The variation of light skin in people of Eurasian ethnicity evolved independently from different genetic backgrounds. This is just one of the new genetic variations associated with skin colour that has been identified by a study of Latin American populations (Nature Communications Jan. 2019; 10(1):358).
Researchers analysed the genetic makeup of the skin pigmentation of over 6,000 Latin Americans, who have a mixture of Native American, European, and African ancestry. Investigators grounded their research in the knowledge that Native Americans are genetically closely related to East Asians. The initial settlement of the Americas occurred an estimated 15,000 to 20,000 years ago, through migration from Eastern Siberia into North America. As a consequence, genetic variations in Native Americans are often shared with East Asians, the researchers wrote.
A total of five new associated genetic regions involving skin, eye, and hair colour were identified. Researchers observed an important variation in the gene MFSD12 that is found uniquely in East Asian and Native American groups—this is the first time that the gene has been linked to skin colour in Native Americans and East Asians. MFSD12 influences how pigment is produced and stored in the skin. Investigators say that the MFSD12 gene was modified after East Asians separated from Europeans around 40,000 years ago, and was then carried over to America by ancient migrations of Native Americans.
“Our work demonstrates that lighter skin colour evolved independently in Europe and East Asia. We also show that this gene was under strong natural selection in East Asia, possibly as adaptation to changes in sunlight levels and ultraviolet radiation,” said study first author Kaustubh Adhikari, PhD, statistical geneticist at the University College London Genetics Institute in London in a press release.
Photo by Frerieke via https://commons.wikimedia.org/wiki/File:Diversity_and_Unity.jpg (CC 2.0).
“It is commonly thought that variation in pigmentation, such as skin colour, in Latin Americans primarily arises due to people’s varying degree of European or African ancestry. But our new study shows that there is variation inherited from their Native ancestors as well,” added joint first author Javier Mendoza-Revilla, PhD, post-doctoral research fellow at Institut Pasteur in Paris.
In addition to skin tone variation, the scientists also noted a wide variation in eye colour among Latin Americans.
“Just like skin colour, early research on eye colour was Europe-centric, and mostly focused on the distinction between blue versus brown eyes. But we show that eye colour is a broad continuum, and by studying the subtler variation within brown to black, we found two new genes linked to it,” said co-author Anood Sohail, PhD student in the genetics department at the University of Cambridge in Cambridge, U.K.
A major motivator for the investigators is the historical lack of diversity in genetics research. For example, the first major study on the genetics of skin tone diversity in Africa occurred only recently. Latin Americans are similarly underrepresented in genetics research, particularly in pigmentation research.
Notably, the MFSD12 gene was also identified in the skin colour study of Africans, however, the variants were completely different than those observed in the current study. “[This highlights] the huge genetic diversity in humans and the need to diversify our study populations,” explained co-author Dr. Andres Ruiz-Linares, honorary professor of human genetics. Department of Genetics, Evolution and Environment at University College London.
This educational gap regarding patients with ethnic skin is one of the reasons why the Skin Spectrum Summit was created by Chronicle Companies, publisher of The Chronicle of Skin & Allergy. It is a one-day educational congress of dermatologists, general practitioners, and family physicians committed to providing better dermatologic care for Canada’s growing ethnic communities, notably Fitzpatrick Scale skin types III through VI. The annual event takes place in Toronto, Montreal, and Vancouver. For more information on this year’s Skin Spectrum Summit, please visit www.skinspectrum.ca