ミトコンドリアゲノムから明らかになったメソアメリカ現生人類集団の遺伝構造ならびに次世代シーケンサによる古人骨ゲノム分析法構築と解析

学位の種別:課程博士University of Tokyo(東京大学

mtDNA diversity of the Zapotec in Mexico suggests a population decline long before the first contact with Europeans.

The New World is the last continent colonized by anatomically modern humans, Homo sapiens. The first migrants entered the New World from Asia through Beringia. It is suggested that there were three streams of Asian gene flow, one major and two additional minor gene flows. The first major migrants took a Pacific coastal route and began spreading to the American continent before the opening of the ice-free corridor. We investigated the diversity of full-length mitochondrial DNA genomes of the Zapotec population, residing in the Mesoamerican region, and reconstructed their demographic history using Bayesian Skyline Plots. We estimated the initial date of gene flow into the New World by Zapotec ancestors at around 17 000–19 000 years ago,which is highly concordant with previous studies. We also show a population decline after the initial expansion. This decline started 4000 years ago, long before European contact with Native Americans. This indicates that other factors including climatec hange should be considered to explain the observed demographic pattern

A study of 8,300-year-old Jomon human remains in Japan using complete mitogenome sequences obtained by next-generation sequencing

Ancient human remains have been assigned to their mitochondrial DNA (mtDNA) haplogroups. To obtain efficiently deep and reliable nucleotide sequences of ancient DNA of interest, we achieved target enrichment followed by next-generation sequencing (NGS). Complete mitochondrial genome (mitogenome) sequences were obtained for three human remains from the Iyai rock-shelter site of the Initial Jomon Period in Japan. All the Jomon mitogenomes belong to haplogroup N9b, but no sequences among them were identical. High genetic diversity was clarified even among the Jomon human remains belonging to haplogroup N9b, which has been described as a haplogroup representing the Jomon people

Diversity in matrilineages among the Jomon individuals of Japan

Background The Jomon period of Japan is characterised by a unique combination of sedentary and hunting/gathering lifestyles, spanning for more than 10,000 years from the final Pleistocene to the Holocene. The transition from the preceding Palaeolithic period to the Jomon period is known to have begun with the appearance of pottery usage. However, knowledge of the genetic background of the Jomon people is still limited. Aim We aimed to determine the population-scale complete mitogenome sequences of the Initial Jomon human remains and compare the occurrence of mitochondrial haplogroups in the Jomon period from temporal and regional perspectives. Subjects and methods For human remains dated to 8200–8600 cal BP, we determined their complete mitogenome sequences using target enrichment-coupled next-generation sequencing. Results We successfully obtained the complete mitogenome sequences with high depth of coverage and high concordance on consensus sequences. These sequences differed by more than three bases each, except for two individuals having completely identical sequences. Co-existence of individuals with haplogroups N9b and M7a was first observed at the same archaeological site from the Initial Jomon period. Conclusion The genetic diversity within the population was not found to be low even in the Initial Jomon period

Complete mitogenome analysis of indigenous populations in Mexico: its relevance for the origin of Mesoamericans.

Mesoamerica has an important role in the expansion of Paleoamericans as the route to South America. In this study, we determined complete mitogenome sequences of 113 unrelated individuals from two indigenous populations of Mesoamerica, Mazahua and Zapotec. All newly sequenced mitogenomes could be classified into haplogroups A2, B2, C1 and D1, but one sequence in Mazahua was D4h3a, a subclade of haplogroup D4. This haplogroup has been mostly found in South America along the Pacific coast. Haplogroup X2a was not found in either population. Genetic similarity obtained using phylogenetic tree construction and principal component analysis showed that these two populations are distantly related to each other. Actually, the Mazahua and the Zapotec shared no sequences (haplotypes) in common, while each also showed a number of unique subclades. Surprisingly, Zapotec formed a cluster with indigenous populations living in an area from central Mesoamerica to Central America. By contrast, the Mazahua formed a group with indigenous populations living in external areas, including southwestern North America and South America. This intriguing genetic relationship suggests the presence of two paleo-Mesoamerican groups, invoking a scenario in which one group had expanded into South America and the other resided in Mesoamerica

Characterization of complete mitochondrial genomes of indigenous Mayans in Mexico

Background: The authors have previously published the complete mitochondrial genome (mitogenome) sequences of two indigenous Mesoamerican populations, Mazahua (n = 25) and Zapotec (n = 88). Methods: This study determined the complete mitogenome sequences of nine unrelated individuals from the indigenous Maya population living in Mexico. Results: Their mitogenome sequences could be classified into either of the haplogroups A2 and C1. Surprisingly, there were no mitogenome sequences (haplotypes) that the Maya, Mazahua, and Zapotec people share in common. Conclusions: This indicates that no genetic exchange, at least matrilineally, has occurred among them

Population dynamics in the Japanese Archipelago since the Pleistocene revealed by the complete mitochondrial genome sequences

Abstract The Japanese Archipelago is widely covered with acidic soil made of volcanic ash, an environment which is detrimental to the preservation of ancient biomolecules. More than 10,000 Palaeolithic and Neolithic sites have been discovered nationwide, but few skeletal remains exist and preservation of DNA is poor. Despite these challenging circumstances, we succeeded in obtaining a complete mitogenome (mitochondrial genome) sequence from Palaeolithic human remains. We also obtained those of Neolithic (the hunting-gathering Jomon and the farming Yayoi cultures) remains, and over 2,000 present-day Japanese. The Palaeolithic mitogenome sequence was not found to be a direct ancestor of any of Jomon, Yayoi, and present-day Japanese people. However, it was an ancestral type of haplogroup M, a basal group of the haplogroup M. Therefore, our results indicate continuity in the maternal gene pool from the Palaeolithic to present-day Japanese. We also found that a vast increase of population size happened and has continued since the Yayoi period, characterized with paddy rice farming. It means that the cultural transition, i.e. rice agriculture, had significant impact on the demographic history of Japanese population