"Distribution of paternal lineages in Mestizo populations throughout Mexico: an in silico study based on Y-STR haplotypes".

The Mexican-Mestizo population arose following European contact with the Americas due to the admixture of principally Spaniards, Native Americans, and Africans around 500 years ago. Because the paternal lineage distribution of the Mexican population has been poorly investigated, this study inferred the haplogroups of ten populations based on 1859 haplotypes (Y-STR data) using two haplogroup predictor programs. In the Mexican population sample, we found predominantly European ancestry (50.1%), followed by Native American (32.5%), Eurasian (13.4%), African (2.1%), East African-South Eurasian (1.3%), and Asian (0.6%) ancestries. In general, our results support a contrary north-to-south gradient throughout the Mexican territory of European and Native-American ancestries, respectively. Moreover, the presence of West-European R1b and Sub-Saharan African E1b1a haplogroups agrees with historical and genetic data of gene flow during the European conquest. This study represents the effort to analyze these paternal lineages on a large scale by taking advantage of Y-STR haplotype data to determine the distribution and ancestry proportions in this country.

PRL -1149T allele (rs1341239) is associated with decreased risk of rheumatoid arthritis in population from southern Mexico: analysis of mRNA expression and PRL serum levels.

INTRODUCTION: Prolactin (PRL) is a sex hormone with immunomodulatory properties, and it is associated with the clinical activity of rheumatoid arthritis (RA). The -1149G>T polymorphism at the prolactin (PRL) gene has been associated with autoimmune diseases, but its functional effect is unclear. OBJECTIVE: To analyze the association of the PRL -1149G>T polymorphism with disease susceptibility, mRNA, and protein expression of PRL in RA patients from Southern Mexico. METHODS: We included 300 RA patients and 300 control subjects (CS). Genotypes were identified by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique, the PRL mRNA expression was determined by real-time PCR, and PRL serum levels were measured by enzyme-linked immunosorbent assay. RESULTS: Applying genetic models of inheritance (dominant, recessive, and additive), we found an association between the T allele and decreased RA susceptibility (OR = 0.55, 95% CI 0.35-0.87, p = 0.009; OR = 0.09, 95% CI 0.012-0.76, p = 0.011; OR = 0.49, 95% CI 0.32-0.76, p = 0.001, respectively). RA patients had higher mRNA expression and soluble levels of PRL than CS (p < 0.05). The PRL serum levels were similar in RA and CS according to genotypes. However, in CS, carriers of GT and TT genotypes showed lower PRL mRNA expression than GG genotype carriers (7.1-fold and 20-fold respectively, p = 0.006). CONCLUSIONS: This study demonstrated that the PRL -1149T allele is a genetic marker of decrease risk to RA in population from Southern Mexico, and it is associated with low PRL mRNA. KEY POINTS: • PRL -1149T allele is a marker of decreased RA susceptibility in population from southern Mexico. • PRL -1149TT genotype is associated with low PRL mRNA expression. • RA patients have higher mRNA expression and soluble levels of PRL than healthy subjects. • PRL serum levels are higher in those RA patients with < 2 years of disease evolution.

Forensic parameters of 15 autosomal STRs (Identifiler™ kit) in three Mayan groups and one Mestizo population from Guatemala.

The population of Guatemala includes Mestizos (admixed) and different Mayan groups (Native Americans), which have been poorly studied in regards to short tandem repeat (STR) loci used for human identification (HID) purposes. Therefore, 483 unrelated Guatemalan volunteers from one Mestizo and three Mayan populations (Poqomchi, Ixil, and Achi) were analyzed with an AmpFlSTR Identifiler™ kit. Allele frequencies and forensic parameters were obtained for 15 autosomal STRs in these populations. Hardy-Weinberg equilibrium by locus and equilibrium linkage between pair of loci were demonstrated by exact tests in all the studied populations. Larger genetic differentiation probably due to genetic drift effects was observed among the studied Guatemalan Mayan groups than the neighboring Mexican Mayas. In brief, our results validate to use the Identifiler™ kit for HID in three non-previously studied Mayan groups, and one Mestizo population from Guatemala.

Population data for 21 autosomal STR loci (GlobalFiler kit) in two Mexican-Mestizo population from the northwest, Mexico.

Mexican Mestizos (admixed) have been poorly studied for short tandem repeats (STRs) included for new human identification (HID) kits, such as the GlobalFiler PCR Amplification kit. Therefore, this kit was analyzed in 784 unrelated volunteers from the city of Tijuana (n = 381) and Sonora state (n = 403) in the northwest region of Mexico. Allele frequencies, forensic parameters, Hardy-Weinberg equilibrium, and linkage equilibrium were estimated or evaluated for 21 autosomal STRs, respectively. For this HID kit, the combined power of discrimination (PD) was > 0.99999999999999 (RMP range = 1.23 to 3.0 × 10-25), and the combined power of exclusion (PE) were 0.999999993 and 0.999999997 in Tijuana city and Sonora state, respectively. Interpopulation analyses based on STRs of the GlobalFiler kit was performed, including four Mexican Native American, one Mexican Mestizo, and four ethnic American populations (USA), previously studied. The low-but significant-differentiation observed among Mexican Mestizos (FST = 0.0969%; p = 0.02584) justifies the creation of STR databases for HID purposes in this country. In brief, results allow the confident use of the GlobalFiler kit for HID purposes in Mestizo population from the Northwest region Mexico.

Association of human beta-defensin 1 gene polymorphisms with nonsegmental vitiligo.

BACKGROUND: Vitiligo is a pigmentation disorder of autoimmune aetiology. Polymorphisms in beta-defensin genes have been linked to a predisposition to some autoimmune disorders. AIM: To evaluate the role of polymorphisms in DEFB1, the gene encoding for human beta-defensin (HBD)-1 and its 5' untranslated region in nonsegmental vitiligo. METHODS: In total, 354 participants [171 patients with non-segmental vitiligo and 183 age and sex-matched healthy controls (HCs)], were genotyped by the PCR-restriction fragment length polymorphism (RFLP) method. For 80 of these individuals (40 patients and -40 HCs) serum HBD-1 was also measured by ELISA. RESULTS: The -44 G allele, CG genotype and GGG haplotype increased the risk for vitiligo (P < 0.02 in all cases), whereas the -20 AA genotype seems to be protective (P = 0.04). Serum HBD-1 levels were lower in patients with vitiligo than in HCs (P < 0.01), as well as in patients with active vitiligo compared with those with stable vitiligo and with HCs (P < 0.05 in both cases), CONCLUSION: Our results suggest that HBD-1 and its gene polymorphisms may modulate vitiligo susceptibility and/or disease activity. This is the first report, to our knowledge, of the association of serum HBD-1 levels and DEFB1 gene polymorphisms with vitiligo.

Correspondence between the CYP2C19 and CYP3A4 genotypes with the inferred metabolizer phenotype by omeprazole administration in Mexican healthy children.

WHAT IS KNOWN AND OBJECTIVE: CYP2C19 genotypes presumably allow the prediction of the metabolizer phenotypes: poor (PMs), extensive (EMs) and ultra-rapid (UMs). However, evidence from previous studies regarding this predictive power is unclear, which is important because the benefits expected by healthcare institutions and patients are based on this premise. Therefore, we aimed to complete a formal evaluation of the diagnostic value of CYP2C19 and CYP3A4 genes for predicting metabolizer phenotypes established by omeprazole (OME) administration in 118 healthy children from Jalisco (western Mexico). METHODS: The genotypes for CYP3A4*1B and CYP2C19*2, *3, *4, *5 and *17 alleles were determined. CYP2C19 and CYP3A4 phenotypes were obtained after 20 mg OME administration and HPLC quantification in plasma to estimate the Hydroxylation Index (HI = OME/HOME) and Sulfonation Index (SI = OME/SOME), respectively. RESULTS AND DISCUSSION: The distribution of genotypes and phenotypes for CYP2C19 and CYP3A4 was similar to previous studies in Mexico and Latin America. We estimated the CYP2C19 UM, EM and PM phenotype frequency in 0.84%, 96.61% and 2.54%, respectively. Although differences in the HI distribution were observed between CYP2C19 genotypes, they showed a poor diagnostic ability to predict the CYP2C19 metabolizer phenotype. Similarly, the number of CYP2C19 and CYP3A4 functional alleles was correlated with the HI distribution, but also their diagnostic ability to predict the CYP2C19 phenotype was poor. WHAT IS NEW AND CONCLUSION: The CYP2C19 phenotype is not predicted by the number of functional alleles of CYP2C19 and CYP3A4 genes. Phenotyping is still the most valuable alternative to dose individualization for CYP2C19 substrate drugs.

Forensic parameters for 15 autosomal STRs in Mestizo population from the state of Guerrero (South, Mexico).

Allele distribution and forensic parameters were estimated for 15 STR loci (AmpFlSTR Identifiler kit) in 251 Mexican-Mestizos from the state of Guerrero (South, Mexico). Genotype distribution was in agreement with Hardy-Weinberg expectations for all 15 STRs. Similarly, linkage disequilibrium test demonstrated no association between pair of loci. The power of exclusion and power of discrimination values were 99.999634444% and >99.99999999%, respectively. Genetic relationship analysis regarding Mestizo populations from the main geographic regions of Mexico suggests that the Center and the present South regions conform one population cluster, separated from the Southeast and Northwest regions.

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

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.

Paternity tests in Mexico: Results obtained in 3005 cases.

National and international reports regarding the paternity testing activity scarcely include information from Mexico and other Latin American countries. Therefore, we report different results from the analysis of 3005 paternity cases analyzed during a period of five years in a Mexican paternity testing laboratory. Motherless tests were the most frequent (77.27%), followed by trio cases (20.70%); the remaining 2.04% included different cases of kinship reconstruction. The paternity exclusion rate was 29.58%, higher but into the range reported by the American Association of Blood Banks (average 24.12%). We detected 65 mutations, most of them involving one-step (93.8% and the remaining were two-step mutations (6.2%) thus, we were able to estimate the paternal mutation rate for 17 different STR loci: 0.0018 (95% CI 0.0005-0.0047). Five triallelic patterns and 12 suspected null alleles were detected during this period; however, re-amplification of these samples with a different Human Identification (HID) kit confirmed the homozygous genotypes, which suggests that most of these exclusions actually are one-step mutations. HID kits with ≥20 STRs detected more exclusions, diminishing the rate of inconclusive results with isolated exclusions (<3 loci), and leading to higher paternity indexes (PI). However, the Powerplex 21 kit (20 STRs) and Powerplex Fusion kit (22 STRs) offered similar PI (p = 0.379) and average number of exclusions (PE) (p = 0.339) when a daughter was involved in motherless tests. In brief, besides to report forensic parameters from paternity tests in Mexico, results describe improvements to solve motherless paternity tests using HID kits with ≥20 STRs instead of one including 15 STRs.

Forensic parameters of the X-STR Decaplex system in Mexican populations.

We studied the X-STR decaplex system in 529 DNA female samples of Mexican populations from five geographic regions. Allele frequencies and forensic parameters were estimated in each region and in the pooled Mexican population. Genotype distribution by locus was in agreement with Hardy-Weinberg expectations in each Mexican population sample. Similarly, linkage equilibrium was demonstrated between pair of loci. Pairwise comparisons and genetic distances between Mexican, Iberoamerican and one African populations were estimated and graphically represented. Interestingly, a non-significant interpopulation differentiation was detected (Fst = 0.0021; p = .74389), which allows using a global Mexican database for forensic interpretation of X-STR genotypes.

Forensic efficiency parameters of the Investigator Argus X-12 kit in women from two Mestizo and seven Amerindian populations from Mexico.

Allele frequency distribution and statistical parameters of forensic efficiency concerning the Investigator Argus X-12 kit (Qiagen, Hilden, Germany) were determined in a total sample of 641 unrelated Mexican females, including two Mestizo-admixed- populations (n=309) and seven Amerindian groups (n=332) from the main regions of the country. Most of the 12 X-STRs were in agreement with Hardy-Weinberg expectations in all nine Mexican populations. The power of discrimination in females (PD) and Median exclusion chance for trios (MECT) and duos (MECD) of this genetic system based on X-STRs were >99.99%. Although Mexican populations showed significant pairwise differentiation, a closer relationship was evident between Amerindian groups and nearby Mestizos, in agreement with historical records, previous genetic studies, and X-linked inheritance pattern expectations.

Population data of 23 STR loci (PowerPlex® Fusion System) in Mexican Mestizos from the West Region.

We analyzed 238 unrelated Mestizo (admixed) individuals from the West region of Mexico with the PowerPlex® Fusion System (Promega Corp.). Allele frequencies and forensic parameters were estimated for the 23 STRs included in this kit. Hardy-Weinberg equilibrium by locus and non-association between pair of loci were demonstrated by exact tests in this population. The combined PE and PD offered by this HID kit were ≥0.9999999986, representing a substantial improvement with respect to those previously offered by 15 STR systems. Interpopulation comparison by AMOVA tests demonstrated low but significant differences among Mexican Mestizos from West, Center, and Northeast regions (Fst = 0.01558; p = 0.0000), similar to the observed among three main ethnic groups from USA (Fst = 0.02048; p = 0.0000). This finding is consistent with the contrary clines of European and Amerindian ancestries described throughout the Mexican territory for Mestizos, the largest population (~90 %) in this country.

Forensic parameters of the Investigator DIPplex kit (Qiagen) in six Mexican populations.

Allele frequencies and statistical parameters of forensic efficiency for 30 deletion-insertion polymorphisms (DIPs) were estimated in six Mexican populations. For this purpose, 421 unrelated individuals were analyzed with the Investigator DIPplex kit. The Hardy-Weinberg and linkage equilibrium was demonstrated for this 30-plex system in all six populations. We estimated the combined power of discrimination (PD ≥ 99.999999%) and combined power of exclusion (PE ≥ 98.632705%) for this genetic system. A low but significant genetic structure was demonstrated among these six populations by pairwise comparisons and AMOVA (F ST ≥ 0.7054; p ≤ 0.0007), which allows clustering populations in agreement with geographical criteria: Northwest, Center, and Southeast.

Genetic structure and forensic parameters of 38 Indels for human identification purposes in eight Mexican populations.

Insertion-deletions for human identification purposes (HID-Indels) offer advantages to solve particular forensic situations and complex paternity cases. In Mexico, admixed population known as Mestizos is the largest (∼90%), plus a number of Amerindian groups (∼10%), which have not been studied with HID-Indels. For this reason, allele frequencies and forensic parameters for 38 HID-Indels were estimated in 531 unrelated individuals from one Amerindian (Purépecha) and seven Mestizo populations from different regions of the country. Genotype distribution was in agreement with Hardy-Weinberg expectations in almost all loci/populations. The linkage disequilibrium (LD) test did not reveal possible associations between loci pairs in all eight Mexican populations. The combined power of discrimination was high in all populations (PD >99.99999999998%). However, the power of exclusion of the 38 HID-Indel system (PE >99.6863%) was reduced regarding most of autosomal STR kits. The assessment of genetic structure (AMOVA) and relationships between populations (FST) demonstrated significant differences among Mexican populations, mainly of the Purépecha Amerindian group. Among Mexican-Mestizos, three population clusters consistent with geography were defined: (i) North-West region: Chihuahua, Sinaloa, and Jalisco; (ii) Central-Southern region: Mexico City, Veracruz and Yucatan; (iii) South region: Chiapas. In brief, this report validates the inclusion of the 38 HID-Indel system in forensic casework and paternity cases in seven Mexican-Mestizo populations from different regions, and in one Mexican Amerindian group.

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.

Glucose-6-phosphate dehydrogenase deficiency in northern Mexico and description of a novel mutation.

Glucose-6-phosphate dehydrogenase deficiency (G6PD) is the most common enzyme pathology in humans; it is X-linked inherited and causes neonatal hyperbilirubinaemia, chronic nonspherocytic haemolytic anaemia and drug-induced acute haemolytic anaemia. G6PD deficiency has scarcely been studied in the northern region of Mexico, which is important because of the genetic heterogeneity described in Mexican population. Therefore, samples from the northern Mexico were biochemically screened for G6PD deficiency, and PCR-RFLPs, and DNA sequencing used to identify mutations in positive samples. The frequency of G6PD deficiency in the population was 0.95% (n = 1993); the mutations in 86% of these samples were G6PD A(-202A/376G), G6PDA(-376G/968C) and G6PD Santamaria(376G/542T). Contrary to previous reports, we demonstrated that G6PD deficiency distribution is relatively homogenous throughout the country (P = 0.48336), and the unique exception with high frequency of G6PD deficiency does not involve a coastal population (Chihuahua: 2.4%). Analysis of eight polymorphic sites showed only 10 haplotypes. In one individual we identified a new G6PD mutation named Mexico DF(193A>G) (rs199474830), which probably results in a damaging functional effect, according to PolyPhen analysis. Proteomic impact of the mutation is also described.

Duchenne muscular dystrophy in a developing country: challenges in management and genetic counseling.

BACKGROUND AND OBJECTIVE: Multidisciplinary management of Duchenne Muscular Dystrophy (DMD) has achieved outstanding results in developed nations. We aimed to describe the status of diagnosis and management of DMD in a developing country through the experience of non-profit organizations. METHODS: A Multistate, multiple-source, population-based survey was performed from medical records of 432 patients. Data were retrospectively collected, reviewed and curated by health specialists; including clinical features, age at first symptoms, age at diagnosis, disease progression and management, family history, education, age and cause of death. RESULTS: There is a delay in noticing first symptoms and it did not diminish over the past 20 years. Less than 30% of patients obtained definite diagnosis and most of them are in physiotherapy programs but not under steroid treatment. In our study, family history does not anticipate recognition of symptoms compared to sporadic cases (p = 0.05). Approximately 93.33% of our patients attended to education programs. Mean age at death was 18.94 +/- 6.73 years and the most frequent cause was pneumonia. CONCLUSION: Delayed diagnosis of DMD in Mexico is mainly caused by the late detection of first symptoms. There is no difference in early detection of symptoms between familiar and sporadic cases. Lifespan of patients in our cohort is reduced compared to developed countries. The late diagnosis and low percentage of definite cases may affect patient management and genetic counseling and could also preclude participation of patients into novel clinical trials.

DEFB1 5'UTR polymorphisms modulate the risk of HIV-1 infection in Mexican women.

Immunologic and genetic factors are involved in HIV-1/AIDS pathogenesis. Defensins are key molecules in innate immunity that participate in the control and/or development of infection and disease. Using PCR-RFLPs, we determined the association between HIV-1/AIDS and human ß-defensin 1 (DEFB1) 5'UTR -52 G/A (rs1799946), -44 C/G (rs1800972), and -20 G/A (rs11362) polymorphisms in three groups of women from the state of Sinaloa, located in the Northwest region of Mexico: i) healthy blood donors; ii) sex-workers; and iii) HIV-1 patients. The -52GG genotype was more frequent in blood donors than in patients (p= 0.023; Odds Ratio, OR= 0.49; 95% CI= 0.25-0.95), whereas the - 52GA genotype was significantly higher in patients (p= 0.013; OR= 2.03; 95% CI= 1.11-3.79, statistical power SP= 98.8%), as well as the frequencies of -20A allele (p= 0.017; OR= 1.60; 95% CI= 1.06-2.40), -20AA genotype (p= 0.047; OR = 2.02; 95% CI= 0.93-4.33) and the ACA haplotype with respect to healthy blood donors (p= 0.000012; OR= 5.82; 95% CI= 2.33-16.43, SP= 99.89%) and sex-workers (p= 0.019; OR= 2.18; 95% CI= 1.07-4.46). Conversely, the ACG haplotype was higher in healthy blood donors than in patients (p= 0.009; OR= 0.55; 95% CI= 0.34-0.89). In addition, the -44CC genotype was associated with a low plasma viral load (p= 0.015), whereas AGA, AGG and GGA haplotypes were more prevalent in individuals with high CD4 counts (p= 0.004, 0.046, and 0.029, respectively). These findings associate DEFB1 5'UTR polymorphisms with HIV-1/AIDS in Mexican women for the first time.

Macrophage migration inhibitory factor: association of -794 CATT5-8 and -173 G>C polymorphisms with TNF-α in systemic lupus erythematosus.

Macrophage migration inhibitory factor (MIF) is an upstream immunoregulatory cytokine associated with the pathogenesis of autoimmune inflammatory diseases. There is evidence that MIF functions in a positive feedback loop with TNF-α that could perpetuate the inflammatory process in systemic lupus erythematosus (SLE). In this case-control study we investigated whether commonly occurring functional MIF polymorphisms are associated with SLE as well as with MIF and TNF-α serum levels in a Mexican-Mestizo population. Genotyping of the -794 CATT5-8 (rs5844572) and -173 G>C (rs755622) MIF polymorphisms was performed by PCR and PCR-RFLP, respectively in 186 SLE patients and 200 healthy subjects. MIF and TNF-α serum levels were determined by ELISA. A significant increase of MIF and TNF-α levels was found in SLE patients. According to a genetic model, we found a significant association of genotypes carrying the -794 CATT7 and -173(∗)C risk alleles with susceptibility to SLE and with a significant increase of TNF-α. In conclusion, MIF gene polymorphisms are associated with SLE susceptibility and with an increase of TNF-α serum levels in a Mexican-Mestizo population.

Forensic parameters for 15 STRs in eight Amerindian populations from the north and west of Mexico.

Allele frequency distributions for 15 STR loci (AmpFlSTR Identifiler kit) were estimated in 825 volunteers of the following eight Mexican-Amerindian populations from two geographical regions: (1) North: Tarahumara (204), Mayo (45), Seri (28), and Guarijío (17); (2) Northwest: Tepehuano (123), Mexicanero (84), Cora (85), and Huichol (239). Genotype frequency distribution was in agreement with Hardy-Weinberg expectations for all 15 STRs, excepting for two loci (D13S317 and FGA) in the Huichol population. The power of discrimination and power of exclusion values were both larger than 0.99999. These STR databases will support the correct interpreting of DNA profiles in paternity testing and forensic cases in Mexican-Amerindian groups from these regions, until know poorly studied. Genetic distances and pairwise comparisons were estimated between populations. A significant genetic differentiation was observed between these Mexican-Amerindian groups (F(ST)=3.43%; p=0.0000) that was 10 times larger than the observed between Mestizos (F(ST)=0.34%), which represent most of the Mexican population (~90%). This result was in agreement with the incapability to cluster these Native American populations by geographic criteria. Pre-Colombian descriptions of Aridoamerica, including the North region of Mexico, suggest genetic drift effects to explain this noticeable population differentiation of Mexican-Amerindian groups.