Motor Proteins in Brain Development

描述（申请人提供）：新皮质神经发生和迁移缺陷导致严重的脑部发育疾病。LIS1是第一个被发现的神经元迁移基因，它的突变会导致无裂脑畸形（光滑的大脑）。LIS1在细胞质动力蛋白通路中起作用，表明微管运动蛋白在脑发育中起作用。在该基金支持的早期工作中，我们确定了神经发生和迁移中需要LIS1和动力蛋白的多个离散阶段，从而建立了典型（I型）无脑畸形的细胞基础的综合模型。我们还发现LIS1是长期神秘的细胞周期依赖的相互动力学核迁移（INM）所必需的，INM是神经上皮和放射状胶质祖细胞（RGPC）行为的一般特征。我们进一步确定INM需要相反方向的微管运动蛋白、正端定向的非常规运动蛋白Kif1a和细胞质动力蛋白的活性。这一模式似乎解释了INM的基本机制，并应使我们能够进一步解决有关其功能和目的的基本和长期存在的问题。具体目的是确定Kif1a的核转运机制；确定基底和根尖INM的特异性抑制如何影响细胞周期进程和细胞命运；并利用小分子蛋白激酶抑制剂和其他试剂确定INM细胞周期控制的机制。这些问题对于理解大脑的大小、组成和组织是如何被控制的，以及干细胞增殖在正常或肿瘤条件下是如何被调节的具有重要意义。对INM基因的分析和小分子细胞周期抑制剂的使用也将确定在早期大脑发育过程中调节神经发生和迁移的潜在靶点。

DESCRIPTION (provided by applicant): Defects in neocortical neurogenesis and migration cause severe brain developmental disease. LIS1, mutations in which cause lissencephaly (smooth brain), was the first neuronal migration gene to be identified. LIS1 functions in the cytoplasmic dynein pathway, indicating that microtubule motor proteins play a role in brain development. In earlier work supported by this grant we identified multiple discrete LIS1- and dynein- requiring stages in neurogenesis and migration, leading to a comprehensive model for the cellular basis of classical (type I) lissencephaly. We also found LIS1 to be required for the long-mysterious cell-cycle- dependent interkinetic nuclear migration (INM), a general feature of neuroepithelial and radial glial progenitor cell (RGPC) behavior. We have determined further that INM requires the activity of opposite-directed microtubule motor proteins, the plus end-directed unconventional kinesin Kif1a and cytoplasmic dynein. This model appears to explain the underlying mechanism for INM, and should allow us to address further basic and long-standing questions regarding its function and purpose. The Specific Aims are to determine the mechanism of nuclear transport by Kif1a; to determine how specific inhibition of basal and apical INM affect cell cycle progression and cell fate; and to determine the mechanisms for cell cycle control of INM using small molecule protein kinase inhibitors and other reagents. These issues have important implications for understanding how brain size, composition, and organization are controlled, and how stem cell proliferation is regulated under normal or neoplastic conditions. The analysis of genes responsible for INM and the use of small molecule cell cycle inhibitors will also identify potential targets for modulating neurogenesis and migration during early brain development.