Distribution of a 27-bp deletion in the band 3 gene in South Pacific islanders.

Distribution of a 27-bp deletion in the band 3 gene (B3Delta27) that causes Southeast Asian/Melanesian ovalocytosis has scarcely been studied in remote insular Southeast Asia and New Guinea. Here the presence of the B3Delta27 was surveyed among a total of 756 subjects from the indigenous populations inhabiting New Guinean islands and remote insular Southeast Asia by using a polymerase chain reaction method. In remote insular Southeast Asia where Austronesian-speaking peoples inhabit, the B3Delta27 frequency ranged between 0.04 and 0.15. In New Guinea Island, hinterland or Papuan groups showed the absence of the B3Delta27 or a very low gene frequency (0.01 in the Gidra) of the B3Delta27. However, groups of the coastal regions (Asmat, Sorong, and others) and of the nearby islands (Biak and Manus) where Austronesian infiltration had occurred showed substantial frequencies of the deletion (0.02-0.09). It is likely that the B3Delta27 was introduced into this region about 3,500 years ago with the arrival of Austronesian-speaking peoples. Once being introduced, the B3Delta27 may have been selected because of its resistance against malaria, while founder effect and genetic drift might have occurred in the New Guinean tribes with small population size, which helped to generate a variety of the B3Delta27 frequencies.