MHBase: A comprehensive database of short microhaplotypes for advancing forensic genetic analysis.

Microhaplotypes (MHs) were first recommended by Prof. Kidd for use in forensics because they can improve human identification, kinship analysis, mixture deconvolution, and ancestry prediction. Since their introduction, extensive research has demonstrated the advantages of MHs in forensic applications and provided useful data for different populations. Currently, two databases, ALFRED (ALlele FREquency Database) and MicroHapDB (MicroHaplotype DataBase), house the published MH information and population data. We previously constructed a single nucleotide polymorphism SNP-SNP MH database (D-SNPsDB) of MHs within 50 bp on the whole human genome for 26 populations integrating basic data such as physical genome positions, mapping of variant identifiers (rsIDs), allele frequencies, and basic variant information. Building upon the previous research, we further selected MHs containing at least two variants (SNPs and/or insertions/deletions [InDels]) within a short DNA fragment (≤ 50 bp) in 26 populations based on the 1000 Genomes Project dataset (Phase 3) to construct a more comprehensive database. Subsequently, we established a user-friendly website that allows users to search the MH database (MHBase) based on their research objectives and study population to find suitable loci and provides other functions such as querying reported loci, performing online calculations using the PHASE software, and calculating ancestral-related parameters. The loci in the database are classified as SNP-based MHs, which include only SNPs, and InDel-including MHs, which contain at least one InDel. Here, we provide a detailed overview of the MHBase and an analysis of shared loci at the global and continental levels, ancestral markers, the genetic distance within loci, and mapping with the genome annotation file. The website is an accessible and useful tool for researchers engaged in marker discovery, population studies, assay development, and panel design.

Developmental validation of an mRNA kit: A 5-dye multiplex assay designed for body-fluid identification.

Identifying the sources of biosamples found at crime scenes is crucial for forensic investigations. Among the markers used for body fluid identification (BFI), mRNA has emerged as a well-studied marker because of its high specificity and remarkable stability. Despite this potential, commercially available mRNA kits specifically designed for BFI are lacking. Therefore, we developed an mRNA kit that includes 21 specific mRNA markers of body fluids, along with three housekeeping genes for BFI, to identify four forensic-relevant fluids (blood, semen, saliva, and vaginal fluids). In this study, we tested 451 single-body-fluid samples, validated the universality of the mRNA kit, and obtained a gene expression profile. We performed the validation studies in triplicates and determined the sensitivity, specificity, stability, precision, and repeatability of the mRNA kit. The sensitivity of the kit was found to be 0.1 ng. Our validation process involved the examination of 59 RNA mixtures, 60 body fluids mixtures, and 20 casework samples, which further established the reliability of the kit. Furthermore, we constructed five classifiers that can handle single-body fluids and mixtures using this kit. The classifiers output possibility values and identify the specific body fluids of interest. Our results showed the reliability and suitability of the BFI kit, and the Random Forest classifier performed the best, with 94% precision. In conclusion, we developed an mRNA kit for BFI which can be a promising tool for forensic practice.

From degraded to deciphered: ATAC-seq's application potential in forensic diagnosis.

In recent years, molecular biology-based diagnostic techniques have made remarkable strides and are now extensively utilized in clinical practice, providing invaluable insights for disease diagnosis and treatment. However, forensic medicine, especially forensic pathology, has witnessed relatively limited progress in the application of molecular biology technologies. A significant challenge in employing molecular techniques for forensic diagnoses lies in the quantitative and qualitative changes observed in diagnostic markers due to sample degradation-a recognized and formidable obstacle. Inspired by the success of DNA sequencing in forensic practices, which enables accurate individual identification even in cases involving degraded and deteriorated tissues and organs, we propose the application of the assay for transposase-accessible chromatin with sequencing (ATAC-seq) to identify targets at the transcriptional onset, exploring chromatin and DNA-level alterations for injury and disease inference in forensic samples. This study employs ATAC-seq to explore alterations in chromatin accessibility post-injury and their subsequent changes over a 2-h degradation period, employing traumatic brain injury (TBI) as a representative model. Our findings reveal high sensitivity of chromatin accessibility sites to injury, evidenced by shifts in thousands of peak positions post-TBI. Remarkably, these alterations remain largely unaffected by early degradation. Our results robustly endorse the notion that integrating and incorporating these specific loci for injury and disease diagnosis in forensic samples holds tremendous promise for practical application. We further validated the above results using human cortical tissue, which supported that early degradation did not significantly affect chromatin accessibility. This pioneering advancement in molecular diagnostic techniques may revolutionize the field of forensic science, especially forensic pathology.

Development of a coding SNP panel for tracking the origin of whole-exome sequencing samples.

Whole-exome sequencing (WES) is widely used to diagnose complex genetic diseases and rare conditions. The implementation of a robust and effective quality control system for sample identification and tracking throughout the WES process is essential. We established a multiplex panel that included 22 coding single-nucleotide polymorphism (cSNP) loci. The personal identification and paternity identification abilities of the panel were evaluated, and a preliminary validation of the practical feasibility of the panel was conducted in a clinical WES case. These results indicate that the cSNP panel could be a useful tool for sample tracking in WES.

Optimizing Analytical Thresholds for Low-Template DNA Analysis: Insights from Multi-Laboratory Negative Controls.

When analyzing challenging samples, such as low-template DNA, analysts aim to maximize information while minimizing noise, often by adjusting the analytical threshold (AT) for optimal results. A potential approach involves calculating the AT based on the baseline signal distribution in electrophoresis results. This study investigates the impact of reagent kits, testing quarters, environmental conditions, and amplification cycles on baseline signals using historical records and experimental data on low-template DNA. Variations in these aspects contribute to differences in baseline signal patterns. Analysts should remain vigilant regarding routine instrument maintenance and reagent replacement, as these may affect baseline signals. Prompt analysis of baseline status and tailored adjustments to ATs under specific laboratory conditions are advised. A comparative analysis of published methods for calculating the optimal AT from a negative signal distribution highlighted the efficiency of utilizing baseline signals to enhance forensic genetic analysis, with the exception of extremely low-template samples and high-amplification cycles. Moreover, a user-friendly program for real-time analysis was developed, enabling prompt adjustments to ATs based on negative control profiles. In conclusion, this study provides insights into baseline signals, aiming to enhance genetic analysis accuracy across diverse laboratories. Practical recommendations are offered for optimizing ATs in forensic DNA analysis.

Improving DNA mixtures analysis using compound markers composed of InDels and SNPs screened from the whole genome with next-generation sequencing.

Next-generation sequencing (NGS) allows for better identification of insertion and deletion polymorphisms (InDels) and their combination with adjacent single nucleotide polymorphisms (SNPs) to form compound markers. These markers can improve the polymorphism of microhaplotypes (MHs) within the same length range, and thus, boost the efficiency of DNA mixture analysis. In this study, we screened InDels and SNPs across the whole genome and selected highly polymorphic markers composed of InDels and/or SNPs within 300 bp. Further, we successfully developed and evaluated an NGS-based panel comprising 55 loci, of which 24 were composed of both SNPs and InDels. Analysis of 124 unrelated Southern Han Chinese revealed an average effective number of alleles (Ae ) of 7.52 for this panel. The cumulative power of discrimination and cumulative probability of exclusion values of the 55 loci were 1-2.37 × 10-73 and 1-1.19 × 10-28 , respectively. Additionally, this panel exhibited high allele detection rates of over 97% in each of the 21 artificial mixtures involving from two to six contributors at different mixing ratios. We used EuroForMix to calculate the likelihood ratio (LR) and evaluate the evidence strength provided by this panel, and it could assess evidence strength with LR, distinguishing real and noncontributors. In conclusion, our panel holds great potential for detecting and analyzing DNA mixtures in forensic applications, with the capability to enhance routine mixture analysis.

Assessment of ForenSeq mtDNA Whole Genome Kit for forensic application.

Mitochondrial DNA (mtDNA) is an indispensable genetic marker in forensic genetics. The emergence and development of massively parallel sequencing (MPS) makes it possible to obtain complete mitochondrial genome sequences more quickly and accurately. The study evaluated the advantages and limitations of the ForenSeq mtDNA Whole Genome Kit in the practical application of forensic genetics by detecting human genomic DNA standards and thirty-three case samples. We used control DNA with different amount to determine sensitivity of the assay. Even when the input DNA is as low as 2.5 pg, most of the mitochondrial genome sequences could still be covered. For the detection of buccal swabs and aged case samples (bloodstains, bones, teeth), most samples could achieve complete coverage of mitochondrial genome. However, when ancient samples and hair samples without hair follicles were sequenced by the kit, it failed to obtain sequence information. In general, the ForenSeq mtDNA Whole Genome Kit has certain applicability to forensic low template and degradation samples, and these results provide the data basis for subsequent forensic applications of the assay. The overall detection process and subsequent analysis are easy to standardize, and it has certain application potential in forensic cases.

Development of specific and rapid detection of human DNA by recombinase polymerase amplification assay for forensic analysis.

The determination of human-derived samples is very important in forensic investigations and case investigation in order to determine vital information on the suspect and the case. In this study, we established a recombinase polymerase amplification (RPA) assay for rapid identification of human-derived components. The sensitivity of the assay was 0.003125 ng, with excellent species specificity, and human-derived DNA could be detected in the presence of non-human-derived components at a ratio of 1:1000. Moreover, the RPA assay had a strong tolerance to inhibitors, in the presence of 800 ng/µL humic acid, 400 ng/µL tannic acid, and 8000 ng/µL collagen. In forensic investigation, common body fluids (blood, saliva, semen, vaginal secretions) are all applicable, and the presence of DNA can be detected from samples after simple alkaline lysis, which greatly shortens the detection time. Four simulation and case samples (aged bones, aged bloodstains, hair, touch DNA) were also successfully applied. The above research results show that the RPA assay constructed in this study can be fully applied to forensic medicine to provide high sensitivity and applicability detection methods.

Evaluation of microhaplotype panels for complex kinship analysis using massively parallel sequencing.

In recent years, microhaplotypes (MHs) have become a research hotspot within the field of forensic genetics. Traditional MHs contain only SNPs that are closely linked within short fragments. Herein, we broaden the concept of general MHs to include short InDels. Complex kinship identification plays an important role in disaster victim identification and criminal investigations. For distant relatives (e.g., 3rd-degree), many genetic markers are required to enhance power of kinship testing. We performed genome-wide screening for new MH markers composed of two or more variants (InDel or SNP) within 220 bp based on the Chinese Southern Han from the 1000 Genomes Project. An NGS-based 67plex MH panel (Panel B) was successfully developed, and 124 unrelated individual samples were sequenced to obtain population genetic data, including alleles and allele frequencies. Of the 67 genetic markers, 65 MHs were, as far as we know, newly discovered, and 32 MHs had effective number of allele (Ae) values greater than 5.0. The average Ae and heterozygosity of the panel were 5.34 and 0.7352, respectively. Next, 53 MHs from a previous study were collected as Panel A (average Ae of 7.43), and Panel C with 87 MHs (average Ae of 7.02) was formed by combining Panels A and B. We investigated the utility of these three panels in kinship analysis (parent-child, full siblings, 2nd-degree, 3rd-degree, 4th-degree, and 5th-degree relatives), with Panel C exhibiting better performance than the two other panels. Panel C was able to separate parent-child, full-sibling, and 2nd-degree relative duos from unrelated controls in real pedigree data, with a small false testing level (FTL) of 0.11% in simulated 2nd-degree duos. For more distant relationships, the FTL was much higher: 8.99% for 3rd-degree, 35.46% for 4th-degree, and 61.55% for 5th-degree. When a carefully chosen extra relative was known, this may enhance the testing power for distant kinship analysis. Two twins from the Q family (2-5 and 2-7) and W family (3-18 and 3-19) shared the same genotypes in all tested MHs, which led to the incorrect conclusion that an uncle-nephew duo was classified as a parent-child duo. In addition, Panel C showed great capacity for excluding close relatives (2nd-degree and 3rd-degree relatives) during paternity tests. Among 18,246 real and 10,000 simulated unrelated pairs, none were misinterpreted as a relative within 2nd-degree at a log10(LR) cutoff of 4. The panels presented herein could provide supplementary power for the analysis of complex kinship.

An MPS-Based 50plex Microhaplotype Assay for Forensic DNA Analysis.

Microhaplotypes (MHs) are widely accepted as powerful markers in forensic studies. They have the advantage of both short tandem repeats (STRs) and single nucleotide polymorphisms (SNPs), with no stutter and amplification bias, short fragments and amplicons, low mutation and recombination rates, and high polymorphisms. In this study, we constructed a panel of 50 MHs that are distributed on 21 chromosomes and analyzed them using the Multiseq multiple polymerase chain reaction (multi-PCR) targeted capture sequencing protocol based on the massively parallel sequencing (MPS) platform. The sizes of markers and amplicons ranged between 11-81 bp and 123-198 bp, respectively. The sensitivity was 0.25 ng, and the calling results were consistent with Sanger sequencing and the Integrative Genomics Viewer (IGV). It showed measurable polymorphism among sequenced 137 Southwest Chinese Han individuals. No significant deviations in the Hardy-Weinberg equilibrium (HWE) and linkage disequilibrium (LD) were found at all MHs after Bonferroni correction. Furthermore, the specificity was 1:40 for simulated two-person mixtures, and the detection rates of highly degraded single samples and mixtures were 100% and 93-100%, respectively. Moreover, animal DNA testing was incomplete and low depth. Overall, our MPS-based 50-plex MH panel is a powerful forensic tool that provides a strong supplement and enhancement for some existing panels.

Modeling Methods and Influencing Factors for Age Estimation Based on DNA Methylation.

Age estimation based on tissues or body fluids is an important task in forensic science. The changes of DNA methylation status with age have certain rules, which can be used to estimate the age of the individuals. Therefore, it is of great significance to discover specific DNA methylation sites and develop new age estimation models. At present, statistical models for age estimation have been developed based on the rule that DNA methylation status changes with age. The commonly used models include multiple linear regression model, multiple quantile regression model, support vector machine model, artificial neural network model, random forest model, etc. In addition, there are many factors that affect the level of DNA methylation, such as the tissue specificity of methylation. This paper reviews these modeling methods and influencing factors for age estimation based on DNA methylation, with a view to provide reference for the establishment of age estimation models.

Corrigendum: A novel SNP-STR system based on a capillary electrophoresis platform.

[This corrects the article DOI: 10.3389/fgene.2021.636821.].

Establishment of a co-analysis system for personal identification and body fluid identification: a preliminary report.

Analysis of genetic markers can provide clues for case investigation. Short tandem repeat (STR) detection and analysis are widely used for both personal identification and parentage testing. However, DNA analysis currently cannot provide sufficient information for body fluid identification. Tissue or cell sources of samples can be identified by detecting body fluid-specific mRNA markers, which have been studied thoroughly. Integrating STR profiling and mRNA expression patterns can provide more information than conventional methods for investigations and the reconstruction of crime scenes; this can be achieved by DNA/RNA co-extraction technology, which is economical, efficient, and suitable for low-template samples. Here, we propose a co-analysis system based on the PowerPlex 16 kit. This system can simultaneously amplify 25 markers, including 15 STRs, one non-STR amelogenin, and nine mRNA markers (three blood-specific, two saliva-specific, two semen-specific, and two housekeeping gene markers). The specificity and sensitivity of the co-analysis system were determined and aged and degraded samples were used to validate the stability of the co-analysis system. Finally, different DNA/RNA ratios and various carriers were evaluated. The results showed that the DNA/RNA co-analysis system correctly identified different types of body fluid stains. The STR profiles obtained using the co-analysis system were identical to those obtained using the PP16 kit, which demonstrates that the mRNA primers used did not affect STR profiling. Complete STR and mRNA profiles could be obtained from 1/8 portions of buccal swabs, 1/16 portions of swabs of blood and semen samples, 0.1 cm2 of blood samples, 0.25 cm2 of semen samples, and 1.0 cm2 saliva samples. Additionally, our findings indicate that complete STR and mRNA profiles can be obtained with this system from blood and semen samples when the DNA/RNA ratio is 1:1/32. This study suggests that the co-analysis system could be used for simultaneous personal identification and body fluid identification.

An overview of SNP-SNP microhaplotypes in the 26 populations of the 1000 Genomes Project.

Microhaplotypes (MHs) are a promising new type of forensic markers that are defined by the combinations of two- or more single-nucleotide polymorphisms (SNPs) within 200 bp. Their advantages, such as low mutation rates, lack of stutter artifacts, and short amplicons, have improved human identification, kinship analysis, ancestry prediction, and mixture deconvolution capabilities. Information on published MHs, e.g., allele frequencies, is available in widely used public databases, ALlele FREquency Database, and MicroHapDB. However, there are abundant non-published MHs spread over the whole genome, and those databases do not incorporate other databases (e.g., the SNP Database) to provide users with more integrated information. Therefore, it is essential to establish a robust, responsive, and comprehensive MHs database. In this study, we thoroughly screened for SNP-SNP MHs among 26 populations from the 1000 Genomes Project (Phase 3). All genotype data of SNPs in each MH were converted to PHASE input files, and allele frequencies were estimated using PHASE. We compiled a detailed summary of SNP-SNPs at the global, continental, and population levels focused on haplotypes and the Ae value and supplemented our database using dbSNP data (last updated in 2015). We have successfully established a dual-SNP MH database (D-SNPsDB) of MHs within 50 bp for 26 populations in the integration of basic data such as physical positions in the human genome, mapping of variant identifiers (rsIDs), allele frequencies, and basic variant information. For public database queries, the D-SNPsDB web app was developed with the R Shiny package to get integrated information.

Validation of the Microreader 28A ID System: A 6-dye multiplex amplification assay for forensic application.

The Microreader 28A ID System is a new 28-plex genotyping system with 6-dye multiplex amplification, which allows the simultaneous amplification of all 20 Combined DNA Index System (CODIS) core loci (CSF1PO, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, FGA, TH01, TPOX, vWA, D1S1656, D2S441, D2S1338, D10S1248, D12S391, D19S433, D22S1045), plus five extended STRs loci (D6S1043, Penta D, Penta E, DYS391, SE33), 2 Y-Indels (Rs2032678, Rs771783753), and the amelogenin loci. This system can be used for forensic analyses, such as personal identification, kinship testing, scientific research, database applications, and other aspects of human genetic identification. The validation of the Microreader 28A ID System followed the "Validation Guidelines for DNA Analysis Methods (2016)" described by the Scientific Working Group on DNA Analysis Methods and the regulations published by the China Ministry of Public Security. Our tests included PCR-based studies, sensitivity study, precision and accuracy evaluation, stutter percentage and heterozygous peak height ratio, inhibitor tests, species specificity, and population studies. The validation results suggest that the Microreader 28A ID system is a robust and reliable amplification kit for personal identification, kinship testing, and forensic database applications.

A Novel SNP-STR System Based on a Capillary Electrophoresis Platform.

Various compound markers encompassing two or more variants within a small region can be regarded as generalized microhaplotypes. Many of these markers have been investigated for various forensic purposes, such as individual identification, deconvolution of DNA mixtures, or forensic ancestry inference. SNP-STR is a compound biomarker composed of a single nucleotide polymorphism (SNP) and a closely linked short tandem repeat polymorphism (STR), and possess the advantages of both SNPs and STRs. In addition, in conjunction with a polymerase chain reaction (PCR) technique based on the amplification refractory mutation system (ARMS), SNP-STRs can be used for forensic unbalanced DNA mixture analysis based on capillary electrophoresis (CE), which is the most commonly used platform in worldwide forensic laboratories. Our previous research reported 11 SNP-STRs, but few of them are derived from the commonly used STR loci, for which existing STR databases can be used as a reference. For maximum compatibility with existing DNA databases, in this study, we screened 18 SNP-STR loci, of which 14 were derived from the expanded CODIS core loci set. Stable and sensitive SNP-STR multiplex PCR panels based on the CE platform were established. Assays on simulated two-person DNA mixtures showed that all allele-specific primers could detect minor DNA components in 1:500 mixtures. Population data based on 113 unrelated Chengdu Han individuals were investigated. A Bayesian framework was developed for the likelihood ratio (LR) evaluation of SNP-STR profiling results obtained from two-person mixtures. Furthermore, we report on the first use of SNP-STRs in casework to show the advantages and limitations for use in practice. Compared to 2.86 × 103 for autosomal STR kits, the combined LR reached 7.14 × 107 using the SNP-STR method in this casework example.

Validation of the Microreader 40Y ID System: a Y-STR multiplex for casework and database samples.

Y-chromosome-specific short tandem repeat loci (Y-STRs) are commonly analysed in forensic science for paternity testing, familial searches, and, in sexual assault cases, to determine male DNA identity from mixed sources with high background female DNA content. The Microreader 40Y ID System is a six-dye multiplex amplification kit that contains 17 Y-STR loci from the Yfiler Plus PCR Amplification Kit and the powerplex Y23 system (DYS19, DYF385a/b, DYS389I/II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS549, DYS635(Y GATA C4), DYS643, Y GATA H4, DYS460, DYS481, DYS533, DYF387S1, DYS449, DYS518, DYS570, DYS576, and DYS627), plus six high polymorphic loci (DYS444, DYS447, DYS557, DYS596, DYS527 a/b) as well as 4 additional candidate Y-STR loci (DYS593, DYF404S1, DYS645) and a Y-Indel loci (Rs2032678), thereby providing greater efficiency, compatibility, and accuracy. The Microreader 40Y ID System can directly amplify markers from blood or saliva on filter paper or FTA cards, without template extraction or purification, and can also be used for extracted DNA templates. To verify the efficiency and accuracy of the kit, the Microreader 40Y ID System was validated by investigating sensitivity, amplification conditions, male-male and male-female mixtures, PCR inhibition, species specificity, reproducibility, and efficacy with degraded samples. The Y-STR loci were also tested using 437 male samples from Tibet, Han, and Yi. The Microreader 40Y ID System was able to compensate for some of the shortcomings of Y-STR markers in practical applications, such as cost and profile interpretation, and fully meets the domestic Y chromosome database construction specifications and requirements.

Multi-Indel: A Microhaplotype Marker Can Be Typed Using Capillary Electrophoresis Platforms.

Since the concept of microhaplotypes was proposed by Kidd in 2013, various microhaplotype markers have been investigated for various forensic purposes, such as individual identification, deconvolution of DNA mixtures, or forensic ancestry inference. In our opinion, various compound markers are also regarded as generalized microhaplotypes, encompassing two or more variants in a short segment of DNA (e.g., 200 bp). That is, a set of variants (referred to herein as multi-variants) within a certain length includes single nucleotide polymorphisms (SNP), insertion/deletion polymorphisms (Indels), or short tandem repeat polymorphisms (STRs). At present, multi-variant is mainly aimed at multi-SNPs. However, the haplotype genotyping of multi-variants relies on single-strand analysis, mainly using massively parallel sequencing (MPS). Here, we describe a method based on a capillary electrophoresis (CE) platform that can directly obtain haplotypes of individuals. Several microhaplotypes consisting of three or more Indels with different insertion or deletion lengths in the range of less than 200 bp were screened out, each of which had at least three haplotypes. As a result, the haplotype of an individual was reflected by the length of its polymorphism. Finally, we established a multiplex amplification system containing 18 multi-Indel markers that could identify haplotypes on each chromosome of an individual. The combined power of discrimination (CPD) and the cumulative probability of exclusion (CPE) were 0.999999999997234 and 0.9984, respectively.

A new approach to detect a set of SNP-SNP markers: Combining ARMS-PCR with SNaPshot technology.

Microhaplotypes are a new promising type of forensic genetic marker. Without the interference of stutter and high mutation rates as for STRs, and with short amplification lengths and a higher degree of polymorphism than single SNP, microhaplotypes composed of two SNPs, SNP-SNP, have a strong application potential. Currently, the most common method to detect microhaplotypes is massive parallel sequencing. However, the cost and extensive use of instruments limit its wide application in forensic laboratories. In this study, we screened 23 new SNP-SNP loci and established a new detection method by combining a multiplex amplification refractory mutation system-based PCR (ARMS-PCR) and SNaPshot technology based on CE. First, we introduced an additional deliberate mismatch at the antepenultimate base from the 3' end of primers when designing ARMS-PCR for SNP 1 (the first SNP of the SNP-SNP). Then, single base extension primers for SNaPshot assay were designed next to the position of SNP 2 (the second SNP). Finally, 15 loci were successfully built into four panels and these loci showed a relatively high level of polymorphism in the Southwest Chinese Han population. All the loci had an average probability of informative genotypes (I value) of 0.319 and a combined discrimination power of 0.999999999. Therefore, this new detection system will provide a valuable supplement to current methods.