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An understanding of pigmentation that is more than just skin deep

American Association for the Advancement of Science

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IMAGE: A Ju/'hoansi individual of the San who was not part of the study. This material relates to a paper that appeared in the 12 October 2017, online issue of Science,... view more 

Credit: Alessia Ranciaro

In an effort to better understand genes affecting skin pigmentation, scientists have generated one of the largest and most comprehensive datasets to date - by sequencing the genomes of 2,092 ethnically and genetically diverse Africans living in Ethiopia, Tanzania, and Botswana. Their findings shed light on how genes associated with skin color likely moved across the globe with human migration, both in and out of Africa. Variation in skin pigmentation is a striking feature of modern humans, and has been correlated with geographic and environmental variation. Despite this wide range, little is known about its underlying genetic basis in global populations. Here, Nicholas Crawford and colleagues identified genetic variants with a likely role in skin tone. The results hinted that one of the light pigmentation variants near the SCL24A5 gene locus was introduced into East Africa by gene flow from non-Africans. At all other loci examined, variants associated with dark pigmentation in Africans were identical by descent in southern Asian and Australo-Melanesian populations. Additional analyses indicated that one particular region of DNA associated with skin pigmentation, MFSD12, encodes a protein that affects the process whereby the skin produces pigment (called melanogenesis), which Crawford et al. confirmed in zebrafish and mouse models (suggesting its conserved function in humans). The authors say that research in larger numbers of ethnically diverse Africans may help uncover additional loci associated with skin pigmentation - lending further insight into the evolutionary history and adaptive significance of skin pigmentation in humans.

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