Biosynthetic pathway of corneal keratan sulfate

描述（由申请人提供）：硫酸角聚糖蛋白多糖是角膜基质的主要成分之一，约占角膜总厚度的90%，对维持角膜透明度具有重要作用。黄斑性角膜营养不良（MCD）是一种遗传性眼病，患者的角膜基质呈斑点状混浊。由于角膜混浊导致失明，患者最终需要接受角膜移植手术。通过对MCD的碳水化合物硫转移酶基因CHST6的研究，以及该基因产物人角膜GlcNAc 6-O硫转移酶（hCGn6ST）的功能分析，我们认为hCGn6ST参与了角膜中硫酸角蛋白碳水化合物的磺化。

DESCRIPTION (provided by applicant): Keratan sulfate proteoglycan is one of the major component of the corneal stroma, which composes about 90% of the total corneal thickness, and is important to maintain corneal transparency. Macular corneal dystrophy (MCD) is a hereditary eye disease, of which the patients show spotted opacity in their corneal stroma. The patients eventually need to be subjected to keratoplasty because of blindness by cornea clouding. Based on the studies of a carbohydrate sulfotransferase gene, CHST6, which is responsible for MCD, and the functional analysis of the gene product named human corneal GlcNAc 6-O sulfotransferase (hCGn6ST), we concluded that hCGn6ST is involved in the sulfation of keratan sulfate carbohydrate in the cornea. From these findings, we hypothesize that MCD phenotype is caused by the accumulation of unsulfated keratan sulfate proteoglycan, which is produced by the corneal cells lacking hCGn6ST activity, in the corneal tissue. We also hypothesize the presence of a corneal tissue-specific gene regulatory element(s) in CHST6 and mutations on the element result in the disruption of CHST6 expression in the corneal tissue. To address these issues, we propose the following specific aims; 1) To establish biosynthetic mechanism of corneal keratan sulfate 2) To identify the corneal tissue-specific gene regulatory element in CHST6 3) To produce the gene knockout mouse that is an animal model of MCD in human These results will provide us with information upon the involvement of keratan sulfate carbohydrate in the maintenance of the corneal transparency. Data obtained from this project are expected to form the basis for further clinical applications for MCD and the other corneal diseases through tissue engineering, medication and gene therapy.