Genomic ancestry in urban Afro-Brazilians

Brazil is the result of interethnic crosses of European, African and Amerindian populations. Allelic frequencies for seven STR loci (TH01, TPOx, CSF1PO, vWA, FES/FPS, F13A1 and CD4), obtained from a sample of 70 individuals identified as Afro-Brazilian and 150 as mulatto, are presented here. Based on the frequencies of these genetic markers, estimates of interethnic admixture showed 62%, 26% and 12% of European, African and Amerindian contribution, respectively, for the mulatto sample and 37% and 63% of European and African contribution, respectively, for the Afro-Brazilian sample.     

Genomic ancestry in urban Afro-Brazilians

Brazil is the result of interethnic crosses of European, African and Amerindian populations. Allelic frequencies for seven STR loci (TH01, TPOx, CSF1PO, vWA, FES/FPS, F13A1 and CD4), obtained from a sample of 70 individuals identified as Afro-Brazilian and 150 as mulatto, are presented here. Based on the frequencies of these genetic markers, estimates of interethnic admixture showed 62%, 26% and 12% of European, African and Amerindian contribution, respectively, for the mulatto sample and 37% and 63% of European and African contribution, respectively, for the Afro-Brazilian sample.     

Maximum likelihood estimates of admixture in northeastern Mexico using 13 short tandem repeat loci

Tetrameric short tandem repeat (STR) polymorphisms are widely used in population genetics, molecular evolution, gene mapping and linkage analysis, paternity tests, forensic analysis, and medical applications. This article provides allelic distributions of the STR loci D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, D7S820, CSF1PO, TPOX, TH01, and D16S539 in 143 Mestizos from Northeastern Mexico, estimates of contributions of genes of European (Spanish), American Indian and African origin in the gene pool of this admixed Mestizo population (using 10 of these loci); and a comparison of the genetic admixture of this population with the previously reported two polymorphic molecular markers, D1S80 and HLA‐DQA1 (n = 103). Genotype distributions were in agreement with Hardy‐Weinberg expectations (HWE) for almost all 13 STR markers. Maximum likelihood estimates of admixture components yield a trihybrid model with Spanish, Amerindian, and African ancestry with the admixture proportions: 54.99% ± 3.44, 39.99% ± 2.57, and 5.02% ± 2.82, respectively. These estimates were not significantly different from those obtained using D1S80 and HLA‐DQA1 loci (59.99% ± 5.94, 36.99% ± 5.04, and 3.02% ± 2.76). In conclusion, Mestizos of Northeastern Mexico showed a similar ancestral contribution independent of the markers used for evolutionary purposes. Further validation of this database supports the use of the 13 STR loci along with D1S80 and HLA‐DQA1 as a battery of efficient DNA forensic markers in Northeastern Mestizo populations of Mexico. Am. J. Hum. Biol. 14:429–439, 2002. © 2002 Wiley‐Liss, Inc.     

Genetic admixture in three mexican mestizo populations based on D1S80 and HLA‐DQA1 Loci

This study compares genetic polymorphisms at the D1S80 and HLA‐DQA1 loci in three Mexican Mestizo populations from three large states (Nuevo León, Jalisco, and the Federal District). Allele frequency distributions are relatively homogenous in the three samples; only the Federal District population shows minor differences of the HLA‐DQA1 allele frequencies compared with the other two. In terms of genetic composition, these Mestizo populations show evidence of admixture with predominantly Spanish‐European (50–60%) and Amerindian (37–49%) contributions; the African contribution (1–3%) is minor. Together with the observation that in Nuevo León, the admixture estimates based on D1S80 and HLA‐DQA1, are virtually the same as those reported earlier from blood group loci, suggests that DNA markers, such as D1S80 and HLA‐DQA1 are useful for examining genetic homogeneity/heterogeneity across Mestizo populations of Mexico. The inverse relationship of the proportion of gene diversity due to population differences (G_st) to within population gene diversity (H_s) is also consistent with theoretical predictions, supporting the use of these markers for population genetics studies. Am. J. Hum. Biol. 14:257–263, 2002. © 2002 Wiley‐Liss, Inc.     

Genetic variability and linkage disequilibrium within the HLA-DP region: analysis of 15 different populations

In order to understand the forces governing the evolution of the genetic diversity in the HLA-DP molecule, polymerase chain reaction (PCR)-based methods were used to characterize genetic variation at the DPA1 and DPB1 loci encoding this heterodimer on 2,807 chromosomes from 15 different populations including individuals of African, Asian, Amerindian, Indian and European origin. These ethnically diverse samples represent a variety of population substructures and include small, isolated populations as well as larger, presumably admixed populations. Ten DPA1 and 39 DPB1 alleles were identified and observed on 87 distinct DP haplotypes, 34 of which were found to be in significant positive linkage disequilibrium in at least one population. Some haplotypes were found in all ethnic groups while others were confined to a single ethnic group or population. Strong positive global linkage disequilibrium (Wn) between DPA1 and DPB1 was present in all 15 populations. The African populations displayed the lowest values of Wn whereas the Amerindian populations displayed near absolute disequilibrium. Analysis of the distribution of haplotypes using the normalized deviate of the Ewens-Watterson homozygosity statistic, F, suggests that DP haplotypes encoding the functional heterodimer are subject to much lower degrees of balancing selection than other loci within the HLA region. Finally, neighbor joining tree analyses demonstrate the power of haplotype diversity for inferring the relationships between the different populations.     

Population structure and admixture in Cerro Largo, Uruguay, based on blood markers and mitochondrial DNA polymorphisms.

Recent studies of the Uruguayan population revealed different amounts of Amerindian and African genetic contributions. Our previous analysis of Afro-Uruguayans from the capital city of the Department of Cerro Largo showed a high proportion of African genes, and the effects of directional mating involving Amerindian women. In this paper, we extended the analysis to a sample of more than 100 individuals representing a random sample of the population of the whole Department. Based on 18 autosomal markers and one X-linked marker, we estimated 82% European, 8% Amerindian, and 10% African contributions to their ancestry, while from seven mitochondrial DNA site-specific polymorphic markers and sequences of hypervariable segment I, we determined 49% European, 30% Amerindian, and 21% African maternal contributions. Directional matings between Amerindian women and European men were detected, but differences involving Africans were not significant. Data about the specific origins of maternal lineages were also provided, and placed in a historical context.     

Assessment of genetic ancestry and population substructure in Costa Rica by analysis of individuals with a familial history of mental disorder

The population of Costa Rica has been considered valuable for locating susceptibility genes of complex disorders because of historical events and a gradual admixture process. We present an assessment of 426 unrelated individuals with a familial history of mental disorder and with ancestors born in the Central Valley, genotyped at 730 microsatellites to evaluate genetic diversity, ancestry, and substructure at the general and regional population levels using quantitative methods. Low population substructure was found. Estimated mean ancestry proportions were 54%, 32%, and 13% for European, Amerindian, and African components, respectively, with some regional variation. The F(ST) values obtained confirm the largest genetic similarity to Europeans. Subdivision of the Amerindians into individual populations revealed strong similarity to Chibchan groups. Analysis of the African ancestry showed high similarity to West and Central African populations. Gene ancestries from other African areas were also detected, probably resulting from ancestral admixture within Africa prior to colonial times. Our analyses show, in an ethnohistorical-genetic context, that gene flow and admixture are important components of Costa Rican population history. The results confirm the need to consider the particular regional genetic structure, the effects of genetic drift and the ancestry when designing and interpreting investigations of genetic traits in this population.     

2p24.2 (rs7552) is a susceptibility locus for nonsyndromic cleft lip with or without cleft palate in the Brazilian population

The population of Brazil is highly admixed, with each individual showing variable levels of Amerindian, European and African ancestry, which may interfere in the genetic susceptibility of known risk loci to nonsyndromic cleft lip with or without cleft palate (NSCL±P). Here, we investigated 5 reported genome‐wide loci for NSCL±P in an ancestry‐structured case‐control study containing 1697 Brazilian participants (831 NSCL±P and 866 healthy controls). SNPs rs7552 in 2q24.2, rs8049367 in 16p13.3, rs1880646, rs7406226, rs9891446 in 17p13, rs1588366 in 17q23.2 and rs73039426 in 19q13.11 were genotyped using TaqMan allelic discrimination assays and genomic ancestry was estimated using a panel of 40 biallelic short insertion/deletion polymorphic markers informative of the Brazilian population. Logistic regression analysis of the single‐markers revealed rs7552 in 2p24.2 as a susceptibility risk marker for NSCL±P, yielding an odds ratio (OR) of 1.71 (95% confidence interval (CI): 1.31‐2.24, P = 9 × 10^?6) in the homozygous state. Several SNP‐SNP interactions containing rs7552 reached significance after adjustment for multiple tests (both Bonferroni assumption and 1000 permutation test), with the most significant interaction involving the 3‐loci among rs7552, rs9891446 and rs73039426 (P = 6.1 × 10^?9 and p_{1000 permutation} = 0.001). Our study is the first to support the association of rs7552 in 2p24.2 with NSCL±P in the highly admixed Brazilian population.     

Predominant human herpesvirus 6 variant A infant infections in an HIV‐1 endemic region of Sub‐Saharan Africa

Human herpesvirus 6, HHV‐6, commonly infects children, causing febrile illness and can cause more severe pathology, especially in an immune compromised setting. There are virulence distinctions between variants HHV‐6A and B, with evidence for increased severity and neurotropism for HHV‐6A. While HHV‐6B is the predominant infant infection in USA, Europe and Japan, HHV‐6A appears rare. Here HHV‐6 prevalence, loads and variant genotypes, in asymptomatic compared to symptomatic infants were investigated from an African region with endemic HIV‐1/AIDS. DNA was extracted from blood or sera from asymptomatic infants at 6 and 18 months age in a population‐based micronutrient study, and from symptomatic infants hospitalised for febrile disease. DNA was screened by qualitative and quantitative real‐time PCR, then genotyped by sequencing at variable loci, U46 (gN) and U47 (gO). HIV‐1 serostatus of infants and mothers were also determined. HHV‐6 DNA prevalence rose from 15% to 22% (80/371) by 18 months. At 6 months, infants born to HIV‐1 positive mothers had lower HHV‐6 prevalence (11%, 6/53), but higher HCMV prevalence (25%, 17/67). HHV‐6 positive febrile hospitalized infants had higher HIV‐1, 57% (4/7), compared to asymptomatic infants, 3% (2/74). HHV‐6A was detected exclusively in 86% (48/56) of asymptomatic HHV‐6 positive samples genotyped. Co‐infections with both strain variants were linked with higher viral loads and found in 13% (7/56) asymptomatic infants and 43% (3/7) HIV‐1 positive febrile infants. Overall, the results show HHV‐6A as the predominant variant significantly associated with viremic infant‐infections in this African population, distinct from other global cohorts, suggesting emergent infections elsewhere. J. Med. Virol. 81:779–789, 2009. © 2009 Wiley‐Liss, Inc.     

HLA genes in Barranquilla (North Colombia): Searching for cryptic Amerindian genes

America First Inhabitants population (Amerindians, Na Dene and Eskimos) underwent a drastic population reduction and gene exchange after Europeans and Africans arrival after 1492 AD. Barranquilla population may be a good model to study present day population admixture in South America. HLA-A, -B and -DRB1 DNA typing has been performed in 188 unrelated individuals originated in the area and speak Spanish language; they showed apparent European/African and mixed characters. HLA genetic European/African features were found and only 1.85% Amerindian one. This contrasts with neighboring Cuban population where 10% HLA Amerindian characters appear.     

Amerindian ancestry in Argentina is associated with increased risk for systemic lupus erythematosus

Previous studies have demonstrated that in admixed populations, West African ancestry is associated with an increased prevalence of systemic lupus erythematosus (SLE). In the current study, the effect of Amerindian ancestry in SLE was examined in an admixed population in Argentina. The Argentine population is predominantly European with approximately 20% Amerindian admixture, and a very small (<2%) contribution from West Africa. The results indicate that Amerindian admixture in this population is associated with a substantial increase in SLE susceptibility risk (Odds Ratio=7.94, P=0.00006). This difference was not due to known demographic factors, including site of collection, age and gender. In addition, there were trends towards significance for Amerindian ancestry influencing renal disease, age of onset and anti-SSA antibodies. These studies suggest that populations with Amerindian admixture, like those with West African admixture, should be considered in future studies to identify additional allelic variants that predispose to SLE.     

The distributions of HLA‐A,HLA‐B,HLA‐C,HLA‐DRB1 and HLA‐DQB1 allele and haplotype at high‐resolution level in Zhejiang Han population of China

The distributions of HLA allele and haplotype are variable in different ethnic populations and the data for some populations have been published. However, the data on HLA‐C and HLA‐DQB1 loci and the haplotype of HLA‐A, HLA‐B, HLA‐C, HLA‐DRB1 and HLA‐DQB1 loci at a high‐resolution level are limited in Zhejiang Han population, China. In this study, the frequencies of the HLA‐A, HLA‐B, HLA‐C, HLA‐DRB1 and HLA‐DQB1 loci and haplotypes were analysed among 3,548 volunteers from the Zhejiang Han population using polymerase chain reaction sequencing‐based typing method. Totals of 51 HLA‐A, 97 HLA‐B, 45 HLA‐C, 53 HLA‐DRB1 and 27 HLA‐DQB1 alleles were observed. The top three frequent alleles of HLA‐A, HLA‐B, HLA‐C, HLA‐DRB1 and HLA‐DQB1 loci were A*11:01 (23.83%), A*24:02 (17.16%), A*02:01 (11.36%); B*40:01 (14.08%), B*46:01 (12.20%), B*58:01 (8.50%); C*07:02 (18.25%), C*01:02:01G (18.15%), C*03:04 (9.88%); DRB1*09:01 (17.52%), DRB1*12:02 (10.57%), DRB1*15:01 (9.70%); DQB1*03:01 (22.63%), DQB1*03:03 (18.26%) and DQB1*06:01 (10.88%), respectively. A total of 141 HLA‐A‐C‐B‐DRB1‐DQB1 haplotypes with a frequency of ≥0.1% were found and the haplotypes with frequency greater than 3% were A*02:07‐C*01:02:01G‐B*46:01‐DRB1*09:01‐DQB1*03:03 (4.20%), A*33:03‐C*03:02‐B*58:01‐DRB1*03:01‐DQB1*02:01 (4.15%), A*30:01‐C*06:02‐B*13:02‐DRB1*07:01‐DQB1*02:02 (3.20%). The likelihood ratios test for the linkage disequilibrium of two loci haplotypes was revealed that the majority of the pairwise associations were statistically significant. The data presented in this study will be useful for searching unrelated HLA‐matched donor, planning donor registry and for anthropology studies in China.     

High prevalence of GB virus C strains genetically related to strains with Asian origin in Nicaraguan hemophiliacs

The presence of hepatitis GB virus C (GBV-C), also known as hepatitis G virus (HGV), and hepatitis C virus (HCV) were investigated in sera from 45 hemophiliacs from nine locations in Nicaragua using a nested polymerase chain reaction (PCR). Primers used to detect GBV-C and HCV derived from the helicase region and 5′UTR, respectively. Seventeen (38%) patients were positive for GBV-C RNA in serum by PCR. Twelve (27%) patients were positive for HCV RNA by PCR. Six (13%) of these were coinfected with GBV-C. Anti-HCV was detected in all the 12 HCV RNA positive hemophiliacs and in another 14 (31%) individuals, in whom GBV-C RNA was found in 2. Ten patients (22%) lacked markers for both GBV-C and HCV. The mean age of the patients positive for GBV-C but negative for HCV by PCR was significantly lower than for those negative for GBV-C but positive for HCV by PCR (P < 0.05; Student's t-test), indicating that the risk for this group of hemophiliacs to acquire GBV-C infection is higher as compared to the risk of acquiring HCV infection. Eleven GBV-C strains were sequenced in the 5′UTR. Sequence comparison to previously published GBV-C strains revealed that all 11 strains were more similar to Asian strains than to strains of European and African origin. Sequences in the NS5-B region were available for 8 HCV strains, all of which were found to belong to genotype 1a. The similarity of the Nicaraguan GBV-C strains to strains from Asia indicates that the GBV-C strains in the region presumably have an Amerindian origin. It is also considered that the HTLV II strains in the New World aboriginal populations are ancient and brought there by the ancestral Amerindian populations from Asia. Further, the genotype F of hepatitis B virus, known to represent the strains in populations with Amerindian background, predominates in Central American populations with Hispanic background. It remains to be clarified why Amerindian strains of GBV-C as well as of HBV predominate also in populations with mixed ethnic background in Central America. J. Med. Virol. 52:149–155, 1997. © 1997 Wiley-Liss, Inc.     

Genetic structure and affinity among eight ethnic populations of Eastern India: based on 22 polymorphic DNA loci.

The nature and extent of genetic variation at 22 polymorphic DNA loci, belonging to three distinct classes, especially, 12 STR loci (D3S1358, vWA, FGA, D5S818, D13S317, D7S820, D8S1179, D21S11, D18S51, HPRTB, F13B, LPL), four VNTR loci (D1S7, D4S139, D5S110, D17S79), and six coding loci (HLDQA1, LDLR, GYPA, HBGG, D7S8, GC) were investigated among eight population groups of West Bengal and Manipur regions of India. Of these, two groups from West Bengal belong to Caucasoid and six (one in WB and five in Manipur) belong to Mongoloid stock. Both STR and the expressed loci show wide diversity among the eight populations. For example, Manipur Muslims show differences in allele frequency when compared to four other regional populations. Similarly, Garo, one of the Mongoloid populations of West Bengal, differ in allele frequency from their counterparts in the Manipur region. Departure from Hardy-Weinberg expectations was observed at certain loci in a few populations (e.g., D21S1137 in Kayastha and Brahmin, HUM F13B in Meitei). Heterozygosity values were higher for Caucasoid than Mongoloid groups. The overall gene differentiation (GST) for STR loci is higher (5.3%) than for those at the expressed region (4.6%). The clustering pattern of the eight populations differs with respect to different classes of genetic markers used. The dendrograms based on six coding loci (HLDQA1, LDLR, GYPA, HBGG, D7S8, GC) differs from those based on STR and VNTR markers. Caucasoid and Mongoloid groups form different clusters and Manipur Muslims are distinct from others. The clustering pattern corresponded with the spatial and ethnic affiliations of the populations. Using different classes of DNA loci at the coding and noncoding region will help to better understand the influence of population structure variables on the genetic structure of populations.     

Dissimilarities in the process of formation of curiaú, a semi‐isolated Afro‐Brazilian population of the Amazon region

The genetic consequences of the social policy of the past in relation to the formation of Afro‐Brazilian societies are interesting and have been studied at various biological levels (classical polymorphisms and the mitochondrial and nuclear levels. These allow the estimation of the contribution of African genes and the participation of other ethnic groups in the formation of these communities. With this objective, uniparental systems of exclusively maternal (mtDNA) or paternal (Y‐DNA) inheritance in the Curiaú community were analyzed. The results demonstrate a differential contribution of the maternal and paternal genetic systems. Thirty‐three sequences were identified by mtDNA analysis; 53% showing an African and 47% an Amerindian origin. For the paternal system, 57% were of African, 37% of European, and 6% of Amerindian origin. Am. J. Hum. Biol. 14:440–447, 2002. © 2002 Wiley‐Liss, Inc.     

Gene Admixture in the Costa Rican Population

The general population of Costa Rica has sometimes been considered to be the product of an amalgamation of groups of diverse origin. To determine the magnitude of accumulated admixture since Spanish colonization, 11 classic genetic markers were analyzed in a total of 2196 individuals originating from five distinct regions of the country. A maximum likelihood approach was used. The proportions of genes of European, Amerindian and African ancestry were found to be 61%, 30% and 9% of the total population, respectively. Variation was observed at a regional level, with an increased European influence in the North (66%) and Central (65%) regions. Meanwhile an increase in Amerindian ancestry was found in the South (38%), and a higher incidence in the contribution of African genes was detected in the coastal regions (13% in the Atlantic and 14% in the North Pacific). A principal component (PC) analysis showed that 76% of the existing variability can be explained by the first two PCs, which is in agreement with the variations observed in the admixture process by geographic area. It has been concluded that the Costa Rican population is truly trihybrid, similar to populations in other Latin American countries; however, it differs from them fundamentally by the proportion of gene flow from ancestral populations.     

Extended HLA haplotypes in a Carib Amerindian population: the Yucpa of the Perija Range.

Eleven MHC loci haplotypes have been defined among a Carib speaking Amerindian population; the Yucpa, inhabiting the northern section of the Perija Range, on the limits between Colombia and Venezuela. This tribe has been known with the name of "Motilones mansos" and is located close to the Chibcha-Paeze speaking Bari or "Motilones bravos." Seventy-three full blooded Yucpa living at the villages of Aroy, Marewa, and Peraya, were selected using a genealogy previously collected by an anthropologist and tested for Bf-C4AB complement allotypes and by serology, high resolution PCR-SSO and SBT typing for HLA class 1 and class 2 alleles. Combinations of 6 HLA-A, 6 HLA-B, 5 HLA-C, 1 Bf, 3 C4AB, 3 DQA1, 3DQB1 and 2 DPA1 and 2 DPB1 alleles present in this population originate 17 different haplotypes, 3 of which represent 63% of the haplotypic constitution of the tribe. The presence of 13 individuals homozygous for 11-loci haplotypes corroborates the existence of the following allelic combinations: DRB1*0411 DQA1*03011 DQB1*0302 DPA1*01 DPB1*0402 with HLA-A*6801 C*0702 B*3909 BfS C4 32 (f = 0.3372) or with A*0204 C*0702 B*3905 (f = 0.1977) and a third haplotype which differs only in DRB1*0403 and A*2402 (f = 0.0930). The results demonstrate the isolation of the tribe and the existence of high frequencies of a reduced number of "Amerindian" ancestral and novel class 1 and class 2 alleles (B*1522, DRB1*0807) with significant linkage disequilibria. These results will be useful to test the hypothesis that differentiation of Amerindian tribal groups will have to rely on haplotypes and micropolymorphism rather than allelic lineage frequencies due to the uniformity shown thus far by the putative descendants of the original Paleo-Indians.     

X‐chromosomal genetic diversity and linkage disequilibrium patterns in Amerindians and non‐Amerindian populations

Objectives: We report X‐chromosomal linkage disequilibrium (LD) patterns in Amerindian (Kogi, Wayuu, and Zenu) and admixed Latin American (Central Valley of Costa Rica and Southern Brazilian Gaucho) populations. Methods: Short tandem repeats (STRs) widespread along the X‐chromosome were investigated in 132 and 124 chromosomes sampled from the Amerindian tribes and the admixed Latin American populations, respectively. Diversity indexes (gene diversity and average numbers of alleles per locus) were estimated for each population and the level of LD was inferred with an exact test. Results: The Amerindian populations presented lower genetic diversity and a higher proportion of loci in LD than the admixed ones. Two haplotype blocks were identified in the X‐chromosome, both restricted to the Amerindians. The first involved DXS8051 and DXS7108 in Xp22.22 and Xp22.3, while the second found only among the Kogi, included eight loci in a region between Xp11.4 and Xq21.1. Conclusions: In accordance to previous work done with other populations, human isolates, such as Amerindian tribes, seem to be an optimal choice for the implementation of association studies due to the wide extent of LD which can be found in their gene pool. On the other hand, the low proportion of loci in LD found in both admixed populations studied here could be explained by events related to their history and similarities between the allele frequencies in the parental stocks. Am. J. Hum. Biol., 2011. © 2011 Wiley‐Liss, Inc.     

Genetic composition of Brazilian population samples based on a set of twenty‐eight ancestry informative SNPs

Ancestry informative SNPs can be useful to estimate individual and population biogeographical ancestry. Brazilian population is characterized by a genetic background of three parental populations (European, African, and Brazilian Native Amerindians) with a wide degree and diverse patterns of admixture. In this work we analyzed the information content of 28 ancestry‐informative SNPs into multiplexed panels using three parental population sources (African, Amerindian, and European) to infer the genetic admixture in an urban sample of the five Brazilian geopolitical regions. The SNPs assigned apart the parental populations from each other and thus can be applied for ancestry estimation in a three hybrid admixed population. Data was used to infer genetic ancestry in Brazilians with an admixture model. Pairwise estimates of F_st among the five Brazilian geopolitical regions suggested little genetic differentiation only between the South and the remaining regions. Estimates of ancestry results are consistent with the heterogeneous genetic profile of Brazilian population, with a major contribution of European ancestry (0.771) followed by African (0.143) and Amerindian contributions (0.085). The described multiplexed SNP panels can be useful tool for bioanthropological studies but it can be mainly valuable to control for spurious results in genetic association studies in admixed populations. Am. J. Hum. Biol., 2010. © 2009 Wiley‐Liss, Inc.     

Admixture estimates for Churuguara, a Venezuelan town in the State of Falcón

BACKGROUND: The present Venezuelan population is the admixture product of Amerindians, Europeans and Africans, a process which was not homogeneous over the country. Blood groups, STRs and VNTRs, specifically D1S80, have been used successfully in admixture studies, but few have been made in Venezuela. AIM: This study aims to estimate the admixture components of Churuguara, Venezuela, and to evaluate the genetic relationship of this population with other Venezuelan as well as worldwide populations through principal component analysis and the study of dendrograms based on genetic distances. SUBJECTS AND METHODS: Gene frequencies of blood groups ABO and Rh (only anti D), of STRs VWA, F13A01, FES/FPS and VNTR D1S80 were studied in a sample of 60 individuals born in Churuguara, a Venezuelan town of admixed ancestry in the State of Falc6n. Admixture was estimated with Chakraborty's gene identity method, and Nei's standard genetic distance was used to build two dendrograms with the neighbour-joining approach, one based on the three STRs and the other based only on D1S80. Principal component analyses with the gene frequencies of these markers were also performed. RESULTS: The frequency of allele ABO*O was 0.788, of ABO*A was 0.187 and of RH*D was 0.74. D1S80 showed 16 different alleles with a heterozygosity of 0.880, whilst the three STRs showed only eight different alleles and heterozygosities between 0.733 and 0.797. The estimates of admixture obtained in this analysis were 52.5% for the Spanish parental group, 27.6% for the African and 19.9% for the Amerindian. Comparison of Churuguara with other Latin American populations shows that its African component is not as high as that observed in Colombian Choco, but it is higher than that observed in other samples from Colombia, Chile and Maracaibo (Venezuela). CONCLUSIONS: Results of the admixture analysis are consistent with those obtained with two dendrograms and principal component analyses, suggesting that the strong initial Amerindian component of 500 years ago has been diluted by the continuous flow of European genes, mainly Spanish, to this region.