Estimation of the number of contributors to mixed samples of DNA by mitochondrial DNA analyses using massively parallel sequencing.

We evaluated whether the number of contributors to mixed DNA samples can be estimated by analyzing the D-loop of mitochondrial DNA using massively parallel sequencing. The A- (positions 16,209-16,400) and B- (positions 30-284) amplicons in hypervariable regions 1 and 2, respectively, were sequenced using MiSeq with 2 × 251 cycles. Sequence extraction and trimming were performed using CLC Genomics Workbench 11 and the number of observed haplotypes was counted for each amplicon type using Microsoft Excel. The haplotype ratios were calculated by dividing the number of counted reads of the corresponding haplotype by the total number of sequence reads. Haplotypes that were over the threshold (5%) were defined as positive haplotypes. The number of larger positive haplotypes in either of the two amplicon types was defined as the number of contributors. Samples were collected from seven individuals. Seventeen mixed samples were prepared by mixing DNA from two to five contributors at various ratios. The number of contributors was correctly estimated from almost all of the mixed samples containing equal amounts of DNA from two to five people. In mixed samples of two or three people, the minor components were detected down to a ratio of 20:1 or 8:2:1. However, heteroplasmy, base deletions, and sharing of the same haplotypes caused incorrect estimations of the number of contributors. Although this method still has room for improvement, it may be useful for estimating the number of contributors in a mixed sample, as it does not rely on forensic mathematics.

Rapid detection of pathogenic virus genome sequence from throat and nasal swab samples using an exhaustive gene amplification method.

Rapid identification of pathogenic agents is important in response to the emergence of biocrime and bioterrorism, to facilitate appropriate confinement and treatment. As the rapid determination system of viral genome sequences (RDV method) using exhaustive gene amplification is useful for rapid identification, we examined whether this method could be applied to forensic samples. To detect pathogenic virus in a cat with suspected viral infections, fluid swab samples were applied to the RDV method. The following steps were performed: viral propagation, extraction of the viral genome, amplification of the first library, fragmentation of the library, amplification of the second library using non-specific primer sets, and direct sequencing of the amplicon. To confirm the viruses detected by this method, we performed conventional PCR using virus-specific primers. We detected pathogenic virus genome sequences from the swab samples and confirmed infection with these viruses. In addition, we directly detected a viral genome sequence from the nasal swab sample without the viral propagation step. The RDV method is infrequently used in forensic analysis. This method is practicable with equipment existing in a normal laboratory and is useful for rapid detection and identification of pathogenic viruses in forensic samples. This method would also be applicable to the detection of bacteria and fungi.

Analysis Comparison for Rapid Identification of Pathogenic Virus from Infected Tissue Samples.

When examining infectious samples, rapid identification of the pathogenic agent is required for diagnosis and treatment or for investigating the cause of death. In our previous study, we applied exhaustive amplification using non-specific primers (the rapid determination system of viral genome sequences, the RDV method) to identify the causative virus via swab samples from a cat with a suspected viral infection. The purpose of the current study is to investigate suitable methods for the rapid identification of causative pathogens from infected tissue samples. First, the influenza virus was inoculated into mice to prepare infected tissue samples. RNA extracted from the mouse lung homogenates was transcribed into cDNA and then analyzed using the RDV method and next-generation sequencing, using MiSeq and MinION sequencers. The RDV method was unable to detect the influenza virus in the infected tissue samples. However, influenza virus reads were detected using next-generation sequencing. Comparing MiSeq and MinION, the time required for library and sequence preparation was shorter for MinION sequencing than for MiSeq sequencing. We conclude that when a causative virus needs to be rapidly identified from an infectious sample, MinION sequencing is currently the method of choice.

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.

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.

Infiltration of T lymphocytes and expression of icam-1 in the hippocampus of patients with hippocampal sclerosis.

We and others have previously shown that reactive microglia express the major histocompatibility complex (MHC) class I and class II antigens in the hippocampus of patients suffering from epilepsy. Although the MHC glycoproteins serve as restriction elements for T lymphocytes, there is little information available regarding T lymphocytes in hippocampal sclerosis. In the present study, we investigated T lymphocyte infiltration in human hippocampi in four cases of epilepsy with hippocampal sclerosis, as well as in four control cases without neurological disease. No CD8- or CD4-positive T lymphocytes were seen in hippocampi from the control cases. In contrast, CD8- and CD4-positive T lymphocytes had infiltrated into the hippocampi of patients with hippocampal sclerosis. In addition, expression of intercellular adhesion molecule-1 was diffusely upregulated in the hippocampi with hippocampal sclerosis. These results indicate that T lymphocyte infiltration is involved in the pathology of hippocampal sclerosis.

Heteroplasmies detected in an amplified mitochondrial DNA control region from a small amount of template.

When mitochondrial DNA (mtDNA) heteroplasmies are detected, they often confound forensic identification, especially if they are the result of poor biological sampling. In this study, we determined the ratio of heteroplasmy in samples that were amplified from a very small amount of template mtDNA or a few cells using a highly sensitive nested polymerase chain reaction (PCR) procedure and a direct sequencing analysis. As a result, more than half of the detected sequences (i.e., 17/20, 15/20, and 14/20) showed homoplasmy derived from a variation in the heteroplasmy proportion when only 10 copies of template mtDNA samples were amplified and analyzed. Additionally, with products amplified from one or several white blood cells (WBCs), several previously undetected heteroplasmies were detected. These results indicate the risks associated with using highly sensitive mtDNA techniques in forensic investigations because of the variable proportions of heteroplasmy or nucleotide substitutions that can possibly be detected from a very small biological sample.

Non-specific peaks generated by animal DNA during human STR analysis: Peak characteristics and a novel analysis method for mixed human/animal samples.

Forensic human identification (HID) laboratories occasionally encounter non-specific peaks generated by non-human DNA. Casework samples for human short tandem repeat (STR) profiling may be contaminated by animal DNA because of the specific environment or situation from which they were obtained. Validation studies for HID kits have reported that non-specific peaks generated from some animals are observed near the human amelogenin peak. In this study, we first revealed that DNA sequences associated with the non-specific peaks generated from animal DNA differ from one animal family to the other. However, non-specific peaks cannot be analyzed using the remainder of polymerase chain reaction (PCR) products left over from conventional HID kits when human and animal DNA are mixed. To overcome this issue, we have developed a novel analysis method of using non-specific peaks generated from animal DNA in human STR profiling to identify the source of contaminating animal DNA at the family level. The method applied here is termed as blocking PCR, which involves selective animal DNA re-amplification by blocking nontarget human amelogenin DNA amplification using an oligonucleotide probe that specifically binds to human amelogenin using the remaining PCR product from the HID kit. Our data demonstrated that HID and family discrimination among animals that are often encountered in forensic contexts could be performed simultaneously. This study enabled recovery of more information from limited quantities of casework samples contaminated with animal DNA, which would be useful for forensic HID scientists.

A case of meningococcal meningitis that was difficult to treat owing to concurrent ventriculitis.

A 64-year-old male came to our hospital emergency department with fever and consciousness disturbance. Culture tests of blood and spinal fluid samples revealed meningococci (Neisseria meningitidis), and we made a diagnosis of meningococcal meningitis. Brain magnetic resonance imaging (MRI) findings revealed ventriculitis. Ceftriaxone was administered for 17 days, however, relapse was noted after that was discontinued, with neutropenia and renal impairment thought to be adverse reactions to the beta-lactam antibiotic. Hence, treatment was switched to oral administration of moxifloxacin for a total of 12 weeks, including in an outpatient setting. After moxifloxacin was discontinued, no side effects or relapse were seen, and treatment was ended. Although antibacterial agents generally show favorable effects for meningococcal meningitis, we consider that sufficient antimicrobial therapy is difficult in cases complicated with ventriculitis.

D5S818 Typing Discrepancy Between PowerPlex(®) Fusion and Other STR Kits Including GlobalFiler(®) Caused by a One-base Deletion in 31 Nucleotides Upstream of the Repeat Region.

Short tandem repeat (STR) typing is widely used in forensic investigation. When the same DNA sample is analyzed with different STR typing kits, a typing discrepancy is occasionally observed. In this study, we examined the cause of a typing discrepancy in a sample at D5S818 locus. This sample was designated as 10, 12 using Identifiler(®) , Identifiler(®) Plus, GlobalFiler(®) , PowerPlex(®) 16HS, and PowerPlex(®) 18D, but as 9.3, 12 using PowerPlex(®) Fusion. Sequencing results indicated that the shorter allele in the sample had a deletion (U31Tdel) at 31 nucleotides upstream of the repeat region (AGAT)10 . This deletion was located in the binding site of the published D5S818 forward primer in PowerPlex(®) 16 and was only 9 and 11 nucleotides downstream of our estimated 5' end position of D5S818 forward primer in GlobalFiler(®) and PowerPlex(®) 18D, respectively. We also examined the effect of primer length on the heterozygous peak balance in this sample.

Estimating allele dropout probabilities by logistic regression: Assessments using Applied Biosystems 3500xL and 3130xl Genetic Analyzers with various commercially available human identification kits.

Phenomena called allele dropouts are often observed in crime stain profiles. Allele dropouts are generated because one of a pair of heterozygous alleles is underrepresented by stochastic influences and is indicated by a low peak detection threshold. Therefore, it is important that such risks are statistically evaluated. In recent years, attempts to interpret allele dropout probabilities by logistic regression using the information on peak heights have been reported. However, these previous studies are limited to the use of a human identification kit and fragment analyzer. In the present study, we calculated allele dropout probabilities by logistic regression using contemporary capillary electrophoresis instruments, 3500xL Genetic Analyzer and 3130xl Genetic Analyzer with various commercially available human identification kits such as AmpFℓSTR® Identifiler® Plus PCR Amplification Kit. Furthermore, the differences in logistic curves between peak detection thresholds using analytical threshold (AT) and values recommended by the manufacturer were compared. The standard logistic curves for calculating allele dropout probabilities from the peak height of sister alleles were characterized. The present study confirmed that ATs were lower than the values recommended by the manufacturer in human identification kits; therefore, it is possible to reduce allele dropout probabilities and obtain more information using AT as the peak detection threshold.

Next-generation sequencing analysis of off-ladder alleles due to migration shift caused by sequence variation at D12S391 locus.

In short tandem repeat (STR) analysis, length polymorphisms are detected by capillary electrophoresis (CE). At most STR loci, mobility shift due to sequence variation in the repeat region was thought not to affect the typing results. In our recent population studies of 1501 Japanese individuals, off-ladder calls were observed at the D12S391 locus using PowerPlex Fusion in nine samples for allele 22, one sample for allele 25, and one sample for allele 26. However, these samples were typed as ordinary alleles within the bins using GlobalFiler. In this study, next-generation sequencing analysis using MiSeq was performed for the D12S391 locus from the 11 off-ladder samples and 33 other samples, as well as the allelic ladders of PowerPlex Fusion and GlobalFiler. All off-ladder allele 22 in the nine samples had [AGAT]11[AGAC]11 as a repeat structure, while the corresponding allele was [AGAT]15[AGAC]6[AGAT] for the PowerPlex Fusion ladder, and [AGAT]13[AGAC]9 for the GlobalFiler ladder. Overall, as the number of [AGAT] in the repeat structure decreased at the D12S391 locus, the peak migrated more slowly using PowerPlex Fusion, the reverse strand of which was labeled, and it migrated more rapidly using GlobalFiler, the forward strand of which was labeled. The allelic ladders of both STR kits were reamplified with our small amplicon D12S391 primers and their mobility was also examined. In conclusion, off-ladder observations of allele 22 at the D12S391 locus using PowerPlex Fusion were mainly attributed to a relatively large difference of the repeat structure between its allelic ladder and off-ladder allele 22.

Genotyping of Toxic Pufferfish Based on Specific PCR-RFLP Products As Determined by Liquid Chromatography/Quadrupole-Orbitrap Hybrid Mass Spectrometry.

A method based on liquid chromatography-electrospray mass spectrometric analysis of the enzymatically digested amplicons derived from the mitochondrial 16S rRNA gene was established for the discrimination of toxic pufferfish. A MonoBis C18 narrow-bore silica monolith column (Kyoto Monotech) and a Q Exactive mass spectrometer (Thermo Fisher) were employed for separation and detection, respectively. Monoisotopic masses of the oligonucleotides were calculated using Protein Deconvolution 3.0 software (Thermo Fisher). Although a lock mass standard was not used, excellent accuracy (mass error, 0.83 ppm on average) and precision (relative standard deviation, 0.49 ppm on average) were achieved, and a mass accuracy of <2.8 ppm was maintained for at least 180 h without additional calibration. The present method was applied to 29 pufferfish samples, and results were consistent with Sanger sequencing.

Allele frequencies for 21 autosomal short tandem repeat loci obtained using GlobalFiler in a sample of 1501 individuals from the Japanese population.

Allele frequencies for 21 autosomal short tandem repeat loci (D3S1358, vWA, D16S539, CSF1PO, TPOX, D8S1179, D21S11, D18S51, D2S441, D19S433, TH01, FGA, D22S1045, D5S818, D13S317, D7S820, SE33, D10S1248, D1S1656, D12S391, and D2S1338) were obtained using the GlobalFiler kit from 1501 unrelated individuals sampled from the Japanese population.

Allele frequencies for 22 autosomal short tandem repeat loci obtained by PowerPlex Fusion in a sample of 1501 individuals from the Japanese population.

Allele frequencies for 22 autosomal short tandem repeat loci (D3S1358, D1S1656, D2S441, D10S1248, D13S317, Penta E, D16S539, D18S51, D2S1338, CSF1PO, Penta D, TH01, vWA, D21S11, D7S820, D5S818, TPOX, D8S1179, D12S391, D19S433, FGA, and D22S1045) were obtained from 1501 unrelated individuals sampled from the Japanese population.

Estimation of the detection rate in STR analysis by determining the DNA degradation ratio using quantitative PCR.

Performing short tandem repeat (STR) analysis from degraded DNA is a challenge for forensic biologists. For assessing the quality and quantity of DNA, we developed quantitative PCR assays to determine the extent of DNA degradation. Quantitative PCR assays using primers that generate two sizes of amplicons from the same region of genomic DNA were used to determine the extent of DNA degradation. These quantitative PCR assays were used with artificially degraded DNA and degraded DNA extracted from aged bloodstains. Increased DNA degradation correlated with a decrease in the number of detectable loci in STR analysis. The extent of DNA degradation and the number of loci detected by STR analysis varied depending on the method of degradation. The extent of degradation of DNA extracted from aged bloodstains correlated well with that of DNA artificially degraded by DNase I in the presence of Mn(2+). Thus, determination of the extent of DNA degradation was helpful for estimating the number of detectable loci. Furthermore, this estimation method is expected to save time and labor, and is particularly suitable when only a limited amount of DNA can be extracted from casework samples.

A comparison of DNA extraction using AutoMate Express™ and EZ1 advanced XL from liquid blood, bloodstains, and semen stains.

In this study, DNA was extracted using an AutoMate Express™ and an EZ1 Advanced XL from liquid blood, fresh and aged bloodstains, and fresh and aged semen stains. Extracted DNA was quantified by real-time PCR using the D17Z1 locus. Short tandem repeat typing was performed using an AmpFℓSTR(®) Identifiler kit. The yields of DNA obtained by the AutoMate Express™ were higher from fresh bloodstains and fresh semen stains, almost the same from aged bloodstains and aged semen stains, but slightly lower from liquid blood compared with those obtained by the EZ1 Advanced XL. The addition of dithiothreitol or the use of PrepFiler™ lysis buffer improved the EZ1 Advanced XL results from fresh bloodstains, but not for liquid blood and aged bloodstains. Our results demonstrated that the PrepFiler™ lysis buffer is the main contributor to the higher DNA yields of the AutoMate Express™ for fresh bloodstains.

A forensic method for the simultaneous analysis of biallelic markers identifying Y chromosome haplogroups inferred as having originated in Asia and the Japanese archipelago.

Information regarding the ancestral and geographical origins of biological evidence samples may be useful for crime investigators as they narrow down the possible donors of the sample. A method for simultaneous analysis of seven biallelic markers (M130, M131, M57, M125, M175, M122 and M134) was developed for forensic application. M57, M125 and M131 are included to identify haplogroups inferred as having originated in the Japanese archipelago. Our method employs allele-specific PCR and fragment analysis using fluorescently labeled primers and capillary electrophoresis. This method can be used to assign a haplogroup from both of degraded male DNA samples and DNA samples containing a mixture of female and male DNA by designing PCR primers that generate small amplicons and are highly specific for targets on the Y chromosome. A total of 1346 samples from Japanese males collected from the four major islands and Okinawa island were classified into seven Y binary haplogroups i.e., C-M130, C-M131, D-M57, D-M125, O-M175, O-M122 and O-M134, and a "no-mutation detected" group and their frequencies were 0.0617, 0.0565, 0.1441, 0.182, 0.3418, 0.11, 0.0847 and 0.0193, respectively. Samples of "no-mutation detected" were further analyzed by direct sequencing for identification of the major haplogroup to which they belong. Along with the haplogroup data, we report haplotype data for the 16 Y-STR markers included in the AmpFlSTR Yfiler PCR amplification kit (Applied Biosystems). These data will be useful in the prediction of haplogroups based on Y-STR haplotypes.