A potential novel role of the R36P mutation in CRYGD in congenial cataract.

Purpose: Congenital cataract is an important cause of visual impairment in childhood. Our previous study reported that the c.110G>C (p.R36P) mutation in the γD-crystallin gene (CRYGD) was associated with congenital cataract in a Chinese family. This study aimed to investigate the potential underlying mechanism through which the p.R36P mutation leads to congenital cataract.

Methods: Plasmids encoding wide-type human γD-crystallin and the mutant R36P γD-crystallin were transfected into HEK293T and SRA01/04 cells. Protein expression levels, including total, soluble, and insoluble fractions, were quantified by Western blotting. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to assess the mRNA expression of other crystallin genes. Cell viability and apoptosis were evaluated using the CCK-8 assay and flow cytometry, respectively.

Results: The total protein, especially the soluble fraction, was significantly reduced in the R36P mutant, while the insoluble part remained unaffected. The decrease of soluble R36P γD-crystallin could not be rescued by the proteinase inhibitor MG132. The mRNA expression of the R36P mutation was lower, but other crystallin RNAs were unchanged. Cell viability was slightly decreased (11%, p<0.05), and cell apoptosis was not significantly increased (12%, p=0.31).

Conclusions: The significant decrease in soluble R36P γD-crystallin may represent a novel mechanism underlying congenital cataract caused by CRYGD gene mutation.