A study of the molecular variants associated with lactase persistence in different Ecuadorian ethnic groups.

Objective: Lactase persistence (LP) is an adaptive trait that certain human populations have acquired in response to lactose consumption in adulthood. The T-13910 variant has been reported as a causal polymorphism in Europeans. The Ecuadorian population has been described as multicultural and multiethnic, comprised of three main ethnic groups (Mestizo, Native Amerindian, and Afro-Ecuadorian). The aim of the study was to identify the molecular basis of LP in these admixed populations for the first time and determine the association between the T-13910 marker and the European ancestry proportion of each ethnic group.

Methods: Genotyping was performed in 741 Ecuadorian individuals by sequencing a 576 bp region around the -13910 position upstream of the LCT gene. The ancestry proportions of Mestizo, Afro-Ecuadorian, and Native Amerindians were calculated using Ancestry Informative Markers and were compared with the diversity panel of the Human Genome Diversity Project.

Results: LP prevalence calculated from T-13910 allele frequency in Mestizo, Afro-Ecuadorian, and Native Amerindians was 24.4%, 16%, and 12.5%, respectively. The ancestry percentage correlated to the admixture proportion of each ethnic group, and the C/T-13910 genotype frequency was influenced by the European ancestry proportion.

Conclusions: The presence of the T-13910 polymorphism in the Ecuadorian population suggested that LP was a trait introduced by European migration and inherited by admixture that occurred during the colonization of South America. This variant was not fixed in a population with a history of admixture, and its allele frequency was proportional to the ancestry proportion of each Ecuadorian ethnic group. Am. J. Hum. Biol. 28:774-781, 2016. © 2016Wiley Periodicals, Inc.