Globin synthesis in severe and intermediate homozygous beta thalassemia in Israel

alpha-thalassemia caused by a 16 bp deletion in the 3' untranslated region of the alpha 2-globin gene including the first nucleotide of the poly A signal sequence

We have identified a 16 bp deletion in the 3' untranslated region of the alpha 2-globin gene, including the first nucleotide of the polyadenylation signal sequence. The propositus, her mother and one of her brothers, all heterozygotes for the above deletion, have mild microcytic anemia. This is the first description of a deletion in the alpha gene involving both the 3' untranslated region and the polyadenylation signal sequence, causing alpha-thalassemia.

Differing erythrocyte membrane skeletal protein defects in alpha and beta thalassemia

Thalassemic red cells show irregular morphology and maldistribution of glycoproteins and sialic acids. These changes are compatible with damage to the red cell membrane skeleton. To test this possibility, we systematically studied the interconnections of skeletal proteins in patients with a form of alpha thalassemia (HbH disease), in patients with beta thalassemia intermedia, and in normal individuals. Alpha- and beta-thalassemic spectrin functions normally in spectrin self-association, binding to normal inside-out vesicles (IOVs), and binding to actin in the presence and absence of normal protein 4.1. Binding of normal spectrin to beta: thalassemic IOVs is normal but alpha-thalassemic IOVs are defective and bind only half the normal amount of spectrin (66 +/- 5 vs. 120 +/- 16 micrograms spectrin dimer/mg IOV protein, respectively). A different defect is detected in beta thalassemia, in which protein 4.1 shows markedly reduced ability (48 +/- 7% of normal) to enhance the binding of normal spectrin to actin and a decreased ability to bind normal spectrin in a binary interaction, compared with normal protein 4.1 (24 +/- 1 and 43 +/- 1 micrograms protein 4.1/mg spectrin, respectively). As no quantitative deficiency of beta-thalassemic protein 4.1 is detected, we assume an acquired lesion is present, which affects about half of the protein 4.1 molecules. These findings indicate that specific, localized, yet different defects exist in the skeletal proteins of alpha- and beta-thalassemic red cells. The different molecular lesions imply that the mechanism of hemolysis and probably the interaction of unpaired globin chains with the membrane differs in the two diseases.

Disturbed patterns of globin chain synthesis in childhood monosomy 7 myeloproliferative syndrome

Two children with typical clinical and haematological features of monosomy 7 myeloproliferative syndrome are presented. Both children displayed decreased production of beta-globin chains and unbalanced high alpha/non-alpha synthetic ratios similar to those characteristic of homozygous beta-thalassaemia. These provide further evidence for the involvement of the erythroid line as part of the malignant clone, indicating neoplastic transformation of a pluripotential stem cell in this disease.

Bone marrow transplantation in beta-thalassemia major. The Israeli experience

The present report summarizes our experience in applying a new approach in bone marrow transplantation for the treatment of beta-thalassemia major. Ex-vivo pretransplant T-lymphocyte depletion with CAMPATH-1 was used for prevention of acute and chronic graft versus host disease and total lymphoid irradiation was added for the conditioning regimen for abrogation of potential rejection of T-cell depleted marrow allografts. Ten patients with homozygous beta-thalassemia major were 9-48 months of age (median 18.5 months) and received HLA-identical allogeneic T-cell depleted marrow after treatment with total lymphoid irradiation, busulfan and cyclophosphamide. Seven patients are alive and free of disease, 3-46 months post-transplantation. The actuarial probability of survival and of disease-free survival at two years was 70%. Three patients died: one of intracranial hemorrhage post-transplantation, one from busulfan interstitial pneumonitis, and one who rejected the first graft and developed fatal chronic graft versus host disease after a second transplant. Seven patients are alive and well with follow-up of 3-45 months, with no signs of acute or chronic GVHD. We conclude that T-cell depleted bone marrow transplantation is indicated for homozygous transfusion dependent young patients with beta-thalassemia who are minimally transfused, particularly in areas where optimal conventional therapy is not feasible.

Erythropoietin activity in the serum of beta thalassemic patients

Serum erythropoietic activity was determined in 32 patients with beta thalassemia major and intermedia. Quantitation was performed by an in vitro bioassay using rabbit erythroid precursor cells (CFU-E) either by colony assay or by 3H-thymidine uptake. 20 polytransfused beta-thalassemic major patients had erythropoietic activity (mean 89.3 +/- 36 milliunits/ml) which was not significantly different (p greater than 0.2) from normal individuals (51.3 +/- 32 milliunits/ml). 12 untransfused patients with beta thalassemia intermedia were found to have comparable serum erythropoietic activity (p greater than 0.01). These levels were much lower than those found in patients with aplastic anemia who had a comparable degree of anemia. We have shown that the low EPO activity in thalassemic patients was not due to experimental conditions (excess of ferritin, low transferrin) nor to specific inhibitors appearing in this disease. No correlation was found between the erythropoietic activity and sex or other clinical parameters of the patients such as severity of the anemia, splenectomy, iron chelation or transfusion therapy. 4 young thalassemic children (1-2 yr of age) studied had high erythropoietic activity ranging from 661 to 5793 milliunits/ml--significantly different from normal children of the same age. It is suggested, therefore, that a decrease in serum erythropoietin levels develops during the course of the disease.

Alterations in membrane protein and phosphorylation pattern in beta-thalassemic red blood cells

The architecture and phosphorylation pattern of RBC membranes were studied in intact RBC and ghosts of patients with beta-thalassemia intermedia. Electron microscopic studies showed severe morphological alterations in ghosts from spx thalassemic patients. The polypeptide pattern obtained on SDS-PAGE revealed a fourfold increase in globin content of ghosts from spx patients. In addition, multiple protein bands were detected migrating below band 4.2, accompanied by alterations in the band 3 zone. When membrane protein phosphorylation was examined by SDS-PAGE and auto-radiography following incubation of intact RBC with [32P]Pi, a reduced labeling of the normally phosphorylated polypeptides was found in the thalassemic RBC. In addition, new phosphorylated peptides appeared in the region of band 3 and below band 4. On the other hand, phosphorylation of isolated membranes with [gamma-32P]ATP showed no major differences in the labeling of the major phosphorylated proteins. An analysis of the initial rate of spectrin-band 2.1 phosphorylation obtained by counting the excised bands from the SDS gels showed that there was a twofold increase in spectrin-band 2.1-phosphorylation rate catalyzed by cAMP-dependent protein-kinase in the thalassemic ghosts, although no differences were found in the extent of spectrin phosphorability. The results are consistent with major changes in membrane protein disposition in thalassemic RBC, most probably caused by the precipitation of excess globin chains.