Massive parallel sequencing of short tandem repeats in the Korean population.

STR analysis using capillary electrophoresis has been the most widely used method for forensic DNA typing. Recently, massive parallel sequencing (MPS) technique has been emerging as an innovative tool to supplement or replace the conventional CE process. In this study, we evaluated the application of commercial MiSeqFGx™ forensic signature kit (Illumina Inc., San Diego, CA, USA) in the Korean population, including performance comparison with CE-based STR profiling kits. The genotyping results of 209 unrelated random Korean individuals were summarized according to the International Society for Forensic Genetics guideline. The study revealed that 26 novel sequence variations in autosomal STR were newly found that had not been previously reported in other forensic literature. This indicates that MPS may be an effective supplementary tool for forensic DNA typing and the database to increase the discriminatory power of individual identification.

Use of cytochrome c oxidase subunit i (COI) nucleotide sequences for identification of the Korean Luciliinae fly species (Diptera: Calliphoridae) in forensic investigations.

Blowflies, especially species belonging to the subfamily Luciliinae, are the first insects to lay eggs on corpses in Korea. Fast and accurate species identification has been a key task for forensic entomologists. Because conventional morphologic identification methods have many limitations with respect to forensic practice, molecular methods have been proposed to identify fly species of forensic importance. To this end, the authors amplified and sequenced the full length of the cytochrome c oxidase subunit I (COI) gene of the Luciliinae fly species collected in Korea. The results showed the COI sequences are instrumental in identifying Luciliinae fly species. However, when compared with previously reported data, considerable inconsistencies were noted. Hemipyrellia ligurriens data in this study differed significantly from two of the five pre-existing data. Two closely related species, Lucilia illustris and Lucilia caesar, showed an overlap of COI haplotypes due to four European sequences. The results suggest that more individuals from various geographic regions and additive nuclear DNA markers should be analyzed, and morphologic identification keys must be reconfirmed to overcome these inconsistencies.

Forensic evaluation and haplotypes of 19 Y-chromosomal STR loci in Koreans.

In this study, 19 Y-specific STR loci (DYS19, DYS389I/II, DYS390, DYS391, DYS392, DYS393, DYS385, DYS388, DYS434, DYS435, DYS436, DYS437, DYS438, DYS439, DYS446, DYS449, and DYS464) were analyzed in 301 unrelated Korean males by three multiplex PCR systems. The haplotype diversity using the classical set of Y-STRs (DYS19, DYS389I/II, DYS390, DYS391, DYS392, DYS393, and DYS385; multiplex I) was 0.9963. For the same individuals, the haplotype diversity value using the new set of highly informative Y-STRs (DYS385, DYS446, DYS449, and DYS464; multiplex III) was 0.9989, while that using the combined set of Y-STRs by adding DYS388 to the previously studied DYS434, DYS435, DYS436, DYS437, DYS438, and DYS439 (multiplex II) was 0.9509. A total of 297 different haplotypes were identified using the 19 Y-STR markers, of which 293 were unique and 4 were found twice. The overall haplotype diversity was 0.9999. The evaluation of the information of selected markers by combination of each marker with the minimal haplotype showed that DYS434, DYS435, DYS436, DYS437, and DYS438 do not significantly contribute to increment of haplotype diversity. However, respective conjunction of DYS464, DYS449, and DYS446 with the minimal haplotype considerably increased the haplotype diversity. Especially, DYS464 is expected to be the most useful marker that can be included in the expanded minimal haplotype. These results including the haplotype data at 19 Y-STR loci in the present study would provide useful information in forensic practice in a Korean population.

Selection of twenty-four highly informative SNP markers for human identification and paternity analysis in Koreans.

A number of DNA marker types suitable for human identification and parentage testing have been developed, of which single nucleotide polymorphisms (SNPs) merit attention as they are abundant, genetically stable, and amenable to high-throughput automated analysis. In this regard, 24 highly informative SNP markers representing each 22 autosome and both sex chromosomes were selected, and the allele and genotype frequencies of these SNPs were determined in a group composed of 30 unrelated Koreans. Based on frequency data from this group, the estimated probability of identity (P(I)) and probability of paternity exclusion (P(E)) with 22 autosomal SNP loci were 1.905x10(-10) and 98.9%, respectively. The SNPs in this study offer a small but highly accurate database that will be an essential reference for SNP-based forensic application in the future.

Using the developmental gene bicoid to identify species of forensically important blowflies (Diptera: calliphoridae).

Identifying species of insects used to estimate postmortem interval (PMI) is a major subject in forensic entomology. Because forensic insect specimens are morphologically uniform and are obtained at various developmental stages, DNA markers are greatly needed. To develop new autosomal DNA markers to identify species, partial genomic sequences of the bicoid (bcd) genes, containing the homeobox and its flanking sequences, from 12 blowfly species (Aldrichina grahami, Calliphora vicina, Calliphora lata, Triceratopyga calliphoroides, Chrysomya megacephala, Chrysomya pinguis, Phormia regina, Lucilia ampullacea, Lucilia caesar, Lucilia illustris, Hemipyrellia ligurriens and Lucilia sericata; Calliphoridae: Diptera) were determined and analyzed. This study first sequenced the ten blowfly species other than C. vicina and L. sericata. Based on the bcd sequences of these 12 blowfly species, a phylogenetic tree was constructed that discriminates the subfamilies of Calliphoridae (Luciliinae, Chrysomyinae, and Calliphorinae) and most blowfly species. Even partial genomic sequences of about 500 bp can distinguish most blowfly species. The short intron 2 and coding sequences downstream of the bcd homeobox in exon 3 could be utilized to develop DNA markers for forensic applications. These gene sequences are important in the evolution of insect developmental biology and are potentially useful for identifying insect species in forensic science.

Quantitative analyses of postmortem heat shock protein mRNA profiles in the occipital lobes of human cerebral cortices: implications in cause of death.

Quantitative RNA analyses of autopsy materials to diagnose the cause and mechanism of death are challenging tasks in the field of forensic molecular pathology. Alterations in mRNA profiles can be induced by cellular stress responses during supravital reactions as well as by lethal insults at the time of death. Here, we demonstrate that several gene transcripts encoding heat shock proteins (HSPs), a gene family primarily responsible for cellular stress responses, can be differentially expressed in the occipital region of postmortem human cerebral cortices with regard to the cause of death. HSPA2 mRNA levels were higher in subjects who died due to mechanical asphyxiation (ASP), compared with those who died by traumatic injury (TI). By contrast, HSPA7 and A13 gene transcripts were much higher in the TI group than in the ASP and sudden cardiac death (SCD) groups. More importantly, relative abundances between such HSP mRNA species exhibit a stronger correlation to, and thus provide more discriminative information on, the death process than does routine normalization to a housekeeping gene. Therefore, the present study proposes alterations in HSP mRNA composition in the occipital lobe as potential forensic biological markers, which may implicate the cause and process of death.

Y-STR analysis of degraded DNA using reduced-size amplicons.

To increase the success rate of Y-STR genotyping for degraded DNA, we have developed two multiplex PCR sets for 21 Y-STR loci. Besides the 17 Y-STR loci of DYS19, DYS385, DYS389-I, DYS389-II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635, and GATA H4.1 contained in a commercial Y-STR kit, AmpFlSTR Yfiler, the other four loci of DYS388, DYS446, DYS447, and DYS449 were also included in the multiplexes to increase the discrimination capacity. Among a total of 21 Y-STR loci, the primers for eight loci (DYS385, DYS390, DYS438, DYS446, DYS448, DYS449, and DYS635) were newly designed in the present study and nine loci (DYS385, DYS390, DYS391, DYS392, DYS438, DYS439, DYS448, and DYS635) have PCR amplicons smaller than those of the AmpFlSTR Yfiler kit. A sensitivity test using serially diluted standard 9948 male DNA showed that all the values of Y-STR loci in the Y-miniplexes are reliable at template concentrations as low as 30 pg. We compared the effectiveness of the two multiplexes with the AmpFlSTR Yfiler kit by using both enzymatically degraded DNA and 30 samples of 50-year-old skeletal remains. This comparison demonstrated that the new Y-miniplex sets can produce a better signal from degraded DNA than the AmpFlSTR Yfiler kit.

Population data of nine miniSTR loci in Koreans.

For highly degraded DNA samples of forensic casework, new miniSTR systems have been developed to supplement the current STR systems. In the present study, nine miniSTR loci were analyzed in 300 unrelated Koreans using three multiplex PCR systems (multiplex I: D10S1248, D14S1434 and D22S1045; multiplex II: D1S1677, D2S441 and D4S2364; and multiplex III: D3S3053, D6S474 and D20S482), and allele frequencies and forensic parameters were calculated. These data demonstrated that D10S1248, D2S441, D22S1045, D14S1434, and D6S474 are as highly informative as the CODIS STRs suggesting that the miniSTRs could be useful for forensic analysis of degraded DNA.

Haplotypes and mutation analysis of 22 Y-chromosomal STRs in Korean father-son pairs.

We analyzed 369 Korean father/son haplotype transfers in 355 families at 22 Y-STRs (DYS19, DYS389I/II, DYS390, DYS391, DYS392, DYS393, DYS385, DYS388, DYS437, DYS438, DYS439, DYS446, DYS447, DYS448, DYS449, DYS456, DYS458, DYS464, DYS635, and GATA H4.1). A total of 350 haplotypes were observed with an overall haplotype diversity of 0.9999. Among these, 345 were unique and five were found twice. Furthermore, 36 mutations were identified, giving locus-specific mutation rate estimates between 0.0 and 19.0 x 10(-3) per generation and an average mutation rate estimate of 3.9 x 10(-3) (95% CI 2.7-5.4 x 10(-3)). The compilation of Y-STR mutation events for the present study and previous studies demonstrates that DYS449, DYS458, DYS635, DYS456 and DYS439 are the most prone to mutations and that their overall average mutation rate estimate is 2.36 x 10(-3) (95% CI 2.03-2.73 x 10(-33)).

Mitochondrial DNA control region sequences in Koreans: identification of useful variable sites and phylogenetic analysis for mtDNA data quality control.

We have established a high-quality mtDNA control region sequence database for Koreans. To identify polymorphic sites and to determine their frequencies and haplotype frequencies, the complete mtDNA control region was sequenced in 593 Koreans, and major length variants of poly-cytosine tracts in HV2 and HV3 were determined in length heteroplasmic individuals by PCR analysis using fluorescence-labeled primers. Sequence comparison showed that 494 haplotypes defined by 285 variable sites were found when the major poly-cytosine tract genotypes were considered in distinguishing haplotypes, whereas 441 haplotypes were found when the poly-cytosine tracts were ignored. Statistical parameters indicated that analysis of partial mtDNA control region which encompasses the extended regions of HV1 and HV2, CA dinucleotide repeats in HV3 and nucleotide position 16497, 16519, 456, 489 and 499 (HV1ex+HV2ex+HV3CA+5SNPs) and the analysis of another partial mtDNA control region including extended regions of HV1 and HV2, HV3 region and nucleotide position 16497 and 16519 (HV1ex+HV2ex+HV3+2SNPs) can be used as efficient alternatives for the analysis of the entire mtDNA control region in Koreans. Also, we collated the basic informative SNPs, suggested the important mutation motifs for the assignment of East Asian haplogroups, and classified 592 Korean mtDNAs (99.8%) into various East Asian haplogroups or sub-haplogroups. Haplogroup-directed database comparisons confirmed the absence of any major systematic errors in our data, e.g., a mix-up of site designations, base shifts or mistypings.

East Asian mtDNA haplogroup determination in Koreans: haplogroup-level coding region SNP analysis and subhaplogroup-level control region sequence analysis.

The present study analyzed 21 coding region SNP markers and one deletion motif for the determination of East Asian mitochondrial DNA (mtDNA) haplogroups by designing three multiplex systems which apply single base extension methods. Using two multiplex systems, all 593 Korean mtDNAs were allocated into 15 haplogroups: M, D, D4, D5, G, M7, M8, M9, M10, M11, R, R9, B, A, and N9. As the D4 haplotypes occurred most frequently in Koreans, the third multiplex system was used to further define D4 subhaplogroups: D4a, D4b, D4e, D4g, D4h, and D4j. This method allowed the complementation of coding region information with control region mutation motifs and the resultant findings also suggest reliable control region mutation motifs for the assignment of East Asian mtDNA haplogroups. These three multiplex systems produce good results in degraded samples as they contain small PCR products (101-154 bp) for single base extension reactions. SNP scoring was performed in 101 old skeletal remains using these three systems to prove their utility in degraded samples. The sequence analysis of mtDNA control region with high incidence of haplogroup-specific mutations and the selective scoring of highly informative coding region SNPs using the three multiplex systems are useful tools for most applications involving East Asian mtDNA haplogroup determination and haplogroup-directed stringent quality control.

Differential distribution of human mitochondrial DNA in somatic tissues and hairs.

To investigate mitochondrial DNA (mtDNA) distribution within tissues during life, we observed length heteroplasmy in a polycytosine tract of the mitochondrial HV2 region by size-based separation of PCR products, using a mutagenic primer which was designed to avoid stutter production. Blood, brain, heart, liver, skeletal muscle and hair shaft samples were collected during autopsies of 25 individuals. Here, we demonstrate differences in the level of mtDNA length heteroplasmy both within and between individuals and tissues. We also show that mtDNA is distributed randomly in varying proportions in various somatic tissues during growth, resulting in an imbalance in the composition of mtDNA pools among tissues. This mtDNA distribution appears not to be strictly random, and can be explained by the random somatic segregation of nucleoids. On the other hand, significant qualitative/quantitative mtDNA peak pattern variations in hair shafts are thought to be a result of the different developmental origins of hairs. Each hair shaft may have a restricted or clonal set of mtDNA molecules derived from a discrete group of stem cells.

Mitochondrial DNA CA dinucleotide repeats in Koreans: the presence of length heteroplasmy.

The mitochondrial DNA HV3 region contains CA dinucleotide repeats which display length polymorphism. To analyze this for forensic purposes, we designed a fluorescence-labelled PCR primer set for short amplification products and carried out genotyping by using capillary electrophoresis. A total of 4 alleles with 4-7 repeat units were observed and the genetic diversity was estimated to be 0.5120 in 500 unrelated Koreans. Interestingly, three individuals showed two or three length variants, i.e. length heteroplasmy.

Quantitative and qualitative profiling of mitochondrial DNA length heteroplasmy.

Quantitative and qualitative analysis of mitochondrial DNA length heteroplasmy for the first hypervariable segment (HV1) and second hypervariable segment (HV2) regions were performed using size-based separation of fluorescently-labeled polymerase chain reaction (PCR) products by capillary electrophoresis. In this report, the relative proportions of length heteroplasmies in individuals were determined, and each length variant in the heteroplasmic mtDNA mixture was identified. The study demonstrated that 36% and 69% of Koreans show length heteroplasmy in the HV1 and HV2 regions, respectively. Electropherograms revealed that length heteroplasmy in the HV1 region resulted in over 5 length variants in an individual. The peak patterns of length heteroplasmy in the HV1 region were classified into five major types. In the HV2 region, length heteroplasmy resulted in 3-6 length variants in an individual, and showed seven variant peak patterns. The increased knowledge concerning mtDNA length heteroplasmy is believed to not only offer a useful means of determining genetic identity due to increased mitochondrial DNA haplotype diversity by allowing mtDNAs to be classified into several peak patterns, but also represent a promising tool for the diagnosis of several common diseases which are etiologically or prognostically associated with mtDNA polymorphisms.

Genetic characteristics and population study of 4 X-chromosomal STRs in Koreans: evidence for a null allele at DXS9898.

The four X-chromosomal short tandem repeats (STRs), DXS9898, DXS6809, DXS7424 and DXS10011 were analyzed by single multiplex PCR in 150 male and 150 female Koreans. The loss of an allele at DXS9898 was observed in 13 out of 450 chromosomes (2.9%) and the PCR analysis showed that the X-chromosome with a null allele at DXS9898 has more than 1 kb deletion at the DXS9898 locus. Statistical analyses for these four X-STRs showed that they are highly informative for forensic application in Koreans. No linkage disequilibrium was observed among these four STRs and the previously reported five polymorphic STRs, HumARA, DXS101, GATA172D05, HPRTB and DXS8377 in Koreans. The test of homogeneity between allele frequencies revealed that there are some discrepancies in allele distributions between Koreans and Germans.

Five highly informative X-chromosomal STRs in Koreans.

The five X-chromosomal short tandem repeats (STRs) GATA172D05, HPRTB, DXS8377, DXS101 and HumARA were analyzed in 150 males and 150 females from Korea. Markers were amplified in a quadruplex and a monoplex PCR reaction with fluorescently labeled primers. For accurate and reproducible STR typing, sequenced allelic ladders were constructed and a Genotyper macro was programmed. Some differences were found on comparing the allele frequencies of Koreans with those of other populations in DXS8377, DXS101 and HumARA. The forensic efficiency parameters showed that the five X-linked STRs are highly informative for forensic application in Koreans.