TRANSCRIPTIONAL REGULATION BY GEMININ

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DESCRIPTION (provided by applicant): Undifferentiated neural precursor cells can be derived from embryonic stem cells or reprogrammed somatic (iPS) cells in unlimited quantities, have broad differentiation potential, can be modified by genetic engineering or clonally selected for particular properties and, for iPS cells, can be patient-matched to avoid immunological incompatibilities. Therefore, these cells are of high significance for in vitro modeling of human neurological diseases and for developing transplantation-based therapies to replace or stimulate repair of damaged tissue. Given the broad utility of these cells, we know surprisingly little about cell intrinsic regulatory networks that direct the initial acquisition of a neural fate and that maintain neural precursors in an undifferentiated state. This significantly limits our understanding of neural development and hampers efforts to compare and manipulate neural precursor cells derived from different starting cell sources or protocols. During vertebrate embryogenesis, Geminin and the Zic family of zinc finger transcription factors control the earliest cell intrinsic responses to neural induction and have essential roles in initial neural specification and maintenance of the undifferentiated state. Mutational analyses of these transcription factors supports their central roles in development and contribution to human disease: complete loss of Geminin results in early embryonic lethality in mice, while Zic1-4 mutations in humans cause a range of embryonic and nervous system malformations and neurological disorders. However, regulatory networks and mechanisms through which these transcription factors act remain largely unknown. Here, we will elucidate transcriptional programs and direct targets that they control at a genome-wide level and will use these data to construct regulatory networks underlying neural fate acquisition. We will test the hypothesis that Geminin is a central regulator of neural versus non-neural fate choice, through interactions with distinct epigenetic regulatory complexes. This work will define epigenetic regulatory mechanisms that direct the earliest aspects of embryonic cell fate acquisition. We will pursue the following Specific Aims: 1. Determine mechanisms by which Geminin activates neural gene expression to promote neural cell fate, 2. Define and compare the transcriptional regulatory networks through which the Zic transcription factors and Geminin control neural specification, and 3. Test the hypothesis that Geminin acts cooperatively with Polycomb to repress non-neural, mesendodermal gene expression during early fate acquisition of embryonic cells. Together, this work will define the regulatory networks controlling initial neural fate acquisition will identify new neural regulatory activities and modes of regulation, and will determine mechanisms through which several epigenetic regulators centrally control cell state and developmental potential during early fate acquisition. These data will fill a fundamental gap in our understanding of early cell fate acquisition. They will inform our understanding of birth defects and provide an essential foundation for manipulating these regulatory networks to control neural cell specification in many biological contexts.