Distribution of genetic variants of oxidative stress metabolism genes: Paraoxonase 1 (PON1) and Glutathione S-transferase (GSTM1/GSTT1) in a population from Southeastern Mexico.

BACKGROUND: Paraoxonase 1 (PON1) and glutathione S-transferases (GSTs) are involved in the biotransformation of xenobiotics. Variation in the enzyme concentration and activity suggests individual differences for the degree of protection against oxidative stress. AIM: This study analysed the distribution of SNPs Q192R, L55M (PON1) and variants in GSTM1 and GSTT1 genes in a population from Southeastern Mexico. SUBJECTS AND METHODS: One hundred and fifty-one Mexican Mestizo healthy volunteers were included. PON1 polymorphisms were determined by Taqman allele discrimination real time-PCR, whereas GSTM1 and GSTT1 genes were determined with a multiplex PCR-based method. RESULTS: All genotypes were in Hardy-Weinberg equilibrium, except for GSTM1. The genotypic distributions of Q192R and L55M were 22% QQ, 48% QR, 30% RR, 62% LL, 34% LM and 4% MM, respectively, whereas the allele frequencies were 0.46 (Q), 0.54 (R), 0.79 (L) and 0.21 (M). The most frequent haplotype was R/L (46.7%). It was found that 31% and 9% of the individuals had the GSTM1 and GSTT1 null genotype, respectively. The frequency of the combined null genotype GSTM1*0/GSTT1*0 was 4.64%. CONCLUSION: The results showed that the frequencies of polymorphisms of PON1, GSTM1 and GSTT1 in the Yucatán population differ to those observed in other ethnic groups and provide useful data for epidemiological studies.

Forensic evaluation of the AmpFℓSTR Identifiler kit in nine Mexican native populations from the pre-Columbian Mesoamerican region.

Allele frequency distribution and forensic parameters of the AmpFℓSTR Identifiler kit was determined in nine Mexican Amerindian populations based on 1,040 unrelated individuals from the pre-Columbian region known as Mesoamerica. Hardy-Weinberg equilibrium was demonstrated for most of the short tandem repeats (STRs) in all nine populations. The power of discrimination and exclusion were higher than 0.99999 and 0.997942, respectively. In addition, a brief overview of the genetic relatedness and structure (F st = 2.62 %; p = 0.00000) between these populations is presented.

Population structure and paternal admixture landscape on present-day Mexican-Mestizos revealed by Y-STR haplotypes.

Mestizos currently represent most of the Mexican population (>90%); they are defined as individuals born in the country having a Spanish-derived last name, with family antecedents of Mexican ancestors back at least to the third generation. Mestizos are result of 500 years of admixture mainly among Spaniards, Amerindians, and African slaves. Consequently, a complex genetic pattern has been generated throughout the country that has been scarcely studied from the paternal point of view. This fact is important, taking into account that gene flow toward the New World comprised largely males. We analyzed the population structure and paternal admixture of present-day Mexican-Mestizo populations based on Y-STRs. We genotyped at least 12 Y-STRs in DNA samples of 986 males from five states: Aguascalientes (n = 293); Jalisco (n = 185); Guanajuato (n = 168); Chiapas (n = 170); and Yucatán (n = 170). AmpFlSTR Y-filer and Powerplex-Y(R) kits were used. Inclusion of North and Central Y-STR databases in the analyses allowed obtaining a Y-STR variability landscape from Mexico. Results confirmed the population differentiation gradient previously noted in Mestizos with SNPs and autosomal STRs throughout the Mexican territory: European ancestry increments to the Northwest and, correspondingly, Amerindian ancestry increments to the Center and Southeast. In addition, SAMOVA test and Autocorrelation Index for DNA Analysis autocorrelogram plot suggested preferential gene flow of males with neighboring populations in agreement with the isolation-by-distance model. Results are important for disease-risk studies (principally male-related) and for human identification purposes, because Y-STR databases are not available on the majority of Mexican-Mestizo populations.

Origin and genetic differentiation of three Native Mexican groups (Purépechas, Triquis and Mayas): contribution of CODIS-STRs to the history of human populations of Mesoamerica.

BACKGROUND: CODIS-STRs in Native Mexican groups have rarely been analysed for human identification and anthropological purposes. AIM: To analyse the genetic relationships and population structure among three Native Mexican groups from Mesoamerica. SUBJECTS AND METHODS: 531 unrelated Native individuals from Mexico were PCR-typed for 15 and 9 autosomal STRs (Identifiler™ and Profiler™ kits, respectively), including five population samples: Purépechas (Mountain, Valley and Lake), Triquis and Yucatec Mayas. Previously published STR data were included in the analyses. RESULTS: Allele frequencies and statistical parameters of forensic importance were estimated by population. The majority of Native groups were not differentiated pairwise, excepting Triquis and Purépechas, which was attributable to their relative geographic and cultural isolation. Although Mayas, Triquis and Purépechas-Mountain presented the highest number of private alleles, suggesting recurrent gene flow, the elevated differentiation of Triquis indicates a different origin of this gene flow. Interestingly, Huastecos and Mayas were not differentiated, which is in agreement with the archaeological hypothesis that Huastecos represent an ancestral Maya group. Interpopulation variability was greater in Natives than in Mestizos, both significant. CONCLUSION: Although results suggest that European admixture has increased the similarity between Native Mexican groups, the differentiation and inconsistent clustering by language or geography stresses the importance of serial founder effect and/or genetic drift in showing their present genetic relationships.

Admixture and genetic relationships of Mexican Mestizos regarding Latin American and Caribbean populations based on 13 CODIS-STRs.

Short tandem repeats (STRs) of the combined DNA index system (CODIS) are probably the most employed markers for human identification purposes. STR databases generated to interpret DNA profiles are also helpful for anthropological purposes. In this work, we report admixture, population structure, and genetic relationships of Mexican Mestizos with respect to Latin American and Caribbean populations based on 13 CODIS-STRs. In addition, new STR population data were included from Tijuana, Baja California (Northwest, Mexico), which represents an interesting case of elevated genetic flow as a bordering city with the USA. Inter-population analyses included CODIS-STR data from 11 Mexican Mestizo, 12 Latin American and four Caribbean populations, in addition to European, Amerindian, and African genetic pools as ancestral references. We report allele frequencies and statistical parameters of forensic interest (PD, PE, Het, PIC, typical PI), for 15 STRs in Tijuana, Baja California. This Mexican border city was peculiar by the increase of African ancestry, and by presenting three STRs in Hardy-Weinberg disequilibrium, probably explained by recurrent gene flow. The Amerindian ancestry in Central and Southeast of Mexico was the greatest in Latin America (50.9-68.6%), only comparable with the North of Central America and Ecuador (48.8-56.4%), whereas the European ancestry was prevalent in South America (66.7-75%). The African ancestry in Mexico was the smallest (2.2-6.3%) in Latin America (≥ 2.6%), particularly regarding Brazil (21%), Honduras (62%), and the Caribbean (43.2-65.2%). CODIS-STRs allowed detecting significant population structure in Latin America based on greater presence of European, Amerindian, and African ancestries in Central/South America, Mexican Mestizos, and the Caribbean, respectively.

Deletion mapping and paternal origin of a Mexican AMELY negative male.

The amelogenin represents the gender marker most widely used for human identification and biomedical purposes. However, some failures in sex-typing have been observed globally. In this study, we could approximate the population frequency of AMELY negative males in 1230 individuals from five states of Mexico (0.081%). For the sole AMELY negative male detected, we constructed a deletion map by means of 10 markers (7 STS and 3 Y-STRs). This allowed classifying the case into the most common category (Class I deletion), according to the nomenclature proposed by Jobling et al. (2007). Interestingly, the Mexican sample was R1a1(∗), a Y-chromosome haplogroup non-previously reported for AMELY negative cases. The geographic distribution of R1a1(∗), and the Y-STR haplotype similarity with a reported case from Slovenia, suggests an Eastern-Europe paternal origin for this case from Mexico. To our knowledge, this is the first report in Latin America that implies a low population frequency and European paternal origin of AMELY negative cases.

Genetic data of 15 autosomal STRs (Identifiler kit) of three Mexican Mestizo population samples from the States of Jalisco (West), Puebla (Center), and Yucatan (Southeast).

We report autosomal STR data (Identifiler PCR amplification kit) of a total sample of 884 unrelated Mestizos from three different regions of Mexico. The population sample included 309, 313 and 262 individuals from the states of Jalisco (West), Puebla (Center) and Yucatan (Southeast), respectively. Allele distribution and forensic statistical parameters are described. Genotype distribution by locus and two-loci combination was in agreement with Hardy-Weinberg expectations for all 15 STRs. Pairwise comparisons including Mexican populations reported in the literature demonstrated a significant differentiation, principally between North/West with regard to Center/Southeast Mexico. These results increase STR data from previously unreported regions of this country, and constitute a valuable guide in forensic casework for choosing an auxiliary STR database in states where it is not available.