Mechanisms regulating neural progenitor expansion in the developing brain

项目摘要 最近的人类遗传学研究发现了一类中心体蛋白与小头畸形症之间的联系，这种联系 其特点是与其他器官相比，大脑有选择地缩小尺寸。这项提议的目标是 通过了解有丝分裂进程异常和小头畸形的发病机制，建立小头畸形的新机制 细胞周期重入导致小头畸形症患者神经前体细胞(NPC)减少。这与 该领域中的主导模式，即鼻咽癌细胞对称/不对称分裂的中断会导致小头畸形。 我们将通过关注WDR62(MCPH2；OMIM 604317)来测试这种机制，它是第二大 人类小头畸形的常见遗传原因，编码WD-40重复蛋白。 我们建立了Wdr62缺乏症的亚型小鼠模型，发现突变的小鼠表现出 由于鼻咽癌的减少，大脑的尺寸变小了。Wdr62缺陷的NPC表现出有丝分裂进展延迟和 细胞死亡增加。Wdr62基因缺陷的小鼠胚胎成纤维细胞(MEF)纺锤体稳定性降低 和主轴组件检查点(SAC)激活。Wdr62在身体上和基因上与极光A相互作用， 确定的主轴装配系数。此外，Wdr62还定位于初生纤毛和 调节MEF的纤毛分解和细胞周期重入。Cep170的耗尽，另一个相互作用的Wdr62 蛋白质，也导致纤毛分解，表明Wdr62可能与Cep170一起发挥调节作用 纤毛的生物发生和细胞周期进程。这些初步数据导致了一种新的假设，即Wdr62 通过影响有丝分裂进程和细胞周期调节发育中的脑内神经前体细胞的扩张 重新进入，这是由疾病突变以特定方式中断的。 为了检验这一假说，我们将追求三个具体目标：1)检验Wdr62调控的假说 影响纺锤体完整性的神经前体细胞有丝分裂进程；2)检验假说 Wdr62通过与Cep170共同作用来调节纤毛分解和细胞周期重新进入；3)测试 假设WDR62的个别疾病等位基因损害其特定功能(有丝分裂或纤毛 拆卸)是由于特定的Wdr62相互作用蛋白失去调控所致。总而言之，这些研究将 提高我们对发育中大脑和大脑中神经前体细胞有丝分裂和细胞周期重入调控的理解 为人类小头畸形症的发病机制提供新的见解。

Project Summary Recent human genetic studies identified a link between a class of centrosomal proteins and microcephaly, which is characterized by a selective reduction of brain size in comparison to other organs. The goal of this proposal is to establish a novel mechanism of microcephaly by understanding how dysregulation of mitotic progression and cell cycle re-entry leads to neural progenitor cell (NPC) reduction in microcephaly. This contrasts with the dominant model in the field that disruption of symmetric/asymmetric division of NPCs causes microcephaly. We will test this mechanism by focusing on WDR62 (MCPH2; OMIM 604317), which is the second most common genetic cause of human microcephaly and encodes a WD-40 repeat protein. We created a hypomorphic mouse model of Wdr62 deficiency and found that mutant mice exhibited reduced brain sizes due to a decrease in NPCs. Wdr62 deficient NPCs exhibit mitotic progression delay and an increase in cell death. Wdr62 deficient mouse embryonic fibroblasts (MEFs) showed reduced spindle stability and spindle assembly checkpoint (SAC) activation. Wdr62 physically and genetically interacts with Aurora A, an established spindle assembly factor. In addition, Wdr62 localizes to the basal bodies of primary cilia and regulates cilia disassembly and cell cycle re-entry of MEFs. Depletion of Cep170, another Wdr62 interacting protein, also results in cilia disassembly, suggesting that Wdr62 may function together with Cep170 to regulate cilia biogenesis and cell cycle progression. These preliminary data lead to a novel hypothesis that Wdr62 regulates neural progenitor expansion in the developing brain by influencing mitotic progression and cell cycle re-entry, which are disrupted by disease mutations in a specific manner. To test this hypothesis, three specific aims will be pursued: 1) Test the hypothesis that Wdr62 regulates mitotic progression of neural progenitor cells (NPCs) by influencing spindle integrity; 2) Test the hypothesis that Wdr62 regulates cilia disassembly and cell cycle re-entry by functioning together with Cep170; 3) Test the hypothesis that individual disease alleles of WDR62 compromise its specific functions (mitosis or cilia disassembly) due to loss of regulation of specific Wdr62 interacting proteins. Together, these studies will improve our understanding of mitosis and cell cycle re-entry regulation of NPCs in the developing brain and provide novel insights into mechanisms underlying human microcephaly diseases.