Aberrant pattern of red cell membrane and cytosolic proteins in a case of congenital dyserythropoietic anaemia

Defective organization of the erythroid cell membrane in a novel case of congenital anemia

In the present paper, we demonstrate the erythroid cell membrane unique properties in a previously characterized case of hemoglobin-H disease, associated with congenital dyserythropoietic anemia type-I features. In order to explain the patient's cell membrane distortions and the high affinity for the various intracellular inclusions, we studied its composition and structure in comparison to other anemic and non-anemic cases. Red cells from peripheral blood were fractionated into cellular, membrane and protein extracts. Membrane attached immunocomplexes were separated and collected by immunoprecipitation. The subcellular fractions were analyzed by SDS-PAGE electrophoresis and immunoblotted against a variety of erythroid-specific antibodies. The protein composition of the membrane was characterized by immunogold electron microscopy. In the membrane of the CDA-associated case, we identified sialic acid and protein deficiencies, formation of protein crosslinkings, excesses of bound globin and immunoglobulins and aberrant peptides. In contrast to the typical hemoglobin-H disease, the ghost-bound globin exhibited preferential attachment to the skeletal proteins than the band 3 and the skeleton-bound globin consisted not only of beta- but also of alpha-globin chains. Another hallmark, probably associated with the CDA defect, was the participation of glycophorins in the membrane-bound immunocomplexes and the pathological clustering of the latter in the membrane. This study strongly suggests that the result of the combinatorial effects on the diseased membrane created a unique profile, quite distinct from the one observed in several typical hemoglobinopathies. Our observations shed light into critical membrane alterations leading to hemolysis in the novel CDA-associated disease and probably into the CDA-I or CDA-I-like diseases.

The congenital dyserythropoietic anaemias

Congenital dyserythropoietic anaemias (CDA) are a category of rare genetic diseases that affect erythropoiesis. Dyserythropoiesis is associated with abnormal erythroblasts and leads to altered red cells, the amount of which is insufficient. There are three main, well-defined CDAs, CDA I, II and III. Their characterization is based on a careful examination of the bone marrow under light and electron microscopes. In addition, a number of rare or unique forms of dyserythropoiesis have been reported. At least with respect to CDA I to III, the clinical evaluation is reaching an ever increasing refinement: age of discovery, determinants of iron overload and/or biliary complications. Over the past few years, a more promising breakthrough has been the localization of the genes responsible for CDA I, II and III, that is, 15q15.1-q15.3, 20q11.2 and 15q21-q25, respectively. Epidemiological studies have now become possible. The identification of the genes is pending.

Congenital dyserythropoietic anaemias: clinical features, haematological morphology and new biochemical data

Three types of congenital dyserythropoietic anaemia (CDA) were originally identified on the basis of the pattern of dysplastic changes in the erythroblasts and the results of the acidified serum lysis test (Ham test). These were designated CDA types I, II and III. Several other types have been described subsequently and new forms continue to be reported. Some patients with CDA develop iron overload even without repeated blood transfusion and may present with the complications of severe iron overload. Dysmorphic features are seen in some cases, especially of CDA type I. In CDA type II, incomplete processing of N-linked oligosaccharides leads to a marked reduction of polylactosamines associated with band 3 of the red cell membrane. A few cases of CDA type III develop lymphoid neoplasms. Some of the Swedish cases of CDA type III have developed a retinal abnormality characterized by angioid streaks and macular degeneration. The chromosomal localizations of the disease gene in CDA types I and II and in the Swedish family with CDA type III are now known, but the identities of the mutant genes are still unknown. Cases of CDA type I have shown a partial haematological response to interferon-alpha, however the biochemical basis of this response is unclear. An important step in the diagnosis of sporadic cases of CDA is the exclusion of known causes of acquired dyserythropoiesis.

Circulating nucleated red blood cells following splenectomy in a patient with congenital dyserythropoietic anemia

A 24-year-old white female with a 10-year history of juvenile rheumatoid arthritis and splenomegaly developed numerous circulating nucleated red blood cells (NRBC) following splenectomy for chronic abdominal pain. Subsequent evaluation revealed the presence of a congenital dyserythropoietic anemia (CDA) with atypical features. Circulating NRBCs have been reported following splenectomy in three other cases of CDA, each of which had atypical features and did not fit into the customary classification of types I-IV. Follow-up of our patient at 4 years revealed no untoward consequences of persistent NRBCs in her circulation.

The 60 and 63 kDa proteolytic peptides of the red cell membrane band-3 protein: their prevalence in human and non-human primates

Three phenotypes based on the polymorphism of band-3 protein from human red cells are described. Limited proteolysis of intact red cells from most individuals (homozygotes) yields a peptide of 60 kDa, but in some cases (heterozygotes), there is also a 63-kDa peptide, and rarely only the single peptide of 63 kDa is found. This is the first description of the 63-kDa homozygote. The interpretation that the three phenotypes are controlled by two alleles of a single autosomal locus, with no dominance, is supported by population and family studies. The frequencies of the allele, which we designate as p63, is 0.041 +/- 0.0068 in Caucasoids and 0.125 +/- 0.0121 in Negroids. The electrophoretic profiles and molecular weights of the peptides obtained with several commercial proteases from Streptomyces griseus are similar to those obtained with chymotrypsin. Whereas band-3 protein in two New-World monkeys (Saimiri and Cebus) resisted pronase attack, an Old-World monkey (Macaca mulatta) was monomorphic for a 63-kDa fragment, and in an ape (Pan troglodytes), a doublet of 62 kDa and 64 kDa was found. Band-3 protein polymorphism appears to be a good marker for genetic differentiation in human populations.

Reduction of membrane band 7 and activation of volume stimulated (K+, Cl-)-cotransport in a case of congenital stomatocytosis

We report on a case of congenital stomatocytosis in a French boy presenting with a haemolytic anaemia requiring splenectomy at the age of 6. The red cells included 15-20% stomatocytes and displayed a marked increase of volume. Their osmotic resistance and density were reduced; however, their deformability was unaltered in isotonicity. Erythrocyte Na+ was high (27 mEq/l) and K+ low (65 mEq/l). The newly described (K+, Cl-)-cotransporter normally triggered by hypo-osmotic stress, was activated to maximal capacity. Membrane band 7 was reduced by 72%. From anamnestic data, the condition appears to have been transmitted by the father. The mother proved to be strictly normal on clinical, morphological, osmotic and biochemical bases. We suggest that the partly missing band 7 may play an important role in the genesis of stomatocytosis.