α-抗肌萎缩相关糖蛋白病α-DG的氧位糖基化基因突变分析与功能研究

α-抗肌萎缩相关糖蛋白病表现为肌营养不良、脑和眼发育畸形，存在α-DG蛋白的糖基化缺陷，具临床和遗传异质性，严重影响儿童发育，具体发病机制不清。在前基金(30600683)支持下我们证实其中的福山型先天性肌营养不良(FCMD)的基因产物fukutin与肌-眼-脑病的基因产物POMGnT1形成复合体并调节其酶活性，推测fukutin可能起分子伴侣作用，并对该类疾病行分子病理及基因诊断，在国际上首次报道日本以外FCMD。在前期证实中国患儿POMGnT1基因新突变、突变体酶活性缺陷、在亚细胞内定位错误的基础上，本课题拟继续分析患儿α-DG的氧位糖基化基因，研究其皮肤成纤维细胞POMGnT1酶活性和α-DG糖链，利用转基因细胞模型观察突变体亚细胞定位、酶活性，探讨fukutin的调节作用及如何影响酶产物α-DG的糖基化和配体结合活性，这不仅为研究该类疾病的发病机制提供线索，对治疗也可能开辟新途径。

Dystroglycanopathy is a group of muscular dystrophies with a reduction in α-dystroglycan (α-DG)' ligand-binding capacity resulting from its aberrant O-glycosylation, which has clinical and genetic heterogeneity, manifested with muscular dystrophy, brain and eye abnormalities. The exact glycan synthesis and modification pathways involved, as well as their role in ligand binding, remain only partially characterized. Among them, the function of Fukuyama type congenital muscular dystrophy(FCMD)'s gene product-fukutin, remains unknown. Under the previous grant of National Natural Science Foundation of China(30600683), we have demonstrated that fukutin forms a complex with muscle-eye-brain disease's gene product-O-linked mannose ?1, 2-N-acetylglucosaminyltransferase 1 (POMGnT1) and may modulate its enzymatic activity, as well as diagnosed a lot of such kind of Chinese patients based on molelular pathology and gene mutation analysis. We firstly report FCMD patient out side of Japan in the world. Based on the early work of identifying loss of enzyme activity and mislocalization of POMGnT1 protein by novel disease-causing mutation in Chinese patient, this project plans to do gene mutation analysis in our α-dystroglycanopathy patients continually. At the same time, to assay the enzyme activity from cultured patient's skin fibroblast and analysis of glycan of α-DG. To observe the subcellular localization and enzyme activity change and the relationship between fukutin and the mutant type POMGnT1 in order to investigate their interaction and influence to α-DG ligand-binding activity. This can not only provide some clues to the pathogenesis of α-dystroglycanopathy, but also develop some new path to the therapy.