Purpose: To screen polymorphisms in complement factor-H (CFH), toll-like receptor 4 (TLR4), and APOE genes as potential risk factors for age-related macular degeneration (AMD) in Indian patients.
Methods: One hundred patients with AMD and 120 normal control subjects were screened for the polymorphisms by restriction digestion and resequencing. Five intragenic SNPs in CFH were screened to generate haplotype data in cases and controls. The data were analyzed in conjunction with data from other populations based on genotype and haplotype frequencies, and odds ratios were computed to estimate the risk of AMD in the different genotypes.
Results: Significant association was noted with the CFH variant (Tyr402His) among AMD cases (P = 1.19 x 10(-7)). Individuals homozygous for the mutant genotype CC had a significantly higher risk (P < 0.0001) of AMD (OR = 11.52; 95% CI 5.05-26.28) than those carrying a single copy of the C allele (OR = 1.51; 95% CI 0.82-2.80), after adjusting for age, gender, and diabetes. Linkage disequilibrium and haplotype analysis at the CFH locus indicated the C-G-T-C-A-G to be a risk haplotype (P = 0.0003). No significant differences were observed in the genotype frequencies of APOE polymorphisms among patients and control subjects (P = 0.76). The carriers of epsilon4 allele had a reduced risk (P = 0.03) of AMD (OR = 0.42, 95% CI 0.19-0.91). TLR4 did not exhibit any association with AMD.
Conclusions: The CFH polymorphism Tyr402His appears indicative of AMD pathogenesis. Diabetes, age, and gender in the presence of the homozygous "CC" genotype in CFH carry an increased risk of AMD. Hence this polymorphism could be used as a potential marker for predictive testing across continents.