Ecological factors in the formation of the Eurasian genogeographic landscape of the vitamin D receptor (VDR) gene

AIM: to analyze the geographical variability of the frequencies of the "risk" alleles C*ApaI, G*BsmI, A*TaqI, and A*FokI of the VDR gene in Eurasian populations, considering the influence of environmental factors.

METHODS: Polymorphism of the VDR gene in 140 populations of the indigenous population of Eurasia was studied using our own data (3,441 DNA samples) and materials from 68 publications (an average of 4 alleles from more than 7,000 DNA samples). Maps of the geographical variability of allele frequencies and homozygous genotypes of VDR polymorphisms were created using the weighted average interpolation method of GeneGeo 2.8 software. The average daily ultraviolet radiation (UV-B radiation, 280-315 nm) for a three-month period of minimum natural light levels were obtained from the global glUV dataset. The relationships between genetic polymorphism frequencies, population geographical coordinates, and insolation indices were assessed using Spearman rank correlation.

RESULTS: Genogeographic maps of the variability in the frequencies of the C*ApaI, G*BsmI, A*TaqI, and A*FokI alleles and their homozygous genotypes in groups of the indigenous population of Eurasia were created. The frequency of A*FokI increased in the western direction (p = 0.013), whereas that of the other alleles increased in the eastern direction (p ≤ 0.001). Population frequencies of the ApaI, BsmI, and FokI polymorphisms were significantly negatively correlated with the level of UV-B radiation during the three-month period of lowest seasonal insolation (p ≤ 0.014).

CONCLUSION: Although the affiliation of populations to the Caucasoid and Mongoloid racial groups is manifested in the distribution of VDR gene polymorphisms, part of the variability in the frequencies of "risk" alleles is due to environmental factors: level of insolation (UV-B radiation), diet, and availability of foods containing vitamin D.