Forensic data and microvariant sequence characterization of 27 Y-STR loci analyzed in four Eastern African countries

By using the recently introduced 6-dye Yfiler^® Plus multiplex, we analyzed 462 males belonging to 20 ethnic groups from four eastern African countries (Eritrea, Ethiopia, Djibouti and Kenya). Through a Y-STR sequence analysis, combined with 62 SNP-based haplogroup information, we were able to classify observed microvariant alleles at four Y-STR loci as either monophyletic (DYF387S1 and DYS458) or recurrent (DYS449 and DYS627). We found evidence of non-allelic gene conversion among paralogous STRs of the two-copy locus DYF387S1. Twenty-two diallelic and triallelic patterns observed at 13 different loci were found to be significantly over-represented (p<10^-6) among profiles obtained from cell lines compared to those from blood and saliva. Most of the diallelic/triallelic patterns from cell lines involved recurrent mutations at rapidly mutating loci (RM Y-STRs) included in the multiplex (p<10^-2). At haplotype level, intra-population diversity indices were found to be among the lowest so far reported for the Yfiler^® Plus, while statistically significant differences among countries and ethnic groups were detected when considering haplotype frequencies alone (F_ST) or by using molecular distances among haplotypes (Φ_ST). The strong population subdivision observed is probably the consequence of the patrilineal social organization of most eastern African ethnic groups, and suggests caution in the use of country-based haplotype frequency distributions for forensic inferences in this region.