Dataset Information

Rapid evolution of a skin-lightening allele in southern African KhoeSan.

ABSTRACT: Skin pigmentation is under strong directional selection in northern European and Asian populations. The indigenous KhoeSan populations of far southern Africa have lighter skin than other sub-Saharan African populations, potentially reflecting local adaptation to a region of Africa with reduced UV radiation. Here, we demonstrate that a canonical Eurasian skin pigmentation gene, SLC24A5, was introduced to southern Africa via recent migration and experienced strong adaptive evolution in the KhoeSan. To reconstruct the evolution of skin pigmentation, we collected phenotypes from over 400 ?Khomani San and Nama individuals and high-throughput sequenced candidate pigmentation genes. The derived causal allele in SLC24A5, p.Ala111Thr, significantly lightens basal skin pigmentation in the KhoeSan and explains 8 to 15% of phenotypic variance in these populations. The frequency of this allele (33 to 53%) is far greater than expected from colonial period European gene flow; however, the most common derived haplotype is identical among European, eastern African, and KhoeSan individuals. Using four-population demographic simulations with selection, we show that the allele was introduced into the KhoeSan only 2,000 y ago via a back-to-Africa migration and then experienced a selective sweep (s = 0.04 to 0.05 in ?Khomani and Nama). The SLC24A5 locus is both a rare example of intense, ongoing adaptation in very recent human history, as well as an adaptive gene flow at a pigmentation locus in humans.

SUBMITTER: Lin M

PROVIDER: S-EPMC6310813 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Rapid evolution of a skin-lightening allele in southern African KhoeSan.

Lin Meng M Siford Rebecca L RL Martin Alicia R AR Nakagome Shigeki S Möller Marlo M Hoal Eileen G EG Bustamante Carlos D CD Gignoux Christopher R CR Henn Brenna M BM

Proceedings of the National Academy of Sciences of the United States of America 20181210 52

Skin pigmentation is under strong directional selection in northern European and Asian populations. The indigenous KhoeSan populations of far southern Africa have lighter skin than other sub-Saharan African populations, potentially reflecting local adaptation to a region of Africa with reduced UV radiation. Here, we demonstrate that a canonical Eurasian skin pigmentation gene, <i>SLC24A5</i>, was introduced to southern Africa via recent migration and experienced strong adaptive evolution in the ...[more]

PMID: 30530665

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Project description:BackgroundThe Minamata Convention on Mercury (Article 4) prohibits the manufacture, import, or export of skin-lightening products containing mercury concentrations above 1 ppm. However, there is a lack of knowledge surrounding the global prevalence of mercury-added skin-lightening products.ObjectiveThe objective of this study was to increase our understanding of worldwide human mercury exposure from skin-lightening products.MethodsA systematic search of peer-reviewed scientific literature was performed for relevant articles in four databases (PubMed, Web of Science Core Collection, Scopus, and TOXLINE). The search strategy, eligibility criteria, and data-extraction methods were established a priori. The search identified 2,303 unique scientific articles, of which 41 were ultimately deemed eligible for inclusion after iterative screens at the title, abstract, and whole-text levels. To facilitate data extraction and synthesis, all papers were organized according to four data groups a) "Mercury in products," b) "Usage of products," c) "Human biomarkers of exposure," and d) "Health impacts."ResultsThis review was based on data contained in 41 peer-reviewed scientific papers from 22 countries worldwide published between 2000 and 2022. In total, we captured mercury concentration values from 787 skin-lightening product samples [overall pooled central median mercury level was 0.49μg/g; interquartile range (IQR): 0.02-5.9] and 1,042 human biomarker measurements from 863 individuals. We also synthesized usage information from 3,898 individuals and self-reported health impacts associated with using mercury-added products from 832 individuals.DiscussionThis review suggests that mercury widely exists as an active ingredient in many skin-lightening products worldwide and that users are at risk of variable and often high exposures. These synthesized findings identify data gaps and help increase our understanding of the health risks associated with the use of these products. https://doi.org/10.1289/EHP10808.

Dataset Information

Rapid evolution of a skin-lightening allele in southern African KhoeSan.

Publications

Rapid evolution of a skin-lightening allele in southern African KhoeSan.

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