Restriction and persistence of polymorphisms of HLA and other blood genetic traits in the Parakanã Indians of Brazil

Genetic variability of platelet glycoprotein Ibalpha gene

Platelet membrane glycoprotein (GP) Ibalpha is a critical component of platelet adhesion complex to subendothelium structures following tissue injury or pathological surfaces, such as atherosclerotic plaques. Polymorphisms of the GPIbalpha gene have been associated with a high risk for occlusive vascular disease, and its distribution varies considerably among distinct populations. These polymorphisms comprise the human platelet antigen (HPA)-2 system, the -5C/T dimorphism of the Kozak sequence, and the variable number of tandem 39-bp repeats (VNTR). Here we report the prevalence of the GPIbalpha gene polymorphisms among Brazilians, a highly ethnically diverse population. We analyzed 492 subjects of European, African, or Indigenous origin. It was possible to determine ten distinct haplotypes. The most common ( reverse similar 40%) haplotype was the Kozak-TT/HPA-2aa/VNTR-CC for both Caucasian and African descent. However, among Indigenous, Kozak-TT/HPA-2aa/VNTR-CC and Kozak-TC/HPA-2aa/VNTR-CC were equally present. Although a strong linkage disequilibrium between VNTR and HPA-2 polymorphism had also been observed, here we determined incomplete linkage disequilibrium in 10% of subjects from all ethnic groups. VNTR-E, a rare variant lacking the 39-bp repeat, was identified in two unrelated subjects, and functional platelet studies revealed no abnormalities. The VNTR-A allele, the largest variant containing four copies of the repeats, was not identified in this population. However, homozygosity for the VNTR-A allele (Kozak-TT/HPA-2aa/VNTR-AA) was determined in two distinct species of nonhuman primates. These results suggest a greater complex evolutionary mechanism in the macroglycoprotein region of the GPIbalpha gene and may be useful in the design of gene-disease association studies for vascular disease.

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.

A novel DI*A allele without the Band 3-Memphis mutation in Amazonian Indians

BACKGROUND AND OBJECTIVES

The blood-group antigens Dia and Dib are carried on erythrocyte band 3 and are defined by a single amino acid substitution at position 854 (Leu for Dia and Pro for Dib). The Band 3-Memphis variant has a point mutation (166A>G) in the SLC4A1 gene, which encodes the amino acid substitution Lys56Glu. Two types of Band 3-Memphis, variants I and II, are distinguished by their susceptibility to covalent labelling with 4,4'-diisothiocyanato-1,2-diphenylethane-2,2'-disulphonic acid (H2DIDS). Memphis II is more readily labelled than Memphis I or normal band 3. It is reported that Memphis II is associated with Dia. In a study designed to determine the frequency of the DI*A/DI*B and 166A>G polymorphisms in different populations in Brazil, we found a new DI*A allele.

MATERIALS AND METHODS

We studied DNA samples from 70 Amazonian Indians, 71 individuals of Japanese descent, 93 random Brazilian blood donors and 84 blacks with sickle cell disease. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analyses were performed on all samples, using MspI for DI*A/DI*B (exon 19) and MnlI for 166A>G (exon 4). Exon 4 and exon 19 from four outliers were sequenced.

RESULTS

Among Amazonian Indians, DI*A and 166G mutations both had a high frequency (0.57 and 0.54, respectively). In individuals of Japanese descent, these alleles were moderately frequent (0.07 and 0.19, respectively). We identified a new allele with DI*A and 166A (56Lys) in four Amazonian Indians.

CONCLUSIONS

Our results revealed that DI*A does not have a strict association with 166G. They also show the relevance of testing a cohort of different populations.

Frequencies of UDP-glucuronosyltransferase 1 (UGT1A1) gene promoter polymorphisms among distinct ethnic groups from Brazil

A polymorphism in the promoter region of the UDP-glucuronosyltransferase 1 (UGT1A) gene is associated with Gilbert syndrome (GS), a benign form of mild unconjugated hyperbilirubinemia. We genotyped 157 individuals from Brazil, comprising 71 Caucasians, 54 African-derived subjects, and 32 Parakanã Indians. Frequencies of the alelle (TA)(7) associated with GS found in this study were 0.324, 0.407, and 0.328, respectively. The genotype frequencies differed significantly between Caucasians and African-derived individuals. The high frequencies of (TA)(7) polymorphism among the three groups confirm previous data that this polymorphism is very ancient and appears to be distributed throughout the world.

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.

Novel HLA allele, HLA-B*4013, identified from a potential bone marrow recipient. Putative gene conversion events with donor sequence

A new B40 allele was identified in a leukemic Caucasian patient. This allele, designated B*4013, differs in alpha 1 domain from B*4002 at six amino acidic positions: 67, 77, 80, 81, 82 and 83. Most of this substitutions could alter the antigen binding site of the HLA-B molecule. B*4013 may have originated by gene conversion or reciprocal recombination involving B*4002 as the recipient allele of sequence donated by B*4406. The new allele was serologically typed as a "blank" associated with the Bw4 epitope.

Frequencies of platelet-specific alloantigen systems 1-5 in three distinct ethnic groups in Brazil

The human platelet antigen (HPA) systems are related to immune platelet disorders as well as to the development of occlusive vascular disease. Several distinct biallelic HPA systems are known, and a heterogeneous distribution of HPA alleles has been described among distinct ethnic groups. In this study we genotyped 320 carefully selected individuals from three distinct ethnic groups in Brazil (Caucasians, Blacks and Amazonian Indians) for the HPA-1, -2, -3, -4 and -5 systems. A similar prevalence for all HPA alleles was found in Brazilians of Caucasian and Black descent. These data contrast with those reported for similar ethnic groups in other countries. Among the Amazonian Indians, no b allele of the HPA-1, -4 and -5 systems was identified. The data presented here could be useful in the diagnosis of alloimmune platelet disease, in genetic counselling and in the development of screening programmes for HPA-related diseases.

Mutation analysis of the HFE gene in Brazilian populations

We analyzed the frequency of the C282Y and H63D mutations in the HFE gene in 227 individuals from Brazil comprising 71 Caucasians, 91 racially mixed Caucasian African-derived Amerindians (both populations from Southeast Brazil), 85 African-derived subjects (from Northeast Brazil) and 75 Parakanã Indians. Allelic frequency of the mutation C. 845G(A (C282Y) was 1.4% in the Caucasian population, 1.1% in the African-derived population, 1.1% in the racially mixed normal controls and 0% in the Parakanã Indians. In the African-derived population, the C282Y mutation was present on chromosomes bearing the haplotype 6/1h according to Beutler and West (1997). Allelic frequency of the mutation C. 187C(G (H63D) was 16.3% in the Caucasian population, 7.5% in the African-derived population, 9.8% in the racially mixed controls and 0% in the Amerindians. The presence of these mutations in the African-derived population reflects the fact that these subjects may have undergone a non-identified racial admixture in their past history. The absence of both defects in the Amerindians suggests that these mutations have emerged after the migration of Polynesians to America, or that they may not have reached the Polynesian population until after the migration to America had occurred.

Novel HLA-A and HLA-B alleles in South American Indians

The human leukocyte antigen (HLA) complex includes the most polymorphic genes in humans. More than 600 allelic variants have been described in different populations. The HLA-B locus has contributed the largest number of alleles. Although Native American populations display a restricted number of HLA-alleles, many novel HLA class I alleles have been identified in indigenous communities of Central and South America. We have studied 248 unrelated individuals from three tribes of North-East Argentina and one from South-West Brazil, as well as 80 related individuals from the Brazilian tribe. In the course of this work, we found 8 new B-locus alleles and 2 novel A-locus alleles in these populations. Here we report the nucleotide sequences of A*0219, A*0222, B*3519, B*3520, B*3521, B*3912, B*4009 and B*4803 and we show their relationship with similar alleles. The new alleles B*35092 and B*3518 have been described by us in a previous paper. The possible mechanisms that may have produced these alleles over evolutionary time are discussed.

Prevalence of homozygosity for the deleted alleles of glutathione S-transferase mu (GSTM1) and theta (GSTT1) among distinct ethnic groups from Brazil: relevance to environmental carcinogenesis?

Environmental related diseases due to occupational carcinogens and toxic substances are a serious problem particularly in developing countries. The glutathione S-transferase system is fundamental for the detoxification of numerous carcinogens and mutagens. The individual inherited susceptibility to chemical carcinogenesis due to glutathione S-transferase mu (GSTM1) and theta (GSTT1) varies significantly among distinct ethnic groups. In this study we determined the prevalence of the null genotype of the GSTM1 and GSTT1 genes among individuals from three distinct Brazilian racial groups using a multiplex-PCR methodology. The results showed that the highest prevalence of the null genotype for the GSTM1 occurred among Caucasians (55%, allele frequency = 0.74), followed by 33% among Brazilian Black subjects (allele frequency = 0.57), and 20% among Amazonian Indians (allele frequency = 0.45). For GSTT1 a homogenous distribution of the null genotype was found among Caucasian and African descendants (18.5 and 19% homozygotes, respectively, allele frequency = 0.43), with a lower prevalence among Amazonian Indians (11% of homozygotes, allele frequency = 0.34). Whether the deficiency of the GST system contributes to a predisposition to environmental related carcinogenesis in specific populations in Brazil remains to be determined.

Prevalence of the mutation C677 --> T in the methylene tetrahydrofolate reductase gene among distinct ethnic groups in Brazil

Vascular disease is a serious public health problem in the industrialized world, and is a frequent cause of death among the adult population of Brazil. Mild hyperhomocysteinemia has been identified as a risk factor for arterial disease, venous thrombosis, and neural tube defects. Individuals homozygous for the thermolabile variant of methylenetetrahydrofolate reductase (MTHFR-T) are found in 5-15% of the general population and have significantly elevated plasma homocysteine levels which represent one of the genetic risk factors for vascular diseases. We have analyzed the prevalence of individuals homozygous for the MTHFR-T in 327 subjects representing the three distinct ethnic groups in Brazil. The prevalence of homozygotes for the mutated allele MTHFR-T was high among persons of Caucasian descent (10%) and considerably lower among Black (1.45%) and Indians persons populations (1.2%). These data suggest that screening for the MTHFR-T allele should help in identifying individuals with a high risk of vascular disease among populations with a heterogeneous background.

Presence of allele alphaLELY in an Amazonian Indian population

Allele alphaLELY is a low-expression allele of the erythroid spectrin alpha-chain that is characterized by a C --> G mutation at position alpha1857 in exon 40 and a C --> T (nt -12) mutation in intron 45. This second mutation is probably responsible for the partial skipping of exon 46. This exon is essential for the nucleation of the alpha-chains by the beta-chains during erythropoeisis. Although allele alphaLELY remains asymptomatic in both heterozygotes and homozygotes, it enhances the expression of deleterious alpha-alleles that occur and, as such, has clinical importance. In this study, the frequency of allele alphaLELY was estimated in two ethnically different Brazilian populations: a random sample of blood donors from Campinas, a city located in São Paulo State, in the southeastern region of Brazil, and a sample of Parakanã Indians (Tupi tribe), a very isolated population with a high degree of inbreeding. The frequency of allele alphaLELY in the blood donor's sample (n = 54) was 24.1% whereas in the indigenous sample (n = 41), it was 15.9%. These frequencies were not significantly different at the 5% level (chi2 = 1.931). Similarly, when the frequencies of our samples were compared with those of the four ethnic groups studied by Maréchal et al. [Br J Haematol 90:553-556, 1995], no significant differences were found at the 5% level (chi2 = 6.686). These results suggest that allele alphaLELY is a very ancient allele since it occurs with a relatively uniform and high frequency in all human ethnic groups studied so far. These findings confirm the importance of allele alphaLELY in influencing the expression of deleterious alpha-spectrin alleles. To our knowledge, these are the first data concerning allele alphaLELY in native Americans.

Dissimilar evolution of B-locus versus A-locus and class II loci of the HLA region in South American Indian tribes

Native American populations have a limited HLA polymorphism compared with other ethnic groups. In spite of this, many novel HLA-B locus alleles, not observed in other populations, have been identified in South American tribes, and rapid evolution of this locus has been suggested. We have studied unrelated subjects of the Toba (TOB n = 116), Wichi (WIC n = 46) and Pilaga (PIL n = 14) tribes from northeastern Argentina to investigate the extent of the HLA polymorphism and obtain clues of selective forces that may have acted in these populations. In these tribes the number of HLA alleles is small at all loci except HLA-B, which presents 22 alleles. Seven novel alleles were characterized including 5 of HLA-B (B*35092, B*3518, B*3519, B*4009, B*4803) 1 at HLA-A (A*0219) and 1 at DRB1 (DRB1*0417). All these variants may have arisen by gene conversion events. Some of the novel variants represent the most frequent alleles of these populations (B*4803 in TOB and PIL; B*3519 in WIC) or are the most frequent subtypes in their lineages. HLA-A, B, DRB1,DQA1 and DQB1, but not DPB1, display relatively similar gene frequencies. This results in high heterozygosity in all the tribes for all the loci studied except HLA-DPB1. The larger polymorphism and the generation and maintenance of novel alleles at the HLA-B locus suggests a more specialized response of this locus to evolutionary forces. These effects may be related to the nature of the polymorphism, to the number of founder alleles and to the functional characteristics of the individual alleles.

The HLA polymorphism of two distinctive South-American Indian tribes: the Kaingang and the Guarani

The HLA-A, B, C, DR and DQ antigens of 240 Kaingang and 98 Guarani individuals have been characterized. The most frequent antigens found among the Kaingang are A31, 2, 24; B35, 51, 39, 48; Cw4, 7, 3, 1; DR8, 4, 2; DQ blank, 3. In the Guarani, they are A2, 28, 31; B40, 62, "53G"; Cw3, 4; DR2, 4, 8, 6; DQ3, blank. B " 53G" is an unusual antigen of the B5 cross-reactive group. DQ blank possibly corresponds to DQ4, not tested in this study. The reaction patterns of B35, B40 and DR4 indicate intra-tribal (of B35 and B40), and inter-tribal (DR4, B40 and B35) heterogeneity of these antigens. 408 Kaingang and 141 Guarani haplotypes were defined by segregation analysis. Of the commonest 10 Guarani and 9 Kaingang haplotypes, only one is shared by both tribes. Significant, positive linkage disequilibrium values for HLA-A,B; HLA-A,C; HLA-B,DR and most HLA-B,C antigen pairs were also different for the two populations. Genetic distance estimates between these two and another seven South-American Indian populations, and relative to the major human races (negroids, caucasoids, and mongoloids) reveal a comparatively high degree of divergence between the Kaingang and the Guarani, which is uncommon for Amerindian populations living close one to another.

Isoelectric focusing studies in Brazilian Indians--uncovering variation of ORM, AHSG and IF

Allele frequencies for the orosomucoid 1 (ORM1), orosomucoid 2 (ORM2), alpha-2-HS-glycoprotein (AHSG) and complement component I (IF) loci were studied in 393 individuals of three Brazilian Indian tribes. In the ORM1 locus only two alleles were observed among the Urubu-Kaapor, while five were found among the Pacaás Novos. The frequency of ORM1*1 was similar in these two tribes (0.734 and 0.715, respectively) but departed more markedly among the Parakanã (0.870). Variation for ORM2 locus was found among the Pacaás Novos only, with ORM2*3 being observed in just three individuals. A new variant (AHSG*PN) was found in the AHSG system. Frequency for AHSG*1 was unexpectedly low in the three tribes, especially, among the Pacaás Novos, where the prevalence (0.145) is the lowest considering other data reported thus far. For IF locus, variability was also restricted to only one trible (Urubu-Kaapor) and attributed to a new polymorphic allele, IF* A3.

Genetic variation within the Tupi linguistic group: new data on three Amazonian tribes

A total of 505 individuals belonging to four populations of three Brazilian Indian tribes were variously studied in relation to 34 genetic systems, and the results were compared with South American Indian averages and five other Tupi populations. Rare variants (CdE of the Rh system, PGM211-1, Cp A-CAY1, serum cholinesterase2 C5+ and some Gm combinations) were observed with varying prevalences, and the three tribes showed different degrees of departure (28%-40% of differences of 10% or more in gene frequencies) from South American Indian averages. People from two communities who speak the same language and are labelled as belonging to the same tribe (Asurini) showed a large degree of genetic differentiation. Another of the tribes studied (Urubu-Kaapor) link through genetic distance analyses with two other tribes from the north of the continent, forming a distinct microevolutionary unit. These features emphasize the peculiarities of the genetic variation in populations with a hunter-gatherer, rudimentary agriculture type of economy.

Genetic variation within a linguistic group: Apalai-Wayana and other Carib tribes

A total of 136 individuals were studied in relation to 31 genetic systems, and the results were compared with South American Indian averages and previous surveys on the Wayana of French Guiana and Surinam. The information was afterwards integrated with data from other Carib groups, and two types of genetic distances (Nei's and Edwards') were calculated a) between five groups, considering ten systems; and b) between nine groups, using five systems. The two measures of genetic distances correlated well (Spearman's correlation coefficient around 0.70), and there was good agreement between the geographical and genetic distances. All analyses indicated a peripheral position for the Apalai-Wayana and their distinctiveness from the Wayana of French Guiana and Surinam, suggesting that intertribal fusions may play an important role in the genetic differentiation of these populations.

O sarampo entre sociedades indígenas brasileiras e algumas considerações sobre a prática da saúde pública entre estas populações

O presente trabalho reve os principais aspectos ligados à epidemiologia do sarampo entre sociedades indígenas brasileiras. São discutidos os fatores de ordem genética, nutricional e sócio-cultural implicados na dinâmica de transmissão da doença, enfatizando-se o papel da provisão de serviços básicos de saúde na prevenção da elevada prevalência e mortalidade observada durante epidemias. O autor aborda também aspectos referentes à prática da saúde pública entre estas populações, salientando a relevância da constituição de grupos multidisciplinares para atuação tanto a nível de planejamento como prestação de serviços básicos assim como um maior envolvimento das escolas de saúde pública no atendimento destes grupos.

Hepatitis A antibody in an isolated Amerindian tribe fifty years after exposure

Antibody to hepatitis A in an Amerindian tribe was found in everyone over 50 years old but in no one younger. We suggest that the tribe had become infected with hepatitis A virus during the period, about 50 years earlier, when they engaged in raids on Luso-Brasilian settlers, that the virus failed to persist in the tribe when they withdrew into isolation, and that those who had been infected maintained antibody titers without boosting since that time.

Population structure and blood genetics of the Pacaás Novos Indians of Brazil

Two communities of relatively recently contacted Brazilian Indians, the Pacaás Novos, have been studied in relation to several demographic parameters and 28 genetic systems. The age and sex distribution, fertility and mortality patterns were not very distinct in the two populations, but they differed markedly in relation to the mating, migration and genetic data (six of the 19 variable loci showed differences higher than 10%). This was interpreted as being the consequence of a fission event, one of the many that may periodically occur, sometimes followed by fusions, in populations at this cultural level. The Pacaás Novos also show some distinctive features when previous genetic studies of South American Indians are reviewed, eight alleles of the variable 19 (LMS, R2, R0, Se, Hp1, Gm1,2;21, Gc1F and PGM1(1)), presenting differences varying between 12%-34% from the average obtained considering these earlier investigations.

Study of HLA system in a Mataco population: a geographically isolated American Indian tribe

A search for antigens of the HLA system has been carried out in 53 Mataco Indians of Argentina living in a geographically isolated area in the northeast of the country. Samples were mostly collected from adults of both sexes who were not directly related. Lymphocyte typing was performed using the microcytotoxicity technique of NIH. 118 sera specific for 15 antigens of the first HLA locus, 22 antigens of the second and 6 of the third were used. The most frequently found alleles were HLA-A28, Aw31 and A2 for the first locus; B15 and B40 for the second; and Cw3 and Cw4 for the third. In addition to previously published investigations on South American Indians, our typing work shows a remarkable homogeneous gene pool and a restricted range of polymorphism; therefore, a further set of haplotypes rendered us also restricted. The most frequent haplotypes that showed a significant statistical linkage disequilibrium were: A2-Cw4, A28-Bx, A2-Cw3, Aw31-Bw16, Aw24-Cw3, B15-Cw3, Bw16-Cw3 and A28-B5. Some of these haplotypes have also been found in other indian populations.

Failure of linguistic relationships to predict genetic distances between the Waiãpi and other tribes of lower Amazonia

Data on blood group, serum protein, erythrocyte enzyme, and histocompatibility antigen (HLA) traits are presented for the Waiãpi, a Tupi-speaking tribe of the Brazilian and French Guianas. Intra- and intertribal comparisons have been made between these data, and previously published data from French Guiana, from another Tupi tribe and from other tribes of neighboring areas, and from the continent as a whole. For this purpose, we have modified the usual measure of genetic distance to obtain a value which is independent of the number of loci being considered. The intertribal genetic distances do not correlate with linguistic affinity. Social differences, which may have affected the rate of drift from the continental mean, correlate better with genetic distances.

Hemoglobin types in Brazilian populations

Population surveys performed in different Brazilian ethnic groups, and comprising 23,606 subjects, disclosed, besides the common S and D types, hemoglobins G and Por to Alegre, as well as high F, A'2 and an apparently unstable A2 variant. Additional studies on isolated families revealed the occurrence of hemoglobins I, Niterói, D Punjab, M Boston and J Rovigo. Screening for sickle cells was also performed on 17,412 individuals. Detailed clinical studies on series of sickle cell anemics were also performed. Due to their special interest, the physico-chemical properties of Hb porto Alegre are reviewed in some detail.

HLA antigens in South American Indians

New HLA data for the Tirio, Parakanã, Kayapo and Mapuche tribes, as well as supplementary data for the Waiãpi, are presented. Taken together with previously published information on South American Indians, these typings show a remarkably homogeneous gene pool with a restricted range of polymorphisms and a further restricted set of haplotypes.