RESUMO
We have identified a minor hemoglobin component (approximately 5%) in the blood of a healthy Costa Rican female, but not in her mother and two brothers (father not studied), that has an His --> Arg replacement at position beta 77 (Hb Costa Rica). No other amino acid replacements were observed and no beta- or gamma-chain-like peptides were present. Hb Costa Rica has abnormal stability. Sequence analyses of numerous polymerase chain reaction (PCR)-amplified segments of DNA that contain exon 2 of the beta gene failed to identify a CAC --> CGC (His --> Arg) mutation. The same was the case when cDNA was sequenced, indicating that a beta-Costa Rica-mRNA could not be detected with this procedure. Gene mapping of genomic DNA with Bg/II, BamHI, and HindIII gave normal fragments only and with the same intensity as observed for the fragments of a normal control. The quantities of the beta chain variants Hb J-Iran and Hb Fukuyama with related mutations at beta 77 vary between 30% and 45% in heterozygotes, whereas that of Hb F-Kennestone with the same His --> Arg mutation but in the G gamma-globin gene, is a high 40%-45% (as percentage of total G gamma) in a heterozygous newborn. These different observations exclude a heterozygosity of the A --> G mutation at codon beta 77, as well as a deletion comparable to that of Hbs Lepore or Kenya, or a beta-globin gene duplication, and point to a nontraditional inheritance of Hb Costa Rica. Allele-specific amplification of cDNA with appropriate primers identified the presence of a low level of mutated mRNA in the reticulocytes of the patient, which was confirmed by dotblot analysis of the same material with 32P-labeled probes. Comparable amplification products were not observed in genomic DNA. The A --> G mutation apparently occurred in a somatic cell at a relatively early stage in the development of the hematopoietic cell system, and Hb Costa Rica accumulated through rapid cell divisions in patchy areas in the bone marrow (somatic mosaicism). An unequal distribution of Hb Costa Rica over the red cells supports this possibility.
Assuntos
Hemoglobinas Anormais/genética , Mosaicismo , Mutação Puntual/genética , Adulto , Sequência de Aminoácidos , Aminoácidos/análise , Sequência de Bases , Códon/genética , Costa Rica , DNA Complementar/genética , Feminino , Variação Genética/genética , Hemoglobinas Anormais/análise , Hemoglobinas Anormais/química , Humanos , Masculino , Dados de Sequência Molecular , RNA Mensageiro/análise , RNA Mensageiro/genética , Reticulócitos/química , Análise de Sequência de DNARESUMO
Glucose-6-phosphate dehydrogenase (G6PD) deficiency has previously been reported among both the black and white populations of Costa Rica. All 28 G6PD A- samples were found to be of the common G6PD A-376G/202A type. A previously described mutation associated with nonspherocytic hemolytic anemia, G6PD Puerto Limón, was found to be due to a G----A transition at nucleotide (nt) 1192, causing a glu----lys substitution. Mutations in this region of the G6PD molecule seem invariably to be associated with chronic hemolytic anemia. G6PD Santamaria had been described previously in two unrelated white subjects. We found that both did, indeed, have the same mutations. In this variant the A----G substitution at nt 376 that is characteristic of G6PD A was present, but an A----T mutation at nt 542, apparently superimposed on the ancient G6PD A mutation, resulted in an asp----val substitution. Thus, the gain of a negative charge at amino acid 126 was counterbalanced by the loss of a charge at amino acid 181, giving rise to a variant with the G6PD A mutation but with normal electrophoretic mobility.
Assuntos
Deficiência de Glucosefosfato Desidrogenase/genética , Glucosefosfato Desidrogenase/genética , Isoenzimas/genética , Mutação , População Negra/genética , Costa Rica , Análise Mutacional de DNA , Humanos , Masculino , População Branca/genéticaRESUMO
The two first homozygous (or double heterozygous) cases of pyruvate kinase (PK) deficiency found in a Costa Rica family with no signs of consanguinity are reported. The clinical manifestations of the deficiency were present in both cases, these being enhanced in one of them by pregnancy. The family study performed showed the heterozygous character of the PK deficiency in all cases, plus the demonstration in two instances (father and brother) of a heterozygous haemoglobin C disease. The importance of the PK/HK quotient in the identification of the PK deficiency heterozygous is stressed, especially when the enzyme activity registered from haemolysates falls within the normal range.
Assuntos
Anemia Hemolítica Congênita não Esferocítica/genética , Anemia Hemolítica Congênita/genética , Doença da Hemoglobina C/genética , Piruvato Quinase/deficiência , Erros Inatos do Metabolismo dos Piruvatos/genética , Adulto , Anemia Hemolítica Congênita não Esferocítica/complicações , Anemia Hemolítica Congênita não Esferocítica/enzimologia , Costa Rica , Feminino , Doença da Hemoglobina C/complicações , Heterozigoto , Humanos , Masculino , Gravidez , Complicações Hematológicas na Gravidez , Piruvato Quinase/genética , Erros Inatos do Metabolismo dos Piruvatos/complicaçõesRESUMO
An electrophoretic pattern of Hb S + Hb F, the relative concentration of this last being 37%, was found in a phenotypically mestizo 3 year-old child of Costa Rica. The genotype of the child was G gamma/A gamma, with a ratio of 1:1. Both hereditary alterations were disperse, according to the family study performed, which showed Hb S plus hereditary persistence of foetal haemoglobin of the African type G gamma A gamma (delta beta o). This case is briefly discussed, along with the molecular heterogeneity of HPFH and the importance of the differential diagnosis of electrophoretic patterns found in Hb S + Hb F patients.