Paternity testing using massively parallel sequencing and the PowerSeq™ AUTO/Y system for short tandem repeat sequencing

Analysis of homozygous allele mismatches in paternity tests with massively parallel sequencing

In paternity testing, short tandem repeats (STRs) allele mismatches are often detected. Nowadays, polymerase chain reaction- and capillary electrophoresis (CE)-based STR genotyping is the most commonly used method to distinguish alleles based on their length. However, it could not detect alleles of the same size with sequence differences. Massively parallel sequencing (MPS) can determine not only allele sizes but also sequences, which could explain the causes of allele mismatches. Additionally, more types of genetic markers can be detected in a single assay, which increases the discriminatory power and facilitates the analysis of paternity tests. In this study, we analyzed 11 cases with homozygous allele mismatches from routine DNA trio paternity tests using the CE platform. Samples were sequenced using the ForenSeq DNA Signature Prep Kit and the MiSeq FGx Sequencing System. The results show that of the eight father-child mismatch cases and three mother-child mismatch cases, five cases with D5S818 and D8S1179 and one case at D13S317 were classified as non-amplification. The other three cases and two cases could be defined as mutations. This study suggests that MPS-based STR genotyping can provide additional information that allows more accurate interpretation of allelic mismatches in paternity testing.

Concordance study on Y-STRs typing between SeqStudio™ genetic analyzer for HID and MiSeq™ FGx forensic genomics system

BACKGROUND

Massively Parallel Sequencing (MPS) allowed an increased number of information to be retrieved from short tandem repeat (STR) analysis, expanding them not only to the size, as already performed in Capillary Electrophoresis (CE), but also to the sequence. MPS requires constant development and validation of the analytical parameters to ensure that the genotyping results of STRs correspond to those obtained by CE. Given the increased frequency of usage of Y-STRs as supplementary markers to the autosomal STRs analysis, it is urgent to validate the concordance of the typing results between CE and MPS analyses.

METHODS AND RESULTS

DNA extracted from 125 saliva samples of unrelated males was genotyped using Yfiler™ Plus PCR Amplification Kit and ForenSeq™ DNA Signature Prep Kit, which were analyzed by SeqStudio™ Genetic Analyzer for HID and MiSeq™ FGx Forensic Genomics System, respectively. For each shared Y-STR, allele designation, number of length- and sequence-based alleles per locus, stutter percentage, and the intra-locus balance of multicopy Y-STRs were screened.

CONCLUSIONS

Although the number of forensic genetics laboratories that are applying the MPS technique in routine analysis is small and does not allow a global assessment of MPS limitations, this comparative study highlights the ability of MPS to produce reliable profiles despite the generation of large amounts of raw data.

Sequence-based allelic variations and frequencies for 22 autosomal STR loci in the Lebanese population

This is the first study that characterizes the sequence-based allelic variations of 22 autosomal Short Tandem Repeat (aSTR) loci in a population dataset collected from Lebanon. Genomic DNA extracts from 195 unrelated Lebanese individuals were amplified with PowerSeq 46GY System Prototype. Targeted amplicons were subjected to DNA library preparation and sequenced on the Verogen MiSeq FGx Sequencing System. Raw FASTQ data files were processed by STRait Razor v3. Sequence strings were annotated according to the considerations of the DNA Commission of the International Society for Forensic Genetics (ISFG) and tabulated herein with their respective allelic frequencies and GeneBank accession and version numbers. The sequenced Lebanese dataset resulted in 429 distinct allelic sequences as compared to the 236 alleles identified by length only. The increase in the number of alleles was observed at 18 out of 22 aSTR loci and was attributed to the sequence variations residing in both the STR repeat motifs and flanking regions. The study uncovered 25 novel aSTR allelic sequences across 12 loci for which GenBank records did not previously exist in the STRSeq BioProject, PRJNA380127. For a concordance check, the length-based allelic calls derived from the full sequences were compared to those genotyped using capillary electrophoresis (CE) methods. Population genetic parameters relevant to the evaluation of forensic DNA evidence were assessed for the sequence-based data and compared to the parameters generated from the length-based information. Using the sequence-based data, Analysis of MOlecular VAriance (AMOVA), genetic distances, and population genetic structure were evaluated for 1231 individuals sampled from the Lebanese and four U.S. populations (African American, Asian, Caucasian, and Hispanic). The results were tabulated and visualized in a population tree, multidimensional scaling scatter plots, and bar plots. This newly established sequence-based database for the Lebanese population can be beneficial for extending NGS applicability to casework or paternity testing and assessing the strength of evidence for NGS-STR profiles. The described novel sequence variants at certain loci can further help in the effort to characterize the sequence diversity of STR markers from different populations around the world.

Investigation on the genetic-inconsistent paternity cases using the MiSeq FGx system

Mutations might challenge the paternity index calculation in forensic identification. While many studies have focussed on the autosomal short tandem repeats (A-STR), the mutation status of sex chromosomes and single nucleotide polymorphism (SNP) remain blank. Next generation sequencing (NGS), known as high throughput and large sequence polymorphism, is a promising tool for forensic genetics. To describe the mutation landscapes in the paternity cases with genetic inconsistencies, a total of 63 parentage confirmed paternity cases contained at least one mismatched locus have been collected. The mutations were subsequently evaluated using Verogen's MPS ForenSeq^TM DNA Signature Kit and a microsatellite instability (MSI) detection kit. The result showed 98.41% (62/63) of the cases had no additional autosomal mutations even when the number of A-STRs increased to 27. As for the sex chromosomes, about 11.11% (7/63) of the cases exhibited either X-STR or Y-STR mutations. D2S1338, FGA and Penta E were the most frequent altered STRs, which suggested they might be the mutation hotspots. In addition, a male with sex chromosome abnormality was observed accidently, whose genotype might be 47, XXY, rather than MSI. Nearly 56.90% of the STR loci possessed isoalleles, which might result in higher STR polymorphisms. No Mendelian incompatibility was detected among the SNP markers, which indicated that SNP was a more reliable genetic marker in the genetic-inconsistent paternity cases. Supplemental data for this article is available online at https://doi.org/10.1080/20961790.2021.2009631 .

Massively parallel sequencing of 25 autosomal STRs including SE33 in four population groups for forensic applications

The introduction of massively parallel sequencing (MPS) in forensic investigation enables sequence-based large-scale multiplexing beyond size-based analysis using capillary electrophoresis (CE). For the practical application of MPS to forensic casework, many population studies have provided sequence data for autosomal short tandem repeats (STRs). However, SE33, a highly polymorphic STR marker, has little sequence-based data because of difficulties in analysis. In this study, 25 autosomal STRs were analyzed, including SE33, using an in-house MPS panel for 350 samples from four populations (African-American, Caucasian, Hispanic, and Korean). The barcoded MPS library was generated using a two-step PCR method and sequenced using a MiSeq System. As a result, 99.88% genotype concordance was obtained between length- and sequence-based analyses. In SE33, the most discordances (eight samples, 0.08%) were observed because of the 4 bp deletion between the CE and MPS primer binding sites. Compared with the length-based CE method, the number of alleles increased from 332 to 725 (2.18-fold) for 25 autosomal STRs in the sequence-based MPS method. Notably, additional 129 unique alleles, a 4.15-fold increase, were detected in SE33 by identifying sequence variations. This population data set provides sequence variations and sequence-based allele frequencies for 25 autosomal STRs.

Interpol review of forensic biology and forensic DNA typing 2016-2019

This review paper covers the forensic-relevant literature in biological sciences from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.