Y chromosome haplogroup N in a Japanese population is classified into three subclades, and two DYS385 loci, a duplicated Y-STR, are duplicated again in subclade N-M1819.

DYS385 is one of the major Y chromosome short tandem repeats (Y-STRs) in forensic genetics and exists as 2 copies in the human Y chromosome palindrome P4 region. In this study, we found that some samples were estimated to have ≥ 4 copies of DYS385 in Y chromosome haplogroup N in a Japanese population. Y chromosome haplogroup N is distributed widely in eastern/central Asia, Siberia, and eastern/northern Europe, and is also observed in Japan; however, little is known about haplogroup N subclades in the Japanese population. To reveal the link between increased DYS385 copy number and haplogroup N subclades, we sequenced single nucleotide polymorphisms to classify the subclades. As a result, the Japanese Y chromosomes of haplogroup N were classified into three subclades, and an increased DYS385 copy number was specific to subclade N-M1819* (N1b2*). These results are of use in forensic DNA analysis because Y-STR copy number is important for the interpretation of Y-STR typing results of male DNA mixtures and kinship analysis. We also found that DYS458.1 microvariants (DYS458 intermediate alleles with single-nucleotide insertion) were observed only in subclade N-CTS962 (N1b1b∼) samples. Given that previous studies reported that DYS458.1 microvariants are observed in Y chromosomes of haplogroup N in other populations, DYS458.1 might be used to infer haplogroup N subclades without limitation to the Japanese population. The results of this study will be beneficial not only to forensic genetics but also to anthropological studies.

Development and validation of a SYBR green-based mitochondrial DNA quantification method by following the MIQE and other guidelines.

In forensic mitochondrial DNA (mtDNA) analysis, quantitative PCR (qPCR) is usually performed to obtain high-quality sequence data for subsequent Sanger or massively parallel sequencing. Unlike methods for nuclear DNA quantification using qPCR, a calibrator is necessary to obtain mtDNA concentrations (i.e., copies/µL). Herein, we developed and validated a mtDNA quantification method based on a SYBR Green assay by following MIQE [Bustin et al., Clin. Chem. 55 (2009) 611-22] and other guidelines. Primers were designed to amplify nucleotide positions 16,190-16,420 in hypervariable region 1 for qPCR using PowerUp SYBR Green and QuantStudio 5. The optimized conditions were 0.3 µM each primer and an annealing temperature of 60 °C under a 2-step cycling protocol. K562 DNA at 100 pg/µL was converted into a mtDNA concentration of 16,400 copies/µL using linearized plasmid DNA. This mtDNA calibrator was obtained by cloning the synthesized DNA fragments of mtDNA (positions 16,140-16,470) containing a 100-bp inversion. The linear dynamic range of the K562 standard curve was 10,000-0.1 pg/µL (r2 ≥ 0.999). The accuracy was examined using NIST SRM 2372a, and its components A, B, and C were quantified with differences of -29.4%, -35.0%, and -22.0%, respectively, against the mtDNA concentrations calculated from published NIST data. We also examined the specificity of the primers, stability of the reaction mix, precision, tolerance against PCR inhibitors, and cross-reactivity against DNA from various animal taxa. Our newly developed mtDNA quantification method is expected to be useful for forensic mtDNA analysis.

Poly_NumtS_430 or HSA_NumtS_587 observed in massively parallel sequencing of the mitochondrial HV1 and HV2 regions.

An increasing number of studies on massively parallel sequencing of mitochondrial DNA (mtDNA) have been reporting identification of various types of noise or off-target sequences. Herein, we report that an off-target haplotype (sequence length 192 bp) observed in MiSeq data of mtDNA at nucleotide position 16,209-16,400 was likely caused by polymorphic nuclear mitochondrial DNA sequences (NumtS). Buccal DNA samples from Volunteers #001-004 and Control DNA 007 were amplified with our multiplex system of the B (15,998-16,172), C (16,209-16,400), and E (30-289) regions using 2000 copies of mtDNA. A sample index was added using a Nextera XT index kit, and MiSeq Reagent Nano Kit v2 was used in 2 × 251 cycles on a MiSeq FGx. FASTQ files were analyzed by CLC Genomics Workbench 21.0.3. The extracted SAM files were analyzed using our original Excel macro to sum up the read counts as the phased variant calls for each region. An off-target haplotype differing at 19 sites against the revised Cambridge reference sequence was observed in Volunteer #001 (4 in 10 MiSeq data), Volunteer #002 (2 in 9), and Control DNA 007 (6 in 9). In a BLAST search, the sequence of the off-target haplotype matched perfectly to three polymorphic NumtS (Poly_NumtS_430 [KM281528.1], HSA_NumtS_587 [HE613849.1], and nuclear fossil [S80333.1]) and BAC clone of chromosome 11 (AC107937.2). The sequence also matched perfectly to a Filipino mtDNA (KC993973.1) which was inferred as a chimeric sequence of mtDNA and the HSA_NumtS_587. The sequence of the off-target haplotype was not contained in the latest human reference genome sequence (GRCh38.p13). In a phylogenetic tree, the off-target haplotype was genetically distant from modern human mtDNA and not directly connected to them. In conclusion, observed off-target haplotype amplified by our multiplex system was likely caused by Poly_NumtS_430 or HSA_NumtS_587.

Massively parallel sequencing data of 31 autosomal STR loci obtained using the Precision ID GlobalFiler NGS STR Panel v2 for 82 Japanese population samples.

Allele frequencies for 31 autosomal short tandem repeat (STR) loci (CSF1PO, D10S1248, D12ATA63, D12S391, D13S317, D14S1434, D16S539, D18S51, D19S433, D1S1656, D1S1677, D21S11, D22S1045, D2S1338, D2S1776, D2S441, D3S1358, D3S4529, D4S2408, D5S2800, D5S818, D6S1043, D6S474, D7S820, D8S1179, FGA, Penta D, Penta E, TH01, TPOX, and vWA) were obtained using Precision ID GlobalFiler NGS STR Panel v2 from 82 unrelated individuals sampled from the Japanese population. Autosomal STR alleles designated by NGS and conventional capillary electrophoresis were found to be concordant except at D2S441 allele 9.

Frequencies of D19S433 silent alleles in a Japanese population of 1501 individuals and their effect on likelihood ratios calculated in kinship tests.

Although silent alleles in D19S433 typing using the GlobalFiler PCR Amplification Kit have been reported, the exact frequency of the D19S433 silent alleles in population data of 1501 Japanese individuals, which are widely used for the assessment of Japanese STR typing results, is unclear. In this study, we examined the exact D19S433 silent allele frequency in this population data. We newly observed the G32A variant causing silent alleles at D19S433 in five samples. Combining them with data including 30 samples with the variant reported previously, we determined that the total frequency of the silent alleles (i.e. the frequency of the G32A variant) in the 1501 Japanese samples was 0.0117 (35/3002). Using the D19S433 allele frequency data, we evaluated the effect of presence/absence information for the D19S433 silent allele on kinship tests. Likelihood ratios (LRs) were calculated for both simulated parent-child and full sibling cases, revealing that the LR may change by approximately 10-2 to 103 fold when the presence/absence of the D19S433 silent allele is revealed in a kinship test. Therefore, if a sufficiently large or small LR is obtained, there is little need to determine the presence/absence of the D19S433 silent allele in Japanese kinship tests using GlobalFiler. This study will be beneficial for the assessment of Japanese human identification and kinship test results using GlobalFiler.

Development and validation of Kongoh ver. 3.0.1: Open-source software for DNA mixture interpretation in the GlobalFiler system based on a quantitative continuous model.

Probabilistic genotyping software based on continuous models is effective for interpreting DNA profiles derived from DNA mixtures and small DNA samples. In this study, we updated our previously developed Kongoh software (to ver. 3.0.1) to interpret DNA profiles typed using the GlobalFiler™ PCR Amplification Kit. Recently, highly sensitive typing systems such as the GlobalFiler system have facilitated the detection of forward, double-back, and minus 2-nt stutters; therefore, we implemented statistical models for these stutters in Kongoh. In addition, we validated the new version of Kongoh using 2-4-person mixtures and DNA profiles with degradation in the GlobalFiler system. The likelihood ratios (LRs) for true contributors and non-contributors were well separated as the information increased (i.e., larger peak height and fewer contributors), and these LRs tended to neutrality as the information decreased. These trends were observed even in profiles with DNA degradation. The LR values were highly reproducible, and the accuracy of the calculation was also confirmed. Therefore, Kongoh ver. 3.0.1 is useful for interpreting DNA mixtures and degraded DNA samples in the GlobalFiler system.

Evaluation of probability distribution models for stutter ratios in the typing system of GlobalFiler and 3500xL Genetic Analyzer.

As DNA typing systems have become increasingly sensitive in recent years, probability distribution models for back, forward, double-back, and minus 2-nt stutter ratios have been desired to be considered in DNA evidence interpretation using specific software programs. However, experimental investigations have been insufficient, especially for forward, double-back, and minus 2-nt stutters. In this study, we experimentally reevaluated the probability distribution models for each stutter ratio in the typing systems of GlobalFiler™ PCR Amplification Kit and 3500xL Genetic Analyzer from Thermo Fisher Scientific. In addition, to enhance the reliability of longest uninterrupted stretch (LUS) values and corrected allele numbers used in previously developed models for stutter ratios using sequence information (i.e., LUS model and multi-seq model), we propose the weighted average of LUS values and corrected allele numbers based on the number of observations in sequence-based population data. Back stutter ratios demonstrated a positive correlation with allele numbers (allele model) in eight loci, LUS values (LUS model) in eight loci, and corrected allele numbers (multi-seq model) in five loci. The forward stutter ratios (FSRs) of D22S1045 followed the LUS model. FSRs other than D22S1045 and double-back stutter ratios followed the LUS model by considering multiple loci together. Minus 2-nt stutter ratios observed in SE33 and D1S1656 did not increase with the increase in the allele numbers. The adopted models for each stutter ratio can be implemented in software programs for DNA evidence interpretation and enable a reliable interpretation of crime stain profiles in forensic caseworks.

Differences in DYF387S1 copy number distribution among haplogroups caused by haplogroup-specific ancestral Y-chromosome mutations.

DYF387S1 is a major Y-chromosome short tandem repeat (Y-STR) used in forensic genetics that is included in the Y-chromosomal haplotype reference database (YHRD, https://yhrd.org) and it is known as a rapidly mutating Y-STR. DYF387S1 is a multi-locus marker and the two paralogs are within a palindromic sequence which is a region prone to structural chromosome mutation. In this study, we investigated DYF387S1 copy number distribution and separately typed the two DYF387S1 paralogs in a Japanese population. We found different DYF387S1 copy numbers among haplogroups indicating that the differences had been caused by haplogroup-specific ancestral Y-chromosomal mutations, such as deletion, duplication and non-allelic gene conversion. In haplogroup C, it is likely that gene conversion between two DYF387S1 paralogs had occurred in the common ancestral Y-chromosome for paragroup C-M130* and duplication of DYF387S1 had occurred in the common ancestral Y-chromosome for haplogroup C-M131. Meanwhile, in haplogroup D, deletion of the upstream DYF387S1 paralog is likely to have occurred in the common ancestral Y-chromosome for paragroup D-M57* and duplication of the remaining DYF387S1 paralog is indicated in the common ancestral Y-chromosome for haplogroup D-M125. In haplogroup O, structural mutations changing the DYF387S1 copy number had probably not occurred in the common ancestral Y-chromosome. We also suggest that deletion of one DYF387S1 paralog occurred in haplogroup N and that deletion of one DYF387S1 paralog or DYF387S1 gene conversion occurred in haplogroup Q. This is the first study that has separately typed the two DYF387S1 paralogs in a large population dataset. As haplogroups C, D, N, O and Q are also observed in other populations, the ancestral mutation events indicated by this study may have affected DYF387S1 polymorphism in other areas of the world.

Evaluation of Rapid DNA system for buccal swab and disaster victim identification samples.

An evaluation of a Rapid DNA system was performed using buccal swab samples and mock Disaster Victim Identification (DVI) samples collected postmortem. The allelic ladder success rate was 90% and samples analyzed simultaneously with this allelic ladder were used for further analysis. Sample success rate of the Rapid DNA system for buccal swab samples, and blood and muscle DVI samples were calculated. Success rates of buccal swab samples were 100% and 75% using cassettes preloaded with all reagents suitable for high- and low-DNA content samples, respectively. Success rates of fresh DVI samples were 80% to 100%. Success rates of putrefied DVI samples varied widely between 0% and 20% and 50% to 80% depending on cassette and sample types. Conventional DNA analysis was performed for comparison with the results of the Rapid DNA system. DNA quantity and degradation of human DNA were measured using quantitative polymerase chain reaction. DVI samples that yielded more than 1 ng/µL of DNA when extracted with conventional protocols were suitable for analysis using cassettes for both high- and low-DNA content samples. DVI samples with less than 0.1 ng/µL of DNA were suitable only for analysis using cassettes for low-DNA content samples. All alleles called and exported by the Expert system software implemented in the Rapid DNA system were concordant with allele calls made by conventional capillary electrophoresis DNA analysis.

Polymorphisms and microvariant sequences in the Japanese population for 25 Y-STR markers and their relationships to Y-chromosome haplogroups.

Y-chromosomal short tandem repeat (Y-STR) markers have been used for forensic purposes such as kinship analysis of male-linage and detection of a male DNA component in a mixture of male and female DNA. Recently, rapidly mutating Y-STR (RM Y-STR) markers were reported that are expected to help distinguish close male relatives. This study provides data of Y-chromosomal haplotypes for 25 Y-STR markers, including six RM Y-STR markers (DYS576, DYS627, DYS518, DYS570, DYS449 and DYF387S1) typed with the Yfiler™ Plus kit in 1299 males of the Japanese population. Discrimination capacity increased from 87.2% for 16 Y-STR markers with the Yfiler™ kit to 99.6% for 25 Y-STR markers with the Yfiler™ Plus kit. We characterized sequences of observed microvariant alleles of eight Y-STR markers and a low-amplified allele of DYS390 by Sanger sequencing. DYF387S1, a multi-locus Y-STR marker that is located at two positions on the human Y-chromosome, was observed in tri-allelic patterns in 51 of 1299 samples (3.9%) and we found an extremely high frequency of the tri-allelic pattern of DYF387S1 in haplogroup C-M131. We also analyzed Y-STR gene diversity in each haplogroup and its relevance to mutation rates.

Ratios and distances of pull-up peaks observed in GlobalFiler kit data.

Short tandem repeat (STR) analysis is widely used for forensic examinations with a capillary electrophoresis instrument such as the 3500xL Genetic Analyzer. This instrument adapts multi-locus STR kits to examine up to 27 loci using a 6-fluorescent dye system and corrects the spectral overlap between each dye. However, inaccurate spectral correction can cause pull-up peaks. Here, we examined the pull-up peaks observed in GlobalFiler kit data in terms of their peak height ratios and distances from their parent allele peaks when using the 3500xL and the 3130xl Genetic Analyzers. With the 3500xL, 546 pull-up peaks were observed, and their pull-up ratios averaged 1.03 ±â€¯0.32% (range 0.260-2.80%). Of the 546 pull-up peaks, 534 peaks (97.8%) were within ±1 bp from their parent allele peaks. Overall, the pull-up peaks toward adjacent shorter wavelength channels (e.g., from yellow to green) tended to be observed in the left side (shorter bp) of the corresponding parent allele peaks, and the opposite side tendency was observed for those pull-up peaks toward adjacent longer wavelength channels. These tendencies were also observed in the GlobalFiler data generated with the 3130xl and in the data obtained by injecting a J6 matrix standard with LIZ 500 or 600 v2 size standard into the 3500xL and 3130xl. Inspection of raw data revealed that the shift of pull-up peaks from their parent allele peaks was derived from sigmoid, pull-down, or slightly shifted pull-up shapes. Based on the obtained data, we propose a standard for assessment of questionable pull-up peaks.

Purification of cone outer segment for proteomic analysis on its membrane proteins in carp retina.

Rods and cones are both photoreceptors in the retina, but they are different in many aspects including the light response characteristics and, for example, cell morphology and metabolism. These differences would be caused by differences in proteins expressed in rods and cones. To understand the molecular bases of these differences between rods and cones, one of the ways is to compare proteins expressed in rods and cones, and to find those expressed specifically or dominantly. In the present study, we are interested in proteins in the outer segment (OS), the site responsible for generation of rod- or cone-characteristic light responses and also the site showing different morphology between rods and cones. For this, we established a method to purify the OS and the inner segment (IS) of rods and also of cones from purified carp rods and cones, respectively, using sucrose density gradient. In particular, we were interested in proteins tightly bound to the membranes of cone OS. To identify these proteins, we analyzed proteins in some selected regions of an SDS-gel of washed membranes of the OS and the IS obtained from both rods and cones, with Liquid Chromatography-tandem Mass Spectrometry (LC-MS/MS) using a protein database constructed from carp retina. By comparing the lists of the proteins found in the OS and the IS of both rods and cones, we found some proteins present in cone OS membranes specifically or dominantly, in addition to the proteins already known to be present specifically in cone OS.

Substrate specificity and subcellular localization of the aldehyde-alcohol redox-coupling reaction in carp cones.

Our previous study suggested the presence of a novel cone-specific redox reaction that generates 11-cis-retinal from 11-cis-retinol in the carp retina. This reaction is unique in that 1) both 11-cis-retinol and all-trans-retinal were required to produce 11-cis-retinal; 2) together with 11-cis-retinal, all-trans-retinol was produced at a 1:1 ratio; and 3) the addition of enzyme cofactors such as NADP(H) was not necessary. This reaction is probably part of the reactions in a cone-specific retinoid cycle required for cone visual pigment regeneration with the use of 11-cis-retinol supplied from Müller cells. In this study, using purified carp cone membrane preparations, we first confirmed that the reaction is a redox-coupling reaction between retinals and retinols. We further examined the substrate specificity, reaction mechanism, and subcellular localization of this reaction. Oxidation was specific for 11-cis-retinol and 9-cis-retinol. In contrast, reduction showed low specificity: many aldehydes, including all-trans-, 9-cis-, 11-cis-, and 13-cis-retinals and even benzaldehyde, supported the reaction. On the basis of kinetic studies of this reaction (aldehyde-alcohol redox-coupling reaction), we found that formation of a ternary complex of a retinol, an aldehyde, and a postulated enzyme seemed to be necessary, which suggested the presence of both the retinol- and aldehyde-binding sites in this enzyme. A subcellular fractionation study showed that the activity is present almost exclusively in the cone inner segment. These results suggest the presence of an effective production mechanism of 11-cis-retinal in the cone inner segment to regenerate visual pigment.