Andrée M. Dozy

Concurrent sickle-cell anemia and α-thalassemia: effect on severity of anemia.

Abstract We studied 47 patients with sickle-cell anemia to determine the effect of α-thalassemia on the severity of their hemolytic anemia. We diagnosed α-thalassemia objectively by using α-globin-gene mapping to detect α-globin-gene deletions, studying 25 subjects with the normal four α-globin genes, 18 with three, and four with two. The mean hemoglobin, hematocrit, and absolute reticulocyte levels (±S.D.) were 7.9±0.9 g per deciliter (4.9±0.6 mmol per liter), 22.9±2.9 per cent, and 501,000±126,000 per cubic millimeter, respectively, in the non-thalassemic group; 9.8±1.6 g per deciliter (6.1±1.0 mmol per liter), 29.0±5.0 per cent, and 361,000±51,000 per cubic millimeter in the group with three α-globin genes; and 9.2±1.0 g per deciliter (5.7±0.6 mmol per liter), 27.5±3.0 per cent, and 100,000±15,000 per cubic millimeter in the group with two α-globin genes. Deletion of α-globin genes was also accompanied by a decreased mean corpuscular hemoglobin concentration (MCHC) in post-reticulocyte erythrocytes and...

Prenatal diagnosis of α-thalassemia: clinical application of molecular hybridization.

Abstract The technic of DNA-DNA hybridization was used for prenatal diagnosis of a pregnancy at risk for homozygous α-thalassemia. Fibroblasts were cultured from amniotic fluid, and the number of α-globin genes in the DNA was quantified by hybridization with radioactive DNA complementary to α-globin mRNA sequences. As compared to control studies of DNA from patients with α-thalassemia syndromes and from unaffected subjects, the results indicated that the fetus had α-thalassemia-1. The diagnosis was confirmed by umbilical-cord blood studies. (N Engl J Med 295:1165–1167, 1976)

Identification of a Nondeletion Defect in α-Thalassemia

Abstract The molecular defect that has been demonstrated in α-thalassemia is the deletion of the α-globin structural genes. Since thalassemias are composed of heterogeneous groups of disorders, other types of defects could also result in α-thalassemia. We studied a Chinese family in which analysis of the mode of inheritance of α-thalassemia-1 and hemoglobin-H disease suggests a lesion that is not due to structural-gene deletion. Molecular hybridization studies with synthetic radioactive DNAs complementary to α-globin mRNA sequences show that in addition to the usual deletion defect, a nondeletion defect produces the phenotype of α-thalassemia-1. The combination of the deletion and nondeletion defects results in hemoglobin-H disease and not homozygous α-thalassemia associated with hydrops fetalis. (N Engl J Med 297:1081–1084, 1977)

Detection of the sickle gene in the human fetus. Potential for intrauterine diagnosis of sickle-cell anemia.

Abstract A method for detection of the types of globin chains synthesized by first-trimester fetuses has been established with umbilical-cord blood derived from fetuses removed at hysterotomy. The blood is incubated with radioactive leucine, and the globin chains chromatographed on carboxymethyl cellulose in the presence of 8 M urea. The presence of beta A or beta S chains is verified by subsequent co-chromatography, digestion with trypsin and high-voltage electrophoresis. Since maternal blood makes an unimportant contribution to the radioactivity observed in fetal radiochromatograms, mixed placental blood provides an adequate sample for the detection of globin-chain synthesis by the fetus. Thus, if mixed placental blood is aspirated, sickle-cell trait in a fetus can be detected. This method provides an approach to focused genetic counseling for disorders of hemoglobin.

Successful Application of Prenatal Diagnosis in a Pregnancy at Risk for Homozygous β-Thalassemia

A Sicilian couple whose first child had homozygous beta-+-thalassemia requiring monthly transfusion requested prenatal diagnosis during the second pregnancy. Fully informed consent was obtained. The placenta was localized by ultra-sound at the 20th week of gestation, and was aspirated with a 20-gauge needle. Samples containing fetal red cells were obtained, and studies of globinchain synthesis showed a normal beta/gamma synthesis ratio for this gestational age. The conclusion that the child was not affected by beta-thalassemia was confirmed when an infant not affected with homozygous of heterozygous beta-thalassemia was born at term. Although more experience with this approach is necessary, this study demonstrates that prenatal diagnosis or exclusion of beta-thalassemia and sickle-cell anemia is feasible.

Haemoglobin Constant Spring Synthesis in Red Cell Precursors

Summary. The synthesis of α Constant Spring (αcs) chain was studied in the peripheral blood and bone marrow of five patients with haemoglobin H Constant Spring disease. Relative to the normal α and β chains, the production of αcs chain was found to be less efficient as the erythroid cells mature.

Modification of Hemoglobin H Disease by Sickle Trait

The rarity of hemoglobin (Hb) H disease in combination with sickle trait may be due in part to the absence of actual Hb H in individuals who, nonetheless, have inherited the deletion of three alpha-globin genes. We describe here a boy with persistent microcytic, hypochromic anemia despite adequate iron stores, who exhibited splenomegaly with a normal reticulocyte count and only rare inclusions in circulating erythrocytes. Starch gel electrophoresis and isoelectric focusing at age 5 yr showed 21% Hb S, persistent Hb Barts, but no Hb H. Recticulocyte alpha/non-alpha globin chain synthesis ratio was 0.58 at age 5. The mother (Asian) had laboratory evidence of alpha-thalassemia trait and the father (Black) had sickle trait. The nature of alpha-thalassemia in this patient was investigated both by liquid hybridization and by the Southern method of gene mapping, in which DNA is digested with restriction endonucleases and the DNA fragments that contained the alpha-globin structural gene identified by hybridization with complementary DNA. The patient had only one alpha-globin structural gene, located in a DNA fragment shorter than that found in normal or alpha-thalassemia trait individuals, but similar to that present in other patients with Hb H disease. Morphologic studies of bone marrow by light and electron microscopy revealed erythroid hyperplasia with inclusions in polychromatic and orthochromatic erythroblasts, suggesting early precipitation of an unstable hemoglobin. The lack of demonstrable Hb H may be the result of both diminished amounts of beta(A) available for Hb H formation (since one beta-globin gene is beta(S)) and the greater affinity of alpha-chains for beta(A) than beta(S)-globin chains leading to the formation of relatively more Hb A than Hb S. The presence of a beta(S) gene may thus modify the usual clinical expression of Hb H disease.

Diagnosis of homozygous α-thalassemia in cultured amniotic-fluid fibroblasts.

THE α-thalassemias in Asian populations are primarily caused by deletion of the α-globin structural genes.1 2 3 4 5 6 In the fatal condition of homozygous α-thalassemia associated with hydrops feta...

Tissue-specific targeting of retroviral vectors via ligand-receptor interactions

Abstract The development of retroviral vectors that target specific cell types could have important implications for the design of gene therapy strategies. A chimeric protein containing the polypeptide hormone erythropoietin and part of the env protein of ecotropic Moloney murine leukemia virus was engineered into the virus. This murine virus became several times more infectious for murine cells bearing the erythropoietin receptor, and it also became infectious for human cells bearing the erythropoietin receptor. This type of tissue-specific targeting by means of ligand-receptor interactions may have broad implications to a variety of gene delivery systems.

The α-Globin Genotype as a Determinant of Hematologic Parameters in Sickle Cell Trait

ABSTRACT It has been predicted that the trimodal distribution of the percentages of hemoglobins containing either an α-globin mutant or a β-globin mutant is caused by differing numbers of α-globin genes in subjects heterozygous for the mutation. Using restriction endonuclease mapping as an objective measure of the number of α-globin genes present, we were able to demonstrate that the percentage of hemoglobin S in black sickle trait subjects is proportional to the number of α-globin genes present. We compared three hematologic parameters: hemoglobin concentration, mean corpuscular volume, and percentage of hemoglobin S to the number of α-globin genes present. Using the Hb concentration and the mean corpuscular volume of sickle trait subjects with four, three, or two α-globin genes allowed distinguishing the group of α-thalassemia trait (two α-globin genes) from the nonthalassemic group (four α-globin genes) and the silent carrier group (three α-globin genes). Comparing the mean percentages of Hb S it was possible to distinguish among all three groups.