Evidence of epigenetic admixture in the Colombian population.

DNA methylation (DNAm) measured in lymphoblastoid cell lines has been repeatedly demonstrated to differ between various human populations. Due to the role that DNAm plays in controlling gene expression, these differences could significantly contribute to ethnic phenotypic differences. However, because previous studies have compared distinct ethnic groups where genetic and environmental context are confounded, their relative contribution to phenotypic differences between ethnicities remains unclear. Using DNAm assayed in whole blood and colorectal tissue of 132 admixed individuals from Colombia, we identified sites where differential DNAm levels were associated with the local ancestral genetic context. Our results are consistent with population specific DNAm being primarily driven by between population genetic differences in cis, with little environmental contribution, and with consistent effects across tissues. The findings offer new insights into a possible mechanism driving phenotypic differences among different ethnic groups, and could help explain ethnic differences in colorectal cancer incidence.