先天性膜性白内障一家系致病基因的遗传分析

目的 分析一个先天性白内障家系的遗传规律,对其突变基因进行初步研究.方法 选取一先天性膜性白内障家系,对家系成员进行临床检查并采集静脉血.标准饱和酚/氯仿抽提法提取DNA,选取多态性微卫星遗传标记,合成引物,聚合酶链反应,聚丙烯酰胺凝胶电泳,基因分型,等位基因共享分析法对已知候选基因进行排除性定位.结果 该家系为常染色体显性遗传性先天性白内障家系.其致病基因与D22S315联系紧密,重组发生在以D22S303和D22S1167为上下边界的范围内.对该范围内已知的先天性白内障致病基因CRYBB1、CRYBB2、CRYBB3、CRYBA4进行DNA直接测序,未发现突变.结论 该家系致病基因定位于22q11.2～q12.1的2.4 Mbp范围内,其致病基因与已知基因座不同.该范围内可能存在导致先天性膜性白内障的新的致病基因.

Mutation of 22q11.2-q12.1 gene in a family with autosomal dominant congenital membranous cataract

Objective Autosomal dominant congenital cataract (ADCC) is a common heredit disease.Some known genes and mutated loci related to ADCC have been found.The present study provides other disease-causing genes in the ADCC family.This study was to identify the genetic defect in four generations of a Chinese family with autosomal dominant congenital membranous cataracts and demonstrate the functional analysis of a candidate gene in the family.MethodsThe family with hereditary cataract was recruited from the Tianjin Medical University Eye Center.The family history was collected and recorded.Clinical and ophthalmologic examinations were performed on 6 affected and 14 unaffected family members and periphery blood samples were collected from all of the subjects for genomic DNA preparation.The members were genotyped with microsatellite markers at loci associated with cataracts.Multiplex polymerase chain reaction (PCR) was carried out with microsatellite markers near to candidated loci related to congenital cataracts.PCR products from each DNA sample were separated on a polyarcylamide gel and analyzed.Exclusion analysis was performed by allele sharing analysis and gene sequencing.This trail was approved by the Human Research Ethics Committee of this hospital.The oral informed consent was obtained from all of the subjects before the initiation of this trial.ResultsThe hereditary characteristic of this family was in accordance with the autosomal dominant inheritance with a gene penetrance 100%.Affected members of the family were diagnosed with membranous cataracts without other ocular symptom.The disease-causing gene locus were mapped to 22q11.2-q12.1 at a size of about 2.4 Mbp.The multiple-sequence alignments of complete coding region and splice site of CRYBB1,CRYBB2,CRYBB3,CRYBA4 were obtained but no mutation was found in this study.CRYBB1,CRYBB2,CRYBB3,CRYBA4 were screened by directly sequencing.ConclusionAll known ADCC loci have been excluded from the family.Further study should be carried out to screen other relevant genes or loci in patients with ADCC.The pathogenic gene in the family should be identified through extensive scanning of genes,and a new disease-causing gene may exist in this family.