中国北方一常染色体显性遗传先天性核性白内障家系CRYGD基因突变的鉴定  

A recurrent mutation of CRYGD gene in a northern Chinese family with autosomal dominant congenital nuclear cataract

作　　者：张晓慧[1] 刘卫华[2] 董冰[1] 陈洁琼[1] 李杨[1] 

机构地区：[1]首都医科大学附属北京同仁医院北京同仁眼科中心北京市眼科研究所眼科学与视觉科学北京市重点实验室,北京100005 [2]首都医科大学附属北京同仁医院北京同仁眼科中心眼科学与视觉科学北京市重点实验室,北京100730

出　　处：《中华实验眼科杂志》2015年第8期722-726,共5页Chinese Journal Of Experimental Ophthalmology

基　　金：北京市卫生系统高层次卫生技术人才学科带头人培养计划项目（2013-2-021）

摘　　要：背景 先天性白内障是儿童致盲的主要原因之一,约1/3的先天性白内障由遗传因素引起,多为常染色体显性遗传,目前确定至少26个基因为常染色体显性遗传先天性白内障（ADCC）的致病基因,发现的致病基因突变已超过100种.目的 明确一ADCC家系的致病基因突变.方法 对2011年1月在北京同仁医院就诊的一来自河北的汉族ADCC家系进行分析,在获得受检者知情同意后,对所有家系成员进行详细的眼科检查并采集外周静脉血各5 ml,提取全基因组DNA.在已知的17个ADCC致病基因周围选取21个荧光标记的微卫星,经多重PCR扩增后进行连锁分析,两点法计算LOD值.对候选基因进行DNA直接测序分析,用ProtScale软件对基因突变前后蛋白局部的疏水性进行分析.用限制性片段长度多态性（RFLP）方法对所有家系成员及100个正常对照者进行基因突变共分离分析.结果 该家系共4代20名成员,其中患者9例,连续4代均有患者发病,符合常染色体显性遗传特征.临床检查证实9例患者均为双眼晶状体核性混浊.连锁分析发现微卫星D2S325和D2S2358与该家系中所有患者均连锁,重组分数（θ）为0时D2S325获得最大LOD值,为4.68.对位于D2S325附近的CRYGC和CR YGD基因进行DNA直接测序,发现CRYGD基因cDNA第127位一已知错义突变（c.T127C）,导致编码蛋白第43位色氨酸变为精氨酸（p.W43R）.ProtScale软件预测突变后的CRYGD蛋白第43位及其周围氨基酸疏水性明显增加.该突变与家系内所有患者表型共分离,家系中表型正常的成员及100名正常对照者均未发现此突变.结论 CRYGD基因c.T127C突变是该ADCC家系的致病基因突变,蛋白局部疏水性增加造成的空间结构异常可能是引起该ADCC家系发病的主要原因.Background Congenital cataract is a major cause for blindness of childhood.Genetic gene mutation accounts for almost 1/3 of congenital cataract patients.The most common inheritance type is autosomal dominant congenital cataract （ADCC）.Over 100 mutations in 26 genes have been found to be associated with ADCC.Objective This study was to identify the disease-causing gene mutation in a family with ADCC.Methods This study was approved by Ethic Committee of Beijing Tongren Hospital and followed Declaration of Helsinki.A northern Chinese family with autosomal dominant congenital nuclear cataract was entrolled in Beijing Tongren Hospital in January 2011.Ocular examinations were performed and periphery blood specimens were collected from each family member under the informed consent.Genomic DNA was extracted.Twenty-one microsatellite markers around 17 ADCC genes were selected for linkage analysis,and two-point LOD score was calculated.CRYGC gene and CRYGD gene were amplified and screened for mutations using direct sequencing.ProtScale software was used to analyze the changes of hydrophobicity of the mutated protein.Co-segregation of the observed change with the disease phenotype was further detected by restriction fragment length polymorphism （RFLP）.Results This family included 20 members of 4 generations,and 9 patients were examined in serial 4 passages,which conformed to autosomal dominant inheritance pattern.Clinical examination revealed binocular congenital nuclear cataract in the 9 patients.Maximum two-point LOD score was 4.68 at marker D2S325 （θ=0）.A known T→C change at position 127 of cDNA sequence was found by mutations screening of CRYGD gene.ProtScale programs showed an obvious increase of the local hydrophobicity in the mutant protein.RFLP results indicated that this missense mutation co-segregated with affected members of the family,but was absent in unaffected members and 100 unrelated controls.Conclusions c.T127C mutation of CRYGD gene appears to be the molecular pathogenesis of this ADCC fami

关 键 词：先天性白内障 白内障/遗传学 DNA突变分析 晶状体核/病理 家系谱 γ-晶状体蛋白/遗传 基因突变 中国人 

分 类 号：R776.1[医药卫生—眼科]