The Brazilian Xavante Indians revisited: new protein genetic studies

A população indígena Xavante em Mato Grosso: características sociodemográficas relacionadas à saúde

RESUMO Objetivo Comparar indicadores sociodemográficos dos Xavante de seis terras indígenas com a população não indígena residente em áreas rurais de quatro microrregiões adjacentes. Método Estudo seccional, do tipo ecológico, com análises comparativas entre indígenas e não indígenas residentes no estado de Mato Grosso, Brasil. Compararam-se os seguintes indicadores: estrutura etária e por sexo, taxa de alfabetização, renda, condições de saneamento dos domicílios e mortalidade. Resultados Foram caracterizadas 14.905 pessoas Xavante e 78.106 pessoas não indígenas (brancas, pretas, amarelas e pardas) residentes em domicílios de área rural. A estrutura etária revelou padrões divergentes, 40,0% dos Xavantes tinham menos de 10 anos de idade, contra 15,0% dos não indígenas na mesma faixa etária. Em relação aos não indígenas, os Xavantes apresentaram maior taxa de analfabetismo (31,3% vs. 9,9%) e 84,1% dos domicílios não possuíam banheiro ou sanitário, 39,6% das pessoas Xavante não declararam renda, contra 6,5% para os não indígenas. Conclusão e implicação para a prática Os dados sobre etnia, coletados pela primeira vez por um censo, são essenciais para análises demográficas de segmentos específicos da população, e, no caso dos Xavante, revelam desigualdades em relação aos não indígenas.

The Xavante indigenous population in Mato Grosso: health-related sociodemographic characteristics

ABSTRACT Objective To compare Xavante sociodemographic indicators from six indigenous lands with the non-indigenous population residing in rural areas of four adjacent microregions. Method This is an ecological cross-sectional study, with comparative analyzes between indigenous and non-indigenous residents in the state of Mato Grosso, Brazil. Age and sex structure, literacy rate, income, household sanitation conditions and mortality were compared. Results A total of 14,905 Xavante people and 78,106 non-indigenous people (white, black, yellow and brown) residing in rural areas were characterized. The age structure revealed divergent patterns, 40.0% of Xavante were under 10 years old, against 15.0% of non-indigenous people in the same age group. Regarding non-indigenous people, the Xavante had a higher illiteracy rate (31.3% vs. 9.9%), and 84.1% of the households did not have a bathroom or toilet, 39.6% of Xavante people did not declare an income against 6.5% for the non-indigenous. Conclusion and implication for practice Data on ethnicity, collected for the first time by a census, are essential for demographic analyzes of specific segments of the population, and in the case of the Xavante, they reveal inequalities in relation to non-indigenous people.

Blood groups in Native Americans: a look beyond ABO and Rh

The study presents comparisons between blood group frequencies beyond ABO and Rh blood systems in Native American populations and previously published data from Brazilian blood donors. The frequencies of Diego (c.2561C>T, rs2285644), Kell (c.578C>T, rs8176058), Duffy (c.125A>G, rs12075, c.1-67T>C, rs2814778) and Kidd (c.838A>G, rs1058396) variants in Kaingang (n=72) and Guarani (n=234) populations from Brazil (1990-2000) were obtained and compared with data from these populations sampled during the 1960s and with individuals of different Brazilian regions. Data showed high frequencies of DI*01 and FY*01 alleles: 11.8% and 57.6% in Kaingang and 6.8% and 75.7% in Guarani groups, respectively. The main results indicated: (1) reduction in genetic distance over time of Kaingang and Guarani in relation to other Brazilian populations is suggestive of ongoing admixture; (2) significant differences in some frequencies of blood group markers (especially Diego, Kidd and Duffy) in relation to Native Americans and individuals from different geographical regions of Brazil. Our study shows that the frequency of red blood cell polymorphisms in two Native American groups is very different from that of blood donors, when we evaluated blood groups different from ABO and Rh systems, suggesting that a better ethnic characterization of blood unit receptors is necessary.

Contrasting the ancestry patterns of three distinct population groups from the northernmost region of South America

Colombia, located in the north of the South American subcontinent is a country of great interest for population genetic studies given its high ethnic and cultural diversity represented by the admixed population, 102 indigenous peoples and African descent populations. In this study, an analysis of the genetic structure and ancestry was performed based on 46 ancestry informative INDEL markers (AIM-INDELs) and considering the genealogical and demographic variables of 451 unrelated individuals belonging to nine Native American, two African American, and four multiple ancestry populations. Measures of genetic diversity, ancestry components, and genetic substructure were analyzed to build a population model typical of the northernmost part of the South American continent. The model suggests three types of populations: Native American, African American, and multiple ancestry. The results support hypotheses posed by other authors about issues like the peopling of South America and the existence of two types of Native American ancestry. This last finding could be crucial for future research on the peopling of Colombia and South America in that a single origin of all indigenous communities should not be assumed. It then would be necessary to consider other events that could explain their genetic variability and complexity throughout the continent.

Genome-wide analysis in Brazilian Xavante Indians reveals low degree of admixture

Characterization of population genetic variation and structure can be used as tools for research in human genetics and population isolates are of great interest. The aim of the present study was to characterize the genetic structure of Xavante Indians and compare it with other populations. The Xavante, an indigenous population living in Brazilian Central Plateau, is one of the largest native groups in Brazil. A subset of 53 unrelated subjects was selected from the initial sample of 300 Xavante Indians. Using 86,197 markers, Xavante were compared with all populations of HapMap Phase III and HGDP-CEPH projects and with a Southeast Brazilian population sample to establish its population structure. Principal Components Analysis showed that the Xavante Indians are concentrated in the Amerindian axis near other populations of known Amerindian ancestry such as Karitiana, Pima, Surui and Maya and a low degree of genetic admixture was observed. This is consistent with the historical records of bottlenecks experience and cultural isolation. By calculating pair-wise F_st statistics we characterized the genetic differentiation between Xavante Indians and representative populations of the HapMap and from HGDP-CEPH project. We found that the genetic differentiation between Xavante Indians and populations of Ameridian, Asian, European, and African ancestry increased progressively. Our results indicate that the Xavante is a population that remained genetically isolated over the past decades and can offer advantages for genome-wide mapping studies of inherited disorders.

Haptoglobin gene subtypes in three Brazilian population groups of different ethnicities

Haptoglobin is a plasma hemoglobin-binding protein that limits iron loss during normal erythrocyte turnover and hemolysis, thereby preventing oxidative damage mediated by iron excess in the circulation. Haptoglobin polymorphism in humans, characterized by the Hp^*1 and Hp ^*2 alleles, results in distinct phenotypes known as Hp1-1, Hp2-1 and Hp2-2, whose frequencies vary according to the ethnic origin of the population. The Hp^*1 allele has two subtypes, Hp ^*1F and Hp ^*1S , that also vary in their frequencies among populations worldwide. In this work, we examined the distribution frequencies of haptoglobin subtypes in three Brazilian population groups of different ethnicities. The haptoglobin genotypes of Kayabi Amerindians (n = 56), Kalunga Afro-descendants (n = 70) and an urban population (n = 132) were determined by allele-specific PCR. The Hp^*1F allele frequency was highest in Kalunga (29.3%) and lowest in Kayabi (2.6%). The Hp^*1F/Hp^*1S allele frequency ratios were 0.6, 1.0 and 0.26 for the Kayabi, Kalunga and urban populations, respectively. This variation was attributable largely to the Hp^*1F allele. However, despite the large variation in Hp^*1F frequencies, results of F _ST (0.0291) indicated slight genetic differentiation among subpopulations of the general Brazilian population studied here. This is the first Brazilian report of variations in the Hp^*1F and Hp^*1S frequencies among non-Amerindian Brazilians.

Genetic studies in French Guiana populations: Synthesis

Twelve blood group and protein systems from a total of 819 individuals from six tribal groups (Apalaí-Wayana, Emerillon, Kaliña, Palikur Wayampi, and Wayana) living in French Guiana and Brazil were compared with each other and integrated with previous results from 17 other South Amerindian populations studied for the same genetic markers. Using correspondence analysis, map methodologies, and maximum linkage cluster analysis developed with the UPGMA method, we attempted to establish the genetic position of these tribes among South American Indians. Peripheral positions for the Emerillon and the Palikur were observed. Ethnohistorical data in French Guiana suggest that a strong founder effect for the former and endogamy for the latter could have generated the genetic differentiation of these two ethnic groups. However, when considered in a wider context, all French Guiana Natives cluster together in an intermediate position as compared with 17 other Amerindian groups studied for the comparison.

Mitochondrial DNA andAlu insertions in a genetically peculiar population: The Ayoreo Indians of Bolivia and Paraguay

A total of 91 Ayoreo individuals previously studied for blood groups and protein markers, living in two Bolivian and one Paraguayan communities, were extensively investigated in relation to the hypervariable 1 segment of the control and eight coding regions of their mitochondrial DNA (mtDNA). They show an extremely reduced mtDNA variability, the observed haplotypes being classifiable in just two haplogroups (C and D). They were also variously studied in relation to six Alu insertions; in this case, however, the prevalences found did not depart markedly from those obtained in other populations of this ethnic group. To assess the Ayoreo position in relation to these populations, 11 other groups that had also been studied for these systems and for blood groups and proteins were selected. The dendrograms obtained with two of the three sets of markers showed distinct patterns, but the Ayoreo were placed in a central position in both the blood group + proteins and Alu insertions trees. Therefore, they are clearly distinct in relation to their mtDNA only, suggesting a strong founder effect and/or random loss of variability in this system.

Lipoprotein lipase and APOE/APOC-I/APOC-II gene cluster diversity in native Brazilian populations

Allele and haplotype frequencies for the T-93G, Hind III, and Pvu II variants of the lipoprotein lipase gene (LPL), and Hpa I and Ava II restriction site polymorphisms (RSP) of the APOE/C-I/C-II gene cluster were determined in 143 individuals from five Brazilian Indian tribes. These results were integrated with those previously reported for APOE. Marked interethnic variability occurs in these sites. A strong linkage disequilibrium was observed between the APOE and APOC-I loci (D' = 0.81; P < 0.00001). Linkage disequilibrium between the Hind III and Pvu II RSPs of the LPL gene was also observed (D' = 1; P < 0.001), but none of these RSPs were in linkage disequilibrium with the T-93G mutation. Considering both loci, heterozygosity was estimated as 0.45, but it was lower in the Xavante and Surui populations, in accordance with the historical and biodemographical data of these Amerindians. The results reported here may have implications for understanding interpopulation differences in lipid levels and coronary heart disease prevalences.

Genetic variability in the Guahibo population from Venezuela

Four communities from Guahibo of Venezuela were analyzed for the genetic variants of nine erythrocyte enzymes and five serum proteins. Of the 14 loci determined, four were monomorphic. Significant frequency differentiation among communities, was present for ESD and TF markers. In general, Guahibo allele frequencies are in the variation ranges described for South American groups. The analysis indicates a relatively higher affinity of Guahibos with other Venezuelan groups within an irregular pattern of genetic distances that are likely related to the complex demographic history of the South American groups. Genetic diversity estimates reveal a moderate degree of genetic structure between the four Guahibo communities. This intra-tribal variability in Guahibo appears to be lower than in Venezuelan Piaroa but higher than in other Amerindians and could be attributed to a combined effect of low population size and relative isolation of communities. At a continental level, the distribution of genetic diversity is consistent with preferential population movements along the eastern and western coastal areas.

Albumin genetic variability in South America: Population distribution and molecular studies

A total of 5,020 individuals living in two southern Brazilian states were screened in relation to albumin types; two variants were found, in Passo Fundo (Nagasaki 2) and Vera Cruz (Tradate 2). Another variant, detected in the northeast, was identified as Porto Alegre 2, which also occurs in other places in Brazil, as well as in India, Pakistan, and Turkey. The results were integrated with those obtained in other studies in South America, yielding a total of 16,941 Amerindians and 23,839 non-Indian subjects. Molecular and physiological studies performed in some of the variants suggested clues to explain the restricted distribution of albumin Yanomama 2 and the widespread occurrence of albumin Maku. Am. J. Hum. Biol. 11:359-366, 1999. Copyright 1999 Wiley-Liss, Inc.

Haplotype and allele frequencies for three genes of the dopaminergic system in South American Indians

Haplotype and allele frequencies for the dopamine D2 receptor gene (DRD2), dopamine D4 receptor gene (DRD4), and dopamine transporter protein gene (SLC6A3) were determined in 135 individuals from five Brazilian Indian tribes, and the results integrated with those previously presented for this ethnic group. DRD2 and DRD4 were highly polymorphic. Haplotypes including TaqI A1 at DRD2, and the seven repeat allele at DRD4 were the most frequent variants, while the SLC6A3 locus was monomorphic for the 10 repeat allele in South American Indians. Genetic distances and the corresponding neighbor-joining tree indicated a geographic dichotomy between North + Central American and South American natives, with the exception of the Wai Wai, who live north of the Amazon river and are grouped in the northern cluster. G(ST) estimates from these genes vary between 0.05 and 0.11 for North and South America, respectively, indicating a higher degree of differentiation of the latter groups. These results are in accordance with previous genetic data on other systems, as well as with the history and biodemographical data of South American Indians. Am. J. Hum. Biol. 12:638-645, 2000. Copyright 2000 Wiley-Liss, Inc.

Genetic structure of Quechua-speakers of the Central Andes and geographic patterns of gene frequencies in South Amerindian populations

A sample of 141 Quechua-speaking individuals of the population of Tayacaja, in the Peruvian Central Andes, was typed for the following 16 genetic systems: ABO, Rh, MNSs, P, Duffy, AcP1, EsD, GLOI, PGM1, AK, 6-PGD, Hp, Gc, Pi, C3, and Bf. The genetic structure of the population was analyzed in relation to the allele frequencies available for other South Amerindian populations, using a combination of multivariate and multivariable techniques. Spatial autocorrelation analysis was performed independently for 13 alleles to identify patterns of gene flow in South America as a whole and in more specific geographic regions. We found a longitudinal cline for the AcP1*a and EsD*1 alleles which we interpreted as the result of an ancient longitudinal expansion of a putative ancestral population of modern Amerindians. Monmonnier's algorithm, used to identify areas of sharp genetic discontinuity, suggested a clear east-west differentiation of native South American populations, which was confirmed by analysis of the distribution of genetic distances. We suggest that this pattern of genetic structures is the consequence of the independent peopling of western and eastern South America or to low levels of gene flow between these regions, related to different environmental and demographic histories.