Biomedical subjects

J F Guerreiro

Publications and source records attributed to J F Guerreiro.

At least 19 recordsLinked to original sources

PubMed2001

The split of the Arara population: comparison of genetic drift and founder effect.

The total genetic diversity of the Amerindian population is as high as that observed for other continental human populations because a large contribution from variation among tribes makes up for the low variation within tribes. This is attributed mainly to genetic drift acting on small isolated populations. However, a small founder population with a low genetic diversity is another factor that may contribute to the low intratribal diversity. Small founder populations seem to be a frequent event in the formation of new tribes among the Amerindians, but this event is usually not well recorded. In this paper, we analyze the genetic diversity of the Arara of Laranjal village and the Arara of Iriri village, with respect to seven tandem repeat autosomic segments (D1S80, ApoB, D4S43, vW1, vW2, F13A1 and D12S67), two Y-chromosome-specific polymorphisms (DYS19 and DYS199), and mitochondrial DNA (mtDNA) markers (restriction fragment length polymorphisms and sequencing of a segment of the D loop region). The occurrence of a single Y chromosome and mtDNA haplotype, and only 1-4 alleles of the autosomic loci investigated, corroborates historic and demographic records that the Arara of Iriri were founded by a single couple of siblings who came from the Arara of Laranjal, the largest group. Notwithstanding this fact, the genetic distance and the molecular variance between the two Arara villages were greater than those observed between them and other Amazonian tribes, suggesting that the microevolutionary process among Brazilian Amerindians may be misinterpreted if historic demographic data are not considered.

Brazil↗

PubMed2000

Gene frequencies of the HPA-3 and HPA-5 platelet antigen alleles among the Amerindians.

Platelet antigens are of importance in several clinical situations and in population genetics. Data are scarce on allele frequencies in ethnic groups other than whites, Asians and African Americans. The frequencies of the alleles of the systems HPA-3 and HPA-5 were determined using the allele-specific restriction enzyme for five South American Amerindian populations and compared with those obtained for Afro-Americans, Japanese and whites from Brazil. The frequency of the HPA-3a allele among the Amerindians as a group did not differ from the values obtained for the other populations. However, differences were observed among the Amerindians, varying from 0.27 to 0.75, the highest frequency thus far observed for a population of Asian origin. Only the HPA-5a allele was found among 130 Amerindian chromosomes. The determination of gene frequencies of the HPA systems in different populations allows inference of gene flows and genetic constitution of populations and the estimation of the risk of platelet-specific alloimmunization.

Alleles↗

PubMed2000

Ethnic heterogeneity of the factor XIII Val34Leu polymorphism.

A polymorphism in the coagulation factor XIII gene (FXIII Val34Leu) has been recently described to confer protection for arterial and venous thrombosis and to predispose to intracerebral hemorrhage. At present it is known that FXIII Val34Leu is prevalent in Caucasians, but information upon its distribution in different ethnic groups is scarce. We investigated the prevalence of FXIIIVal34Leu in 450 unrelated subjects of four ethnic groups: 97 Caucasians (Brazilians of European descent and Portuguese), 149 Blacks (Brazilians, and Africans from Cameroon, Zaire and Angola), 40 Asians (Japanese descendents) and 164 Amerindians from South America. PCR amplification of exon 2 of FXIII gene followed by MseI restriction-digestion was employed to define the genotypes. FXIIIVal34Leu was detected in 44.3% of the Caucasians, in 28.9% of the Blacks, in 2.5% of the Asians and in 51.2% of the Amerindians. These data confirm that FXIII Val34Leu is highly prevalent in Caucasians and indicate that it is rarer in populations of African origin. The very high frequency among Amerindians indicates that FXIII Val34Leu is not absent among Asians, and since it has a very low prevalence in Japanese, a heterogeneity in its distribution in Asia may be inferred. Taken together, our data showed that FXIII Val34Leu exhibits a significant ethnic heterogeneity, a finding that is relevant for studies relating this polymorphism with thrombotic and bleeding disorders.

Factor XIII↗

PubMed1999

Born to clot: the European burden.

Venous thrombosis is a common problem, predominantly afflicting people of European origin. This European predisposition has been explained to some extent by the recent characterization of factor V Leiden, and the G20210A prothrombin variant. Although it is clear that factor V Leiden is largely confined to Europeans, the world distribution of the prothrombin variant is not known. We have analysed samples from 22 different non-European countries and shown that this prothrombin variant is very rare outside Europe: one case occurring in India. The reason for the confined distribution of these two mutations is unclear.

Africa↗

PubMed1998

Analysis of the 677 C-->T mutation of the methylenetetrahydrofolate reductase gene in different ethnic groups.

A recently described mutation in the methylenetetrahydrofolate reductase (MTHFR) gene (a C to T transition at nucleotide 677) is associated with a thermolabile phenotype and decreased enzyme activity. In homozygotes, the mutation is also related to hyperhomocysteinemia and increased risk for atherosclerotic disease and (apparently) venous thrombosis. The prevalence of this mutation in different human populations is unknown. We have investigated the frequency of the 677 C-->T mutation in the MTHFR gene in 337 individuals (674 chromosomes) belonging to four ethnic groups: Whites, African and Brazilian Blacks, Asians and Amerindians. The frequencies of the positive allele among Whites and Asians were similar to those previously reported for Caucasian populations. The positive allele seems to be slightly rarer among the Amerindians (frequency 24.0%) in comparison to Whites and Asians, with a heterogeneous distribution among the five Indian tribes analysed. In contrast, the mutation has a very low prevalence in Blacks, especially among the African Blacks, for whom the mutation was absent in homozygosity. Our data indicate that the 677 C-->T MTHFR mutation has a significantly heterogeneous distribution among different ethnic groups, a fact that may contribute to explain geographical or racial differences in the risk for vascular disease.

Asian People↗

PubMed1998

Heterogeneity of the O alleles at the blood group ABO locus in Amerindians.

BACKGROUND AND OBJECTIVES: Amerindians are blood group O, but the distribution of the various O alleles is unknown. Their ABO genotypes were compared with samples from other Brazilian ethnic groups. MATERIALS AND METHODS: Genomic DNA was examined by PCR-RFLP analysis, PCR-SSP and direct sequencing. RESULTS: An unusual allele distribution was found, with 91% of the O alleles being O1variant. Almost half of these alleles had an additional novel mutation (G542A), which was also detected in a few other Brazilian and European samples. The O alleles correlated completely with ABO-related haplotypes previously determined by Southern blot. CONCLUSION: The three Amerindian tribes represent a homogeneous (ABO blood group) population, except for the G542A mutation. The presence of this mutation in all other populations examined suggests that it originated before the migration of man into America.

ABO Blood-Group System↗

PubMed1998

D1S80 polymorphism in Amerindians from the Amazon region of Brazil.

The allele frequency distribution at the D1S80 locus (pMCT118) was analyzed in five Amerindian tribes from the Brazilian Amazon (Zoé, Awá-Guajá, Urubú-Kaapór, Katuena, and Xikrin of Bacajá) and was compared with distributions described for other worldwide populations. Nine different segregating alleles were identified in a sample of 139 individuals; alleles *18, *25, and *30 predominated in all tribes. Although the tribes are usually characterized by a low within-population diversity, they have a high interpopulational diversity, probably because of genetic drift acting on small isolated populations. Our data are similar to data for other Brazilian Amerindian tribes; these were combined for comparison with other human populations. Brazilian Amerindians are similar to the Pehuenche from Chile and to North American natives. However, the closest similarity was observed between Brazilian Amerindians and Polynesian populations (Samoans), probably reflecting common ancestry. Brazilian Amerindians and Asian populations have some similarities in terms of allele distribution (high frequencies of alleles *18 and *30), but the values of heterozygosity and the number of alleles are higher in Asians. Brazilian Amerindians are also clearly different from Europeans.

Alleles↗

PubMed1997

Molecular analysis of the O alleles at the blood group ABO locus in populations of different ethnic origin reveals novel crossing-over events and point mutations.

The blood group ABO genotypes of 138 group O individuals with three different ethnic origins in Brazil were determined, including Whites, Blacks and Amerindians. Several previously undescribed O alleles were found, predominantly in the Black group, in which about a third of the samples did not conform to previously known O allele structures. It has been well documented for the first time that some new alleles can arise from crossing-over events between known alleles in the ABO system. This was made possible by both restriction endonuclease analysis and direct sequencing of exons 3-7 in the ABO gene. The anticipated relatively high frequency of some of these new alleles in certain populations, necessitates great care when interpreting results from existing genotype screening methods.

ABO Blood-Group System↗

PubMed1997

Coding versus intron variability: extremely polymorphic HLA-DRB1 exons are flanked by specific composite microsatellites, even in distant populations.

Although microsatellite typing is the dominant method in genome research and indirect gene diagnosis, precise relationships of exonic and adjacent simple repeat polymorphisms are not known. We investigated exon 2 sequences of HLA-DRB1 genes and their neighbouring (GT)n(GA)m repeats including the intervening single copy spacer. DRB1 is the most polymorphic protein-coding locus in man and all vertebrates investigated. The entire DRB1 variability exists in exon 2. DRB1 genes in different haplotype groups (DR1, DR51, DR52, DR8 and DR53) are accompanied by characteristic modifications of the (GT)n(GA)m block (3' to group-specific single copy spacers). Among more than 520 alleles analysed, > 100 different types of microsatellites were observed. The perfect (GT)n and (GA)m blocks vary in length and may be partly 'degenerated', mostly in a subgroup-specific manner. Interestingly, the extent of microsatellite diversity varies in given DRB1 alleles. While the microsatellites of the DR7, DR9 alleles and in the DR1 group are virtually invariant, in DR4 and DR13, in particular, simple repeats appear hypervariable with at least 15 or 17 different length alleles, respectively. Comparing Caucasians, Bushmen and South American Indians, the microsatellite variation in identical DRB1 alleles (e.g. DRB1*0102, 03011, 1302) is smaller than within any of the DR groups in Caucasians. Taken together, extremely polymorphic DRB1 exons evolve in concert with certain variants of an exceptionally well-preserved microsatellite.

Cloning, Molecular↗

PubMed1997

Gene frequencies of the HPA-1 and HPA-2 platelet antigen alleles among the Amerindians.

BACKGROUND AND OBJECTIVES: Platelet-specific alloantigens are important in neonatal alloimmune thrombocytopenia, posttransfusion purpura, refractoriness to platelet transfusions, and population genetics. Data are scarce on allele frequencies in ethnic groups other than whites and Asians. MATERIALS AND METHODS: Using allele-specific restriction enzyme analysis, we studied the distribution of HPA-1 and HPA-2 alleles in six Brazilian Amazon tribes of Amerindians, belonging to five different language stocks. We compared these with the values obtained for blacks and whites. RESULTS: Only the HPA-1a allele was found among 132 Amerindian chromosomes, compared with a gene frequency of HPA-1b of 0.115 and 0.113, respectively, among blacks and whites. The frequency of HPA-2b among the Amerindians (0.042) is lower than that obtained for blacks and whites (0.148 and 0.100, respectively), and the lowest thus far observed in a population of Asian origin. CONCLUSION: Differences in DNA polymorphisms in Amerindian populations have not only anthropological and genetic interest, but also practical applications when they involve coding regions that may change the functional or immunologic features of the protein.

Alleles↗

PubMed1997

Factor IX gene haplotypes in Amerindians.

We have determined the haplotypes of the factor IX gene for 95 Indians from 5 Brazilian Amazon tribes: Wayampí, Wayana-Apalaí, Kayapó, Arára, and Yanomámi. Eight polymorphisms linked to the factor IX gene were investigated: MseI (at 5', nt -698), BamHI (at 5', nt -561), DdeI (intron 1), BamHI (intron 2), XmnI (intron 3), TaqI (intron 4), MspI (intron 4), and HhaI (at 3', approximately 8 kb). The results of the haplotype distribution and the allele frequencies for each of the factor IX gene polymorphisms in Amerindians were similar to the results reported for Asian populations but differed from results for other ethnic groups. Only five haplotypes were identified within the entire Amerindian study population, and the haplotype distribution was significantly different among the five tribes, with one (Arára) to four (Wayampí) haplotypes being found per tribe. These findings indicate a significant heterogeneity among the Indian tribes and contrast with the homogeneous distribution of the beta-globin gene cluster haplotypes but agree with our recent findings on the distribution of alpha-globin gene cluster haplotypes and the allele frequencies for six VNTRs in the same Amerindian tribes. Our data represent the first study of factor IX-associated polymorphisms in Amerindian populations and emphasizes the applicability of these genetic markers for population and human evolution studies.

Brazil↗

PubMed1996

Racial heterogeneity of DNA polymorphisms linked to the A and the O alleles of the ABO blood group gene.

Except for subgroup A2 and minor A, O and B alleles (Ax, O2 and B(A)), which occur at low frequencies in the population, the major ABO alleles are considered to be homogeneous entities. The present study is the first demonstration of an extensive variability linked to the more common alleles of the blood A and O genes by digestion of the genomic DNA with different restriction enzymes and hybridization with a probe generated by PCR amplification of a segment of the last exon of the glycosyltransferase gene. For group A in Whites, two or three-allele fragment length polymorphisms (RFLP) were demonstrated by Hinc II, Taq I and Hinf I; for group O two to five-allele RFLP were detected in Blacks, Whites and Amerindians with restriction enzymes Hinc II, Bgl I, Kpn I, Taq I and Hinf I. These polymorphisms probably originated by single-base changes, although a length variation due to variable number of tandem repeats cannot be ruled out for some. Allelic association between the different restriction sites permitted the identification of seven O allele haplotypes in Blacks, and two in Whites and Indians. Three different haplotypes were identified for group A in Whites. The greater heterogeneity of the O allele among the Blacks as compared with Whites and Indians is similar to that observed for other gene systems. The polymorphisms of the histoblood group ABH antigen genes seem a useful tool for population genetics, phylogenetics and evolution studies.

ABO Blood-Group System↗

PubMed1995

Identification of human T cell lymphotropic virus type IIa infection in the Kayapo, an indigenous population of Brazil.

Human T cell lymphotropic virus type II (HTLV-II) infection is endemic in a number of indigenous populations in North, Central, and South America. In the present study we have employed serological and molecular methods to identify HTLV-II infection in Indian communities in the Amazon region of Brazil. Sera (1324) from 25 different Indian communities were analyzed by ELISA and Western blot. One hundred and four samples (7.8%) from a number of culturally distinct and geographically unrelated populations were found to have reactivities consistent with HTLV-II infection. Of these, 67 were from the Kayapo Indian communities, which had an overall seroprevalence rate of greater than 30%. In addition, high seroprevalence rates were observed in three other communities, the Munduruku, Arara do Laranjal and the Tyrio, suggesting that there are additional foci of endemic infection in the Amazon region. In the Kayapo, seroprevalence rates tended to increase with age, supporting the importance of sexual transmission of the virus, and family studies demonstrated that vertical transmission is also an important route of infection. Restriction fragment length polymorphism (RFLP) and nucleotide sequence analysis of a region of the env gene demonstrated that the Kayapo are infected with the HTLV-IIa subtype. Moreover, nucleotide sequence analysis of the LTR demonstrated that this belonged to a distinct HTLV-IIa phylogenetic group. The identification of HTLV-IIa in the Kayapo is, as far as we are aware, the first identified endemic focus of infection by this subtype of HTLV-II in the Americas.

Adolescent↗

PubMed1995

Alpha-globin gene haplotypes in South American Indians.

The haplotypes of the alpha-globin gene cluster were determined for 99 Indians from the Brazilian Amazon region who belong to 5 tribes: Wayampí, Wayana-Apalaí, Kayapó, Arára, and Yanomámi. Three predominant haplotypes were identified: Ia (present in 38.9% of chromosomes), IIIa (25.8%), and IIe (22.1%). The only alpha-globin gene rearrangement detected was alpha alpha alpha 3.7 I gene triplication associated with haplotype IIIa, found in high frequencies (5.6% and 10.6%) in two tribes and absent in the others. alpha-Globin gene deletions that cause alpha-thalassemia were not seen, supporting the argument that malaria was absent in these populations until recently. The heterogeneous distribution of alpha-globin gene haplotypes and rearrangements among the different tribes differs markedly from the homogeneous distribution of beta-globin gene cluster haplotypes and reflects the action of various genetic mechanisms (genetic drift, founder effect, consanguinity) on small isolated population groups with a complicated history of divergence-fusion events. The alpha-globin gene haplotype distribution has some similarities to distributions observed in Southeast Asian and Pacific Island populations, indicating that these populations have considerable genetic affinities. However, the absence of several features of the alpha-globin gene cluster that are consistently present among the Pacific Islanders suggests that the similarity of haplotypes between Brazilian Indians and people from Polynesia, Micronesia, and Melanesia is more likely to result of ancient common ancestry rather than the consequence of recent direct genetic contribution through immigration.

Alleles↗

PubMed1994

Molecular bases of the ABO blood groups of Indians from the Brazilian Amazon region.

Phenotype studies of ABO blood groups in most Amerindian populations revealed the exclusive presence of group O. Since group O is the result of the absence of glycosyltransferase activity, its molecular bases may be heterogeneous. We carried out ABO blood group genotyping by analysis of DNA of 30 Indians from 2 Amazonian tribes (Yanomami and Arara), and compared the findings with other populations (Caucasians and Blacks). Two segments of the glycosyltransferase gene were amplified by PCR and digested with KpnI or AluI to detect deletion or base change at positions 258 and 700, respectively. For all subjects, the gene basis of blood group O is the deletion of a single nucleotide at position 258 of the glycosyltransferase A gene, similar to that observed in Caucasoids and Negroids. DNA sequencing of limited regions of the gene supports this conclusion. This finding does not exclude, however, that a heterogeneity of the O allele may be revealed by a more extensive analysis.

ABO Blood-Group System↗

PubMed1994

The heterogeneity of the beta s cluster haplotypes in Brazil.

The beta s cluster haplotypes were determined for 74 Brazilian patients with sickle cell anemia from three cities separated by 1,400 to 2,300 km. The cities are representative of the regions which have the largest Black populations of the country. All 138 chromosomes with typical haplotypes had one of the three most common African haplotypes. No example of the Asian or of the Cameroon haplotypes was found. The Bantu haplotype predominates in all three regions (54.8 to 73.1%), followed by the Benin haplotype (25.4 to 45.2%) and a small number of cases with the Senegal haplotype (0 to 6.9%). The mean prevalence of the Bantu haplotype of 65.9% agrees closely with historical data which indicate that 70% of the African slaves brought to Brazil originated from regions of Bantu populations.

Anemia, Sickle Cell↗

PubMed1992

Beta-globin gene cluster haplotypes in Yanomama Indians from the Amazon region of Brazil.

Six polymorphic restriction enzyme sites in the beta-globin gene cluster were investigated in Yanomama Indians from the Amazon region of Brazil, using the polymerase chain reaction (PCR) technique. Four haplotypes were identified; the haplotype frequency distribution is similar to those reported for Polynesians, Micronesians and most Asian populations.

Base Sequence↗

PubMed1989

Serum cholinesterase polymorphism (CHE1 and CHE2 loci) among several Indian groups from Amazon region of Brazil, and segregation of the C5 variant in families.

Eight Indian tribes from the Amazon region of Brazil (Araweté, Arara, Yamamadi, Kararaô, Karitiana, Waiampi, Surui and Cinta Larga) were studied for the distribution of the atypical and C5 variants of serum cholinesterase. None of them presented the CHE1*A allele, but the C5 variant was found in the Araweté (20.4%), Kararaô (15.6%), Karitiana (50.5%), Surui (12.3%) and Cinta Larga (19.6%) tribes. The frequency of the C5+ phenotype in the Karitiana is the highest reported thus far in human populations. Segregation studies considering the C5 variant were made among the Karitiana, and also among the Urubu-Kaapor and Munduruku tribes previously studied by Guerreiro et al [1987a, 1987b]. Most of the data were in agreement with the genetic hypothesis, but they also revealed a significant lack of the C5+ phenotype in offspring from C5+ X C5+ matings, as well as the occurrence of two C5+ children from C5- X C5- unions, in the Urubu-Kaapor tribe.

Alleles↗