HLA-DQ haplotypes in 15 different populations

Abstract

In order to understand the forces governing the evolution of the DQ molecule, PCR-based methods have been used to type the DQA1 and DQB1 loci encoding this heterodimer on 2,807 chromosomes from 15 different populations including Africans, Asians, Amerindians and Caucasians. These ethnically diverse samples represent a variety of population substructures and include small, isolated populations as well as larger populations where admixture has occurred. Nine DQA1 alleles and 18 DQB1 alleles have been identified which make up 42 distinct DQ haplotypes. Some haplotypes are found in all ethnic groups while others are confined to a single ethnic group or population. Despite evidence of recombination between the DQA1 and DQB1 loci, there are no examples of a haplotype carrying a DQw1-associated alpha chain and a DQw2-, DQw3-, or DQw4-associated beta chain in cis (and vice versa). These data suggest that these haplotypes, which encode unstable heterodimers, are rapidly removed from the population through natural selection.