Application of next-generation sequencing technology in forensic science

Preliminary study on microeukaryotic community analysis using NGS technology to determine postmortem submersion interval (PMSI) in the drowned pig

while several methods for determining postmortem submersion interval (PMSI) in drowning cases have been suggested, the estimation of PMSI remains difficult. Next-generation sequencing (NGS) technology enables simultaneous identification of multiple taxa from environmental samples. Although NGS has been applied to estimate time since death, this application has been mainly focused on terrestrial cases. As a case study, we investigated microeukaryotic biodiversity and community structures in submerged car bonnet and drowned pig using NGS technology. NGS analysis showed that the microeukaryotic biodiversity in pig carcass was relevantly lower than that in car bonnet. NGS results also revealed that water molds and algae were related to decomposition. Relative abundances of Filobasidium, Achlya, Saprolegnia, Hydrodicton, Lobosphaera, and Scenedesmus varied with decomposition period. This data indicated that these taxa might be useful as good indicators to estimate PMSI. This study showed microeukaryotic community analysis using NGS technology may help solve drowning cases in forensic investigation.

ACOG Technology Assessment in Obstetrics and Gynecology No. 14: Modern Genetics in Obstetrics and Gynecology

Knowledge of human genetics has increased dramatically, and obstetrician-gynecologists and other health care providers are increasingly called on to incorporate genetics and genetic testing into medical practice. Advances in our understanding of the molecular basis of inherited disorders have led to the development of DNA-based tests that can be used for prenatal and postnatal diagnosis, carrier testing, and aneuploidy screening. These techniques have allowed for diagnosis of a wide variety of genetic diseases ranging from aneuploidies to single-gene disorders. Once a specific pathogenic variant in a gene has been identified, direct testing for that specific variant is possible; this is the most accurate molecular diagnostic method. Counseling patients about genetic testing and results can be challenging and obstetrician-gynecologists and women's health care providers are encouraged to make use of and refer to genetics professionals when necessary. The correct interpretation of molecular genetic diagnostic testing is highly dependent on an accurate clinical diagnosis, test sensitivity, ethnic variability in variants and disease prevalence, genetic heterogeneity, reduced penetrance, and phenotypical variability. As genetics becomes a more integral part of routine medical practice, it is essential that obstetrician-gynecologists and other health care providers be aware of advances in the understanding of genetic disease and the fundamental principles of genetic screening and molecular testing. This technology assessment has been revised to reflect advances in clinical genetics related to obstetrics and gynecology, including epigenetics, sequencing, and testing.

Optimizing DNA recovery and forensic typing of degraded blood and dental remains using a specialized extraction method, comprehensive qPCR sample characterization, and massively parallel sequencing

Human dental remains encountered in criminal casework evidence, missing person cases, or mass disaster tragedies provide a valuable sample source for DNA typing when suitable soft tissue is unavailable. Using traditional methods, teeth samples can be challenging to process, resulting in low-quantity and/or quality nuclear DNA and insufficient profiles for comparisons. This study examines the performance of a three-part nuclear DNA analysis workflow for teeth samples based on (1) improved dental tissue recovery using the Dental Forensic Kit (DFK^MR) (Universidad de los Andes) and DNA extraction with QuickExtract™ FFPE DNA Extraction Kit (Lucigen®), (2) quantification with InnoQuant® HY (InnoGenomics Technologies) for sensitive assessment of total human and male DNA quantity/quality, and (3) massively parallel sequencing for simultaneous genotyping of 231 short tandem repeat (STR) and single-nucleotide polymorphism (SNP) markers with the ForenSeq® DNA Signature Prep Kit (Verogen, Inc.). Initial evaluation of artificially degraded blood samples (n = 10) achieved highly sensitive and informative quantification results with InnoQuant® HY, enabling successful first pass genotyping with the MiSeq FGx® System. Twenty-three STR alleles (out of 85) and 70 identity informative SNP loci (out of 94) were recovered from two pg total long target DNA input (0.86 ng total short target input) and an InnoQuant degradation index (DI) of 460 (severely degraded). The three-part workflow was subsequently applied to teeth samples (dental pulp, root cement tissues; n = 13) with postmortem intervals (PMI) of the teeth ranging from 8 days to approximately 6 months. Informative SNP and STR DNA profiles were obtained, to include 78 STR alleles and 85 identity informative SNP loci typed (of 94 total SNP targets) in a 1 month, four-day PMI root cement sample with one pg total long target DNA input and a DI of 76. These data indicate successful performance of the proposed workflow from degraded DNA from teeth samples.

Impact of DNA degradation on massively parallel sequencing-based autosomal STR, iiSNP, and mitochondrial DNA typing systems

Biological samples, including skeletal remains exposed to environmental insults for extended periods of time, exhibit increasing levels of DNA damage and fragmentation. Human forensic identification methods typically use a combination of mitochondrial (mt) DNA sequencing and short tandem repeat (STR) analysis, which target segments of DNA ranging from 80 to 500 base pairs (bps). Larger templates are often unavailable as skeletal samples age and the associated DNA degrades. Single-nucleotide polymorphism (SNP) loci target shorter templates and may serve as a solution to the problem. Recently developed assays for STR and SNP analysis using a massively parallel sequencing approach, such as the ForenSeq kit (Verogen, San Diego, CA), offer a means for generating results from degraded samples as they target templates down to 60 to 170 bps. We performed a modeling study that demonstrates that SNPs can increase the significance of an identification when analyzing DNA down to an average size of 100 bps for input amounts between 0.375 and 1 ng of nuclear DNA. Observations from this study were then compared with human skeletal material results (n = 14, ninth to eighteenth centuries), which further demonstrated the utility of the ForenSeq kit for degraded samples. The robustness of the Promega PowerSeq™ Mito System was also tested with human skeletal remains (n = 70, ninth to eighteenth centuries), resulting in successful coverage of 99.29% of the mtDNA control region at 50× coverage or more. This was accompanied by modifications to a mainstream DNA extraction technique for skeletal remains that improved recovery of shorter templates.

Forensic Genetics and Genotyping

Forensic genetics represents a combination of molecular and population genetics. Personal identification and kinship analysis (e.g. paternity testing) are the two main subjects of forensic DNA analysis. Biological specimens from which DNA is isolated are blood, semen, saliva, tissues, bones, teeth, hairs. Genotyping has become a basis in the characterization of forensic biological evidence. It is performed using a variety of genetic markers, which are divided into two large groups: bi-allelic (single-nucleotide polymorphisms, SNP) and multi-allelic polymorphisms (variable number of tandem repeats, VNTR and short tandem repeats, STR). This review describes the purpose of genetic markers in forensic investigation and their limitations. The STR loci are currently the most informative genetic markers for identity testing, but in cases without a suspect SNP can predict offender’s ancestry and phenotype traits such as skin, eyes and hair color. Nowadays, many countries worldwide have established forensic DNA databases based on autosomal short tandem repeats and other markers. In order for DNA profile database to be useful at a national or international level, it is essential to standardize genetic markers used in laboratories.

Privacy and ethical challenges in next-generation sequencing

INTRODUCTION

Next-generation sequencing (NGS) is expected to revolutionize health care. NGS allows for sequencing of the whole genome more cheaply and quickly than previous techniques. NGS offers opportunities to advance medical diagnostics and treatments, but also raises complicated ethical questions that need to be addressed.

AREAS CONSIDERED

This article draws from the literature on research and clinical ethics, as well as next-generation sequencing, in order to provide an overview of the ethical challenges involved in next-generation sequencing. This article includes a discussion of the ethics of NGS in research and clinical contexts.

EXPERT OPINION

The use of NGS in clinical and research contexts has features that pose challenges for traditional ethical frameworks for protecting research participants and patients. NGS generates massive amounts of data and results that vary in terms of known clinical relevance. It is important to determine appropriate processes for protecting, managing and communicating the data. The use of machine learning for sequencing and interpretation of genomic data also raises concerns in terms of the potential for bias and potential implications for fiduciary obligations. NGS poses particular challenges in three main ethical areas: privacy, informed consent, and return of results.

Food Tracking Perspective: DNA Metabarcoding to Identify Plant Composition in Complex and Processed Food Products

One of the main goals of the quality control evaluation is to identify contaminants in raw material, or contamination after a food is processed and before it is placed on the market. During the treatment processes, contamination, both accidental and economically motivated, can generate incongruence between declared and real composition. In our study, we evaluated if DNA metabarcoding is a suitable tool for unveiling the composition of processed food, when it contains small trace amounts. We tested this method on different types of commercial plant products by using tnrL marker and we applied amplicon-based high-throughput sequencing techniques to identify plant components in different food products. Our results showed that DNA metabarcoding can be an effective approach for food traceability in different type of processed food. Indeed, the vast majority of our samples, we identified the species composition as the labels reported. Although some critical issues still exist, mostly deriving from the starting composition (i.e., variable complexity in taxa composition) of the sample itself and the different processing level (i.e., high or low DNA degradation), our data confirmed the potential of the DNA metabarcoding approach also in quantitative analyses for food composition quality control.

Nanopore sequencing: An enrichment-free alternative to mitochondrial DNA sequencing

Mitochondrial DNA sequence data are often utilized in disease studies, conservation genetics and forensic identification. The current approaches for sequencing the full mtGenome typically require several rounds of PCR enrichment during Sanger or MPS protocols followed by fairly tedious assembly and analysis. Here we describe an efficient approach to sequencing directly from genomic DNA samples without prior enrichment or extensive library preparation steps. A comparison is made between libraries sequenced directly from native DNA and the same samples sequenced from libraries generated with nine overlapping mtDNA amplicons on the Oxford Nanopore MinION™ device. The native and amplicon library preparation methods and alternative base calling strategies were assessed to establish error rates and identify trends of discordance between the two library preparation approaches. For the complete mtGenome, 16 569 nucleotides, an overall error rate of approximately 1.00% was observed. As expected with mtDNA, the majority of error was detected in homopolymeric regions. The use of a modified basecaller that corrects for ambiguous signal in homopolymeric stretches reduced the error rate for both library preparation methods to approximately 0.30%. Our study indicates that direct mtDNA sequencing from native DNA on the MinION™ device provides comparable results to those obtained from common mtDNA sequencing methods and is a reliable alternative to approaches using PCR-enriched libraries.

Evaluating the Efficiency of Primer Extension Capture as a Method to Enrich DNA Extractions

In this study, we sought to document the efficiency of primer extension capture (PEC) as a method to enrich DNA eluates of targeted DNA molecules and remove nontarget molecules from pools containing both. Efficiency of the method was estimated by comparing number of "copies in" to "copies out" by quantitative polymerase chain reaction. PEC retention of DNA targets ranging 109-288 base pairs (bps) in length was 15.88-2.14% (i.e., loss of 84.12-97.86% of target molecules). Experimental modifications of the PEC method resulted in no significant improvements. However, the benefit of PEC was revealed in its ability to remove most nontarget DNA molecules (99.99%). We also discovered that many (56.69%) of the target molecules are "lost" prior to their immobilization on the streptavidin-coated beads. These estimates of methodological efficiency are directly comparable to previous ones observed following "fishing" for DNA, an alternative method for DNA enrichment.

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.

Next-Generation Sequencing for Biodefense: Biothreat Detection, Forensics, and the Clinic

BACKGROUND

Next-generation sequencing (NGS) is revolutionizing a variety of molecular biology fields including bioforensics, biosurveillance, and infectious disease diagnostics. For pathogen detection, the ability to sequence all nucleic acids in a sample allows near limitless multiplexability, free from a priori knowledge regarding an etiologic agent as is typically required for targeted molecular assays such as real-time PCR. Furthermore, sequencing capabilities can generate in depth genomic information, allowing detailed molecular epidemiological studies and bioforensics analysis, which is critical for source agent identification in a biothreat outbreak. However, lack of analytical specificity, inherent to NGS, presents challenges for regulated applications such as clinical diagnostics and molecular attribution.

CONTENT

Here, we discuss NGS applications in the context of preparedness and biothreat readiness. Specifically, we investigate current and future applications of NGS technologies to affect the fields of biosurveillance, bioforensics, and clinical diagnostics with specific focus on biodefense.

SUMMARY

Overall, there are many advantages to the implementation of NGS for preparedness and readiness against biowarfare agents, from forensics to diagnostics. However, appropriate caveats must be associated with any technology. This includes NGS. While NGS is not the panacea replacing all molecular techniques, it will greatly enhance the ability to detect, characterize, and diagnose biowarfare agents, thus providing an excellent addition to the biodefense toolbox of biosurveillance, bioforensics, and biothreat diagnosis.

Assessment of impact of DNA extraction methods on analysis of human remain samples on massively parallel sequencing success

Skeletal remains recovered from missing persons' cases are often exposed to harsh environmental conditions resulting in the DNA being damaged, degraded, and/or the samples containing PCR inhibitors. In this study, the efficacy of common extraction methods was evaluated to remove high levels of PCR inhibitors commonly encountered with human remains, and their downstream compatibility with the two leading sequencing chemistries and platforms for human identification purposes. Blood, hair, and bone samples were spiked with high levels of inhibitors commonly identified in each particular substrate in order to test the efficiency of various DNA extraction methods prior to sequencing. Samples were extracted using three commercial extraction kits (DNA IQ™, DNA Investigator, and PrepFiler® BTA), organic (blood and hair only), and two total demineralization protocols (bone only)). Massively parallel sequencing (MPS) was performed using two different systems: Precision ID chemistry and a custom AmpliSeq™ STR and iiSNP panel on the Ion S5™ System and the ForenSeq DNA Signature Prep Kit on the MiSeq FGx™. The overall results showed that all DNA extraction methods were efficient and are fully compatible with both MPS systems. Key performance indicators such as STR and SNP reportable alleles, read depth, and heterozygote balance were comparable for each extraction method. In samples where CE-based STRs yielded partial profiles (bone), MPS-based STRs generated more complete or full profiles. Moreover, MPS panels contain more STR loci than current CE-based STR kits and also include SNPs, which can further increase the power of discrimination obtained from these samples, making MPS a desirable choice for the forensic analysis of such challenging samples.

Microbial forensics: new breakthroughs and future prospects

Recent advances in genetic data generation, through massive parallel sequencing (MPS), storage and analysis have fostered significant progresses in microbial forensics (or forensic microbiology). Initial applications in circumstances of biocrime, bioterrorism and epidemiology are now accompanied by the prospect of using microorganisms (i) as ancillary evidence in criminal cases; (ii) to clarify causes of death (e.g., drownings, toxicology, hospital-acquired infections, sudden infant death and shaken baby syndromes); (iii) to assist human identification (skin, hair and body fluid microbiomes); (iv) for geolocation (soil microbiome); and (v) to estimate postmortem interval (thanatomicrobiome and epinecrotic microbial community). When compared with classical microbiological methods, MPS offers a diverse range of advantages and alternative possibilities. However, prior to its implementation in the forensic context, critical efforts concerning the elaboration of standards and guidelines consolidated by the creation of robust and comprehensive reference databases must be undertaken.

Molecular markers used in forensic genetics

Forensic genetics is a field that has become subject to increasing interest in recent years. Both the technology and the markers used for forensic purposes have changed since the 1980s. The minisatellite sequences used in the famous Pitchfork case introduced genetics to the forensic sciences. Minisatellite sequences have now been replaced by more sensitive microsatellite markers, which have become the basis for the creation of genetic profile databases. Modern molecular methods also exploit single nucleotide polymorphisms, which are often the only way to identify degraded DNA samples. The same type of variation is taken into consideration in attempting to establish the ethnicity of a perpetrator and to determine phenotypic traits such as the eye or hair colour of the individual who is the source of the genetic material. This paper contains a review of the techniques and molecular markers used in human and animal forensic genetics, and also presents the potential trends in forensic genetics such as phenotyping.

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.

Big data in forensic genetics

The potential and difficulties of the application of genome wide data in forensics are analyzed. We argue that, besides statistical, computational, ethical, economic and technical validation problems, the state of the art of population genetics theory is insufficient to deal with the forensic use of this type of data. In order to keep the current standards of quantifying and reporting genetic evidence, namely in kinship analyses and identification, substantial improvement in the theoretical framework should be reached, since to obtain genome-wide results is to provide the experts with data that they cannot quantify the corresponding evidentiary value. Therefore, while a satisfactory, generalized theoretical and biostatistical modelling is not achieved, it may well be wiser to improve the already established approaches to a limited, pre-defined number of validated genetic markers, amenable to a consensual handling and reporting. Whole genome population analyses will prove extremely useful in selecting the best suited and most efficient of those markers.

Massively Parallel Sequencing of Forensic STRs Using the Ion Chef™ and the Ion S5™ XL Systems

Next-generation sequencing (NGS) has been used to genotype forensic short tandem repeat (STR) markers for individual identification and kinship analysis. STR data from several NGS platforms have been published, but forensic application trials using the Ion S5™ XL system have not been reported. In this work, we report sensitivity, reproducibility, mixture, simulated degradation, and casework sample data on the Ion Chef™ and S5™ XL systems using an early access 25-plex panel. Sensitivity experiments showed that over 97% of the alleles were detectable with down to 62 pg input of genomic DNA. In mixture studies, alleles from minor contributors were correctly assigned at 1:9 and 9:1 ratios. NGS successfully gave 12 full genotype results from 13 challenging casework samples, compared with five full results using the CE platform. In conclusion, the Ion Chef™ and the Ion S5™ XL systems provided an alternative and promising approach for forensic STR genotyping.

Performance of the Early Access AmpliSeq™ Mitochondrial Panel with degraded DNA samples using the Ion Torrent™ platform

The Early Access AmpliSeq™ Mitochondrial Panel amplifies whole mitochondrial genomes for phylogenetic and kinship identifications, using Ion Torrent™ technology. There is currently limited information on its performance with degraded DNA, a common occurrence in forensic samples. This study evaluated the performance of the Panel with DNA samples degraded in vitro, to mimic conditions commonly found in forensic investigations. Purified DNA from five individuals was heat-treated at five time points each (125°C for 0, 30, 60, 120, and 240 min; total n = 25). The quality of DNA was assessed via a real-time DNA assay of genomic DNA and prepared for massively parallel sequencing on the Ion Torrent™ platform. Mitochondrial sequences were obtained for all samples and had an amplicon coverage averaging between 66X to 2803X. Most amplicons (157/162) displayed high coverages (452 ± 333X), while reads with less than 100X coverage were recorded in five amplicons only (90 ± 5X). Amplicon coverage was decreased with prolonged heating. At 72% strand balance, reads were well balanced between forward and reverse strands. Using a coverage threshold of ten reads per SNP, complete sequences were recovered in all samples and resolved kinship and, haplogroup relations. Additionally, the HV1 and HV2 regions of the reference and 240-min heat-treated samples (n = 10) were Sanger-sequenced for concordance. Overall, this study demonstrates the efficacy of a novel forensic Panel that recovers high quality mitochondrial sequences from degraded DNA samples.

Analysis of mainland Japanese and Okinawan Japanese populations using the precision ID Ancestry Panel

We typed 165 AIMs in 49 mainland Japanese and 47 Okinawa Japanese using the Precision ID Ancestry Panel (Thermo Fisher Scientific). None of the 165 SNPs showed significant deviation from Hardy-Weinberg equilibrium in the mainland Japanese. One SNP (rs3943253) showed significant deviation from Hardy-Weinberg equilibrium in Okinawa Japanese. Fisher's exact tests showed that the genotype frequencies of 14 loci were significantly different (p<0.05) between the two populations before correction for multiple testing. After Bonferroni correction, only rs671 remained statistically significant (p<0.0003). This SNP is located in the ALDH2 gene. The mutant A allele is associated with increased side effects after alcohol intake. The frequency of the GG genotype (wild type) was higher in the Okinawa Japanese (78.7%) than in mainland Japanese (34.7%; Bonferroni corrected P<0.001). For 31 (63.3%) of the mainland Japanese and 42 (89.4%) of Okinawa Japanese, the highest population likelihood was obtained with the Japanese reference population. However, only in a few individuals, the likelihoods were significantly different from those calculated using reference data from neighboring populations. The likelihoods for mainland Japanese and Okinawa Japanese were not significantly different from each other for any of the investigated individuals. STRUCTURE and PCA analyses showed that mainland Japanese, Okinawa Japanese, and East Asians could not be differentiated with the Precision ID Ancestry Panel.

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.

Using long ssDNA polynucleotides to amplify STRs loci in degraded DNA samples

Obtaining informative short tandem repeat (STR) profiles from degraded DNA samples is a challenging task usually undermined by locus or allele dropouts and peak-high imbalances observed in capillary electrophoresis (CE) electropherograms, especially for those markers with large amplicon sizes. We hereby show that the current STR assays may be greatly improved for the detection of genetic markers in degraded DNA samples by using long single stranded DNA polynucleotides (ssDNA polynucleotides) as surrogates for PCR primers. These long primers allow a closer annealing to the repeat sequences, thereby reducing the length of the template required for the amplification in fragmented DNA samples, while at the same time rendering amplicons of larger sizes suitable for multiplex assays. We also demonstrate that the annealing of long ssDNA polynucleotides does not need to be fully complementary in the 5’ region of the primers, thus allowing for the design of practically any long primer sequence for developing new multiplex assays. Furthermore, genotyping of intact DNA samples could also benefit from utilizing long primers since their close annealing to the target STR sequences may overcome wrong profiling generated by insertions/deletions present between the STR region and the annealing site of the primers. Additionally, long ssDNA polynucleotides might be utilized in multiplex PCR assays for other types of degraded or fragmented DNA, e.g. circulating, cell-free DNA (ccfDNA).

Next generation sequencing: an application in forensic sciences?

CONTEXT

Over the last few decades, advances in sequencing have improved greatly. One of the most important achievements of Next Generation Sequencing (NGS) is to produce millions of sequence reads in a short period of time, and to produce large sequences of DNA in fragments of any size. Libraries can be generated from whole genomes or any DNA or RNA region of interest without the need to know its sequence beforehand. This allows for looking for variations and facilitating genetic identification.

OBJECTIVES

A deep analysis of current NGS technologies and their application, especially in forensics, including a discussion about the pros and cons of these technologies in genetic identification.

METHODS

A systematic literature search in PubMed, Science Direct and Scopus electronic databases was performed for the period of December 2012 to June 2015.

RESULTS

In the forensic field, one of the main problems is the limited amount of sample available, as well as its degraded state. If the amount of DNA input required for preparing NGS libraries continues to decrease, nearly any sample could be sequenced; therefore, the maximum information from any biological remains could be obtained. Additionally, microbiome typification could be an interesting application to study for crime scene characterisation.

CONCLUSIONS

NGS technologies are going to be crucial for DNA human typing in cases like mass disasters or other events where forensic specimens and samples are compromised and degraded. With the use of NGS it will be possible to achieve the simultaneous analysis of the standard autosomal DNA (STRs and SNPs), mitochondrial DNA, and X and Y chromosomal markers.

Forensic genetics and genomics: Much more than just a human affair

While traditional forensic genetics has been oriented towards using human DNA in criminal investigation and civil court cases, it currently presents a much wider application range, including not only legal situations sensu stricto but also and, increasingly often, to preemptively avoid judicial processes. Despite some difficulties, current forensic genetics is progressively incorporating the analysis of nonhuman genetic material to a greater extent. The analysis of this material-including other animal species, plants, or microorganisms-is now broadly used, providing ancillary evidence in criminalistics in cases such as animal attacks, trafficking of species, bioterrorism and biocrimes, and identification of fraudulent food composition, among many others. Here, we explore how nonhuman forensic genetics is being revolutionized by the increasing variety of genetic markers, the establishment of faster, less error-burdened and cheaper sequencing technologies, and the emergence and improvement of models, methods, and bioinformatics facilities.

Search for More Effective Microsatellite Markers for Forensics With Next-Generation Sequencing

Published by the Combined DNA Index System (CODIS) program of the Federal Bureau of Investigation (FBI) in 1997, the 13 core short tandem repeat (STR) loci are widely adopted as genetic markers in forensic applications, e.g., identity testing and paternity testing. However, these loci may be biased and suffer from reduced sensitivities toward specific population groups. In addition, the rapid growth of entries in forensic databases raises the chance of random hits, which can cause false recognitions of criminal suspects. A solution to these problems is to introduce more effective STR markers. The availability of whole genome sequencing enables us to identify more reliable STRmarkers for forensic applicationscomputationally. In this paper, we proposed an algorithm to identify STR markers with high discriminative abilities from the next-generation sequencing data. Our algorithm could select a customized set of loci for a given population with pre-specified discriminative thresholds. We have applied the method to 320 Chinese individuals from the 1000 Genomes Project and obtained various numbers of loci, which were able to statistically identify an individualworldwide and had higher combined powers of discrimination and combined probabilities of exclusion than the existing CODIS 13 loci. For identity testing, themean frequencyofDNAprofile (FDP) with the selected 11 STRs was smaller than that with CODIS 13 STRs by student's t-test. With more loci, much smaller FDPs were obtained. The databasematching probabilities for selected loci were also lower than that for CODIS 13 STRs in a database with 10 billion entries. Moreover, the selected loci were able to provide considerably low chance of random profile matches so that statistically no false positives could occur. The selected loci also reduced the risk of random allele matches when doing the familial search, with lower random allele matching probabilities. In addition, the selected STRs were statistically better than CODIS STRs for paternity testing in our simulated data, with lower probabilities of false inclusions and exclusions.

Review: DNA Barcoding and Chromatography Fingerprints for the Authentication of Botanicals in Herbal Medicinal Products

In the last two decades, there has been a tremendous increase in the global use of herbal medicinal products (HMPs) due to their claimed health benefits. This has led to increase in their demand and consequently, also, resulted in massive adulteration. This is due to the fact that most of the traditional methods cannot identify closely related species in a process product form. Therefore the urgent need for simple and rapid identification methods resulted in the discovery of a novel technique. DNA barcoding is a process that uses short DNA sequence from the standard genome for species identification. This technique is reliable and is not affected by external factors such as climates, age, or plant part. The difficulties in isolation of DNA of high quality in addition to other factors are among the challenges encountered using the DNA barcoding in the authentication of HMP. These limitations indicated that using DNA barcoding alone may ineffectively authenticate the HMP. Therefore, the combination of DNA barcoding with chromatographic fingerprint, a popular and generally accepted technique for the assessment and quality control of HMP, will offer an efficient solution to effectively evaluate the authenticity and quality consistency of HMP. Detailed and quality information about the main composition of the HMPs will help to ascertain their efficacy and safety as these are very important for quality control.

Informativeness of NGS Analysis for Vaginal Fluid Identification

The identification of vaginal fluids in forensic examinations plays an important role in crime scene reconstruction. Molecular detection of vaginal bacterial communities can lead to the correct discrimination of body fluids. These kinds of studies can be performed through multiplex real-time PCR using primers for a specific selection of bacteria. The availability of next-generation sequencing (NGS) protocols provided for the extension of the analysis to evaluate the prokaryotes present in specimens. In this study, DNA was extracted from 18 samples (vaginal, oral, fecal, yoghurt) and analyzed by real-time PCR and NGS. The comparison between the two approaches has demonstrated that the information developed through NGS can augment the more conventional real-time PCR detection of a few key bacterial species to provide a more probative result and the correct identification of vaginal fluid from samples that are more forensically challenged.

Metagenomics and Bioinformatics in Microbial Ecology: Current Status and Beyond

Metagenomic approaches are now commonly used in microbial ecology to study microbial communities in more detail, including many strains that cannot be cultivated in the laboratory. Bioinformatic analyses make it possible to mine huge metagenomic datasets and discover general patterns that govern microbial ecosystems. However, the findings of typical metagenomic and bioinformatic analyses still do not completely describe the ecology and evolution of microbes in their environments. Most analyses still depend on straightforward sequence similarity searches against reference databases. We herein review the current state of metagenomics and bioinformatics in microbial ecology and discuss future directions for the field. New techniques will allow us to go beyond routine analyses and broaden our knowledge of microbial ecosystems. We need to enrich reference databases, promote platforms that enable meta- or comprehensive analyses of diverse metagenomic datasets, devise methods that utilize long-read sequence information, and develop more powerful bioinformatic methods to analyze data from diverse perspectives.

Recent Advances in Autism Spectrum Disorders: Applications of Whole Exome Sequencing Technology

Autism spectrum disorders (ASD) is characterized by three core symptoms with impaired reciprocal social interaction and communication, a pattern of repetitive behavior and/or restricted interests in early childhood. The prevalence is higher in male children than in female children. As a complex neurodevelopmental disorder, the phenotype and severity of autism are extremely heterogeneous with differences from one patient to another. Genetics has a key role in the etiology of autism. Environmental factors are also interacting with the genetic profile and cause abnormal changes in neuronal development, brain growth, and functional connectivity. The term of exome represents less than 1% of the human genome, but contains 85% of known disease-causing variants. Whole-exome sequencing (WES) is an application of the next generation sequencing technology to determine the variations of all coding regions, or exons of known genes. For this reason, WES has been extensively used for clinical studies in the recent years. WES has achieved great success in the past years for identifying Mendelian disease genes. This review evaluates the potential of current findings in ASD for application in next generation sequencing technology, particularly WES. WES and whole-genome sequencing (WGS) approaches may lead to the discovery of underlying genetic factors for ASD and may thereby identify novel therapeutic targets for this disorder.

Empirical estimation of sequencing error rates using smoothing splines

Background

Next-generation sequencing has been used by investigators to address a diverse range of biological problems through, for example, polymorphism and mutation discovery and microRNA profiling. However, compared to conventional sequencing, the error rates for next-generation sequencing are often higher, which impacts the downstream genomic analysis. Recently, Wang et al. (BMC Bioinformatics 13:185, 2012) proposed a shadow regression approach to estimate the error rates for next-generation sequencing data based on the assumption of a linear relationship between the number of reads sequenced and the number of reads containing errors (denoted as shadows). However, this linear read-shadow relationship may not be appropriate for all types of sequence data. Therefore, it is necessary to estimate the error rates in a more reliable way without assuming linearity. We proposed an empirical error rate estimation approach that employs cubic and robust smoothing splines to model the relationship between the number of reads sequenced and the number of shadows.

Results

We performed simulation studies using a frequency-based approach to generate the read and shadow counts directly, which can mimic the real sequence counts data structure. Using simulation, we investigated the performance of the proposed approach and compared it to that of shadow linear regression. The proposed approach provided more accurate error rate estimations than the shadow linear regression approach for all the scenarios tested. We also applied the proposed approach to assess the error rates for the sequence data from the MicroArray Quality Control project, a mutation screening study, the Encyclopedia of DNA Elements project, and bacteriophage PhiX DNA samples.

Conclusions

The proposed empirical error rate estimation approach does not assume a linear relationship between the error-free read and shadow counts and provides more accurate estimations of error rates for next-generation, short-read sequencing data.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-016-1052-3) contains supplementary material, which is available to authorized users.