Analysis of 21 autosomal STRs in Saudi Arabia reveals population structure and the influence of consanguinity

Variation in the 21 autosomal STRs detected by the GlobalFiler multiplex was investigated in a sample of 523 indigenous male Arabs from five geographic regions of Saudi Arabia. Although allele frequencies for the entire dataset were found to be broadly similar to those determined in previous studies of Saudi citizens, significant differences were found among regions. Heterozygote deficiency was observed at nearly all loci in all regions, probably as a consequence of high levels of consanguineous marriage; in the case of D2S1338, which showed the largest deviation from Hardy-Weinberg equilibrium, the presence of a null allele also played a part. Genetic distances were greatest between the Northern and Southern regions, whilst the West, Central and East appeared most similar to each other, and to previously published surveys. This contrasts with previously described variation among paternal lineages in the same sample-set: Y-chromosome variation was limited within the North/Central/South core compared with the more diverse East and West. Differences between autosomal and Y-chromosomal patterns may reflect genetic drift on the Y chromosome, exacerbated by prevalent patrilineal descent groups in different regions

Massively parallel sequencing of sex-chromosomal STRs in Saudi Arabia reveals patrilineage-associated sequence variants

Massively parallel sequencing (MPS) of forensic STRs has the potential to reveal additional allele diversity compared to conventional capillary electrophoresis (CE) typing strategies, but population studies are currently relatively few in number. The Verogen ForenSeq™ DNA Signature Prep Kit includes both Y-STRs and X-STRs among its targeted loci, and here we report the sequences of these loci, analysed using Verogen's ForenSeq™ Universal Analysis Software (UAS) v1.3 and STRait Razor v3.0, in a representative sample of 89 Saudi Arabian males. We identified 56 length variants (equivalent to CE alleles) and 75 repeat sequence sub-variants across the six X-STRs analysed; equivalent figures for the set of 24 Y-STRs were 147 and 192 respectively. We also observed two flanking sequence variants for the X-, and six for the Y-STRs. Recovery of sequence data and concordance with CE data (where available) across the tested loci was good, though rare flanking variation affected interpretation and allele calling at DYF387S1 and DXS7132. Examination of flanking sequences of the Y-STRs revealed five SNPs (L255, M4790, BY7692, Z16708 and S17543) previously shown to define specific haplogroups by Y-chromosome sequencing. These define Y-haplogroups in 62 % of our sample, a proportion that increases to 91 % when haplogroup-associated repeat-sequence motifs are also considered. A population-level comparison of the Saudi Arabian X-STRs with a global sample showed our dataset to be part of a large cluster of populations of West Eurasian and Middle Eastern origin

Defining cat mitogenome variation and accounting for numts via multiplex amplification and Nanopore sequencing

Hair shed by domestic cats is a potentially useful source of forensic evidence. Analysable hair DNA is predominantly mitochondrial, but the recent domestication history of cats means that mtDNA diversity is low. A 402-bp control region segment is usually sequenced, defining only a small number of distinct haplotypes in populations. Previously, we used a long-amplicon approach to sequence whole mitogenomes in a sample of blood DNAs from 119 UK cats, greatly increasing observed diversity and reducing random match probabilities. To exploit this variation for forensic analysis, we here describe a multiplex system that amplifies the cat mitogenome in 60 overlapping amplicons of mean length 360 bp, followed by Nanopore sequencing. Variants detected in multiplex sequence data from unrooted hair completely mirror those from long-amplicon data from blood from the same individuals. However, applying the multiplex to matched blood DNA reveals additional sequence variants which derive from the major feline nuclear mitochondrial insertion sequence (numt), which covers 7.9 kb of the 17-kb mitogenome and exists in multiple tandem copies. We use long-amplicon Nanopore sequencing to investigate numt variation in a set of cats, together with an analysis of published genome sequences, and show that numt arrays are variable in both structure and sequence, thus providing a potential source of uncertainty when nuclear DNA predominates in a sample. Forensic application of the multiplex was demonstrated by matching hairs from a cat with skeletal remains from its putative mother, both of which shared a globally common haplotype at the control region. The random match probability in this case with the CR 402-bp segment was 0.21 and this decreased to 0.03 when considering the whole mitogenome. The developed multiplex and sequencing approach, when applied to cat hair where nuclear DNA is scarce, can provide a reliable and highly discriminating source of forensic genetic evidence from a single hair. The confounding effect of numt co-amplification in degraded samples where mixed sequences are observed can be mitigated by variant phasing, and by comparison with numt sequence diversity data, such as those presented here.</p