Genetic structure of three Native Mexican communities based on mtDNA haplogroups, and ABO and Rh blood group systems.

OBJECTIVE: The goals of this population genetics study were to describe mtDNA haplogroups and ABO and Rh blood group systems of 3 Native Mexican populations, to determine their genetic variability, and to compare their haplogroups with those of 13 Native Mexican populations previously reported. MATERIAL AND METHODS: The three communities under analysis were a Tepehua-speaking community from Huehuetla (Hidalgo state), an Otomi-speaking community from San Antonio el Grande (Hidalgo state), and a Zapotec-speaking community from Juchitán (Oaxaca state). Every subject studied in each community had four grandparents who were born in the same community and spoke the same language. The four Amerindian mtDNA haplogroups (A, B, C and D) were studied by restriction analysis and gel electrophoresis. RESULTS: Regarding the blood groups, the O group was the most frequent in the three populations (97.2, 94.7, and 86.2%, respectively), as well as the Rh+ group (100, 100, 84%). The three populations analyzed were in Hardy-Weinberg equilibrium. In respect to the mtDNA haplogroups, A, B, C and D, their percentage was 33.3, 36.1, 13.9 and 5.6 % in Huehuetla; 39.5, 13.2, 39.5 and 2.6 % in San Antonio el Grande, and 55.3, 21.0, 7.9 and 5.2 % in Juchitán. Between 5 and 11% of the haplogroups were of non-Amerindian origin, probably due to admixture with Caucasian and African populations, as has been reported in the past. No statistically-significant differences were found among the three populations studied or between them and 13 previously reported Native Mexican populations.

Genetic admixture of eight Mexican indigenous populations: based on five polymarker, HLA-DQA1, ABO, and RH loci.

This study explores the genetic admixture of eight Mexican indigenous populations (Otomi-Ixmiquilpan, Otomi-Actopan, Tzeltales, Nahua-Milpa-Alta, Nahua-Xochimilco, Nahua-Zitlala, Nahua-Ixhuatlancillo, and Nahua-Coyolillo) on the basis of five PCR-based polymorphic DNA loci (LDLR, GYPA, HBGG, D7S8, GC), HLA_DQA1, and the blood groups ABO and Rh (CcDEe). Among the indigenous populations, the highest gene frequencies for O and D were 0.9703 and 1.000 for Zitlala (State of Guerrero) and 0.9955 and 0.9414 for Tzeltales (State of Chiapas), respectively. Maximum likelihood estimates of admixture components yield a trihybrid model with Amerindian (assuming that Nahua-Zitlala is the most representative indigenous population), Spanish, and African ancestry with the admixture proportions: 93.03, 6.03, and 0.94 for Tzeltales, and 28.99, 44.03, and 26.98 for Coyolillo. A contribution of the ancestral populations of Ixhuatlancillo, Actopan, Ixmiquilpan, Milpa-Alta, and Xochimilco were found with the following average of admixture proportions: 75.84, 22.50, and 1.66. The findings herein demonstrate that the genetic admixture of the Mexican indigenous populations who at present speak the same Amer-Indian language can be differentiated and that the majority of them have less ancestral indigenous contribution than those considered as Mestizo populations.

Genetic structure of seven Mexican indigenous populations based on five polymarker loci.

This descriptive study investigates the genetic structure of seven Mexican indigenous populations (Mixteca Alta, Mixteca Baja, Otomies, Purepecha, Nahuas-Guerrero, Nahuas-Xochimilco, and Tzeltales) on the basis of five PCR-based polymorphic DNA loci: LDLR, GYPA, HBGG, D7S8, and GC. Genetic distance and diversity analyses indicate that these Mexican indigenous are similar and that more than 96% of the total gene diversity (H(T)) can be attributed to individual variation within populations. Mixteca-Alta, Mixteca-Baja, and Nahuas-Xochimilco show indications of higher admixture with European-derived persons. The demonstration of a relative genetic homogeneity of Mexican Indians for the markers studied suggests that this population is suitable for studying disease-marker associations in the search for candidate genes of complex diseases.