先天性核性白内障家系致病基因的定位与候选基因突变检测

Gene mapping and mutation detection in a family with congenital nuclear cataract

目的对中国一常染色体显性遗传性先天性核性白内障家系进行致病基因的定位与候选基因突变检测。方法实验研究。采集家系成员的外周静脉血，提取基因组DNA。用约400个中密度微卫星标记进行基因扫描，平均遗传距离10厘摩（cM）。利用LINKAGE软件包进行连锁分析。在阳性定位区域内选取更为精细的微卫星标记进行精细定位。利用CYRILLIC软件进行单体型分析，确定候选基闪所在染色体区域。候选基因直接测序检测基因突变。结果两点间连锁分析在微卫旱标记D2S325处获得最大对数优势计分（LOD）值Zmax=2．29（θmax=0．00）。精细定位和单体型分析将致病基因定位于微卫星标记D2S117和D2S2382之间，遗传距离约19．04cM，染色体位置为2q32．3-q35。候选基因直接测序发现CRYGC基因第3外显子第470碱基一个G—A的点突变。结论本研究将我国一个先天性核性白内障家系的致病基因定位于2号染色体2q32．3-q35约19．04cM区域内，并在CRYGC基因发现一个新的点突变与此家系共分离。

Objective To map and detect the gene responsible for congenital nuclear cataract in a Chinese family. Methods Genomic DNA was extracted from the peripheral blood samples of members of the pedigree. Gene scan was performed using approximately 400 microsatellite markers spaced at about 10 cM intervals （ABI）. Linkage analysis was carried out using a Linkage software package. Additional microsatellitc markers for the positive region were selected for precise targeting, and haplotype data were processed using Cyrillic software to define the region of the disease gene. Mutation detection was carried out by sequencing candidate genes. Results Suggestive evidence of linkage was detected at marker D2S325 （LOD score [Z] = 2. 29, recombination fraction [θ] = 0. 00）. Precise targeting and haplotype analysis traced the disease gene to a 19.04 cM region bounded by D2S117 and D2S2382 on chromosome 2q32.3- q35. Direct sequencing of the candidate gene cluster revealed a G→A transversion in exon 3 of CRYGC. Conclusions The present study has identified a novel nonsense mutation in CRYGC associated with congenital nuclear cataracts in a Chinese family.