Mutation screening of γ-crystallin gene in congenital cataract patients from North India

The present study screened eight families (comprising 25 affected and unaffected individuals, along with ten unrelated controls) to identify known and potentially novel mutations in the human γ-crystallin (CRYG) genes using Sanger bidirectional sequencing.

A hospital-based cross-sectional study was conducted to assess genetic mutations associated with congenital cataract. Clinical data and family history of the patients attending the hospital were recorded. Peripheral blood (2-3 ml) was collected from affected and unaffected family members having congenital cataract. Genomic DNA was extracted, and the candidate genes were amplified using gene specific primers. The polymerase chain reaction products were sequenced bidirectionally to analyze the cosegregation of the genotype with the disease phenotype, and the sequences were compared with NCBI reference sequences.

Analysis of families with inherited cataract revealed two reported single-nucleotide polymorphisms (SNPs) associated with congenital cataract, one in the promoter region of CRYGB gene (c.-47T > C) and the other one in the exon 2 of CRYGD (c.51T>C). One mutation (c.24G>C, p.Glu8Asp) was observed in CRYGD cosegregating with the lamellar cataract in the family. No unaffected family member or healthy unrelated control was identified to have the mutation.

The association of rs2289917 (c.-47T>C) with inherited cataract substantiates the previous findings. Earlier studies from other regions of India report that a putative Ikaros1 binding site between the TATA box and the transcription start site is destroyed by c.-47T>C nucleotide change in CRYGB. Conclusion: Thus, the rs2289917 risk allele was found to have a substantial association with an elevated risk of congenital cataract.