The Lis1-Nde1 pathway in cerebral cortical development

描述（由申请人提供）：大脑皮质发育性遗传畸形是临床上很大一部分癫痫和智力低下病例的基础。了解这些发育障碍的一个有力工具是分析它们的致病基因。已知LIS1基因的杂合突变可导致无脑畸形（平滑脑），这是一种严重的神经遗传综合征，表现为顽固性癫痫、深度智力迟钝和婴儿早期死亡。LIS1基因编码一种没有明显内在酶活性的细胞质蛋白；其分子和细胞功能可能通过蛋白-蛋白相互作用起作用。我们发现LIS1在物理上和功能上都与Nde1相互作用。通过分析Lis1-Nde1双突变小鼠的等位基因序列，我们发现Lis1和Nde1在调节神经祖细胞的自我更新和分化中形成了剂量依赖性复合物。Lis1-Nde1双重功能突变缺失导致大脑皮层神经发生时神经祖细胞出现严重的有丝分裂、形态和粘附缺陷，导致大脑皮层体积缩小80%以上，皮层神经元严重解体。我们建议在Specific Aim 1中对Lis1和Nde1突变小鼠的皮质发育缺陷进行详细分析，以了解神经祖细胞的增殖自我更新和神经源性分化是如何受到其基本结构特征（如形态学、有丝分裂模式、侧粘连和细胞结构组织）的控制的。我们还将通过研究培养物中的Lis1-Nde1突变体祖细胞和分析Nde1结合蛋白，探索特异性靶2中Lis1-Nde1复合物控制神经发生的细胞分子机制。这项工作将有助于理解Lis1- Nde1通路对皮层神经发生的分子调控，并将对大脑皮层发育的机制以及无脑畸形和其他遗传性皮质畸形疾病的发病机制有更广泛的了解。

DESCRIPTION (provided by applicant): Developmental genetic malformations of the cerebral cortex underlie a large fraction of clinical cases of epilepsy and mental retardation. A powerful tool for understanding these developmental disorders is to analyze their causative genes. Heterozygous mutations of the LIS1 gene are known to cause lissencephaly (smooth brain), a severe neurogenetic syndrome manifested by intractable epilepsy, profound mental retardation and early infantile death. LIS1 gene encodes a cytoplasmic protein with no apparent intrinsic enzymatic activity; its molecular and cellular function may act via protein-protein interactions. We show that LIS1 interacts with Nde1 both physically and functionally. By analyzing an allelic series of Lis1-Nde1 double mutant mice, we demonstrated that Lis1 and Nde1 form a dosage dependent complex in regulating the self-renewal and differentiation of neural progenitors. Lis1-Nde1 double loss of functional mutations resulted in severe mitotic, morphological and adhesion defects of neural progenitors at the onset of cerebral cortical neurogenesis, leading to an over 80% reduction in the size of the cerebral cortex and severe disorganizations of cortical neurons. We propose to perform detailed analyses on cortical developmental defects of Lis1 and Nde1 mutant mice in Specific Aim 1 to understand how the proliferative self-renewal and the neurogenic differentiation of neural progenitors are controlled by their basic structural features such as morphology, mitotic pattern, lateral adhesions and cytoarchitectural organizations. We will also explore the cell molecular mechanisms that underlie the neurogenesis control by the Lis1-Nde1 complex in Specific Aim 2 through studying Lis1- Nde1 mutant progenitors in cultures and analyzing Nde1 binding proteins. The proposed work will help to understand the molecular control of cortical neurogenesis by the Lis1- Nde1 pathway, and will also gain a broader insight into mechanisms governing cerebral cortex development as well as pathogenesis of lissencephaly and other genetic cortical malformation diseases. PUBLIC HEALTH RELEVANCE: Mutations of the LIS1 gene cause lissencephaly syndrome (smooth brain), a severe developmental genetic disorder with a malformed cerebral cortex, intractable epilepsy and profound mental retardation. The proposal outlines combined mouse genetic and cell biological experiments to study the function of LIS1 and its associated Nde1 genes in regulating the self- renewal and neurogenesis during cerebral cortical development.