MOLECULAR REGULATION OF NEOCORTICAL NEUROGENESIS

描述（由申请人提供）：啮齿动物和人类自发突变的分析已被证明在确定大脑发育所必需的分子机制方面具有非常重要的价值。最值得注意的是，通过遗传分析和定位克隆，已经确定了皮质神经元迁移所必需的蛋白质。相比之下，已经有一些自发突变，导致识别参与胞质分裂和相关细胞动力学的控制，发生在整个神经发生在脑室表面的途径。胞质分裂的调控在新皮层神经发生中起着重要作用，并可能决定新产生的子细胞的命运。在第一阶段的补助金，我们发现了一种新的突变体，平头，现在已经揭示了一个重要的分子机制，运作，以调节胞质分裂和神经发生的神经元祖细胞。CNS特异性表型的平头突变体的特征在于严重的microcercephaly与不同的神经元细胞类型的相对数量的变化，并在异常的神经元肥大。使用定位克隆策略将平头突变鉴定为位于大鼠和人12号染色体长臂上的Citron激酶基因（CitronK或CitK）中的突变。平头突变是外显子1中的单碱基缺失，导致无义密码子和增殖区中CitronK蛋白表达的缺失。CitronK蛋白集中在VZ表面的粘附功能和胞质分裂沟。我们假设CitK，其中包含多个蛋白质相互作用域，链接命运决定信号与细胞骨架重组在VZ表面。我们建议使用成像实验，体内转染和生化实验的组合，以进一步阐明神经发生所必需的细胞和分子途径。

DESCRIPTION (provided by applicant): Analysis of spontaneous mutations in rodents and humans has proven invaluable in identifying molecular mechanisms essential to brain development. Most notably, proteins essential to patterned migration of cortical neurons have been identified through genetic analyses and positional cloning. In contrast, there have been few spontaneous mutations that have led to the identification of pathways involved in the control of cytokinesis and associated cellular dynamics that occur throughout neurogenesis at the surface of the ventricles. The regulation of cytokinesis plays a central role in neocortical neurogenesis, and may determine the fates of newly generated daughter cells. In the first period of this grant we discovered a novel mutant, flathead, which has now revealed an essential molecular mechanism that operates to regulate cytokinesis and neurogenesis in neuronal progenitors. The CNS-specific phenotype of the flathead mutant is characterized by severe micrencephaly with alterations in the relative numbers of different neuronal cell types, and in abnormal neuronal hypertrophy. A positional cloning strategy was used to identify the flathead mutation as a mutation in the Citron-kinase gene (CitronK or CitK) located on the long arm of rat and human chromosome 12. The flathead mutation is a single base deletion in exon 1 that results in a nonsense codon and absence of CitronK protein expression in proliferative zones. CitronK protein is concentrated at the VZ surface at adherens unctions and cytokinesis furrows. We hypothesize that CitK, which contains multiple protein interaction domains, links fate determining signals with cytoskeletal restructuring at the VZ surface. We propose to use a combination of imaging experiments, in vivo transfection, and biochemical experiments to further elucidate a cellular and molecular pathway necessary for neurogenesis.