DRD4 VNTR polymorphism in Oceanic populations

Abstract

To study the origin of Polynesians and the gene flow from Polynesian ancestors to indigenous Melanesians, a 48-bp variable number of tandem repeats (VNTR) in exon 3 of the dopamine D4 receptor (DRD4) gene was investigated for six Austronesian (AN)-speaking populations—two in Tonga (Nuku’alofa and Ha’apai), three in Solomon Islands (Munda, Paradise, and Rawaki, of whom Rawaki was a Micronesian migrant group), and one in Papua New Guinea (Balopa), and one Non-Austronesian (NAN)-speaking population in Papua New Guinea (Gidra). In these Oceanic populations, six VNTR alleles with 2 (2R) to 11 (7R) repeats were observed. The most frequent DRD4 VNTR allele was the 4R allele, although the allele frequencies of 2R and 7R varied markedly among them, characterized by high frequencies of 7R and lack of 2R in NAN-speaking Melanesians (Gidra), and high frequencies of 2R and low or null frequencies of 7R in AN-speaking Polynesians (Nuku’alofa and Ha’apai) and Micronesians (Rawaki). The allele frequency distribution of DRD4 VNTR in Polynesians was similar to that in Aboriginal Taiwanese (Ami and Atayal), supporting the hypothesis that Polynesian ancestors were derived from Southeast Asians (probably Taiwanese). A principal component analysis for Southeast Asian and Oceanic populations based on the DRD4 VNTR allele frequencies revealed that AN-speaking Melanesian populations were genetically placed between two AN-speaking Polynesian and one NAN-speaking Melanesian populations. These results provide evidence of gene flow from Polynesian ancestors to indigenous Melanesians while Polynesian ancestors passed through Melanesia.