Investigating alpha-globin structural variants: a retrospective review of 135000 Brazilian individuals

Background: Brazil has a multiethnic population with a high diversity of hemoglobinopathies. While screenings for beta-globin mutations are far more common, alterations affecting alpha-globin genes are usually more silent and less well known. The aim of this study was to describe the results of a screening program for alpha-globin gene mutations in a representative sample of the Southeastern Brazilian population. Methods: A total of 135,000 individuals, including patients with clinical suspicion of hemoglobinopathies and their family members, randomly chosen individuals submitted to blood tests and blood donors who were abnormal hemoglobin carriers were analyzed. The variants were screened by alkaline and acid electrophoreses, isoelectric focusing and cation-exchange high performance liquid chromatography (HPLC) and the abnormal chains were investigated by reverse-phase high performance liquid chromatography (RP-HPLC). Mutations were identified by molecular analyses, and the oxygen affinity, heme-heme cooperativity and Bohr effect of the variants were evaluated by functional tests. Results: Four new and 22 rare variants were detected in 98 families. Some of these variants were found in co-inheritance with other hemoglobinopathies. Of the rare hemoglobins, Hasharon, Stanleyville II and J-Rovigo were the most common, the first two being S-like and associated with alpha-thalassemia. Conclusion: The variability of alpha-globin alterations reflects the high degree of racial miscegenation and an intense internal migratory flow between different Brazilian regions. This diversity highlights the importance of programs for diagnosing hemoglobinopathies and preventing combinations that may lead to important clinical manifestations in multiethnic populations.

Investigating alpha-globin structural variants: a retrospective review of 135,000 Brazilian individuals.

BACKGROUND: Brazil has a multiethnic population with a high diversity of hemoglobinopathies. While screenings for beta-globin mutations are far more common, alterations affecting alpha-globin genes are usually more silent and less well known. The aim of this study was to describe the results of a screening program for alpha-globin gene mutations in a representative sample of the Southeastern Brazilian population. METHODS: A total of 135,000 individuals, including patients with clinical suspicion of hemoglobinopathies and their family members, randomly chosen individuals submitted to blood tests and blood donors who were abnormal hemoglobin carriers were analyzed. The variants were screened by alkaline and acid electrophoreses, isoelectric focusing and cation-exchange high performance liquid chromatography (HPLC) and the abnormal chains were investigated by reverse-phase high performance liquid chromatography (RP-HPLC). Mutations were identified by molecular analyses, and the oxygen affinity, heme-heme cooperativity and Bohr effect of the variants were evaluated by functional tests. RESULTS: Four new and 22 rare variants were detected in 98 families. Some of these variants were found in co-inheritance with other hemoglobinopathies. Of the rare hemoglobins, Hasharon, Stanleyville II and J-Rovigo were the most common, the first two being S-like and associated with alpha-thalassemia. CONCLUSION: The variability of alpha-globin alterations reflects the high degree of racial miscegenation and an intense internal migratory flow between different Brazilian regions. This diversity highlights the importance of programs for diagnosing hemoglobinopathies and preventing combinations that may lead to important clinical manifestations in multiethnic populations.

Frequency and spectrum of hemoglobinopathy mutations in a Uruguayan pediatric population.

Hemoglobinopathies are the most common recessive diseases worldwide but their prevalence in Uruguay has not been investigated. In this study, 397 unrelated outpatient children from the Pereira Rosell Hospital Center (CHPR), as well as 31 selected patients with microcytic anemia and 28 ß-thalassemia carriers were analyzed for hemoglobinopathies by using biochemical and molecular biology methods. Parametric and non-parametric methods were used to compare the hematological indices between groups of genotypes. Of the 397 patients in the first group, approximately 1% (0.76% HbS and 0.25% ß-thalassemia) had a mutation in the HBB gene and 3.3% had ß-thalassemia. These mutations had a heterogeneous distribution that varied according to individual ancestry. HbS was found exclusively in individuals with declared African ancestry and had a carrier frequency of 2.2%. The frequency of α-thalassemia carriers in outpatients of European and African ancestry was 1.2% and 6.5%, respectively. In contrast, the frequency of α-thalassemia carriers in patients with microcytic anemia was 25.8%, significantly higher (p < 0.01) than that observed in the sample as a whole and in Afro-descendants and Euro-descendants. Significant differences were observed in the hematological parameters between individuals with thalassemia genotypes and those with a normal genotype. These results indicate that hemoglobinopathies are a relevant health problem in Uruguay.

Prevalence of α-thalassemia 3.7 kb deletion in the adult population of Rio Grande do Norte, Brazil.

α-Thalassemia, arising from a defect in α-globin chain synthesis, is often caused by deletions involving one or both of the α-genes on the same allele. With the aim of investigating the prevalence of α-thalassemia 3.7 kb deletion in the adult population of Rio Grande do Norte, 713 unrelated individuals, between 18 and 59 years-of-age, were analyzed. Red blood cell indices were electronically determined, and A(2) and F hemoglobins evaluated by HPLC. PCR was applied to the molecular investigation of α-thalassemia 3.7 kb deletion. Eighty (11.2%) of the 713 individuals investigated presented α-thalassemia, of which 79 (11.1%) were heterozygous (-α(3.7)/αα) deletions and 1 (0.1%) homozygous (-α(3.7)/-α(3.7)). Ethnically, heterozygous deletions were higher (24.8%) in Afro-Brazilians. Comparison of hematological parameters between individuals with normal genotype and those with heterozygous α(+)-thalassemia showed a statistically significant difference in the number of erythrocytes (p < 0.001), MCV (p < 0.001), MCH (p < 0.001) and Hb A(2) (p = 0.007). This study is one of the first dedicated to investigating α-thalassemia 3.7 kb deletion in the population of the State Rio Grande do Norte state. Results obtained demonstrate the importance of investigating this condition in order to elucidate the causes of microcytosis and hypochromia.

Determination of ß haplotypes in patients with sickle-cell anemia in the state of Rio Grande do Norte, Brazil.

ß(S) haplotypes were studied in 47 non-related patients with sickle-cell anemia from the state of Rio Grande do Norte, Brazil. Molecular analysis was conducted by PCR/RFLP using restriction endonucleases XmnI, HindIII, HincII and HinfI to analyze six polymorphic sites from the beta cluster. Twenty-seven patients (57.5%) were identified with genotype CAR/CAR, 9 (19.1%) CAR/BEN, 6 (12.8%) CAR/CAM, 1 (2.1%) BEN/BEN, 2 (4.3%) CAR/Atp, 1 (2.1%) BEN/Atp and 1 (2.1%) with genotype Atp/Atp. The greater frequency of Cameroon haplotypes compared to other Brazilian states suggests the existence of a peculiarity of African origin in the state of Rio Grande do Norte.

Characterization of beta-thalassemia mutations in patients from the state of Rio Grande do Norte, Brazil.

35 unrelated individuals were studied for characterization as either heterozygous or homozygous for beta-thalassemia. Molecular analysis was done by PCR/RFLP to detect the mutations most commonly associated with beta-thalassemia (ß(0)IVS-I-1, ß(+)IVS-I-6, and ß(0)39). In the patients who showed none of these mutations, the beta-globin genes were sequenced. Of the 31 heterozygous patients, 13 (41.9%) had the ß(+)IVS-I-6 mutation, 15 (48.4%) the ß(0)IVS-I-1 mutation, 2 (6.5%) the ß(+)IVS-I-110 mutation and 1 (3.2%) the ß(+)IVS-I-5 mutation. IVS-I-6 was detected in the four homozygotes. The mutation in codon 39, often found in previous studies in Brazil, was not detected in the present case. This is the first study aiming at identifying mutations that determine beta-thalassemia in the state of Rio Grande do Norte.

Determination of beta S haplotypes in patients with sickle-cell anemia in the state of Rio Grande do Norte, Brazil

βS haplotypes were studied in 47 non-related patients with sickle-cell anemia from the state of Rio Grande do Norte, Brazil. Molecular analysis was conducted by PCR/RFLP using restriction endonucleases XmnI, HindIII, HincII and HinfI to analyze six polymorphic sites from the beta cluster. Twenty-seven patients (57.5 percent) were identified with genotype CAR/CAR, 9 (19.1 percent) CAR/BEN, 6 (12.8 percent) CAR/CAM, 1 (2.1 percent) BEN/BEN, 2 (4.3 percent) CAR/Atp, 1 (2.1 percent) BEN/Atp and 1 (2.1 percent) with genotype Atp/Atp. The greater frequency of Cameroon haplotypes compared to other Brazilian states suggests the existence of a peculiarity of African origin in the state of Rio Grande do Norte.

Characterization of beta-thalassemia mutations in patients from the state of Rio Grande do Norte, Brazil

35 unrelated individuals were studied for characterization as either heterozygous or homozygous for beta-thalassemia. Molecular analysis was done by PCR/RFLP to detect the mutations most commonly associated with beta-thalassemia (β0IVS-I-1, β+IVS-I-6, and β039). In the patients who showed none of these mutations, the beta-globin genes were sequenced. Of the 31 heterozygous patients, 13 (41.9 percent) had the β+IVS-I-6 mutation, 15 (48.4 percent) the β0IVS-I-1 mutation, 2 (6.5 percent) the β+IVS-I-110 mutation and 1 (3.2 percent) the β+IVS-I-5 mutation. IVS-I-6 was detected in the four homozygotes. The mutation in codon 39, often found in previous studies in Brazil, was not detected in the present case. This is the first study aiming at identifying mutations that determine beta-thalassemia in the state of Rio Grande do Norte.

Beta-globin gene cluster haplotypes in Afro-Uruguayans from two geographical regions (South and North).

The beta-globin gene cluster haplotypes were identified in 52 and 40 chromosomes from two Afro-Uruguayan populations located in the South and North of the country, respectively. In both regions, the 5' haplotype 2 (+ - - - -), characteristic of non-African populations, was the most frequent, reflecting a strong process of admixture in Afro-Uruguayans (0.355 and 0.262, respectively). The haplotypes 3 (- - - - +) and 4 (- + - - +), characteristics of African sub-Saharan populations, present inverse frequencies in North and South: whereas in the South haplotype 3 is the second most frequent (0.232), and haplotype 4 presents a low frequency (0.019), in the North haplotype 4 is the third most frequent (0.140), and haplotype 3 only reaches an intermediate frequency (0.088). The pairwise F(ST) and the exact test of differentiation show genetic heterogeneity between both regions. Nei's genetic distance show that South and North present affinities with Bantu groups, although the North present the smallest genetic distance with the Mandenka, a Senegalese population. With respect to 3' haplotypes, haplotype I was the most frequent in both populations, followed by haplotype II, characteristic of sub-Saharan Africans. The high frequencies of haplotype III-Asian could indicate admixture with Native American populations. The differences observed between both Uruguayan regions could be explained by microevolutionary events as genetic drift, founder effects, differential admixture, and/or distinct origin of the African slaves introduced in those regions.

Alpha-thalassemia, HbS, and beta-globin gene cluster haplotypes in two Afro-Uruguayan sub-populations from northern and southern Uruguay

Hemoglobinopathies are the most common monogenic disorders worldwide; however, they have never been systematically studied from a genetic perspective in Uruguay. In this study, we determined the frequencies of hemoglobin variants in Afro-Uruguayans. A sample of 52 healthy unrelated Afro-Uruguayans from the northern (N = 28) and southern (N = 24) regions of the country was analyzed. Eight individuals (15.4 percent) were heterozygous for -alpha3,7thalassemia; seven of them (29.2 percent) were originally from the southern region, whereas one of them (3.6 percent) was from the northern region; the differences between both regions were statistically significant (p = 0.016 +/-0.003). The only structural mutation detected was betaS, which is typical of African populations. Four individuals (10 percent) were heterozygous for betaS, three of them (13.6 percent) from the South, and one (5.6 percent) from the North. The betaS haplotypes were analyzed in eight individuals: two were homozygous betaS/betaS, two were heterozygous betaS/betathal, and four were heterozygous betaS/betaª. This haplotype distribution (60 percent Bantu, 20 percent Benin, and 20 percent Bantu A2) is in agreement with historical records reporting a predominantly Bantu origin for the enslaved Africans brought to Uruguay. Even though this is a preliminary study, due to the small sample size, our results are suggestive of a relatively high incidence of hemoglobinopathies in the Afro-Uruguayan population.

Polycythemia and Hb Coimbra [beta 99 (G1) Asp -> Glu] in Brazil

We report the clinical and laboratory findings concerning three unrelated Brazilian patients investigated for polycythemia, whose definitive diagnosis could only be established after the presence of Hb Coimbra (b99 Asp ® Glu) was demonstrated. This illustrates the importance of properly investigating hereditary hemoglobinopathies in cases of erythrocytosis because in some populations variants with high oxygen affinity may be more frequent than expected but go undetected when conventional electrophoresis is used as the sole detection procedure.

Soluble transferrin receptor in sickle cell diseases: correlation with spleen function

OBJECTIVE: To correlate spleen function with soluble transferrin receptor (sTfR) levels and red cell ferritin (RCF) values in patients with sickle cell diseases. DESIGN: Prospective study. LOCATION: University Hospital, School of Medical Sciences, State University of Campinas; a tertiary hospital. PARTICIPANTS: 60 patients with sickle cell diseases, in a steady state, who had not received blood transfusions for 3 months; 28 normal individuals with no clinical or laboratory signs of anemia. MEASUREMENTS: Determination of serum iron, transferrin iron-binding capacity, serum ferritin, RCF and sTfR. Evaluation of spleen function: erythrocytes with pits were quantified. RESULTS: Patients with sickle cell anemia had sTfR levels significantly higher than in normal individuals or those with HbSC (p=0.0001) and there was an inverse correlation between sTfR and fetal Hb (p=0.0016). RCF values were significantly higher in sickle cell anemia patients than in normal individuals or those with HbSC (p=0.0001), and there was a correlation between RCF and pitted erythrocytes (p=0.0512). CONCLUSION: The association between sTfR and fetal Hb confirms the contribution of fetal Hb to improving the hemolytic state by minimizing the consequent reactive erythrocyte expansion. High sTfR levels are not related to the degree of spleen function deficiency seen in sickle cell disease patients. The deficiency in the exocytosis process of the spleen occurring in sickle cell anemia patients may contribute to their accumulation of RCF

Mild clinical expression of S-ß thalassemia in a Brazilian patient with the ß+ IVS-I- (T C) mutation

Nós caracterizamos a base molecular da talassemia ß em uma paciente negra brasileira, de 8 anos de idade, com um quadro clínico extremamente benigno de S-ß+ talassemia. A paciente tinha uma hemoglobina total de 10,1 g/dl, com 57 por cento de HbS. O sequenciamento direto do DNA, amplificado por PCR, revelou que a paciente é heterozigota da mutaçäo ß+IVS-I-6 (T C). Esta mutaçäo, algumas vezes referida como o tipo português de talassemia, foi encontrada em associaçäo com o polimorfismo C T no codon 2 do gene ß e, de nosso conhecimento, näo havia sido previamente descrita na populçäo negra brasileira.

Red cell indices and alpha-thalassemia

O presente trabalho teve o objetivo de verificar se a concentraçäo de Hb e os índices hematimétricos VCM e HCM podem ser empregados na identiticaçäo de indivíduops portadores da talassemia *+. Assim foram comparados 3 grupos de recém -nascidos negróides cujos genótipos foram deduzidos através da detecçäo e quantificaçäo de Hb Bart's em sangue de cordäo umbilical. O primeiro grupo era composto de 252 recém-nascidos nos quais a Hb Bart's näo foi detectada. o segundo por 31 prováveis heterozigotos para talassemia * níveis de Hb Bart's entre 1,5 -3,8%); e o terceiro grupo por 5 provaveis homozigotos para talassemia * (Hb Bart's entre 5,9 - 9,0%). Foram comparados ainda os dados em adultos negros (doadores de sangue) cujos genótipos foram diretamente determinados por análise de DNA com enzimas de restriçäo (33 com genótipo normal e 10 heterozigotos para talassemia *+). Os resultados mostraram que a concentraçäo de Hb näo se correlaciona com a presença de talassemia *+, näo diferindo significativamente entre os grupos analisados. Já com relaçäo ao VCM e HCM, as médias foram significativamente diferentes, permitindo a distinçäo entre os grupos. No entanto, a distribuiçäo individual dos valores mostrou considerável sobreposiçäo, comprovando que estes índices näo säo capazes de identificar casos individuais, o que näo os recomenda, de forma isolada, como indicadores da talassemia *