This project investigates how transcription factors control the proliferation and differentiation of neural stem cells in the developing cerebral cortex and thereby cortical growth. The cortex confers humans with their unique cognitive capabilities and relies on a striking diversity of neurons to fulfil its highly complex tasks. Generating these different neurons in sufficient numbers requires controlling the balance between proliferation and differentiation of neural stem cells from which these neurons are formed. Changes in these parameters can have profound effects on cortical size and are thought to underlie cortical malformations in human disease and the expansion of the human cerebral cortex during evolution. Regulating gene activity presents a dominant factor in cortical stem cells to control the balance between proliferation and differentiation. Mutations in transcription factor genes or in promoters and enhancers can have profound effects on cortical size and are associated with intellectual disability and risk for neuropsychiatric disease. Despite the importance of transcription factors for cortical growth, their role has mainly been investigated in model organisms but very little is known how these factors act in human cortical stem cells. This project will investigate the roles of the GLI3 and DMRTA2 transcription factor genes. GLI3 mutations result in Greig Cephalopolydactyly Syndrome (GCPS) and an enlarged cortex, while DMRTA2 mutations lead to lissencephaly and a smaller cortex. This project will use Crispr/Cas9 gene editing to introduce loss-of-function mutations of these genes in human iPSCs. We will determine proliferation and differentiation rates in cortical stem cells derived from the mutant iPS cell lines. Using mRNAseq and chromatin immunoprecipitation experiments, we will identify target genes and processes controlled by the GLI3 and DMRTA2 transcription factors in neural progenitor proliferation. These analyses will be a vital step towards gaining a comprehensive understanding how transcription factors coordinate the proliferation of cortical stem cells. This research also has implications for our understanding of how cortical malformations develop in syndromes in which genes encoding transcription factors are mutated. References Heide, M. et al., Novel gene function and regulation in neocortex expansion. Curr Opin Cell Biol. 49,22-30 (2017). Hasenpusch-Theil K. et al., Gli3 controls the onset of cortical neurogenesis by regulating the radial glial cell cycle through Cdk6 expression. Development (2018), doi: 10.1242/dev.163147. Desmaris, E. et al., DMRT5, DMRT3 and EMX2 cooperatively repress Gsx2 at the pallium-subpallium boundary to maintain cortical identity in dorsal telencephalic progenitors. J Neurosci. doi: 10.1523/JNEUROSCI.0375-18.2018 (2018).