Molecular Studies of Brain Malformations

描述（由申请人提供）：脑发育期间神经元迁移障碍导致无脑型皮质发育不良。肌肉-眼-脑（MEB）疾病在大脑中的临床表现涉及由软脑膜中的神经元异位引起的多小回，这可能是由于发育期间的过度迁移所致。MEB疾病的遗传基础是编码参与蛋白质的O-甘露糖型糖基化的糖基转移酶的POMGnT 1中的无效突变。POMGnT 1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分析已经确定细丝蛋白1、LIS 1和双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容易理解的，因为它们是肌动蛋白结合或微管相关蛋白。POMGnT 1参与神经元迁移是令人困惑的，因为它是一种酶。在确定其底物之前，它仍将是一个谜。总体假设是α-肌营养不良聚糖是POMGnT 1的关键底物，因此其通过POMGnT 1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。在不存在这种糖基化的情况下中断的相互作用导致基底膜、边缘区Cajal-Retzius细胞和放射状胶质细胞的总体形态学变化，从而导致神经元的过度迁移。 为了直接检验这一假设，将产生MEB疾病的小鼠模型。将确定POMGnT 1是否修饰α-肌营养不良聚糖以及此类修饰的生物学功能。 POMGnT 1缺陷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查。此外，POMGnT 1修饰的其他潜在候选糖蛋白将通过蛋白质组学方法鉴定。这些研究将提供深入了解破坏蛋白质O-甘露糖基化导致神经元迁移障碍的细胞和分子发病机制，以及甘露糖基聚糖在哺乳动物发育中的基本功能。

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.