LOW DISCRIMINATION POWER OF THE YFILERTM PLUS PCR AMPLIFICATION KIT IN AFRICAN POPULATIONS. DO WE NEED MORE RM Y-STRs?

Abstract Recently, thirteen rapidly mutating Y-STRs (RM Y-STRs), characterized by a mutation rate higher than 10-2/STR/generation, have been proven to be extremely useful in distinguishing among close male relatives. Six of these RM-YSTRs have been included in the YfilerTM Plus PCR Amplification Kit, which shows the highest discriminatory power among Y-STR commercial multiplex currently available. In this study, we used Yfiler Plus to analyze 1,437 males from eastern, northern and sub-Saharan Africa (462, 477 and 498 subjects, respectively). 242 out of 1,437 subjects were found to share 102 Y-STR haplotypes, resulting in a low discrimination capacity (DC = 0.90) as compared to other continental regions. With few exceptions, Y-STR haplotype sharing was limited to subjects coming from the same country and ethnic group, and belonging to the same binary Y-SNP haplogroup, suggesting possible familial relationships along the male lineage. In order to evaluate the presence of hidden familial relationships, all the 242 subjects sharing a Y-STR haplotype were further genotyped for 16 autosomal STRs using the AmpFlSTR® NGM SElect™ PCR Amplification Kit. Blind search and simulation test analyses for kinship using the Familias software revealed the presence of a low proportion of close relatives (second degree or closer) in our sample set. These findings show that close relatedness explains only a relatively small proportion of the observed Y-STR haplotype sharing, suggesting that a higher number of RM Y-STRs should be included in commercial kits to improve the discrimination power of male-specific markers in regions characterized by high levels of endogamy.