Genetic control of neural stem cell homeostasis

项目摘要 神经系统的发育、生长和再生依赖于神经干细胞(NSC)的动态平衡，一种 NSC自我更新、分化和生存之间的微妙平衡。神经干细胞动态平衡缺陷是其基础 广泛的神经发育、精神和神经退行性疾病。分子和细胞机制 神经干细胞内稳态的调控机制目前仍知之甚少。我们建议澄清基本的 利用果蝇幼虫脑II型神经母细胞研究神经干细胞稳态的遗传控制机制 (国家统计局)作为模范。果蝇NBS在发现信号分子和细胞 参与神经干细胞动态平衡的主要机制。与哺乳动物神经干细胞在谱系结构上相似， 果蝇幼虫大脑中的II型NB谱系包含运输放大中间祖细胞(IP)，它可以 产生大量不同的后代。Notch信号是维持细胞内环境平衡的关键 II型NB谱系。抑制Notch信号会导致NB不能正常维护，而Notch 过度激活导致异位NB的形成和脑肿瘤的发生。Notch信令还调节 哺乳动物神经干细胞的动态平衡，N信号失控与脑癌有关。分子 然而，N信号调节NSC稳态的机制还不是很清楚。以前的研究 神经干细胞中的N信号主要集中在无毛[SU(H)]-抑制子介导的典型N信号上。 相关转录因子。然而，我们在前一个资助期的研究发现，一种新的非 在细胞质中运行的典型N信号通路也是至关重要的。此非规范的组件 N信号通路包括线粒体PTEN诱导的激酶1(PINK1)，雷帕霉素的机制靶点 复合体-2(MTORC2)和mTORC2底物AKT。这一非典型N信号通路的临床意义 我们的观察结果表明，果蝇大脑中的肿瘤起始肿瘤干细胞(CSC)样细胞 肿瘤模型和人类GBM样本对这一途径的扰动特别敏感。此外，我们 发现这种非正则途径对线粒体氧化磷酸化起翻译控制作用 相关的mRNA。这项提案的目标是摆脱神经干细胞转录调控的现状 通过关注新发现的N信号中的翻译控制机制。我们的中心假设是 非典范N信号通过线粒体的共翻译质量控制调节NSC的稳态 MRNAs，从而调节线粒体蛋白质组和功能。为了验证这一假设，我们提出了两个具体的 目标。目标1将阐明共翻译质量控制通路如何介导Notch对NSC的影响 动态平衡。目标2将剖析Notch调节共译质量的分子机制 控制过程。在成功完成这些目标后，我们将产生新的机械洞察力 Notch对NSC动态平衡的调控我们预计，这将为研究开辟全新的方向 Notch在神经干细胞生物学、癌症生物学和成人大脑功能中的基本作用。

Project Summary Nervous system development, growth, and regeneration depend on neural stem cell (NSC) homeostasis, a state of delicate equilibrium between NSC self-renewal, differentiation, and survival. Defects in NSC homeostasis underlie broad neurodevelopmental, psychiatric, and neurodegenerative disorders. The molecular and cellular mechanisms underlying the control of NSC homeostasis remain poorly understood. We propose to elucidate the basic mechanisms underlying the genetic control of NSC homeostasis, using Drosophila larval brain type II neuroblasts (NBs) as a model. Drosophila NBs have been instrumental in discovering signaling molecules and cellular mechanisms that are centrally involved in NSC homeostasis. Similar to mammalian NSCs in lineage hierarchy, the type II NB lineages in the Drosophila larval brain contain transit-amplifying intermediate progenitors (IPs), which can generate a vast number of differentiated progenies. Notch signaling is critical for maintaining the homeostasis of type II NB lineages. Inhibition of Notch signaling results in NB not being properly maintained, whereas Notch hyperactivation causes ectopic NB formation and brain tumorigenesis. Notch signaling also regulates the homeostasis of mammalian NSCs, with deregulated N signaling having been linked to brain cancer. The molecular mechanisms by which N signaling regulates NSC homeostasis, however, are not well understood. Previous studies of N signaling in NSCs have focused heavily on canonical N signaling mediated by Suppressor of Hairless [Su(H)]- related transcription factors. However, our studies in the previous funding period have found that a novel non- canonical N signaling pathway operating in the cytosol is also critically involved. Components of this non-canonical N signaling pathway include mitochondrial PTEN-induced kinase 1 (PINK1), mechanistic target of rapamycin complex-2 (mTORC2), and mTORC2 substrate AKT. Clinical significance of this non-canonical N signaling pathway is underscored by our observation that tumor-initiating cancer stem cell (CSC)-like cells in both Drosophila brain tumor models and human GBM samples are particularly sensitive to perturbation of this pathway. Moreover, we found that this non-canonical pathway exerts translational control over mitochondrial oxidative phosphorylation related mRNAs. The goal of this proposal is to move away from the status quo of transcriptional regulation of NSCs by focusing on the newly discovered translational control mechanism in N signaling. Our central hypothesis is that non-canonical N signaling regulates NSC homeostasis through co-translational quality control of mitochondrial mRNAs, thus modulating mitochondrial proteome and function. To test this hypothesis, we propose two Specific Aims. Aim 1 will elucidate how the co-translational quality control pathway mediates the effect of Notch on NSC homeostasis. Aim 2 will dissect the molecular mechanism by which Notch regulates the co-translational quality control process. Upon successful completion of these Aims, we will have generated new mechanistic insights into the control of NSC homeostasis by Notch. We anticipate that this will open up entirely new directions for studying the fundamental roles of Notch in NSC biology, cancer biology, and adult brain function.