Characterization of mtDNA haplogroups in 14 Mexican indigenous populations.

In this descriptive study we investigated the genetic structure of 513 Mexican indigenous subjects grouped in 14 populations (Mixteca-Alta, Mixteca-Baja, Otomi, Purépecha, Tzeltal, Tarahumara, Huichol, Nahua-Atocpan, Nahua-Xochimilco, Nahua-Zitlala, Nahua-Chilacachapa, Nahua-Ixhuatlancillo, Nahua-Necoxtla, and Nahua-Coyolillo) based on mtDNA haplogroups. These communities are geographically and culturally isolated; parents and grandparents were born in the community. Our data show that 98.6% of the mtDNA was distributed in haplogroups A1, A2, B1, B2, C1, C2, D1, and D2. Haplotype X6 was present in the Tarahumara (1/53) and Huichol (3/15), and haplotype L was present in the Nahua-Coyolillo (3/38). The first two principal components accounted for 95.9% of the total variation in the sample. The mtDNA haplogroup frequencies in the Purépecha and Zitlala were intermediate to cluster 1 (Otomi, Nahua-Ixhuatlancillo, Nahua-Xochimilco, Mixteca-Baja, and Tzeltal) and cluster 2 (Nahua-Necoxtla, Nahua-Atocpan, and Nahua-Chilacachapa). The Huichol, Tarahumara, Mixteca-Alta, and Nahua-Coyolillo were separated from the rest of the populations. According to these findings, the distribution of mtDNA haplogroups found in Mexican indigenous groups is similar to other Amerindian haplogroups, except for the African haplogroup found in one population.

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.

Distribution of class I and class III MHC antigens in the Tarasco Amerindians.

Class I and class III major histocompatibility complex (MHC) antigen frequencies were analyzed in 130 haplotypes from 33 families belonging to a group of Amerindians culturally and linguistically isolated for more than 12 centuries in Mexico: the Tarascos. The most frequent antigens in this ethnic group of the HLA-A locus are: A2 (gf 0.353), A24 (gf = 0.223), A31 (gf = 0.184), and A28 (gf = 0.161); and the most frequent of the HLA-B locus are: B35 (gf = 0.230), B39 (gf = 0.192), B15 (gf = 0.146), and B5 (gf = 0.123). On the other hand, class III antigens demonstrated relatively high frequencies of the SC31 (frequency = 0.561), SC01 (frequency = 0.076), and SC42 (frequency = 0.069) complotypes. Also important was the relatively high frequency of the HLA-B27 antigen (gf 0.061) and the SC33 complotype (frequency = 0.046), which are either absent or found infrequently in other Amerindian groups. Analysis of MHC haplotypes revealed that four of them have relatively high frequencies, these were the following: [B39;SC31] (11.6%), [B35;SC31] (11.6%), [B15;SC31] (8.0%), and [B5;SC31] (5.8%). Other MHC haplotypes had frequencies lower than 5.0%. The decreased frequency of BF alleles other than BF*S and the presence of the SC33 and SC32 complotypes suggest long time preservation from genetic admixture. This information withstands the basis for population genetic analysis and disease association studies in Mexican mestizos.

El pleomorfismo clinico de la esclerodermia lineal: evidencia para la descripcion de dos fenotipos clinicos / The clinic pleomorphism of linear scleroderma: evidence for the description of 2 clinic phenotype

Estudiamos 25 pacientes con diagnostico histologico y clinico de esclerodermia lineal durante periodos de seguimiento de 8 a 46 meses de manera prospectiva. Este estudio hace enfasis en la diversidad de las manifestaciones cutaneas observadas que incluyeron, entre otras, aspecto de "sablazo", hemiatrofia facial y lesiones del cuero cabelludo y de la piel de la region frontal. Las variables estudiadas incluyeron: sexo, edad de inicio de la enfermedad, serologia, areas corporales afectadas y curso o forma de la entidad. Al realizar el analisis de estas variables, encontramos las siguientes correlaciones estadisticamente significativas: a) sexo y serologia (femenino y seropositividad, masculino y seronegatividad, con un p< 0.004); b) edad de inicio de la entidad y serologia ( inicio antes de los 12 anos de edad y seronegatividad con un p< 0.004); c) areas corporales afectadas y serologia (cara y seronegatividad, con p< 0.002; miembros inferiores y seroositividad, con p< 0.001-)d.) serologia y curso o forma de la enfermedad (seropositividad y curso severo con p< 0.005); e) edad de inicio de la enfermedad y seguimiento del paciente ( mayor de un ano con un p< 0.003). De acuerdo con los resultados obtenidos en un estudio, proponemos dos fenotipos para la esclerodermia lineal: 1: fenotipo I: inicio antes de los 12 anos, compromiso de la cara, curso leve a moderado y seronegatividad. b) fenotipo II: inicio de la enfermedad despues de los 12 anos compromiso de miembros inferiores curso moderado a severo y seropositividad. Ocho pacientes presentaron anticuerpos...