Rapid PCR of STR markers: Applications to human identification

Taking the microfluidic approach to nucleic acid analysis in forensics: Review and perspectives

Forensic laboratories are universally acknowledged as being overburdened, underfunded, and in need of improved analytical methods to expedite investigations, decrease the costs associated with nucleic acid (NA) analysis, and perform human identification (HID) at the point of need (e.g., crime scene, booking station, etc.). In response, numerous research and development (R&D) efforts have resulted in microfluidic tools that automate portions of the forensic genetic workflow, including DNA extraction, amplification, and short tandem repeat (STR) typing. By the early 2000 s, reports from the National Institute of Justice (NIJ) anticipated that microfluidic 'swab-in-profile-out' systems would be available for use at the crime scene by 2015 and the FBI's 2010 'Rapid DNA' Initiative, approved by Congress in 2017, directed this effort by guiding the development and implementation of maturing systems. At present, few fully-automated microfluidic DNA technologies are commercially available for forensic HID and their adoption by agencies interested in identification has been limited. In practice, the integration of complex laboratory processes to produce one autonomous unit, along with the highly variable nature of forensic input samples, resulted in systems that are more expensive per sample and not comparable to gold-standard identification methods in terms of sensitivity, reproducibility, and multiplex capability. This Review and Perspective provides insight into the contributing factors to this outcome; namely, we focus on the complications associated with the tremendous undertaking that is developing a sample-in-answer-out platform for HID. For context, we also describe the intricate forensic landscape that contributes to a nuanced marketplace, not easily distilled down to cases of simple supply and demand. Moving forward and considering the trade-offs associated with developing methods to compete, sometimes directly, with conventional ones, we recommend a focus shift for microfluidics developers toward the creation of innovative solutions for emerging applications in the field to increase the bandwidth of the forensic investigative toolkit. Likewise, we urge case working personnel to reframe how they conceptualize the currently available Rapid DNA tools; rather than comparing these microfluidic methods to gold-standard procedures, take advantage of their rapid and integrated modes for those situations requiring expedited identifications in an informed manner.

Genetic polymorphisms and population genetic analyses of 57 autosomal InDel loci in Hubei Tujia group

Introduction: The Tujia is the eighth most populous population in China, but its genetic structure has not been fully studied. Methods: In this study, we utilized 57 autosomal Insertion/deletion (InDel) loci to evaluate the genetic polymorphisms and efficiency of forensic applications in the Chinese Hubei Tujia group, and analyzed the genetic structure variances among the studied group and other 26 different reference populations from five continents in 1000 Genomes Project (1KG). Results: The results showed that 57 InDels have no significant deviations from Hardy-Weinberg equilibrium and linkage equilibrium. The combined power of discrimination (CPD) and the combined probability of exclusion (CPE) values for 57 InDels were 0.99999999999999999999999699822 and 0.999975177214539 in the Hubei Tujia group, respectively. In addition, the results of genetic structure analyses indicated that the Hubei Tujia group has close genetic relationships with the Chinese Han population and other East Asian populations. Discussion: These 57 autosomal InDels can be used as reliable tools for forensic individual identification and paternity testing, and are more suitable for East Asian populations. Furthermore, three InDels (rs72085595, rs145941537, and rs34529639) are promising for inferring ancestral information.

Rapid DNA Profile Development with Applied Biosystems RapidHIT™ ID System

The RapidHIT™ ID System by Applied Biosystems allows the generation of a CODIS compatible STR profile in 90 min. The preloaded cartridges, fully automated workflow, and user-friendly computer interface allow for quick and simple single sample processing both in the laboratory and outside by non-laboratory personnel, like law enforcement officers. DNA processing utilizes a direct amplification workflow to generate an STR profile targeting the CODIS or ESS core loci. In conjunction with the RapidLINK™ Software, the system performs an initial analysis, flagging any profiles that do not meet single-source full profile parameters. Additionally, the RapidLINK™ allows for users to manage a multi-instrument/multi-location Rapid DNA system and view results in real-time. This gives users off-site the ability to track and even analyze results. The system allows for rapid reference sample analysis in locations like booking stations and national or border security agencies to obtain quick feedback of database hits for investigative leads while the subject is still in custody. RapidHIT™ ID DNA systems can also be set up at sites to aid in victim identification during mass disasters. The following chapter describes the process of generating a forensic DNA profile using the RapidHIT™ ID instrumentation from start to finish. Additionally, basic use and analysis using the RapidLINK™ and GeneMarker™ HID software is included.

SGAEMDA: Predicting miRNA-Disease Associations Based on Stacked Graph Autoencoder

MicroRNA (miRNA)-disease association (MDA) prediction is critical for disease prevention, diagnosis, and treatment. Traditional MDA wet experiments, on the other hand, are inefficient and costly.Therefore, we proposed a multi-layer collaborative unsupervised training base model called SGAEMDA (Stacked Graph Autoencoder-Based Prediction of Potential miRNA-Disease Associations). First, from the original miRNA and disease data, we defined two types of initial features: similarity features and association features. Second, stacked graph autoencoder is then used to learn unsupervised low-dimensional representations of meaningful higher-order similarity features, and we concatenate the association features with the learned low-dimensional representations to obtain the final miRNA-disease pair features. Finally, we used a multilayer perceptron (MLP) to predict scores for unknown miRNA-disease associations. SGAEMDA achieved a mean area under the ROC curve of 0.9585 and 0.9516 in 5-fold and 10-fold cross-validation, which is significantly higher than the other baseline methods. Furthermore, case studies have shown that SGAEMDA can accurately predict candidate miRNAs for brain, breast, colon, and kidney neoplasms.

The Impact of Leukemia on the Detection of Short Tandem Repeat (STR) Markers

INTRODUCTION

Short tandem repeats (STRs) have been used for various identity typing methods worldwide. They have high discrimination power in human identification in forensics, paternity testing, missed personal identification, genetic diseases, and gene regulatory functions. They have also been used to detect and monitor the stability of diseases, including various types of cancer. This study aimed to investigate the impact of leukemia on the detection and stability of STR markers.

METHODS

DNA was isolated from 30 participants (15 with chronic myeloid leukemia( CML) and 15 healthy controls) and used to amplify STR markers using specific primers.

RESULTS

We found that the blood of those with leukemia had more 9.3 and 9 alleles at the tyrosine hydroxylase 1 (TH01) marker than the blood of the healthy control samples. The results of this study will help researchers understand leukemia's effect on the detection and stability of STR markers in leukemic patients compared to healthy individuals.

CONCLUSION

Our results demonstrate that STR markers could become useful in genetic studies of leukemia cases.

Performance Evaluation of a Novel Ultrafast Molecular Diagnostic Device Integrated With Microfluidic Chips and Dual Temperature Modules

Ultrafast, portable, and inexpensive molecular diagnostic platforms are critical for clinical diagnosis and on-site detection. There are currently no available real-time polymerase chain reaction (PCR) devices able to meet the demands of point-of-care testing, as the heating and cooling processes cannot be avoided. In this study, the dual temperature modules were first designed to process microfluidic chips automatically circulating between them. Thus, a novel ultrafast molecular diagnostic real-time PCR device (approximately 18 and 23 min for DNA and RNA detection, respectively) with two channels (FAM and Cy5) for the detection of 12 targets was developed. The device contained three core functional components, including temperature control, optics, and motion, which were integrated into a portable compact box. The temperature modules accurately control temperature in rapid thermal cycles with less than ±0.1 °C, ±1 °C and ±0.5 °C for the temperature fluctuation, uniformity, and error of indication, respectively. The average coefficient of variation (CV) of the fluorescence intensity (FI) for all 12 wells was 2.3% for FAM and 2.7% for Cy5. There was a good linear relationship between the concentrations of fluorescent dye and the FIs of FAM and Cy5(R² = 0.9990 and 0.9937), and the average CVs of the Ct values calculated by the embedded software were 1.4% for FAM and Cy5, respectively. The 100 double-blind mocked sputum and 249 clinical stool samples were analyzed by the ultrafast real-time PCR device in comparison with the DAAN Gene SARS-CoV-2 kit run on the ABI 7500 instrument and Xpert C. difficile/Epi, respectively. Among the 249 stool samples, the ultrafast real-time PCR device detected toxigenic C. difficile in 54 samples (54/249, 21.7%) with a specificity and positive predictive values of 99.0 and 96.3%, which were higher than the Xpert C. difficile/Epi values of 94.4 and 88.1% (p > 0.05). The ultrafast real-time PCR device detected 15 SARS-CoV-2 positive samples, which has a 100% concordance with that obtained by the DAAN Gene SARS-CoV-2 kit. This study demonstrated that the ultrafast real-time PCR device integrated with microfluidic chips and dual temperature modules is an ultrafast, reliable, easy-to-use, and cost-effective molecular diagnostic platform for clinical diagnosis and on-site testing, especially in resource-limited settings.

Review of direct PCR and Rapid DNA approaches to streamline sexual assault kit testing

Crime laboratories have been faced with large casework backlogs due to lengthy processing times, limited resources and scientists, and rising crime rates. Evidence related to sexual assault crimes, specifically sexual assault kits (SAKs), heavily contribute to the reported backlogs. Although more sensitive, faster chemistries and automated techniques have been implemented over the years, the traditional STR workflow remains relatively unchanged. Enhanced workflows such as direct PCR and Rapid DNA have the potential to streamline the processing of forensic evidence items including those commonly submitted in SAKs, but the FBI QAS guidelines restrict CODIS-approved labs from implementing these methods for forensic samples. Recent studies have shown decreased turnaround times and improved or comparable profiling success with both approaches. However, review of the literature shows a lack of in-depth research comparing traditional DNA workflows to faster and more sensitive direct PCR and/or Rapid DNA approaches for evidentiary samples, especially for SAKs. By providing the forensic science and criminal justice communities with the strengths and limitations of direct PCR and Rapid DNA methods, stakeholders and policy makers may be better informed.

Genetic characterization evaluation of a novel multiple system containing 57 deletion/insertion polymorphic loci with short amplicons in Hunan Han population and its intercontinental populations analyses

Deletion/insertion polymorphism (DIP) is a promising genetic marker of DNA length polymorphism. However, there are relatively few studies on the exploration of DIP genetic polymorphisms and investigation of population genetic data at present, which limits its application in forensic identification. In this study, the genetic polymorphisms of 57 autosomal DIPs and forensic application evaluations of the novel panel were analyzed in Chinese Hunan Han population using capillary electrophoresis platform, andthe differences of genetic polymorphic distributions at these loci were compared among the Hunan Han and 26 reference populations. The present results showed the combination of total 57 DIPs could be a robust tool for forensic individual identification and paternity testing. Due to the different allele frequency distributions in the different continental populations, the system could also effectively distinguish among East Asian, European and African populations.

Nucleic Acid Tests for Clinical Translation

Nucleic acids, including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are natural biopolymers composed of nucleotides that store, transmit, and express genetic information. Overexpressed or underexpressed as well as mutated nucleic acids have been implicated in many diseases. Therefore, nucleic acid tests (NATs) are extremely important. Inspired by intracellular DNA replication and RNA transcription, in vitro NATs have been extensively developed to improve the detection specificity, sensitivity, and simplicity. The principles of NATs can be in general classified into three categories: nucleic acid hybridization, thermal-cycle or isothermal amplification, and signal amplification. Driven by pressing needs in clinical diagnosis and prevention of infectious diseases, NATs have evolved to be a rapidly advancing field. During the past ten years, an explosive increase of research interest in both basic research and clinical translation has been witnessed. In this review, we aim to provide comprehensive coverage of the progress to analyze nucleic acids, use nucleic acids as recognition probes, construct detection devices based on nucleic acids, and utilize nucleic acids in clinical diagnosis and other important fields. We also discuss the new frontiers in the field and the challenges to be addressed.

The development of miniSTRs as a method for high-speed direct PCR

There are situations in which it would be very valuable to have a DNA profile within a short time; for example, in mass disasters or airport security. In previous work, we have promoted reduced size STR amplicons for the analysis of degraded DNA. We also noticed that shorter amplicons are more robust during amplification, making them inhibition resistant, and potentially applicable to high-speed direct PCR. Here, we describe a set of miniSTRs capable of rapid direct PCR amplification. The selected markers are a subset of the Combined DNA Index System (CODIS) loci modified to permit high-speed amplification. Using the proposed protocol, the amplification of eight loci plus amelogenin directly from a saliva sample can be completed in 7 min and 38 s using a two-step PCR with 30 cycles of 98°C for 2 s and 62°C for 7 s on a Streck Philisa thermocycler. Selection of DNA polymerase, optimization of the two-step PCR cycling conditions, the primer concentrations, and the dilution of saliva is described. This method shows great potential as a quick screening method to obtain a presumptive DNA profile when time is limited, particularly when combined with high-speed separation and detection methods.

Evaluation of three microhaplotypes in individual identification and ancestry inference

Microhaplotype as an emerging genetic marker has attracted more attention in forensic field. The purpose of this study was to evaluate the potential of microhaplotypes in individual identification and ancestry inference in Chinese Hainan Li and 26 1000 G populations. Three microhaplotypes were genotyped from 100 Li individuals using Agena MassARRAY. Moreover, 2504 individuals from 26 populations (1000 Genomes Project database) were enrolled. The genotypes frequencies of microhaplotypes in each population were calculated by the Plink software. We used Structure, Arlequin, and MEGA6 software to analyze the genetic structure, differentiation and genetic background difference, respectively. The forensic parameters of these microhaplotypes were calculated using Modified Powerstats software. The distribution of genotypes frequencies of three microhaplotypes elaborated the high diversities among the Li and 26 1000 G populations. Li population had a close genetic relationship with EAS populations using structure analysis. No differentiation was observed between Li and CHS population by Fst analysis. The NJ tree showed that the genetic background of Li and CHS is most similar. The average heterozygosity (HE), probability of match (PM), power of discrimination (PD), probability of exclusion (PE) and polymorphism information content (PIC) values for the three microhaplotypes in 27 populations were 0.535, 0.497, 0.465, 0.325, and 0.481, respectively. In conclusion, our results revealed three microhaplotypes as individual identification and ancestry inference genetic markers among Li population and 26 1000 G populations. Future studies are needed to confirm our results with larger samples and select much higher forensic efficacy microhaplotypes.

A Guide to COVID-19: a global pandemic caused by the novel coronavirus SARS-CoV-2

The emergence of the SARS-CoV-2 strain of the human coronavirus has thrown the world into the midst of a new pandemic. In the human body, the virus causes COVID-19, a disease characterized by shortness of breath, fever, and pneumonia, which can be fatal in vulnerable individuals. SARS-CoV-2 has characteristics of past human coronaviruses, with close genomic similarities to SARS-CoV, the virus that causes the disease SARS. Like these related coronaviruses, SARS-CoV-2 is transmitted through the inhalation of droplets and interaction with contaminated surfaces. Across the world, laboratories are developing candidate vaccines for the virus - with vaccine trials underway in the United States and the United Kingdom - and considering various drugs for possible treatments and prophylaxis. Here, we provide an overview of SARS-CoV-2 by analyzing its virology, epidemiology, and modes of transmission while examining the current progress of testing procedures and possible treatments through drugs and vaccines.

Establishment and evaluation of a method for efficient screening of Clostridium butyricum

At present, the traditional methods for the screening of Clostridium butyricum are not sufficiently selective and efficient. Therefore, it is necessary to establish a targeted and efficient screening method for the detection of C. butyricum. Bioinformatics was used in this study to find C. butyricum specific genes, and species-specific primers were designed based on the conserved regions of the targeted genes, followed by optimization of the PCR conditions. Methodological evaluation was carried out, and the results were compared with the traditional screening method based on Trypticase Sulfite Neomycin (TSN) selective medium. A high-efficiency PCR screening method, targeting C. butyricum species-specific primers, was established. The method was confirmed to have high specificity and sensitivity towards C. butyricum cut-off CFU 10³. Compared with the traditional method, the screening success rate of C. butyricum strains increased from 0.61 to 81.91%. The PCR screening method could quickly and accurately detect C. butyricum in samples and dramatically improve screening efficiency.

Low temperature isothermal amplification of microsatellites drastically reduces stutter artifact formation and improves microsatellite instability detection in cancer

Microsatellites are polymorphic short tandem repeats of 1–6 nucleotides ubiquitously present in the genome that are extensively used in living organisms as genetic markers and in oncology to detect microsatellite instability (MSI). While the standard analysis method of microsatellites is based on PCR followed by capillary electrophoresis, it generates undesirable frameshift products known as ‘stutter peaks’ caused by the polymerase slippage that can greatly complicate the analysis and interpretation of the data. Here we present an easy multiplexable approach replacing PCR that is based on low temperature isothermal amplification using recombinase polymerase amplification (LT-RPA) that drastically reduces and sometimes completely abolishes the formation of stutter artifacts, thus greatly simplifying the calling of the alleles. Using HT17, a mononucleotide DNA repeat that was previously proposed as an optimal marker to detect MSI in tumor DNA, we showed that LT-RPA improves the limit of detection of MSI compared to PCR up to four times, notably for small deletions, and simplifies the identification of the mutant alleles. It was successfully applied to clinical colorectal cancer samples and enabled detection of MSI. This easy-to-handle, rapid and cost-effective approach may deeply improve the analysis of microsatellites in several biological and clinical applications.

Forensic features and genetic background exploration of a new 47-autosomal InDel panel in five representative Han populations residing in Northern China

BACKGROUND

Insertion/deletion (InDel) analysis plays an indispensable role in human identification, population genetics, and biogeographic research. Profiles of individuals in forensic applications worldwide based on a set of autosomal InDel loci (A-InDels) in human genomes have been widely used over the past few years.

METHODS

The new AGCU InDel 50 Kit contains 47 well-chosen A-InDels, ensuring high discriminatory power, and the 2 Y chromosome InDel loci (Y-InDels) are used for sex determination in case of allele dropout at Amelogenin. In this study, five Northern Han populations residing in different geographic areas of China were recruited and genotyped using the assay.

RESULTS

After Bonferroni correction, all 47 A-InDels were in accordance with the lack of significant departures of Hardy-Weinberg equilibrium in all loci and investigated groups. The combined probability of discrimination and the probability of exclusion in the Han population range from 1-3.2240 × 10-19 to 1-1.3030 × 10-19 and 0.9997, respectively. A comprehensive population genetic relationship investigation between Han Chinese and 26 worldwide populations based on allele frequency correlation was carried out. Our results revealed no significant genetic differentiation in Chinese Han groups. Hierarchical clustering, phylogenetic relationship reconstructions, multidimensional scaling, principal component analysis, and structure analysis were performed, and the results indicated that, genetically, Han populations are closely related to East Asians.

CONCLUSION

Overall, this novel 47 A-InDel assay is a valuable tool that could potentially be used for forensic identification and parentage tests.

Results of the 2018 Rapid DNA Maturity Assessment

Three commercially available integrated rapid DNA instruments were tested as a part of a rapid DNA maturity assessment in July of 2018. The assessment was conducted with sets of blinded single-source reference samples provided to participants for testing on the individual rapid platforms within their laboratories. The data were returned to the National Institute of Standards and Technology (NIST) for review and analysis. Both FBI-defined automated review (Rapid DNA Analysis) and manual review (Modified Rapid DNA Analysis) of the datasets were conducted to assess the success of genotyping the 20 Combined DNA Index System (CODIS) core STR loci and full profiles generated by the instruments. Genotype results from the multiple platforms, participating laboratories, and STR typing chemistries were combined into a single analysis. The Rapid DNA Analysis resulted in a success rate of 80% for full profiles (85% for the 20 CODIS core loci) with automated analysis. Modified Rapid DNA Analysis resulted in a success rate of 90% for both the CODIS 20 core loci and full profiles (all attempted loci per chemistry). An analysis of the peak height ratios demonstrated that 95% of all heterozygous alleles were above 59% heterozygote balance. For base-pair sizing precision, the precision was below the standard 0.5 bp deviation for both the ANDE 6C System and the RapidHIT 200.

Prediction of Potential miRNA-Disease Associations Through a Novel Unsupervised Deep Learning Framework with Variational Autoencoder

The important role of microRNAs (miRNAs) in the formation, development, diagnosis, and treatment of diseases has attracted much attention among researchers recently. In this study, we present an unsupervised deep learning model of the variational autoencoder for MiRNA–disease association prediction (VAEMDA). Through combining the integrated miRNA similarity and the integrated disease similarity with known miRNA–disease associations, respectively, we constructed two spliced matrices. These matrices were applied to train the variational autoencoder (VAE), respectively. The final predicted association scores between miRNAs and diseases were obtained by integrating the scores from the two trained VAE models. Unlike previous models, VAEMDA can avoid noise introduced by the random selection of negative samples and reveal associations between miRNAs and diseases from the perspective of data distribution. Compared with previous methods, VAEMDA obtained higher area under the receiver operating characteristics curves (AUCs) of 0.9118, 0.8652, and 0.9091 ± 0.0065 in global leave-one-out cross validation (LOOCV), local LOOCV, and five-fold cross validation, respectively. Further, the AUCs of VAEMDA were 0.8250 and 0.8237 in global leave-one-disease-out cross validation (LODOCV), and local LODOCV, respectively. In three different types of case studies on three important diseases, the results showed that most of the top 50 potentially associated miRNAs were verified by databases and the literature.

Genetic diversity, structure and forensic characteristics of Hmong-Mien-speaking Miao revealed by autosomal insertion/deletion markers

Insertion/deletion (Indel) genetic markers have special features compared to other forensic-related markers, such as the low mutation rate and di-allelic markers with length polymorphism, playing an indispensable role in the forensic and population genetics, molecular anthropology and evolutionary biology. However, the genetic diversity, allelic frequency, forensic parameters and population genetic characteristics of the Indel markers in Hmong-Mien-speaking Guizhou Miao people are unclear due to the sparse sampling. Thus, we genotyped 30 forensic-related Indel markers in 311 unrelated healthy Miao individuals (149 females and 161 males) residing in the Guizhou Province in Southwest China using the Investigator DIPplex amplification system. All 30 Indels are in accordance with the no departures of Hardy-Weinberg equilibrium and linkage disequilibrium. The combined probability of discrimination and the probability of exclusion in Guizhou Miao population are 0.999999999948 and 0.9843, respectively. This observed ideal forensic parameter estimates indicate that this di-allelic Indel panel can be used as a supplementary tool in forensic retinue personal identification and complemented for autosomal STRs in the parentage testing in Miao population, especially used as the main tool in old or highly degraded samples in disaster victim identification. Eleven Indels show a high allele frequency difference between different continental populations and could be used as ancestry-informative markers in forensic ancestry inference. Phylogenetic relationships between Guizhou Miao and 68 worldwide populations based on the genetic polymorphisms of Indels are investigated via three different pairwise genetic distances, principal component analysis, multidimensional scaling analysis and phylogenetic relationship reconstructions. Analyses of the comprehensive population genetic relationship comparison reveal significant genetic differentiation of Chinese groups. Our results demonstrate that Guizhou Miao people are genetically closer related to the geographically adjacent populations, especially with Liangshan Yi, Guangxi Miao and Dong, but genetically distinct with Turkic-speaking populations. Comprehensive and precise genetic admixture and divergence history of Guizhou Miao and neighboring populations are needed to further investigate and reconstruct via high-density marker panel or whole-genome sequencing of modern or ancient Miao samples.

Practical applications of DNA genotyping in diagnostic pathology

INTRODUCTION

Among various human tissue identity testing platforms, short tandem repeat (STR) genotyping has emerged as the most powerful and cost-effective method. Beyond forensic applications, tissue identity testing has become increasingly important in modern medical practice, in areas such as diagnostic pathology. Areas covered: A brief overview of various molecular/genetic techniques for identity testing is provided. This includes restriction fragment length polymorphism, single nucleotide polymorphism array and STR genotyping by multiplex PCR. Diagnostic applications of STR genotyping are covered in greater details: genotyping diagnosis of gestational trophoblastic disease, resolving tissue specimen mislabeling or histologic contaminant or 'floaters', bone marrow engraftment/chimerism analysis and interrogation of the primary source of malignancy in patients receiving organ donation. Four clinical cases are then presented to further illustrate these important clinical applications along with discussion of the interpretation, limitations, and pitfalls of STR genotyping. Expert commentary: STR genotyping is currently the most applicable method of identity testing and has extended its role well into the practice of diagnostic pathology with novel and powerful applications beyond forensics.

DNA testing in homicide investigations

Objectives With the widespread use of DNA testing, police, death investigators, and attorneys need to be aware of the capabilities of this technology. This review provides an overview of scenarios where DNA evidence has played a major role in homicide investigations in order to highlight important educational issues for police, death investigators, forensic pathologists, and attorneys. Methods This was a nonrandom, observational, retrospective study. Data were obtained from the collective files of the authors from casework during a 15-year period, from 2000 through 2014. Results A series of nine scenarios, encompassing 11 deaths, is presented from the standpoint of the police and death investigation, the forensic pathology autopsy performance, the subsequent DNA testing of evidence, and, ultimately, the final adjudication of cases. Details of each case are presented, along with a discussion that focuses on important aspects of sample collection for potential DNA testing, especially at the crime scene and the autopsy. The presentation highlights the diversity of case and evidence types in which DNA testing played a valuable role in the successful prosecution of the case. Conclusions By highlighting homicides where DNA testing contributed to the successful adjudication of cases, police, death investigators, forensic pathologists, and attorneys will be better informed regarding the types of evidence and situations where such testing is of potential value.

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.

Microfluidic Devices for Forensic DNA Analysis: A Review

Microfluidic devices may offer various advantages for forensic DNA analysis, such as reduced risk of contamination, shorter analysis time and direct application at the crime scene. Microfluidic chip technology has already proven to be functional and effective within medical applications, such as for point-of-care use. In the forensic field, one may expect microfluidic technology to become particularly relevant for the analysis of biological traces containing human DNA. This would require a number of consecutive steps, including sample work up, DNA amplification and detection, as well as secure storage of the sample. This article provides an extensive overview of microfluidic devices for cell lysis, DNA extraction and purification, DNA amplification and detection and analysis techniques for DNA. Topics to be discussed are polymerase chain reaction (PCR) on-chip, digital PCR (dPCR), isothermal amplification on-chip, chip materials, integrated devices and commercially available techniques. A critical overview of the opportunities and challenges of the use of chips is discussed, and developments made in forensic DNA analysis over the past 10–20 years with microfluidic systems are described. Areas in which further research is needed are indicated in a future outlook.

A Genome-Wide Scan of DNA Methylation Markers for Distinguishing Monozygotic Twins

Identification of individuals within pairs of monozygotic (MZ) twins remains unresolved using common forensic DNA typing technology. For some criminal cases involving MZ twins as suspects, the twins had to be released due to inability to identify which of the pair was the perpetrator. In this study, we performed a genome-wide scan on whole blood-derived DNA from four pairs of healthy phenotypically concordant MZ twins using the methylated DNA immunoprecipitation sequencing technology to identify candidate DNA methylation markers with capacity to distinguish MZ twins within a pair. We identified 38 differential methylation regions showing within-pair methylation differences in all four MZ pairs. These are all located in CpG islands, 17 of which are promoter-associated, 17 are intergenic islands, and four are intragenic islands. Genes associated with these markers are related with cell proliferation, differentiation, and growth and development, including zinc finger proteins, PRRX2, RBBP9, or are involved in G-protein signaling, such as the regulator of G-protein signaling 16. Further validation studies on additional MZ twins are now required to evaluate the broader utility of these 38 markers for forensic use.