Previously, I wrote about correlation between West African Ancestry (WAA) estimates and skin color among African Americans and African Caribbeans (here). They used 33 ancestry informative markers (AIMs) that have large frequency differences between African and European populations. Three of these markers are candidate genes for skin pigmentation (TYR, OCA2, and MC1R), so they examined, if these skin color candidate genes are associated with skin color (Melanin Index measure using the DermaSpectrometer).
Two pigmentation candidate genes (TYR and OCA2) and many other AIMs were associated with M Index without adjusting for WAA. When they adjust for WAA, only TYR remained significant. Then, they used ADMIXMAP, admixture mapping software, to find segments of genome that are associated with skin pigmentation because of the differences in their genetic ancestry. In this analysis, TYR and OCA2 are associated with skin color, but not MC1R.
Their analyses demonstrated that two pigmentation candidate genes (TYR and OCA2) likely to cause differences in skin color between African and European populations. TYR produces an enzyme, tyrosinase, which catalyzes the first two reactions in the melanin synthesis pathway. Mutations in OCA2, or P gene, cause the common type of albinism.
I hope to review follow-up research projects later to further understand genes involved in production of dark skin in African and African American populations.
