Mechanisms regulating neural progenitor expansion in the developing brain

项目摘要 最近的人类遗传学研究确定了一类中心体蛋白与小头畸形之间的联系， 其特征是与其他器官相比，大脑尺寸选择性缩小。这项提案的目的是 通过了解有丝分裂进程的失调以及 细胞周期再进入导致小头畸形中神经祖细胞（NPC）减少。这与 该领域的主导模型是NPC的对称/不对称分裂的破坏导致小头畸形。 我们将通过关注WDR 62（MCPH 2; 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。 我们建立了一个Wdr 62缺陷的亚纯型小鼠模型，发现突变小鼠表现出 由于NPC数量的减少而导致大脑体积的缩小。Wdr 62缺陷型NPC表现出有丝分裂进程延迟， 增加细胞死亡。Wdr 62缺陷型小鼠胚胎成纤维细胞（MEFs）显示纺锤体稳定性降低 和纺锤体组装检查点（SAC）激活。Wdr 62在物理和遗传上与Aurora A相互作用， 确定的主轴装配系数。此外，Wdr 62定位于初级纤毛的基体， 调节纤毛解体和MEFs的细胞周期重新进入。Cep 170的耗尽，另一种Wdr 62相互作用 蛋白质，也导致纤毛解体，这表明Wdr 62可能与Cep 170一起发挥调节作用， 纤毛生物发生和细胞周期进程。这些初步数据导致了一个新的假设，即Wdr 62 通过影响有丝分裂进程和细胞周期来调节发育中的脑中神经祖细胞的扩增 重新进入，这是由疾病突变以特定的方式破坏。 为了检验这一假设，将追求三个具体目标：1）检验Wdr 62调节 通过影响纺锤体的完整性来研究神经祖细胞（NPC）的有丝分裂进程; 2）检验假设 Wdr 62通过与Cep 170共同发挥作用来调节纤毛分解和细胞周期重新进入; 3）测试 假设WDR 62个体疾病等位基因损害其特异性功能（有丝分裂或纤毛 分解），这是由于特定Wdr 62相互作用蛋白的调控丧失。这些研究将 提高我们对发育中大脑中NPC的有丝分裂和细胞周期再进入调节的理解， 为人类小头畸形疾病的潜在机制提供了新的见解。

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.