Hemoglobin biosynthesis in juvenile erythroleukemia: Evidence of imbalanced globin chain synthesis

Summary In three young patients with erythroleukemia in whom a partial reversion to the fetal pattern of erythropoiesis occured there was found additionally an imbalance of globin chain synthesis. The synthesis of - plus -chains exceeded that of the -chains. In contrast, physiologic hemoglobin F production occuring in newborn infants and increased hemoglobin F production due to rapidly regenerating erythropoiesis in hereditary spherocytosis and after acute erythroblastopenia are characterized by a well balanced globin chain synthesis. These studies indicate that in distinct cases of juvenile erythroleukemia the genuine reversion to fetal erythropoiesis may be associated not only with a depression of hemoglobin synthesis but also with an imbalanced globin chain synthesis. Unlike adult cases of erythroleukemia without reversion to fetal erythropoiesis the imbalance of globin chain synthesis seems to be a more generalized phenomenon in these cases of juvenile erythroleukemia which is not confined to a particular red cell population.Supported by the Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg, Schr 86/14 and Ga 148/5     

Translation of human globin mRNA: globin synthesis in cells containing Hb Leiden.

Most structurally abnormal hemoglobins are present in smaller amounts than HbA in the erythrocytes of heterozygous subjects. In the presence of a hemoglobinopathy, alpha and beta globin synthesis remains balanced with equal production of the two types of chains. In reticulocytes of subjects with Hb Leiden (beta 6 or 7 glu leads to 0) there is greater production of alpha than beta globin in vitro (beta/alpha = 0.67), and slightly more beta A is synthesized than beta Leiden (beta A/beta Leiden = 1.28). Differences in specific mRNA content, rates of initiation of chain synthesis, or rates of chain elongation could be responsible for such differential polypeptide synthesis. In the present study, the ribosomal assembly of beta A, beta Leiden, and alpha globin chains was examined in peripheral blood. The translation times of the three chains did not differ significantly (average times: beta A = 65.4 sec, beta Leiden = 70.8 sec, alpha = 53.5 sec). These results indicated that an altered rate of translation was not the source of the anomalous globin synthesis observed in vitro in cells containing Hb Leiden. The experiments suggested that the observed imbalance in alpha/beta production was due to either differential rates of initiation of globin chain synthesis or quantitative differences in the amounts of the specific mRNAs present in the cells.     

The Clinical and Biosynthetic Characterization of αβ-Thalassaemia

A Cypriot family is described in which three thalassaemia genes, α-thalassaemia 1, α-thalassaemia 2, and β–thalassaemia, are segregating. Two siblings are heterozygous for both α-thalassaemia 1 and β-thalassaemia while a third child has typical haemoglobin H disease. The α-thalassaemia β-thalassaemia combination, which is associated with an α/β chain production ratio of unity, produces a moderate degree of anaemia with marked hypochromia and morphological changes of the red cells together with increased rates of flux of potassium across the membranes, but the red cell survival is normal. These changes m red cell morphology and metabolism are very similar to those found in the sibling with haemoglobin H disease in whom there is gross imbalance of globin chain synthesis and shortened red cell survival. These results suggest that imbalanced globin chain production is the primary cause of shortened red cell survival in thalassaemia and that changes in membrane permeability are probably of secondary importance and may, at least in part, result from factors other than globin chain imbalance.     

The interaction of α thalassaemia with heterozygous β thalassaemia

S ummary . The α globin genotypes of 55 β thalassaemia heterozygotes have been determined by restriction endonuclease analysis to identify those with interacting α thalassaemia genes. A comparison of the haematological and haemoglobin synthesis findings of individuals with normal α genotypes (αα/αα) with those with one (- α/αα) or two (-α/-α) α genes deleted shows that the latter two groups have more balanced globin chain synthesis ratios, higher haemoglobin levels, and larger, better haemoglobinized red cells. This suggests that the degree of globin chain imbalance is a significant factor in determining the red cell characteristics in heterozygous β thalassaemia. Screening programmes for thalassaemia, based on the detection of low MCVs, could miss cases of the interaction of α and β thalassaemia.     

Erythrokinetics and iron status in heterozygous β thalassaemia, and the effect of interaction with α thalassaemia

Ferrokinetic studies, alpha globin gene mapping, and assessment of iron status have been carried out in 16 healthy subjects with heterozygous beta thalassaemia. Six subjects had coinherited alpha thalassaemia and had more balanced alpha/beta globin chain synthesis ratios than the remaining 10 subjects with uncomplicated heterozygous beta thalassaemia. The overall efficiency of erythropoiesis was significantly reduced in the latter group (mean 76 +/- 17 (SD)% of normal), but was indistinguishable from normal in subjects with coexistent alpha thalassaemia. Red cell survival was unimpaired in both groups, indicating that the defect was one of mild ineffective erythropoiesis rather than peripheral haemolysis. Values for total plasma iron turnover were normal or only slightly increased. This suggests a lack of any additional stimulus to erythropoiesis, which might normally be expected to compensate easily for the mild degree of anaemia. Uncomplicated heterozygous beta thalassaemia produces an extremely mild disorder of erythropoiesis, which is dependent on the imbalance between alpha and beta globin chain synthesis, and is not associated with a risk of serious iron overload.     

A family with segregating triplicated alpha globin loci and beta thalassemia

In this article we report a Sardinian family, in which a beta- thalassemia gene and a triple alpha-globin loci, counterpart of the rightward deletion type alpha-thalassemia-2, were segregating. The analysis of the genotype-phenotype correlations in the different family members allowed us to give an outline of the manifestations associated with different genotype combinations. The heterozygote for the triple alpha-loci showed no consistent abnormal clinical or hematologic characteristics and presented balanced alpha/beta-globin chain synthesis. In the homozygous state for this lesion, the only phenotypic expression was a slightly imbalanced globin chain synthesis. The combination of heterozygous beta-thalassemia with the heterozygous state for the triple alpha-globin loci produced no clinical manifestations and showed a hematologic phenotype indistinguishable from that of heterozygous beta-thalassemia. On the other hand, the combination of the homozygous state for the triple alpha-globin gene loci and the heterozygous state for beta-thalassemia produced a clinical picture of thalassemia intermedia with a very mild clinical course, minor increase of fetal hemoglobin (HbF) levels, and a pronounced imbalance of globin chain synthesis.     

Acquired hemoglobin H disease in idiopathic myelofibrosis.

A 68-year-old male, diagnosed 1 year previously as having myelofibrosis, developed hemolysis, red cell inclusions, and 37% Hb H. The alpha/beta globin synthetic ratio for circulating reticulocytes, determined by 3H-leucine incorporation and globin chain separation by carboxymethylcellulose chromatography in urea, was 0.049. When total RNA was purified from peripheral blood cells and translated in a wheat germ cell-free translation system, the alpha/beta ratio of the translation products was 0.26, indicating mRNA as a major cause of the globin synthetic imbalance. This study demonstrates that myelofibrosis is one setting in which acquired Hb H disease occurs; that the synthetic imbalance may be extreme; and that it can be associated with an imbalance in the activities of specific globin mRNAs.     

Synthesis of alpha, delta-beta and gamma chains by reticulocytes from two brothers homozygous for haemoglobin Lepore.

Globin chain synthesis has been investigated for the first time in 2 patients homozygous for haemoglobin Lepore, although the 2 brothers have the same haemoglobin genotype the severity of the diseases is very different. The purpose of this study was to try and find out the reason for the different severity in the clinical manifestations. In the 2 patients a different excess of alpha-chain synthesis was observed, the higher excess being present in the subject carrying the more severe anaemia. This result strongly suggests that in homozygous haemoglobin Lepore disease, as in beta-thalassaemia, the degree of globin chain imbalance is responsible for the clinical manifestations.     

Hb Yokohama [beta 31 (B13)Leu----Pro] detected as a de novo mutation in a Yugoslavian boy.

Hb Yokohama [beta 31 (B13)Leu----Pro] was observed in a young Yugoslavian boy as a de novo mutation. The child exhibited severe transfusion-dependent hemolytic anemia. The variant was detected and quantitiated at 10.5% by reversed phase high performance liquid chromatography. In vitro globin chain synthesis showed a slight imbalance with an alpha/beta ratio of 1.38. Structural characterization of the abnormal beta chain was done by high performance liquid chromatographic analysis, on material obtained by high salt precipitation. The mutation was confirmed by sequencing of the amplified DNA.     

Kinetic alterations of the red cell membrane phosphatase in alpha- and beta-thalassemia

We studied the red cell membrane neutral phosphatase, which is part of the Na+K+ ATPase, in several types of oxidative hemolytic anemias. We used an artificial substrate, the p-nitrophenylphosphate. In controls and in patients heterozygous for various unstable hemoglobins (Hb Hope, Hb K?ln, or Hb Hammersmith), the kinetics were of the Michaelis-Menten type. On the contrary, in nearly all patients with alpha- or beta-thalassemia, the kinetics displayed an abnormally biphasic character. The apparent Michaelis constant (KMapp) was significantly decreased. The biphasic character correlated with the imbalance of globin chain synthesis. The beta-mercaptoethanol markedly increased Vmax in controls, but had little effect on the biphasic kinetics. Omission of K+ abolished the biphasic kinetics. The abnormal kinetics failed to appear with another artificial substrate, the 4-methylumbelliferylphosphate, nor did it appear with ATP, the natural substrate. In vitro, H2O2 treatment of normal and thalassemic red cells was unable to induce or exaggerate, respectively, the biphasic kinetics, but generated alterations of a different nature. We suggest that the various kinetic alterations of the phosphatase in thalassemic syndromes originate from the imbalance of globin chain synthesis. However, the involvement of an oxidative process remains to be demonstrated.     

HB Yokohama [β31(B13)LEU→PRO] Detected AS A de novo Mutation in a Yugoslavian Boy

Hb Yokohama [β31(B13)Leu→Pro] was observed in a young Yugoslavian boy as a de novo mutation. The child exhibited severe transfusion-dependent hemolytic anemia. The variant was detected and quantitated at 10.5% by reversed phase high performance liquid chromatography. In vitro globin chain synthesis showed a slight imbalance with an α/β ratio of 1.38. Structural characterization of the abnormal β chain was done by high performance liquid chroma-tographic analysis, on material obtained by high salt precipitation. The mutation was confirmed by sequencing of the amplified DNA.     

Homozygous G gamma delta beta thalassaemia

This report describes the clinical and haematological findings in three siblings homozygous for G gamma delta beta thalassaemia in an Indian family. There was a mild to moderate anaemia and markedly abnormal red cell morphology. Haemoglobin analysis showed 100% Hb F, solely of the G gamma type, with a pancellular but uneven distribution. Considerable chain imbalance was detectable in globin synthesis studies. In contrast to five previously reported cases, these children were essentially asymptomatic and have never required transfusions.     

Ultrastructure and cell cycle distribution of erythropoietic cells in heterozygotes and homozygotes for haemoglobin E

S ummary. Marrow aspirates from heterozygotes and homozygotes for haemoglobin E (HbE) have been studied by electron microscopy and by the technique of combined Feulgen microspectrophotometry and ³H-thymidine autoradiography. The erythropoietic cells of heterozygotes did not contain any precipitated globin chains and the proliferating erythroblasts of such individuals showed no abnormality in their distribution in the different stages of interphase. By contrast, 0–1.5% of late erythroblast profiles and 3.1–12.8% of marrow reticulocyte profiles of homozygotes contained intracellular inclusions resembling precipitated α-chains. Although precipitated globin chains were not seen in the early polychromatic erythroblasts of homozygotes, the number of these cells in the G2 phase relative to that in the S phase was increased. These data indicate that there is (1) probably little or no imbalance of globin chain synthesis in heterozygotes, (2) a substantial degree of imbalance in homozygotes, and (3) a disturbance of erythroblast proliferation in homozygotes which cannot be attributed to the deleterious effects of detectable intracellular α-chain precipitates. The electron microscope and cell cycle distribution data in the homozygotes for HbE were similar to those in two heterozygotes for β thalassaemia.     

Homozygous G γλβ thalassaemia

Summary This report describes the clinical and haematological findings in three siblings homozygous for ^Gγ δβ thalassaemia in an Indian family. There was a mild to moderate anaemia and markedly abnormal red cell morphology. Haemoglobin analysis showed 100% Hb F, solely of the ^Gγ type, with a pancellular but uneven distribution. Considerable chain imbalance was detectable in globin synthesis studies. In contrast to the five previously reported cases, these children were essentially asymptomatic and have never required transfusions.     

Dinucleotide deletion in -alpha3.7 allele causes a severe form of alpha+ thalassaemia

We describe a family of Italian origin in which the father and his two children had hypochromia and microcytosis with normal iron status. All individuals underwent an uneventful clinical course and required no treatment. To investigate the molecular basis of this phenotype, which is a prerequisite for further genetic counselling, we revealed that all affected family members are carriers of a common form of alpha+ thalassaemia resulting from the deletion of 3.7 kb of the alpha-globin cluster (alphaalpha/-alpha3.7). However, this genotype alone could not account for the phenotype presenting in this family. Further characterization of the alpha-globin genes demonstrated an additional AC deletion in the vicinity of the initiation codon of the -alpha3.7 allele. This secondary mutation causes an additional impaired translation of the affected allele producing increased globin chain imbalance. This leads to a more severe phenotype, as heterozygotes for such mutation (alphaalpha/-alphaT) have hypochromic microcytosis and abnormal globin chain synthesis that mimic alpha0 thalassaemia trait (--/alphaalpha). Accurate genotyping of alpha globin determinant is absolutely required as there is a possibility that an interaction of this unusual double mutation with other common alpha0 thalassaemias (--/-alphaT) can give rise to a very severe, probably fatal, alpha thalassaemia.     

Globin Chain Synthesis in the Marrow and Reticulocytes of Beta Thalassemia, Hemoglobin H Disease, and Beta Delta Thalassemia

, , and globin chain synthesis inbone marrow and peripheral bloodreticulocytes were studied in two patients with thalassemia major, two withthalassemia intermedia, one with thalassemia minor, one with Hb H disease,and one with homozygous -thalassemia. Nine nonthalassemic patientsserved as controls. In thalassemiamajor, a marked imbalance of - to -chain synthesis was found in the bonemarrow as well as in reticulocytes. Theimbalance, however, was slightly moreevident in the latter. In the patientswith thalassemia intermedia and minorthe - to -globin chain ratios in thereticulocytes were of the same orderof magnitude, despite the marked clinical differences between thalassemiaintermedia and minor. A balanced synthesis was found in the bone marrowof the patient with thalassemia minor.The bone marrow globin synthesis inthalassemia intermedia was not studied. Contrary to that in Hb H diseaseand -thalassemia, the imbalancewas more apparent in the bone marrow. In the latter, no evidence for imbalance was detected in the reticulocytes. These results point out the needfor further studies on globin chain synthesis in the bone marrow and reticulocytes of patients With the variousthalassemia syndromes and the effectof the free globin chain pool on thoseresults.

Submitted on March 9, 1971 Revised on November 29, 1971 Accepted on February 12, 1972     

The Importance of the Genetic Picture and Globin Synthesis in Determining the Clinical and Haematological Features of Thalassaemia Intermedia

Twelve carriers of thalassaemia intermedia were studied. Their clinical and haematological picture was distinctly different from that in both heterozygotes and homozygotes for beta thalassaemia. Several genetic patterns were found responsible for thalassaemia intermedia: beta/delta beta thalassaemia, alpha 2 beta/beta thalassaemia-heterocellular HPFH. In a few subjects the genetic picture indicated that the patients were homozygous for beta thalassaemia, in spite of the mildness of the clinical situation. The lack of genetic uniformity was refelcted in very wide Hb A2 (2.5--8.7%) and Hb F (7.5--96.9%) ranges, as opposed to the noticeable degree of biochemical uniformity indicated by the very similar imbalance of globin chain synthesis: 0.33-0.54 for the non-alpha/alpha chain ratio in the peripheral blood. The mean for this parameter (0.43 +/- 0.05) was significantly different (P less than 0.001) from that observed in heterozygous carriers (0.60 +/- 0.10) and homozygous carriers (0.11 +/- 0.05) for beta thalassaemia. The marrow blood displayed a comparable pattern. It is therefore suggested that the severity of thalassaemia is attributable to the degree of chain synthesis imbalance.     

Assay of Thalassaemic Messenger RNA in the Wheat Germ System

Messenger RNA(mRNA) has been prepared from reticulocytes obtained from patients with different types of thalassaemia and assayed in the wheat germ system. Since normal human reticulocyte mRNA directs the synthesis of equal numbers of alpha- and beta-globin chains in this system it offers a rapid and simple technique for assaying mRNA in the thalassaemic disorders. In mRNA from beta+ thalassaemics the deficiency of beta-globin synthesis mirrored that observed in intact reticulocytes while that prepared from patients wiht haemoglobin H disease gave alpha/beta globin chain production ratios which showed consistently greater imbalance than was found in reticulocytes. Messenger RNA prepared from haemoglobin E-beta0 thalassaemics from Thailand directed no detectable beta-chain synthesis while that prepared from a betaO thalassaemic from Ferrara synthesized a fraction with the chromatographic characteristics of beta-globin chains.     

Embryonic erythroid differentiation in the human leukemic cell line K562.

K562 human leukemia cells synthesize embryonic hemoglobins after culture in the presence of hemin. We have rigorously identified these hemoglobins by globin chain analysis and peptide mapping. No adult hemoglobin could be detected, and beta-globin synthesis was less than 2 ppm of total protein synthesis. Persistent embryonic globin gene expression is known to occur as a consequence of globin gene deletions. However, restriction endonuclease mapping showed that the globin gene complexes in K562 cells are indistinguishable from normal. Hemin increased the rate of embryonic globin synthesis. The pattern of hemoglobin synthesis proved to be stable when cells from different laboratories were compared. One line, however, synthesized large amounts of Hb X and very little Hb Portland in response to hemin. Hb X has been previously detected in human embryos; we show here that it has the composition epsilon 2 gamma 2 and is diagnostic of imbalanced chain synthesis or "zeta thalassemia." We have identified several agents that induce hemoglobin synthesis in K562 cells. Different inducers induced different patterns of embryonic hemoglobin synthesis but never any adult hemoglobin synthesis.