The Role of Notch Signaling in Shh-mediated Oligodendrocyte Fate Specification

项目摘要 少突胶质细胞是中枢神经系统中形成髓鞘的神经胶质细胞，髓鞘对于神经系统的正常功能至关重要。 神经回路的形成和功能。在大脑发育过程中，神经祖细胞首先产生 兴奋性神经元，然后逐渐过渡到少突胶质细胞前体细胞（OPCs）的生产; 这种现象被称为“神经胶质开关”。而OPCs和髓鞘的少突胶质细胞分化 虽然我们对神经胶质细胞的形成已经很清楚，但我们仍然不知道促进神经胶质细胞转换的早期机制。 并指定祖细胞朝向OPC命运。本研究的目的是了解发育和分子 在发育中的小鼠中指导神经祖细胞产生OPCs而不是神经元的机制 新皮层我们的实验室以前确定了Sonic hedgehog（Shh）作为一种关键的细胞外信号， 胚胎发育后期神经元-神经胶质的转换。然而，尽管一些祖细胞在细胞中产生OPCs， 对Shh的反应，其他人继续产生神经元。这表明共存的神经祖细胞 差异响应Shh，需要额外的细胞内在机制来获得OPC命运。我们的单人 细胞RNA测序分析和我的初步数据表明，无论是Notch信号通路， 转录因子Ascl 1对于促进响应Shh的神经祖细胞的OPC特化是至关重要的。 重要的是，Ascl 1最近被鉴定为能够促进染色质的先驱转录因子 直接细胞命运的可及性。基于这些数据，我假设Notch信号通路促进了 OPC规范通过调节神经祖细胞对Shh的反应，除了建立 表观遗传状态通过Ascl 1为OPC命运做好准备。我将在两个具体目标中测试这个假设：1）定义 Notch信号在Shh介导的OPC特化中的功能作用， 离体药理学方法和2）测试Notch信号传导与Ascl 1合作以 促进用于指定少突胶质细胞谱系的表观遗传状态。这些目标的实现将大大 有助于更好地了解神经细胞命运的规范和少突胶质细胞的发展，这将 允许新的工具和方法来恢复疾病和损伤后的髓鞘。

PROJECT SUMMARY Oligodendrocytes are glial cells in the central nervous system that form myelin, which are critical for the proper formation and function of neural circuits. During brain development, neural progenitor cells first give rise to excitatory neurons before gradually transitioning to the production of oligodendrocyte precursor cells (OPCs); a phenomenon known as the “neuron-glia switch”. Whereas oligodendrocyte differentiation from OPCs and myelin formation are well understood, we still do not know the earlier mechanisms that facilitate the neuron-glia switch and specify progenitors towards an OPC fate. This study aims to understand the developmental and molecular mechanisms that instruct neural progenitors to generate OPCs instead of neurons in the developing mouse neocortex. Our lab previously identified Sonic hedgehog (Shh) as a critical extracellular signal that initiates the neuron-glia switch during late embryonic development. However, while some progenitors generate OPCs in response to Shh, others continue to produce neurons. This suggests that co-existing neural progenitors differentially respond to Shh and require additional cell-intrinsic mechanisms to acquire an OPC fate. Our single cell RNA-sequencing analysis and my preliminary data indicate that both the Notch signaling pathway and the transcription factor Ascl1 are critical for promoting OPC specification from neural progenitors in response to Shh. Importantly, Ascl1 has recently been identified as a pioneer transcription factor capable of promoting chromatin accessibility to direct cell fates. Based on these data, I hypothesize that the Notch signaling pathway promotes OPC specification by regulating the response of neural progenitors to Shh in addition to establishing an epigenetic state primed for the OPC fate through Ascl1. I will test this hypothesis in two Specific Aims: 1) Define the functional role of Notch signaling in Shh-mediated OPC specification using in vivo genetic manipulations and ex vivo pharmacological approaches and 2) Test the hypothesis that Notch signaling cooperates with Ascl1 to promote an epigenetic state for specifying the oligodendrocyte lineage. Completion of these aims will significantly contribute to a better understanding of neural cell fate specification and oligodendrocyte development, which will allow for novel tools and methods to restore myelin following disease and injury.