Identification of genetic mutation in a Chinese pedigree with congenital cataract by whole-exome sequencing

Background

Genetic mutation remains to be the most common cause of congenital cataract.Whole exon sequencing technology is an ideal method to detect the pathogenic gene mutations.

Objective

This study was to identify the pathogenic gene in a Chinese autosomal dominant congenital cataract (ADCC) family by whole-exome sequencing.

Methods

This study complied with Helsinki Declaration and the protocol was approved by Ethic Committee of Peking University Third Hospital.Informed consent was obtained from each subject before any medical examination.A cross-sectional study was designed.A Chinese ADCC family with 4 generations and 48 members were enrolled in Peking University Third Hospital, of which Ⅰ1 and Ⅰ2 died.The periphery blood of 8-10 ml was collected from each member of Ⅱ, Ⅲ and Ⅳ generations for the high throughput sequencing of genes using whole exon trapping and new sequencing technology, and the sequencing results were compared with the data of human HA PMAP8, dbSNP130 and 1000 Genome Project database.The synonymous mutation was filtered after reported common variants, and the false positive results of explicit sequencing were finally excluded by Sanger sequencing and then the candidate genes were identified.The mutation genes were screened to determine the pathogenic gene of this ADCC family.

Results

Eleven ADCC patients were found in this family, and the patients distributed in each generation with an equal chance for involvement in male and female subjects, which conformed to an autosomal dominant inheritance pattern.All the patients were nuclear cataract.Genome-wide whole-exome sequencing found that major intrinsic protein (MIP) gene was known genes of ADCC in initially identified candidate genes, so the Sanger was used to verify the MIP gene.The heterozygous mutation of MIP gene (chr12: 56845250 C>T) appeared to be the pathogenic cause of this ADCC family.The mutation occurred in the splice sites of the gene, resulting in the fourth exon coded-61 amino acids are replaced by leucine, histidine and serine, which lead to the abnormal truncated proteins.

Conclusions

The heterozygous mutation of MIP gene is the molecular pathogenesis of this Chinese ADCC family.

Pedigree; Cataract/genetics; Membrane glycoproteins/genetics; Mutation/genetics; Aquaporins/genetics; Alternative splicing/genetics; Autosomal dominant; Whole-exome sequencing; Major intrinsic protein/genetics; Chinese