Sip1 regulates sequential fate decisions through feedback signalling from postmitotic neurons to progenitor cells.

ABSTRACT: In the developing cerebral cortex different types of neurons and glial cells are born through a precisely controlled sequence of events. The fate of cortical progenitors, in turn, is determined by an elusive conundrum of temporally and spatially regulated signalling mechanisms. We found the DNA-binding transcription factor Sip1 (also known as Zfhx1b) to be produced at high levels in postmitotic neurons of the cerebral cortex. Conditional deletion of Sip1 in young neocortical neurons was found to induce premature and increased production of upper layer neurons at the expense of deep layer neurons. Furthermore, it caused precocious and increased generation of glial precursors during late corticogenesis, leading subsequently to enhanced astrocytogenesis at early postnatal stages. Expression profiling analysis indicated that the temporal shift in upper layer production coincides with overexpression of the neurotrophin-3 (NT3) gene and altered growth factor signalling in progenitors, while the premature gliogenesis is preceded by upregulation of fibroblast growth factor-9 (Fgf9) gene expression. Chromatin immunoprecipitation and in situ hybridization validates NT3 as a direct target of Sip1 in the cortex and confines the transcriptional repression by Sip1 to postmitotic neurons. Moreover, we show that exogenous application of Fgf9 in solution or via coated beads to wild-type cortical slices induces premature and excessive generation of glial precursors in the germinal zone. In conclusion, our data suggest that throughout corticogenesis Sip1 acts to restrain the level of production of secreted signalling factors in postmitotic neurons. These factors feed back to progenitor cells in order to regulate the timing of cell fate switch and the numbers of neurons and glial cells produced in the developing cerebral cortex.

ORGANISM(S): Mus musculus

PROVIDER: GSE16699 | GEO | 2009/10/30

SECONDARY ACCESSION(S): PRJNA117355

REPOSITORIES: GEO