Motor Proteins in Brain Development

描述(申请人提供)：新皮质神经发生和迁移缺陷会导致严重的大脑发育疾病。导致无脑(平滑大脑)的突变Lis1是第一个被发现的神经元迁移基因。Lis1在细胞质动力蛋白途径中发挥作用，表明微管运动蛋白在脑发育中发挥作用。在这笔资金支持的早期工作中，我们确定了神经发生和迁移中需要多个离散的Lis1和dynein阶段，导致了经典(I型)无脑的细胞基础的综合模型。我们还发现了长时间神秘的细胞周期依赖的动间核迁移(INM)所必需的Lis1，这是神经上皮细胞和放射状胶质前体细胞(RGPC)行为的一般特征。我们进一步确定，INM需要反向的微管马达蛋白、正端定向的非常规Kif1a运动蛋白和细胞质动力蛋白的活性。这一模型似乎解释了INM的基本机制，并应允许我们进一步解决有关其功能和目的的基本和长期存在的问题。其具体目的是确定Kif1a的核转运机制；确定特异性抑制基础和顶端INM如何影响细胞周期进程和细胞命运；以及确定使用小分子蛋白激酶抑制剂和其他试剂控制INM细胞周期的机制。这些问题对于了解大脑的大小、组成和组织是如何控制的，以及在正常或肿瘤条件下干细胞增殖是如何调控的具有重要的意义。对负责INM的基因的分析和小分子细胞周期抑制剂的使用也将确定在大脑发育早期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.