Olig2 phosphorylation and the regulation of neural stem cell fate (360G-Wellcome-092844_Z_10_Z)

During development of the central nervous system (CNS), neuroepithelial stem cells (NSCs), residing in the ventricular zones (VZ) of the embryonic brain and spinal cord, divide and differentiate to generate all the neurons and glial cells (astrocytes and oligodendrocytes) of the mature CNS. Typically, neurons form before glia. In the ventral spinal cord, for example, embryonic NSCs of the pMN progenitor domain generate several subtypes of motor neurons (MNs) before switching abruptly (at E12.5 in mouse) to production of oligodendrocyte precursors (OLPs). The OLPs then migrate away from the VZ into all parts of the spinal cord before associating with axons, differentiating into post-mitotic oligodendrocytes (OLs) and synthesizing myelin. We aim to address how NSCs switch at a predetermined time from neuron to glial production ? specifically, the mechanism of the MN-OLP fate switch in the ventral spinal cord. Broadly, the proposed project aims to characterize the role and regulation of the basic helix-loophelix transcription factor Olig2 in the MN-OLP fate-switch. Recent work from the Richardson lab showed that a specific serine residue (S147) in Olig2 is phosphorylated during MN specification and de-phosphorylated at the switch to OLP production. What triggers de-phosphorylation of Olig2 at the time of the MN-OLP switch? The sequence surrounding S147 conforms to a protein kinase-A target site, but the identity of the putative phosphatase responsible for dephosphorylation has not been established. What are the targets and co-factors of Olig2 in its different phosphorylated states that coordinate the temporally-defined switch in NSC fate? And what are the functions of the other predicted Olig2 phosphorylation states? This project will involve three distinct lines of investigation. 1: Characterizing the expression of candidate phosphatases/phosphatase inhibitors in the ventral spinal cord at the time of the MNOLP fate-switch. 2: Identifying target genes of Olig2 in its phosphorylated and de-phosphorylated states. 3: Characterizing the developmental function of another Olig2 phosphorylation site, S263, a potential target of p38 mitogen-activated protein kinase (MAPK).