Skin tones ranging from fair, wheatish, brown to dark brown can be found in populations all across India and this presents an ideal opportunity to examine the genetic architecture of skin colour.
A recent study, which is the first of its kind in India, has established the relationship between skin colour variations and genetics.
The study was conducted by Dr Kumarasamy Thangaraj at the CSIR-Centre for Cellular and Molecular Biology (CCMB), Hyderabad, in collaboration with Estonian Biocentre, Estonia and five other institutes. It was published on November 17, 2016 in the online edition of The Journal of Investigative Dermatology.
Initially, the study surveyed 1167 individuals from 27 populations and gathered data for melanin content from most exposed and low exposed area of human body at UP and Bihar. Out of this, 374 individuals were chosen for the first round of study, according to Dr Anshuman Mishra, the first author of the study.
Speaking to The News Minute, Dr Thangaraj said, “Initially we studied one particular location UP and Bihar, to measure the skin colour contrast and correlated that with genetic variation. Later on, we studied people from all over India where we didn’t see the skin colour component but only studied how this is distributed all over India.”
As per the report, the gene SLC24A5 is known to make the skin lighter and accounts for 25-38% of the pigmentation differences between Europeans and West Africans.
Analyses have revealed that two variants (rs1426654 and rs2470102) of this gene taken together could better explain the variation in skin colour among Indian populations than considering each variant independently.
Dr. Thangaraj added that those who have the mutation will have light colour and those who don’t have it will have dark colour. Wherever the gene or mutation is present, irrespective of the caste, race or tribe, they will have the skin colour variation. Those who migrate will carry the gene and that mutation will remain there.
The authors found that social structure defined by the caste system has a “profound influence on skin pigmentation”. The skin colour was found to vary significantly among ethnic groups and social categories studied, the report says.
“Our study clearly reflects the profound influence of the strict marriage patterns and multi-layered endogamy adding further to the variation in skin color contributing to the mosaic of skin tones”, says Chandana Basu, one of the authors of the study and researcher at Estonian Biocentre, Tartu, Estonia.
This team has studied 1,825 individuals belonging to 52 diverse populations across India and found that, social category and associated SNPs explain 38.4% of the variation in skin color. Unlike Africans and Europeans, we do not have homogeneous skin colour throughout the country. This could be due to different waves of human migration into India and recent admixture of all Indian populations, which we predicted in our previous study that it could have happened about two thousand years ago, said Dr. Thangaraj.
SNPs or single nucleotide polymorphisms are the most common type of genetic variation among people.
“The study was conducted over a period of three to four years but before that we had a sample structure, so these samples have been analysed,” said Dr Thangaraj.