Identification of a GJA3 mutation in a Chinese family with congenital nuclear cataract using exome sequencing

Congenital cataract, a clinically and genetically heterogeneous lens disorder is defined as any opacity of the lens presented from birth and is responsible for approximately 10% of worldwide childhood poor vision or blindness. To identify the genetic defect responsible for congenital nuclear cataract in a four-generation Chinese Han family, exome and direct Sanger sequencings were conducted and a missense variant c.139G>A (p.D47N) in the gap junction protein-alpha 3 gene (GJA3) was identified. The variant co-segregated with patients of the family and was not observed in unaffected family members or normal controls. The above findings indicated that the variant was a pathogenic mutation. The mutation p.D47N was found in the first extracellular loop (El) domain of GJA3 protein. Our data suggest that exome sequencing is a powerful tool to discover mutation(s) in cataract,. a disorder with high genetic heterogeneity. Our findings may also provide new insights into the cause and diagnosis of congenital nuclear cataract and have implications for genetic counseling.