By Meghan Bialt-DeCelie ’19

Currently, our understanding of the genes behind skin pigmentation in humans is limited, especially for those of African heritage. Researchers led by Nicholas Crawford, PhD from the University of Pennsylvania investigated the genetic variants behind a wider range of skin colors provided from diverse African populations.

Melanin is the pigment that provides the wide range of skin colors seen in the human population. The researchers first measured melanin levels of over two thousand genetically diverse subjects from the African countries of Ethiopia, Tanzania, and Botswana. They did this by using a DSMII Color Meter which measured light reflection from the skin. They also analyzed the genomes of nearly 1600 African individuals and compared them to sequences of people from the Thousand Genomes Project in search of associations of loci with skin pigmentation and geographical origins. Then they ranked these associations with a method called Causal Variants Identification in Associated Regions, or CAVIAR. This is a statistical analysis that predicts the likelihood that a certain trait is caused by a certain gene. They found six genes that had strongly correlations to skin pigmentation: SLC24A5, MFSD12, DDB1, TMEM138, OCA2, and HERC2.

The geneticists found that the Solute Carrier Family 24 Member 5 gene, or SLC24A5, had the strongest correlation to skin pigmentation. They also found associations with the gene MFSD12 which is a protein used in melanin production that is also found in other organisms such as zebrafish and mice. Understanding the roles of the genes most associated with skin pigmentation gives insight not only to the evolutionary history of the modern human but also potential gene targets for skin related diseases.

References:

1. N. Crawford, et al., Loci associated with skin pigmentation identified in African populations. Science, (2017). doi: 10.1126/science.aan8433.
2. Image retrieved from: http://www.ramstein.af.mil/News/Article-Display/Article/303949/diversity-equality-strengthen-bonds-across-force/