Mechanism of hypoxia mediated failure of oligodendrocyte generation

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PROJECT SUMMARY Nearly 1 out of every 10 children are born prematurely in the United States and although advancements in perinatal care have resulted in the increased survival of preterm infants, many of these children go on to exhibit neurodevelopmental deficits leading to significant cognitive and motor dysfunction. One of the most common neurologic insults following preterm birth is diffuse white matter injury (DWMI), which is thought to arise from hypoxic injury to the developing brain caused by the immature state of lung development and cerebral vasculature and has no cure. White matter is required for communication within the central nervous system and is primarily composed of myelin, which is a fatty sheath that surrounds neuronal axons to allow efficient action potential propagation. Myelin is generated by mature oligodendrocytes, which arise via differentiation of oligodendrocyte progenitor cells (OPCs). In the context of DWMI, hypoxia leads to apoptosis of cells of the oligodendrocyte lineage followed by proliferation and failure of subsequent oligodendrocyte regeneration from residual OPCs. This deficit in oligodendrocyte generation from OPCs following hypoxia can be abrogated by knocking out hypoxia inducible factors (HIFs), which are DNA-binding transcription factors that accumulate under hypoxia and are rapidly degraded in normoxia, in OPCs. However, the mechanism of how HIFs block oligodendrocyte generation remains elusive. Leveraging our lab’s ability to generate large and pure populations of OPCs, I performed ChIP-seq for HIF1a and H3K27Ac, a marker of active chromatin, in order to determine putative HIF targets across the OPC genome. The top candidate target based on HIF1a binding as well as enrichment of H3K27Ac suggested a transcription factor that has been shown to be important for stem cell maintenance in tissues outside the central nervous system as a target of HIF in OPCs. I demonstrate that overexpression of this transcription factor is sufficient to inhibit differentiation of OPCs to oligodendrocytes and is upregulated following hypoxic injury in a mouse model of DWMI. This proposal seeks to further investigate these findings by 1) utilizing a combination of cellular, molecular and genetic techniques to determine the mechanism by which this transcription factor inhibits OPC differentiation 2) determining whether downregulation of this transcription factor will facilitate recovery of oligodendrocyte formation following hypoxic injury in vitro and 3) characterizing the spatiotemporal dynamics of the upregulation of this transcription factor in vivo using a mouse model of DWMI. The experiments outlined in this proposal will increase our understanding of mechanisms that impede oligodendrocyte generation from OPCs under hypoxic conditions, and will uncover novel avenues for therapeutic intervention for this highly prevalent and debilitating neurodevelopmental condition.