Abstract
OBJECTIVE: To identify the cause of congenital perinuclear cataracts in a Chinese family and its underlying mechanism. METHODS: Family history and clinical data were recorded, and candidate genes were amplified by polymerase chain reaction (PCR) and screened for mutations using direct bidirectional DNA sequencing. The GJA3 gene was acquired from a human lens cDNA library, and the GJA3 mutant was generated by PCR-based site-directed mutagenesis. Connexin localization and gap junction formation were assessed by fluorescence microscopy, and hemichannel functions were analyzed by dye uptake assay. RESULTS: Gene sequencing showed one base pair substitution at position 671 of the GJA3 gene's coding region (c.671A > G), leading to the conversion of the 224th amino acid of the Connexin 46 protein (Cx46), expressed by the GJA3 gene, from histidine to arginine (p.H224R). In stable transfectants, the formation of gap junctions was detected in both wild-type Cx46 (wtCx46) and mutant Cx46H224R transfected HeLa cells, where the Cx46H224R transfected cells exhibited a much higher Propidium Iodide (PI) loading speed than the wtCx46 cells. CONCLUSION: This study was the first to identify the c. 671A > G mutation of the GJA3 gene (p.H224R in Cx46), which leads to the generation of congenital perinuclear cataracts. We suggest that the H224R missense mutation of Cx46 may cause alterations in the activity of the hemichannel, leading to cataract development.