Gene flow between the Korean peninsula and its neighboring countries

Biogeographic origin and genetic characteristics of the peopling of Jeju Island based on lineage markers

BACKGROUND

Jeju Island is the largest island of South Korea, located southwest far from the mainland of Korea, and has a unique history and its own cultures that are distinguished from those of the other regions of the Korean mainland. However, the Jeju population has not been deeply investigated to date to understand their genetic structure, which may reflect their historical and geographical background.

OBJECTIVE

To identify the genetic characteristics and biogeographic origin of people of Jeju Island based on the statistical analysis of genetic data using lineage markers.

METHODS

17 Y-STRs data for 615 unrelated males and mitochondrial DNA haplogroup data for 799 unrelated individuals residing on Jeju Island were generated, and analyzed to investigate genetic diversity and genetic characteristics using statistical methods including pairwise Fst or Rst, Analysis of molecular variance (AMOVA) and Multidimensional scaling (MDS).

RESULTS

For male individuals of Jeju Island, unique genetic characteristics were observed in the analysis of Y-STRs, including low haplotype diversity, strong association with surnames, genetic difference from other regions of Korea, and common genetic variation of the Y-STR loci known to be predominant in Northern populations, such as Mongolians. Statistical analysis of the mitochondrial DNA haplogroups also revealed similar results that showed low haplogroup diversity and high frequency of haplogroup Y prevalent mostly in ethnic populations around the Sea of Okhotsk in Northeastern Asia. All these results suggest that Jeju Island is genetically distinct from other regions of Korea, possibly being a subpopulation in Korea, and related closely to Northern Asian populations.

CONCLUSION

The findings in the genetic approach could support understanding of the historical background of Jeju Island that is consistent with evidence from other multidisciplinary studies.

Genetic variation in the coagulation factor V gene and risk of femoral head osteonecrosis

Osteonecrosis of the femoral head (ONFH) is characterized by the death of the cellular portion of the femoral head due a reduction or disruption in the blood supply. Certain studies have implicated coagulation disorders, including thrombophilia and hypofibrinolysis, in the pathogenesis of ONFH. The factor V (F5) Leiden mutation has been suggested to be a genetic risk factor for venous thromboembolism and osteonecrosis in Caucasian individuals, however, this association remains controversial in other populations. The present study aimed to identify polymorphisms of the F5 gene and performed a case‑control study in a Korean population. The F5 gene was sequenced in 24 unrelated Korean individuals, and 16 polymorphisms were detected. A total of six polymorphisms were genotyped in 423 patients with ONFH and 348 control individuals. Analysis of the association between genotyped single nucleotide polymorphisms and haplotypes and with ONFH was performed. Comparison of the ONFH samples and the control individuals using logistic regression models revealed no statistically significant difference in the frequencies of the F5 polymorphisms and haplotypes. These findings suggested that F5 polymorphisms were not significant in the susceptibility to ONFH in the Korean population.

Tracing hepatitis B virus to the 16th century in a Korean mummy

A rare find of a mummified child from the 16th century AD, in Korea, with relatively preserved organs, enabled a search for ancient hepatitis B virus (aHBV) DNA sequences from laparoscopic-derived liver biopsies. Analysis of the complete aHBV genome (3,215 base pairs) revealed a unique HBV genotype C2 (HBV/C2) sequence commonly spread in Southeast Asia, which probably represents an HBV that infected the Joseon Dynasty population in Korea. Comparison of the aHBV sequences with contemporary HBV/C2 DNA sequences revealed distinctive differences along four open reading frames. Genetic diversity between contemporary and recovered aHBV/C2 DNA may be the result of immunologic, environmental, and/or pharmacologic pressures. The calculated time of most recent common ancestor suggests that the Korean HBV sequence origin dates back at least 3,000 years and possibly as long as 100,000 years. This isolate most likely represents the earliest human HBV sequence that colonized Southeast Asia by human migration.

CONCLUSION

This study describes the complete sequence of the oldest HBV isolate and the most ancient full viral genome known so far.

Perspectives on human population structure at the cusp of the sequencing era

Human groups show structured levels of genetic similarity as a consequence of factors such as geographical subdivision and genetic drift. Surveying this structure gives us a scientific perspective on human origins, sheds light on evolutionary processes that shape both human adaptation and disease, and is integral to effectively carrying out the mission of global medical genetics and personalized medicine. Surveys of population structure have been ongoing for decades, but in the past three years, single-nucleotide-polymorphism (SNP) array technology has provided unprecedented detail on human population structure at global and regional scales. These studies have confirmed well-known relationships between distantly related populations and uncovered previously unresolvable relationships among closely related human groups. SNPs represent the first dense genome-wide markers, and as such, their analysis has raised many challenges and insights relevant to the study of population genetics with whole-genome sequences. Here we draw on the lessons from these studies to anticipate the directions that will be most fruitful to pursue during the emerging whole-genome sequencing era.