Genetic Control of Neural Stem Cell Homeostasis

描述（由申请人提供）：实现神经干细胞（NSC）谱系内的稳态对神经系统发育和维持至关重要。它需要在国家安全理事会的自我更新和差异化之间保持微妙的平衡。神经干细胞内稳态控制的分子和细胞机制仍然知之甚少。阐明这些机制将为神经系统的发育和维持提供新的见解，并为NSC稳态失败导致的疾病（包括脑肿瘤和神经发育，精神病和神经退行性疾病）的分子靶向治疗提供关键。我们建议阐明的基本机制，遗传控制的NSC稳态，果蝇幼虫脑II型成神经细胞（NBs）作为一个模型。果蝇NB在发现信号分子（如Numb和Notch）和细胞机制（如不对称细胞分裂）方面发挥了重要作用，这些机制主要涉及NSC的稳态。与哺乳动物神经干细胞一样，II型果蝇NB产生转运扩增中间祖细胞（IP），这有助于产生大量分化的后代。Notch信号传导对于维持II型NB的“干性”至关重要。Notch信号传导的抑制导致NB命运不能被适当地维持，而异常的Notch激活导致异位NB形成和脑肿瘤发生。Notch在调节NSC稳态中的功能似乎在哺乳动物中是保守的。然而，关于Notch的作用机制及其与Numb的体内关系还有很多需要了解的地方，这仍然是一个谜和有争议的。我们已经发现，经典的Notch信号是必要的，但不是足够的Notch指导的NSC调控，一个新的非经典的Notch信号通路也参与。我们的主要假设是，非经典Notch信号与经典Notch信号协同作用，介导NSC稳态控制的不同方面，并且Numb调节这两种途径。许多基本的问题被提出：什么样的细胞程序做规范和非规范途径调节？这些途径的关键分子靶点是什么？我们能否通过操纵这些关键目标来概括Notch的效果？麻木在这两条途径中扮演什么角色？三个具体目标将有助于解决这些问题。目的1从遗传学和生物化学的角度阐明一条调控神经干细胞稳态的非经典Notch信号通路。目的2验证经典Notch通路和非经典Notch通路协同作用维持NSC稳态的假说。目的3将测试Numb在一种新的蛋白质复合物中起作用以调节经典和非经典Notch途径中的关键下游介质的假设。在成功完成这些目标后，我们将通过Notch和Numb产生对NSC稳态控制的新机制见解。我们预计，这将为研究Numb和Notch在NSC生物学和癌症生物学中的基本作用开辟全新的方向。

DESCRIPTION (provided by applicant): Achieving homeostasis within neural stem cell (NSC) lineages is essential for nervous system development and maintenance. It requires an exquisite balance between NSC self-renewal and differentiation. The molecular and cellular mechanisms underlying the control of NSC homeostasis remain poorly understood. Elucidation of these mechanisms will provide novel insights into the development and maintenance of the nervous system as well as offer the keys to molecularly targeted therapy for diseases resulting from NSC homeostasis failure, including brain tumors and neurodevelopmental, psychiatric, and neurodegenerative disorders. 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 such as Numb and Notch, and cellular mechanisms such as asymmetric cell division, that are centrally involved in NSC homeostasis. Like mammalian NSCs, fly type II NBs generate transit-amplifying intermediate progenitors (IPs), which help to generate a vast number of differentiated progenies. Notch signaling is critical for maintaining the "stemness" of type II NBs. Inhibition of Notch signaling results in NB fate not being properly maintained, whereas aberrant Notch activation causes ectopic NB formation and brain tumorigenesis. The function of Notch in regulating NSC homeostasis appears to be conserved in mammals. However, there is much to be learned about the mechanisms of action of Notch and its in vivo relationship with Numb, which remains enigmatic and controversial. We have found that canonical Notch signaling is necessary but not sufficient for Notch-directed NSC regulation and that a novel non-canonical Notch signaling pathway is also involved. Our main hypothesis is that non-canonical Notch signaling acts coordinately with canonical Notch signaling to mediate distinct aspects of NSC homeostasis control, and that Numb regulates both of these two pathways. Many fundamental questions are raised: What cellular programs do the canonical and the non-canonical pathways regulate? What are the key molecular targets of these pathways? Can we recapitulate the effect of Notch by manipulating these key targets? What roles does Numb play in these two pathways? Three specific aims will help address these questions. Aim 1 will genetically and biochemically elucidate a non-canonical Notch signaling pathway that regulate NSC homeostasis. Aim 2 will test the hypothesis that the non-canonical Notch pathway and the canonical pathway act coordinately to maintain NSC homeostasis. Aim 3 will test the hypothesis that Numb acts in a novel protein complex to regulate key downstream mediators in the canonical and non-canonical Notch pathways. Upon successful completion of these Aims, we will generate new mechanistic insights into the control of NSC homeostasis by Notch and Numb. We anticipate that this will open up entirely new directions for studying the fundamental roles of Numb and Notch in NSC biology and cancer biology.