Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Rome, Italy.
Reparto Carabinieri Investigazioni Scientifiche di Roma - Sezione di Biologia, Viale Tor di Quinto 119, 00191, Rome, Italy.
Forensic Sci Int Genet. 2020 Nov;49:102374. doi: 10.1016/j.fsigen.2020.102374. Epub 2020 Aug 21.
Y chromosome short tandem repeats (Y-STRs) are commonly used to identify male lineages for investigative and judicial purposes and could represent the only source of male-specific genetic information from unbalanced female-male mixtures. The Yfiler Plus multiplex, which includes twenty conventional and seven rapidly-mutating Y-STRs, represents the most discriminating patrilineal system commercially available to date. Over the past five years, this multiplex has been used to analyze several Eurasian populations, with a reported discrimination capacity (DC) approaching or corresponding to the highest possible value. However, despite the inclusion of rapidly mutating Y-STRs, extensive haplotype sharing was still reported for some African populations due to a number of different factors affecting the effective population size. In the present study, we analyzed 27 Y-STRs included in the Yfiler Plus multiplex and 82 Y-SNPs in central Sahel (northern Cameroon and western Chad), an African region characterized by a strong ethnic fragmentation and linguistic diversity. We evaluated the effects of population sub-structuring on genetic diversity by stratifying a sample composed of 431 males according to their ethnicity (44 different ethnic groups) and urbanization degree (four villages and four towns). Overall, we observed a low discrimination capacity (DC = 0.90), with 71 subjects (16.5 %) sharing 27 Y-STR haplotypes. Haplotype sharing was essentially limited to subjects with the same binary haplogroup, coming from the same location and belonging to the same ethnic group. Haplotype sharing was much higher in rural areas (average DC = 0.83) than urban settlements (average DC = 0.96) with a significant correlation between DC and census size (r = 0.89; p = 0.003). Notably, we found that genetic differentiation between villages from the same country (Φ = 0.14) largely exceeded that found among countries (Φ = 0.02). These findings have important implications for the choice of the appropriate reference population database to evaluate the statistical relevance of forensic Y-haplotype matches.
Y 染色体短串联重复序列（Y-STR）常用于鉴定男性谱系，以满足调查和司法目的，并且可能是不平衡的男女混合物中唯一的男性特异性遗传信息来源。Yfiler Plus 多重扩增试剂盒包含 20 个常规和 7 个快速突变的 Y-STR，是目前商业上可获得的最具鉴别力的父系系统。在过去的五年中，该多重扩增试剂盒已用于分析多个欧亚人群，其报告的分辨能力（DC）接近或对应于可能的最高值。然而，尽管包含快速突变的 Y-STR，但由于影响有效种群大小的许多不同因素，一些非洲人群仍然报告了广泛的单倍型共享。在本研究中，我们分析了 Yfiler Plus 多重扩增试剂盒中包含的 27 个 Y-STR 和中非萨赫勒地区（喀麦隆北部和乍得西部）的 82 个 Y-SNP，该非洲地区以强烈的族群分裂和语言多样性为特征。我们通过根据族群（44 个不同族群）和城市化程度（四个村庄和四个城镇）对由 431 名男性组成的样本进行分层，评估了人口亚结构对遗传多样性的影响。总体而言，我们观察到较低的分辨能力（DC=0.90），71 名受试者（16.5%）共享 27 个 Y-STR 单倍型。单倍型共享主要限于具有相同二元单倍群的受试者，来自同一地点，属于同一族群。在农村地区（平均 DC=0.83）的单倍型共享率高于城市定居点（平均 DC=0.96），且 DC 与人口普查规模之间存在显著相关性（r=0.89；p=0.003）。值得注意的是，我们发现来自同一国家的村庄之间的遗传分化（Φ=0.14）大大超过了国家之间的遗传分化（Φ=0.02）。这些发现对于选择适当的参考人群数据库来评估法医 Y-单倍型匹配的统计相关性具有重要意义。
