Gordon Fishell

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..The mechanisms underlying the commitment of telencephalic cells to specific regional identities have been examined through recent transplantation experiments...

..We suggest two models that make opposite predictions as to whether the radial glia or nascent neuron inherit the radial glial fiber or the majority of the Numb protein...

..Here, we discuss these new findings in the context of our present understanding of cortical cell specification...

..Finally we speculate regarding the attractiveness and challenges of establishing a unifying nomenclature to describe inhibitory neuron diversity throughout the telencephalon...

..Taken together, our data support a model in which Gsh2, in response to sonic hedgehog signaling, plays a crucial role in multiple aspects of telencephalic development...

..Hence, the competence to generate the earliest born neurons during later cortical development is actively suppressed but not lost...

..Moreover, we report that the migratory fate of cells from the CGE is intrinsically determined by embryonic day 13.5 (E13.5). Together, these results provide the first insights into the development and fate of the CGE...

..Thus, radial glial populations within different CNS regions are not heterogeneous with regard to their potential to generate neurons versus glia...

..Our strategy reveals a causal link between the embryonic genetic specification by Nkx2-1 in progenitors and the functional attributes of their neuronal progeny in the mature nervous system...

..A primary challenge in the future will be to investigate what aspects of interneuron diversity are determined by intrinsic genetic programmes within each lineage versus those properties imposed by the local environment in the cortex...

..Moreover, our work has revealed that many of the genes expressed in cortical interneuron precursors have been independently linked to neurological disorders in both mice and humans...

..This review examines the role of Notch during gliogenesis in both fruit flies and vertebrates, as well as evidence in vertebrates that some glia may be stem cells...

..We observe that the physiological subtypes of cortical interneurons are, to a large degree, unique to their time point of generation...

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..The universal modulation of these neurons by serotonin and acetylcholine via ionotropic receptors suggests that they might be involved in shaping cortical circuits during specific brain states and behavioral contexts...

..We compare the data garnered from in vitro analysis to what has been learned from the transplantation of NSCs into the developing, adult or lesioned brain...

..Recent studies in Cell Stem Cell (Eiraku et al., 2008) and Nature (Gaspard et al., 2008) demonstrate that embryonic stem cells can recapitulate early cortical development, enabling them to generate specific cortical subtypes...

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..Thus, we demonstrate that the cerebellar rhombic lip gives rise to multiple cell types within rhombomere 1...

..Thus, in conjunction with previous studies, we have now determined the spatial and temporal origins of the vast majority of cortical interneuron subtypes...

..Together, our findings are consistent with Pax6 function being required for aspects of Gli3-mediated telencephalic patterning...

..Finally, we will conclude by calling the readers attention to the devastating consequences that result from developmental failures in the formation of inhibitory circuits within the cortex...

..Together we provide the first comprehensive analysis of the temporal generation of OB interneuron subtypes and demonstrate that the timing by which these populations are produced is tightly orchestrated...

..We suggest these developmental changes in competence are mediated by a transcriptional mechanism that intrinsically integrates information from the distinct signaling pathways that act to pattern the telencephalic neuroepithelium...

..It is, however, necessary for their normal positioning and maturation. As a consequence, the specific removal of Sox6 from this population results in a severe epileptic encephalopathy...

..These results identify Blbp as the first predominantly CNS-specific Notch target gene and suggest that it mediates some aspects of Notch signaling in radial glia...

..5 CGE. Thus, we provide evidence that the spatial and temporal origin of interneuron precursors in the developing telencephalic eminences predicts the intrinsic physiological properties of mature interneurons...

..Most notably, upon transplantation to the perinatal cerebellum, cerebellar stem cells from all ages are able to acquire the position and mature electrophysiological properties of cerebellar granule cells...

..These results indicate that Notch signaling is required in neural progenitor cells to control cell fate in the striatum, but is dispensable during subsequent phases of neuronal migration and differentiation...

..These results suggest that hedgehog signaling is required to maintain progenitor cells in the postnatal telencephalon...

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..As a result, the promise of being able to use transgenics to target specific neuronal populations is now being realized...

..These results are discussed in the context of the purported role of Shh as a morphogen...

..This recovery may be, at least in part, a result of the late migration of Dlx2 progenitors from the caudal ganglionic eminences (CGE), which, based on our previous work, does not appear to require Nkx2.1 gene function...

..In addition these results support the idea that, in addition to hedgehog signaling, a Shh-independent pathways must act during development to pattern the telencephalon...

..These results suggest that Hedgehog signaling is required for the maintenance of the B and C cell populations and indirectly for the migration of the neurons that are generated from the adult stem cell niche...

..These results demonstrate that ongoing hedgehog signaling is required to maintain adult neural stem cells and that their ability to self-renew is limited...

..Here we review our present knowledge of the hedgehog signalling pathway and speculate about areas in which further insights into this versatile pathway might be forthcoming...

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..0 and E12 is essential for the patterning of ventral regions and the generation of cell types that are thought to largely arise from them...

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..Moreover, through the genetic profiling of these cells we expect to be able to directly link the function of these cells to specific genetically inherited disorders in human patients. ..

..Together this proposal will provide a comprehensive examination of Shh signaling during telencephalic development. ..

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..Our studies will reveal the mechanisms by which these populations are generated and thus provide the first step towards finding a cure to these disorders. ..

..Our studies will reveal the mechanisms by which these populations are generated and thus provide the first step towards finding a cure to these disorders. ..

..This proposal will therefore provide the first comprehensive analysis of the developmental origins of cortical interneuron diversity. ..

..The position, morphology and gene expression within clones resulting from control versus ectopic expression viral vector infections will allow us to evaluated the function of these genes during neural development. ..

..Together the sets of experiments described in this proposal will examine the establishment of the subdivisions of forebrain and their significance to the determination of regional cell identity. ..

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..If we can understand how this population is generated, we will take the first step towards assessing whether we can use gene or cell therapies to ameliorate the devasting consequences associated with cortical interneuron dysfunction. ..