Concordance and characterization of massively parallel sequencing at 58 STRs in a Tibetan population

Abstract

Background: Massively parallel sequencing (MPS) is a promising supplementary method for forensic casework in short tandem repeats (STRs) genotyping, owing to several advantageous features in comparison to traditional capillary electrophoresis (CE). However, the application of MPS in casework requires accessible datasets from the worldwide population to enrich the allele frequencies of sequence-based STR genotypes. Methods: In this study, we report the characterization of sequence-based allele frequencies of 58 STRs from a Tibetan population comprising 120 unrelated individuals using the ForenSeq™ DNA Signature Prep Kit. A concordance study evaluating MPS and CE allele data was performed to ensure that MPS is compatible with current CE-based forensic databases. The diversity of observed alleles, allele frequencies, and forensic parameters per locus by length (LB), sequence without flanking region (RSB), and sequence with flanking region (FSB) were analyzed and compared. Results: The concordance study demonstrated a concordance rate exceeding 99%. The combined random match probability (RMP) for the 26 A-STRs was 2.04 × 10–29, 1.93 × 10–31, and 9.56 × 10–33 for LB, RSB, and FSB, respectively. Similar trends were observed in other forensic parameters resulting from the increase in the number of unique alleles available. A total of 111 and 113 unique haplotypes in the Y-STR loci were observed when using length-based and sequence-based alleles, respectively. In addition, we identified 35 novel alleles at 25 loci and 25 polymorphisms in the flanking regions at 17 STRs. Conclusions: Our data suggest that MPS- and CE-derived alleles are compatible. MPS-based analysis of the STR data substantially increased the allele diversity and improved the forensic parameters, which clearly demonstrated the advantages of MPS in comparison to CE. With more pooled data and larger-scale validation, MPS could play a valuable role in forensic genetics and might be an additional tool for routine casework.