Nam Soo Cho

A large population genetic study of 15 autosomal short tandem repeat loci for establishment of Korean DNA profile database.

Genotyping of highly polymorphic short tandem repeat (STR) markers is widely used for the genetic identification of individuals in forensic DNA analyses and in paternity disputes. The National DNA Profile Databank recently established by the DNA Identification Act in Korea contains the computerized STR DNA profiles of individuals convicted of crimes. For the establishment of a large autosomal STR loci population database, 1805 samples were obtained at random from Korean individuals and 15 autosomal STR markers were analyzed using the AmpFlSTR Identifiler PCR Amplification kit. For the 15 autosomal STR markers, no deviations from the Hardy-Weinberg equilibrium were observed. The most informative locus in our data set was the D2S1338 with a discrimination power of 0.9699. The combined matching probability was 1.521 × 10−17. This large STR profile dataset including atypical alleles will be important for the establishment of the Korean DNA database and for forensic applications.

Genetic polymorphisms of 16 Y chromosomal STR loci in Korean population

Allele frequencies and haplotypes of 16 Y chromosomal STR loci included in the AmpFlSTR((R)) Yfilertrade mark system were obtained from a sample of 526 unrelated Korean male individuals. A total of 478 haplotypes were observed in the 526 individuals studied, of which 440 were unique. The overall haplotype diversity for the 16 Y-STR loci was 0.9996, and the discrimination capacity was 0.9087. We found 13 atypical alleles, including null, duplicated and microvariant alleles. Microvariants have been characterized by sequencing, 14.1 allele at DYS458 showing the flanking site mutation, 13.1 and 15.2 allele at DYS385a/b showing changes in the repeat structure.

Mutational analysis of whole mitochondrial DNA in patients with MELAS and MERRF diseases

Mitochondrial diseases are clinically and genetically heterogeneous disorders, which make the exact diagnosis and classification difficult. The purpose of this study was to identify pathogenic mtDNA mutations in 61 Korean unrelated families (or isolated patients) with MELAS or MERRF. In particular, the mtDNA sequences were completely determined for 49 patients. From the mutational analysis of mtDNA obtained from blood, 5 confirmed pathogenic mutations were identified in 17 families, and 4 unreported pathogenically suspected mutations were identified in 4 families. The m.3243A>G in the tRNALeu(UUR) was predominantly observed in 10 MELAS families, and followed by m.8344A>G in the tRNALys of 4 MERRF families. Most pathogenic mutations showed heteroplasmy, and the rates were considerably different within the familial members. Patients with a higher rate of mutations showed a tendency of having more severe clinical phenotypes, but not in all cases. This study will be helpful for the molecular diagnosis of mitochondrial diseases, as well as establishment of mtDNA database in Koreans.

Population genetic polymorphisms of 17 Y-chromosomal STR loci in South Koreans

Haplotypes and allele frequencies of 17 Y-chromosomal STR loci included in the AmpFlSTR(®) Yfiler(®) system were obtained from a sample of 1021 unrelated individuals living in 6 provinces of South Korea. A total of 938 haplotypes were observed in the 1021 individuals studied, of which 885 were unique. The overall haplotype diversity for the 17 Y-STR loci was 0.9998, and the discrimination capacity was 0.9187. We found 11 atypical alleles (null, duplicated, triplicated, and microvariant alleles), that have not previously been reported in South Korean populations. It seems that these 17 loci are useful genetic markers for forensic personal identification and paternity testing in the South Korean population.

A preliminary study on the origin of Koreans based on Y-STR variation

To investigate the origin of Koreans, we examined the 12-locus Y-chromosome short tandem repeat (Y-STR) variation in a sample of 310 unrelated males from three localities (Gochang, Andong and Geoje) in Korea and statistically analyzed the previously published four Y-STR databases (n = 1655) of Korean population. The median joining network of 9-locus Y-STR haplotypes inferred as haplogroup O2b-SRY+465 showed a “star cluster” indicative of a population expansion from a centrally positioned haplotype. The central haplotype in the “star cluster” was the most frequently occurring Y-STR haplotype among the Korean male gene pool (6%, 127 of 1965, 10,14,12,13,14,16,13,13,23, for loci DYS391, DYS389I, DYS439, DYS438, DYS437, DYS19, DYS392, DYS393, and DYS390), which was shared among all seven datasets. Based on the “star cluster” pattern from both our data (41%, 128 of 310) and those previously published (34%, 563 of 1655), we suggest that the most frequent Y-STR haplotype among the Korean male gene pool seems to be the Korean modal (ancestral) haplotype. Further study with additional Y-STR and Y-SNP data of the east Asian populations as well as Korean population are needed to providing a genetic clue for the “star cluster” (O2b-SRY+465) associated with the ethnohistoric events of the Koreans.

Y-STR genetic structure of the most common surnames in Korea

The genetic pattern of the Y-chromosomal short tandem repeat (Y-STR) haplotypes of 542 unrelated males having the five most common surnames was analyzed to evaluate their usefulness for Korean forensic science and to provide the basic information for Korean genetic genealogy. We identified 439 Y-STR haplotypes, with 385 (87.7%) being found once. Each of the most common Korean surnames examined here showed high haplotype diversity (>0.9949), indicating that Y-STR haplotypes are very heterogeneous within each surname. Population genetic analysis showed that there are little genetic difference among five surnames due to the genetic heterogeneity within each surname and the various kinds of non surname-specific haplotypes (33.6%: 182/542) distributed among five surnames. Surname prediction may not be adequate for narrowing down the suspect list in Korean forensic science, and additional Y-STR haplotype data of thebon-gwans are needed.