Mechanism of hypoxia mediated failure of oligodendrocyte generation

项目总结 在美国，几乎每10个孩子中就有一个是早产的，尽管在 围产期护理增加了早产儿的存活率，其中许多孩子继续展示 神经发育缺陷导致严重的认知和运动功能障碍。最常见的一种 早产后的神经系统损害是弥漫性白质损伤(DWMI)，它被认为是由 肺发育和脑发育不成熟状态对发育中脑的缺氧性损伤 血管系统疾病，无法治愈。白质是中枢神经系统内交流所必需的， 主要由髓鞘组成，髓鞘是围绕神经元轴突的脂肪鞘，以允许有效的行动。 潜在的传播。髓鞘是由成熟的少突胶质细胞产生的，这些少突胶质细胞是通过分化而产生的 少突胶质前体细胞(OPC)。在弥漫性脑缺血的背景下，低氧导致脑组织细胞的凋亡。 少突胶质细胞谱系继而增殖和随后的少突胶质细胞再生失败 剩余的OPC。低氧后OPC产生少突胶质细胞的这种缺陷可以通过以下方法消除 敲除低氧诱导因子(HIF)，HIF是DNA结合的转录因子，在 低氧，并在常氧条件下在OPC中迅速降解。然而，HIF如何阻止的机制 少突胶质细胞的生成仍然难以捉摸。利用我们实验室的能力来产生大量纯净的人口 在OPC中，我对HIF1a和H3K27Ac进行了CHIP-SEQ，H3K27Ac是活性染色质的标志，以确定 可能是OPC基因组中的HIF靶点。基于HIF1a结合的首选候选目标以及 H3K27Ac的浓缩提示了一种已被证明对干细胞重要的转录因子 中枢神经系统外组织的维持是OPC中HIF的靶点。我证明了这一点 该转录因子的过表达足以抑制OPC向少突胶质细胞的分化 在缺氧性心肌梗死小鼠模型中表达上调。这项建议旨在进一步调查 这些发现通过1)利用细胞、分子和遗传技术的组合来确定 该转录因子抑制OPC分化的机制2)决定是否下调 该转录因子的表达将促进体外缺氧损伤后少突胶质细胞的形成 3)研究了体内转录因子上调的时空动态。 DWMI的小鼠模型。这项提案中概述的实验将增加我们对机制的理解 这阻碍了OPC在低氧条件下产生少突胶质细胞，并将揭示新的途径 对这种高度流行和衰弱的神经发育疾病进行治疗干预。

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.