オセアニア地域集団の進化史 : ゲノムから見た混血と自然選択

The present Oceanian populations are considered to have derived from admixture of Papuan-and Asian-related ancestors.Papuan-related ancestors were the ancestors of modern Papuans and Aboriginal Australians, who colonized Near Oceania about 50,000 years ago, and Asian-related ancestors were Austronesian (AN)-speaking population, called Lapita, who migrated from Southeast Asia about 3,500 years ago.The major aim of this thesis is to elucidate the demographic history and adaptation of Oceanian populations.In Chapter 2, I analyzed mitochondrial DNA (mtDNA) and sex chromosomes of Oceanian populations.From the mtDNA analysis of three Oceanian populations living in the New Georgia Islands of the Solomon Islands, genetic similarity between AN-speaking Melanesians in the New Georgia Islands and Polynesians was revealed in maternal lineage, suggesting that Polynesian ancestors may have passed through the vicinity of the New Georgia Islands before their expansion to Remote Oceania (Section 1) .The previous studies on haplotype variations of mtDNA and Y chromosome suggested that sex-biased admixture (i.e., females primarily from Asian-related ancestry and males from Papuan-related ancestry) occurred in ancestors of Oceanian populations.In Section 2, to examine sex-biased admixture in Polynesians, the whole genome sequencing data including autosomes, sex chromosomes and mtDNA of Tongans were analyzed and QFST, an estimator of the ratio of effective population size on the X chromosome to that of the autosomes based on the measure of genetic differentiation (FST), was calculated between Tonga and Han Chinese from Beijing (CHB) and between Tonga and Gidra, a modern Papuan population in the lowlands of Western Province, Papua New Guinea.Corresponding to the previous studies, my results corroborated sex-biased admixture in ancestral populations of Tonga but the bias was likely to be not large.In Chapter 3, to assess the effect of admixture on the adaptation of AN-speaking Melanesians in the Solomon Islands, genome-wide SNP data of Munda, an AN-speaking Melanesian population in the New Georgia Islands of the Solomon Islands, were analyzed.I revealed that the Munda people were genetically related to other populations from the Solomon Islands and 51-57% of Munda genomes were estimated to be derived from Papuan-related ancestry when assuming CHB and Gidra as Asian-and Papuan-related ancestors, respectively.Two genomic regions which spanned more than 1 Mbp respectively showed significant proportions of Papuan-and Asian-related ancestry and were suspected to have experienced natural selection.The high Papuan-related ancestry region was located in the HLA class II region and the high Asian-related ancestry region contained the annexin A1 (ANXA1) gene.Since these genes have important roles in immune system, infectious diseases may be one of the possible driving forces of the selection.In Chapter 4, natural selection in Polynesians were detected in two different approaches.In Section 1, natural selection acted over the genomic regions derived from Papuanrelated ancestry was detected by estimating local ancestry across Tonga genomes assuming CHB and Gidra as Asian-and Papuan-related ancestors.The genome-wide proportion of Papuan-related ancestry was estimated about 25-33% in Tonga genomes.Two genomic regions which showed Papuan-related ancestry proportion higher than mean + 5 SD (~68%) were suspected to be shaped by positive selection.One was located in extended major histocompatibility complex regions and the other contained the ATP-binding cassette protein C11 (ABCC11).A nonsynonymous SNP on the ABCC11 (rs17822931) is known to affect apocrine secretory cell function and determine ear wax type.The ancestral allele (C) of rs17822931, wet ear wax allele, was frequently observed in Oceanian populations and likely to have undergone positive selection.Considering that Papuan-related ancestors have inhabited

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