Evaluation of the influence of chronic low-dose radiation on DNA repair gene polymorphisms [, , ] in individuals from normal and high level natural radiation areas of Kerala Coast.

Single Nucleotide Polymorphisms (SNPs) at DNA repair genes are considered as potential biomarkers of radio-sensitivity. The coastal belt of Kerala in south west India has a patchy distribution of monazite in its beach sand that contains Th-232 and its decay products. Thus, radiation levels in this area vary from <1.0mGy to 45.0mGy/year. The areas with external gamma radiation dose >1.5mGy/year are considered as High-Level Natural Radiation Areas (HLNRA) and ≤ 1.5mGy/year are Normal Level Natural Radiation Area (NLNRA). In the present study, an attempt was made to evaluate the influence of chronic low dose radiation exposure on DNA repair gene polymorphisms in NLNRA and HLNRA population of Kerala coast. Genomic DNA was isolated from venous blood samples of 246 random, healthy individuals (NLNRA,  = 104; HLNRA,  = 142) and genotyping of five SNPs such as X-ray repair cross complementing 1(), X-ray repair cross complementing 3 (], Protein kinase, DNA-activated, catalytic subunit () (X-ray repair cross-complementing group 7, ), nei like DNA glycosylase 1 () and DNA ligase 1 () was carried out using PCR based restriction fragment length polymorphism (PCR-RFLP) followed by silver staining. Our results showed no significant difference in genotype frequencies in HLNRA vs NLNRA at three of the five SNPs studied i.e. (χ = 5.85,  = .054), (χ = 0.71,  = .339), ( G/T) (χ = 3.72,  = .156), whereas significant difference was observed at (χ =8.71,  = .013) and A/C (χ = 7.66,  = .022). The odds of heterozygote to homozygote genotypes in HLNRA relative to NLNRA at Arg399Gln (OR = 1.96, 95% CI: 1.13-3.40), Thr241Met (OR = 0.73, 95% CI: 0.41-1.31), (OR = 0.81; 95% CI: 0.48-1.38), (OR = 0.54; 95% CI: 0.31-0.96) and (OR = 1.62; 95% CI: 0.97-2.69) was also not significantly different in HLNRA vs NLNRA, except at and The genotype frequencies at three of these SNPs i.e. and () were similar, whereas and showed significant difference between HLNRA and NLNRA population. However, further research using more number of SNPs in a larger cohort is required in this study area.