Frank R. Wendt

Genetic analysis of the Yavapai Native Americans from West-Central Arizona using the Illumina MiSeq FGx™ forensic genomics system

Forensically-relevant genetic markers were typed for sixty-two Yavapai Native Americans using the ForenSeq™ DNA Signature Prep Kit.These data are invaluable to the human identity community due to the greater genetic differentiation among Native American tribes than among other subdivisions within major populations of the United States. Autosomal, X-chromosomal, and Y-chromosomal short tandem repeat (STR) and identity-informative (iSNPs), ancestry-informative (aSNPs), and phenotype-informative (pSNPs) single nucleotide polymorphism (SNP) allele frequencies are reported. Sequence-based allelic variants were observed in 13 autosomal, 3 X, and 3 Y STRs. These observations increased observed and expected heterozygosities for autosomal STRs by 0.081±0.068 and 0.073±0.063, respectively, and decreased single-locus random match probabilities by 0.051±0.043 for 13 autosomal STRs. The autosomal random match probabilities (RMPs) were 2.37×10-26 and 2.81×10-29 for length-based and sequence-based alleles, respectively. There were 22 and 25 unique Y-STR haplotypes among 26 males, generating haplotype diversities of 0.95 and 0.96, for length-based and sequencebased alleles, respectively. Of the 26 haplotypes generated, 17 were assigned to haplogroup Q, three to haplogroup R1b, two each to haplogroups E1b1b and L, and one each to haplogroups R1a and I1. Male and female sequence-based X-STR random match probabilities were 3.28×10-7 and 1.22×10-6, respectively. The average observed and expected heterozygosities for 94 iSNPs were 0.39±0.12 and 0.39±0.13, respectively, and the combined iSNP RMP was 1.08×10-32. The combined STR and iSNP RMPs were 2.55×10-58 and 3.02×10-61 for length-based and sequence-based STR alleles, respectively. Ancestry and phenotypic SNP information, performed using the ForenSeq™ Universal Analysis Software, predicted black hair, brown eyes, and some probability of East Asian ancestry for all but one sample that clustered between European and Admixed American ancestry on a principal components analysis. These data serve as the first population assessment using the ForenSeq™ panel and highlight the value of employing sequence-based alleles for forensic DNA typing to increase heterozygosity, which is beneficial for identity testing in populations with reduced genetic diversity.

Increasing the reference populations for the 55 AISNP panel: the need and benefits

Ancestry inference for an individual can only be as good as the reference populations with allele frequency data on the SNPs being used. If the most relevant ancestral population(s) does not have data available for the SNPs studied, then analyses based on DNA evidence may indicate a quite distantly related population, albeit one among the more closely related of the existing reference populations. We have added reference population allele frequencies for 14 additional population samples (with >1100 individuals studied) to the 125 population samples previously published for the Kidd Lab 55 AISNP panel. Allele frequencies are now publicly available for all 55 SNPs in ALFRED and FROG-kb for a total of 139 population samples. This Kidd Lab panel of 55 ancestry informative SNPs has been incorporated in commercial kits by both ThermoFisher Scientific and Illumina for massively parallel sequencing. Researchers employing those kits will find the enhanced set of reference populations useful.

Flanking region variation of ForenSeq™ DNA Signature Prep Kit STR and SNP loci in Yavapai Native Americans

Massively parallel sequencing (MPS) offers advantages over current capillary electrophoresis-based analysis of short tandem repeat (STR) loci for human identification testing. In particular STR repeat motif sequence information can be obtained, thereby increasing the discrimination power of some loci. While sequence variation within the repeat region is observed relatively frequently in some of the commonly used STRs, there is an additional degree of variation found in the flanking regions adjacent to the repeat motif. Repeat motif and flanking region sequence variation have been described for major population groups, however, not for more isolated populations. Flanking region sequence variation in STR and single nucleotide polymorphism (SNP) loci in the Yavapai population was analyzed using the ForenSeq™ DNA Signature Prep Kit and STRait Razor v2s. Seven and 14 autosomal STRs and identity-informative single nucleotide polymorphisms (iiSNPs), respectively, had some degree of flanking region variation. Three and four of these identity-informative loci, respectively, showed ≥5% increase in expected heterozygosity. The combined length- and sequence-based random match probabilities (RMPs) for 27 autosomal STRs were 6.11×10-26 and 2.79×10-29, respectively. When combined with 94 iiSNPs (a subset of which became microhaplotypes) the combined RMP was 5.49×10-63. Analysis of length-based and sequence-based autosomal STRs in STRUCTURE indicated that the Yavapai are most similar to the Hispanic population. While producing minimal increase in X- and Y-STR discrimination potential, access to flanking region data enabled identification of one novel X-STR and three Y-STR alleles relative to previous reports. Five ancestry-informative SNPs (aiSNPs) and two phenotype-informative SNPs (piSNPs) exhibited notable flanking region variation.

Massively parallel sequencing of 68 insertion/deletion markers identifies novel microhaplotypes for utility in human identity testing

Short tandem repeat (STR) loci are the traditional markers used for kinship, missing persons, and direct comparison human identity testing. These markers hold considerable value due to their highly polymorphic nature, amplicon size, and ability to be multiplexed. However, many STRs are still too large for use in analysis of highly degraded DNA. Small bi-allelic polymorphisms, such as insertions/deletions (INDELs), may be better suited for analyzing compromised samples, and their allele size differences are amenable to analysis by capillary electrophoresis. The INDEL marker allelic states range in size from 2 to 6 base pairs, enabling small amplicon size. In addition, heterozygote balance may be increased by minimizing preferential amplification of the smaller allele, as is more common with STR markers. Multiplexing a large number of INDELs allows for generating panels with high discrimination power. The Nextera™ Rapid Capture Custom Enrichment Kit (Illumina, Inc., San Diego, CA) and massively parallel sequencing (MPS) on the Illumina MiSeq were used to sequence 68 well-characterized INDELs in four major US population groups. In addition, the STR Allele Identification Tool: Razor (STRait Razor) was used in a novel way to analyze INDEL sequences and detect adjacent single nucleotide polymorphisms (SNPs) and other polymorphisms. This application enabled the discovery of unique allelic variants, which increased the discrimination power and decreased the single-locus random match probabilities (RMPs) of 22 of these well-characterized INDELs which can be considered as microhaplotypes. These findings suggest that additional microhaplotypes containing human identification (HID) INDELs may exist elsewhere in the genome.

Analysis of Short Tandem Repeat and Single Nucleotide Polymorphism Loci From Single-Source Samples Using a Custom HaloPlex Target Enrichment System Panel.

AbstractShort tandem repeats and single nucleotide polymorphisms (SNPs) are used to individualize biological evidence samples. Short tandem repeat alleles are characterized by size separation during capillary electrophoresis (CE). Massively parallel sequencing (MPS) offers an alternative that can overcome limitations of the CE. With MPS, libraries are prepared for each sample, entailing target enrichment and bar coding, purification, and normalization. The HaloPlex Target Enrichment System (Agilent Technologies) uses a capture-based enrichment system with restriction enzyme digestion to generate fragments containing custom-selected markers. It offers another possible workflow for typing reference samples. Its efficacy was assessed using a panel of 275 human identity SNPs, 88 short tandem repeats, and amelogenin. The data analyzed included locus typing success, depth of sequence coverage, heterozygote balance, and concordance. The results indicate that the HaloPlex Target Enrichment System provides genetic data similar to that obtained by conventional polymerase chain reaction-CE methods with the advantage of analyzing substantially more markers in 1 sequencing run. The genetic typing performance of HaloPlex is comparable to other MPS-based sample preparation systems that utilize primer-based target enrichment.

Increasing the reach of forensic genetics with massively parallel sequencing

The field of forensic genetics has made great strides in the analysis of biological evidence related to criminal and civil matters. More so, the discipline has set a standard of performance and quality in the forensic sciences. The advent of massively parallel sequencing will allow the field to expand its capabilities substantially. This review describes the salient features of massively parallel sequencing and how it can impact forensic genetics. The features of this technology offer increased number and types of genetic markers that can be analyzed, higher throughput of samples, and the capability of targeting different organisms, all by one unifying methodology. While there are many applications, three are described where massively parallel sequencing will have immediate impact: molecular autopsy, microbial forensics and differentiation of monozygotic twins. The intent of this review is to expose the forensic science community to the potential enhancements that have or are soon to arrive and demonstrate the continued expansion the field of forensic genetics and its service in the investigation of legal matters.

Global genetic variation of select opiate metabolism genes in self-reported healthy individuals

CYP2D6 is a key pharmacogene encoding an enzyme impacting poor, intermediate, extensive and ultrarapid phase I metabolism of many marketed drugs. The pharmacogenetics of opiate drug metabolism is particularly interesting due to the relatively high incidence of addiction and overdose. Recently, trans-acting opiate metabolism and analgesic response enzymes (UGT2B7, ABCB1, OPRM1 and COMT) have been incorporated into pharmacogenetic studies to generate more comprehensive metabolic profiles of patients. With use of massively parallel sequencing, it is possible to identify additional polymorphisms that fine tune, or redefine, previous pharmacogenetic findings, which typically rely on targeted approaches. The 1000 Genomes Project data were analyzed to describe population genetic variation and statistics for these five genes in self-reported healthy individuals in five global super- and 26 sub-populations. Findings on the variation of these genes in various populations expand baseline understanding of pharmacogenetically relevant polymorphisms for future studies of affected cohorts.

Full-gene haplotypes refine CYP2D6 metabolizer phenotype inferences

CYP2D6 is a critical pharmacogenetic target, and polymorphisms in the gene region are commonly used to infer enzyme activity score and predict resulting metabolizer phenotype: poor, intermediate, extensive/normal, or ultrarapid which can be useful in determining cause and/or manner of death in some autopsies. Current genotyping approaches are incapable of identifying novel and/or rare variants, so CYP2D6 star allele definitions are limited to polymorphisms known a priori. While useful for most predictions, recent studies using massively parallel sequencing data have identified additional polymorphisms in CYP2D6 that are predicted to alter enzyme function but are not considered in current star allele nomenclature. The 1000 Genomes Project data were used to produce full-gene haplotypes, describe their distribution in super-populations, and predict enzyme activity scores. Full-gene haplotypes generated lower activity scores than current approaches due to inclusion of additional damaging polymorphisms in the star allele. These findings are critical for clinical implementation of metabolizer phenotype prediction because a fraction of the population may be incorrectly considered normal metabolizers but actually may be poor or intermediate metabolizers.

Targeted sequencing of clade-specific markers from skin microbiomes for forensic human identification

The human skin microbiome is comprised of diverse communities of bacterial, eukaryotic, and viral taxa and contributes millions of additional genes to the repertoire of human genes, affecting human metabolism and immune response. Numerous genetic and environmental factors influence the microbiome composition and as such contribute to individual-specific microbial signatures which may be exploited for forensic applications. Previous studies have demonstrated the potential to associate skin microbial profiles collected from touched items to their individual owner, mainly using unsupervised methods from samples collected over short time intervals. Those studies utilize either targeted 16S rRNA or shotgun metagenomic sequencing to characterize skin microbiomes; however, these approaches have limited species and strain resolution and susceptibility to stochastic effects, respectively. Clade-specific markers from the skin microbiome, using supervised learning, can predict individual identity using skin microbiomes from their respective donors with high accuracy. In this study the hidSkinPlex is presented, a novel targeted sequencing method using skin microbiome markers developed for human identification. The hidSkinPlex (comprised of 286 bacterial (and phage) family-, genus-, species-, and subspecies-level markers), initially was evaluated on three bacterial control samples represented in the panel (i.e., Propionibacterium acnes, Propionibacterium granulosum, and Rothia dentocariosa) to assess the performance of the multiplex. The hidSkinPlex was further evaluated for prediction purposes. The hidSkinPlex markers were used to attribute skin microbiomes collected from eight individuals from three body sites (i.e., foot (Fb), hand (Hp) and manubrium (Mb)) to their host donor. Supervised learning, specifically regularized multinomial logistic regression and 1-nearest-neighbor classification were used to classify skin microbiomes to their hosts with up to 92% (Fb), 96% (Mb), and 100% (Hp) accuracy. All samples (n=72) regardless of body site origin were correctly classified with up to 94% accuracy, and body site origin could be predicted with up to 86% accuracy. Finally, human short tandem repeat and single-nucleotide polymorphism profiles were generated from skin swab extracts from a single subject to highlight the potential to use microbiome profiling in conjunction with low-biomass samples. The hidSkinPlex is a novel targeted enrichment approach to profile skin microbiomes for human forensic identification purposes and provides a method to further characterize the utility of skin microflora for human identification in future studies, such as the stability and diversity of the personal skin microbiome.

Exploring the 1000 Genomes Project haplotype reporting for the CYP2D6 pharmacogene

The Gaedigk et al. article BA perspective by PharmVar: Are the hundreds of CYP2D6 haplotypes predicted by Wendt and colleagues real?^ describes shortcomings of the 2017 Wendt et al. article BFull-gene haplotypes refine CYP2D6 metabolizer phenotype inferences^ [1]. To summarize, they discuss (1) the lack of submission of novel variants to www. PharmVar.org; (2) inaccurate activity score reporting, namely for those haplotypes containing the 843T>G SNP; (3) use of 1000 Genomes Project (1kGP) data from the inaccessible regions of the database; and (4) lack of sequence and structural validation for any of the described haplotypes. We thank Gaedigk and colleagues for their review of the Wendt et al. 2017 findings and in many ways share their concerns. In general, the authors’ letter raises valid concerns for the data presented in the original Wendt et al. study and many pharmacogenomics studies utilizing publically available data. However, the authors’ appear to overstate our reported findings and seem to ignore where we already transparently discuss the major limitations of using such a database for this type of data exploration. We summarize our responses to their concerns below. In general, we urge PharmVar to actively update its nomenclature table as to reflect most recent submitted findings. Additionally, we encourage PharmVar, its affiliates, and other pharmacogenomics researchers to release full-gene information as it becomes available, rather than only those sites relevant to the PharmVar nomenclature table(s) or the repository of knowledge for their respective gene(s) of interest. In doing so, the initiative described by Gaedigk and colleagues will continue to thrive. The Wendt et al. paper was intended to explore the use of full-gene CYP2D6 haplotype diversity in publically available data. A number of single-nucleotide polymorphisms from the 1kGP and the Wendt et al. study are not found on www. PharmVar.com. Gaedigk and colleagues note that PharmVar accepts submission of high-quality haplotype data. The Pilot Criteria of the 1kGP Phase3 Paired-end Accessible Regions are quite stringent, requiring Ba depth of coverage between 8,960 and 35,840 inclusive (between one-half and twice the average depth) and that no more than 20% of covering reads have mapping quality zero^ [2]. Indeed, read depth is a limiting factor for using data such as those of the 1kGP; however, Wendt et al. never recommended or even suggested that the data were high quality and be considered for submission to PharmVar. Such a recommendation would have been inappropriate and misleading to the community. Indeed, we stress in our paper that Bempirical data are required to confirm their enzyme activity [of the resulting haplotypes]^ and thus share similar concerns. Wendt et al. indicated that the relatively low sequencing read depth of the 1kGP is a major limitation of their findings. However, low read depth of pharmacoand immunogenes does not warrant ignoring the public availability of 1kGP short-read data for exploratory purposes. It is a great resource used by many scientists for developing hypotheses and addressing probing questions. There appears to be some confusion by Gaedigk et al. regarding the methods ofWendt et al. in which 1kGP haplotypes were characterized first using only those sites recognized and published on the PharmVar website (Human Cytochrome p450 Allele Nomenclature Database at the time of Wendt et al. analyses). Here, the consortium defines CYP2D6 * Frank R. Wendt frw5010@gmail.com