Deciphering the Daam2-VHL signaling axis in oligodendrocyte development and white matter injury

摘要和摘要 胶质细胞约占中枢神经系统(CNS)细胞成分的60%，发挥着多样化的作用 在起作用的中枢神经系统和一系列神经疾病中的作用。神经胶质细胞系的发育进展 按照严格调控的程序进行，包括构图、产生不同的细胞、分化和 髓鞘形成。这种一连串的发育事件特别容易受到新生儿缺氧性脑损伤的影响， 这会导致髓鞘少突胶质细胞(OLs)的严重丧失，广泛的白质损伤， 最终导致神经元功能障碍。尽管有机硅具有强大的再生能力，但潜在的 低氧损伤后神经回路中髓鞘减少和继发性缺陷的机制 仍然没有明确的定义。此外，髓鞘形成在整个成年期早期持续，这也使 中枢神经系统易受侮辱，导致迟发性神经变性。因此，这一行动的首要目标是 应用是定义在发育和修复过程中驱动OL成熟的新基因和新途径，以及 精确定位白质障碍的潜在靶向通路。之前，我们确定了Daam2 (蓬乱的形态发生相关激活因子2)作为OL髓鞘形成和修复的关键调节因子，以及 最近发现Daam2通过缺氧调节因子的泛素化来控制OL的分化 VHL(冯·希佩尔-林道)。此外，我们还发现Daam2受两种E3连接酶Nedd4(Neuroal)的调节 前体细胞表达发育下调蛋白4)和Trim9(包含 9)，进而控制VHL泛素化和OL分化。这些观察提出了两个关键问题 我们将在这项提案中提出的问题是：1)DAAM2如何在OL中调制VHL-HIF信号？和2) 泛素介导的DAAM2降解在OL中是如何控制的？通过深入了解 DAAM2的作用机制，我们将建立DAAM2抑制作为临床意义和 脑白质损伤治疗的可行策略。为了回答这些关键问题，我们将首先定义 DAAM-2和VHL在OL发育和白质损伤中的相互关系(目标1)。 这些研究将把Daam2-VHL轴定义为OL发育的关键调节因子，同时揭示了新的 髓鞘形成过程中Wnt信号与低氧途径的关系接下来，我们将确定 OLS中的Daam2蛋白酶体降解途径(目标2)。完成后，这些研究将确定如何 Daam2受靶E3连接酶调控，发现Nedd4和Trim9是新的OL髓鞘形成调节因子。 从机制上理解DAAM2-VHL轴在少突胶质细胞损伤修复中的作用 关于细胞对白质损伤的易感性，并最终指出了治疗发展的新场所 以刺激OL重新髓鞘形成。

SUMMARY and ABSTRACT Glia comprise approximately 60% of the cellular constituency of central nervous system (CNS), playing diverse roles in the functioning CNS and a host of neurological disorders. Development of glial cell lineages proceeds along a tightly regulated program that involves patterning, generation of diverse cells, differentiation, and myelination. This cascade of developmental events is particularly vulnerable to neonatal hypoxic brain injury, which leads to profound loss of myelinating oligodendrocytes (OLs), extensive white matter damage, culminating in neuronal dysfunction. Despite the robust regenerative capacity of OLs, the underlying mechanisms mediating hypomyelination and the subsequent defects in neural circuits after hypoxic injury remain poorly defined. Moreover, myelination continues throughout early adulthood, which also renders the CNS susceptible to insults causing late-onset neurodegeneration. Therefore, the overarching goal of this application is to define new genes and pathways that drive OL maturation during development and repair, and pinpoint potential targetable pathways for white matter disorders. Previously, we identified Daam2 (Disheveled associated activator of morphogenesis 2) as a pivotal regulator of OL myelination and repair, and recently discovered that Daam2 governs OL differentiation through ubiquitination of the hypoxia regulator VHL (von Hippel-Lindau). Moreover, we discovered that Daam2 is regulated by two E3 ligases, Nedd4 (Neural precursor cell expressed developmentally down-regulated protein 4) and Trim9 (Tripartite Motif Containing 9), which in turn govern VHL ubiquitination and OL differentiation. These observations raise two key questions that we will pursue in this proposal: 1) how does Daam2 modulate VHL-HIF signaling in OLs? and 2) how is the ubiquitin-mediated Daam2 degradation controlled in OLs? By understanding the in-depth mechanisms by which Daam2 operates, we will establish Daam2 inhibition as a clinically significant and actionable strategy for the treatment of white matter injury. To answer these key questions, we will first define the reciprocal relationship between Daam2 and VHL during OL development and white matter injury (Aim 1). These studies will define the Daam2-VHL axis as a pivotal regulator of OL development, while revealing novel connections between Wnt signaling and hypoxic pathway during OL myelination. Next, we will determine Daam2 proteasomal degradation pathways in OLs (Aim 2). Upon completion, these studies will define how Daam2 is regulated by target E3 ligases, and identify Nedd4 and Trim9 as novel regulators of OL myelination. A mechanistic understanding of Daam2-VHL axis function in oligodendrocyte repair after injury will shed light on cellular vulnerability to white matter injury and ultimately point to new venues for therapeutic development to stimulate OL remyelination.