Publications
2023
Direction selectivity of inhibitory interneurons in mouse barrel cortex differs between interneuron subtypes.
Julien Guy, Martin Möck, Jochen F. Staiger.
Cell Reports 42, 111936; https://doi.org/10.1016/j.celrep.2022.111936, 2023.
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GABAergic interneurons represent ∼15% to 20% of all cortical neurons, but their diversity grants them unique roles in cortical circuits. In the barrel cortex, responses of excitatory neurons to stimulation of facial whiskers are direction selective, whereby excitation is maximized over a narrow range of angular deflections. Whether GABAergic interneurons are also direction selective is unclear. Here, we use two-photon-guided whole-cell recordings in the barrel cortex of anesthetized mice and control whisker stimulation to measure direction selectivity in defined interneuron subtypes. Selectivity is ubiquitous in interneurons, but tuning sharpness varies across populations. Vasoactive intestinal polypeptide (VIP) interneurons are as selective as pyramidal neurons, but parvalbumin (PV) interneurons are more broadly tuned. Furthermore, a majority (2/3) of somatostatin (SST) interneurons receive direction-selective inhibition, with the rest receiving direction-selective excitation. Sensory evoked activity in the barrel cortex is thus cell-type specific, suggesting that interneuron subtypes make distinct contributions to cortical representations of stimuli.
2022
Repetitively burst-spiking neurons in reeler mice show conserved but also highly variable morphological features of layer Vb-fated “thick-tufted” pyramidal cells..
Jochen F. Staiger*, Alexandra Sachkova, Martin Möck, Julien Guy and Mirko Witte.
Front. Neuroanat. 16:1000107. doi: 10.3389/fnana.2022.1000107, 2022.
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Reelin is a large extracellular glycoprotein that is secreted by Cajal-Retziuscells during embryonic development to regulate neuronal migration andcell proliferation but it also seems to regulate ion channel distributionand synaptic vesicle release properties of excitatory neurons well intoadulthood. Mousemutants with a compromised reelin signaling cascade showa highly disorganized neocortex but the basic connectional features of thedisplaced excitatory principal cells seem to be relatively intact. Very little isknown, however, about the intrinsic electrophysiological and morphologicalproperties of individual cells in the reeler cortex. Repetitive burst-spiking (RB)is a unique property of large, thick-tufted pyramidal cells of wild-type layer Vbexclusively, which project to several subcortical targets. In addition, they areknown to possess sparse but far-reaching intracortical recurrent collaterals.Here, we compared the electrophysiological properties and morphologicalfeatures of neurons in the reeler primary somatosensory cortex with thoseof wild-type controls. Whereas in wild-type mice, RB pyramidal cells wereonly detected in layer Vb, and the vast majority of reeler RB pyramidal cellswere found in the superficial third of the cortical depth. There were noobvious dierences in the intrinsic electrophysiological properties and basicmorphological features (such as soma size or the number of dendrites) werealso well preserved. However, the spatial orientation of the entire dendritictree was highly variable in the reeler neocortex, whereas it was completelystereotyped in wild-typemice. It seems that basic quantitative features of layerVb-fated RB pyramidal cells are well conserved in the highly disorganizedmutant neocortex, whereas qualitative morphological features vary, possiblyto properly orient toward the appropriate input pathways, which are knownto show an atypical oblique path through the reeler cortex. The obliquedendritic orientation thus presumably reflects a re-orientation of dendriticinput domains toward spatially highly disorganized aerent projections.
BAF (mSWI/SNF) complex regulates mediolateral cortical patterning in the developing forebrain.
Huong Nguyen, Godwin Sokpor, Arpan Parichha, Linh Pham, Nidhi Saikhedkar, Yuanbin Xie, Pauline Antonie Ulmke, Joachim Rosenbusch, Mehdi Pirouz, Rüdiger Behr, Anastassia Stoykova, Beate Brand-Saberi, Huu Phuc Nguyen, Jochen F. Staiger, Shubha Tole and Tran Tuoc.
Front. Cell Dev. Biol. 10:1011109. doi: 10.3389/fcell.2022.1011109, 2022.
abstract
Early forebrain patterning entails the correct regional designation of theneuroepithelium, and appropriate specification, generation, and distributionof neural cells during brain development. Specific signaling and transcriptionfactors are known to tightly regulate patterning of the dorsal telencephalon toafford proper structural/functional cortical arealization and morphogenesis.Nevertheless, whether and how changes of the chromatin structure link to thetranscriptional program(s) that control cortical patterning remains elusive. Here,we report that the BAF chromatin remodeling complex regulates thespatiotemporal patterning of the mouse dorsal telencephalon. To determinewhether and how the BAF complex regulates cortical patterning, weconditionally deleted the BAF complex scaffolding subunits BAF155 andBAF170 in the mouse dorsal telencephalic neuroepithelium. Morphologicaland cellular changes in the BAF mutant forebrain were examined usingimmunohistochemistry and in situ hybridization. RNA sequencing, Coimmunoprecipitation,and mass spectrometry were used to investigate themolecular basis of BAF complex involvement in forebrain patterning. We foundthat conditional ablation of BAF complex in the dorsal telencephalonneuroepithelium caused expansion of the cortical hem and medial cortexbeyond their developmental boundaries. Consequently, the hippocampalprimordium is not specified, the mediolateral cortical patterning iscompromised, and the cortical identity is disturbed in the absence of BAFcomplex. The BAF complex was found to interact with the cortical hemsuppressor LHX2. The BAF complex suppresses cortical hem fate to permitproper forebrain patterning. We provide evidence that BAF complex modulatesmediolateral cortical patterning possibly by interacting with the transcriptionfactor LHX2 to drive the LHX2-dependent transcriptional program essential fordorsal telencephalon patterning. Our data suggest a putative mechanisticsynergy between BAF chromatin remodeling complex and LHX2 inregulating forebrain patterning and ontogeny.
2021
Theta activity paradoxically boosts gamma and ripple frequency sensitivity in prefrontal interneurons.
Ricardo Martins Merino, Leon-Pinzon, Walter Stühmer, Martin Möck, Jochen F. Staiger, Fred Wolf, Andreas Neef.
Proceedings of the National Academy of Science USA 2021 118 (51) e2114549118, 2021.
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Fast oscillations in cortical circuits critically depend on GABAergic interneurons. Which interneuron types and populations can drive different cortical rhythms, however, remains unresolved and may depend on brain state. Here, we measured the sensitivity of different GABAergic interneurons in prefrontal cortex under conditions mimicking distinct brain states. While fast-spiking neurons always exhibited a wide bandwidth of around 400 Hz, the response properties of spike-frequency adapting interneurons switched with the background input’s statistics. Slowly fluctuating background activity, as typical for sleep or quiet wakefulness, dramatically boosted the neurons’ sensitivity to gamma and ripple frequencies. We developed a time-resolved dynamic gain analysis and revealed rapid sensitivity modulations that enable neurons to periodically boost gamma oscillations and ripples during specific phases of ongoing low-frequency oscillations. This mechanism predicts these prefrontal interneurons to be exquisitely sensitive to high-frequency ripples, especially during brain states characterized by slow rhythms, and to contribute substantially to theta-gamma cross-frequency coupling.
Lactate is an energy substrate for rodent cortical neurons and enhances their firing activity.
Anastassios Karagiannis, Thierry Gallopin, Alexandre Lacroix, Fabrice Plaisier, Juliette Piquet, Hélène Geoffroy, Régine Hepp, Jérémie Naudé, Benjamin Le Gac, Richard Egger, Bertrand Lambolez, Dongdong Li, Jean Rossier, Jochen F Staiger, Hiromi Imamura, Susumu Seino, Jochen Roeper, Bruno Cauli.
eLife 2021;10:e71424, 2021.
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Glucose is the mandatory fuel for the brain, yet the relative contribution of glucose and lactate for neuronal energy metabolism is unclear. We found that increased lactate, but not glucose concentration, enhances the spiking activity of neurons of the cerebral cortex. Enhanced spiking was dependent on ATP-sensitive potassium (KATP) channels formed with KCNJ11 and ABCC8 subunits,which we show are functionally expressed in most neocortical neuronal types. We also demonstratethe ability of cortical neurons to take-upand metabolize lactate. We further reveal that ATP isproduced by cortical neurons largely via oxidative phosphorylation and only modestly by glycolysis.Our data demonstrate that in active neurons, lactate is preferred to glucose as an energy substrate,and that lactate metabolism shapes neuronal activity in the neocortex through KATP channels. Our results highlight the importance of metabolic crosstalk between neurons and astrocytes for brain function.
H3 acetylation selectively promotes basal progenitor proliferation and neocortex expansion.
Cemil Kerimoglu, Linh Pham, Anton B. Tonchev, M. Sadman Sakib, Yuanbin Xie, Godwin Sokpor, Pauline Antonie Ulmke, Lalit Kaurani, Eman Abbas, Huong Nguyen, Joachim Rosenbusch, Alexandra Michurina, Vincenzo Capece, Meglena Angelova, Nenad Maricic, Beate Brand-Saberi, Miriam Esgleas, Mareike Albert, Radoslav Minkov, Emil Kovachev, Ulrike Teichmann, Rho H. Seong, Wieland B. Huttner, Huu Phuc Nguyen, Anastassia Stoykova, Jochen F. Staiger, Andre Fischer, Tran Tuoc.
Science Advances 2021; 7 : eabc6792, 2021.
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Increase in the size of human neocortex―acquired in evolution―accounts for the unique cognitive capacity ofhumans. This expansion reflects the evolutionarily enhanced proliferative ability of basal progenitors (BPs), includingthe basal radial glia and basal intermediate progenitors (bIPs) in mammalian cortex, which may have been acquiredthrough epigenetic alterations in BPs. However, how the epigenome in BPs differs across species is not known.Here, we report that histone H3 acetylation is a key epigenetic regulation in bIP amplification and cortical expansion.Through epigenetic profiling of sorted bIPs, we show that histone H3 lysine 9 acetylation (H3K9ac) is low inmurine bIPs and high in human bIPs. Elevated H3K9ac preferentially increases bIP proliferation, increasing the sizeand folding of the normally smooth mouse neocortex. H3K9ac drives bIP amplification by increasing expressionof the evolutionarily regulated gene, Trnp1, in developing cortex. Our findings demonstrate a previously unknownmechanism that controls cortical architecture.
Conditional Loss of BAF (mSWI/SNF) Scaffolding Subunits Affects Specification and Proliferation of Oligodendrocyte Precursors in Developing Mouse Forebrain.
Eman Abbas, Mohamed A Hassan, Godwin Sokpor, Kamila Kiszka, Linh Pham, Cemil Kerimoglu, Andre Fischer, Huu Phuc Nguyen, Jochen F Staiger, Tran Tuoc.
Front Cell Dev Biol. 2021 Jul 15;9:619538., 2021.
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Loss of BAF Complex in Developing Cortex Perturbs Radial Neuronal Migration in a WNT Signaling-Dependent Manner.
Godwin Sokpor, Cemil Kerimoglu, Huong Nguyen, Linh Pham, Joachim Rosenbusch, Robin Wagener, Huu Phuc Nguy, Andre Fischer, Jochen F. Staiger and Tran Tuoc.
Front. Mol. Neurosci., 16 June 2021 | https://doi.org/10.3389/fnmol.2021.687581, 2021.
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Radial neuronal migration is a key neurodevelopmental event indispensable for proper cortical laminar organization. Cortical neurons mainly use glial fiber guides, cell adhesion dynamics, and cytoskeletal remodeling, among other discrete processes, to radially trek from their birthplace to final layer positions. Dysregulated radial migration can engender cortical mis-lamination, leading to neurodevelopmental disorders. Epigenetic factors, including chromatin remodelers have emerged as formidable regulators of corticogenesis. Notably, the chromatin remodeler BAF complex has been shown to regulate several aspects of cortical histogenesis. Nonetheless, our understanding of how BAF complex regulates neuronal migration is limited. Here, we report that BAF complex is required for neuron migration during cortical development. Ablation of BAF complex in the developing mouse cortex caused alteration in the cortical gene expression program, leading to loss of radial migration-related factors critical for proper cortical layer formation. Of note, BAF complex inactivation in cortex caused defective neuronal polarization resulting in diminished multipolar-to-bipolar transition and eventual disruption of radial migration of cortical neurons. The abnormal radial migration and cortical mis-lamination can be partly rescued by downregulating WNT signaling hyperactivity in the BAF complex mutant cortex. By implication, the BAF complex modulates WNT signaling to establish the gene expression program required for glial fiber-dependent neuronal migration, and cortical lamination. Overall, BAF complex has been identified to be crucial for cortical morphogenesis through instructing multiple aspects of radial neuronal migration in a WNT signaling-dependent manner.
Mapping of domain-mediated protein-protein interaction by SPOT peptide assay.
Xiaoyi Mao, Godwin Sokpor, Jochen F Staiger, Huu Phuc Nguyen, Tran Tuoc.
STAR Protocols, Volume 2, Issue 2, 100503, 2021.
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Ablation of Vti1a/1b Triggers Neural Progenitor Pool Depletion and Cortical Layer 5 Malformation in Late-embryonic Mouse Cortex.
Godwin Sokpor, Joachim Rosenbusch, Ajaya J Kunwar, Michael Rickmann, Tran Tuoc, Silvio O Rizzoli, Victor Tarabykin, Gabriele Fischer von Mollard, Kerstin Krieglstein, Jochen F Staiger.
Neuroscience . 2021 May 21;463:303-316. doi: 10.1016/j.neuroscience.2021.03.021. Epub 2021 Mar 26, 2021.
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Cortical morphogenesis entails several neurobiological events, including proliferation and differentiation of progenitors, migration of neuroblasts, and neuronal maturation leading to functional neural circuitry. These neurodevelopmental processes are delicately regulated by many factors. Endosomal SNAREs have emerged as formidable modulators of neuronal growth, aside their well-known function in membrane/vesicular trafficking. However, our understanding of their influence on cortex formation is limited. Here, we report that the SNAREs Vti1a and Vti1b (Vti1a/1b) are critical for proper cortical development. Following null mutation of Vti1a/1b in mouse, the late-embryonic mutant cortex appeared dysgenic, and the cortical progenitors therein were depleted beyond normal. Notably, cortical layer 5 (L5) is distinctively disorganized in the absence of Vti1a/1b. The latter defect, coupled with an overt apoptosis of Ctip2-expressing L5 neurons, likely contributed to the substantial loss of corticospinal and callosal projections in the Vti1a/1b-deficient mouse brain. These findings suggest that Vti1a/1b serve key neurodevelopmental functions during cortical histogenesis, which when mechanistically elucidated, can lend clarity to how endosomal SNAREs regulate brain development, or how their dysfunction may have implications for neurological disorders.
Molecular Profiling Reveals Involvement of ESCO2 in Intermediate Progenitor Cell Maintenance in the Developing Mouse Cortex.
Pauline Antonie Ulmke, M Sadman Sakib, Peter Ditte, Godwin Sokpor, Cemil Kerimoglu, Linh Pham, Yuanbin Xie, Xiaoyi Mao, Joachim Rosenbusch, Ulrike Teichmann, Huu Phuc Nguyen, Andre Fischer, Gregor Eichele, Jochen F Staiger, Tran Tuoc.
Stem Cell Reports 2021 Apr 13;16(4):968-984, 2021.
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Critical role of the BAF chromatin remodeling complex during murine neural crest development.
Bi-Lin KW, Seshachalam PV, Tuoc T, Stoykova A, Ghosh S and Singh MK.
PLoS Genetics 17(3): e1009446, 2021.
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The BAF complex plays an important role in the development of a wide range of tissues bymodulating gene expression programs at the chromatin level. However, its role in neuralcrest development has remained unclear. To determine the role of the BAF complex, wedeleted BAF155/BAF170, the core subunits required for the assembly, stability, and functionsof the BAF complex in neural crest cells (NCCs). Neural crest-specific deletion ofBAF155/BAF170 leads to embryonic lethality due to a wide range of developmental defectsincluding craniofacial, pharyngeal arch artery, and OFT defects. RNAseq and transcriptionfactor enrichment analysis revealed that the BAF complex modulates the expression of multiplesignaling pathway genes including Hippo and Notch, essential for the migration, proliferation,and differentiation of the NCCs. Furthermore, we demonstrated that the BAFcomplex is essential for the Brg1-Yap-Tead-dependent transcription of target genes inNCCs. Together, our results demonstrate an important role of the BAF complex in modulatingthe gene regulatory network essential for neural crest development.
Post-transcriptional regulation by the exosome complex is required for cell survival and forebrain development via repression of P53 signaling.
Pauline Antonie Ulmke, Yuanbin Xie, Godwin Sokpor, Linh Pham, Orr Shomroni, Tea Berulava, Joachim Rosenbusch, Uttiya Basu, Andre Fischer, Huu Phuc Nguyen, Jochen F. Staiger, Tran Tuoc.
Development 2021 148: dev188276 doi: 10.1242/dev.188276, 2021.
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Fine-tuned gene expression is crucial for neurodevelopment. The gene expression program is tightly controlled at different levels, including RNA decay. N6-methyladenosine (m6A) methylation-mediated degradation of RNA is essential for brain development. However, m6A methylation impacts not only RNA stability, but also other RNA metabolism processes. How RNA decay contributes to brain development is largely unknown. Here, we show that Exosc10, a RNA exonuclease subunit of the RNA exosome complex, is indispensable for forebrain development. We report that cortical cells undergo overt apoptosis, culminating in cortical agenesis upon conditional deletion of Exosc10 in mouse cortex. Mechanistically, Exosc10 directly binds and degrades transcripts of the P53 signaling-related genes, such as Aen and Bbc3. Overall, our findings suggest a crucial role for Exosc10 in suppressing the P53 pathway, in which the rapid turnover of the apoptosis effectors Aen and Bbc3 mRNAs is essential for cell survival and normal cortical histogenesis.
Spine dynamics of PSD-95-deficient neurons in the visual cortex link silent synapses to structural cortical plasticity.
Rashad Yusifov, Anja Tippmann, Jochen F. Staiger, Oliver M. Schlüter and Siegrid Löwel.
Proceedings of the National Academy of Science USA, 2021 118 (10) e2022701118, 2021.
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Critical periods (CPs) are timewindows of heightened brain plasticityduring which experience refines synaptic connections to achievemature functionality. At glutamatergic synapses on dendritic spinesof principal cortical neurons, the maturation is largely governed bypostsynaptic density protein-95 (PSD-95)-dependent synaptic incorporationof α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid(AMPA) receptors into nascent AMPA-receptor silent synapses. Consequently,in mouse primary visual cortex (V1), impaired silent synapsematuration in PSD-95-deficient neurons prevents the closure ofthe CP for juvenile ocular dominance plasticity (jODP). A structuralhallmark of jODP is increased spine elimination, induced by briefmonocular deprivation (MD). However, it is unknown whether impairedsilent synapse maturation facilitates spine elimination andalso preserves juvenile structural plasticity. Using two-photon microscopy,we assessed spine dynamics in apical dendrites of layer2/3 pyramidal neurons (PNs) in binocular V1 during ODP in awakeadult mice. Under basal conditions, spine formation and eliminationratios were similar between PSD-95 knockout (KO) and wild-type(WT) mice. However, a brief MD affected spine dynamics only inKO mice, where MD doubled spine elimination, primarily affectingnewly formed spines, and caused a net reduction in spine densitysimilar to what has been observed during jODP inWT mice. A similarincrease in spine elimination after MD occurred if PSD-95 wasknocked down in single PNs of layer 2/3. Thus, structural plasticityis dictated cell autonomously by PSD-95 in vivo in awake mice. Lossof PSD-95 preserves hallmark features of spine dynamics in jODP intoadulthood, revealing a functional link of PSD-95 for experiencedependentsynapse maturation and stabilization during CPs.
Sensory input drives rapid homeostatic scaling of the axon initial segment in mouse barrel cortex.
Nora Jamann, Dominik Dannehl, Nadja Lehmann, Robin Wagener, Corinna Thielemann, Christian Schultz, Jochen F. Staiger, Maarten H. P. Kole & Maren Engelhardt.
Nature Communications 12:23; https://doi.org/10.1038/s41467-020-20232-x, 2021.
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The axon initial segment (AIS) is a critical microdomain for action potential initiation and implicated in the regulation of neuronal excitability during activity-dependent plasticity. While structural AIS plasticity has been suggested to fine-tune neuronal activity when networkstates change, whether it acts in vivo as a homeostatic regulatory mechanism in behaviorally relevant contexts remains poorly understood. Using the mouse whisker-to-barrel pathway asa model system in combination with immunofluorescence, confocal analysis and electrophysiological recordings, we observed bidirectional AIS plasticity in cortical pyramidal neurons. Furthermore, we find that structural and functional AIS remodeling occurs in distinct temporal domains: Long-term sensory deprivation elicits an AIS length increase, accompanied with an increase in neuronal excitability, while sensory enrichment results in a rapidAIS shortening, accompanied by a decrease in action potential generation. Our findings highlight a central role of the AIS in the homeostatic regulation of neuronal input-output relations.
Neuronal Circuits in Barrel Cortex for Whisker Sensory Perception.
Staiger JF and Petersen CCH.
Physiological Reviews 101:353-415, 2021.
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The array of whiskers on the snout provides rodents with tactile sensory information relating to the size, shape and texture of objects in their immediate environment. Rodents can use their whiskers to detect stimuli, distinguish textures, locate objects and navigate. Important aspects of whisker sensation are thought to result from neuronal computations in the whisker somatosensory cortex (wS1). Each whisker is individually represented in the somatotopic map of wS1 by an anatomical unit named a ‘barrel’ (hence also called barrel cortex). This allows precise investigation of sensory processing in the context of a well-defined map. Here, we first review the signaling pathways from the whiskers to wS1, and then discuss current understanding of the various types of excitatory and inhibitory neurons present within wS1. Different classes of cells can be defined according to anatomical, electrophysiological and molecular features. The synaptic connectivity of neurons within local wS1 microcircuits, as well as their long-range interactions and the impact of neuromodulators, are beginning to be understood. Recent technological progress has allowed cell-type-specific connectivity to be related to cell-type-specific activity during whisker-related behaviors. An important goal for future research is to obtain a causal and mechanistic understanding of how selected aspects of tactile sensory information are processed by specific types of neurons in the synaptically connected neuronal networks of wS1 and signaled to downstream brain areas, thus contributing to sensory-guided decision-making.
2020
NKCC-1 mediated Cl− uptake in immature CA3 pyramidal neurons is sufficient to compensate phasic GABAergic inputs.
Sergey N. Kolbaev, Namrata Mohapatra, Rongqing Chen, Aniello Lombardi, Jochen F. Staiger, Heiko J. Luhmann, Peter Jedlicka & Werner Kilb.
Scientific Reports volume 10, Article number: 18399, 2020.
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Activation of GABAA receptors causes in immature neurons a functionally relevant decrease in the intracellular Cl− concentration ([Cl−]i), a process termed ionic plasticity. Amount and duration of ionic plasticity depends on kinetic properties of [Cl−]i homeostasis. In order to characterize the capacity of Cl− accumulation and to quantify the effect of persistent GABAergic activity on [Cl−]i, we performed gramicidin-perforated patch-clamp recordings from CA3 pyramidal neurons of immature (postnatal day 4–7) rat hippocampal slices. These experiments revealed that inhibition of NKCC1 decreased [Cl−]i toward passive distribution with a time constant of 381 s. In contrast, active Cl− accumulation occurred with a time constant of 155 s, corresponding to a rate of 15.4 µM/s. Inhibition of phasic GABAergic activity had no significant effect on steady state [Cl−]i. Inhibition of tonic GABAergic currents induced a significant [Cl−]i increase by 1.6 mM, while activation of tonic extrasynaptic GABAA receptors with THIP significantly reduced [Cl−]i.. Simulations of neuronal [Cl−]i homeostasis supported the observation, that basal levels of synaptic GABAergic activation do not affect [Cl−]i. In summary, these results indicate that active Cl−-uptake in immature hippocampal neurons is sufficient to maintain stable [Cl−]i at basal levels of phasic and to some extent also to compensate tonic GABAergic activity.
Increased Callosal Connectivity in Reeler Mice Revealed by Brain-Wide Input Mapping of VIP Neurons in Barrel Cortex.
Georg Hafner, Julien Guy, Mirko Witte, Pavel Truschow, Alina Rüppel, Nikoloz Sirmpilatze, Rakshit Dadarwal, Susann Boretius, Jochen F Staiger.
Cerebral Cortex, bhaa280, https://doi.org/10.1093/cercor/bhaa280, 2020.
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The neocortex is composed of layers. Whether layers constitute an essential framework for the formation of functional circuits is not well understood. We investigated the brain-wide input connectivity of vasoactive intestinal polypeptide (VIP) expressing neurons in the reeler mouse. This mutant is characterized by a migration deficit of cortical neurons so that no layers are formed. Still, neurons retain their properties and reeler mice show little cognitive impairment. We focused on VIP neurons because they are known to receive strong long-range inputs and have a typical laminar bias toward upper layers. In reeler, these neurons are more dispersed across the cortex. We mapped the brain-wide inputs of VIP neurons in barrel cortex of wild-type and reeler mice with rabies virus tracing. Innervation by subcortical inputs was not altered in reeler, in contrast to the cortical circuitry. Numbers of long-range ipsilateral cortical inputs were reduced in reeler, while contralateral inputs were strongly increased. Reeler mice had more callosal projection neurons. Hence, the corpus callosum was larger in reeler as shown by structural imaging. We argue that, in the absence of cortical layers, circuits with subcortical structures are maintained but cortical neurons establish a different network that largely preserves cognitive functions.
A community-based transcriptomics classification and nomenclature of neocortical cell types.
Rafael Yuste, Michael Hawrylycz, Nadia Aalling, Argel Aguilar-Valles, Detlev Arendt, Ruben Armananzas Arnedillo, Giorgio A. Ascoli, Concha Bielza, Vahid Bokharaie, Tobias Borgtoft Bergmann, Irina Bystron, Marco Capogna, Yoonjeung Chang, Ann Clemens, Christiaan P. J. de Kock, Javier DeFelipe, Sandra Esmeralda Dos Santos, Keagan Dunville, Dirk Feldmeyer, Richárd Fiáth, Gordon James Fishell, Angelica Foggetti, Xuefan Gao, Parviz Ghaderi, Natalia A. Goriounova, Onur Güntürkün, Kenta Hagihara, Vanessa Jane Hall, Moritz Helmstaedter, Suzana Herculano, Markus M. Hilscher, Hajime Hirase, Jens Hjerling-Leffler, Rebecca Hodge, Josh Huang, Rafiq Huda, Konstantin Khodosevich, Ole Kiehn, Henner Koch, Eric S. Kuebler, Malte Kühnemund, Pedro Larrañaga, Boudewijn Lelieveldt, Emma Louise Louth, Jan H. Lui, Huibert D. Mansvelder, Oscar Marin, Julio Martinez-Trujillo, Homeira Moradi Chameh, Alok Nath, Maiken Nedergaard, Pavel Němec, Netanel Ofer, Ulrich Gottfried Pfisterer, Samuel Pontes, William Redmond, Jean Rossier, Joshua R. Sanes, Richard Scheuermann, Esther Serrano-Saiz, Staiger JF, Peter Somogyi, Gábor Tamás, Andreas Savas Tolias, Maria Antonietta Tosches, Miguel Turrero García, Hermany Munguba Vieira, Christian Wozny, Thomas V. Wuttke, Liu Yong, Juan Yuan, Hongkui Zeng & Ed Lein.
Nature Neuroscience 23: 1456–1468, 2020.
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To understand the function of cortical circuits, it is necessary to catalog their cellular diversity. Past attempts to do so using anatomical, physiological or molecular features of cortical cells have not resulted in a unified taxonomy of neuronal or glial cell types, partly due to limited data. Single-cell transcriptomics is enabling, for the first time, systematic high-throughput measurements of cortical cells and generation of datasets that hold the promise of being complete, accurate and permanent. Statistical analyses of these data reveal clusters that often correspond to cell types previously defined by morphological or physiological criteria and that appear conserved across cortical areas and species. To capitalize on these new methods, we propose the adoption of a transcriptome-based taxonomy of cell types for mammalian neocortex. This classification should be hierarchical and use a standardized nomenclature. It should be based on a probabilistic definition of a cell type and incorporate data from different approaches, developmental stages and species. A community-based classification and data aggregation model, such as a knowledge graph, could provide a common foundation for the study of cortical circuits. This community-based classification, nomenclature and data aggregation could serve as an example for cell type atlases in other parts of the body.
Histological assessment of optogenetic tools to study fronto-visual and fronto-parietal cortical networks in the rhesus macaque.
Fortuna, M. G. Huer, J. Guo, H. Gruber, J. Gruber-Dujardin, E. Staiger, J. F. Scherberger, H. Treue, S. Gail, A..
Scientific Reports: 10(1)2020: DOI 10.1038/s41598-020-67752-6, 2020.
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Optogenetics ofers unprecedented possibilities to investigate cortical networks. Yet, the number of successful optogenetic applications in non-human primates is still low, and the consequences of opsin expression in the primate brain are not well documented. We assessed histologically if we can target cerebrocortical networks with three common optogenetic constructs (AAV2/5-CaMKIIα-eNpHR3.0mCherry, -ChR2-eYFP, -C1V1-mCherry). The frontal eye feld or the dorsal premotor area of rhesus macaques were virally injected, and the resulting transduction spread, expression specifcity, and opsin trafcking into axons projecting to parietal and visual areas were examined. After variable periods (2–24 months), expression was robust for all constructs at the injection sites. The CaMKIIα promoter driven-expression was predominant, but not exclusive, in excitatory neurons. In the case of eNpHR3.0-mCherry and ChR2-eYFP, opsins were present in axonal projections to target areas, in which sparse, retrogradely transduced neurons could also be found. Finally, the intracellular distribution of opsins difered: ChR2-eYFP had almost exclusive membrane localization, while eNpHR3.0-mCherry and C1V1-mCherry showed additional intracellular accumulations, which might afect neuronal survival in the long-term. Results indicate that all three constructs can be used for local neuronal modulation, but axonal stimulation and long-term use require additional considerations of construct selection and verifcation.
Recommendations for measuring whisker movements and locomotion in mice with sensory, motor and cognitive deficits.
Simanaviciute U, Ahmed J, Brown RE, Connor-Robson N, Farr TD, Fertan E, Gambles N, Garland H, Morton AJ, Staiger JF, Skillings EA, Trueman RC, Wade-Martins R, Wood NI, Wong AA, Grant RA.
J Neurosci Methods. 2020 Feb 1;331:108532. doi: 10.1016/j.jneumeth.2019.108532., 2020.
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2019
Selective Inactivation of Reelin in Inhibitory Interneurons Leads to Subtle Changes in the Dentate Gyrus But Leaves Cortical Layering and Behavior Unaffected.
Pahle J, Muhia M, Wagener RJ, Tippmann A, Bock HH, Graw J, Herz J, Staiger JF, Drakew A, Kneussel M, Rune GM, Frotscher M, Brunne B.
Cereb Cortex. 2019 Oct 30. pii: bhz196. doi: 10.1093/cercor/bhz196, 2019.
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Reelin is an extracellular matrix protein, known for its dual role in neuronal migration during brain development and in synaptic plasticity at adult stages. During the perinatal phase, Reelin expression switches from Cajal-Retzius (CR) cells, its main source before birth, to inhibitory interneurons (IN), the main source of Reelin in the adult forebrain. IN-derived Reelin has been associated with schizophrenia and temporal lobe epilepsy; however, the functional role of Reelin from INs is presently unclear. In this study, we used conditional knockout mice, which lack Reelin expression specifically in inhibitory INs, leading to a substantial reduction in total Reelin expression in the neocortex and dentate gyrus. Our results show that IN-specific Reelin knockout mice exhibit normal neuronal layering and normal behavior, including spatial reference memory. Although INs are the major source of Reelin within the adult stem cell niche, Reelin from INs does not contribute substantially to normal adult neurogenesis. While a closer look at the dentate gyrus revealed some unexpected alterations at the cellular level, including an increase in the number of Reelin expressing CR cells, overall our data suggest that Reelin derived from INs is less critical for cortex development and function than Reelin expressed by CR cells.
Pathway-, layer- and cell-type-specific thalamic input to mouse barrel cortex.
Sermet BS, Truschow P, Feyerabend M, Mayrhofer JM, Oram TB, Yizhar O, Staiger JF, Petersen CCH.
eLife 2019;8:e52665 , 2019.
abstract link
Mouse primary somatosensory barrel cortex (wS1) processes whisker sensory information, receiving input from two distinct thalamic nuclei. The first-order ventral posterior medial (VPM) somatosensory thalamic nucleus most densely innervates layer 4 (L4) barrels, whereas the higher-order posterior thalamic nucleus (medial part, POm) most densely innervates L1 and L5A. We optogenetically stimulated VPM or POm axons, and recorded evoked excitatory postsynaptic potentials (EPSPs) in different cell-types across cortical layers in wS1. We found that excitatory neurons and parvalbumin-expressing inhibitory neurons received the largest EPSPs, dominated by VPM input to L4 and POm input to L5A. In contrast, somatostatin-expressing inhibitory neurons received very little input from either pathway in any layer. Vasoactive intestinal peptide-expressing inhibitory neurons received an intermediate level of excitatory input with less apparent layer-specificity. Our data help understand how wS1 neocortical microcircuits might process and integrate sensory and higher-order inputs.
Mapping Brain-Wide Afferent Inputs of Parvalbumin-Expressing GABAergic Neurons in Barrel Cortex Reveals Local and Long-Range Circuit Motifs.
Hafner G, Witte M, Guy J, Subhashini N, Fenno LE, Ramakrishna C, Kim YS, Deisseroth K, Callaway EC, Oberhuber M, Conzelmann KK, Staiger JF.
Cell Reports 28 (13) P3450-3461.E8, 2019.
abstract link
Parvalbumin (PV)-expressing GABAergic neurons are the largest class of inhibitory neocortical cells. We visualize brain-wide, monosynaptic inputs to PV neurons in mouse barrel cortex. We develop intersectional rabies virus tracing to specifically target GABAergic PV cells and exclude a small fraction of excitatory PV cells from our starter population. Local inputs are mainly from layer (L) IV and excitatory cells. A small number of inhibitory inputs originate from LI neurons, which connect to LII/III PV neurons. Long-range inputs originate mainly from other sensory cortices and the thalamus. In visual cortex, most transsynaptically labeled neurons are located in LIV, which contains a molecularly mixed population of projection neurons with putative functional similarity to LIII neurons. This study expands our knowledge of the brain-wide circuits in which PV neurons are embedded and introduces intersectional rabies virus tracing as an applicable tool to dissect the circuitry of more clearly defined cell types.
Functional architecture and encoding of tactile sensorimotor behavior in rat posterior parietal cortex.
Mohan H, de Haan R, Broersen R, Pieneman AW, Helmchen F, Staiger JF, Mansvelder HD, de Kock CPJ.
Journal of Neuroscience 39:7332-7343, 2019.
abstract link
The posterior parietal cortex (PPC) in rodents is reciprocally connected to primary somatosensory and vibrissal motor cortices. The PPCneuronal circuitry could thus encode and potentially integrate incoming somatosensory information and whisker motor output. However,the information encoded across PPC layers during refined sensorimotor behavior remains largely unknown. To uncover thesensorimotor features represented in PPC during voluntary whisking and object touch, we performed loose-patch single-unit recordingsand extracellular recordings of ensemble activity, covering all layers of PPC in anesthetized and awake, behaving male rats. First, usingsingle-cell receptive field mapping, we revealed the presence of coarse somatotopy along the mediolateral axis in PPC. Second, we foundthat spiking activity was modulated during exploratory whisking in layers 2– 4 and layer 6, but not in layer 5 of awake, behaving rats.Population spiking activity preceded actual movement, and whisker trajectory endpoints could be decoded by population spiking,suggesting that PPC is involved in movement planning. Finally, population spiking activity further increased in response to activewhisker touch but only in PPC layers 2– 4. Thus, we find layer-specific processing, which emphasizes the computational role of PPCduring whisker sensorimotor behavior.
Characterizing the morphology of somatostatin‐expressing interneurons and their synaptic innervation pattern in the barrel cortex of the GFP‐expressing inhibitory neurons mouse.
Zhou X., Mansori I., Fischer T., Witte M., Staiger JF..
J Comp Neurol. 2019;1–17, 2019.
abstract link
Somatostatin‐expressing (SST+) cells form the second largest subpopulation of neocortical GABAergic neurons that contain diverse subtypes, which participate in layer‐specific cortical circuits. Martinotti cells, as the most abundant subtype of SST+ interneurons, are mainly located in layers II/III and V/VI, and are characterized by dense axonal arborizations in layer I. GFP‐expressing inhibitory neurons (GIN), representing a fraction of mainly upper layer SST+ interneurons in various cortical areas, were recently claimed to include both Martinotti cells and non‐Martinotti cells. This makes it necessary to examine in detail the morphology and synaptic innervation pattern of the GIN cells, in order to better predict their functional implications. In our study, we characterized the neurochemical specificity, somatodendritic morphology, synaptic ultrastructure as well as synaptic innervation pattern of GIN cells in the barrel cortex in a layer‐specific manner. We showed that GIN cells account for 44% of the SST+ interneurons in layer II/III and around 35% in layers IV and Va. There are 29% of GIN cells coexpressing calretinin with 54% in layer II/III, 8% in layer IV, and 13% in layer V. They have diverse somatodendritic configurations and form relatively small synapses across all examined layers. They almost exclusively innervate dendrites of excitatory cells, preferentially targeting distal apical dendrites and apical dendritic tufts of pyramidal neurons in layer I, and rarely target other inhibitory neurons. In summary, our study reveals unique features in terms of the morphology and output of GIN cells, which can help to better understand their diversity and structure–function relationships.
Neuromodulation Leads to a Burst-Tonic Switch in a Subset of VIP Neurons in Mouse Primary Somatosensory (Barrel) Cortex.
Prönneke A, Witte M, Möck M, Staiger JF.
Cerebral Cortex doi: 10.1093/cercor/bhz102, 2019.
abstract link
Neocortical GABAergic interneurons expressing vasoactive intestinal polypeptide (VIP) contribute to sensory processing,sensorimotor integration, and behavioral control. In contrast to other major subpopulations of GABAergic interneurons, VIPneurons show a remarkable diversity. Studying morphological and electrophysiological properties of VIP cells, we found apeculiar group of neurons in layer II/III of mouse primary somatosensory (barrel) cortex, which showed a highly dynamicburst firing behavior at resting membrane potential that switched to tonic mode at depolarized membrane potentials.Furthermore, we demonstrate that burst firing depends on T-type calcium channels. The burst-tonic switch could beinduced by acetylcholine (ACh) and serotonin. ACh mediated a depolarization via nicotinic receptors whereas serotoninevoked a biphasic depolarization via ionotropic and metabotropic receptors in 48% of the population and a purelymonophasic depolarization via metabotropic receptors in the remaining cells. These data disclose an electrophysiologicallydefined subpopulation of VIP neurons that via neuromodulator-induced changes in firing behavior is likely to regulate thestate of cortical circuits in a profound manner.
Distribution Patterns of Three Molecularly Defined Classes of GABAergic Neurons Across Columnar Compartments in Mouse Barrel Cortex.
Almási Z, Dávid C, Witte M, Staiger JF.
Frontiers in Neuroanatomy 13:45 doi: 10.3389/fnana.2019.00045, 2019.
abstract link
The mouse somatosensory cortex is an excellent model to study the structural basis ofcortical information processing, since it possesses anatomically recognizable domainsthat receive different thalamic inputs, which indicates spatial segregation of differentprocessing tasks. In this work we examined three genetically labeled, non-overlappingsubpopulations of GABAergic neurons: parvalbumin- (PVC), somatostatin- (SSTC), andvasoactive intestinal polypeptide-expressing (VIPC) cells. Each of these subpopulationsdisplayed a unique cellular distribution pattern across layers. In terms of columnarlocalization, the distribution of these three populations was not quantitatively differentbetween barrel-related versus septal compartments in most layers. However, in layer IV(LIV), SSTC, and VIPC, but not PVC neurons preferred the septal compartment overbarrels. The examined cell types showed a tendency toward differential distribution insupragranular and infragranular barrel-related versus septal compartments, too. Ourdata suggests that the location of GABAergic neuron cell bodies correlates with thespatial pattern of cortical domains receiving different kinds of thalamic input. Thus,at least in LIV, lemniscal inputs present a close spatial relation preferentially to PVCcells whereas paralemniscal inputs target compartments in which more SSTC andVIPC cells are localized. Our findings suggest pathway-specific roles for neocorticalGABAergic neurons.
RBM15 Modulates the Function of Chromatin Remodeling Factor BAF155 Through RNA Methylation in Developing Cortex.
Xie Y*, Hernandez RC*, Sokpor G, Pham L, Narayanan R, Rosenbusch J, Staiger JF, Tuoc T.
Molecular Neurobiology, https://doi.org/10.1007/s12035-019-1595-1, 2019.
abstract link
Chromatin remodeling factor BAF155 is an important regulator of many biological processes. As a core and scaffold subunit of the BAF (SWI/SNF-like) complex, BAF155 is capable of regulating the stability and function of the BAF complex. The spatiotemporal expression of BAF155 during embryogenesis is essential for various aspects of organogenesis, particularly in the brain development. However, our understanding of the mechanisms that regulate the expression and function of BAF155 is limited. Here, we report that RBM15, a subunit of the m6A methyltransferase complex, interacts with BAF155 mRNA and mediates BAF155 mRNA degradation through the mRNA methylation machinery. Ablation of endogenous RBM15 expression in cultured neuronal cells and in the developing cortex augmented the expression of BAF155. Conversely, RBM15 overexpression decreased BAF155 mRNA and protein levels, and perturbed BAF155 functions in vivo, including repression of BAF155-dependent transcriptional activity and delamination of apical radial glial progenitors as a hallmark of basal radial glial progenitor genesis. Furthermore, we demonstrated that the regulation of BAF155 by RBM15 depends on the activity of the mRNA methylation complex core catalytic subunit METTL3. Altogether, our findings reveal a new regulatory avenue that elucidates how BAF complex subunit stoichiometry and functional modulation are achieved in mammalian cells.
Structural brain anomalies in patients with FOXG1 syndrome and in Foxg1+/− mice.
Pringsheim M,, Mitter D, Schröder S, Warthemann R, Plümacher K, Kluger G, Baethmann M, Bast T, Braun S, Büttel HM, Conover E, Courage C, Datta AN, Eger A, Grebe TA, Hasse‐Wittmer A, Heruth M, Höft K, Kaindl AM, Karch S, Kautzky T, Korenke GC, Kruse B, Lutz RE, Omran H, Patzer S, Philippi H, Ramsey K, Rating T, Rieß A, Schimmel M, Westman R, Zech FM, Zirn B, Ulmke PA, Sokpor G, Tuoc T, Leha A, Staudt M, Brockmann K.
Ann Clin Transl Neurol. https://doi.org/10.1002/acn3.735, 2019.
abstract link
Objective
FOXG1 syndrome is a rare neurodevelopmental disorder associated with heterozygous FOXG1 variants or chromosomal microaberrations in 14q12. The study aimed at assessing the scope of structural cerebral anomalies revealed by neuroimaging to delineate the genotype and neuroimaging phenotype associations.
Methods
We compiled 34 patients with a heterozygous (likely) pathogenic FOXG1 variant. Qualitative assessment of cerebral anomalies was performed by standardized re‐analysis of all 34 MRI data sets. Statistical analysis of genetic, clinical and neuroimaging data were performed. We quantified clinical and neuroimaging phenotypes using severity scores. Telencephalic phenotypes of adult Foxg1+/− mice were examined using immunohistological stainings followed by quantitative evaluation of structural anomalies.
Results
Characteristic neuroimaging features included corpus callosum anomalies (82%), thickening of the fornix (74%), simplified gyral pattern (56%), enlargement of inner CSF spaces (44%), hypoplasia of basal ganglia (38%), and hypoplasia of frontal lobes (29%). We observed a marked, filiform thinning of the rostrum as recurrent highly typical pattern of corpus callosum anomaly in combination with distinct thickening of the fornix as a characteristic feature. Thickening of the fornices was not reported previously in FOXG1 syndrome. Simplified gyral pattern occurred significantly more frequently in patients with early truncating variants. Higher clinical severity scores were significantly associated with higher neuroimaging severity scores. Modeling of Foxg1 heterozygosity in mouse brain recapitulated the associated abnormal cerebral morphology phenotypes, including the striking enlargement of the fornix.
Interpretation
Combination of specific corpus callosum anomalies with simplified gyral pattern and hyperplasia of the fornices is highly characteristic for FOXG1 syndrome.
2018
Chromatin remodeling BAF155 subunit regulates the genesis of basal progenitors in developing cortex .
Narayanan R, Pham L, Kerimoglu C, Watanabe T, Hernandez RC, Sokpor G, Ulmke PA, Kiszka KA, Tonchev AB, Rosenbusch J, Seong RH, Teichmann U, Frahm J, Fischer F, Bonn S, Stoykova A, Staiger JF, Tuoc T.
iScience (Cell Press), DOI: https://doi.org/10.1016/j.isci.2018.05.014, 2018.
abstract link
The abundance of basal progenitors (BPs) - basal radial glia progenitors (bRGs) and basal intermediate progenitors (bIPs), in primate brain has been correlated to the high degree of cortical folding. Here we examined the role of BAF155, a subunit of the chromatin remodeling BAF complex, in generation of cortical progenitor heterogeneity. The conditional deletion of BAF155 led to diminished bIP pool and increased number of bRGs, due to delamination of apical RGs. We found that BAF155 is required for normal activity of neurogenic transcription factor PAX6, thus controlling expression of genes that are involved in bIP specification, cell-cell interaction and establishment of adherens junction. In PAX6-dependent manner, BAF155 regulates the expression of the CDC42 effector protein CEP4, thereby controlling progenitor delamination. Furthermore, BAF155-dependent chromatin remodeling seems to exert a specific role in the genesis of BPs through regulation of human RG-specific genes (such as Foxn4) that possibly acquired evolutionary significance.
Epigenetic regulation by BAF (mSWI/SNF) complexes limits neural stem cell proliferation by suppressing Wnt signaling in late embryonic development.
Nguyen H*, Kerimoglu C*, Pirouz M, Pham L, Kiszka KA, Sokpor G, Sakib MS, Rosenbusch J, Teichmann U, Seong RH, Stoykova A, Fischer A, Staiger JF, Tuoc T .
Stem Cell Reports, doi: 10.1016/j.stemcr.2018.04.014, 2018.
abstract link
During early cortical development, neural stem cells (NSCs) divide symmetrically to expand the progenitor pool, whereas in later stages, NSCs divide asymmetrically to self-renew and produce other cell types. The timely switch from such proliferative to differentiative division critically determines progenitor and neuron numbers. However, the mechanisms that limit proliferative division in late cortical development are not fully understood. Here, we show that the BAF (mSWI/SNF) complexes restrict proliferative competence and promote neuronal differentiation in late corticogenesis. Inactivation of BAF complexes leads to H3K27me3-linked silencing of neuronal differentiation-related genes, with concurrent H3K4me2-mediated activation of proliferation-associated genes via de-repression of Wnt signaling. Notably, the deletion of BAF complexes increased proliferation of neuroepithelial cell-like NSCs, impaired neuronal differentiation and exerted a Wnt-dependent effect on neocortical and hippocampal development. Thus, these results demonstrate that BAF complexes act as both activators and repressors to control global epigenetic and gene expression programs in late corticogenesis.
ATP-dependent chromatin remodeling during cortical neurogenesis.
Sokpor G*, Hernandez RC*, Rosenbusch J, Staiger JF, Tuoc T.
Front. Neurosci. | doi: 10.3389/fnins.2018.00226 , 2018.
abstract link
The generation of individual neurons (neurogenesis) during cortical development occurs in discrete steps that are subtly regulated and orchestrated to ensure normal histogenesis and function of the cortex. Notably, various gene expression programs are known to critically drive many facets of neurogenesis with a high level of specificity during brain development. Typically, precise regulation of gene expression patterns ensures that key events like proliferation and differentiation of neural progenitors, specification of neuronal subtypes, as well as migration and maturation of neurons in the developing cortex occur properly. ATP-dependent chromatin remodeling complexes regulate gene expression through utilization of energy from ATP hydrolysis to reorganize chromatin structure. These chromatin remodeling complexes are characteristically multimeric, with some capable of adopting functionally distinct conformations via subunit reconstitution to perform specific roles in major aspects of cortical neurogenesis. In this review, we highlight the functions of such chromatin remodelers during cortical development. We also bring together various proposed mechanisms by which ATP-dependent chromatin remodelers function individually or in concert, to specifically modulate vital steps in cortical neurogenesis.
Transcriptional and epigenetic control of mammalian olfactory epithelium development.
Sokpor G*, Abbas E*, Rosenbusch J, Staiger JF, Tuoc T..
Molecular Neurobiology (https://doi.org/10.1007/s12035-018-0987-y), 2018.
abstract link
The postnatal mammalian olfactory epithelium (OE) represents a major aspect of the peripheral olfactory system. It is a pseudostratified tissue that originates from the olfactory placode and is composed of diverse cells, some of which are specialized receptor neurons capable of transducing odorant stimuli to afford the perception of smell (olfaction). The OE is known to offer a tractable miniature model for studying the systematic generation of neurons and glia that typify neural tissue development. During OE development, stem/progenitor cells that will become olfactory sensory neurons and/or non-neuronal cell types, display fine spatiotemporal expression of neuronal and non-neuronal genes that ensures their proper proliferation, differentiation, survival, and regeneration. Many factors, including transcription and epigenetic factors have been identified as key regulators of the expression of such requisite genes to permit normal OE morphogenesis. Typically, specific interactive regulatory networks established between transcription and epigenetic factors/cofactors orchestrate histogenesis in the embryonic and adult OE. Hence, investigation of these regulatory networks critical for OE development promises to disclose strategies that may be employed in manipulating the stepwise transition of olfactory precursor cells to become fully differentiated and functional neuronal and non-neuronal cell types. Such strategies potentially offer formidable means of replacing injured or degenerated neural cells as therapeutics for nervous system perturbations. This review recapitulates the developmental cellular diversity of the olfactory neuroepithelium and discusses findings on how the precise and cooperative molecular control by transcriptional and epigenetic machinery is indispensable for OE ontogeny.
2017
Subcellular Targeting of VIP Boutons in Mouse Barrel Cortex is Layer-Dependent and not Restricted to Interneurons.
Zhou,X.; Rickmann,M.; Hafner,G.; Staiger,J.F..
Cerebral Cortex 27(11):5353-5368, 2017.
abstract link
Neocortical vasoactive intestinal polypeptide (VIP) expressing cells are a diverse subpopulation of GABAergic interneurons issuing distinct axonal projections. They are known to inhibit other types of interneurons as well as excitatory principal neurons and possess a disinhibitory net effect in cortical circuits. In order to elucidate their targeting specificity, the output connectivity of VIP interneurons was studied at the subcellular level in barrel cortex of interneuron-specific Cre-driver mice, using pre- and postembedding electron microscopy. Systematically sampling VIP boutons across all layers, we found a substantial proportion of the innervated subcellular structures were dendrites (80%), with somata (13%), and spines (7%) being much less targeted. In layer VI, a high proportion of axosomatic synapses was found (39%). GABA-immunopositive ratio was quantified among the targets using statistically validated thresholds: only 37% of the dendrites, 7% of the spines, and 26% of the somata showed above-threshold immunogold labeling. For the main target structure "dendrite", a higher proportion of GABAergic subcellular profiles existed in deep than in superficial layers. In conclusion, VIP interneurons innervate non-GABAergic excitatory neurons and interneurons at their subcellular domains with layer-dependent specificity. This suggests a diverse output of VIP interneurons, which predicts multiple functionality in cortical circuitry beyond disinhibition
Inhibitory interneurons and their circuit motifs in the many layers of the barrel cortex.
Feldmeyer D, Qi G, Emmenegger V, Staiger JF.
Neuroscience | http://dx.doi.org/10.1016/j.neuroscience.2017.05.027, 2017.
abstract link
Recent years have seen substantial progress instudying the structural and functional properties ofGABAergic interneurons and their roles in the neuronal networksof barrel cortex. Although GABAergic interneuronsrepresent only about 12% of the total number of neocorticalneurons, they are extremely diverse with respect to theirstructural and functional properties. It has become clear thatbarrel cortex interneurons not only serve the maintenanceof an appropriate excitation/inhibition balance but also aredirectly involved in sensory processing. In this review wepresent different interneuron types and their axonal projectionpattern framework in the context of the laminar andcolumnar organization of the barrel cortex. The main focusis here on the most prominent interneuron types, i.e. basketcells, chandelier cells, Martinotti cells, bipolar/bitufted cellsand neurogliaform cells, but interneurons with more unusualaxonal domains will also be mentioned. We describetheir developmental origin, their classification with respectto molecular, morphological and intrinsic membrane andsynaptic properties. Most importantly, we will highlight themost prominent circuit motifs these interneurons areinvolved in and in which way they serve feed-forward inhibition,feedback inhibition and disinhibition. Finally, this willbe put into context to their functional roles in sensory signalperception and processing in the whisker system andbeyond.
Chromatin Remodeling BAF (SWI/SNF) Complexes in Neural Development and Disorders.
Sokpor G*, Xie Y*, Rosenbusch J, Tuoc T.
Front. Mol. Neurosci. | doi: 10.3389/fnmol.2017.00243 , 2017.
abstract link
The ATP-dependent BRG1/BRM associated factor (BAF) chromatin remodeling complexes are crucial in regulating gene expression by controlling chromatin dynamics. Over the last decade, it has become increasingly clear that during neural development in mammals, distinct ontogenetic stage-specific BAF complexes derived from combinatorial assembly of their subunits are formed in neural progenitors and post-mitotic neural cells. Proper functioning of the BAF complexes plays critical roles in neural development, including the establishment and maintenance of neural fates and functionality. Indeed, recent human exome sequencing and genome-wide association studies have revealed that mutations in BAF complex subunits are linked to neurodevelopmental disorders such as Coffin-Siris syndrome, Nicolaides-Baraitser syndrome, Kleefstra’s syndrome spectrum, Hirschsprung’s disease, autism spectrum disorder, and schizophrenia. In this review, we focus on the latest insights into the functions of BAF complexes during neural development and the plausible mechanistic basis of how mutations in known BAF subunits are associated with certain neurodevelopmental disorders.
TRPV1 regulates excitatory innervation of OLM neurons in the hippocampus.
Hurtado-Zavala,J.I.; Ramachandran,B.; Ahmed,S.; Halder,R.; Bolleyer,C.; Awasthi,A.; Stahlberg,M.A.; Wagener,R.J.; Anderson,K.; Drenan,R.M.; Lester,H.A.; Miwa,J.M.; Staiger,J.F.; Fischer,A.; Dean,C..
Nature Communications 8:15878, 2017.
DOI: 10.1038/ncomms15878
abstract link
TRPV1 is an ion channel activated by heat and pungent agents including capsaicin, and has been extensively studied in nociception of sensory neurons. However, the location and function of TRPV1 in the hippocampus is debated. We found that TRPV1 is expressed in oriens-lacunosum-moleculare (OLM) interneurons in the hippocampus, and promotes excitatory innervation. TRPV1 knockout mice have reduced glutamatergic innervation of OLM neurons. When activated by capsaicin, TRPV1 recruits more glutamatergic, but not GABAergic, terminals to OLM neurons in vitro. When TRPV1 is blocked, glutamatergic input to OLM neurons is dramatically reduced. Heterologous expression of TRPV1 also increases excitatory innervation. Moreover, TRPV1 knockouts have reduced Schaffer collateral LTP, which is rescued by activating OLM neurons with nicotine—via α2β2-containing nicotinic receptors—to bypass innervation defects. Our results reveal a synaptogenic function of TRPV1 in a specific interneuron population in the hippocampus, where it is important for gating hippocampal plasticity.
The functioning of a cortex without layers.
Guy J, Staiger JF.
Frontiers in Neuroanatomy 11:54, 2017.
abstract link
A major hallmark of cortical organization is the existence of a variable number of layers, i.e., sheets of neurons stacked on top of each other, in which neurons have certain commonalities. However, even for the neocortex, variable numbers of layers have been described and it is just a convention to distinguish six layers from each other. Whether cortical layers are a structural epiphenomenon caused by developmental dynamics or represent a functionally important modularization of cortical computation is still unknown. Here we present our insights from the reeler mutant mouse, a model for a developmental, “molecular lesion”-induced loss of cortical layering that could serve as ground truth of what an intact layering adds to the cortex in terms of functionality. We could demonstrate that the reeler neocortex shows no inversion of cortical layers but rather a severe disorganization that in the primary somatosensory cortex leads to the complete loss of layers. Nevertheless, the somatosensory system is well organized. When exploring an enriched environment with specific sets of whiskers, activity-dependent gene expression takes place in the corresponding modules. Precise whisker stimuli lead to the functional activation of somatotopically organized barrel columns as visualized by intrinsic signal optical imaging. Similar results were obtained in the reeler visual system. When analyzing pathways that could be responsible for preservation of tactile perception, lemniscal thalamic projections were found to be largely intact, despite the smearing of target neurons across the cortical mantle. However, with optogenetic experiments we found evidence for a mild dispersion of thalamic synapse targeting on layer IV-spiny stellate cells, together with a general weakening in thalamocortical input strength. This weakening of thalamic inputs was compensated by intracortical mechanisms involving increased recurrent excitation and/or reduced feedforward inhibition. In conclusion, a layer loss so far only led to the detection of subtle defects in sensory processing by reeler mice. This argues in favor of a view in which cortical layers are not an essential component for basic perception and cognition. A view also supported by recent studies in birds, which can have remarkable cognitive capacities despite the lack of a neocortex with multiple cortical layers. In conclusion, we suggest that future studies directed toward understanding cortical functions should rather focus on circuits specified by functional cell type composition than mere laminar location.
Crossreactivity of an antiserum directed to the gram-negative bacterium Neisseria gonorrhoeae with the SNARE-complex protein Snap23 correlates to impaired exocytosis in SH-SY5Y cells.
Almamy, A.; Schwerk, C.; Schroten, H.; Asif, A.R.; Reuss, B..
Journal of Molecular Neuroscience, 2017.
DOI 10.1007/s12031-017-0920-2
abstract
Abstract Early maternal infections with Neisseriagonorrhoeae (NG) correlate to an increased lifetime schizophreniarisk for the offspring, which might be due to animmune-mediated mechanism. Here, we investigated the interactionsof polyclonal antisera to NG (α-NG) with a firsttrimester prenatal brain multiprotein array, revealing amongothers the SNARE-complex protein Snap23 as a target antigenfor α-NG. This interaction was confirmed by Western blotanalysis with a recombinant Snap23 protein, whereas theclosely related Snap25 failed to interact with α-NG.Furthermore, a polyclonal antiserum to the closely relatedbacterium Neisseria meningitidis (α-NM) failed tointeract with both proteins. Functionally, in SH-SY5Y cells,α-NG pretreatment interfered with both insulin-induced vesiclerecycling, as revealed by uptake of the fluorescent endocytosismarker FM1-43, and insulin-dependent membranetranslocation of the glucose transporter GluT4. Similar effectscould be observed for an antiserum raised directly to Snap23,whereas a serum to Snap25 failed to do so. In conclusion,Snap23 seems to be a possible immune target for antigonococcalantibodies, the interactions of which seem at leastin vitro to interfere with vesicle-associated exocytosis.Whether these changes contribute to the correlation betweenmaternal gonococcal infections and psychosis in vivo remainsstill to be clarified.
Interactions of antisera to different Chlamydia and Chlamydophila species with the ribosomal protein RPS27a correlate with impaired protein synthesis in a human choroid plexus papilloma cell line..
Almamy A, Schwerk C, Schroten H, Ishikawa H, Asif AR, Reuss B.
IMMUNOL RES 65(6): 1110-1123, doi: 10.1007/s12026-017-8952-9, 2017.
abstract
Chlamydia trachomatis(CT) and theChlamydophilaspecies (CS)Chlamydophila pneumoniae(CPn), andChlamydophila psittaci(CPs) are suggested toinduce autoantibodies causative of several human autoim-mune disorders like rheumatoid arthritis and systemic lupuserythematosus (SLE). The aim of the present study was there-fore to identify cellular protein interaction partners withantisera to CT (α-CT) or CS (α-CS) and to identify functionalconsequences of such interaction in vitro. As detected with acommercial first trimester human prenatal brain multiproteinarray (hEXselect, Engine, Germany), the most frequent inter-action partner with bothα-CT andα-CS was the ribosomalsmall subunit protein RPS27a. This could be confirmed byWestern blot analysis with a recombinant RPS27a sample. Inaddition, immunocytochemistry with both antisera in the hu-man choroid plexus papilloma cell line HIBCPP revealed agranular cytoplasmic staining, and Western blot analysis withwhole-cell protein samples of HIBCPP cells revealed bothantisera to label protein bands of different molecular weightsand intensity. By 2D Western blot analysis and mass spec-trometry, one of the protein spots interacting withα-CT couldbe identified as the RPS27a. Finally, two different methods forthe detection of protein synthesis activity, the SUnSET tech-nique and an HPG fluorescence assay revealed both antiserato cause reduced translational activity in HIBCPP cells.Together with previous findings of RPS27a as an autoimmunetarget in a mouse model of systemic lupus erythematosus(SLE), these results suggest that infections with CT and/orCS could induce SLE-associated immune modifications.However, direct evidence for a pathogenic role of these inter-actions for SLE demands further investigations.
Nicotine reverses hypofrontality in animal models of addiction and schizophrenia.
Koukouli,F.; Rooy,M.; Tziotis,D.; Sailor,K.A.; O'Neill,H.C.; Levenga,J.; Witte,M.; Nilges,M.; Changeux,J.P.; Hoeffer,C.A.; Stitzel,J.A.; Gutkin,B.S.; DiGregorio,D.A.; Maskos,U..
Nature Medicine, 2017.
abstract link
2016
Antisera against Neisseria gonorrhoeae cross-react with specific brain proteins of the common marmoset monkey and other nonhuman primate species.
Reuss, B.; Asif, A.R.; Almamy,A.; Schwerk, C.; Schroten, H.; Ishikawa, H.; Drummer, C.; Behr, R..
Brain Research 1653:23-38, 2016.
doi: 10.1016/j.brainres.2016.10.012
abstract link
Intracortical Network Effects Preserve Thalamocortical Input Efficacy in a Cortex Without Layers.
Guy,J.; Sachkova,A.; Möck,M.; Witte,M.; Wagener,R.J.; Staiger,J.F..
Cerebral Cortex DOI 10.1093/cercor/bhw281, 2016.
abstract
Layer IV (LIV) of the rodent somatosensory cortex contains the somatotopic barrel field. Barrels receive much of the sensory input to the cortex through innervation by thalamocortical axons from the ventral posteromedial nucleus. In the reeler mouse, the absence of cortical layers results in the formation of mispositioned barrel-equivalent clusters of LIV fated neurons. Although functional imaging suggests that sensory input activates the cortex, little is known about the cellular and synaptic properties of identified excitatory neurons of the reeler cortex. We examined the properties of thalamic input to spiny stellate (SpS) neurons in the reeler cortex with in vitro electrophysiology, optogenetics, and subcellular channelrhodopsin-2-assisted circuit mapping (sCRACM). Our results indicate that reeler SpS neurons receive direct but weakened input from the thalamus, with a dispersed spatial distribution along the somatodendritic arbor. These results further document subtle alterations in functional connectivity concomitant of absent layering in the reeler mutant. We suggest that intracortical amplification mechanisms compensate for this weakening in order to allow reliable sensory transmission to the mutant neocortex
Parvalbumin- and vasoactive intestinal polypeptide-expressing neocortical interneurons impose differential inhibition on Martinotti cells.
Walker F, Möck M, Feyerabend M, Guy J, Wagener RJ, Schubert D, Staiger JF, Witte M.
Nature Comunications 7:13664 (DOI: 10.1038/ncomms13664, 2016.
abstract link
Disinhibition of cortical excitatory cell gate information flow through and between corticalcolumns. The major contribution of Martinotti cells (MC) is providing dendritic inhibition toexcitatory neurons and therefore they are a main component of disinhibitory connections.Here we show by means of optogenetics that MC in layers II/III of the mouse primarysomatosensory cortex are inhibited by both parvalbumin (PV)- and vasoactive intestinalpolypeptide (VIP)-expressing cells. Paired recordings revealed stronger synaptic inputonto MC from PV cells than from VIP cells. Moreover, PV cell input showed frequencyindependentdepression, whereas VIP cell input facilitated at high frequencies. Thesedifferences in the properties of the two unitary connections enable disinhibition with distincttemporal features.
Morphological Characteristics of Electrophysiologically Characterized Layer Vb Pyramidal Cells in Rat Barrel Cortex.
Jochen F. Staiger, Alexandre J. C. Loucif, Dirk Schubert, Martin Möck.
PLoS ONE 11 (10): e0164004, 2016.
doi:10.1371/journal. pone.0164004
abstract link
Layer Vb pyramidal cells are the major output neurons of the neocortex and transmit theoutcome of cortical columnar signal processing to distant target areas. At the same time they contribute to local tactile information processing by emitting recurrent axonal collateralsinto the columnar microcircuitry. It is, however, not known how exactly the two types of pyramidal cells, called slender-tufted and thick-tufted, contribute to the local circuitry.Here, we investigated in the rat barrel cortex the detailed quantitative morphology of biocytin-filled layer Vb pyramidal cells in vitro, which were characterized for their intrinsicelectrophysiology with special emphasis on their action potential firing pattern. Since westained the same slices for cytochrome oxidase, we could also perform layer- and columnrelated analyses. Our results suggest that in layer Vb the unambiguous action potential firing patterns "regular spiking (RS)" and "repetitive burst spiking (RB)" (previously called intrinsically burst spiking) correlate well with a distinct morphology. RS pyramidal cells are somatodendritically of the slender-tufted type and possess numerous local intralaminarand intracolumnar axonal collaterals, mostly reaching layer I. By contrast, their transcolumnar projections are less well developed. The RB pyramidal cells are somatodendritically of the thick-tufted type and show only relatively sparse local axonal collaterals, whichare preferentially emitted as long horizontal or oblique infragranular collaterals. However,contrary to many previous slice studies, a substantial number of these neurons alsoshowed axonal collaterals reaching layer I. Thus, electrophysiologically defined pyramidalcells of layer Vb show an input and output pattern which suggests RS cells to be more"locally segregating" signal processors whereas RB cells seem to act more on a "global integrative" scale.
Comment on “Principles of connectivity among morphologically defined cell types in adult neocortex”.
Barth, A.; Burkhalter, A.; Callaway, E.M.; Connors, B.W.; Cauli, B.; DeFelipe, J.; Feldmeyer, D.; Freund, T.; Kawaguchi, Y.; Kisvarday, Z.; Kubota, Y.; McBain, C.;Oberlaender, M.; Rossier, J.;Rudy, B.; Staiger, J.F.; Somogyi, P.; Tamas, G.;Yuste, R..
Science 353 (6304):1108-a, 2016.
abstract link
Jiang et al. (Research Article, 27 November 2015, aac9462) describe detailed experimentsthat substantially add to the knowledge of cortical microcircuitry and are unique in the numberof connections reported and the quality of interneuron reconstruction.The work appeals toexperts and laypersons because of the notion that it unveils new principles and provides acomplete description of cortical circuits.We provide a counterbalance to the authors’ claimsto give those less familiar with the minutiae of cortical circuits a better sense of thecontributions and the limitations of this study.
mSWI/SNF (BAF) complexes are indispensable for the neurogenesis and development of embryonic olfactory epithelium.
Bachmann C*, Nguyen H*, Rosenbusch J*, Pham L, Rabe T, Patwa M, Sokpor G, Seong RH, Ashery-Padan R, Mansouri A, Stoykova A, Staiger JF, Tuoc T..
Plos Genetics, 2016.
12(9), *equally contributed authors
abstract link
Neurogenesis is a key developmental event through which neurons are generated from neural stem/progenitor cells. Chromatin remodeling BAF (mSWI/SNF) complexes have been reported to play essential roles in the neurogenesis of the central nervous system. However, whether BAF complexes are required for neuron generation in the olfactory system is unknown. Here, we identified onscBAF and ornBAF complexes, which are specifically present in olfactory neural stem cells (oNSCs) and olfactory receptor neurons (ORNs), respectively. We demonstrated that BAF155 subunit is highly expressed in both oNSCs and ORNs, whereas high expression of BAF170 subunit is observed only in ORNs. We report that conditional deletion of BAF155, a core subunit in both onscBAF and ornBAF complexes, causes impaired proliferation of oNSCs as well as defective maturation and axonogenesis of ORNs in the developing olfactory epithelium (OE), while the high expression of BAF170 is important for maturation of ORNs. Interestingly, in the absence of BAF complexes in BAF155/BAF170 double-conditional knockout mice (dcKO), OE is not specified. Mechanistically, BAF complex is required for normal activation of Pax6-dependent transcriptional activity in stem cells/progenitors of the OE. Our findings unveil a novel mechanism mediated by the mSWI/SNF complex in OE neurogenesis and development.
Intracortical polyimide electrodes with a bioresorbable coating.
Hassler,C.; Guy,J.; Nietzschmann,M.; Plachta,D.T.; Staiger,J.F.; Stieglitz,T..
Biomed.Microdevices 18 (5):81, 2016.
abstract link
Polyimide based shaft electrodes were coated with a bioresorbable layer to stiffen them for intracortical insertion and to reduce the mechanical mismatch between the target tissue and the implanted device after degradation of the coating. Molten saccharose was used as coating material. In a proof-of-concept study, the electrodes were implanted into the cortex of Wistar rats and the insertion forces during implantation were recorded. Electrochemical impedance spectroscopy was performed immediately after implantation and up to 13 weeks after implantation to monitor the tissue response to the implanted electrodes. The recorded spectra were modeled with an equivalent circuit to differentiate the influence of the single components. In one rat, a peak in the encapsulation resistance was observable after two weeks of implantation, indicating the peak of the acute inflammatory response. In another rat, the lowest resistances were observed after four weeks, indicating the termination of the acute inflammatory response. Multiunit activity was recorded with an adequate signal to noise ratio to allow spike sorting. Histology was performed after 7, 45 and 201 days of implantation. The results showed the highest tissue reaction after 45 days and confirmed impedance data that acute inflammatory reactions terminate over time
Ablation of BAF170 in Developing and Postnatal Dentate Gyrus Affects Neural Stem Cell Proliferation, Differentiation, and Learning.
Tuoc T, Dere E, Radyushkin K, Pham L, Nguyen H, Tonchev AB, Sun G, Ronnenberg A, Shi Y, Staiger JF, Ehrenreich H, Stoykova A.
Molecular Neurobiology, 2016.
doi:10.1007/s12035-016-9948-5
abstract link
The BAF chromatin remodeling complex plays an essential role in brain development. However its function in postnatal neurogenesis in hippocampus is still unknown. Here, we show that in postnatal dentate gyrus (DG), the BAF170 subunit of the complex is expressed in radial glial-like (RGL) progenitors and in cell types involved in subsequent steps of adult neurogenesis including mature astrocytes. Conditional deletion of BAF170 during cortical late neurogenesis as well as during adult brain neurogenesis depletes the pool of RGL cells in DG, and promotes terminal astrocyte differentiation. These derangements are accompanied by distinct behavioral deficits, as reflected by an impaired accuracy of place responding in the Morris water maze test, during both hidden platform as well as reversal learning. Inducible deletion of BAF170 in DG during adult brain neurogenesis resulted in mild spatial learning deficits, having a more pronounced effect on spatial learning during the reversal test. These findings demonstrate involvement of BAF170-dependent chromatin remodeling in hippocampal neurogenesis and cognition and suggest a specific role of adult neurogenesis in DG in adaptive behavior.
Zbtb20 modulates the sequential generation of neuronal layers in developing cortex.
Tonchev AB, Tuoc T, Rosenthal EH, Studer M, Stoykova A.
Molecular Brain, 2016.
doi: 10.1186/s13041-016-0242-2.
abstract link
BACKGROUND:
During corticogenesis, genetic programs encoded in progenitor cells at different developmental stages and inherited in postmitotic neurons specify distinct layer and area identities. Transcription factor Zbtb20 has been shown to play a role for hippocampal development but whether it is implicated in mammalian neocortical morphogenesis remains unknown.
RESULTS:
Here, we report that during embyogenesis transcription factor Zbtb20 has a dynamic spatio-temporal expression pattern in mitotic cortical progenitors through which it modulates the sequential generation of cortical neuronal layer identities. Zbtb20 knock out mice exhibited enhanced populations of early born L6-L4 neuronal subtypes and a dramatic reduction of the late born L3/L2 neurons. This defect was due to a temporal misbalance in the production of earlier versus later born neurons, leading to a progressive diminishing of the progenitor pool for the generation of L3-L2 neurons. Zbtb20 implements these temporal effects in part by binding to promoter of the orphan nuclear receptor CoupTF1/Nr2f1. In addition to its effects exerted in cortical progenitors, the postmitotic expression of Zbtb20 in L3/L2 neurons starting at birth may contribute to their proper differentiation and migration.
CONCLUSIONS:
Our findings reveal Zbtb20 as a novel temporal regulator for the generation of layer-specific neuronal identities.
Epigenetic regulation by BAF (mSWI/SNF) chromatin remodeling complexes is indispensable for embryonic development.
Nguyen H*, Sokpor G*, Pham L, Rosenbusch J, Stoykova A, Staiger JF, Tuoc T.
Cell Cycle, 2016.
2016, 18;15(10):1317-24, equally contributed authors
abstract link
The multi-subunit chromatin-remodeling SWI/SNF (known as BAF for Brg/Brm-associated factor) complexes play essential roles in development. Studies have shown that the loss of individual BAF subunits often affects local chromatin structure and specific transcriptional programs. However, we do not fully understand how BAF complexes function in development because no animal mutant had been engineered to lack entire multi-subunit BAF complexes. Importantly, we recently reported that double conditional knock-out (dcKO) of the BAF155 and BAF170 core subunits in mice abolished the presence of the other BAF subunits in the developing cortex. The generated dcKO mutant provides a novel and powerful tool for investigating how entire BAF complexes affect cortical development. Using this model, we found that BAF complexes globally control the key heterochromatin marks, H3K27me2 and -3, by directly modulating the enzymatic activity of the H3K27 demethylases, Utx and Jmjd3. Here, we present further insights into how the scaffolding ability of the BAF155 and BAF170 core subunits maintains the stability of BAF complexes in the forebrain and throughout the embryo during development. Furthermore, we show that the loss of BAF complexes in the above-described model up-regulates H3K27me3 and impairs forebrain development and embryogenesis. These findings improve our understanding of epigenetic mechanisms and their modulation by the chromatin-remodeling SWI/SNF complexes that control embryonic development.
2015
Thalamocortical Connections Drive Intracortical Activation of Functional Columns in the Mislaminated Reeler Somatosensory Cortex .
Robin J. Wagener, Mirko Witte, Julien Guy, Nieves Mingo-Moreno, Sebastian Kügler, Jochen F. Staiger.
Cerebral Cortex, 2015.
abstract link
Neuronal wiring is key to proper neural information processing. Tactile information from the rodent's whiskers reaches the cortex via distinct anatomical pathways. The lemniscal pathway relays whisking and touch information from the ventral posteromedial thalamic nucleus to layer IV of the primary somatosensory "barrel" cortex. The disorganized neocortex of the reeler mouse is a model system that should severely compromise the ingrowth of thalamocortical axons (TCAs) into the cortex. Moreover, it could disrupt intracortical wiring. We found that neuronal intermingling within the reeler barrel cortex substantially exceeded previous descriptions, leading to the loss of layers. However, viral tracing revealed that TCAs still specifically targeted transgenically labeled spiny layer IV neurons. Slice electrophysiology and optogenetics proved that these connections represent functional synapses. In addition, we assessed intracortical activation via immediate-early-gene expression resulting from a behavioral exploration task. The cellular composition of activated neuronal ensembles suggests extensive similarities in intracolumnar information processing in the wild-type and reeler brains. We conclude that extensive ectopic positioning of neuronal partners can be compensated for by cell-autonomous mechanisms that allow for the establishment of proper connectivity. Thus, genetic neuronal fate seems to be of greater importance for correct cortical wiring than radial neuronal position.
Loss of BAF (mSWI/SNF) complexes causes global transcriptional and chromatin state changes in forebrain development.
Ramanathan Narayanan, Mehdi Pirouz, Cemil Kerimoglu, Linh Pham, Robin J. Wagener, Kamila A. Kiszka, Joachim Rosenbusch, Michael Kessel, Andre Fischer, Anastassia Stoykova, Jochen F. Staiger, and Tran Tuoc.
Cell Reports, 2015.
13, 1–13
abstract link
BAF (Brg/Brm-associated factors) complexes play important roles in development and are linked to chromatin plasticity at selected genomic loci. Nevertheless, a full understanding of their role in development and chromatin remodeling has been hindered by the absence of mutants completely lacking BAF complexes. Here, we report that the loss of BAF155/BAF170 in double-conditional knock-out (dcKO) mice eliminates all known BAF subunits, resulting in an overall reduction in active chromatin marks (H3K9Ac), a global increase in repressive marks (H3K27me2/3), and down-regulation of gene expression. We demonstrate that BAF complexes interact with H3K27 demethylases (JMJD3, UTX) and potentiate their activity. Importantly BAF complexes are indispensable for forebrain development, including proliferation, differentiation and cell survival of neural progenitor cells. Our findings reveal a molecular mechanism mediated by BAF complexes that controls global transcriptional program and chromatin state in development.
The disorganized visual cortex in reelin-deficient mice is functional and allows for enhanced plasticity.
Justyna Pielecka-Fortuna, Robin Jan Wagener, Ann-Kristin Martens, Bianka Goetze, Karl-Friedrich Schmidt, Jochen F. Staiger, Siegrid Löwel.
Brain Structure and Function; DOI: 10.1007/s00429-014-0866-x, 2015.
220(6):3449-67
abstract link
A hallmark of neocortical circuits is the segregation of processing streams into six distinct layers. The importance of this layered organization for cortical processing and plasticity is little understood. We investigated the structure, function and plasticity of primary visual cortex (V1) of adult mice deficient for the glycoprotein reelin and their wild-type littermates. In V1 of rl-/- mice, cells with different laminar fates are present at all cortical depths. Surprisingly, the (vertically) disorganized cortex maintains a precise retinotopic (horizontal) organization. Rl-/- mice have normal basic visual capabilities, but are compromised in more challenging perceptual tasks, such as orientation discrimination. Additionally, rl-/- animals learn and memorize a visual task as well as their wild-type littermates. Interestingly, reelin deficiency enhances visual cortical plasticity: juvenile-like ocular dominance plasticity is preserved into late adulthood. The present data offer an important insight into the capabilities of a disorganized cortical system to maintain basic functional properties.
Characterizing VIP Neurons in the Barrel Cortex of VIPcre/tdTomato Mice Reveals Layer-Specific Differences.
Prönneke A, Scheuer B, Wagener RJ, Möck M, Witte M, and Staiger JF.
Cereb. Cortex (2015) 25 (12): 4854-4868. doi: 10.1093/cercor/bhv202 , 2015.
abstract pdf link
Neocortical GABAergic interneurons have a profound impact on cortical circuitry and its information processing capacity. Distinct subgroups of inhibitory interneurons can be distinguished by molecular markers, such as parvalbumin, somatostatin, and vasoactive intestinal polypeptide (VIP). Among these, VIP-expressing interneurons sparked a substantial interest since these neurons seem to operate disinhibitory circuit motifs found in all major neocortical areas. Several of these recent studies used transgenic Vip-ires-cre mice to specifically target the population of VIP-expressing interneurons. This makes it necessary to elucidate in detail the sensitivity and specificity of Cre expression for VIP neurons in these animals. Thus, we quantitatively compared endogenous tdTomato with Vip fluorescence in situ hybridization and αVIP immunohistochemistry in the barrel cortex of VIPcre/tdTomato mice in a layer-specific manner. We show that VIPcre/tdTomato mice are highly sensitive and specific for the entire population of VIP-expressing neurons. In the barrel cortex, approximately 13% of all GABAergic neurons are VIP expressing. Most VIP neurons are found in layer II/III (∼60%), whereas approximately 40% are found in the other layers of the barrel cortex. Layer II/III VIP neurons are significantly different from VIP neurons in layers IV-VI in several morphological and membrane properties, which suggest layer-dependent differences in functionality.
Persistence of Functional Sensory Maps in the Absence of Cortical Layers in the Somatosensory Cortex of Reeler Mice.
Guy J, Wagener R, Möck M and Staiger JF.
Cerebral Cortex; doi: 10.1093/cercor/bhu052, 2015.
25(9):2517-28
abstract link
In rodents, layer IV of the primary somatosensory cortex contains the barrel field, where individual, large facial whiskers are represented as a dense cluster of cells. In the reeler mouse, a model of disturbed cortical development characterized by a loss of cortical lamination, the barrel field exists in a distorted manner. Little is known about the consequences of such a highly disturbed lamination on cortical function in this model. We used in vivo intrinsic signal optical imaging together with piezo-controlled whisker stimulation to explore sensory map organization and stimulus representation in the barrel field. We found that the loss of cortical layers in reeler mice had surprisingly little incidence on these properties. The overall topological order of whisker representations is highly preserved and the functional activation of individual whisker representations is similar in size and strength to wild-type controls. Because intrinsic imaging measures hemodynamic signals, we furthermore investigated the cortical blood vessel pattern of both genotypes, where we also did not detect major differences. In summary, the loss of the reelin protein results in a widespread disturbance of cortical development which compromises neither the establishment nor the function of an ordered, somatotopic map of the facial whiskers.
S1 laminar specialization.
Staiger JF.
Scholarpedia of touch, 2015.
ISBN: 978-94-6239-132-1
link
What types of neocortical GABAergic neurons do really exist?.
Jochen F. Staiger, Martin Möck, Alvar Prönneke, Mirko Witte .
e-Neuroforum (Springer), 2015.
abstract link
The neocortex is regarded as the brain structure responsible for mediating higher brain functions, like conscious perception of sensory signals, learning and memory or programming of goal-directed behavior. Cortical circuits that enable these functions are formed by, first, a larger population of excitatory so-called principal cells (i.e., glutamatergic pyramidal cells; ca. 80–85 %), which issue long-distance projections, in addition to local recurrent collaterals, which form the major part of local cortical excitatory circuits. A second, smaller population of inhibitory also called local or short-axoned interneurons (i.e., GABAergic neurons; ca. 15–20 %), however, contribute heavily to intracortical microcircuits too. They can be subdivided by their location in specific areas, layers, or columns, which possess specific input–output relationships, but also in terms of morphology, electrophysiology, molecular expression profiles, and subcellular target specificity. Here it is proposed that, at present, in the rodent neocortex this population of GABAergic neurons can be reasonably divided into six different types, mainly due to their unique axonal patterns and subcellular target specificity: (i) axo-axonic cells, (ii) basket cells, (iii) Martinotti cells, (iv) bipolar/bitufted cells, (v) neurogliaform cells, and (vi) projection neurons. These different types of GABAergic neurons strongly govern the working of cortical circuits for meaningful behavior by feed-forward and feedback inhibition as well as disinhibition. Thus, they keep excitation in check, perform gain modulation, and open temporal or spatial windows for input control or output generation.
A gradual depth-dependent change in connectivity features of supragranular pyramidal cells in rat barrel cortex.
Staiger JF, Bojak I, Miceli S, Schubert D..
Brain Struct Funct., 2015.
abstract link
Recent experimental evidence suggests a finer genetic, structural and functional subdivision of the layers which form a cortical column. The classical layer II/III (LII/III) of rodent neocortex integrates ascending sensory information with contextual cortical information for behavioral read-out. We systematically investigated to which extent regular-spiking supragranular pyramidal neurons, located at different depths within the cortex, show different input-output connectivity patterns. Combining glutamate uncaging with whole-cell recordings and biocytin filling, we revealed a novel cellular organization of LII/III: (1) "Lower LII/III" pyramidal cells receive a very strong excitatory input from lemniscal LIV and much fewer inputs from paralemniscal LVa. They project to all layers of the home column, including a feedback projection to LIV, whereas transcolumnar projections are relatively sparse. (2) "Upper LII/III" pyramidal cells also receive their strongest input from LIV, but in addition, a very strong and dense excitatory input from LVa. They project extensively to LII/III as well as LVa and Vb of their home and neighboring columns. (3) "Middle LII/III" pyramidal cell shows an intermediate connectivity phenotype that stands in many ways in between the features described for lower versus upper LII/III. "Lower LII/III" intracolumnarly segregates and transcolumnarly integrates lemniscal information, whereas "upper LII/III" seems to integrate lemniscal with paralemniscal information. This suggests a fine-grained functional subdivision of the supragranular compartment containing multiple circuits without any obvious cytoarchitectonic, other structural or functional correlate of a laminar border in rodent barrel cortex.
Cortical GABAergic neurons.
Staiger JF.
Brain Mapping: An encyclopedic reference, 2015.
abstract link
The neocortex is regarded as the brain structure responsible for mediating higher brain functions, like conscious perception of sensory signals, learning and memory, and programming of goal-directed behavior. Cortical circuits are formed by, first, a larger population of excitatory so-called principal cells (i.e., glutamatergic pyramidal cells; ca. 80–88%), which issue long-distance projections, in addition to local recurrent collaterals, which form the major part of local cortical excitatory circuits (Douglas, R. J., & Martin, K. A. C. (2007). Mapping the matrix: The ways of neocortex. Neuron 56, 226–238; Feldmeyer, D., Brecht, M., Helmchen, F., Petersen, C. C. H., Poulet, J. F. A., Staiger, J. F. (2013). Barrel cortex function. Progress in Neurobiology 103, 3–27; Schubert, D., Kötter, R., & Staiger, J. F. (2007). Mapping functional connectivity in barrel-related columns reveals layer- and cell type-specific microcircuits. Brain Structure and Function 212, 107–119). A second, smaller population of inhibitory also called local or short-axoned interneurons (i.e., GABAergic neurons; ca. 12–20%), however, contribute heavily to intracortical microcircuits, too. They can be subdivided by their location not only in specific areas, layers, or columns, which possess specific input–output relationships, but also in terms of morphology, electrophysiology, molecular expression profiles, and subcellular target specificity (Ascoli, G. A., Alonso-Nanclares, L., Anderson, S. A., Barrionuevo, G., & Benavides-Piccione, R. (2008). Petilla terminology: nomenclature of features of GABAergic interneurons of the cerebral cortex. Nature Reviews Neuroscience 9, 557–568; Markram, H., Toledo-Rodriguez, M., Wang, Y., Gupta, A., Silberberg, G., Wu, C. Z. (2004). Interneurons of the neocortical inhibitory system. Nature Reviews Neuroscience 5, 793–807). Here, it is proposed that, at present, in the rodent neocortex, this population of GABAergic neurons can be reasonably divided into six different types: (i) axo-axonic cells, (ii) basket cells, (iii) Martinotti cells, (iv) bipolar/bitufted cells, (v) neurogliaform cells, and (vi) projection neurons. A major topic for future research will be to determine how much within-type diversity does exist, that is, how many subtypes can reasonably be distinguished and what are their genuine functions in the cortical circuitry.
2014
Revisiting enigmatic cortical calretinin-expressing interneurons.
Cauli B., Zhou X., Tricoire L., Toussay X. and Staiger JF.
Frontiers in Neuroanatomy, 2014.
abstract link
Cortical calretinin (CR)-expressing interneurons represent a heterogeneous subpopulation of about 10–30% of GABAergic interneurons, which altogether total ca. 12–20% of all cortical neurons. In the rodent neocortex, CR cells display different somatodendritic morphologies ranging from bipolar to multipolar but the bipolar cells and their variations dominate. They are also diverse at the molecular level as they were shown to express numerous neuropeptides in different combinations including vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), neurokinin B (NKB) corticotrophin releasing factor (CRF), enkephalin (Enk) but also neuropeptide Y (NPY) and somatostatin (SOM) to a lesser extent. CR-expressing interneurons exhibit different firing behaviors such as adapting, bursting or irregular. They mainly originate from the caudal ganglionic eminence (CGE) but a subpopulation also derives from the dorsal part of the medial ganglionic eminence (MGE). Cortical GABAergic CR-expressing interneurons can be divided in two main populations: VIP-bipolar interneurons deriving from the CGE and SOM-Martinotti-like interneurons originating in the dorsal MGE. Although bipolar cells account for the majority of CR-expressing interneurons, the roles they play in cortical neuronal circuits and in the more general metabolic physiology of the brain remained elusive and enigmatic. The aim of this review is, firstly, to provide a comprehensive view of the morphological, molecular and electrophysiological features defining this cell type. We will, secondly, also summarize what is known about their place in the cortical circuit, their modulation by subcortical afferents and the functional roles they might play in neuronal processing and energy metabolism.
Impair Nerve Growth Factor-Dependent Neurite Outgrowth in Rat PC12 Cells.
Reuss B..
J Mol Neurosci, 2014.
abstract link
In children born from mothers with prenatal infections with the Gram-negative bacterium Neisseria gonorrhoeae, schizophrenia risk is increased in later life. Since cortical neuropil formation is frequently impaired during this disease, actions of a rabbit polyclonal antiserum directed to N. gonorrhoeae on neurite outgrowth in nerve growth factor-stimulated PC12 cells were investigated here. It turned out that 10 μg/ml of the antiserum leads indeed to a significant reduction in neurite outgrowth, whereas an antiserum directed to Neisseria meningitidis had no such effect. Furthermore, reduction in neurite outgrowth could be reversed by the neuroleptic drugs haloperidol, clozapine, risperidone, and olanzapine. On the molecular level, the observed effects seem to include the known neuritogenic transcription factors FoxO3a and Stat3, since reduced neurite outgrowth caused by the antiserum was accompanied by a reduced phosphorylation of both factors. In contrast, restitution of neurite outgrowth by neuroleptic drugs revealed no correlation to the phosphorylation state of these factors. The present report gives a first hint that bacterial infections could indeed lead to impaired neuropil formation in vitro; however, the in vivo relevance of this finding for schizophrenia pathogenesis remains to be clarified in the future.
Antibodies Directed to the Gram-Negative Bacterium Neisseria gonorrhoeae Cross-React with the 60 kDa Heat Shock Protein and Lead to Impaired Neurite Outgrowth in NTera2/D1 Cells.
Reuss B., Asif A.R..
J Mol Neurosci, 2014.
abstract link
Children of mothers with prenatal gonococcal infections are of increased risk to develop schizophrenic psychosis in later life. The present study hypothesizes an autoimmune mechanism for this, investigating interactions of a commercial rabbit antiserum directed to Neisseria gonorrhoeae (α-NG) with human NTera2/D1 cells, an established in vitro model for human neuronal differentiation. Immunocytochemistry demonstrated α-NG to label antigens on an intracellular organelle, which by Western blot analysis showed a molecular weight shortly below 72 kDa. An antiserum directed to Neisseria meningitidis (α-NM) reacts with an antigen shortly below 95 kDa, confirming antibody specificity of these interactions. Two-dimensional gel electrophoresis and partial Western transfer, allowed to localize an α-NG reactive protein spot which was identified by LC-Q-TOF MS/MS analysis as mitochondrial heat shock protein Hsp60. This was confirmed by Western blot analysis of α-NG immunoreactivity with a commercial Hsp60 protein sample, with which α-NM failed to interact. Finally, analysis of neurite outgrowth in retinoic acid-stimulated differentiating NTera2-D1 cells, demonstrates that α-NG but not α-NM treatment reduces neurite length. These results demonstrate that α-NG can interact with Hsp60 in vitro, whereas pathogenetic relevance of this interaction for psychotic symptomatology remains to be clarified.
Roles of chromatin remodeling BAF complex in neural differentiation and reprogramming.
Narayanan R and Tuoc TC .
Cell and Tissue Research (DOI: 10.1007/s00441-013-1791-7), 2014.
abstract link
ATP-dependent BAF chromatin remodeling complexes play an essential role in the maintenance of the gene expression program by regulating the structure of chromatin. There is increasing evidence that BAF complexes based on the alternative ATPase subunits, Brg1 and Brm, control the differentiation of neural stem cells (NSCs) to generate distinct neural cell types and modulate trans-differentiation between cell types. The BAF complexes have dedicated functions at different stages of neural differentiation that appear to arise by combinatorial assembly of their subunits. Furthermore, the differentiation of NSCs is regulated by the tight interactions between the BAF chromatin remodeling complex and the transcriptional machinery. Here, we review recent insights into the functional interaction between BAF complexes and various transcription factors (TFs) in neural differentiation and cellular reprogramming
Control of cerebral size and thickness.
Tuoc TC*, Pavlakis E, Tylkowski M and Stoykova A*.
Cellular and Molecular Life Sciences. DOI: 10.1007/s00018-014-1590-7, 2014.
abstract link
The mammalian neocortex is a sheet of cells covering the cerebrum that provides the structural basis for the perception of sensory inputs, motor output responses, cognitive function, and mental capacity of primates. Recent discoveries promote the concept that increased cortical surface size and thickness in phylogenetically advanced species is a result of an increased generation of neurons, a process that underlie higher cognitive and intellectual performance in higher primates and humans. Here, we review some of the advances in the field, focusing on the diversity of neocortical progenitors in different species, and cellular mechanisms of neurogenesis. We discuss recent views on intrinsic and extrinsic molecular determinants, including the role of epigenetic chromatin modifiers and microRNA, in the control of neuronal output in developing cortex and in the establishment of normal cortical architecture.
Depolarizing chloride gradient in developing cochlear nucleus neurons: Underlying mechanism and implication for calcium signaling.
Witte M, Reinert T., Dietz B., Nerlich J., Rübsamen R., Milenkovic I..
Neuroscience 261: 207-222 , 2014.
abstract link
Precise regulation of the chloride homeostasis crucially determines the action of inhibitory transmitters GABA and glycine and thereby endows neurons or even discrete neuronal compartments with distinct physiological responses to the same transmitters. In mammals, the signaling mediated by GABAA/glycine receptors shifts during early postnatal life from depolarization to hyperpolarization, due to delayed maturation of the chloride homeostasis system. While the activity of the secondary active, K+-Cl--extruding cotransporter KCC2, renders GABA/glycine hyperpolarizing in auditory brainstem nuclei of altricial rodents, the mechanisms contributing to the initially depolarizing transmembrane gradient for Cl- in respective neurons remained unknown. Here we used gramicidin-perforated patch recordings, non-invasive Cl- and Ca2+ imaging, and immunohistochemistry to identify the Cl--loading transporter that renders depolarizing effects of GABA/glycine in early postnatal life of spherical bushy cells in the cochlear nucleus of gerbil. Our data identify the 1Na+:1K+:2Cl- cotransporter 1 (NKCC1) as the major Cl--loader responsible for depolarizing action of GABA/glycine at postnatal days 3-5 (P3-5). Extracellular GABA/muscimol elicited calcium signaling through R-, L-, and T-type channels, which was dependent on bumetanide- and [Na+]e-sensitive Cl- accumulation. The "adult like", low intracellular Cl- concentration is established during the second postnatal week, through a mechanism engaging the NKCC1-down regulation between P5 and P15 and ongoing KCC2-mediated Cl--extrusion.
2013
BAF chromatin remodeling complex: Cortical size regulation and beyond.
Tuoc TC*, Narayanan R, Stoykova A*.
Cell Cycle, 12(8), 2013.
abstract link
The multi-subunit chromatin remodeling BAF complex controls different developmental processes. Using cortex-specific conditional knockout and overexpression mouse models, we have recently reported that BAF170, a subunit of the vertebrate BAF chromatin remodeling complex, interacts with transcription factor (TF) Pax6 to control cortical size and volume. The mechanistic basis includes suppression of the expression of Pax6 target genes, which are required for genesis of cortical intermediate progenitors (IPs) and specification of late neuronal subtype identity. In addition, we showed that a dynamic competition between BAF170 and BAF155 subunits within the BAF complex during progression of neurogenesis is a primary event in modulating the size of the mammalian cortex. Here, we present additional insights into the interaction between the BAF complex and TF Pax6 in the genesis of IPs of the developing cortex. Furthermore, we show that such competition between BAF170 and BAF155 is involved as well in the determination of the size of the embryonic body. Our results add new insights into a cell-intrinsic mechanism, mediated by the chromatin remodeling BAF complex, that controls vertebrate body shape and size.
Barrel cortex function.
Feldmeyer D, Brecht M, Helmchen F, Petersen CCH, Poulet JFA, Staiger JF, Luhmann HJ, Schwarz C.
Prog Neurobiol 103:3-27 , 2013.
abstract link
eocortex, the neuronal structure at the base of the remarkable cognitive skills of mammals, is a layered sheet of neuronal tissue composed of juxtaposed and interconnected columns. A cortical column is considered the basic module of cortical processing present in all cortical areas. It is believed to contain a characteristic microcircuit composed of a few thousand neurons. The high degree of cortical segmentation into vertical columns and horizontal layers is a boon for scientific investigation because it eases the systematic dissection and functional analysis of intrinsic as well as extrinsic connections of the column. In this review we will argue that in order to understand neocortical function one needs to combine a microscopic view, elucidating the workings of the local columnar microcircuits, with a macroscopic view, which keeps track of the linkage of distant cortical modules in different behavioral contexts. We will exemplify this strategy using the model system of vibrissal touch in mice and rats. On the macroscopic level vibrissal touch is an important sense for the subterranean rodents and has been honed by evolution to serve an array of distinct behaviors. Importantly, the vibrissae are moved actively to touch GÇô requiring intricate sensorimotor interactions. Vibrissal touch, therefore, offers ample opportunities to relate different behavioral contexts to specific interactions of distant columns. On the microscopic level, the cortical modules in primary somatosensory cortex process touch inputs at highest magnification and discreteness GÇô each whisker is represented by its own so-called barrel column. The cellular composition, intrinsic connectivity and functional aspects of the barrel column have been studied in great detail. Building on the versatility of genetic tools available in rodents, new, highly selective and flexible cellular and molecular tools to monitor and manipulate neuronal activity have been devised. Researchers have started to combine these with advanced and highly precise behavioral methods, on par with the precision known from monkey preparations. Therefore, the vibrissal touch model system is exquisitely positioned to combine the microscopic with the macroscopic view and promises to be instrumental in our understanding of neocortical function.
Characterization and Distribution of Reelin-Positive Interneuron Subtypes in the Rat Barrel Cortex..
Pohlkamp T, Dávid C, Cauli B, Gallopin T, Bouché E, Karagiannis A, May P, Herz J, Frotscher M, Staiger JF, Bock HH..
Cerebral Cortex (doi: 10.1093/cercor/bht161), 2013.
abstract link
GABAergic inhibitory interneurons (IN) represent a heterogeneous population with different electrophysiological, morphological, and molecular properties. The correct balance between interneuronal subtypes is important for brain function and is impaired in several neurological and psychiatric disorders. Here we show the data of 123 molecularly and electrophysiologically characterized neurons of juvenile rat barrel cortex acute slices, 48 of which expressed Reelin (Reln). Reln mRNA was exclusively detected in Gad65/67-positive cells but was found in interneuronal subtypes in different proportions: all cells of the adapting-Somatostatin (SST) cluster expressed Reln, whereas 63% of the adapting-neuropeptide Y (NPY, 50% of the fast-spiking Parvalbumin (PVALB), and 27% of the adapting/bursting-Vasoactive Intestinal Peptide (VIP) cluster were Reln-positive. Silhouette analysis revealed a high impact of the parameter Reln on cluster quality. By analyzing the co-localization of RELN immunoreactivity with those of different IN-markers, we found that RELN is produced layer-independently in SST-, NPY-, and NOS1-expressing INs, whereas co-localization of RELN and VIP was mostly absent. Of note, RELN co-localized with PVALB, predominantly in INs of layers IV/V (>30%). Our findings emphasize RELN's role as an important IN-marker protein and provide a basis for the functional characterization of Reln-expressing INs and its role in the regulation of inhibitory IN networks.
Mapping remodeling of thalamocortical projections in the living reeler mouse brain by diffusion tractography.
Harsan LA, Dávid C, Reisert M, Schnell S, Hennig J, von Elverfeldt D, Staiger JF.
Proc Natl Acad Sci USA 110: E1797-E1806, 2013.
abstract link
A major challenge in neuroscience is to accurately decipher in vivo the entire brain circuitry (connectome) at a microscopic level. Currently, the only methodology providing a global noninvasive window into structural brain connectivity is diffusion tractography. The extent to which the reconstructed pathways reflect realistic neuronal networks depends, however, on data acquisition and postprocessing factors. Through a unique combination of approaches, we designed and evaluated herein a framework for reliable fiber tracking and mapping of the living mouse brain connectome. One important wiring scheme, connecting gray matter regions and passing fiber-crossing areas, was closely examined: the lemniscal thalamocortical (TC) pathway. We quantitatively validated the TC projections inferred from in vivo tractography with correlative histological axonal tracing in the same wild-type and reeler mutant mice. We demonstrated noninvasively that changes in patterning of the cortical sheet, such as highly disorganized cortical lamination in reeler, led to spectacular compensatory remodeling of the TC pathway.
Chromatin regulation by BAF170 controls cerebral cortical size and thickness.
Tuoc TC, Boretius S, Sansom NS, Pitulescu ME, Frahm, J, Livesey FJ, Stoykova A.
Developmental Cell, 2013.
25 , 1–14
abstract link
Increased cortical size is essential to the enhanced intellectual capacity of primates during mammalian evolution. The mechanisms that control cortical size are largely unknown. Here, we show that mammalian BAF170, a subunit of the chromatin remodeling complex mSWI/SNF, is an intrinsic factor that controls cortical size. We find that conditional deletion of BAF170promotes indirect neurogenesis by increasing the pool of intermediate progenitors (IPs) and results in an enlarged cortex, whereas cortex-specific BAF170 over-expression results the opposite phenotype. Mechanistically, BAF170 competes with BAF155 subunit in the BAF complex, affecting euchromatin structure and thereby modulating the binding efficiency of the Pax6/REST-corepressor complex to Pax6 target genes that regulate the generation of IPs and late cortical progenitors. Our findings reveal a molecular mechanism mediated by the mSWI/SNF chromatin-remodeling complex that controls cortical architecture.
Optopatcher-An electrode holder for simultaneous intracellular patch-clamp recording and optical manipulation.
Katz Y, Yizhar O, Staiger,JF, Lampl I.
Journal of Neuroscience Methods 214:113-117, 2013.
abstract link
Optogenetics has rapidly become a standard method in neuroscience research. Although significant progress has been made in the development of molecular tools, refined techniques for combined light delivery and recording in vivo are still lacking. For example, simultaneous intracellular recording and light stimulation have only been possible by using two separate positioning systems. To overcome this limitation, we have developed a glass pipette holder which contains an additional port for the insertion of an optical fiber into the pipette. This device, which we called "optopatcher" allows whole cell patch-clamp recording simultaneously with direct projection of light from the recording pipette. The holder spares the use of an additional manipulator and, importantly, enables accurate, stable and reproducible illumination. In addition, replacement of standard pipettes is done as easily as with the available commercial holders. Here we used the optopatcher in vivo to record the membrane potential of neurons from different cortical layers in the motor cortex of transgenic mice expressing channelrhodopsin-2 under the Thy1 promoter. We demonstrate the utility of the optopatcher by recording LFP and intracellular responses to light stimulation.
New insights into the classification and nomenclature of cortical GABAergic interneurons.
De Felipe J, Lopez-Cruz PL, Benavides-Piccione R, Bielza C, Larranaga P, Anderson S, Burkhalter A, Cauli B, Fairen A, Feldmeyer D, Fishell G, Fitzpatrick D, Freund TF, Gonzalez-Burgos G, Hestrin S, Hill S, Hof PR, Huang J, Jones EG, Kawaguchi Y, Kisvarday Z, Kubota Y, Lewis, DA, Marin O, Markram H, McBain CJ, Meyer HS, Monyer H, Nelson SB, Rockland K, Rossier J, Rubenstein JL, Rudy B, Scanziani M, Shepherd GM, Sherwood CC, Staiger JF, Tamas G, Thomson A, Wang Y, Yuste R, Ascoli GA.
Nature Reviews Neuroscience 14: 202-16, 2013.
abstract link
A systematic classification and accepted nomenclature of neuron types is much needed but is currently lacking. This article describes a possible taxonomical solution for classifying GABAergic interneurons of the cerebral cortex based on a novel, web-based interactive system that allows experts to classify neurons with pre-determined criteria. Using Bayesian analysis and clustering algorithms on the resulting data, we investigated the suitability of several anatomical terms and neuron names for cortical GABAergic interneurons. Moreover, we show that supervised classification models could automatically categorize interneurons in agreement with experts' assignments. These results demonstrate a practical and objective approach to the naming, characterization and classification of neurons based on community consensus.
2012
Unique functional properties of somatostatin-expressing GABAergic neurons in mouse barrel cortex.
Gentet LJ, Kremer Y, Taniguchi H, Huang ZJ, Staiger J, Petersen CCH.
Nat Neurosci 15:607-612, 2012.
abstract link
Neocortical GABAergic neurons have diverse molecular, structural and electrophysiological features, but the functional correlates of this diversity are largely unknown. We found unique membrane potential dynamics of somatostatin-expressing (SOM) neurons in layer 2/3 of the primary somatosensory barrel cortex of awake behaving mice. SOM neurons were spontaneously active during periods of quiet wakefulness. However, SOM neurons hyperpolarized and reduced action potential firing in response to both passive and active whisker sensing, in contrast with all other recorded types of nearby neurons, which were excited by sensory input. Optogenetic inhibition of SOM neurons increased burst firing in nearby excitatory neurons. We hypothesize that the spontaneous activity of SOM neurons during quiet wakefulness provides a tonic inhibition to the distal dendrites of excitatory pyramidal neurons. Conversely, the inhibition of SOM cells during active cortical processing likely enhances distal dendritic excitability, which may be important for top-down computations and sensorimotor integration.
2011
Neuregulin 1 type III/ErbB signaling is crucial for Schwann cell colonization of sympathetic axons.
Heermann S, Schmücker J, Hinz U, Rickmann M, Unterbarnscheidt T, Schwab MH, Krieglstein K.
PLoS One. 6(12):e28692, 2011.
abstract link
Analysis of Schwann cell (SC) development has been hampered by the lack of growing axons in many commonly used in vitro assays. As a consequence, the molecular signals and cellular dynamics of SC development along peripheral axons are still only poorly understood. Here we use a superior cervical ganglion (SCG) explant assay, in which axons elongate after treatment with nerve growth factor (NGF). Migration as well as proliferation and apoptosis of endogenous SCG-derived SCs along sympathetic axons were studied in these cultures using pharmacological interference and time-lapse imaging. Inhibition of ErbB receptor tyrosine kinases leads to reduced SC proliferation, increased apoptosis and thereby severely interfered with SC migration to distal axonal sections and colonization of axons. Furthermore we demonstrate that SC colonization of axons is also strongly impaired in a specific null mutant of an ErbB receptor ligand, Neuregulin 1 (NRG1) type III. Taken together, using a novel SC development assay, we demonstrate that NRG1 type III serves as a critical axonal signal for glial ErbB receptors that drives SC development along sympathetic axons.
Chronic intracortical implantation of saccharose-coated flexible shaft electrodes into the cortex of rats.
Hassler C, Guy J, Nietzschmann M, Staiger JF, Stieglitz T.
Conf Proc IEEE Eng Med Biol Soc 2011: 644-47, 2011.
abstract link
Within this study, polyimide based shaft electrodes were fabricated and dip-coated in molten saccharose to stiffen them for insertion into the brain tissue. These electrodes were then implanted successfully into the cortex of whistar rats and the insertion force during implantation was recorded. Electrochemical impedance spectroscopy was performed immediately after implantation and in regular time intervals up to 201 days after implantation to monitor the tissue response to the implanted electrodes. Depending on the measured electrode pairs and the rats, the impedance spectra behaved different over time. Either they showed a constant decrease in impedance at 1 kHz, or they showed an initial decrease to increase again later. Furthermore, physiological signal recording was performed by stimulating the rats with acoustic signals and simultaneously recording the response on the different electrode sites. Multi-unit activity was detected until 37 days after implantation with an averaged signal-to-noise ratio of 2 to 4.
Lack of the endosomal SNAREs vti1a and vti1b led to significant impairments in neuronal development.
Kunwar AJ, Rickmann M, Backofen B, Browski SM, Rosenbusch J, Schöning S, Fleischmann T, Krieglstein K, Fischer von Mollard G.
Proc Natl Acad Sci U S A. 108(6):2575-80, 2011.
abstract link
Fusion between membranes is mediated by specific SNARE complexes. Here we report that fibroblasts survive the absence of the trans-Golgi network/early endosomal SNARE vti1a and the late endosomal SNARE vti1b with intact organelle morphology and minor trafficking defects. Because vti1a and vti1b are the only members of their SNARE subclass and the yeast homolog Vti1p is essential for cell survival, these data suggest that more distantly related SNAREs acquired the ability to function in endosomal traffic during evolution. However, absence of vti1a and vti1b resulted in perinatal lethality. Major axon tracts were missing, reduced in size, or misrouted in Vti1a(-/-) Vti1b(-/-) embryos. Progressive neurodegeneration was observed in most Vti1a(-/-) Vti1b(-/-) peripheral ganglia. Neurons were reduced by more than 95% in Vti1a(-/-) Vti1b(-/-) dorsal root and geniculate ganglia at embryonic day 18.5. These data suggest that special demands for endosomal membrane traffic could not be met in Vti1a(-/-) Vti1b(-/-) neurons. Vti1a(-/-) and Vti1b(-/-) single deficient mice were viable without these neuronal defects, indicating that they can substitute for each other in these processes.
2010
Tamoxifen and raloxifene modulate gap junction coupling during early phases of retinoic acid-dependent neuronal differentiation of NTera2/D1 cells.
Dahm L., Klugmann F., Gonzalez-Algaba a., Reuss B..
Cell Biol Toxicol, 2010.
abstract link
Gap junctions (GJ) represent a cellular communication system known to influence neuronal differentiation and survival. To assess a putative role of this system for neural effects of tamoxifen (TAM) and raloxifene (RAL), we used the human teratocarcinoma cell line NTera2/D1, retinoic acid (RA)-dependent neuronal differentiation of which is regulated by gap junctions formed of connexin43 (Cx43). As demonstrated by Western blot analysis, concentrations above 1 µmol/l for TAM, and 0.1 µmol/l for RAL lead to a temporary time- and concentration-dependent increase in Cx43 immunoreactivity, which reached a peak for TAM after 1 day and for RAL after 2 days. Immunocytochemical stainings revealed the increase in Cx43 immunoreactivity to result from an accumulation in intracellular compartments such as the Golgi apparatus or lysosomes. In addition, TAM and RAL were able to prevent the RA-dependent decrease of Cx43 immunoreactivity in NTera2/D1 cells, normally observed during neuronal differentiation. This suggested a suppression of neuronal differentiation to result from these substances. According to this, treatment of NTera2/D1 cells with 10 µmol/l TAM or RAL during weeks 1 and 2 of a 6 weeks RA-driven differentiation schedule impaired, whereas treatment during weeks 5 and 6 did not impair, neuronal differentiation of these cells. Modulation of GJ coupling between NTera2/D1 cells by TAM and RAL seems therefore to perturb early neuronal differentiation, whereas differentiated neurons in the mature brain seem to be not affected. These effects could be of importance for actions of TAM and RAL on early embryonic steps of nervous system formation.
Electrophysiological and morphological properties of Cajal-Retzius cells with different ontogenetic origins.
Sava BA, David CS, Teissier A, Pierani A, Staiger JF, Luhmann HJ, Kilb W.
Neuroscience 167:724-734, 2010.
abstract link
The different origins of Cajal-Retzius cells (CRc) as well as their diverse molecular profile suggest that this cell type may represent different neuronal subpopulations. In order to investigate whether CRc from different origins show distinct functional or morphological characteristics we used transgenic Dbx1(cre);ROSA26(YFP) mice in which two subpopulations of CRc, originating from the septum and ventral pallium (VP) at the pallial-subpallial border (PSB), were permanently labeled by yellow fluorescent protein (YFP) expression. Electrophysiological properties of YFP(+) and YFP(-) CRc were investigated by whole-cell patch-clamp recordings, while a thorough somatodendritic and axonal reconstruction of the biocytin labeled CRc was subsequently performed using a Neurolucida system. Our experiments revealed that no significant differences in resting membrane potential, input resistance or capacitance, hyperpolarization activated currents and most action potentials properties could be observed between YFP(+) and YFP(-) CRc. Both YFP(+) and YFP(-) CRc displayed spontaneous and carbachol-induced GABAergic postsynaptic currents with similar properties and comparable NMDA-receptor mediated glutamatergic inward currents that were equally affected by the NR2B specific antagonist ifenprodil. Morphological reconstructions revealed that dendritic and axonal parameters are similar between YFP(+) and YFP(-) CRc, while the dendritic compartment of YFP(+) CRc was slightly larger. In summary, no considerable differences in functional and morphological properties between YFP(+) and YFP(-) CRc could be observed in this study. These observations suggest that CRc of different ontogenic origins display comparable functional properties in the early postnatal cortex and therefore perform similar functions within the transient neuronal networks of the developing cortex.
Membrane potential dynamics of GABAergic neurons in the barrel cortex of behaving mice.
Gentet LJ, Avermann M, Matyas F, Staiger JF, Petersen CCH.
Neuron 65:422-435, 2010.
abstract link
Computations in cortical circuits are mediated by synaptic interactions between excitatory and inhibitory neurons, and yet we know little about their activity in awake animals. Here, through single and dual whole-cell recordings combined with two-photon microscopy in the barrel cortex of behaving mice, we directly compare the synaptically driven membrane potential dynamics of inhibitory and excitatory layer 2/3 neurons. We find that inhibitory neurons depolarize synchronously with excitatory neurons, but they are much more active with differential contributions of two classes of inhibitory neurons during different brain states. Fast-spiking GABAergic neurons dominate during quiet wakefulness, but during active wakefulness Non-fast-spiking GABAergic neurons depolarize, firing action potentials at increased rates. Sparse uncorrelated action potential firing in excitatory neurons is driven by fast, large, and cell-specific depolarization. In contrast, inhibitory neurons fire correlated action potentials at much higher frequencies driven by slower, smaller, and broadly synchronized depolarization.
In vivo diffusion tensor magnetic resonance imaging and fiber tracking of the mouse brain.
Harsan LA, Paul D, Schnell S, Kreher B, Hennig J, Staiger JF, von Elverfeldt D.
NMR in Biomedicine DOI:10.1002/nbm.1496, 2010.
abstract link
Until very recently, the study of neural architecture using fixed tissue has been a major scientific focus of neurologists and neuroanatomists. A non-invasive detailed insight into the brain's axonal connectivity in vivo has only become possible since the development of diffusion tensor magnetic resonance imaging (DT-MRI). This unique approach of analyzing axonal projections in the living brain was used in the present study to describe major white matter fiber tracts of the mouse brain and also to identify for the first time non-invasively the rich connectivity between the amygdala and different target regions. To overcome the difficulties associated with high spatially and temporally resolved DT-MRI measurements a 4-shot diffusion weighted spin echo (SE) echo planar imaging (EPI) protocol was adapted to mouse brain imaging at 9.4T. Diffusion tensor was calculated from data sets acquired by using 30 diffusion gradient directions while keeping the acquisition time at 91 min. Two fiber tracking algorithms were employed. A deterministic approach (fiber assignment by continuous tracking - FACT algorithm) allowed us to identify and generate the 3D representations of various neural pathways. A probabilistic approach was further used for the generation of probability maps of connectivity with which it was possible to investigate - in a statistical sense - all possible connecting pathways between selected seed points. We show here applications to determine the connection probability between regions belonging to the visual or limbic systems. This method does not require a priori knowledge about the projections' trajectories and is shown to be efficient even if the investigated pathway is long or three-dimensionally complex. Additionally, high resolution images of rotational invariant parameters of the diffusion tensor, such as fractional anisotropy, volume ratio or main eigenvalues allowed quantitative comparisons in-between regions of interest (ROIs) and showed significant differences between various white matter regions.
The somatosensory cortex of reeler mutant mice shows absent layering but intact formation and behavioral activation of columnar somatotopic maps.
Wagener RJ, David C, Zhao S, Haas CA, Staiger JF .
J Neurosci 30:15700-15709, 2010.
abstract link
Sensory information acquired via the large facial whiskers is processed and relayed in the whisker-to-barrel pathway, which shows multiple somatotopic maps of the receptor periphery. These maps consist of individual structural modules, the development of which may require intact cortical lamination. In the present study we examined the whisker-to-barrel pathway in the reeler mouse and thus used a model with disturbed cortical organization. A combination of histological (fluorescent Nissl and cytochrome oxidase staining) as well as molecular methods (c-Fos and laminar markers Rgs8, RORB, and ER81 expression) revealed wild type-equivalent modules in reeler. At the neocortical level, however, we found extensive alterations in the layout of the individual modules of the map. Nevertheless, they showed a columnar organization that included compartments equivalent to those of their wild-type counterparts. Moreover, all examined modules showed distinct activation as a consequence of behavioral whisker stimulation. Analysis of the magnitude of the cortical lamination defect surprisingly revealed an extensive disorganization, rather than an inversion, as assumed previously. Striking developmental plasticity of thalamic innervation, as suggested by vGluT2 immunohistochemistry, seems to ensure the proper formation of columnar modules and topological maps even under highly disorganized conditions.
Roles of the ubiquitin-proteosome system in neurogenesis.
Tuoc TC, Stoykova A.
Cell Cycle, 2010.
9(16):3174-3180.
abstract link
The ubiquitin-proteosome system (UPS) is a non-lysosomal proteolysis system involved in the degradation of irrelevant/misfolded intracellular proteins. The protein substrates of this system are tagged by ubiquitin in sequential reactions that target them for proteasome-dependent destruction. In the developing central nervous system, ubiquitin-mediated proteolysis has recently emerged as an important player in the regulation of neural progenitor proliferation, cell specification, neuronal differentiation, maturation, and migration. E3 ubiquitin ligases are crucial components in the UPS because they provide the specificity that determines which substrates are targeted for ubiquitin-dependent proteolysis. In this review, we discuss the molecular mechanisms of the UPS, focusing primarily on the roles of E3 ligases and their substrates in sequential steps of neurogenesis.
Presynaptic and postsynaptic origin of multicomponent extracellular spike waveforms at the endbulb of held/spherical bushy cell synapse..
Typlt M., Haustein M., Dietz B., Steinert J., Witte M., Englitz B., Milenkovic I., Kopp-Scheinpflug C., Forsythe I., Rübsamen R..
Eur J Neuroscience 31(9):1574-81 , 2010.
abstract link
Extracellular signals from the endbulb of Held-spherical bushy cell (SBC) synapse exhibit up to three component waves ('P', 'A' and 'B'). Signals lacking the third component (B) are frequently observed but as the origin of each of the components is uncertain, interpretation of this lack of B has been controversial: is it a failure to release transmitter or a failure to generate or propagate an action potential? Our aim was to determine the origin of each component. We combined single- and multiunit in vitro methods in Mongolian gerbils and Wistar rats and used pharmacological tools to modulate glutamate receptors or voltage-gated sodium channels. Simultaneous extra- and intracellular recordings from single SBCs demonstrated a presynaptic origin of the P-component, consistent with data obtained with multielectrode array recordings of local field potentials. The later components (A and B) correspond to the excitatory postsynaptic potential (EPSP) and action potential of the SBC, respectively. These results allow a clear interpretation of in vivo extracellular signals. We conclude that action potential failures occurring at the endbulb-SBC synaptic junction largely reflect failures of the EPSP to trigger an action potential and not failures of synaptic transmission. The data provide the basis for future investigation of convergence of excitatory and inhibitory inputs in modulating transmission at a fully functional neuronal system using physiological stimulation.
2009
P2 receptor-mediated signaling in spherical bushy cells of the mammalian cochlear nucleus..
Milenkovic, I., Rinke I, Witte M, Dietz, B., Rübsamen R..
J Neurophysiol. 102(3):1821-1833, 2009.
abstract link
Purinoreceptors of the P2 family contribute strongly to signaling in the cochlea, but little is known about the effects of purinergic neurotransmission in the central auditory system. Here we examine P2 receptor-mediated signaling in the large spherical bushy cells (SBCs) of Mongolian gerbils around the onset of acoustically evoked signal processing (P9-P14). Brief adenosine 5'-O-(3-thiotriphosphate) (ATPgammaS) application evoked inward current, membrane depolarization, and somatic Ca2+ signals. Moreover, ATPgammaS changed the SBCs firing pattern from phasic to tonic, when the application was synchronized with depolarizing current injection. This bursting discharge activity was dependent on [Ca2+]i and Ca2+-dependent protein kinase (PKC) activity and is presumably caused by modulation of low-threshold K+ conductance. Activation of P2Y1 receptors could not evoke these changes per se, thus it was concluded that the involvement of P2X receptors seems to be necessary. Ca2+ imaging data showed that both P2X and P2Y1 receptors mediate Ca2+ signals in SBCs where P2Y1 receptors most likely activate the PLC-IP3 (inositol trisphosphate) pathway and release Ca2+ from internal stores. Immunohistochemical staining confirmed the expression of P2X2 and P2Y1 receptor proteins in SBCs, providing additional evidence for the involvement of both receptors in signal transduction in these neurons. Purinergic signaling might modulate excitability of SBCs and thereby contribute to regulation of synaptic strength. Functionally, the increase in firing rate mediated by P2 receptors could reduce temporal precision of the postsynaptic firing, e.g., phase locking, which has an immediate effect on signal processing related to sound localization. This might provide a mechanism for adaptation to the ambient acoustic environment.
Local circuits targeting parvalbumin-containing interneurons in layer IV of rat barrel cortex.
Staiger JF, Zuschratter W, Luhmann HJ, Schubert D.
Brain Struct Func 214:1-13; DOI 10.1007/s00429-009-0225-5, 2009.
abstract link
Interactions between inhibitory interneurons and excitatory spiny neurons and also other inhibitory cells represent fundamental network properties which cause the so-called thalamo-cortical response transformation and account for the well-known receptive field differences of cortical layer IV versus thalamic neurons. We investigated the currently largely unknown morphological basis of these interactions utilizing acute slice preparations of barrel cortex in P19-21 rats. Layer IV spiny (spiny stellate, star pyramidal and pyramidal) neurons or inhibitory (basket and bitufted) interneurons were electrophysiologically characterized and intracellularly biocytin-labeled. In the same slice, we stained parvalbumin-immunoreactive (PV-ir) interneurons as putative target cells after which the tissue was subjected to confocal image acquisition. Parallel experiments confirmed the existence of synaptic contacts in these types of connection by correlated light and electron microscopy. The axons of the filled neurons differentially targeted barrel PV-ir interneurons: (1) The relative number of all contacted PV-ir cells within the axonal sphere was 5–17% for spiny (n = 10), 32 and 58% for basket (n = 2) and 12 and 13% for bitufted (n = 2) cells. (2) The preferential subcellular site which was contacted on PV-ir target cells was somatic for four and dendritic for five spiny cells; for basket cells, there was a somatic and for bitufted cells a dendritic preference in each examined case. (3) The highest number of contacts on a single PV-ir cell was 9 (4 somatic and 5 dendritic) for spiny neurons, 15 (10 somatic and 5 dendritic) for basket cells and 4 (1 somatic and 3 dendritic) for bitufted cells. These patterns suggest a cell type-dependent communication within layer IV microcircuits in which PV-ir interneurons provide not only feed-forward but also feedback inhibition thus triggering the thalamo-cortical response transformation.
Classification of NPY-expressing neocortical interneurons.
Karagiannis A, Gallopin T, David C, Battaglia D, Geoffroy H, Rossier J, Hillman EMC, Staiger JF, Cauli B.
J Neurosci 29:3642-3659, 2009.
abstract link
Neuropeptide Y (NPY) is an abundant neuropeptide of the neocortex involved in numerous physiological and pathological processes. Because of the large electrophysiological, molecular, and morphological diversity of NPY-expressing neurons their precise identity remains unclear. To define distinct populations of NPY neurons we characterized, in acute slices of rat barrel cortex, 200 cortical neurons of layers I-IV by means of whole-cell patch-clamp recordings, biocytin labeling, and single-cell reverse transcriptase-PCR designed to probe for the expression of well established molecular markers for cortical neurons. To classify reliably cortical NPY neurons, we used and compared different unsupervised clustering algorithms based on laminar location and electrophysiological and molecular properties. These classification schemes confirmed that NPY neurons are nearly exclusively GABAergic and consistently disclosed three main types of NPY-expressing interneurons. (1) Neurogliaform-like neurons exhibiting a dense axonal arbor, were the most frequent and superficial, and substantially expressed the neuronal isoform of nitric oxide synthase. (2) Martinotti-like cells characterized by an ascending axon ramifying in layer I coexpressed somatostatin and were the most excitable type. (3) Among fast-spiking and parvalbumin-positive basket cells, NPY expression was correlated with pronounced spike latency. By clarifying the diversity of cortical NPY neurons, this study establishes a basis for future investigations aiming at elucidating their physiological roles.
Selective cortical layering abnormalities and behavioral deficits in cortex-specific Pax6 knock-out mice.
Tuoc TC*, Radyushkin K*, Tonchev AB, Pinon MC, Ashery-Padan R, Molnar Z, Davidoff MS, Stoykova A.
J Neurosci, 2009.
29(26):8335-8349
abstract link
The transcription factor Pax6 has been implicated in neocortical neurogenesis in vertebrates, including humans. Analyses of the role of Pax6 in layer formation and cognitive abilities have been hampered by perinatal lethality of Pax6 mutants. Here, we generated viable mutants exhibiting timed, restricted inactivation of Pax6 during early and late cortical neurogenesis using Emx1-Cre and hGFAP-Cre lines, respectively. The disruption of Pax6 at the onset of neurogenesis using Emx1-Cre line resulted in premature cell cycle exit of early progenitors, increase of early born neuronal subsets located in the marginal zone and lower layers, and a nearly complete absence of upper layer neurons, especially in the rostral cortex. Furthermore, progenitors, which accumulated in the enlarged germinal neuroepithelium at the pallial/subpallial border in the Pax6 mutants, produced an excess of oligodendrocytes. The inactivation of Pax6 after generation of the lower neuronal layers using hGFAP-Cre line did not affect specification or numbers of late-born neurons, indicating that the severe reduction of upper layer neurons in Pax6 deficiency is mostly attributable to a depletion of the progenitor pool, available for late neurogenesis. We further show that Pax6(fl/fl);Emx1-Cre mutants exhibited deficiencies in sensorimotor information integration, and both hippocampus-dependent short-term and neocortex-dependent long-term memory recall. Because a majority of the morphological and behavior disabilities of the Pax6 mutant mice parallel abnormalities reported for aniridia patients, a condition caused by PAX6 haploinsufficiency, the Pax6 conditional mutant mice generated here represent a valuable genetic tool to understand how the developmental cortical disruption can lead to a human behavior abnormality.
In vivo requirement of TGF-beta/GDNF cooperativity in mouse development: focus on the neurotrophic hypothesis.
Rahhal B, Heermann S, Ferdinand A, Rosenbusch J, Rickmann M, Krieglstein K.
Int J Dev Neurosci. 27(1):97-102, 2009.
abstract link
Neurotrophic factors are well-recognized extracellular signaling molecules that regulate neuron development including neurite growth, survival and maturation of neuronal phenotypes in the central and peripheral nervous system. Previous studies have suggested that TGF-beta plays a key role in the regulation of neuron survival and death and potentiates the neurotrophic activity of several neurotrophic factors, most strikingly of GDNF. To test the physiological relevance of this finding, TGF-beta2/GDNF double mutant (d-ko) mice were generated. Double mutant mice die at birth like single mutants due to kidney agenesis (GDNF-/-) and congential cyanosis (TGF-beta2-/-), respectively. To test for the in vivo relevance of TGF-beta2/GDNF cooperativity to regulate neuron survival, mesencephalic dopaminergic neurons, lumbar motoneurons, as well as neurons of the lumbar dorsal root ganglion and the superior cervical ganglion were investigated. No loss of mesencephalic dopaminergic neurons was observed in double mutant mice at E18.5. A partial reduction in neuron numbers was observed in lumbar motoneurons, sensory and sympathetic neurons in GDNF single mutants, which was further reduced in TGF-beta2/GDNF double mutant mice at E18.5. However, TGF-beta2 single mutant mice showed no loss of neurons. These data point towards a cooperative role of TGF-beta2 and GDNF with regard to promotion of survival within the peripheral motor and sensory systems investigated.
2008
Loss of transforming growth factor-beta 2 leads to impairment of central synapse function.
Heupel K, Sargsyan V, Plomp JJ, Rickmann M, Varoqueaux F, Zhang W, Krieglstein K.
Neural Dev. 3:25, 2008.
abstract link
BACKGROUND:
The formation of functional synapses is a crucial event in neuronal network formation, and with regard to regulation of breathing it is essential for life. Members of the transforming growth factor-beta (TGF-beta) superfamily act as intercellular signaling molecules during synaptogenesis of the neuromuscular junction of Drosophila and are involved in synaptic function of sensory neurons of Aplysia.
RESULTS:
Here we show that while TGF-beta2 is not crucial for the morphology and function of the neuromuscular junction of the diaphragm muscle of mice, it is essential for proper synaptic function in the pre-Bötzinger complex, a central rhythm organizer located in the brainstem. Genetic deletion of TGF-beta2 in mice strongly impaired both GABA/glycinergic and glutamatergic synaptic transmission in the pre-Bötzinger complex area, while numbers and morphology of central synapses of knock-out animals were indistinguishable from their wild-type littermates at embryonic day 18.5.
CONCLUSION:
The results demonstrate that TGF-beta2 influences synaptic function, rather than synaptogenesis, specifically at central synapses. The functional alterations in the respiratory center of the brain are probably the underlying cause of the perinatal death of the TGF-beta2 knock-out mice.
Efficient recruitment of layer 2/3 interneurons by excitatory layer 4 input in single columns of rat somatosensory cortex.
Helmstaedter M, Staiger JF, Sakmann B, Feldmeyer D.
J Neurosci 28:8273-8284, 2008.
abstract link
Interneurons in layers 2/3 are excited by pyramidal cells within the same layer (Reyes et al., 1998; Gupta et al., 2000), but little is known about translaminar innervation of these interneurons by spiny neurons in the main cortical input layer 4 (L4). Here, we investigated (1) how efficiently L4 spiny neurons excite L2/3 interneurons via monosynaptic connections, (2) whether glutamate release from axon terminals of L4 spiny neurons depends on the identity of the postsynaptic interneuron, and (3) how L4-to-L2/3 interneuron connections compare with L4-to-L2/3 pyramidal neuron connections. We recorded from pairs of L4 spiny neurons and L2/3 interneurons in acute slices of rat barrel cortex of postnatal day 20 (P20) to P29 rats. The L4-to-L2/3 interneuron connections had an average unitary EPSP of 1.2 ± 1.1 mV. We found an average of 2.3 ± 0.8 contacts per connection, and the L4-to-L2/3 interneuron innervation domains were mostly column restricted. Unitary EPSP amplitudes and paired-pulse ratios in the L4-to-L2/3 interneuron connections depended on the “group” of the postsynaptic interneuron. Averaged over all L4-to-L2/3 interneuron connections, unitary EPSP amplitudes were 1.8-fold higher than in the translaminar L4-to-L2/3 pyramidal cell connections. Our results suggest that L4 spiny neurons may more efficiently recruit L2/3 interneurons than L2/3 pyramidal neurons, and that glutamate release from translaminar boutons of L4 spiny neuron axons is target cell specific.
Petilla Terminology: Nomenclature of features of GABAergic interneurons of the cerebral cortex.
Ascoli GA, Alonso-Nanclares L, Anderson SA, Barrionuevo G, Benavides-Piccione R, Burkhalter A, Buzsaki G, Cauli B, DeFelipe J, Fairén A, Feldmeyer D, Fishell G, Fregnac Y, Freund TF, Karube F, Gardner D, Gardner EP, Goldberg JH, Helmstaedter M, Hestrin S, Kisvarday Z, Lambolez B, Lewis D, Marin O, Markram H, Muñoz A, Packer A, Petersen C, Rockland K, Rossier J, Rudy B, Somogyi P, Staiger JF, Tamas G, Thomson AM, Toledo-Rodriguez M, Wang Y, West DC, and Yuste R.
Nat Rev Neurosci 9:557-568, 2008.
abstract link
Neuroscience produces a vast amount of data from an enormous diversity of neurons. A neuronal classification system is essential to organize such data and the knowledge that is derived from them. Classification depends on the unequivocal identification of the features that distinguish one type of neuron from another. The problems inherent in this are particularly acute when studying cortical interneurons. To tackle this, we convened a representative group of researchers to agree on a set of terms to describe the anatomical, physiological and molecular features of GABAergic interneurons of the cerebral cortex. The resulting terminology might provide a stepping stone towards a future classification of these complex and heterogeneous cells. Consistent adoption will be important for the success of such an initiative, and we also encourage the active involvement of the broader scientific community in the dynamic evolution of this project.
Altered molecular regionalization and normal thalamocortical connections in cortex-specific Pax6 knock-out mice.
Pinon MC*, Tuoc TC*, Ashery-Padan R, Molnar Z, Stoykova A.
J Neurosci, 2008.
28(35):8724-8734.
abstract link
Transcription factor Pax6 exerts a prominent rostrolateral(high) to caudomedial(low) expression gradient in the cortical progenitors and have been implicated in regulation of area identity in the mammalian cortex. Herein, we analyzed the role of Pax6 in molecular arealization and development of thalamocortical connections in the juvenile cortex-specific conditional Pax6 knock-out mice (Pax6cKO). Using a set of molecular markers of positional identity (Id2, Cadherin6, COUP-TF1, RZRbeta, and EphA7), we show that, in the juvenile Pax6cKO, the relative size of caudal cortical areas (putative visual and somatosensory) are mildly enlarged, whereas the rostral domain (putative motor) is severely reduced. Despite the rostral shift of graded expression of areal markers, the distribution of area-specific thalamocortical and corticofugal projections appear normal in the Pax6cKO. This indicates that change of the size of cortical areas is not accompanied by a change in cortical identity. We show furthermore that, despite a severe depletion of supragranular cortical layers and accumulation of cells along the pallial-subpallial boundary, thalamocortical fibers establish a periphery-related pattern of the somatosensory cortex in normal position in Pax6cKO. Our findings indicate that Pax6 expression gradients in cortical progenitors do not directly impart thalamocortical or corticofugal areal identity.
Trim11 modulates the function of neurogenic transcription factor Pax6 through ubiquitin-proteosome system.
Tuoc TC, Stoykova A.
Genes Dev, 2008.
22(14):1972-1986.
abstract link
The transcription factor Pax6 is an important developmental regulator. Spatiotemporal control of Pax6 expression during embryogenesis is crucial for regulating distinct aspects of cortical development. Here, we report that Trim11, a member of the TRIM/RBCC protein family of E3 ubiquitin ligases, interacts with Pax6 and mediates Pax6 degradation via the ubiquitin-proteasome system. Trim11 overexpression decreases endogenous Pax6 protein levels and represses Pax6 functions, including Pax6-dependent transactivation and neurogenesis. Abrogation of endogenous Trim11 expression in the developing cortex increases the level of insoluble forms of Pax6 and enhances apoptosis. We provide evidence that the B30.2 domain of Trim11 is essential for the clearance of insoluble cell proteins. Furthermore, we show that the expression of Trim11 is directly regulated by Pax6 in developing cortex in vivo. Our findings indicate that an autoregulatory feedback loop between Trim11 and Pax6 maintains a balance between the levels of Pax6 and Trim11 proteins in cortical progenitors, having an essential role for the Pax6-dependent neurogenesis.
Er81 is a downstream target of Pax6 in cortical progenitors.
Tuoc TC, Stoykova A.
BMC Dev Biol, 2008.
2008, 8:23.
abstract link
BACKGROUND:
Although the transcription factor Pax6 plays an essential role in neurogenesis, layer formation and arealization in the developing mammalian cortex, the mechanisms by which it accomplishes these regulatory functions are largely unknown. Pax6 and the ETS family transcription factor Er81, which is presumed to play a role in the specification of a sublineage of layer 5 projection neurons, are expressed with a prominent rostrolateral-high to caudomedial-low gradient in cortical progenitors. In the absence of functional Pax6, progenitors do not express Er81 and the rostrolateral cortex lacks Er81-positive layer 5 neurons. In this study, we investigated the transcriptional regulation of Er81 and provide evidence that Er81 is a direct target of Pax6.
RESULTS:
We identified and analyzed the regulatory function of an evolutionarily conserved upstream DNA sequence in the putative mouse Er81 promoter. Three potential Pax6 binding sites were identified in this region. We found that the presence of one of these sites is necessary and sufficient for full activation of the Er81 promoter in Pax6-transfected HeLa cells, while other still unknown factors appear to contribute to Er81 promoter activity in cortical progenitors and neuronal cells. The results suggest that endogenous Pax6, which is expressed at the highest level in progenitors of the rostrolateral cortex, exerts region-specific control of Er81 activity, thus specifying a subpopulation of layer 5 projection neurons.
CONCLUSION:
We conclude that the genetic interplay between the transcription factors, Pax6 and Er81, is responsible, in part, for the regional specification of a distinct sublineage of layer 5 projection neurons.
2007
Development of chloride-mediated inhibition in neurons of the anteroventral cochlear nucleus of gerbil (Meriones unguiculatus).
Milenkovic I., Witte M., Turecek R., Heinrich M., Reinert T., Rübsamen R..
J Neurophysiol 98: 1634-1644, 2007.
abstract link
At the initial stages in neuronal development, GABAergic and glycinergic neurotransmission exert depolarizing responses, assumed to be of importance for maturation, which in turn shift to hyperpolarizing in early postnatal life due to development of the chloride homeostasis system. Spherical bushy cells (SBC) of the mammalian cochlear nucleus integrate excitatory glutamatergic inputs with inhibitory (GABAergic and glycinergic) inputs to compute signals that contribute to sound localization based on interaural time differences. To provide a fundamental understanding of the properties of GABAergic neurotransmission in mammalian cochlear nucleus, we investigated the reversal potential of the GABA-evoked currents (E GABA) by means of gramicidin-perforated-patch recordings in developing SBC. The action of GABA switches from depolarizing to hyperpolarizing by the postnatal day 7 due to the negative shift in E GABA. Furthermore, we studied the expression pattern of the K+-Cl(-)-extruding cotransporter KCC2, previously shown to induce a switch from neonatal Cl(-) efflux to the mature Cl(-) influx in various neuron types, thereby causing a shift from depolarizing to hyperpolarizing GABA action. The KCC2 protein is expressed in SBC already at birth, yet its activity is attained toward the end of the first postnatal week as indicated by pharmacological inhibition. Interruption of the Cl(-) extrusion by [(dihydroindenyl)oxy] alkanoic acid or furosemide gradually shifted E(GABA) in positive direction with increasing maturity, suggesting that KCC2 could be involved in maintaining low [Cl(-)]i after the postnatal day 7 thereby providing the hyperpolarizing Cl(-)-mediated inhibition in SBC.
Cholinergic control of spindle bursts in neonatal rat visual cortex.
Hanganu IL, Staiger JF, Ben-Ari Y, Khazipov R.
J Neurosci 27:5694-5705, 2007.
abstract link
Acetylcholine (ACh) is known to shape the adult neocortical activity related to behavioral states and processing of sensory information. However, the impact of cholinergic input on the neonatal neuronal activity remains widely unknown. Early during development, the principal activity pattern in the primary visual (V1) cortex is the intermittent self-organized spindle burst oscillation that can be driven by the retinal waves. Here, we assessed the relationship between this early activity pattern and the cholinergic drive by either blocking or augmenting the cholinergic input and investigating the resultant effects on the activity of the rat visual cortex during the first postnatal week in vivo. Blockade of the muscarinic receptors by intracerebroventricular, intracortical, or supracortical atropine application decreased the occurrence of V1 spindle bursts by 50%, both the retina-independent and the optic nerve-mediated spindle bursts being affected. In contrast, blockade of acetylcholine esterase with physostigmine augmented the occurrence, amplitude, and duration of V1 spindle bursts. Whereas direct stimulation of the cholinergic basal forebrain nuclei increased the occurrence probability of V1 spindle bursts, their chronic immunotoxic lesion using 192 IgG-saporin decreased the occurrence of neonatal V1 oscillatory activity by 87%. Thus, the cholinergic input facilitates the neonatal V1 spindle bursts and may prime the developing cortex to operate specifically on relevant early (retinal waves) and later (visual input) stimuli.
The innervation of parvalbumin containing interneurons by VIP immunopositive interneurons in the primary somatosensory cortex of the adult rat.
David C, Schleicher A, Zuschratter W, Staiger JF.
Eur J Neurosci 25:2329-2340, 2007.
abstract link
Gamma-Aminobutyric acid (GABA)ergic interneurons of neocortex consist of many subgroups with extremely heterogeneous morphological, physiological and molecular properties. To explore the putative effect of the vasoactive intestinal polypeptide-immunopositive (VIP +) neurons on neocortical circuitry, the number and distribution of VIP + boutons were analysed on somatodendritic domains of 272 parvalbumin immunopositive (PV +) 3D-reconstructed neurons. The synaptic nature of 91% of somatic and 76% of dendritic contacts was verified by electron microscopy. The target PV + neurons were separated in two significantly different groups by means of cluster analysis. The first group (Cluster 1, 26%) received on average five times more VIP + synapses than those of the second group. The second group (Cluster 2, 74%) contained cells that were poorly innervated by VIP + boutons or did not have either somatic or dendritic or any VIP innervation at all. The cells of Cluster 1 had a soma size and total dendritic length significantly smaller than that of Cluster 2, however, they received three times more dendritic synapses, which resulted in a five times higher VIP + synaptic density on dendrites. Our results showed that although most of the PV + cells are innervated by VIP + boutons at a varying degree, some 6% of PV + cells received no input from VIP + interneurons. This suggests a refined morphological basis to influence the majority of the PV + interneurons, which are very effectively controlling pyramidal cell firing. Together with metabolic and neuromodulatory effects of VIP, this would probably result in an enhanced responsiveness of the latter cell type to tactile stimuli.
Mapping functional connectivity in barrel-related columns reveals layer- and cell type-specific microcircuits.
Schubert D, Kötter R, Staiger JF.
Brain Struct Funct 212: 107-119, 2007.
abstract link
Synaptic circuits bind together functional modules of the neocortex. We aim to clarify in a rodent model how intra- and transcolumnar microcircuits in the barrel cortex are laid out to segregate and also integrate sensory information. The primary somatosensory (barrel) cortex of rodents is the ideal model system to study these issues because there, the tactile information derived from the large facial whiskers on the snout is mapped onto so called barrel-related columns which altogether form an isomorphic map of the sensory periphery. This allows to functionally interpret the synaptic microcircuits we have been analyzing in barrel-related columns by means of whole-cell recordings, biocytin filling and mapping of intracortical functional connectivity with sublaminar specificity by computer-controlled flash-release of glutamate. We find that excitatory spiny neurons (spiny stellate, star pyramidal, and pyramidal cells) show a layer-specific connectivity pattern on top of which further cell type-specific circuits can be distinguished. The main features are: (a) strong intralaminar, intracolumnar connections are established by all types of excitatory neurons with both, excitatory and (except for layer Vb- intrinsically burst-spiking-pyramidal cells) inhibitory cells; (b) effective translaminar, intracolumnar connections become more abundant along the three main layer compartments of the canonical microcircuit, and (c) extensive transcolumnar connectivity is preferentially found in specific cell types in each of the layer compartments of a barrel-related column. These multiple sequential and parallel circuits are likely to be suitable for specific cortical processing of "what" "where" and "when" aspects of tactile information acquired by the whiskers on the snout.
Distinct expression and subcellular localization patterns of Na+/HCO3- cotransporter (SLC 4A4) variants NBCe1-A and NBCe1-B in mouse brain.
Rickmann M, Orlowski B, Heupel K, Roussa E.
Neuroscience. 146(3):1220-31, 2007.
abstract link
The electrogenic Na+/HCO3- cotransporter (NBCe1) has been identified as a key player for regulation of intracellular pH in several cell types. The present study was undertaken to determine expression and subcellular localization of the NH2-terminal solute carrier (SLC) 4A4 variants NBCe1-A and NBCe1-B in mouse brain using variant-specific antibodies by immunohistochemistry and immunoelectron microscopy. In addition, distribution of NBCe1 variants and activity-dependent regulation was investigated in mouse embryonic day 17.5 (E17.5) hippocampal primary cultures in vitro. The results showed NBCe1-A and NBCe1-B transcript expression in the mouse olfactory bulb, cerebral cortex, hippocampus and cerebellum. NBCe1-A was predominantly expressed in Purkinje cells, granule cells of the dentate gyrus, non-pyramidal cell bodies in cerebral cortex, and in periglomerular and mitral cells in the olfactory bulb. Pyramidal neurons in cerebral cortex and apical cell dendrites in the hippocampus were stained for both NBCe1-A and NBCe1-B. Moreover, NBCe1-B was present in Bergmann glia. At the ultrastructural level, NBCe1-B was preferentially expressed in perivascular astroglial lamellae, whereas both NBCe1 NH2-terminal variants were localized in pre- and postsynaptic compartments. Except for the olfactory bulb, NBCe1-A was always colocalized with calbindin. Treatment of E17.5 primary hippocampal cultures with KCl, showed dramatic downregulation of NBCe1-B mRNA and protein after 60 min, whereas NBCe1-A expression remained unchanged. These data demonstrate for the first time distinct cellular distribution of NBCe1 NH2-terminal variants in mouse brain. NBCe1 may be involved in neuronal modulation, and pH regulation during neuronal activity.
Conditional activation of Pax6 in the developing cortex of transgenic mice causes progenitor apoptosis.
Berger J, Berger S, Tuoc TC, D'Amelio M, Cecconi F, Gorski JA, Jones KR, Gruss P, Stoykova A.
Development, 2007.
134(7):1311-1322.
abstract link
During development, Pax6 is expressed in a rostrolateral-high to caudomedial-low gradient in the majority of the cortical radial glial progenitors and endows them with neurogenic properties. Using a Cre/loxP-based approach, we studied the effect of conditional activation of two Pax6 isoforms, Pax6 and Pax6-5a, on the corticogenesis of transgenic mice. We found that activation of either Pax6 or Pax6-5a inhibits progenitor proliferation in the developing cortex. Upon activation of transgenic Pax6, specific progenitor pools with distinct endogenous Pax6 expression levels at different developmental stages show defects in cell cycle progression and in the acquisition of apoptotic or neuronal cell fate. The results provide new evidence for the complex role of Pax6 in mammalian corticogenesis.
2006
Differential expression of active zone proteins in neuromuscular junctions suggests functional diversification.
Juranek J, Mukherjee K, Rickmann M, Martens H, Calka J, Südhof TC, Jahn R.
Eur J Neurosci. 24(11):3043-52, 2006.
abstract link
Nerve terminals of the central nervous system (CNS) contain specialized release sites for synaptic vesicles, referred to as active zones. They are characterized by electron-dense structures that are tightly associated with the presynaptic plasma membrane and organize vesicle docking and priming sites. Recently, major protein constituents of active zones have been identified, including the proteins Piccolo, Bassoon, RIM, Munc13, ERCs/ELKs/CASTs and liprins. While it is becoming apparent that each of these proteins is essential for synaptic function in the CNS, it is not known to what extent these proteins are involved in synaptic function of the peripheral nervous system. Somatic neuromuscular junctions contain morphologically and functionally defined active zones with similarities to CNS synapses. In contrast, sympathetic neuromuscular varicosities lack active zone-like morphological specializations. Using immunocytochemistry at the light and electron microscopic level we have now performed a systematic investigation of all five major classes of active zone proteins in peripheral neuromuscular junctions. Our results show that somatic neuromuscular endplates contain a full complement of all active zone proteins. In contrast, varicosities of the vas deferens contain a subset of active zone proteins including Bassoon and ELKS2, with the other four components being absent. We conclude that Bassoon and ELKS2 perform independent and specialized functions in synaptic transmission of autonomic synapses.
Immediate-early gene expression in the barrel cortex.
Staiger JF.
Somatosens Mot Res 23:135-146., 2006.
abstract link
Since their detection in the early 1980s immediate-early genes (most of them being inducible transcription factors) have been regarded as molecular keys to the orchestration of late-effector genes that ultimately would enable functional and structural adaptation of the brain to changing external and internal demands. This is called neuronal plasticity and it has been intensively studied in the somatosensory (barrel) cortex of rodents. This brain region is intimately involved in the processing and probably also the storage of tactile information, stemming from the large facial whiskers, necessary for object detection or spatial navigation in the environment. On the other hand, several of the inducible transcription factors have been found to function as neuronal activity markers providing a cellular resolution, thus, enabling the cell-type specific mapping of activated neuronal circuits. Some recent data on both topics in the rodent barrel cortex will be presented in this topical review.
Morphology, electrophysiology and functional input connectivity of pyramidal neurons characterizes a genuine layer Va in the primary somatosensory cortex.
Schubert D, Kötter R, Luhmann HJ, Staiger JF.
Cereb Cortex 16:223-236., 2006.
abstract link
Cortical layer V classically has been subdivided into sublayers Va and Vb on cytoarchitectonic grounds. In the analysis of cortical microcircuits, however, layer Va has largely been ignored. The purpose of this study was to investigate pyramidal neurons of layer Va in view of their potential role in integrating information from lemniscal and paralemniscal sources. For this we combined detailed electrophysiological and morphological characterization with mapping of intracortical functional connectivity by caged glutamate photolysis in layer Va of rat barrel cortex in vitro. Electrophysiological characterization revealed pyramidal cells of the regular spiking as well as the intrinsically burst firing type. However, all layer Va pyramidal neurons displayed uniform morphological properties and comparable functional input connectivity patterns. They received most of their excitatory and inhibitory inputs from intracolumnar sources, especially from layer Va itself, but also from layer IV. Those two layers were also the main origin for transcolumnar excitatory inputs. Layer Va pyramidal neurons thus may predominantly integrate information intralaminarly as well as from layer IV. The functional connectivity maps clearly distinguish layer Va from layer Vb pyramidal cells, and suggest that layer Va plays a unique role in intracortical processing of sensory information.
Functional unity of the ponto-cerebellum: evidence that intrapontine communication is mediated by a reciprocal loop with the cerebellar nuclei.
Möck M, Butovas S, Schwarz C.
J Neurophysiol. 95(6):3414-25, 2006.
abstract link
The majority of cerebral signals destined for the cerebellum are handed over by the pontine nuclei (PN), which thoroughly reorganize the neocortical topography. The PN maps neocortical signals of wide-spread origins into adjacent compartments delineated by spatially precise distribution of cortical terminals and postsynaptic dendrites. We asked whether and how signals interact on the level of the PN. Intracellular fillings of rat PN cells in vitro did not reveal any intrinsic axonal branching neither within the range of the cells' dendrites nor farther away. Furthermore, double whole cell patch recordings did not show any signs of interaction between neighboring pontine cells. Using simultaneous unit recording in the PN and cerebellar nuclei (CN) in rats in vivo, we investigated whether PN compartments interact via extrinsic reciprocal connections with the CN. Repetitive electrical stimulation of the cerebral peduncle of < or = 40 Hz readily evoked rapid sequential activation of PN and CN, demonstrating a direct connection between the structures. Stimulation of the PN gray matter led to responses in neurons < or = 600 microm away from the stimulation site at latencies compatible with di- or polysynaptic pathways via the CN. Importantly, these interactions were spatially discontinuous around the stimulation electrode suggesting that reciprocal PN-CN loops in addition reflect the compartmentalized organization of the PN. These findings are in line with the idea that the cerebellum makes use of the compartmentalized map in the PN to orchestrate the composition of its own neocortical input.
The oculomotor role of the pontine nuclei and the nucleus reticularis tegmenti pontis.
Thier P, Möck M.
Prog Brain Res. 151:293-320, 2006.
abstract link
Cerebral cortex and the cerebellum interact closely in order to facilitate spatial orientation and the generation of motor behavior, including eye movements. This interaction is based on a massive projection system that allows the exchange of signals between the two cortices. This cerebro-cerebellar communication system includes several intercalated brain stem nuclei, whose eminent role in the organization of oculomotor behavior has only recently become apparent. This review focuses on the two major nuclei of this group taking a precerebellar position, the pontine nuclei and the nucleus reticularis tegmenti pontis, both intimately involved in the visual guidance of eye movements.
Na(+)/H(+) exchanger isoforms are differentially regulated in rat submandibular gland during acid/base disturbances in vivo.
Oehlke O, Sprysch P, Rickmann M, Roussa E.
Cell Tissue Res. 323(2):253-62, 2006.
abstract link
Acute metabolic acidosis and alkalosis cause a series of homeostatic adaptive responses in the kidney and other epithelia. We hypothesized that acid/base disturbances might affect the expression of Na(+)/H(+) exchanger (NHE) isoforms in salivary glands and determined the expression and cellular distribution of NHE3 and NHE4 in rat submandibular glands of controls and after imposed acute or chronic metabolic acidosis or alkalosis in vivo. Reverse transcription/polymerase chain reaction, in situ hybridization, and immunohistochemistry were applied by using specific primers, antisense probes, and antibodies, respectively. The results showed NHE3 and NHE4 transcript expression and protein abundance in rat submandibular gland. NHE3 was apically localized in duct cells, whereas NHE4 was found basolaterally distributed in acinar and duct cells. Acute acidosis and alkalosis and chronic acidosis had no effect on NHE3 and NHE4 expression and localization. In contrast, chronic metabolic alkalosis significantly decreased the number of apically stained NHE3 duct cells but had no effect on NHE3 mRNA expression. The results demonstrate, for the first time, the presence of NHE4 protein in salivary glands. The data also indicate the distinct regulation and adaptive changes of different isoforms of the same transporter in rat submandibular gland as a response to acid/base disturbances.
2005
Optical release of caged glutamate for stimulation of neurons in the in vitro slice preparation.
Kötter R, Schubert D, Dyhrfjeld-Johnsen J, Luhmann HJ, Staiger JF.
J Biomed Optics 10: 1-15., 2005.
abstract link
Optical stimulation techniques prove useful to map functional inputs in the in vitro brain slice preparation: Glutamate released by a focused beam of UV light induces action potentials, which can be detected in postsynaptic neurons. The direct activation effect is influenced by factors such as compound concentration, focus depth, light absorption in the tissue, and sensitivity of different neuronal domains. We analyze information derived from direct stimulation experiments in slices from rat barrel cortex and construct a computational model of a layer V pyramidal neuron that reproduces the experimental findings. The model predictions concerning the influence of focus depth on input maps and action potential generation are investigated further in subsequent experiments where the focus depth of a high-numerical-aperture lens is systematically varied. With our setup flashes from a xenon light source can activate neuronal compartments to a depth of 200 mum below the surface of the slice. The response amplitude is influenced both by tissue depth and focus plane. Specific somatodendritic structures can be targeted as the probability of action potential induction falls off exponentially with distance. Somata and primary apical dendrites are most sensitive to uncaged glutamate with locally increased sensitivity on proximal apical dendrites. We conclude that optical stimulation can be targeted with high precision.
CoCoDat: a database system for organizing and selecting quantitative data on single neurons and neuronal microcircuitry.
Dyhrfjeld-Johnsen J, Maier J, Schubert D, Staiger JF, Luhmann HJ, Stephan KE, Kötter R.
J Neurosci Methods 141:291-308., 2005.
abstract link
We present a novel database system for organizing and selecting quantitative experimental data on single neurons and neuronal microcircuitry that has proven useful for reference-keeping, experimental planning and computational modelling. Building on our previous experience with large neuroscientific databases, the system takes into account the diversity and method-dependence of single cell and microcircuitry data and provides tools for entering and retrieving published data without a priori interpretation or summarizing. Data representation is based on the framework suggested by biophysical theory and enables flexible combinations of data on membrane conductances, ionic and synaptic currents, morphology, connectivity and firing patterns. Innovative tools have been implemented for data retrieval with optional relaxation of search criteria along the conceptual dimensions of brain region, cortical layer, cell type and subcellular compartment. The relaxation procedures help to overcome the traditional trade-off between exact, non-interpreted data representation in the original nomenclature and convenient data retrieval. We demonstrate the use of these tools for the construction, tuning and validation of a multicompartmental model of a layer V pyramidal cell from the rat barrel cortex. CoCoDat is freely available at . Its application is scalable from offline use by individual researchers via local laboratory networks to a federation of distributed web sites in platform-independent XML format using Axiope tools.
Organization of tectopontine terminals within the pontine nuclei of the rat and their spatial relationship to terminals from the visual and somatosensory cortex.
Schwarz C, Horowski A, Möck M, Thier P.
J Comp Neurol. 484(3):283-98, 2005.
abstract link
We investigated the spatial relationship of axonal and dendritic structures in the rat pontine nuclei (PN), which transfer visual signals from the superior colliculus (SC) and visual cortex (A17) to the cerebellum. Double anterograde tracing (DiI and DiAsp) from different sites in the SC showed that the tectal retinotopy of visual signals is largely lost in the PN. Whereas axon terminals from lateral sites in the SC were confined to a single terminal field close to the cerebral peduncle, medial sites in the SC projected to an additional dorsolateral one. On the other hand, axon terminals originating from the two structures occupy close but, nevertheless, totally nonoverlapping terminal fields within the PN. Furthermore, a quantitative analysis of the dendritic trees of intracellularly filled identified pontine projection neurons showed that the dendritic fields were confined to either the SC or the A17 terminal fields and never extended into both. We also investigated the projections carrying cortical somatosensory inputs to the PN as these signals are known to converge with tectal ones in the cerebellum. However, terminals originating in the whisker representation of the primary somatosensory cortex and in the SC were located in segregated pontine compartments as well. Our results, therefore, point to a possible pontocerebellar mapping rule: Functionally related signals, commonly destined for common cerebellar target zones but residing in different afferent locations, may be kept segregated on the level of the PN and converge only later at specific sites in the granular layer of cerebellar cortex.
2004
Mutation in the gene encoding lysosomal acid phosphatase (Acp2) causes cerebellum and skin malformation in mouse.
Mannan AU, Roussa E, Kraus C, Rickmann M, Maenner J, Nayernia K, Krieglstein K, Reis A, Engel W.
Neurogenetics. 5(4):229-38, 2004.
abstract link
We report a novel spontaneous mutation named nax in mice, which exhibit delayed hair appearance and ataxia in a homozygote state. Histological analyses of nax brain revealed an overall impairment of the cerebellar cortex. The classical cortical cytoarchitecture was disrupted, the inner granule cell layer was not obvious, the Purkinje cells were not aligned as a Purkinje cell layer, and Bergmann glias did not span the molecular layer. Furthermore, histological analyses of skin showed that the hair follicles were also abnormal. We mapped the nax locus between marker D2Mit158 and D2Mit100 within a region of 800 kb in the middle of chromosome 2 and identified a missense mutation (Gly244Glu) in Acp2, a lysosomal monoesterase. The Glu244 mutation does not affect the stability of the Acp2 transcript, however it renders the enzyme inactive. Ultrastructural analysis of nax cerebellum showed lysosomal storage bodies in nucleated cells, suggesting progressive degeneration as the underlying mechanism. Identification of Acp2 as the gene mutated in nax mice provides a valuable model system for studying the role of Acp2 in cerebellum and skin homeostasis.
Calbindin-containing interneurons are a target for VIP-immunoreactive synapses in rat primary somatosensory cortex.
Staiger JF, Masanneck C, Schleicher A, Zuschratter W.
J Comp Neurol 468: 179-189., 2004.
abstract link
Inhibitory interneurons in cerebral cortex are morphologically and physiologically extremely heterogeneous. This greatly interferes with an understanding of their functions. Progress has been made by classifying these neurons with the aid of molecular markers, e.g., neuropeptides or calcium-binding proteins, which are reliably expressed by certain subpopulations. We have used this approach to demonstrate an output of a subpopulation of cortical interneurons which express vasoactive intestinal polypeptide (VIP). By double immunostaining and correlated light and electron microscopy, we show that calbindin (CB)-containing interneurons located in layers II-VI of rat barrel cortex are targets of symmetric VIP-immunoreactive synapses. All CB-immunoreactive interneurons showed numerous contacts of VIP boutons on proximal and distal dendritic segments. A great majority of CB-immunoreactive interneurons (214/222) displayed such close appositions with VIP boutons on their soma as well. Quantification revealed that the number of VIP-immunoreactive boutons on CB-immunoreactive somata and dendrites of specified order is comparable for the different cortical layers. In conclusion, all calbindin-containing cortical interneurons seem to be under direct influence of other GABAergic interneurons expressing the peptide VIP. An indirect functional consequence of this may be disinhibition of pyramidal cells, which are considered the major target of calbindin interneurons. However, since the examined types of interneurons are intricately embedded in networks of yet different interneurons, the outcome of these multiple inhibitory interactions is likely to be less simplistic. It may be related to the timing of pyramidal cell discharge within and across layers of cortical columns.
Functional diversity of layer IV spiny neurons in rat somatosensory cortex: quantitative morphology of electrophysiologically characterized and biocytin labeled cells.
Staiger JF, Flagmeyer I, Schubert D, Zilles K, Kötter R, Luhmann HJ.
Cereb Cortex 14: 690-701., 2004.
abstract link
Previous analyses of the spiny layer IV neurons have almost exclusively focused on spiny stellate cells. Here we provide detailed morphological data characterizing three subpopulations of spiny neurons in slices of adolescent rats: (i) spiny stellate cells (58%), (ii) star pyramidal cells (25%) and (iii) pyramidal cells (17%), which can be distinguished objectively by the preferential orientation of their dendritic stems. Spiny stellate cells lacked an apical dendrite and frequently confined their dendritic and axonal arbors to the respective column. Star pyramidal and pyramidal cells possessed an apical dendrite, which reached the supragranular layers. Their axonal arbors were similar, showing both a columnar component and transcolumnar branches with direct transbarrel projections. However, a small fraction of star pyramidal cells possessed few or even no transcolumnar branches. Electrophysiologically, all three types of neurons were either regular-spiking or intrinsically burst-spiking without a significant relation to the morphological subtypes. The basic synaptic properties of thalamic inputs were also independent of the type of target layer IV spiny neuron. All remained subthreshold and showed paired-pulse depression. In conclusion, the columnar axonal arborization of spiny stellate cells is supplemented by a significant oblique to horizontal projection pattern in pyramidal-like neurons. This offers a structural basis for either segregation or early context-dependent integration of tactile information, in a cell-type specific manner.
2003
Distinct local circuits between neocortical pyramidal cells and fast-spiking interneurons in young adult rats.
Angulo MC, Staiger JF, Rossier J, Audinat A.
J Neurophysiol 89: 943-953., 2003.
abstract link
Connections between layer V pyramidal cells and GABAergic fast-spiking interneurons (pyramidal-FS) were studied by paired recordings combined with morphological analyses in acute neocortical slices from 28- to 52-day-old rats. Pairs of spikes elicited in pyramidal cells at a stimulation rate of 0.2 Hz induced unitary excitatory postsynaptic currents (EPSCs) in FS interneurons that displayed facilitation (48%), depression (38.5%), or neither depression nor facilitation (13.5%). Analyses of the EPSC amplitude distributions indicate that depressing connections always showed multiple functional release sites. On the contrary, facilitating connections consisted either of one or several release sites. At a holding potential of -72 mV, the quantal size (q) and the release probability (p) of facilitating connections with a single release site were -21.9 +/- 7.5 pA and 0.49 +/- 0.19 (SD), respectively. The mean q and the estimated number of release sites (n) at connections showing multiple sites were obtained by decreasing the release probability and did not differ between depressing and facilitating synapses (depressing connections: q = -15.3 +/- 2.5 pA, n = 5.1 +/- 3, facilitating connections: q = -23.9 +/- 9.8 pA, n = 7.8 +/- 5.4). However, the quantal content at facilitating synapses with multiple sites (1.9 +/- 1.5) was significantly different from that at depressing connections (4.1 +/- 3.9). Finally, quantitative morphological analyses revealed that most of the pyramidal cells displaying facilitation can be differentiated from those displaying depression by a more densely branched apical dendritic tree. Therefore two types of morphologically distinct pyramidal cells form excitatory connections with FS interneurons that differ in their short-term plasticity characteristics. Facilitating and depressing connections may provide a differential control of the temporal information processing of FS cells and thus finely regulate the inhibitory effect of these interneurons in neocortical networks of young adult rats.
Cell type-specific circuitry of cortical layer IV spiny neurons.
Schubert D, Kötter R, Zilles K, Luhmann HJ, Staiger JF.
J Neurosci 23: 2961-2970., 2003.
abstract link
Sensory signal processing in cortical layer IV involves two major morphological classes of excitatory neurons: spiny stellate and pyramidal cells. It is essentially unknown how these two cell types are integrated into intracortical networks and whether they play different roles in cortical signal processing. We mapped their cell-specific intracortical afferents in rat somatosensory cortex through a combination of whole-cell patch-clamp recordings and caged glutamate photolysis. Spiny stellate cells received monosynaptic excitation and inhibition originating almost exclusively from neurons located within the same barrel. Pyramidal cells, by contrast, displayed additional excitatory inputs from nongranular layers and from neighboring barrels. Their inhibitory inputs originated, as for spiny stellate cells, mainly from neurons located in the same barrel. These results indicate that spiny stellate cells act predominantly as local signal processors within a single barrel, whereas pyramidal cells globally integrate horizontal and top-down information within a functional column and between neighboring barrels.
2002
Disruption of PLC-beta 1-mediated signal transduction in mutant mice causes age-dependent hippocampal mossy fiber sprouting and neurodegeneration.
Böhm D, Schwegler H, Kotthaus L, Nayernia K, Rickmann M, Köhler M, Rosenbusch J, Engel W, Flügge G, Burfeind P.
Mol Cell Neurosci. 21(4):584-601, 2002.
abstract link
Aberrant reorganization of hippocampal mossy fibers occurs in human temporal lobe epilepsy and rodent epilepsy models. We generated a mouse model showing massive late-onset aberrant mossy fiber sprouting in the adult hippocampus. The mutation in this mouse model derives from an intronic insertion of transgene DNA in the mouse PLC-beta1 gene (PLC-beta 1(-/-)(TC) mutation) leading to a splice mutation of the PLC-beta 1 gene and a complete loss of downstream PLC-beta 1 expression. PLC-beta 1(-/-)(TC) mutants develop a loss of NMDA-receptors in the stratum oriens of region CA1, apoptotic neuronal death, and reduced hippocampal PKC activity. The phenotype of these mice further consists of a late-onset epileptiform hyperexcitability, behavioral modifications in a radial maze and in an open field, female nurturing defect, and male infertility. In the present study, we provide evidence that the arising of the behavioral phenotype in PLC-beta 1(-/-)(TC) mice correlates in time with the development of the aberrant mossy fiber projections and that the disruption of the PLC-beta 1-mediated signal transduction pathway may lead to a functional cholinergic denervation, which could cause hippocampal remodeling and, in consequence, epileptiform hyperexcitability.
Excitatory and inhibitory neurons express c-Fos in barrel-related columns after exploration of a novel environment.
Staiger JF, Masanneck C, Bisler S, Zuschratter W, Zilles K.
Neuroscience 109: 687-699., 2002.
abstract link
Recent work has shown that behaviorally meaningful sensory information processing is accompanied by the induction of several transcription factors in the barrel cortex of rodents. It is now generally accepted that stimulus-transcription coupling is an important step in the sequence of events leading to long-term plastic changes in neuronal structure and function. Nevertheless, so far few data are available as to what types of neurons are involved in such a genomic response. Here, we determined the morphological and neurochemical identity of neurons in rat barrel cortex showing a c-Fos-immunoreactive nucleus after exploration of an enriched environment. Double stainings of c-Fos and glial fibrillary acidic protein excluded astrocytes as a possible cell type expressing this transcription factor. By morphological phenotyping with intracellular Lucifer Yellow injections, it was found that a large majority were probably excitatory pyramidal cells, but inhibitory interneurons were also found to contain c-Fos-immunoreactive nuclei. By neurochemical phenotyping of GABAergic interneurons with specific antibodies, a significant induction was found, in a layer-dependent manner, for the populations of glutamic acid decarboxylase-, parvalbumin-, calbindin- and vasoactive intestinal polypeptide-immunoreactive neurons but not for calretinin-immunoreactive cells in experimental compared to control columns. From these data we conclude that thalamic afferents effectively drive cortical excitatory as well as inhibitory intracortical circuits. Thus, the adaptations of receptive field properties of cortical neurons after different manipulations of the sensory periphery are likely to be caused by plastic changes in excitatory and inhibitory networks.
Expression of Fos, ICER, Krox-24 and JunB in the whisker-to-barrel-pathway of rats: time course of induction upon whisker-pairing and exploration of an enriched environment.
Bisler S, Schleicher A, Gass P, Stehle JH, Zilles K, Staiger JF.
J Chem Neuroanat 23: 187-198., 2002.
Innervation of interneurons immunoreactive for VIP by intrinsically bursting pyramidal cells and fast-spiking interneurons in infragranular layers of juvenile rat neocortex.
Staiger JF, Schubert D, Zuschratter W, Kötter R, Luhmann HJ, Zilles K.
Eur J Neurosci 16: 11-20., 2002.
Two types of nicotinic receptors mediate an excitation of neocortical layer I interneurons.
Christophe E, Roebuck A, Staiger JF, Lavery DJ, Charpak S, Audinat E.
J Neurophysiol 88: 1318-1327., 2002.
Quantitative organization of neurotransmitters in the deep cerebellar nuclei of the Lurcher mutant.
Sultan F, König T, Möck M, Thier P.
J Comp Neurol. 452(4):311-23, 2002.
abstract link
The Lurcher mutant mouse is characterized by a primary selective loss of Purkinje cells, leading to the near total apoptotic death of these neurons. In contrast to the subsequent massive secondary degeneration of the granule cells and the inferior olivary neurons, only mild degeneration occurs in the deep cerebellar nuclei (DCN). However, it is not known to what extent the different populations of DCN neurons-glutamatergic principal projection neurons, gamma-aminobutyric acid (GABA)-ergic inferior olivary projection neurons, and glycinergic neurons-are affected in their neurotransmitter composition. To answer this question we studied the neurotransmitter contents (glutamate, GABA, and glycine) of DCN neurons and the size of synaptic boutons immunohistochemically on serial semithin sections in both Lurcher and wild-type mice. Applying the physical dissector counting method, our results confirmed the mild degeneration (a reduction by 20%) of large glutamatergic neurons and a more pronounced degeneration of GABAergic (by 42%) and glycinergic neurons (by 45%). On the other hand, an analysis of neurons colabeled for both GABA and glycine, revealed that this specific colabeling increased in the Lurcher mutant (by 40%). In addition, both the GABA-immunolabeled (IL) (by 56%) and the glycine-IL (by 45%) synaptic boutons showed an increase in diameter in the mutant. The density of these boutons showed a decrease of 30% each. In summary, the increase in the number of neurons colabeled for GABA and glycine, together with the increase in the size of the inhibitory synaptic boutons, could help in providing the minimum inhibition needed to maintain a residual "cerebellar" functionality in the Lurcher DCN.
Serotonergic control of cerebellar mossy fiber activity by modulation of signal transfer by rat pontine nuclei neurons.
Möck M, Schwarz C, Thier P.
J Neurophysiol. 88(2):549-64, 2002.
abstract link
Serotonergic modulation of precerebellar nuclei may be crucial for the function of the entire cerebellar system. To study the effects of serotonin (5-HT) on neurons located within the pontine nuclei (PN), the main source of cerebellar mossy fibers, we performed standard intracellular recordings from PN neurons in a slice preparation of the rat pontine brain stem. Application of 5 microM 5-HT significantly altered several intrinsic membrane properties of PN neurons. First, it depolarized the somatic membrane potential by 6.5 +/- 3.5 mV and increased the apparent input resistance from 49.5 +/- 14.6 to 62.7 +/- 21.1 MOmega. Second, 5-HT altered the I-V relationship of PN neurons: it decreased the inward rectification in hyperpolarizing direction, but increased it when depolarizing currents were applied. Third, it decreased the rheobase from 0.32 +/- 0.14 to 0.24 +/- 0.14 nA without affecting the firing threshold. Finally, the amplitude of medium-duration after hyperpolarizations was reduced from -14.9 +/- 2.0 to -12.3 +/- 2.4 mV. Together, these 5-HT effects on the intrinsic membrane properties result in an increase in excitability and instantaneous firing rate. In addition, application of 5 microM 5-HT also modulated postsynaptic potentials (PSPs) evoked by electric stimulations within the cerebral peduncle. The amplitude, maximal slope, and integral of these PSPs were reduced to 46.2 +/- 23.4%, 45.7 +/- 23.7%, and 61.4 +/- 28.4% of the control value, respectively. In contrast, we found no change in the decay and voltage dependence of PSPs. To test modulatory effects on short-term synaptic facilitation, we applied pairs of electrical stimuli at intervals between 10 and 1,000 ms. 5-HT selectively enhanced the paired-pulse facilitation for interstimulus-intervals >20 ms. The alteration of paired-pulse facilitation points to a presynaptic site of action for 5-HT effects on synaptic transmission. Pharmacological experiments suggested that pre- and postsynaptic effects of 5-HT were mediated by two different kinds of 5-HT receptors: changes in intrinsic membrane properties were blocked by the 5-HT(2) receptor antagonist cinanserin while the reduction of PSPs was prevented by the 5-HT(1) receptor antagonist cyanopindolol. In conclusion, 5-HT increases the excitability of PN neurons but decreases the synaptic transmission on them. The selective enhancement of synaptic facilitation may, however, allow high-frequency inputs to effectively drive PN neurons, thus the PN may act as a high-pass filter during periods of 5-HT release.
2001
Kainate receptors regulate unitary IPSCs elicited in pyramidal cells by fast-spiking interneurons in the neocortex.
Ali AB, Rossier J, Staiger JF, Audinat E.
J Neurosci 21: 2992-2999., 2001.
Layer-specific intracolumnar and transcolumnar functional connectivity of layer V pyramidal cells in rat barrel cortex.
Schubert D, Staiger JF, Cho N, Kötter R, Zilles K, Luhmann HJ.
J Neurosci 21: 3580-3592., 2001.
Spatial arrangement of cerebro-pontine terminals.
Schwarz C, Möck M.
J Comp Neurol. 435(4):418-32, 2001.
abstract link
Understanding the interaction of the cerebral cortex and cerebellum requires knowledge of the highly complex spatial characteristics of cerebro-cerebellar signal transfer. Cerebro-pontine fibers from one neocortical site terminate in several sharply demarcated patches across large parts of the pontine nuclei (PN), and fibers from different neocortical areas terminate in the same pontine region. To determine whether projections from segregated neocortical sites overlap in the PN, we studied double anterograde tracing of cerebro-pontine terminals from large parts of rat neocortex. In none of these experiments, including double injection into two functionally related areas, were we able to demonstrate overlapping patches, although close spatial relationships were always detected. This non-overlapping distribution is consistent with a compartmentalized organization of the cerebro-pontine projection and may be the basis of the fractured type of maps found in the cerebellar granular layer. The critical distance between two sites on the neocortical surface that project to non-overlapping patches in the PN was found to be 600 microm, by using double injection within the whisker representation of the primary somatosensory area. This matches the diameter of dendritic trees of layer 5 projection neurons, indicating that non-overlapping populations of neocortical projection neurons possess non-overlapping patches of pontine terminals. Estimations based on this critical distance and the pontine volume anterogradely labeled by one injection site indicate that the size of the PN may be well suited to accommodate a complete set of non-overlapping pontine patches from all possible neocortical sites.
The cerebellum-specific Munc13 isoform Munc13-3 regulates cerebellar synaptic transmission and motor learning in mice.
Augustin I, Korte S, Rickmann M, Kretzschmar HA, Südhof TC, Herms JW, Brose N.
J Neurosci. 21(1):10-7, 2001.
abstract link
Munc13 proteins form a family of three, primarily brain-specific phorbol ester receptors (Munc13-1/2/3) in mammals. Munc13-1 is a component of presynaptic active zones in which it acts as an essential synaptic vesicle priming protein. In contrast to Munc13-1, which is present in most neurons throughout the rat and mouse CNS, Munc13-3 is almost exclusively expressed in the cerebellum. Munc13-3 mRNA is present in granule and Purkinje cells but absent from glia cells. Munc13-3 protein is localized to the synaptic neuropil of the cerebellar molecular layer but is not found in Purkinje cell dendrites, suggesting that Munc13-3, like Munc13-1, is a presynaptic protein at parallel fiber-Purkinje cell synapses. To examine the role of Munc13-3 in cerebellar physiology, we generated Munc13-3-deficient mutant mice. Munc13-3 deletion mutants exhibit increased paired-pulse facilitation at parallel fiber-Purkinje cell synapses. In addition, mutant mice display normal spontaneous motor activity but have an impaired ability to learn complex motor tasks. Our data demonstrate that Munc13-3 regulates synaptic transmission at parallel fiber-Purkinje cell synapses. We propose that Munc13-3 acts at a similar step of the synaptic vesicle cycle as does Munc13-1, albeit with less efficiency. In view of the present data and the well established vesicle priming function of Munc13-1, it is likely that Munc13-3-loss leads to a reduction in release probability at parallel fiber-Purkinje cell synapses by interfering with vesicle priming. This, in turn, would lead to increases in paired-pulse facilitation and could contribute to the observed deficit in motor learning.
2000
Neurons immunoreactive for vasoactive intestinal polypeptide in the rat primary somatosensory cortex: morphology and spatial relationship to barrel-related columns.
Bayraktar T, Welker E, Freund TF, Zilles K, Staiger JF.
J Comp Neurol 420: 291-304., 2000.
Exploration of a novel environment leads to the expression of inducible transcription factors in barrel-related columns.
Staiger JF, Bisler S, Schleicher A, Gass P, Stehle JH, Zilles K.
Neuroscience 99: 7-16., 2000.
abstract link
Tactile information acquired through the vibrissae is of high behavioral relevance for rodents. Numerous physiological studies have shown adaptive plasticity of cortical receptive field properties due to stimulation and/or manipulation of the whiskers. However, the cellular mechanisms leading to these plastic processes remain largely unknown. Although genomic responses are anticipated to take place in this sequel, virtually no data so far exist for freely behaving animals concerning this issue. Thus, adult rats were placed overnight in an enriched environment and most of them were also subjected to clipping of different sets of whiskers. This type of stimulation led to a specific and statistically significant increase in the expression of the protein products of the inducible transcription factors c-Fos, JunB, inducible cyclic-AMP early repressor and Krox-24 (also frequently named Zif268 or Egr-1), but not c-Jun. The response was found in columns of the barrel cortex corresponding to the stimulated vibrissae; it displayed a layer-specific pattern. However, no induction of transcription factors was observed in the subcortical relay stations of the whisker-to-barrel pathway, i.e. the trigeminal nuclei and the ventrobasal complex. These results strongly suggest that a coordinated transcriptional response is initiated in the barrel cortex as a consequence of processing of novel environmental stimuli.
Laminar characteristics of functional connectivity in rat barrel cortex revealed by stimulation with caged-glutamate.
Staiger JF, Kötter R, Zilles K, Luhmann HJ.
Neurosci Res 37: 49-58., 2000.
1999
Developmental synaptic changes increase the range of integrative capabilities of an identified excitatory neocortical connection.
Angulo MC, Staiger JF, Rossier J, Audinat E.
J Neurosci 19: 1566-1576., 1999.
Cellular morphology and physiology of the perinatal rat cerebral cortex.
Luhmann HJ, Schubert D, Kötter R, Staiger JF.
Dev Neurosci 21: 298-309., 1999.
Enlargement of cortical vibrissa representation in the surround of an ischemic cortical lesion.
Schiene K, Staiger JF, Bruehl C, Witte OW.
J Neurol Sci 162: 6-13. , 1999.
Connectivity in the somatosensory cortex of the adolescent rat: an in vitro biocytin study.
Staiger JF, Kötter R, Zilles K, Luhmann HJ.
Anat Embryol 199: 357-365. , 1999.
GABAergic inhibition in the rat pontine nuclei is exclusively extrinsic: evidence from an in situ hybridization study for GAD67 mRNA.
Möck M, Schwarz C, Wahle P, Thier P.
Exp Brain Res. 124(4):529-32, 1999.
abstract link
As clearly indicated by our electrophysiological work, GABAergic inhibition plays a powerful role in the pontine nuclei (PN), the major link between cerebral cortex and the cerebellum. Using the technique of in situ hybridization for the mRNA encoding for the gamma-aminobutyric acid (GABA)-synthesizing isoenzyme glutamic acid decarboxylase67 (GAD67), we demonstrate here the total absence of potentially GABAergic neurons from the rat PN. This negative finding supports the notion that GABAergic inhibition in the PN of rats, unlike that of higher mammals, is exclusively based on extrapontine GABAergic afferents.
1998
Disturbance of the cortical cholinergic innervation in Borna disease prior to encephalitis.
Gies U, Bilzer T, Stitz L, Staiger JF.
Brain Pathol 8: 39-48., 1998.
Analysing functional connectivity in brain slices by a combination of infrared video microscopy, flash photolysis of caged compounds and scanning methods.
Kötter R, Staiger JF, Zilles K, Luhmann HJ.
Neuroscience 86: 265-277., 1998.
Immunohistochemical evidence for dysregulation of the GABAergic system ipsilateral to photochemically induced cortical infarcts in rats.
Neumann-Haefelin T, Staiger JF, Redecker C, Zilles K, Fritschy JM, Mohler H, Witte OW.
Neuroscience 87: 871-879., 1998.
Unsolved problems in comparing brain sizes in Homo sapiens.
Peters M, Jäncke L, Staiger JF, Schlaug G, Huang Y, Steinmetz H.
Brain and Cognition 37: 254-285., 1998.
Properties of bipolar VIPergic interneurons and their excitation by pyramidal neurons in the rat neocortex.
Porter JT, Cauli B, Staiger JF, Lambolez B, Rossier J, Audinat E.
Eur J Neurosci 10: 3617-3628., 1998.
1997
Co-localization of vasoactive intestinal polypeptide, gamma-aminobutyric acid and choline acetyltransferase in neocortical interneurons of the adult rat.
Bayraktar T, Staiger JF, Acsady L, Cozzari C, Freund TF, Zilles K.
Brain Res 757: 209-217., 1997.
Geniculo-cortical afferents form synaptic contacts with vasoactive intestinal polypeptide (VIP) immunoreactive neurons of the rat visual cortex.
Hajos F, Staiger JF, Halasy K, Freund TF, Zilles K.
Neurosci Lett 228: 179-182., 1997.
The relationship between corpus callosum size and forebrain volume.
Jäncke L, Staiger JF, Schlaug G, Huang YX, Steinmetz H.
Cereb Cortex 7: 48-56., 1997.
Interneurons immunoreactive for vasoactive intestinal polypeptide (VIP) are extensively innervated by parvalbumin-containing boutons in rat primary somatosensory cortex.
Staiger JF, Freund TF, Zilles K.
Eur J Neurosci 9: 2259-2268., 1997.
Electrophysiological properties of rat pontine nuclei neurons In vitro II. Postsynaptic potentials.
Möck M, Schwarz C, Thier P.
J Neurophysiol. 78(6):3338-50, 1997.
abstract link
We investigated the postsynaptic responses of neurons of the rat pontine nuclei (PN) by performing intracellular recordings in parasagittal slices of the pontine brain stem. Postsynaptic potentials (PSPs) were evoked by brief (0.1 ms) negative current pulses (10-250 microA) applied to either the cerebral peduncle or the pontine tegmentum. First, excitatory postsynaptic potentials (EPSPs) could be evoked readily from peduncular stimulation sites. These EPSPs exhibited short latencies, a nonlinear increment in response to increased stimulation currents, and an unconventional dependency on the somatic membrane potential. Pharmacological blockade of the synaptic transmission using 6,7-dinitroquinoxaline-2, 3-dione and ,-2-amino-5-phosphonovaleric acid, selective antagonists of the alpha-amino-3-hydroxy-5-methyl-4-isoxazilepropionate- (AMPA) and the N-methyl--aspartate (NMDA)-type glutamate receptors, showed that these EPSPs were mediated exclusively by excitatory amino acids via both AMPA and NMDA receptors. Moreover, the pharmacological experiments indicated the existence of voltage-sensitive but NMDA receptor-independent amplification of EPSPs. Second, stimulations at peduncular and tegmental sites also elicited inhibitory postsynaptic potentials (IPSPs) in a substantial proportion of pontine neurons. The short latencies of all IPSPs argued against the participation of inhibitory interneurons. Their sensitivity to bicuculline and reversal potentials around -70 mV suggested that they were mediated by gamma-aminobutyric acid-A (GABAA) receptors. In addition to single PSPs, sequences consisting of two to four distinct EPSPs could be recorded after stimulation of the cerebral peduncle. Most remarkably, the onset latencies of the following EPSPs were multiples of the first one indicating the involvement of intercalated synapses. Finally, we used the classic paired-pulse paradigm to study whether the temporal structure of inputs influences the synaptic transmission onto pontine neurons. Pairs of electrical stimuli applied to the cerebral peduncle resulted in a marked enhancement of the amplitude of the second EPSP for interstimulus intervals of 10-100 ms. Delays >200 ms left the EPSP amplitude unaltered. These data provide evidence for a complex synaptic integration and an intrinsic connectivity within the PN too elaborate to support the previous notion that the PN are simply a relay station.
Electrophysiological properties of rat pontine nuclei neurons In vitro. I. Membrane potentials and firing patterns.
Schwarz C, Möck M, Thier P.
J Neurophysiol. 78(6):3323-37, 1997.
abstract link
We used a new slice preparation of rat brain stem to establish the basic membrane properties of neurons in the pontine nuclei (PN). Using standard intracellular recordings, we found that pontine cells displayed a resting membrane potential of -63 +/- 6 mV (mean +/- SD), an input resistance of 53 +/- 21 MOmega, a membrane time constant of 5.3 +/- 2.4 ms and were not spontaneously active. The current-voltage relationship of most of the PN neurons showed the characteristics of inward rectification in both depolarizing and hyperpolarizing directions. A prominent feature of the firing of pontine neurons was a marked firing rate adaptation, which eventually caused the cells to cease firing. Several types of membrane conductances possibly contribute to this feature. For one, a medium and a slow type of afterhyperpolarization (AHP) control the pattern of firing. The medium AHP was partly susceptible to blockade of calcium influx, whereas it was abolished completely by blockade of potassium channels with tetraethylammonium, indicating that it is based on at least two conductances: a calcium-dependent and a calcium-independent one. The slow AHP was carried by potassium ions and could be blocked effectively by preventing calcium influx into the cell. It was present after single spikes but was strongest after a high-frequency spike train. Calcium entry into the cell was mediated by high-threshold calcium channels that were detected by the generation of calcium spikes under blockade of potassium channels. Furthermore, the early phase of the firing rate adaptation was shown to be related to the time course of a slow, tetrodotoxin (TTX)-sensitive, persistent sodium potential, which was activated already in the subthreshold range of membrane potentials. This potential was time dependent and imposed as a depolarizing "hump" with a maximum occurring in most cases between 50 and 100 ms after stimulus onset. In the suprathreshold range, it generated plateau potentials following fast spikes, if potassium channels were blocked. After the complete adaptation of the firing rate, PN neurons were observed to display irregular fluctuations of the membrane potential, which sometimes reached firing threshold thereby eliciting an irregular low-frequency spike train. As these fluctuations could be blocked with TTX, they probably are based on the persistent sodium currents. The opposing drive in hyperpolarizing direction may be provided by strong outward currents that generated a marked outward rectification in the current-voltage relationship under TTX. In conclusion, PN neurons show complex membrane properties that are reminiscent in many ways to cerebrocortical "regular firing" neurons.
1996
Recurrent axon collaterals of corticothalamic projection neurons in rat primary somatosensory cortex contribute to excitatory and inhibitory feedback-loops.
Staiger JF, Zilles K, Freund TF.
Anat Embryol 194: 533-543., 1996.
Innervation of VIP-immunoreactive neurons by the ventroposteromedial thalamic nucleus in the barrel cortex of the rat.
Staiger JF, Zilles K, Freund TF.
J Comp Neurol 367: 194-204., 1996.
Distribution of GABAergic elements postsynaptic to ventroposteromedial thalamic projections in layer IV of rat barrel cortex.
Staiger JF, Zilles K, Freund TF.
Eur J Neurosci 8: 2273-2285., 1996.
Inverse relationship between brain size and callosal connectivity.
Steinmetz H, Staiger JF, Schlaug G, Huang YX, Jäncke L.
Naturwissenschaften 83: 221., 1996.
1995
Increased corpus callosum size in musicians.
Schlaug G, Jäncke L, Huang YX, Staiger JF, Steinmetz H.
Neuropsychologia 33: 1047., 1995.
Corpus callosum and brain volume in women and men.
Steinmetz H, Staiger JF, Schlaug G, Huang Y, Jäncke L.
Neuroreport 6: 1002-1004., 1995.
1992
Restricted origin and distribution of projections from the lateral to the medial septal complex in rat and guinea pig.
Witter MP, Daelmans HEM, Jorritsma-Byham B, Staiger JF, Wouterlood FG.
Neurosci Lett 148: 164-168., 1992.
1991
The efferent connections of the lateral septal nucleus in the guinea pig: intrinsic connectivity of the septum and projections to other telencephalic areas.
Staiger JF, Nürnberger F.
Cell Tissue Res 264: 415-426., 1991.
The efferent connections of the lateral septal nucleus in the guinea pig: projections to the diencephalon and brainstem.
Staiger JF, Nürnberger F.
Cell Tissue Res 264: 391-413., 1991.
1990
Efferent projections from the lateral septal nucleus to the anterior hypothalamus in the rat: a study combining Phaseolus vulgaris-leucoagglutinin tracing with vasopressin immunocytochemistry.
Staiger JF, Wouterlood FG.
Cell Tissue Res 261: 17-23., 1990.
Columnar arrangement of lumbar motoneurons innervating a pair of antagonistically acting leg muscles in the rat.
Staiger JF, Nürnberger F.
Z mikrosk -anat Forsch 104: 79-86., 1990.
1989
Pattern of afferents to the lateral septum in the guinea pig.
Staiger JF, Nürnberger F.
Cell Tissue Res 257: 471-490., 1989.