Phylogenetic relationship of the populations within and around Japan using 105 short tandem repeat polymorphic loci

Forensic features and genetic structure of 20 autosomal STR loci in the Han population of Ningde City, Southeastern China

BACKGROUND

Short tandem repeat (STR) loci are widely used in forensic medicine and population genetics.

AIM

To profile 20 autosomal STR loci using the SureID^® 21 G Human STR Identification Kit.

SUBJECTS AND METHODS

Samples were obtained from 1412 unrelated Chinese Han individuals from Ningde City, Southeastern China and 20 autosomal STR loci were profiled using the SureID^® 21 G Human STR Identification Kit.

RESULTS

A total of 261 alleles were observed among 1412 unrelated individuals and the corresponding allelic frequencies ranged from 0.5464 to 0.0004. The combined power of discrimination and exclusion of the 20 autosomal STR loci were 0.99999999999999999922 and 0.999999340285752, respectively. There was no significant deviation from Hardy-Weinberg equilibrium (HWE) and minimal departure from linkage equilibrium (LE) for two pairwise combinations of loci after sequential Bonferroni correction. In the population comparison, phylogenetic analysis was performed between the Han population and other relevant populations on the basis of the shared autosomal STR genotyping. Moreover, the neighbor-joining tree and principal component analysis were analysed based on the Nei's standard genetic distance.

CONCLUSION

The population comparison revealed that the structure of the Ningde Han population was similar to the structure of southern Han populations in China and was significantly different to the other Chinese ethnic groups, such as Kyrgyz, Uzbek, Kazakh, Uyghur, Manchu from Xinjiang and Mongols.

Population genetics of 24 Y-STR loci in Chinese Han population from Jilin Province, Northeast China

BACKGROUND

It is meaningful to expand the available population information on forensic medicine and to investigate the genetic characteristics of Han population from Jilin Province, Northeast China.

METHODS

In this study, we investigated the genetic characteristics of 24 Y-chromosomal short tandem repeat (STR) loci in 1,088 unrelated Chinese Han male individuals from Jilin Province, using DNATyperTM Y24 amplification kit. Additionally, we performed the population comparison between the Jilin population and the other nine reported populations based on the Y-STR genotyping haplotypes.

RESULTS

A total of 1,067 different haplotypes were found from 1,088 unrelated individuals, of which 1,046 were unique and 21 were shared by two individuals. The gene diversity values of 22 loci ranged from 0.3870 (DYS391) to 0.9668 (DYS385ab). The random match probability was 0.0010 with the discrimination capacity of 0.9807. Population comparison showed that there were minor differences compared to Beijing Chinese Han, China Manchu, Gansu Chinese Han, and Jiangsu Chinese Han, but major differences with respect to the populations of Guangdong Chinese Han, Yunnan Chinese Han, China Hui, China Korean, and China Tibetan.

CONCLUSION

Our results showed that the 24 Y-STR loci in Jilin Han population are valuable for forensic application and human genetics.

The history of human populations in the Japanese Archipelago inferred from genome-wide SNP data with a special reference to the Ainu and the Ryukyuan populations

The Japanese Archipelago stretches over 4000 km from north to south, and is the homeland of the three human populations; the Ainu, the Mainland Japanese and the Ryukyuan. The archeological evidence of human residence on this Archipelago goes back to >30 000 years, and various migration routes and root populations have been proposed. Here, we determined close to one million single-nucleotide polymorphisms (SNPs) for the Ainu and the Ryukyuan, and compared these with existing data sets. This is the first report of these genome-wide SNP data. Major findings are: (1) Recent admixture with the Mainland Japanese was observed for more than one third of the Ainu individuals from principal component analysis and frappe analyses; (2) The Ainu population seems to have experienced admixture with another population, and a combination of two types of admixtures is the unique characteristics of this population; (3) The Ainu and the Ryukyuan are tightly clustered with 100% bootstrap probability followed by the Mainland Japanese in the phylogenetic trees of East Eurasian populations. These results clearly support the dual structure model on the Japanese Archipelago populations, though the origins of the Jomon and the Yayoi people still remain to be solved.

Paleolithic Contingent in Modern Japanese: Estimation and Inference using Genome-wide Data

The genetic origins of Japanese populations have been controversial. Upper Paleolithic Japanese, i.e. Jomon, developed independently in Japanese islands for more than 10,000 years until the isolation was ended with the influxes of continental immigrants about 2,000 years ago. However, the knowledge of origin of Jomon and its contribution to the genetic pool of contemporary Japanese is still limited, albeit the extensive studies using mtDNA and Y chromosomes. In this report, we aimed to infer the origin of Jomon and to estimate its contribution to Japanese by fitting an admixture model with missing data from Jomon to a genome-wide data from 94 worldwide populations. Our results showed that the genetic contributions of Jomon, the Paleolithic contingent in Japanese, are 54.3∼62.3% in Ryukyuans and 23.1∼39.5% in mainland Japanese, respectively. Utilizing inferred allele frequencies of the Jomon population, we further showed the Paleolithic contingent in Japanese had a Northeast Asia origin.

A genetic analysis of the Sakishima islanders reveals no relationship with Taiwan aborigines but shared ancestry with Ainu and main-island Japanese

The Sakishima islands are members of the Ryukyu island chain, stretching from the southwestern tip of the Japanese archipelago to Taiwan in the East China Sea. Archaeological data indicate cultural similarities between inhabitants of prehistoric Sakishima and Neolithic Taiwan. Recent studies based on tooth crown traits show remarkably high inter-island diversity among Ryukyu islanders, suggesting that the Sakishima islanders might have genetic backgrounds distinct from main-island Okinawa people. To investigate the genetic diversity of the Ryukyu islanders, we analyzed mtDNA, Y chromosome, and autosomal short tandem repeat loci in a sample of main-island Okinawa people and Sakishima (Miyako and Ishigaki) islanders whose participated in a previous study of tooth crown morphology. Our phylogenetic analysis of maternal (mtDNA) and paternal (Y chromosome) lineages shows that the Sakishima islanders are more closely related to people from the Japanese archipelago than to Taiwan aborigines. Miyako islanders and the Hokkaido Ainu have the first and second highest frequencies (respectively) of the Y-chromosomal Alu-insertion polymorphism, which is a presumable Jomon marker. Genetic diversity statistics show no evidence of demographic reduction or of extreme isolation in each island's population. Thus, we conclude that 1) Neolithic expansion from Taiwan did not contribute to the gene pool of modern Sakishima islanders, 2) male-lineage of the Ryukyu islanders likely shares a common ancestor with the Hokkaido Ainu who are presumably direct descendants of the Jomon people, and 3) frequent reciprocal gene flow among islands has masked the trace of common ancestry in the Ryukyu island chain.

The population genomics of begomoviruses: global scale population structure and gene flow

BACKGROUND

The rapidly growing availability of diverse full genome sequences from across the world is increasing the feasibility of studying the large-scale population processes that underly observable pattern of virus diversity. In particular, characterizing the genetic structure of virus populations could potentially reveal much about how factors such as geographical distributions, host ranges and gene flow between populations combine to produce the discontinuous patterns of genetic diversity that we perceive as distinct virus species. Among the richest and most diverse full genome datasets that are available is that for the dicotyledonous plant infecting genus, Begomovirus, in the Family Geminiviridae. The begomoviruses all share the same whitefly vector, are highly recombinogenic and are distributed throughout tropical and subtropical regions where they seriously threaten the food security of the world's poorest people.

RESULTS

We focus here on using a model-based population genetic approach to identify the genetically distinct sub-populations within the global begomovirus meta-population. We demonstrate the existence of at least seven major sub-populations that can further be sub-divided into as many as thirty four significantly differentiated and genetically cohesive minor sub-populations. Using the population structure framework revealed in the present study, we further explored the extent of gene flow and recombination between genetic populations.

CONCLUSIONS

Although geographical barriers are apparently the most significant underlying cause of the seven major population sub-divisions, within the framework of these sub-divisions, we explore patterns of gene flow to reveal that both host range differences and genetic barriers to recombination have probably been major contributors to the minor population sub-divisions that we have identified. We believe that the global Begomovirus population structure revealed here could facilitate population genetics studies into how central parameters of population genetics namely selection, recombination, mutation, gene flow, and genetic drift shape the global begomovirus diversity.

Origin and dispersal of atypical aldehyde dehydrogenase ALDH2487Lys

The East Asian respond with a marked facial flushing and mild to moderate symptoms of intoxication after drinking the amounts of alcohol that has no detectable effect on European. The alcohol sensitivity in Orientals is due to a delayed oxidation of acetaldehyde by an atypical aldehyde dehydrogenase ALDH2487Lys, which is resulted from a structural mutation in gene ALDH2. The atypical ALDH2487Lys allele has been associated with various phenotypic statuses, such as protective against alcohol dependence and the risk of alcohol-related digestive tract cancers. Here, we have examined this SNP, adjacent four non-coding SNPs, and one downstream STRP on ALDH2 gene, in total of 1072 unrelated healthy individuals from 14 Chinese populations and 130 Indian individuals. Five major haplotypes based on five SNPs across the ALDH2 gene 40 kb were found in all East Asian populations. The frequencies of the ancestral haplotype GCCTG and the East Asian special haplotype GCCTA containing the atypical ALDH2487Lys allele were 44.8% and 14.9%, respectively. The frequency of the atypical ALDH2487Lys allele or the East Asian specific haplotype GCCTA is high in Yunnan, South coastal, east coastal of China, and decreased gradually toward inland China, West, Northwest and North China. Combined with demographic history in East Asian, our results showed that the presence of ALDH2487Lys allele in peripheral regions of China might be the results of historical migration events from China to these regions. The origin of ALDH2487Lys could be possibly traced back to ancient Pai-Yuei tribe in South China.

Minisatellite MS32 alleles show population specificity among Thai, Chinese, and Japanese

Lineages of structurally related alleles at minisatellite MS32 in human populations show considerable differentiation at the continental level. However, the regional specificity of these lineages remains unknown. We now describe the comparison of allele structures in Thai, Han Chinese, and Japanese populations with lineages previously established for North Europeans and Africans. The great majority of alignable Asian alleles showed their closest structural relative in Asia, with few instances of preferential alignment of Asian with European alleles and only one isolated incident showing a best match with an African allele. Further, there was a strong tendency, most marked for Japanese, for Asian alleles to align preferentially with other alleles from the same population, indicating strong regional specificity of allele lineages. This rapidly evolving minisatellite can therefore serve as a lineage marker for exploring recent events in human population history and dissecting population structure at the fine-scale level, as well as being an extremely informative DNA marker for personal identification.

A spatial analysis of genetic structure of human populations in China reveals distinct difference between maternal and paternal lineages

Analyses of archeological, anatomical, linguistic, and genetic data suggested consistently the presence of a significant boundary between the populations of north and south in China. However, the exact location and the strength of this boundary have remained controversial. In this study, we systematically explored the spatial genetic structure and the boundary of north-south division of human populations using mtDNA data in 91 populations and Y-chromosome data in 143 populations. Our results highlight a distinct difference between spatial genetic structures of maternal and paternal lineages. A substantial genetic differentiation between northern and southern populations is the characteristic of maternal structure, with a significant uninterrupted genetic boundary extending approximately along the Huai River and Qin Mountains north to Yangtze River. On the paternal side, however, no obvious genetic differentiation between northern and southern populations is revealed.

Low levels of genetic divergence across geographically and linguistically diverse populations from India

Ongoing modernization in India has elevated the prevalence of many complex genetic diseases associated with a western lifestyle and diet to near-epidemic proportions. However, although India comprises more than one sixth of the world's human population, it has largely been omitted from genomic surveys that provide the backdrop for association studies of genetic disease. Here, by genotyping India-born individuals sampled in the United States, we carry out an extensive study of Indian genetic variation. We analyze 1,200 genome-wide polymorphisms in 432 individuals from 15 Indian populations. We find that populations from India, and populations from South Asia more generally, constitute one of the major human subgroups with increased similarity of genetic ancestry. However, only a relatively small amount of genetic differentiation exists among the Indian populations. Although caution is warranted due to the fact that United States–sampled Indian populations do not represent a random sample from India, these results suggest that the frequencies of many genetic variants are distinctive in India compared to other parts of the world and that the effects of population heterogeneity on the production of false positives in association studies may be smaller in Indians (and particularly in Indian-Americans) than might be expected for such a geographically and linguistically diverse subset of the human population.

Genomic studies of human genetic variation are useful for investigating human evolutionary history, as well as for designing strategies for identifying disease-related genes. Despite its large population and its increasing complex genetic disease burden as a result of modernization, India has been excluded from most of the largest genomic surveys.

The authors performed an extensive investigation of Indian genetic diversity and population relationships, sampling 15 groups of India-born immigrants to the United States and genotyping each individual at 1,200 genetic markers genome-wide. Populations from India, and groups from South Asia more generally, form a genetic cluster, so that individuals placed within this cluster are more genetically similar to each other than to individuals outside the cluster. However, the amount of genetic differentiation among Indian populations is relatively small. The authors conclude that genetic variation in India is distinctive with respect to the rest of the world, but that the level of genetic divergence is smaller in Indians than might be expected for such a geographically and linguistically diverse group.

A comprehensive analysis of microsatellite diversity in Aboriginal Australians

Indigenous Australians have a unique evolutionary history that has resulted in a complex system of inter and intra-tribal relationships. While a number of studies have examined the population genetics of indigenous Australians, most have used a single sample to illuminate details of the global dispersal of modern humans and few studies have focussed on the population genetic features of the widely dispersed communities of the indigenous population. In this study we examine the largest Aboriginal Australian sample yet analysed (N = 8,868) at fifteen hypervariable autosomal microsatellite loci. A comprehensive analysis of differentiation indicates different levels of heterogeneity among indigenous peoples from traditional regions of Aboriginal Australia. The most genetically differentiated populations inhabit the North of the country, in particular the Tiwi of Melville and Bathurst islands, Arnhem Land (itself divided into West and East Arnhem), and Fitzmaurice regions. These tribal groups are most differentiated from other Aboriginal Australian tribes, especially those of the Central Desert regions, and also show marked heterogeneity from one another. These genetic findings are supportive of observations of body measurements, skin colour, and dermatoglyphic features which also vary substantially between tribes of the North (e.g. Arnhem Land) and Central Australian regions and, more specifically, between the Tiwi and West and East Arnhem tribes. This study provides the most comprehensive survey of the population genetics of Aboriginal Australia.

PSMIX: an R package for population structure inference via maximum likelihood method

BACKGROUND

Inference of population stratification and individual admixture from genetic markers is an integrative part of a study in diverse situations, such as association mapping and evolutionary studies. Bayesian methods have been proposed for population stratification and admixture inference using multilocus genotypes and widely used in practice. However, these Bayesian methods demand intensive computation resources and may run into convergence problem in Markov Chain Monte Carlo based posterior samplings.

RESULTS

We have developed PSMIX, an R package based on maximum likelihood method using expectation-maximization algorithm, for inference of population stratification and individual admixture.

CONCLUSION

Compared with software based on Bayesian methods (e.g., STRUCTURE), PSMIX has similar accuracy, but more efficient computations.PSMIX and its supplemental documents are freely available at http://bioinformatics.med.yale.edu/PSMIX.