Molecular Studies of Brain Malformations

描述(申请人提供)：大脑发育过程中神经元迁移障碍导致无脑型皮质发育不良。脑部肌肉-眼-脑(MEB)疾病的临床表现包括由软脑膜神经元异位引起的多小脑回，推测是由于发育过程中过度迁移所致。MEB病的遗传学基础是POMGNT1基因零突变，该基因编码一种参与蛋白质O-甘露糖型糖基化的糖基转移酶。POMGnT1缺陷导致神经元迁移缺陷的细胞和分子机制尚不清楚。对其他神经元迁移障碍的遗传学分析发现，丝素1、LIS 1和双重皮质素是神经元迁移的关键调节因子。它们参与细胞运动是很容易理解的，因为它们是肌动蛋白结合蛋白或微管相关蛋白。POMGNT1在神经元迁移中的作用令人费解，因为它是一种酶。它将一直令人费解，直到它的底物被确定。总体假设是α-营养不良聚糖是POMGNT1的关键底物，因此POMGNT1的糖基化对于放射状胶质细胞和脑表面基底膜之间的相互作用是必不可少的。在缺乏这种糖基化的情况下，相互作用的中断会导致基底膜、边缘带Cajal-Retzius细胞和放射状胶质细胞的大体形态变化，导致神经元过度迁移。为了直接验证这一假设，我们将建立MEB病的小鼠模型。POMGNT1是否修饰α-营养不良聚糖以及这种修饰的生物学功能将被确定。POMGNT1缺乏对放射状胶质细胞和基底膜相互作用以及对神经元迁移的细胞和分子影响将被检测。此外，POMGNT1修饰的其他潜在候选糖蛋白将通过蛋白质组学方法进行鉴定。这些研究将对蛋白质O-甘露糖糖基化导致神经元迁移障碍的细胞和分子机制以及甘露糖在哺乳动物发育中的基本功能提供深入的认识。

DESCRIPTION (provided by applicant): Disorders of neuronal migration during brain development result in lissencephaly-type cortical dysplasia. The clinical manifestations of muscle-eye-brain (MEB) disease in the brain involve polymicrogyria caused by neuronal ectopia in the leptomeninges that presumably result from over-migration during development. The genetic basis of MEB disease is null mutations in POMGnT1 encoding a glycosyltransferase involved in O-mannose-type glycosylation of proteins. The cellular and molecular mechanisms of POMGnT 1 deficiency leading to defective neuronal migration are unknown. Genetic analyses of other neuronal migration disorders have identified filamin 1, LIS 1 and doublecortin as key regulators of neuronal migration. Their involvement in cell movement is readily understandable, as they are actin binding or microtubule-associated proteins. The involvement of POMGnT1 in neuronal migration is puzzling because it is an enzyme. It will remain puzzling until its substrates are identified. The overall hypothesis is that alpha-dystroglycan is a key substrate of POMGnT1, such that its glycosylation by POMGnT1 is essential for interactions between radial glia and the brain surface basement membrane. Disrupted interactions in the absence of such glycosylation lead to gross morphological changes in the basement membrane, the marginal zone Cajal-Retzius cells, and the radial glia, resulting in overmigration of neurons. To directly test this hypothesis, a mouse model of MEB disease will be generated. Whether POMGnT1 modifies alpha-dystroglycan and the biological functions of such modifications will be determined. The cellular and molecular effects of POMGnT1 deficiency on radial glia and basement membrane interaction and on neuronal migration will be examined. In addition, other potential candidate glycoproteins modified by POMGnT1 will be identified by a proteomic approach. These studies will provide insight into the cellular and molecular pathogenesis of disrupted protein O-mannosyl glycosylation leading to neuronal migration disorders and on the basic functions of mannosyl glycans in mammalian development.