No evidence of telomere length attrition in newborns from high level natural background radiation areas in Kerala coast, south west India

Abstract

Purpose: The tandemly repeated hexamers (TTAGGG)n present at the telomeric ends protect the human genome from a variety of environmental exposures including ionizing radiation. In order to find out the effect of chronic low dose radiation exposure, we have determined telomere length among newborns from high level natural radiation areas (HLNRA) of the Kerala coast in South west India.Methodology: Umbilical cord blood samples were collected from 128 newborns from HLNRA and 43 newborns from normal level natural radiation areas (NLNRA) and genomic DNA was isolated using a salt precipitation method. The mean telomere length was determined using SYBR green-based real time quantitative Polymerase chain reaction (qPCR), where telomere gene specific (T) and single copy gene specific (S) primers were used. The average of telomere versus single copy gene (T/S) ratio was calculated which was proportional to telomere length of each individual.Results: The mean relative telomere length was found to be 1.03 ± 0.01 (95% CI, 0.99–1.05) and 1.10 ± 0.03 (95% CI, 1.04–1.17) in HLNRA and NLNRA newborns, respectively (P > 0.05). Based on the level of background radiation dose, samples were divided into four groups, i.e., NLNRA: < 1.50 mGy/year and three HNLRA groups: 1.51–3.00 mGy/year, 3.01–5.00 mGy/year, and > 5.00 mGy/year. The mean relative telomere length in these groups were found to be 1.10 ± 0.03 (95% CI, 1.03–1.17), 0.98 ± 0.01 (95% CI, 0.95–1.01), 1.05 ± 0.02 (95% CI, 1.01–1.10) and 1.07 ± 0.03 (95% CI, 1.04–1.10), respectively. No significant difference was observed between the mean telomere length of male and female newborns.Conclusions: The elevated level of natural chronic background radiation prevailing in Kerala coast did not show any significant effect on telomere length of newborns. To our knowledge, this is the first report on newborn telomere length from a high level natural radiation area.