一特殊表型的常染色体显性遗传先天性白内障家系致病基因的筛选与鉴定

Screen and identification of causing-disease gene in a family with a special crystalline autosomal dominant congenital cataract

背景遗传因素是先天性白内障的主要致病因素之一，致病基因的筛查是研究先天性白内障发病分子机制的重要步骤。目的明确一结晶样晶状体混浊的先天性常染色体显性遗传白内障（ADCC）家系的致病基因。方法收集山西省榆社县一个四代先天性结晶样混浊白内障家系22名成员，其中患者10例。在获得知情同意后，该家系成员进行家系调查以确定遗传方式。经裂隙灯显微镜检查和常规眼科临床检查确定表型。采集其中17例家系成员的外周静脉血5ml并提取DNA，ADCC的17个已知致病基因周围选取22个荧光标记的微卫星，通过对微卫星标志物的扩增和基因型分析对该家系进行基因两点连锁分析，并计算对数优势评分（LOD）值。对筛选的候选基因进行直接测序分析。结果该家系患者晶状体混浊表型非常类似，家系分析表明为四代垂直遗传，符合单基因ADCC的特点。基因连锁分析提示，该家系与微卫星D2S325位点和D2S2358位点连锁，最大LOD值分别为1．20（0=0）和0．22（0=0），位于此区域内的CRYGD基因测序后发现一个已经报道的错义突变c．C70A（p．P23T）。结论CRYGD基因P23T突变是该家系结晶样晶状体混浊的致病原因。

Background Inheritance is one of main causing-disease factors in congenital cataract. So the screen of causing-disease gene in congenital cataract patients is a critical step. Objective This survey was to investigate the molecular characteristics of a Chinese pedigree with a special crystalline autosomal dominant congenital cataract（ADCC） in Shanxi province. Methods This study was approved by Ethic Commission of Shanxi Eye Hospital. Informed consent was obtained from each subject before any medical examination. Twenty-two families from a pedigree with special crystalline were included in this study. The family members received regular ophthaimologic and general examinations to rule out any concomitant disorders. Blood samples were obtained to extract the DNA from all the subjects. Twenty-two fluorescent labeled microsatcllites were selected from 17 causing genes of ADCC and amplified and screened for the linkage analysis. LOD was calculated and the candidate gene was directly sequenced. Results Ten individuals with congenital cataract were found in the family with the similar phenotype. The inheritance mode complied with the autosomal dominant pattern. Linkage analysis indicated a gene chain at D2S325 and D2S2358 with the LOD value 1.20（ 0 = 0 ）and 0.22 （0 = 0 ）. A known c. C70A（ p. P23T）missence mutation at the coding region of CRYGD gene was detected by direct sequence. Conclusions A missense mutation P23T of the CRYGD gene cause the autosomal dominant congenital nuclear cataract with the special phenotype.