Mutation analysis of connexin 50 gene among Iranian families with autosomal dominant cataracts

OBJECTIVES Childhood cataract is a genetically heterogeneous eye disorder that results in visual impairment. The aim of this study was to identify the genetic mutations of connexin 50 gene among Iranian families suffered from autosomal dominant congenital cataracts (ADCC). MATERIALS AND METHODS Families, having at least two members with bilateral familial congenital cataract, were selected for the study. Probands were evaluated by detailed ophthalmologist's examination, and the pedigree analysis was performed. PCR amplifications were performed corresponding to coding region and intron-exon boundaries of GJA8, a candidate gene responsible for ADCC. PCR products were subjected to bidirectional sequencing, and the co-segregation of identified mutations was examined and finally, the impact of identified mutations on biological functions of GJA8 was predicted by in silico examination. RESULTS Three different genetic alterations, including c.130G>A (p.V44M), c.301G>T (p.R101L) and c.134G>T (p.W45L) in GJA8 gene were detected among three probands. Two identified mutations, W45L and V44M have been already reported, while the R101L is a novel mutation and its co-segregation was examined. This mutation was exclusively detected in the ADCC and could not be found among the healthy control group. The result of bioinformatic studies of R101L mutation predicted that this amino acid substitution within GJA8 could be a disease-afflicting mutation due to its potential effect on the protein structure and biological function. CONCLUSION Our results suggest that mutations of lens connexin genes such as GJA8 gene could be one of the major mechanisms of cataract development, at least in a significant proportion of Iranian patients with ADCC.