Project description:The connectivity, activity, and plasticity of the telencephalon are shaped by pallial and subpallial GABAergic neurons, two large populations that are produced in the embryonic medial, caudal and lateral ganglionic eminences in a highly complicated manner. Dysregulated development of GABAergic neurons is associated with neuropsychiatric disorders. However, knowledge about the specification of GABAergic neuron subtypes is limited. Here, using single-cell RNA sequencing combined with loss-of-function we delineated developmental trajectories and revealed transcriptional programs that specify GABAergic neuron subtypes in each GE lineage and transcription factors that direct lineage bifurcation decisions. Our study illuminates the control of production between pallial and subpallial populations and offers transcriptomic insights into the pathogenesis of GABAergic neuron-related disorders.
Project description:The connectivity, activity, and plasticity of the telencephalon are shaped by pallial and subpallial GABAergic neurons, two large populations that are produced in the embryonic medial, caudal and lateral ganglionic eminences in a highly complicated manner. Dysregulated development of GABAergic neurons is associated with neuropsychiatric disorders. However, knowledge about the specification of GABAergic neuron subtypes is limited. Here, using single-cell RNA sequencing combined with loss-of-function we delineated developmental trajectories and revealed transcriptional programs that specify GABAergic neuron subtypes in each GE lineage and transcription factors that direct lineage bifurcation decisions. Our study illuminates the control of production between pallial and subpallial populations and offers transcriptomic insights into the pathogenesis of GABAergic neuron-related disorders.
Project description:The connectivity, activity, and plasticity of the telencephalon are shaped by pallial and subpallial GABAergic neurons, two large populations that are produced in the embryonic medial, caudal and lateral ganglionic eminences in a highly complicated manner. Dysregulated development of GABAergic neurons is associated with neuropsychiatric disorders. However, knowledge about the specification of GABAergic neuron subtypes is limited. Here, using single-cell RNA sequencing combined with loss-of-function we delineated developmental trajectories and revealed transcriptional programs that specify GABAergic neuron subtypes in each GE lineage and transcription factors that direct lineage bifurcation decisions. Our study illuminates the control of production between pallial and subpallial populations and offers transcriptomic insights into the pathogenesis of GABAergic neuron-related disorders.
Project description:The ventricular-subventricular zone (V-SVZ) is the largest neurogenic region of the postnatal forebrain, containing neural stem cells (NSCs) that emerge from both the embryonic pallium and subpallium. Despite of this dual origin, glutamatergic neurogenesis declines rapidly after birth, while gabaergic neurogenesis persists throughout life. We performed single-cell RNA-sequencing (scRNA-Seq) of the postnatal dorsal V-SVZ for unravelling the mechanisms leading to pallial lineage germinal activity silencing. We show that pallial NSCs enter a state of deep quiescence, characterized by high BMP-signaling, reduced transcriptional activity and Hopx expression, whilst in contrast, subpallial NSCs remain primed for activation. Induction of deep quiescence is paralleled by a rapid blockade of glutamatergic neurons production and differentiation. Finally, manipulation of Bmpr1a demonstrates its key role in mediating these effects. Together, our results highlight a central role of BMP-signaling in synchronizing quiescence induction and blockade of neuronal differentiation to rapidly silence pallial germinal activity after birth.
Project description:In the embryonic telencephalon, the pallial-subpallial boundary (PSB) separates the dorsal Pax6+ pallium from the ventral Gsh2+ subpallium. Previous studies have revealed that this region is a source of cells that will populate both the olfactory bulb and basal telencephalic limbic system. However, the level of progenitor cell heterogeneity and developmental genetic regulation of this progenitor region remains to be fully elucidated. In this study we carried out a comprehensive analysis of gene expression patterns at the PSB, in addition to an examination of the combinatorial function of Pax6 and Gsh2 in the specification of the PSB. First, we reveal that the PSB is comprised of a complex mix of molecularly distinct progenitor pools. In addition, by analysis of single Sey, Gsh2, and Sey/Gsh2 double mutant mice, we demonstrate that both Pax6 and Gsh2 are directly required for major aspects of PSB progenitor specification. Our analysis also reveals that the establishment of the epidermal growth factor receptor positive lateral cortical stream migratory route to the basal telencephalon is Pax6 dependent. Thus, in addition to their well-characterized cross-repressive roles in dorsal/ventral patterning our analyses reveal important novel functions of Gsh2 and Pax6 in the regulation of PSB progenitor pool specification and patterning.
Project description:Pallial functional organization is mediated by the dynamic interplay of a broad spectrum of cellular and molecular cues that promote midline patterning, neurogenesis, axon guidance and neural connectivity. The regulators that orchestrate these seminal processes are still poorly understood. By employing a pallial conditional ablation model, we report that the transcriptional and epigenetic modulator, REST corepressor 2 (Rcor2) plays key roles in organizing the developing corticoseptal boundary. ChIP-seq and RNA-seq analyses reveal that Rcor2 modulates a diverse repertoire of classes of genes with essential roles in CC development, including pallial/subpallial patterning, cell fate specification and axon guidance.
Project description:Dravet syndrome (DS) is a devastating early onset refractory epilepsy syndrome caused by variants in the SCN1A gene. A disturbed GABAergic interneuron function is implicated in the progression to DS but the underlying developmental and pathophysiological mechanisms remain elusive, in particularly at the chromatin level. In this study, we utilized induced pluripotent stem cells (iPSCs) derived from DS cases and healthy donors to model disease-associated epigenetic abnormalities of GABAergic development. Employing the ATAC-Seq technique, we assessed chromatin accessibility at multiple time points (Day 0, Day 19, Day 35, and Day 65) of GABAergic differentiation. Additionally, we elucidated the effects of the commonly used anti-seizure drug valproic acid (VPA) on chromatin accessibility in GABAergic cells. The distinct dynamics in chromatin profile of DS iPSC predicted accelerated early GABAergic development, evident at D19, and diverged further from the pattern in control iPSC with continued differentiation, indicating a disrupted GABAergic maturation. Exposure to VPA at D65 reshaped the chromatin landscape at a variable extent in different iPSC-lines and rescued the observed dysfunctional development in some DS iPSC-GABA. This study provides the first comprehensive investigation on the chromatin landscape of GABAergic differentiation in DS-patient iPSC, offering valuable insights into the epigenetic dysregulations associated with interneuronal dysfunction in DS. Moreover, our detailed analysis of the chromatin changes induced by VPA in iPSC-GABA holds the potential to improve development of personalized and targeted anti-epileptic therapies.
Project description:The human insular lobe, in the depth of the Sylvian fissure, displays three main cytoarchitectonic divisions defined by the differentiation of granular layers II and IV. These comprise a rostro-ventral agranular area, an intermediate dysgranular area, and a dorso-caudal granular area. Immunohistochemistry in human embryos and fetuses using antibodies against PCNA, Vimentin, Nestin, Tbr1, and Tb2 reveals that the insular cortex is unique in that it develops far away from the ventricular zone (VZ), with most of its principal neurons deriving from the subventricular zone (SVZ) of the pallial-subpallial boundary (PSB). In human embryos (Carnegie stage 16/17), the rostro-ventral insula is the first cortical region to develop; its Tbr1+ neurons migrate from the PSB along the lateral cortical stream. From 10 gestational weeks (GW) onward, lateral ventricle, ganglionic eminences, and PSB grow forming a C-shaped curvature. The SVZ of the PSB gives rise to a distinct radial glia fiber fascicle (RGF), which courses lateral to the putamen in the external capsule. In the RGF, four components can be established: PF, descending from the prefrontal PSB to the anterior insula; FP, descending from the fronto-parietal PSB toward the intermediate insula; PT, coursing from the PSB near the parieto-temporal junction to the posterior insula, and T, ascending from the temporal PSB and merging with components FP and PT. The RGF fans out at different dorso-ventral and rostro-caudal levels of the insula, with descending fibers predominating over ascending ones. The RGF guides migrating principal neurons toward the future agranular, dysgranular, and granular insular areas, which show an adult-like definition at 32 GW. Despite the narrow subplate, and the absence of an intermediate zone except in the caudal insula, most insular subdivisions develop into a 6-layered isocortex, possibly due to the well developed outer SVZ at the PSB, which is particularly prominent at the level of the dorso-caudal insula. The small size of the initial PSB sector may, however, determine the limited surface expansion of the insula, which is in contrast to the exuberant growth of the opercula deriving from the adjacent frontal-parietal and temporal VZ/SVZ.