Massively parallel sequence data of 31 autosomal STR loci from 496 Spanish individuals revealed concordance with CE-STR technology and enhanced discrimination power.

This study reports Short Tandem Repeat (STR) sequence-based allele data from 496 Spanish individuals across 31 autosomal STR (auSTR) loci included in the Precision ID GlobalFiler™ NGS STR Panel v2: D12S391, D13S317, D8S1179, D21S11, D3S1358, D5S818, D1S1656, D2S1338, vWA, D2S441, D5S2800, D7S820, D16S539, D6S474, D12ATA63, D4S2408, D6S1043, D19S433, D14S1434, CSF1PO, D10S1248, D18S51, D1S1677, D22S1045, D2S1776, D3S4529, FGA, Penta D, Penta E, TH01 and TPOX. The sequence of each allele was aligned to the reference sequence GRCh37 (hg19) and formatted according to the guidance of the International Society for Forensic Genetics. A subset of 221 samples was evaluated for testing concordance with allele calls derived from CE-based analysis using PowerPlex Fusion 6C, and there was 99.95% allele concordance. Twenty-five out of 31 auSTR loci showed an increased number of alleles due to repeat region sequence variation and/or single nucleotide polymorphisms (SNP) residing in the flanking regions. A total of 18 loci showed increased observed heterozygosity due to sequence variation; the loci exhibiting the greatest increase were: D13S317 (12% points), D5S818 (10% points), D8S1179 (7% points), D3S1358 (7% points), and D21S11 (6% points). The combined match probability decreased from 2.022E-24 (length-based data) to 1.042E-27 (sequence-based data) for the 20 CODIS core STR loci. The combined match probability (sequence-based data) for the 31 STR loci studied was 4.777E-40. The combined typical paternity index increased from 1.118E + 12 to 8.179E + 13 using length and sequence-based data, respectively. This Spanish population study performed in the framework of the EU-funded DNASEQEX project is expected to provide STR sequence-based allele frequencies for forensic casework and support implementation of massively parallel sequencing (MPS) technology in forensic laboratories.