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| 1.
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論文（リポジトリ）
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Isshiki, Mariko ; Naka, Izumi ; Watanabe, Yusuke ; Nishida, Nao ; Kimura, Ryosuke ; Furusawa, Takuro ; Natsuhara, Kazumi ; Yamauchi, Taro ; Nakazawa, Minato ; Ishida, Takafumi ; Eddie, Ricky ; Ohtsuka, Ryutaro ; Ohashi, Jun
概要:
People in the Solomon Islands today are considered to have derived from Asian- and Papuan-related ancestors. Papuan-rela
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ted ancestors colonized Near Oceania about 47,000 years ago, and Asian-related ancestors were Austronesian (AN)-speaking population, called Lapita, who migrated from Southeast Asia about 3,500 years ago. These two ancestral populations admixed in Near Oceania before the expansion of Lapita people into Remote Oceania. To understand the impact of the admixture on the adaptation of AN-speaking Melanesians in Near Oceania, we performed the genome-wide single nucleotide polymorphism (SNP) analysis of 21 individuals from Munda, the main town of the New Georgia Islands in the western Solomon Islands. Population samples from Munda were genetically similar to other Solomon Island population samples. The analysis of genetic contribution from the two different ancestries to the Munda genome revealed significantly higher proportions of Asian- and Papuan-related ancestries in the region containing the annexin A1 (ANXA1) gene (Asian component > 82.6%) and in the human leukocyte antigen (HLA) class II region (Papuan component > 85.4%), respectively. These regions were suspected to have undergone natural selection since the time of admixture. Our results suggest that admixture had affected adaptation of AN-speaking Melanesians in the Solomon Islands.
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| 2.
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論文（リポジトリ）
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Furusawa, Takuro ; Naka, Izumi ; Yamauchi, Taro ; Natsuhara, Kazumi ; Eddie, Ricky ; Kimura, Ryosuke ; Nakazawa, Minato ; Ishida, Takafumi ; Ohtsuka, Ryutaro ; Ohashi, Jun
概要:
The people of the Solomon Islands represent an Austronesian (AN)-speaking population’s adaptation to a humid tropical en
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vironment and subsistence of tuberous crops. Genome-wide association studies (GWASs) of other populations (e.g. the Human Genome Diversity Project [HGDP]) have suggested the existence of genotypes adaptive to ecoregion, diet, and subsistence, and that those genotypes are also associated with metabolic and cardiovascular diseases. Recently, the incidence of non-communicable diseases has been increasing in the Solomon Islands. In the present study, we explored the association of genotypes adaptive to a tropical environment and tuberous crop diet with metabolic and cardiovascular conditions in rural and urban AN-speaking Melanesian and Micronesian populations of the Solomon Islands. A total of 561 participants were genotyped for single nucleotide polymorphisms (SNPs) potentially associated with a tropical environment (rs174570 and rs2237892) and a tuberous crop diet (rs162036, rs185819, and rs2722425). The results showed that the allele frequencies of the Solomon Islands populations adopted patterns similar to those in populations from other hot, tropical areas with a tuberous crop diet in previous studies. Furthermore, rs162036, rs185819, rs2237892, and rs2722425 were all strongly associated with one or more metabolic and cardiovascular conditions. The derived allele of rs2722425 (i.e. rs2722425-G) was significantly associated with an elevated LDL level (P = 0.000264) even after the significance level was adjusted for multiple testing (i.e., α = 0.0005). Our results suggest that the inhabitants of the Solomon Islands exhibit the effects of the tropical environment and tuberous crop diet on their allele frequencies, and that their susceptibility to metabolic and cardiovascular diseases is therefore considered to be associated with their environment and diet.
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| 3.
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論文（リポジトリ）
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Naka, Izumi ; Ohashi, Jun ; Kimura, Ryosuke ; Furusawa, Takuro ; Yamauchi, Taro ; Nakazawa, Minato ; Natsuhara, Kazumi ; Ataka, Yuji ; Nishida, Nao ; Ishida, Takafumi ; Inaoka, Tsukasa ; Matsumura, Yasuhiro ; Ohtsuka, Ryutaro
概要:
To study the origin of Polynesians and the gene flow from Polynesian ancestors to indigenous Melanesians, a 48-bp variab
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le 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.
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