Deciphering the association of intronic single nucleotide polymorphisms of crystallin gene family with congenital cataract.

Purpose: Introns play an important role in gene regulation and expression. Single nucleotide polymorphisms (SNPs) in introns have the potential to cause disease and alter the genotype-phenotype association. Hence, this study aimed to decipher the association of SNPs in the introns of the crystallin gene in congenital cataracts. Methods: SNPs in the introns of crystallin gene family - CRYAA (rs3788059), CRYAB (rs2070894), CRYBA4 (rs2071861), and CRYBB2 (rs5752083, rs5996863) - were genotyped in 248 participants consisting of 141 congenital cataracts and 107 healthy controls by allele-specific oligonucleotide polymerase chain reaction method. Around 10% of samples for each SNPs were sequenced to confirm the genotypes. The allele, genotype, and haplotype frequency were evaluated by the SHEsis online tool. Results: Using dominant model, the "A" allele of rs3788059 was found to have an increased risk toward congenital cataract development whereas the "G" allele was found to be protective (AA + AG vs. GG; odds ratio [OR] 95% confidence interval [CI] = 3.73 [1.71, 8.15], P = 0.0009). The "A" allele of both rs2070894 (AA + AG vs. GG; OR [95% CI] = 0.49 [0.29, 0.84], P = 0.012) and rs5752083 (AA + AC vs. CC; OR [95% CI] = 0.25 [0.08, 0.76], P = 0.016) were suggested to have a protective role by the dominant model. The A-C-T haplotype (rs2071861, rs5752083, and rs5996863) was found to be a significant risk factor for the development of congenital cataract. Conclusion: Intronic SNPs in crystallin genes may play a role in the predisposition toward congenital cataract. However, the present findings need to be replicated in a large cohort with more number of samples.

Protective association of A-T-T haplotype of DMT1 gene against risk of human age-related nuclear cataract.

BACKGROUND: Age-related cataract (ARC) is profoundly associated with oxidative stress. Iron plays a pivotal role in generating oxidative stress and promoting deleterious irreversible damage to the macromolecules. Divalent metal transporter 1 (DMT1) mediates the uptake of iron into the cell. Aberrant transcript expression of DMT1 gene in lenses of human ARC was reported. The present investigated the genetic association between DMT1 gene polymorphisms and risk of ARC. METHODS: DNA from peripheral blood of ARC subjects (n = 764) and age-matched controls (n = 794) was isolated. Genotyping of three single-nucleotide polymorphisms (SNPs) - rs224589 (C/A), rs1048230 (T/C), and rs2285230 (T/C) - of DMT1 gene was performed by polymerase chain reaction (PCR)-restriction fragment length polymorphism technique. Level of DMT1 transcript expression was determined by quantitative real-time PCR analysis using RNA from lens epithelial and fiber cells. RESULTS: Nuclear cataract showed a higher frequency of CC genotypes (OR = 1.40; 95%CI = 1.01-1.95; p = 0.04) of SNP rs224589 and a significantly lower frequency of A-T-T haplotype (OR = 0.63; 95%CI = 0.42-0.92; p = 0.02) than that of controls. The A-T-T haplotype demonstrated a dominant protective effect against disease risk when compared to the more common haplotype (C-T-T) (p = 0.01). The haplotype pairs C-T-T/C-T-T and A-C-C/A-C-C showed higher level of transcript expression of DMT1 than C-T-T/A-T-T haplotype pair (p < 0.05). Further, a novel genetic variation (c.1328A>G; p.N443S) in exon 3 of DMT1 gene was observed in a subject with nuclear cataract. CONCLUSIONS: The results highlighted a protective association of A-T-T haplotype against the risk of ARC.