Molecular Studies of Brain Malformations

描述(申请人提供)：先天性肌营养不良症(CMD)伴有脑畸形，如肌肉-眼-脑疾病(MEB)是以皮质发育不良、眼部异常和肌肉营养不良为特征的遗传性疾病。致病基因的蛋白质产物编码与蛋白质糖基化有关的糖基转移酶。特别重要的是通过糖甘露糖O-连接到蛋白质上的多糖。O-甘露糖聚糖是由POMT1和POMT2将甘露糖加到丝氨酸/苏氨酸残基上，然后由POMGNT1将N-乙酰氨基葡萄糖加到甘露糖上形成的。这些基因缺陷导致1-营养不良糖链低糖基化，并产生CMD表型。大基因突变会导致相似的表型。虽然Large的生化功能尚不清楚，但在其他CMD患者分离的细胞中，Large过表达高糖基化1-DystroGan，提示Large可能被开发为CMD的基因治疗药物。假设是大分子合成一种有别于O-甘露糖基的多糖(S)。研究的具体目的是：1.大分子在营养不良糖链糖基化和功能中的作用。2.大鼠体内基因治疗的可行性。通过表征大功能丧失和大功能获得下的1-Dystroglan的碳水化合物分布，所提出的研究将为大的分子功能提供新的和重要的见解。此外，它还将在体内测试将Large用作POMGNT1缺乏症的基因治疗剂的可行性。公共卫生相关性：先天性肌营养不良合并脑畸形是由涉及蛋白质糖基化的糖基转移酶的基因突变引起的。本项目研究糖基化缺陷引起的脑畸形的分子和细胞机制，以及将一种酶用作先天性肌营养不良的治疗剂的可行性。

DESCRIPTION (provided by applicant): Congenital muscular dystrophies (CMD) with brain malformations such as muscle-eye- brain disease (MEB) are genetic diseases characterized by cortical dysplasia, ocular abnormalities, and muscular dystrophy. The protein products of the offending genes encode glycosyltransferases involved in glycosylation of proteins. Of particular importance are glycans O-linked to proteins by the sugar mannose. O-mannosyl glycans are formed by the addition of mannose to Ser/Thr residues by POMT1 and POMT2, followed by the 21, 2 addition of N-acetylglucosamine to the mannose by POMGnT1. Genetic deficiencies of these lead to 1-dystroglycan hypoglycosylation and produce CMD phenotypes. Mutations in the gene Large cause similar phenotypes. While the biochemical functions of Large are unknown, overexpression of Large can hyperglycosylate 1-dystroglycan in cells isolated from other CMD patients, suggesting that Large may be developed as a therapeutic agent for gene therapy of CMD. The hypothesis is that Large synthesizes a glycan(s) distinct from O-mannosyl glycans. The specific aims are to investigate: 1. The roles of Large in dystroglycan glycosylation and function. 2. The feasibility of using Large in gene therapy in vivo. By characterizing the carbohydrate profiles of 1-dystroglycan under Large loss- and gain-of-functions, the proposed research will provide new and important insights into the molecular functions of Large. In addition, it will test the feasibility of using Large as a gene therapeutic agent for the POMGnT1 deficiency in vivo. PUBLIC HEALTH RELEVANCE: Congenital muscular dystrophies with brain malformations are caused by genetic mutations to glycosyltransferases involved in protein glycosylation. This project studies the molecular and cellular mechanisms of brain malformations caused by defective glycosylation and the feasibility of using an enzyme as a therapeutic agent in congenital muscular dystrophies.