Revealing the challenges of low template DNA analysis with the prototype Ion AmpliSeq™ Identity panel v2.3 on the PGM™ Sequencer

Genetic sexing of subadult skeletal remains

When subadult skeletons need to be identified, biological sex diagnosis is one of the first steps in the identification process. Sex assessment of subadults using morphological features is unreliable, and molecular genetic methods were applied in this study. Eighty-three ancient skeletons were used as models for poorly preserved DNA. Three sex-informative markers on the Y and X chromosome were used for sex identification: a qPCR test using the PowerQuant Y target included in PowerQuant System (Promega), the amelogenin test included in ESI 17 Fast STR kit (Promega), and a Y-STR amplification test using the PowerPlex Y-23 kit (Promega). Sex was successfully determined in all but five skeletons. Successful PowerQuant Y-target, Y-amelogenin, and Y-chromosomal STR amplifications proved the presence of male DNA in 35 skeletons, and in 43 subadults female sex was established. No match was found between the genetic profiles of subadult skeletons, and the elimination database and negative control samples produced no profiles, indicating no contamination issue. Our study shows that genetic sex identification is a very successful approach for biological sexing of subadult skeletons whose sex cannot be assessed by anthropological methods. The results of this study are applicable for badly preserved subadult skeletons from routine forensic casework.

Comparison of three massively parallel sequencing platforms for single nucleotide polymorphism (SNP) genotyping in forensic genetics

Three MPS platforms are being used in forensic genetic analysis, i.e., MiSeq FGx, Ion S5 XL, and MGISEQ-2000. However, few studies compared their performance. In this study, we sequenced 83 common SNPs of 71 samples using the ForenSeq™ DNA Signature Prep Kit on MiSeq FGx, the Precision ID Identity Panel on Ion S5 XL, and the MGIEasy Signature Identification Library Prep Kit on MGISEQ-2000 and then the performance was compared. Results showed that the MiSeq FGx had the highest sequence quality but the lowest sequencing depth and allele balance. Discordant genotypes were observed at six SNPs, which may be caused by variants at primer binding regions, indel errors, or misalignments. Besides, two kinds of background noises, allele-specific miscalled reads (ASMR) and allele-nonspecific miscalled reads (ANMR), were characterized. MGISEQ-2000 showed the highest level of ASMR while Ion S5 XL had the highest level of ANMR. Site- and genotype-dependent miscalled patterns were observed at several SNPs on Ion S5 XL and MGISEQ-2000, but few on MiSeq FGx. In conclusion, the three MPS platforms perform differently with respect to sequencing quality, sequencing depth, allele balance, concordance, and background noise. These findings may be useful for data comparison, mixture deconvolution, and heteroplasmy analysis in forensic genetics.

SNP analysis of challenging bone DNA samples using the HID-Ion AmpliSeq™ Identity Panel: facts and artefacts

PCR-MPS is an emerging tool for the analysis of low-quality DNA samples. In this study, we used PCR-MPS to analyse 32 challenging bone DNA samples from three Second World War victims, which previously yielded no results in conventional STR PCR-CE typing. The Identity Panel was used with 27 cycles of PCR. Despite that we only had an average of 6.8 pg of degraded DNA as template, 30 out of 32 libraries (93.8%) produced sequencing data for about 63/90 autosomal markers per sample. Out of the 30 libraries, 14 (46.7%) yielded single source genetic profiles in agreement with the biological identity of the donor, whereas 12 cases (40.0%) resulted in SNP profiles that did not match or were mixed. The misleading outcomes for those 12 cases were likely due to hidden exogenous human contamination, as shown by the higher frequencies of allelic imbalance, unusual high frequencies of allelic drop-ins, high heterozygosity levels in the consensus profiles generated from challenging samples, and traces of amplified molecular products in four out of eight extraction negative controls. Even if the source and the time of the contamination were not identified, it is likely that it occurred along the multi-step bone processing workflow. Our results suggest that only positive identification by statistical tools (e.g. likelihood ratio) should be accepted as reliable; oppositely, the results leading to exclusion should be treated as inconclusive because of potential contamination issues. Finally, strategies are discussed for monitoring the workflow of extremely challenging bone samples in PCR-MPS experiments with an increased number of PCR cycles.

Improving kinship probability in analysis of ancient skeletons using identity SNPs and MPS technology

In forensic kinship analysis and human identification cases, analysis of STRs is the gold standard. When badly preserved ancient DNA is used for kinship analysis, short identity SNPs are more promising for successful amplification. In this work, kinship analysis was performed on two skeletons from the Early Middle Ages. The surface contaminants of petrous bones were removed by chemical cleaning and UV irradiation; DNA was isolated through full demineralization and purified in an EZ1 Advanced XL machine. The PowerQuant kit was used to analyze DNA yield and degradation, and on average, 17 ng DNA/g of petrous bone was obtained. Both skeletons were typed in duplicate for STR markers using the Investigator EssplexPlus SE QS kit, and comparison of partial consensus genotypes showed shared allelic variants at most loci amplified, indicating close kinship. After statistical calculation, the full-sibling kinship probability was too low for kinship confirmation, and additional analyses were performed with PCR-MPS using the Precision ID Identity Panel. The HID Ion Chef Instrument was used to prepare the libraries and for templating and the Ion GeneStudio S5 System for sequencing. Analysis of identity SNPs produced full genetic profiles from both skeletons. For combined likelihood ratio (LR) calculation, the product rule was used, combining LR for STRs and LR for SNPs, and a combined LR of 3.3 × 10⁷ (corresponding to a full-sibling probability of 99.999997%) was calculated. Through the SNP PCR-MPS that followed the STR analysis, full-sibling kinship between the ancient skeletons excavated from an early medieval grave was confirmed.

The effectiveness of various strategies to improve DNA analysis of formaldehyde-damaged tissues from embalmed cadavers for human identification purposes

Formalin-fixed tissues provide the medical and forensic communities with alternative and often last resort sources of DNA for identification or diagnostic purposes. The DNA in these samples can be highly degraded and chemically damaged, making downstream genotyping using short tandem repeats (STRs) challenging. Therefore, the use of alternative genetic markers, methods that pre-amplify the low amount of good quality DNA present, or methods that repair the damaged DNA template may provide more probative genetic information. This study investigated whether whole genome amplification (WGA) and DNA repair could improve STR typing of formaldehyde-damaged (FD) tissues from embalmed cadavers. Additionally, comparative genotyping success using bi-allelic markers, including INDELs and SNPs, was explored. Calculated random match probabilities (RMPs) using traditional STRs, INDEL markers, and two next generation sequencing (NGS) panels were compared across all samples. Overall, results showed that neither WGA nor DNA repair substantially improved STR success rates from formalin-fixed tissue samples. However, when DNA from FD samples was genotyped using INDEL and SNP-based panels, the RMP of each sample was markedly lower than the RMPs calculated from partial STR profiles. Therefore, the results of this study suggest that rather than attempting to improve the quantity and quality of severely damaged and degraded DNA prior to STR typing, a more productive approach may be to target smaller amplicons to provide more discriminatory DNA identifications. Furthermore, an NGS panel with less loci may yield better results when examining FD samples, due to more optimized chemistries that result in greater allelic balance and amplicon coverage.

Eye and Hair Color Prediction of Ancient and Second World War Skeletal Remains Using a Forensic PCR-MPS Approach

To test the usefulness of the forensic PCR-MPS approach to eye and hair color prediction for aged skeletons, a customized version of the PCR-MPS HIrisPlex panel was used on two sets of samples. The first set contained 11 skeletons dated from the 3rd to the 18th centuries AD, and for each of them at least four bone types were analyzed (for a total of 47 samples). In the second set, 24 skeletons from the Second World War were analyzed, and only petrous bones from the skulls were tested. Good-quality libraries were achieved in 83.3% of the cases for the ancient skeletons and in all Second World War petrous bones, with 94.7% and 100% of the markers, respectively, suitable for SNP typing. Consensus typing was achieved for about 91.7% of the markers in 10 out of 11 ancient skeletons, and the HIrisPlex-S webtool was then used to generate phenotypic predictions. Full predictions were achieved for 3 (27.3%) ancient skeletons and 12 (50%) Second World War petrous bones. In the remaining cases, different levels of AUC (area under the receiver operating curve) loss were computed because of no available data (NA) for 8.3% of markers in ancient skeletons and 4.2% of markers in Second World War petrous bones. Although the PCR-based approach has been replaced with new techniques in ancient DNA studies, the results show that customized forensic technologies can be successfully applied to aged bone remains, highlighting the role of the template in the success of PCR-MPS analysis. However, because several typical errors of ancient DNA sequencing were scored, replicate tests and accurate evaluation by an expert remain indispensable tools.

Isometric artifacts from polymerase chain reaction‐massively parallel sequencing analysis of short tandem repeat loci: An emerging issue from a new technology?

The recent introduction of polymerase chain reaction (PCR)‐massively parallel sequencing (MPS) technologies in forensics has changed the approach to allelic short tandem repeat (STR) typing because sequencing cloned PCR fragments enables alleles with identical molecular weights to be distinguished based on their nucleotide sequences. Therefore, because PCR fidelity mainly depends on template integrity, new technical issues could arise in the interpretation of the results obtained from the degraded samples. In this work, a set of DNA samples degraded in vitro was used to investigate whether PCR‐MPS could generate “isometric drop‐ins” (IDIs; i.e., molecular products having the same length as the original allele but with a different nucleotide sequence within the repeated units). The Precision ID GlobalFiler NGS STR panel kit was used to analyze 0.5 and 1 ng of mock samples in duplicate tests (for a total of 16 PCR‐MPS analyses). As expected, several well‐known PCR artifacts (such as allelic dropout, stutters above the threshold) were scored; 95 IDIs with an average occurrence of 5.9 IDIs per test (min: 1, max: 11) were scored as well. In total, IDIs represented one of the most frequent artifacts. The coverage of these IDIs reached up to 981 reads (median: 239 reads), and the ratios with the coverage of the original allele ranged from 0.069 to 7.285 (median: 0.221). In addition, approximately 5.2% of the IDIs showed coverage higher than that of the original allele. Molecular analysis of these artifacts showed that they were generated in 96.8% of cases through a single nucleotide change event, with the C > T transition being the most frequent (85.7%). Thus, in a forensic evaluation of evidence, IDIs may represent an actual issue, particularly when DNA mixtures need to be interpreted because they could mislead the operator regarding the number of contributors. Overall, the molecular features of the IDIs described in this work, as well as the performance of duplicate tests, may be useful tools for managing this new class of artifacts otherwise not detected by capillary electrophoresis technology.

The development of forensic DNA analysis: New debates on the issue of fundamental human rights

Before the advent of forensic DNA profiling, forensic techniques such as fingerprint examination and blood type comparison were used in the identification of suspects. DNA profiling has since become the gold standard of forensic science, and forensic DNA analysis techniques continue to evolve. Recent developments such as familial searching and phenotyping have raised ethical questions and concerns reflecting those expressed in the late 1980s when forensic DNA analysis was first introduced. At that time, attempts to use DNA evidence in criminal trials were met with challenges to its evidential value and admissibility. A common concern was whether the probative value of the evidence would outweigh its potentially prejudicial effect. This gave rise to a complex three-way debate, which revolved around first, the admissibility of the scientific principles in criminal courts; second, the scientific process involved in analysing DNA samples; and third, the impact that forensic DNA analysis may have on fundamental human rights. Ultimately, debates about the scientific process and the admissibility of such evidence in criminal trials overshadowed the debate about potential infringements of fundamental human rights. This resulted in a lack of critical discussion around the erosion of civil liberties through the use of scientific technologies. This paper revisits the early debates on the development of forensic DNA analysis. It draws parallels with current developments and analyses the potential for current and future human rights infringements, highlighting that the libertarian model offers a necessary counterbalance to the other arguments, due to its concern for maintaining fundamental rights.

DNA recovery after sequential processing of latent fingerprints on copy paper

Forensic examiners must determine whether both latent fingerprint development and DNA profiling can be performed on the same area of an evidence item and, if only one is possible, which examination offers the best chance for identification. Latent fingerprints can be enhanced by targeting different components of fingerprint residues with sequential chemical treatments. This study investigated the effects of single-reagent and sequential latent fingerprint development processes on downstream DNA analysis to determine the point at which latent fingerprint development should be stopped to allow for DNA recovery. Latent fingerprints deposited on copy paper by one donor were developed using three sequential processes: 1,8-diazafluoren-9-one (DFO) → ninhydrin → physical developer (PD); 1,2-indanedione-zinc (IND-Zn) → ninhydrin → PD; and IND-Zn → ninhydrin → Oil Red O (ORO) → PD. Samples were examined after the addition of each chemical treatment. DNA was collected with cotton swabs, extracted, quantified, and amplified. DNA yields, peak heights, number of alleles obtained, and percentage of DNA profiles eligible for CODIS upload were examined. DNA profiles were obtained with varying degrees of success, depending on the number and type of treatments used for latent fingerprint development. The treatments that were found to be the least harmful to downstream DNA analysis were IND-Zn and IND-Zn/laser, and the most detrimental treatments were DFO, DFO/laser, and PD. In general, as the number of treatments increase, the opportunities for DNA loss or damage also increase, and it is preferable to use fewer treatments when developing latent fingerprints prior to downstream DNA processing.

High-throughput DNA sequencing of environmentally insulted latent fingerprints after visualization with nanoscale columnar-thin-film technique

The goals of this study were to (a) ascertain human identity capabilities of DNA obtained from latent fingerprints that have been first environmentally insulted and then developed by the deposition of a columnar thin film (CTF), and (b) to determine if the CTF process and material are detrimental to single nucleotide polymorphism (SNP) analysis. Fingerprints were deposited on five different types of substrates and aged for one day, 7 days or 30 days while being environmentally insulted under one of the four conditions: 16.6 °C and 60% relative humidity (RH) (Condition A), 24.5 °C and 60% RH (Condition B), 35 °C and 67% RH (Condition C) and a cold condition (Condition D). Then CTF technique was then on 59% of these fingerprints. DNA samples from 805 fingerprints were extracted, quantified, subjected to manual library preparation using the Precision ID Identity Panel, and underwent high-throughput sequencing. The Ion S5™ platform was employed to sequence 124 SNP amplicons. SNPs were successfully sequenced from 802/805 samples. Total read depth was consistent across environmental conditions, and majority of samples had 100% profile completeness and 100% concordance. Anecdotally, libraries that were amplified with a higher cycle number had more 'Major Allele Frequency' flags compared to samples amplified with 23 cycle numbers, possibly due to stochastic effects. Neither the substrates nor the CTF process and materials inhibit downstream DNA analysis. DNA of low quality and quantity from the chosen samples can be sequenced using the Precision ID Identity Panel on the Ion S5™ platform which performed well, however, a different approach may be needed if spurious alleles are suspected.

Pushing the Boundaries: Forensic DNA Phenotyping Challenged by Single-Cell Sequencing

Single-cell sequencing is a fast developing and very promising field; however, it is not commonly used in forensics. The main motivation behind introducing this technology into forensics is to improve mixture deconvolution, especially when a trace consists of the same cell type. Successful studies demonstrate the ability to analyze a mixture by separating single cells and obtaining CE-based STR profiles. This indicates a potential use of the method in other forensic investigations, like forensic DNA phenotyping, in which using mixed traces is not fully recommended. For this study, we collected single-source autopsy blood from which the white cells were first stained and later separated with the DEPArray™ N×T System. Groups of 20, 10, and 5 cells, as well as 20 single cells, were collected and submitted for DNA extraction. Libraries were prepared using the Ion AmpliSeq™ PhenoTrivium Panel, which includes both phenotype (HIrisPlex-S: eye, hair, and skin color) and ancestry-associated SNP-markers. Prior to sequencing, half of the single-cell-based libraries were additionally amplified and purified in order to improve the library concentrations. Ancestry and phenotype analysis resulted in nearly full consensus profiles resulting in correct predictions not only for the cells groups but also for the ten re-amplified single-cell libraries. Our results suggest that sequencing of single cells can be a promising tool used to deconvolute mixed traces submitted for forensic DNA phenotyping.

Strategy for STR typing of bones from the Second World War combining CE and NGS technology: A pilot study

The genetic identification of skeletal remains found in Second World War mass graves is complicated because of the poor quality of the samples. The aim of this study was to set up a workflow for STR typing of such samples combining PCR/CE and PCR/NGS technologies. To this end, 57 DNA samples from an equal number of 75-year-old femurs were studied. After a first round of PCR typing using GlobalFiler CE, 42 samples yielded a full profile and were therefore submitted to our standard workflow. The 15 samples that yielded no or a limited number (2-17/21) of autosomal STR markers as well four bone control samples that provided a full profile with the conventional PCR/CE test were typed in duplicate by the GlobalFiler NGS kit. Despite the degradation of the samples, which resulted in lower coverage and a lower % of on-target reads, reliable sequencing data were obtained from 16/19 samples. The use of a threshold of 30× for the locus call led to a consensus profile (cp) of 20-31/31 STR autosomal loci in 10 samples and to a cp of 8-10/31 loci in two samples, whereas the four control samples yielded a cp of 26-31/31 loci. Finally, the data of the NGS typing were combined with those of the CE typing. This last task allowed us to recover (on average) three alleles per sample and to increase the number of the heterozygous patterns in 37 cases. In total, the combined approach proposed here made possible the genetic typing of 65-100% of the autosomal STR markers in 10/15 (66.6 %) skeletal remains that yielded no or very poor results with the conventional PCR/CE approach. However, because several artefacts (such as allelic drop-out and allelic drop-in) were scored, the risk of mistyping cannot be neglected.

Performance Comparison of Massively Parallel Sequencing (MPS) Instruments Using Single-Nucleotide Polymorphism (SNP) Panels for Ancestry

Thermo Fisher Scientific released the Precision ID Ancestry Panel, a 165-single-nucleotide polymorphism (SNP) panel for ancestry prediction that was initially compatible with the manufacturer's massively parallel sequencer, the Ion Torrent Personal Genome Machine (PGM). The semiautomated workflow using the panel with the PGM involved several time-consuming manual steps across three instruments, including making templating solutions and loading sequencing chips. In 2014, the manufacturer released the Ion Chef robot, followed by the Ion S5 massively parallel sequencer in late 2015. The robot performs the templating with reagent cartridges and loads the chips, thus creating a fully automated workflow across two instruments. The objective of the work reported here is to compare the performance of two massively parallel sequencing systems and ascertain if the change in the workflow produces different ancestry predictions. For performance comparison of the two systems, forensic-type samples (n = 16) were used to make libraries. Libraries were templated either with the Ion OneTouch 2 system (for the PGM) or on the Ion Chef robot (for the S5). Sequencing results indicated that the ion sphere particle performance metrics were similar for the two systems. The total coverages per SNP and SNP quality were both higher for the S5 system. Ancestry predictions were concordant for the mock forensic-type samples sequenced on both massively parallel sequencing systems. The results indicated that automating the workflow with the Ion Chef system reduced the labor involved and increased the sequencing quality.

Massively parallel sequencing and STR analysis from partial bloody fingerprints enhanced with columnar thin films

Fingerprint enhancement often includes either physical or chemical approaches, such as fingerprint powder or cyanoacrylate fuming, to improve the quality of a fingerprint for visualization and analysis. However, these methods become more complex when fingerprints are partial bloody, and these procedures may interfere with downstream DNA analysis. Columnar thin film (CTF) deposition is a type of nanotechnology that utilizes an evaporant material to enhance a fingerprint under low-pressure conditions. Short tandem repeat (STR) analysis is the traditional method employed in crime laboratories. When DNA is of poor quality and quantity, like that often obtained from fingerprints, little to no genetic information may be obtained. Single nucleotide polymorphisms (SNPs) may be used to glean additional information when STR analysis fails. In this pilot study, 100 partial bloody fingerprints were collected from two donors and deposited on five different crime scene substrates, in which half were enhanced with CTFs and were graded for quality by an IAI-certified latent fingerprint examiner. CTF-developed fingerprints, on average, had higher grades compared to non-developed partial bloody fingerprints. STR analysis using Fusion 6C was performed to assess inhibition from the evaporant materials, in which no inhibition was observed. Sequencing of SNPs using the Precision ID Identity Panel was also employed, in which genetic information that could not be obtained from STRs was acquired with SNPs. Various sample types (i.e. pristine, low quality, and contaminated) utilized in this project demonstrated the acceptable performance of the Precision ID Identity Panel.

The challenge of predicting human pigmentation traits in degraded bone samples with the MPS-based HIrisPlex-S system

Identification of human remains is an important part of human DNA analysis studies. STR and mitochondrial DNA markers are well suited for the analysis of degraded biological samples including bone material. However, these DNA markers may be useless when reference material is not available. In these cases, predictive DNA analysis can support the process of human identification by providing investigative leads. Forensic DNA phenotyping has progressed significantly by offering new methods based on massively parallel sequencing technology, but the frequent degradation processes observed in skeletal remains can make analysis of such samples challenging. In this study, we demonstrate the usefulness of a recently established Ion AmpliSeq^TM HIrisPlex-S panel using Ion Torrent technology for analyzing bone samples that show different levels of DNA degradation. In total, 63 bone samples at post-mortem intervals up to almost 80 years were genotyped and eye, hair and skin colour predictions were performed using the HIrisPlex-S models. Following the recommended coverage thresholds, it was possible to establish full DNA profiles comprising of 41 DNA variants for 35 samples (55.6%). For 5 samples (7.9%) no DNA profiles were generated. The remaining 23 samples (36.5%) produced partial profiles and showed a clear underperformance of 3 HIrisPlex-S SNPs - rs1545397 (OCA2), rs1470608 (OCA2) and rs10756819 (BNC2), all used for skin colour prediction only. None of the 23 samples gave complete genotypes needed for skin colour prediction was obtained, and in 7 of them (25.9%) the 3 underperformed SNPs were the cause. At the same time, the prediction of eye and hair colour using complete IrisPlex and HIrisPlex profiles could be made for these 23 samples in 20 (87.0%) and 12 cases (52.2%), respectively. Complete HIrisPlex-S profiles were generated from as little as 49 pg of template DNA. Five samples for which the HIrisPlex-S analysis failed, consistently failed in standard STR analysis. Importantly, the 3 underperforming SNPs produced significantly lower number of reads in good quality samples. Nonetheless, the AUC loss resulting from missing data for these 3 SNPs is not considered large (≤0.004) and the prediction of pigmentation from partial profiles is also available in the current HPS tool. The study shows that DNA degradation and the resulting loss of data are the most serious challenge to DNA phenotyping of skeletal remains. Although the newly developed HIrisPlex-S panel has been successfully validated in the current research, primer redesign for the 3 underperforming SNPs in the MPS design should be considered in the future.

Forensic characterization of Brazilian regional populations through massive parallel sequencing of 124 SNPs included in HID ion Ampliseq Identity Panel

Use of Massive Parallel Sequencing (MPS) techniques has been investigated by forensic community aiming introduction of such methods in routine forensic casework analyses. Interesting features presented by MPS include high-throughput, ability to simultaneous genotyping of significant number of samples and forensic markers, workflow automation, among others. Emergence of single nucleotide polymorphism (SNP) as forensic relevant markers was facilitated in this process, since concurrent typing of larger marker sets is necessary for obtaining same levels of individual discrimination provided by other marker categories. In this context, HID Ion Ampliseq Identity Panel is a commercial solution with forensic purposes comprising simultaneous analysis of 90 highly informative autosomal SNPs and 34 Y -chromosome superior clade SNPs for male lineage haplotyping. SNP typing can be obtained with smaller amplicons, and this panel was designed for efficient processing of critical or challenging forensic samples. In this work, a sample of 432 individuals from all five Brazilian geopolitical regions was evaluated with this panel, in order to access feasibility of this panel use in a national basis. Results obtained for all five regions, including forensic parameters, show that this marker set can be efficiently employed for Brazilian nationals in human identification or kinship determination applications, due to high levels of genetic discriminative information content displayed by Brazilians. Interpopulation comparison studies were executed among Brazilian regional populations and 26 worldwide populations, in order to access genetic stratification occurrence. Some levels of population structure were identified, and impact on database design was discussed. Y-chromosome haplotyping of Brazilian samples revealed high levels of European ancestry in Brazilian male lineages, and utility of haplotyping in real forensic casework is addressed. Finally, genotyping and sequencing efficiency with this panel were addressed, as an effort to appraise the adequacy of this panel use in Brazilian national forensic demands.

Massively parallel sequencing techniques for forensics: A review

DNA sequencing, starting with Sanger's chain termination method in 1977 and evolving into the next generation sequencing (NGS) techniques of today that employ massively parallel sequencing (MPS), has become essential in application areas such as biotechnology, virology, and medical diagnostics. Reflected by the growing number of articles published over the last 2-3 years, these techniques have also gained attention in the forensic field. This review contains a brief description of first, second, and third generation sequencing techniques, and focuses on the recent developments in human DNA analysis applicable in the forensic field. Relevance to the forensic analysis is that besides generation of standard STR-profiles, DNA repeats can also be sequenced to look for polymorphisms. Furthermore, additional SNPs can be sequenced to acquire information on ancestry, paternity or phenotype. The current MPS systems are also very helpful in cases where only a limited amount of DNA or highly degraded DNA has been secured from a crime scene. If enough autosomal DNA is not present, mitochondrial DNA can be sequenced for maternal lineage analysis. These developments clearly demonstrate that the use of NGS will grow into an indispensable tool for forensic science.

Identification of the skeletal remains of the Czech communist regime crime victim, priest Josef Toufar

Parish priest Josef Toufar died as a direct consequence of torture committed by Communist State Security Service agents, forcing him to confess that "miraculous" movement of crucifix above the main altar during the Holy Mass held in the Roman-Catholic church in Číhošť was staged by using a technical equipment. Josef Toufar was presumably buried in a mass grave at the cemetery in Prague-Ďáblice under a false name Josef Zouhar. In 2013 the Czech Bishops' Conference grant an approval to begin the process of his beatification. However, the beatification required the exhumation and identification of the remains. In this case report, we describe the process of searching, exhumation, and the combined A-STR/Y-STR DNA analysis of remains of Pater Josef Toufar. His identification was feasible due to kinship analysis: buccal swabs of three family members (niece, grand-niece, and grand-nephew) were available for testing.

Short hypervariable microhaplotypes: A novel set of very short high discriminating power loci without stutter artefacts

Since two decades, short tandem repeats (STRs) are the preferred markers for human identification, routinely analysed by fragment length analysis. Here we present a novel set of short hypervariable autosomal microhaplotypes (MH) that have four or more SNPs in a span of less than 70 nucleotides (nt). These MHs display a discriminating power approaching that of STRs and provide a powerful alternative for the analysis;1;is of forensic samples that are problematic when the STR fragment size range exceeds the integrity range of severely degraded DNA or when multiple donors contribute to an evidentiary stain and STR stutter artefacts complicate profile interpretation. MH typing was developed using the power of massively parallel sequencing (MPS) enabling new powerful, fast and efficient SNP-based approaches. MH candidates were obtained from queries in data of the 1000 Genomes, and Genome of the Netherlands (GoNL) projects. Wet-lab analysis of 276 globally dispersed samples and 97 samples of nine large CEPH families assisted locus selection and corroboration of informative value. We infer that MHs represent an alternative marker type with good discriminating power per locus (allowing the use of a limited number of loci), small amplicon sizes and absence of stutter artefacts that can be especially helpful when unbalanced mixed samples are submitted for human identification.

Producing standard damaged DNA samples by heating: pitfalls and suggestions

Heat-mediated hydrolysis of DNA is a simple and inexpensive method for producing damaged samples in vitro. Despite heat-mediated DNA hydrolysis is being widely used in forensic and clinical validation procedures, the lack of standardized procedures makes it impossible to compare the intra and inter-laboratory outcomes of the damaging treatments. In this work, a systematic approach to heat induced DNA hydrolysis was performed at 70 °C for 0-18 h to test the role both of the hydrolysis buffer and of the experimental conditions. Specifically, a trial DNA sample, resuspended in three different media (ultrapure water, 0.1% DEPC-water and, respectively, TE) was treated both in Eppendorf tubes ("Protocol P") and in Eppendorf tubes provided with screwcaps ("Protocol S"). The results of these comparative tests were assessed by normalization of the qPCR results. DEPC-water increased the degradation of the samples up to about 100 times when compared to the ultrapure water. Conversely, the TE protected the DNA from degradation whose level was about 1700 times lower than in samples treated in ultrapure water. Even the employment of the "Protocol S" affected the level of degradation, by consistently increasing it (up to about 180 times in DEPC-water). Thus, this comparative approach showed that even seemingly apparently trivial and often underestimated parameters modify the degradation level up to 2-3 orders of magnitude. The chemical-physical reasons of these findings are discussed together with the role of potential factors such as enhanced reactivity of CO₂, ROS, NO_x and pressure, which are likely to be involved. Since the intra and inter-laboratory comparison of the outcomes of the hydrolytic procedure is the first step toward its standardization, the normalization of the qPCR data by the UV/qPCR ratio seems to be the simplest and most reliable way to allow this. Finally, the supplying (provided with the commercial qPCR kits) of a DNA sample whose degree of degradation is well documented could be helpful in ISO/IEC 17025 validation procedures and in proficiency testing.

Qualitative and quantitative assessment of Illumina's forensic STR and SNP kits on MiSeq FGx™

Massively parallel sequencing (MPS) is a powerful tool transforming DNA analysis in multiple fields ranging from medicine, to environmental science, to evolutionary biology. In forensic applications, MPS offers the ability to significantly increase the discriminatory power of human identification as well as aid in mixture deconvolution. However, before the benefits of any new technology can be employed, a thorough evaluation of its quality, consistency, sensitivity, and specificity must be rigorously evaluated in order to gain a detailed understanding of the technique including sources of error, error rates, and other restrictions/limitations. This extensive study assessed the performance of Illumina’s MiSeq FGx MPS system and ForenSeq™ kit in nine experimental runs including 314 reaction samples. In-depth data analysis evaluated the consequences of different assay conditions on test results. Variables included: sample numbers per run, targets per run, DNA input per sample, and replications. Results are presented as heat maps revealing patterns for each locus. Data analysis focused on read numbers (allele coverage), drop-outs, drop-ins, and sequence analysis. The study revealed that loci with high read numbers performed better and resulted in fewer drop-outs and well balanced heterozygous alleles. Several loci were prone to drop-outs which led to falsely typed homozygotes and therefore to genotype errors. Sequence analysis of allele drop-in typically revealed a single nucleotide change (deletion, insertion, or substitution). Analyses of sequences, no template controls, and spurious alleles suggest no contamination during library preparation, pooling, and sequencing, but indicate that sequencing or PCR errors may have occurred due to DNA polymerase infidelities. Finally, we found utilizing Illumina’s FGx System at recommended conditions does not guarantee 100% outcomes for all samples tested, including the positive control, and required manual editing due to low read numbers and/or allele drop-in. These findings are important for progressing towards implementation of MPS in forensic DNA testing.

Comparison of Two Massively Parallel Sequencing Platforms using 83 Single Nucleotide Polymorphisms for Human Identification

The potential of Massively Parallel Sequencing (MPS) technology to vastly expand the capabilities of human identification led to the emergence of different MPS platforms that use forensically relevant genetic markers. Two of the MPS platforms that are currently available are the MiSeq^® FGx™ Forensic Genomics System (Illumina) and the HID-Ion Personal Genome Machine (PGM)™ (Thermo Fisher Scientific). These are coupled with the ForenSeq™ DNA Signature Prep kit (Illumina) and the HID-Ion AmpliSeq™ Identity Panel (Thermo Fisher Scientific), respectively. In this study, we compared the genotyping performance of the two MPS systems based on 83 SNP markers that are present in both MPS marker panels. Results show that MiSeq^® FGx™ has greater sample-to-sample variation than the HID-Ion PGM™ in terms of read counts for all the 83 SNP markers. Allele coverage ratio (ACR) values show generally balanced heterozygous reads for both platforms. Two and four SNP markers from the MiSeq^® FGx™ and HID-Ion PGM™, respectively, have average ACR values lower than the recommended value of 0.67. Comparison of genotype calls showed 99.7% concordance between the two platforms.

STRait Razor v2s: Advancing sequence-based STR allele reporting and beyond to other marker systems

STRait Razor has provided the forensic community a free-to-use, open-source tool for short tandem repeat (STR) analysis of massively parallel sequencing (MPS) data. STRait Razor v2s (SRv2s) allows users to capture physically phased haplotypes within the full amplicon of both commercial (ForenSeq) and "early access" panels (PowerSeq, Mixture ID). STRait Razor v2s may be run in batch mode to facilitate population-level analysis and is supported by all Unix distributions (including MAC OS). Data are reported in tables in string (haplotype), length-based (e.g., vWA allele 14), and International Society of Forensic Genetics (ISFG)-recommended (vWA [CE 14]-GRCh38-chr12:5983950-5984049 (TAGA)₁₀ (CAGA)₃ TAGA) formats. STRait Razor v2s currently contains a database of ∼2500 unique sequences. This database is used by SRv2s to match strings to the appropriate allele in ISFG-recommended format. In addition to STRs, SRv2s has configuration files necessary to capture and report haplotypes from all marker types included in these multiplexes (e.g., SNPs, InDels, and microhaplotypes). To facilitate mixture interpretation, data may be displayed from all markers in a format similar to that of electropherograms displayed by traditional forensic software. The download package for SRv2s may be found at https://www.unthsc.edu/graduate-school-of-biomedical-sciences/molecular-and-medical-genetics/laboratory-faculty-and-staff/strait-razor.