Haruto Kodera

Origins and genetic features of the Okhotsk people, revealed by ancient mitochondrial DNA analysis

AbstractIn order to investigate the phylogenetic status of the Okhotsk people that were distributed in northern and eastern Hokkaido as well as southern Sakhalin during the fifth to the thirteenth centuries, DNA was carefully extracted from human bone and tooth remains excavated from archaeological sites. The hypervariable region 1 sequences of the mitochondrial DNA (mtDNA) control region were successfully amplified and 16 mtDNA haplotypes were identified from 37 individuals of the Okhotsk people. Of the 16 haplotypes found, 6 were unique to the Okhotsk people, whereas the other 10 were shared by northeastern Asian people that are currently distributed around Sakhalin and downstream of the Amur River. The phylogenetic relationships inferred from mtDNA sequences showed that the Okhotsk people were more closely related to the Nivkhi and Ulchi people among populations of northeastern Asia. In addition, the Okhotsk people had a relatively closer genetic affinity with the Ainu people of Hokkaido, and were likely intermediates of gene flow from the northeastern Asian people to the Ainu people. These findings support the hypothesis that the Okhotsk culture joined the Satsumon culture (direct descendants of the Jomon people) resulting in the Ainu culture, as suggested by previous archaeological and anthropological studies.

Polymorphisms and allele frequencies of the ABO blood group gene among the Jomon, Epi-Jomon and Okhotsk people in Hokkaido, northern Japan, revealed by ancient DNA analysis

To investigate the genetic characteristics of the ancient populations of Hokkaido, northern Japan, polymorphisms of the ABO blood group gene were analyzed for 17 Jomon/Epi-Jomon specimens and 15 Okhotsk specimens using amplified product-length polymorphism and restriction fragment length polymorphism analyses. Five ABO alleles were identified from the Jomon/ Epi-Jomon and Okhotsk people. Allele frequencies of the Jomon/Epi-Jomon and Okhotsk people were compared with those of the modern Asian, European and Oceanic populations. The genetic relationships inferred from principal component analyses indicated that both Jomon/Epi-Jomon and Okhotsk people are included in the same group as modern Asian populations. However, the genetic characteristics of these ancient populations in Hokkaido were significantly different from each other, which is in agreement with the conclusions from mitochondrial DNA and ABCC11 gene analyses that were previously reported.

Allele frequencies of the ABCC11 gene for earwax phenotypes among ancient populations of Hokkaido, Japan

Human earwax is classified into wet and dry types, which are determined by a single-nucleotide polymorphism in the adenosine triphosphate-binding cassette, sub-family C11 (ABCC11) gene locus. To investigate the allele frequencies of the ABCC11 locus within ancient populations on the Northern Japanese island of Hokkaido, amplified product-length polymorphisms were analyzed for 50 specimens of the Okhotsk people and 35 specimens of the Jomon and Epi-Jomon people excavated from various archaeological sites of Hokkaido. Of these specimens, 31 Okhotsk and 19 Jomon/Epi-Jomon samples were genotyped successfully. Frequencies of the wet-type allele in the Jomon/Epi-Jomon people, considered a major ancestor of the Ainu, were higher than those of other Northeastern Asian populations, including the modern Ainu. By contrast, in the Okhotsk people, believed to originate from East Siberia, frequencies of the dry-type allele were relatively higher than those in the Ainu and Jomon/Epi-Jomon people. These results suggest that gene flow from the Northeastern Asian Continent to descendants of the Jomon/Epi-Jomon people of Hokkaido through the Okhotsk people occurred, resulting in the establishment of the Ainu.

The Role of the Dentin Island in Root Bifurcation of the Human Molar

Abstract In the human molar, an area of calcification appears in the developmental process of tooth root bifurcation, independent of the tooth crown. This results in the formation of a dentin island, which subsequently fuses with the tooth crown dentin to form the root bifurcation. In the current study, I hypothesized that the role of the dentin island is to control the amount of dentin that is formed at the root bifurcation. The difference in the amount of dentin formed between the bifurcation side and the external- facing side of the root was investigated. The distance on the dentin surface from the dental neck to the root bifurcation midpoint, and the corresponding distance on the external mesial surface were measured. The distance on the bifurcation side was nearly twice as long as that on the external-facing side. The appearance of the dentin island is considered to supplement the formation of dentin in the bifurcation. It was possible to geometrically identify the position in the calcification point. This corresponded to the actual calcification point as determined from a tetracycline-labeling image.