先天性白内障一家系全基因组扫描基因定位及候选基因序列分析

Linkage analysis of a Chinese family with congenital cataract and mutation screening of BFSP1

目的应用全基因组扫描、连锁分析的方法对常染色体显性遗传性先天性白内障（ADCC）一家系进行基因定位、寻找候选基因并进行突变筛查。方法提取该家系成员外周血DNA,进行全基因组扫描。在ABI 3130-avant全自动遗传分析仪上读取370对微卫星标记物的等位基因片段大小,并采用Genescan 3.1和Genotyper 2.0软件进行两点法计算LOD值并构建单体型。根据连锁分析的结果,对该区域内在晶状体中呈高表达,且对维持晶状体纤维细胞的分化状态起重要作用的基因-BFSP1进行直接的序列分析。结果该家系的致病基因位于20p12-20p11.2的13.96 cm区域内。在该区域内的基因-BFSP1全部外显子及外显子与内含子交界处均未发现任何突变。结论首次将一常染色体显性遗传绕核型先天性白内障家系的致病基因定位于20p12-20p11.2的13.96 cm区域内。

Objective Congenital cataract is one of the major causes of blindness in human being, and gene study on congenital cataract is helpful to understand its pathogenesis. This study was to identify the genetic location of the candidate gene by linkage analysis and describe the clinical phenotype in a Chinese family with autosomal dominant congenital cataract （ADCC）. Methods Sixteen patients with ADCC and 26 normal subjects were collected from a Chinese family. A detailed clinical examination was performed for the family members. The genomic DNA of all family members was extracted from peripheral blood leukoeytes. Linkage analysis and genome-wide linkage screening was conducted using fluorescent detection of 370 microsatellite markers representing all autosomes at an average resolution of approximately 10 cm. The polymerase chain reactions were carried out to amplify all 370 mierosatellite markers. The allele sizes were determined on ABI 3130-avant genetic analysis according to an internal size standard and the results were analyzed using Genesean 3.1 and Genotyper 2.0 software. Multipoint LOD scores between the disease status and the marker alleles were calculated using the Linkage software package of Sire Walk 2, Version 3.35. Directly sequence was conducted on affected members of this family to determine the mutation in all exons of BFSP1 gene. The study followed the Helsinki Statement. Results The affected members in the family were born with classic phenotype of zonular ADCC. Linkage analysis showed the markers D20S163, D20S915, D20S152, D20S98, D20S904, D20S875, D20S112, D20S1140, D20S432 co-segregated with the disease locus in all affected members. The maximum Lod Score was 6.02 （D20S904） , so the candidate region of disease gene in the family was located on 13.96 cm between 20p12 -20p11.2. Directly sequence showed no mutations in all exons of BFSP1 gene in this family. Conclusion This is the first report that candidate region in the family is located in 20p12 - 20p11. 2. No mutation in all exons of BFSP1 gene is found in the family. A new disease-causing gene may exist in this family.