Forensic parameters and admixture in Mestizos from five geographic regions of Mexico based on 20 autosomal STRs (Powerplex 21 system)

Abstract

We analyzed Mestizo (admixed) population samples from different geographic regions of Mexico (n = 1283) with 20 autosomal STRs (PowerPlex® 21, Promega Corp.). Allele frequencies and forensic parameters from the Northwest, Northeast, West, Center, and Southeast regions are reported, as well as from the pooled Mexican population sample. The combined PD and PE for this 20 STR system were > 0.9999999999 and > 0.99999996593% in all five population samples, respectively. Analysis of molecular variance (AMOVA) of these Mexican population samples, plus Monterrey (Northeast) and Mexico (Center) Cities, showed low but significant differences among Mexican-Mestizos from the seven populations (Fst = 0.20%; p = 0.0000). Structure analysis showed the highest proportion of Native American ancestry in Mexico City, Center, and Southeast regions, respectively, which was in agreement with the estimated genetic distances represented in a MDS plot and a NJ tree. The best fit of population clusters (K = 4) obtained with the Structure software indicates that Mexican-Mestizos are mainly composed by European, African, and two Native American ancestries. The European and Native American ancestries displayed a contrary gradient, increasing toward the North-West and South-Southeast, respectively. These 20 autosomal STR loci improved the admixture estimation regarding previous studies with the 13 CODIS-STRs, as supported by the higher similarity with previous estimates based on genome-wide SNP. In brief, this study validates the confident use of the PowerPlex® 21 system for human identification purposes in Mestizo populations throughout the Mexican territory.

Ancestral proportions based on 22 autosomal STRs of an admixed population (Mestizos) from the Península of Yucatán, México

“…1b), suggests that the studied population of the Southeast is mainly composed by NA ancestry (64.9%), and lesser proportion by European (33.7%) and African (1.3%) ancestries. Interestingly, the similar ancestral proportion pattern was observed in a previous report based on the 13 CODIS-STRs (NA = 63.6%; European = 34.2%) [2], but showed differences with the study based on 20 STRs (NA = 55.5%; European = 42.4%) for the same Southeast region [3]. These differences could be explained by socioeconomic and educational factors of the population sample by intrapopulation structure, as has been described in Mexican-Mestizo populations [13].…”

“…Although a northwest-southeast genetic cline is evident (Fig. 1b), the ancestral distribution among the Mexican populations showed higher similarity between the Center and Southeast regions, respect to the West and Northeast regions, as previously noted [2,3]. Despite the small number of Mexican-Mestizo populations used herein, the distribution of NA ancestry roughly reflects the Pre-Hispanic NA demography, particularly toward the Mesoamerican area [13].…”

“…Hardy-Weinberg equilibrium (HWE) and linkage disequilibrium (LD) were evaluated with the Arlequin v3.5 software [4]. Admixture analysis was performed by means of a supervised analysis with the Structure software [5] using the following ancestral references: African-Americans, European-Americans [6] and a NA pool from Mexico [3]. In addition, the following admixed populations were included: Hispanic-Americans [6], Monterrey City (Northeast, Mexico) [7], West region of Mexico [8], and Mexico City (Center) [9].…”

“…However, STR population datasets are also useful to analyze anthropological issues, such as structure, relationships and admixture of human populations. Although Mexican populations have been widely analyzed with autosomal STRs [2], the emergence and development of new genetic systems makes necessary to re-analyze many of these populations [3]. Consequently, the aim of this study is to explore the ancestral proportions in Mestizos of the Peninsula of Yucatan based on the 22 STRs included in the Powerplex Fusion® System.…”

Predicting Pathogenicity of CDH1 Gene Variants in Patients with Early-onset Diffuse Gastric Cancer from Western Mexico

“…The admixture analysis based on STR genotype was performed with Structure 14,15 . For this purpose, STR population databases that included Mexican Native Americans 16 , as well as Europeans and Africans from the USA, were employed as ancestral references 17 . The structure parameters employed herein offered consistent admixture estimates regarding those based on AIMs and genome-wide SNPs, as previously demonstrated in Mexican populations 18 .…”