A study on „golden gene“ adds an important piece to the jigsaw puzzle of human skin color variation
Though genetics of skin pigmentation has shown recent advancements in the last decade, studies involving populations of South Asia, one of the major hot spots of pigmentation diversity is still in its infancy stage. South Asia, inhabited by one-fifth of the world population and known for it’s complex prehistory, thus serves as a perfect model to decipher the underlying genetic architecture of skin pigmentation.
An international team of scientists led by researchers from University of Tartu, Estonian Biocentre and University of Cambridge, in a current study published in PLOS Genetics have filled this white spot by studying one of the important pigmentation genes, SLC24A5 which has been earlier known to contribute 25-38% of skin pigmentation differences between Europeans and West Africans.
In this study, the team carried out an expedition involving skin color measurements from local residents of India to quantify the range and extent of variation in skin pigmentation phenotype and found that this gene has a major effect on skin pigmentation. The first detailed map of the genetic variant inolving 54 ethnic populations shows that the light skin associated allele is quite wide spread.
“It was interesting to see that the effect of geographical, linguistic, socio-cultural boundaries further shaped by strict endogamy which forms the backbone of the South Asian genetic diversity was so strongly reflected in the complex patterning of this light skin allele” explains Chandana Basu Mallick, lead author, PhD student from University of Tartu and researcher at Estonian Biocentre. She further adds, “This study helps us to understand various other mechanisms that could have contributed in shaping the existing biological spectrum of human skin color in addition to the natural selection driven by UV rays, which is well-known and helps in further understanding of this complex phenotypic trait”.
Another important element of the study was resequencing of SLC24A5 using a representative global sample set which helped to unveil an important fact that Indians share the same mutation of SLC24A5 for their light skin as Europeans and belong to the same haplotype background. Though evidence of positive selection in SLC24A5 has been well demonstrated in previous genome-wide studies, the fact that South Asians have been underrepresented in the world-wide panels brought forward another important question; if there has been any evidence of positive selection for this gene in South Asians. To our surprise, we found that a differential pattern of selection with evidence of positive selection seen in North India, but not in South India. This further suggested that an interesting interplay between selection and demographic history of populations.
This study also provides the first comprehensive estimate of the coalescence time of rs1426654-A allele, which is crucial in the understanding of the evolutionary history of light skin in humans which is still a debated issue.
See the article at PLOS Genetics.
More information: Chandana Basu Mallick, phone: (+372) 53285250, e-mail: cbm2577 [ät] gmail.com;