The role of mTOR signaling in oligodendrocyte differentiation and CNS myelination

描述(由申请人提供)：目前的研究是一项多重P.I.建议，重点关注mTOR在少突胶质细胞发育和中枢神经系统髓鞘形成中的作用。这是一个重要的研究领域，因为人类脱髓鞘的破坏性后果，以及需要了解髓鞘形成和再髓鞘形成如何调控的分子细节，以便修复这种损伤。Macklin实验室研究了Akt和mTOR在中枢神经系统髓鞘形成中的作用，Wood实验室研究了mTOR在少突胶质细胞分化中的作用，并在少突胶质细胞中发现了mTOR调节的蛋白质组。关于在少突胶质细胞的发育过程中，mTOR何时成为主要调节因子，在文献和两个实验室的初步数据中存在不一致的情况。因此，目前的建议旨在明确回答mTOR信号复合体何时以及如何调控少突胶质细胞的发育，包括对分化和髓鞘形成的潜在作用。而不是竞争来解决这些问题，我们提出了一个合作项目，使用互补的鼠系，标准化的试剂和技术。这两个实验室拥有互补的条件性突变小鼠组，它们将被共同用于研究这些问题。在第一个特定目标中，我们将研究mTOR调节少突胶质细胞分化的机制，验证mTOR通过mTORC1和mTORC2的特定作用直接调节少突胶质细胞分化的假设。这将通过研究mTOR、Raptor或Rictor条件缺失小鼠中调节的信号通路和分化事件来进行研究。在第二个特定目标中，我们将研究mTOR调节中枢神经系统髓鞘形成和髓鞘维持的机制。我们将检验这一假设，即mTOR通过mTORC1和mTORC2直接调节髓鞘形成，每个复合体都有不同的控制。此外，研究还将调查中枢神经系统中活跃的髓鞘形成如何转变为髓鞘维持。在第三个特定目标中，我们将研究TSC1/2在发育的少突胶质细胞中对这两个mTOR复合体的上游调控。这些研究将验证TSC信号通过上游抑制mTORC1和激活mTORC2来调节少突胶质细胞分化和中枢神经系统髓鞘形成的假设。TSC1/2被认为是mTOR信号的负性调节因子，但在某些情况下，TSC活性的丧失会导致髓鞘减少，而不是预期的超髓鞘形成。因此，确定它们如何影响少突胶质细胞中的mTOR信号是很重要的。在最终目标中，我们将确定mTOR途径调节重新髓鞘形成的机制。这一目标的关键问题将是，该通路在调节少突胶质细胞分化和髓鞘形成中的作用是否概括了其 是否在发育过程中发挥作用，或者是否有独特的mTOR元件调节成人组织中的再髓鞘形成。这一目标显然对我们理解多发性硬化症的重新髓鞘形成有重大影响。

DESCRIPTION (provided by applicant): The current studies are a multiple-P.I. proposal that focuses on the role of mTOR in oligodendrocyte development and CNS myelination. This is an important research area because of the devastating consequences of demyelination in humans and the need to understand the molecular details of how myelination and remyelination are regulated, in order to repair such damage. The Macklin laboratory has investigated the role of Akt and mTOR in CNS myelination, while the Wood laboratory has investigated the role of mTOR in oligodendrocyte differentiation and has identified an mTOR-regulated proteome in oligodendrocytes. There is inconsistency in the literature and in the preliminary data from the two laboratories as to when in the developmental program of oligodendrocytes mTOR becomes a major regulator. Thus, the current proposal is designed to answer unequivocally when and how the mTOR signaling complexes regulate oligodendrocyte development including potential actions on both differentiation and myelination. Rather than compete to address these questions, we propose a collaborative project using complementary mouse lines, and standardized reagents and techniques. The two laboratories have complementary sets of conditional mutant mice that will be used collaboratively to investigate these questions. In the first specific aim, we will investigate the mechanisms by which mTOR regulates oligodendrocyte differentiation, testing the hypothesis that mTOR directly regulates oligodendrocyte differentiation via specific actions of both mTORC1 and mTORC2. This will be investigated by studying the signaling pathways and the differentiation events that are modulated in mTOR, raptor or rictor conditionally-deleted mice. In the second specific aim, we will investigate the mechanisms by which mTOR regulates CNS myelination and myelin maintenance. We will test the hypothesis that mTOR directly regulates myelination via both mTORC1 and mTORC2, with differential control by each complex. Studies will additionally investigate how active myelination shifts to myelin maintenance in the CNS. In the third specific aim, we will investigate the upstream regulation of the two mTOR complexes by TSC1/2 in developing oligodendrocytes. These studies will test the hypothesis that TSC signaling regulates oligodendrocyte differentiation and CNS myelination through upstream inhibition of mTORC1 and activation of mTORC2. TSC1/2 are considered to be negative regulators of mTOR signaling, yet in some contexts loss of TSC activity induces hypomyelination rather than the expected hypermyelination. Establishing how they impact mTOR signaling in the oligodendrocyte is therefore important. In the final aim, we will determine the mechanisms by which the mTOR pathway regulates remyelination. The crucial questions in this aim will be whether the role of this pathway in the regulation of oligodendrocyte differentiation and myelination recapitulates its function during development, or whether there are unique elements of mTOR regulation of remyelination in adult tissue. This aim clearly has significant impact on our understanding of remyelination in multiple sclerosis.