Hemoglobin synthesis studies of a family with alpha-thalassemia trait and sickle cell trait

Genetic hemoglobin abnormalities in 2363 Cuban newborns

A total of 2363 Cuban newborns were screened for genetic hemoglobin abnormalities; 2187 (92.56%) had a normal electrophoretic pattern. Of the 176 samples with abnormal electrophoretic patterns, 102 (4.32%) had hemoglobins A, F plus Bart's; 54 (2.29%) had hemoglobins A, F and S; 3 (0.13%) had hemoglobins A, F, S plus Bart's; 14 (0.59%) had hemoglobins A, F and C; 1 (0.04%) had hemoglobins A, F, C and Bart's. The frequency of Hb Bart's was 4.46% in AA phenotype, 5.25% in AS, and 6.67% in AC. Two newborns were found to have rare variants. A close correlation was found between the observed and expected phenotypes, which indicates the accuracy of the diagnostic methods used. The results of all hemoglobin abnormalities were entered on the infants' hospital records. In addition, these families received genetic counseling.

Alpha-thalassemia and the production of different alpha chain variants in heterozygotes

The production of five alpha chain variants (Hb G-Georgia, Hb St. Luke's, Hb Lloyd, Hb Montgomery, and Hb G-Philadelphia) in heterozygotes was evaluated through hematological observations, hemoglobin quantification, and biosynthetic studies. All heterozygotes for Hb St. Luke's and Hb Lloyd and most heterozygotes with Hb G-Georgia and Hb Montgomery had normal hematology and average sigma alpha/beta values of about 1.1. They were assigned a normal genotype (alpha alpha G/alpha alpha), although the proportions of Hb St. Luke's and Hb G-Georgia were low (10 to 13%) and those of Hb Lloyd and Hb Montgomery twice as high (20%). Data from short-term incubations confirmed this genotype for some of these heterozygotes. Isolated Hb St. Luke's and Hb G-Georgia gave low alpha G/beta values (0.2 and 0.3) indicating that these Hb variants were defective at the level of Hb assembly. Isolated Hb Montgomery and Hb G-Philadelphia, however, gave higher alpha G/beta values of 0.6 and 0.8, respectively. A second type of variability existed among Hb G-Georgia (20 vs. 13%), Hb Montgomery (28 vs. 20%), and Hb G-Philadelphia (47 vs. 34%) heterozygotes, in whom the levels of Hb G differed. The occurrence of higher levels of these three alpha chain heterozygosities was associated with hematological or biosynthetic evidence of a mild or moderate alpha chain deficiency due to an alpha-thalassemia-2 heterozygosity (alpha alpha G/alpha O alpha or alpha O alpha G/alpha alpha) or a homozygosity (alpha O alpha G/alpha O alpha), respectively.

Post-translational control of human hemoglobin synthesis: the role of the differential affinity between globin chains in the control of mutated globin gene expression

The interactions between beta-thalassemia and the human hemoglobin (Hb) alpha-chain variants, Hb Hasharon, Hb O Idonesia and Hb J Paris, and between alpha-thalassemia and the beta-chain variants, Hb S, Hb C and Hb G San José, which are characterized by preferential decrease of the abnormal Hb level in peripheral bloods, have been studied. Both biosynthesis studies in reticulocytes and determination of the relative affinity of abnormal chains for normal complementary chains by in vivo recombination experiments, involving globin chains previously isolated in their native form, have been carried out in order to provide insights on the molecular events following the synthesis of the mutant chains under conditions of complementary chain deficiency. Furthermore, we have measured the relative affinity for complementary chain of beta D Los Angeles- and alpha J Rovigo-chains, the level of which does not decay in thalassemic carriers, and of alpha Legnano- and beta Osu Christiansborg-chains, which have not yet been observed in association with thalassemias. Our experiments indicated that the differential affinity for beta-chains is not always the major post-translational control mechanism which regulates the level of certain alpha-chain variants in beta-thalassemic heterozygotes, and that preferential removal of abnormal chains by proteolytic enzymes is likely to play an important role in most cases. On the other hand, the low affinity of certain variant beta-chains for alpha-chains may offer an explanation for the low level of certain beta-chain variants in peripheral blood of non-thalassemic carriers, as well as to their decrease under conditions of relative alpha-chain deficiency (alpha-thalassemias).

Hematological and clinical features of sickle cell diseases: a review

The differentiation, hematologic features and clinical manifestations of patients with the various sickling disorders are reviewed. The deficiencies in our current knowledge about the spectrum of the clinical course of patients with these conditions is discussed. The interaction of alpha thalassemia with sickle cell anemia and its possible effect upon the severity of the disease is summarized. The apparent milder disease in certain groups of patients with sickle cell anemia in whom there is an associated elevation of hemoglobin F is contrasted with the controversy surrounding the effects of hemoglobin F levels in the patients of African origin.

Interaction of alpha-thalassemia genes with each other and with HbC in an American black family

The relative rates of in vitro synthesis of hemoglobin chains have been studied in an American black family in which the mother is doubly heterozygous for alpha-thalassemia and HbC and the father is heterozygous for alpha-thalassemia. The alpha/non-alpha synthetic ratio was equally unbalanced in both the bone marrow and the peripheral blood of the mother. Although HbC comprised 35% of her hemoglobin (compared to 42.2 +/- 2.2 in individuals with HbC trait and balanced globin synthesis), synthetic data showed that the newly synthesized beta C chain was 44% of the total newly synthesized beta chains. Isolated membranes contained more newly synthesized beta C than beta A chains. Three of the offspring were within the normal range, and the remaining three had alpha-thalassemia. There were two spontaneous abortions during the second trimester of pregnancy. Hydrops fetalis did not occur, and none of the children had HbH disease or HbC trait.

Abnormal haemoglobins in the Sudan savanna of Nigeria. I. Prevalence of haemoglobins and relationships between sickle cell trait, malaria and survival

The prevalence of different haemoglobins and their interaction with malaria have been studied in Garki, Kano State, Nigeria. Sickle cell trait was present in 24% of newborn and 29% of those aged over five years. Hb.AC was present in 0.7%. Frequency of both haemoglobin variants was greater in Hausa than Fulani. Sickle cell anaemia was almost invariably fatal in early childhood. The distribution curve of percentage of Hb.S in sickle cell trait subjects was normal, and did not demonstrate any high frequency of a gene for alpha-thalassaemia. The presence of beta-thalassaemia minor could not be tested, but Hb.S/beta-thalassaemia was not detected. Hb.S gene frequency appears to have been maintained by a fitness in heterozygotes of 21% over normal homozygotes; increased fertility and high mutation rate did not make any apparent contribution. Hb.AS subjects had on average lower frequency and considerably lower densities of Plasmodium falciparum trophozoites than Hb.AA from the age of 30 to 59 weeks; density was less in sickle cell trait up to age three years in the dry season only. It is suggested that the survival advantage and hence the prevalence of sickle cell trait may be greatest in some hyperendemic areas and less where malaria transmission is extremely high or when it is high and unvaried.

betaS Chain turnover in reticulocytes of sickle trait individuals with high or low concentrations of haemoglobin S

Reticulocytes, isolated from the blood of sickle cell trait donors with either low (25-30%) or high (40-42%) haemoglobin S(Hb S) concentrations, were incubated with [3H]leucine for various times from 1.25 to 60 min. Samples of the total soluble fractions of the cells were denatured with urea and mercaptoethanol. The mixtures were analysed by electrophoresis on cellulose acetate strips. The specific radioactivities (dpm/mg) of the separated betaS and betaA globin chains were determined. The betaS/betaA ratios of globin chain specific radio activities in the reticulocytes of the 'low Hb S' donors decreased gradually from initial values higher than 1.30 to values near unity. These data suggested that faster turnover of some of the soluble, newly synthesized betaS chains compared to the newly synthesized betaA chains could explain part, but not all, of the disparity in concentrations of Hbs S and A in these people. When reticulocytes from 'high Hb S' donors were 3H-labelled for times longer than 5 min, the betaS/betaA specific radioactivity ratios remained at or near unity. This result suggested that newly synthesized betaS chains were not turning over selectively in these cells. Instead, there was a relative decrease in betaS chain synthesis proportional to the difference in blood concentrations of Hb S and Hb A. Additional calculations suggested that the more rapid turnover of newly synthesized betaS chains in the 'low Hb S' reticulocytes could explain the difference in Hb S concentrations between 'high and low Hb S' people. These results are consistent with previous reports that an alpha-thalassaemia gene, present in 'low Hb S' but absent in 'high Hb S' donors, may be responsible for the selective turnover of betaS chains.