Structural Diversity and African Origin of the 17q21.31 Inversion Polymorphism

The 17q21.31 inversion polymorphism exists either as direct (H1) or inverted (H2) haplotypes with differential predispositions to disease and selection. We investigated its genetic diversity in 2700 individuals with an emphasis on African populations. We characterize eight structural haplotypes that vary in size from 1.08 to 1.49 Mbp as a result of complex rearrangements and provide evidence for a 30 kbp H1/H2 double recombination event. We show that recurrent partial duplications of the KANSL1 (previously known as KIAA1267) gene have occurred on both H1 and H2 haplotypes and risen to high frequency in European populations. We identify a likely ancestral H2 haplotype (H2′) lacking these duplications, enriched among African hunter-gatherer groups yet essentially absent from West Africans populations. While H1 and H2 segmental duplications arose independently and prior to the human migration out of Africa, they have reached high frequencies recently among Europeans either due to extraordinary genetic drift or selective sweeps.