Evaluation of the microhaplotype markers in kinship analysis

Performance comparison of a previously validated microhaplotype panel and a forensic STR panel for DNA mixture analysis

Short Tandem Repeats (STRs) are the most widespread markers in forensic genetics. However, STR stutter peaks can mask alleles from a minor contributor when analysing mixtures, hindering the interpretation of complex profiles. In this study we compared the performance of a previously described panel of microhaplotypes (MHs), an alternative type of forensic marker, against a standard STR kit. The parameters evaluated included: capability of determining the minimum number of contributors in the mixture; percentages of allele drop-outs and drop-ins; retrieval of alleles belonging to the minor contributor, and estimation of likelihood ratio (LR) values. In addition, the capacity of EuroForMix software to estimate each donor's percentage of contribution was tested, as well as the impact on results when using manually, or automatically prepared libraries. The MH panel showed better performance than STRs for the detection of 2-contributor mixtures, but the lower degree of polymorphism per MH marker hindered the task of deconvolution with multiple contributors. MHs presented higher drop-in rates and lower drop-out rates, a higher capability to recover the minor contributor's alleles and provided higher LR values than STRs, likely due to the much higher number of loci combined in the panel. Estimations of contributor ratios using EuroForMix showed promising results and marginal differences were found in these values between manually and automatically prepared libraries. Overall, results showed that the mixture detection performance of the MH panel was better or equal to the standard forensic autosomal STR panel, indicating microhaplotypes are informative markers for this purpose.

Developmental validation of a custom-designed Multi-InDel panel: A five-dye multiplex amplification system for challenging DNA samples

The continual investigation of novel genetic markers has yielded promising solutions for addressing the challenges encountered in forensic DNA analysis. In this study, we have introduced a custom-designed panel capable of simultaneously amplifying 41 novel Multi-insertion/deletion (Multi-InDel) markers and an amelogenin locus using the capillary electrophoresis platform. Through a developmental validation study conducted in accordance with guidelines recommended by the Scientific Working Group on DNA Analysis Methods, we demonstrated that the new Multi-InDel system exhibited the sensitivity to produce reliable genotyping profiles with as little as 62.5 pg of template DNA. Accurate and complete genotyping profiles could be obtained even in the presence of specific concentrations of PCR inhibitors. Furthermore, the maximum amplicon size for this system was limited to under 220 bp in the genotyping profile, resulting in its superior efficiency compared to commercially available short tandem repeat kits for both naturally and artificially degraded samples. In the context of mixed DNA analysis, the Multi-InDel system was proved informative in the identification of two-person DNA mixture, even when the template DNA of the minor contributor was as low as 50 pg. In conclusion, a series of performance evaluation studies have provided compelling evidence that the new Multi-InDel system holds promise as a valuable tool for forensic DNA analysis.

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 (A_e) values greater than 5.0. The average A_e 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 A_e of 7.43), and Panel C with 87 MHs (average A_e 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.

Recent advances in forensic biology and forensic DNA typing: INTERPOL review 2019-2022

This review paper covers the forensic-relevant literature in biological sciences from 2019 to 2022 as a part of the 20th INTERPOL International Forensic Science Managers Symposium. Topics reviewed include rapid DNA testing, using law enforcement DNA databases plus investigative genetic genealogy DNA databases along with privacy/ethical issues, forensic biology and body fluid identification, DNA extraction and typing methods, mixture interpretation involving probabilistic genotyping software (PGS), DNA transfer and activity-level evaluations, next-generation sequencing (NGS), DNA phenotyping, lineage markers (Y-chromosome, mitochondrial DNA, X-chromosome), new markers and approaches (microhaplotypes, proteomics, and microbial DNA), kinship analysis and human identification with disaster victim identification (DVI), and non-human DNA testing including wildlife forensics. Available books and review articles are summarized as well as 70 guidance documents to assist in quality control that were published in the past three years by various groups within the United States and around the world.

A sequence-based 163plex microhaplotype assay for forensic DNA analysis

Novel genetic marker microhaplotype has led to an upsurge in forensic genetic research. This study established a 163 microhaplotype (MH) multiplex assay based on next-generation sequencing (NGS) and evaluated the assay's performance and applicability. Our results showed that the 163 MH assay was accurate, repeatable and reliable, and could distinguish between African, European-American, Southern Asia and Eastern Asia populations. Among the 163 MH makers, 48 MHs with Ae > 3.0 in China Eastern Han were selected and confirmed to be highly polymorphic, with a combined power of discrimination of 1-8.26 × 10-44 and the combined power of exclusion in duos and trios of 1-1.26 × 10-8 and 1-8.27 × 10-16, respectively. Moreover, the mixture study demonstrated the realizability of the MHs in deconvoluting mixtures with different proportions of two to five-person. In conclusion, our findings support the use of this MH assay for ancestry inference, human identification, paternity testing and mixture deconvolution in forensic research.

The application of short and highly polymorphic microhaplotype loci in paternity testing and sibling testing of temperature-dependent degraded samples

Paternity testing and sibling testing become more complex and difficult when samples degrade. But the commonly used genetic markers (STR and SNP) cannot completely solve this problem due to some disadvantages. The novel genetic marker microhaplotype proposed by Kidd’s research group combines the advantages of STR and SNP and is expected to become a promising genetic marker for kinship testing in degraded samples. Therefore, in this study, we intended to select an appropriate number of highly polymorphic SNP-based microhaplotype loci, detect them by the next-generation sequencing technology, analyze their ability to detect degraded samples, calculate their forensic parameters based on the collected 96 unrelated individuals, and evaluate their effectiveness in paternity testing and sibling testing by simulating kinship relationship pairs, which were also compared to 15 STR loci. Finally, a short and highly polymorphic microhaplotype panel was developed, containing 36 highly polymorphic SNP-based microhaplotype loci with lengths smaller than 100 bp and Ae greater than 3.00, of which 29 microhaplotype loci could not reject the Hardy-Weinberg equilibrium and linkage equilibrium after the Bonferroni correction. The CPD and CPE of these 29 microhaplotype loci were 1-2.96E-26 and 1-5.45E-09, respectively. No allele dropout was observed in degraded samples incubated with 100°C hot water for 40min and 60min. According to the simulated kinship analysis, the effectiveness at the threshold of 4/−4 reached 98.39% for relationship parent-child vs. unrelated individuals, and the effectiveness at the threshold of 2/−2 for relationship full-sibling vs. unrelated individuals was 93.01%, which was greater than that of 15 STR loci (86.75% for relationship parent-child vs. unrelated individuals and 81.73% for relationship full-sibling vs. unrelated individuals). After combining our 29 microhaplotype loci with other 50 short and highly polymorphic microhaplotype loci, the effectiveness values at the threshold of 2/−2 were 82.42% and 90.89% for relationship half-sibling vs. unrelated individuals and full-sibling vs. half-sibling. The short and highly polymorphic microhaplotype panel we developed may be very useful for paternity testing and full sibling testing in degraded samples, and in combination with short and highly polymorphic microhaplotype loci reported by other researchers, may be helpful to analyze more distant kinship relationships.

Evaluation of the MHSeqTyper47 kit for forensically challenging DNA samples

Microhaplotypes have been highly regarded for forensic mixture DNA deconvolution because they do not experience interference from stutters in the same way as short tandem repeat markers, and they tend to be more polymorphic than single nucleotide polymorphism markers. However, forensic microhaplotype kits have not been reported. The MHSeqTyper47 kit genotypes 47 microhaplotype loci. In this study, MiSeq FGx sequencing metrics for MHSeqTyper47 were presented, and the genotyping accuracy of this kit was examined. The sensitivity of MHSeqTyper47 reached 62.5 pg, and full genotyping results were obtained from degraded DNA samples with degradation indexes ≤ 3.00. Full genotypes were obtained in the presence of 100 ng/μL tannin, 50 μM heme, 25 ng/μL humic acid, and 1.25 μg/μL indigo dye. In DNA mixture studies, a minimum of 31 loci of the minor contributor were correctly genotyped at 1:99 or 99:1 mixing ratios, with the cumulative random matching probability of these loci reaching 4.54 × 10^-25. Mixing ratios could be reliably predicted from two-donor DNA mixtures based on the loci with four called alleles. Taken together, these data showed that the MHSeqTyper47 kit was effective for forensically challenging DNA analysis.

North Asian population relationships in a global context

Population genetic studies of North Asian ethnic groups have focused on genetic variation of sex chromosomes and mitochondria. Studies of the extensive variation available from autosomal variation have appeared infrequently. We focus on relationships among population samples using new North Asia microhaplotype data. We combined genotypes from our laboratory on 58 microhaplotypes, distributed across 18 autosomes, on 3945 individuals from 75 populations with corresponding data extracted for 26 populations from the Thousand Genomes consortium and for 22 populations from the GenomeAsia 100 K project. A total of 7107 individuals in 122 total populations are analyzed using STRUCTURE, Principal Component Analysis, and phylogenetic tree analyses. North Asia populations sampled in Mongolia include: Buryats, Mongolians, Altai Kazakhs, and Tsaatans. Available Siberians include samples of Yakut, Khanty, and Komi Zyriane. Analyses of all 122 populations confirm many known relationships and show that most populations from North Asia form a cluster distinct from all other groups. Refinement of analyses on smaller subsets of populations reinforces the distinctiveness of North Asia and shows that the North Asia cluster identifies a region that is ancestral to Native Americans.

Research progress on application of microhaplotype in forensic genetics

As a novel genetic marker, microhaplotype can be applied in the field of forensic genetics. Microhaplotype has the advantages of high polymorphism, low mutation rate, no stutter products and short amplification fragments. Microhaplotype can effectively detect mixture, and quantitatively analyze the contributors of mixture. DNA with severe fragmentation can be successfully genotyped by microhaplotype. It can be used as ancestry informative marker to effectively divide the global continental population according to genetic structure. Microhaplotype system can provide more information than traditional short tandem repeat and help to identify complex relationships. It can provide new ideas for tumor source identification, cell line identification and prenatal paternity testing. Here we review the applications of microhaplotype, intending to provide references for forensic practice.

A highly polymorphic panel of 40-plex microhaplotypes for the Chinese Han population and its application in estimating the number of contributors in DNA mixtures

Microhaplotypes (MHs) have great potential in multiple forensic applications and have proven to be promising markers in complex DNA mixture analysis. In this study, we developed a multiplex panel of 40 highly polymorphic MHs for the Chinese Han population, evaluated its forensic values, and explored its application in predicting the number of contributors (NOCs) in DNA mixtures. The panel consisted of 20 newly proposed loci and 20 previously reported loci with lengths spanning less than 120 bp. The average effective number of alleles (A_e) was 3.77, and the cumulative matching probability (CMP) and the cumulative power of exclusion (CPE) reached 1.2E-37 and 1-2.1E-12, respectively, in the Chinese Han population from the 1000 Genomes Project. Further validation on 150 Chinese Han individuals showed that A_e ranged from 2.62 to 4.41 with a mean value of 3.61, and CMP and CPE were 3.61E-36 and 1-1.84E-12, respectively, indicating that this panel was informative for personal identification and paternity testing in the studied population. To estimate NOC in DNA mixtures, we developed a machine learning model based on this panel. As a result, the accuracies in artificial DNA mixtures reached 95.24% for 2- to 4-person mixtures and 83.33% for 2- to 6-person mixtures. Furthermore, the NOC estimation on simulated profiles with allele dropout showed that this panel was still robust under slight dropout. In conclusion, this panel has value for forensic identification and NOC estimation of DNA mixtures.

Pairwise kinship testing with microhaplotypes: Can advancements be made in kinship inference with these markers?

Kinship testing based on genetic relatedness is one of the major tasks in forensic genetics. Although short tandem repeats (STRs) are the "gold standard" biomarkers for relationship testing, microhaplotypes (MHs) have also emerged as viable options for kinship elucidation. In this work, the kinship testing efficiency of 54 highly polymorphic MHs was studied in two extended families consisting of parent-offspring, full siblings, grandparent-grandchildren, uncle/aunt-nephew/nieces, and first cousins. In addition, ten-thousand pairs of different degrees of relationships were simulated using various datasets including 54 MHs, 27 STRs plus 94 single nucleotide polymorphisms (SNPs) that were included in the ForenSeq DNA Signature Prep Kit (ForenSeq), 54 MHs plus loci in ForenSeq, and different subsets of 417-published MHs. The panels' system effectiveness in the kinship analysis were accessed by likelihood ratio distributions. The results showed that 54 MHs could be used in first-degree relationship testing with high reliability. The effectiveness of 54 MHs was slightly lower than ForenSeq but only by a narrow margin. Both 54 MHs and ForenSeq were not sufficient for distant relationship testing, and approximately 200 microhaplotypes with an average expected heterozygosity (He) = 0.79 were enough to determine second-degree relationships, but a panel of 417 MHs with an average He = 0.72 was not sufficient to first cousins testing according to the simulation analysis. In conclusion, 54 MHs could be used to serve as supplement markers for kinship testing; and well-established STR markers plus well-performing microhaplotype markers may become collective tools in forensic applications, though an enlarged pool of forensic markers is needed for distant relationship testing.

Considering the flanking region variants of nonbinary SNP and phenotype-informative SNP to constitute 30 microhaplotype loci for increasing the discriminative ability of forensic applications

The flanking region variants of nonbinary SNPs and phenotype-informative SNPs (piSNPs) have been observed, which may greatly improve the discriminative ability after constituting microhaplotype. In this study, 30 microhaplotype loci based on the nonbinary SNPs and piSNPs (shown to be related to phenotypes such as hair and eye color) were selected. Genotyping were conducted on 100 unrelated northern Han Chinese, and the 26 populations from the 1000 Genome Project were also included for comparison of populations differentiation. The simulated study was conducted for evaluating the efficiency of kinship testing. These 30 microhaplotype loci we selected had good polymorphism, with a mean effective number of alleles (Ae) of 3.46. The average Ae increase was 1.27 compared with the target SNPs. The populations from the five regions worldwide could also be distinguished using these loci. The results of kinship testing showed that these microhaplotype loci had the similar ability as 15 STR loci of AmpFlSTR^R Identifiler^R PCR Amplification Kit to identify the biological parent and a stronger ability to exclude the nonbiological parents. So, these 30 microhaplotype loci may be multifunctional for forensic application, including the ability of personal identification and kinship testing equivalent to 15 STR loci, and the power of ancestry inference for distinguishing the main intercontinental population. Moreover, our selected phenotypic microhaplotype loci may theoretically have phenotype prediction capabilities. But the phenotype prediction efficiency of these phenotypic microhaplotype loci may be worse than that of piSNPs and the detailed prediction accuracy of different populations needs to be further studied.

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 Highly Polymorphic Panel Consisting of Microhaplotypes and Compound Markers with the NGS and Its Forensic Efficiency Evaluations in Chinese Two Groups

Novel genetic markers like microhaplotypes and compound markers show promising potential in forensic research. Based on previously reported single nucleotide polymorphism (SNP) and insertion/deletion (InDel) polymorphism loci, 29 genetic markers including 22 microhaplotypes and seven compound markers were identified. Genetic distributions of the 29 loci in five continental populations, Kazak and Mongolian groups in China were investigated. We found that the expected heterozygosity values of these 29 loci were >0.4 in these populations, indicating these loci were relatively high polymorphisms. Population genetic analyses of five continental populations showed that five loci displayed relatively high genetic variations among these continental populations and could be useful markers for ancestry analysis. In summary, the 29 loci displayed relatively high genetic diversities in continental populations and Chinese two groups and could be informative loci for forensic research.

Noninvasive prenatal paternity testing by target sequencing microhaps

Microhaplotypes (i.e.,microhaps or MHs) are emerging multi-allelic markers with at least two single nucleotide polymorphisms (SNPs) within ∼ 200 bp that have alleles of the same length and do not generate stutter products. Based on massively parallel sequencing (MPS) technology, microhaps have proven applicability in forensics for different application purposes. Here we evaluate the feasibility of non-invasive prenatal paternity testing (NIPPT) with a panel of polymorphic microhap markers, using cell-free DNA (cfDNA) in the maternal circulation. A custom MPS-based assay targeting 60 microhaps was developed in our previous study. Herein, we applied the developed assay to cfDNA samples in 15 NIPPT cases in the first trimester of pregnancy (6∼13 weeks). The R package relMix was employed for data interpretation, with a regression dropout estimating model. As a result, the targeted sequencing wherein target enrichment is by hybridization capture can be effectively employed for microhap sequencing with cfDNA samples. With the combined use of relMix, the paternity of the biological fathers in 15 cases was correctly determined, with the combined paternity index (CPI) value > 10¹². Moreover, the specificity of this approach was validated by the successful paternity exclusion of 3 close relatives (father, full sibling and uncle) of the biological father in one case, and further by the significant separation in CPI distribution between the biological father and 112 unrelated males in each cases. Our results indicate that this MPS-based microhap sequencing strategy could be utilized in NIPPT. This method may contribute to developments in NIPPT and to the resolution of issues related to DNA mixtures of close relatives for specific purposes.

Construction and forensic application of 20 highly polymorphic microhaplotypes

Microhaplotype markers have become an important research focus in forensic genetics. However, many reported microhaplotype markers have limited polymorphisms. In this study, we developed a set of highly polymorphic microhaplotype markers based on tri-allelic single-nucleotide polymorphisms. Eleven newly discovered microhaplotypes along with nine previously identified in our laboratory were studied. The microhaplotype genotypes of unrelated individuals and familial samples were generated on the MiSeq PE300 platform. These 20 loci have an average greater than 3.5 effective number of alleles. Over the whole set, the cumulative power of discrimination was 1-3.3 × 10^-18, the cumulative power of exclusion was 1-1.928 × 10^-7 and the theoretical probability of detecting a mixture was 1-1.427 × 10^-6. Differentiation comparisons of 26 populations from the 1000 Genomes Project distinguished among East Asian, South Asian, African and European populations. Overall, these markers enrich the current microhaplotype marker databases and can be applied for individual identification, paternity testing and biogeographic ancestry distinction.

A microhap panel for kinship analysis through massively parallel sequencing technology

It is widely recognized that microhaps are powerful markers for different forensic purposes, mainly due to their advantages of both short tandem repeats and single nucleotide polymorphisms, including multiple alleles, low mutation rate, and absence of stutter peaks. In the present study, a panel of 60 microhap loci was developed and utilized in forensic kinship analysis as a preliminary study. Genotyping of microhap was performed by massively parallel sequencing and haplotypes were directly achieved from sequence reads of 73 samples from Chinese Han population. We observed that 49 out of 60 loci have effective number of alleles greater than 3.0 and 10 out of 60 have values above 4.0, with an average value of 3.5598. The heterozygosity values were in a range from 0.5840 to 0.8546 with an average of 0.7268 and the cumulative power of exclusion value of the 60 loci is equal to 1-4.78 × 10^-18 . Moreover, we demonstrated the applicability of this method by different relationship inference problems, including identification of single parent-offspring, full-sibling, and second-degree relative. The results indicated that the assembled microhap panel provided more power for relationship inference, than commonly used short tandem repeats or single nucleotide polymorphism system.