[HEREDITARY ELLIPTOCYTOSIS IN ICELAND].
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Hereditary elliptocytosis (HE) is, in the heterozygous state, a common mild congenital hemolytic disease. In contrast, homozygous elliptocytosis is a severe transfusion-dependent hemolytic anemia. The major determinant of red cell membrane shape and stability is a two-dimensional proteinaceous meshwork named membrane skeleton. Spectrin, the most important protein of the membrane skeleton, is basically a heterodimer composed of alpha and beta chains. Within the membrane, spectrin dimers self-associate to form tetramers. In type I HE spectrin dimer self-association is defective and an excess of spectrin dimer is present in the patient's red cell membranes. The defective self-association is often correlated with an abnormality of the spectrin alpha chain which is depicted by limited tryptic digest of spectrin. In a family previously studied by us (Dhermy et al., 1984), the search for a spectrin defect in the red cells of the fetus of the pregnant mother was indicated for the following reasons: the diagnosis of heterozygous type I HE with the same spectrin variant had been made in the mother as well as in the father. Moreover, homozygous HE had been recognized in one of the children born two years previously with a persistent and severe transfusion dependent hemolytic anemia. Preliminary studies of normal fetal erythrocytes at twenty weeks gestation have shown that fetal and adult spectrin molecules are identical. The results obtained in the fetus at risk allowed us to diagnose type I HE (though elliptocytes were not present in the blood) for the following reasons: (i) erythrocyte deformability was decreased (ii) spectrin self-association was defective with an excess of dimer species in the membrane (iii) limited tryptic digest of spectrin showed the same abnormal pattern as seen in the heterozygous mother, with a decrease in the 80,000-dalton peptide and a concomitant increase in the 74,000-dalton peptide. The heterozygous state, strongly suspected on the tryptic digest pattern of fetal spectrin, was confirmed when the mother gave birth to a baby who did not have hemolytic anemia during the first 18 months of life.
Hereditary elliptocytosis (HE) is a common disorder of erythrocyte shape, occurring especially in individuals of African and Mediterranean ancestry, presumably because elliptocytes confer some resistance to malaria. The principle lesion in HE is mechanical weakness or fragility of the erythrocyte membrane skeleton due to defects in alpha-spectrin, beta-spectrin, or protein 4.1. Numerous mutations have been described in the genes encoding these proteins, including point mutations, gene deletions and insertions, and mRNA processing defects. Several mutations have been identified in a number of individuals on the same genetic background, suggesting a "founder effect." The majority of HE patients are asymptomatic, but some may experience hemolytic anemia, splenomegaly, and intermittent jaundice.
Seven black patients with mild hereditary elliptocytosis (HE) from five unrelated families were studied. The erythrocytes of these patients exhibited an abnormal thermal sensitivity (between 45 degrees C and 47 degrees C instead of 49 degrees C). An important defect of spectrin dimer self-association was detected in two ways: (1) the proportions of spectrin dimer (SpD) extracted from membranes at 4 degrees C under low ionic strength conditions were increased between 25% and 56% (normal value 15% +/- 2%); (2) the spectrin dimer----tetramer conversion in solution were defective with an association constant value between 0.4 and 2.4 X 10(5) M-1 for a normal value of 6 +/- 0.4 X 10(5) M-1. Spectrin (Sp) from HE patients and normal volunteers (32 black and 22 white subjects) was submitted to limited tryptic digestion, followed by one- or two-dimensional separation of the peptides. Peptide patterns of crude Sp from all seven HE patients exhibited a marked and reproducible decrease in 80,000-dalton peptide (previously identified as the dimer-dimer interaction domain of the alpha-chain) and a concomitant appearance of a novel 65,000-dalton peptide. A minor fragment at 28,000 daltons was also decreased. Tryptic digestion of HE spectrin dimer and tetramer (SpT), isolated after the SpD self-association procedure in solution, revealed modifications (decrease in the 80,000-dalton peptide and presence of a 65,000-dalton peptide) predominantly in HE SpD when peptide patterns of HE SpT were quite similar to control SpT patterns. Immunoblots with anti-alpha-chain antibodies revealed that the 65,000-dalton peptide derived from the alpha-chain. Kinetic studies of Sp digestion showed that the 65,000-dalton peptide did not result from further digestion of a 74,000 intermediate and was not a precursor of 46,000- to 50,000-dalton peptides. These results show a new structural defect of Sp-alpha-chain, associated with a defective Sp dimer self-association in HE.
We examined erythrocytes from 18 patients with hereditary elliptocytosis. Spectrin from eight patients (referred to as type 1) was defective in dimer-dimer association as demonstrated in two ways. First, there was an increased amount of spectrin dimer with a concomitant decrease in tetramer as measured in erythrocyte membrane preparations extracted at 0 degrees C under low-salt conditions (the amount of spectrin dimer was 15-33% of total spectrin species compared with a normal range of 3-7%). Second, the equilibrium constants of spectrin dimer-dimer association were decreased in both solution and in situ membrane. Spectrin from the remaining 10 patients (referred to as type 2) showed normal dimer-dimer association. Membrane skeletons, produced from ghosts of both types of hereditary elliptocytosis by Triton X-100 extraction, were unstable when mechanically shaken. Because spectrin tetramers, but not dimers, can crosslink actin, we postulate that the defective spectrin dimer-dimer association in type 1 diminishes actin crosslinking and thus is responsible for membrane skeletal instability. A defective protein-protein association in type 2, however, remains to be identified.
The authors report 6 cases of hereditary elliptocytosis during a screening in one thousand (1,000) black persons. The analysis of these cases of elliptocytosis allow to draw the following conclusions: the frequency of the hereditary elliptocytosis varies between 0.6 to 1 per cent in Ivory Coast, the functional and structural analysis of spectrin show a high global frequency of the elliptocytosis of Model I in relation with an abnormally of alpha I domain of spectrin, all the cases detected don't give any clinical trouble.
Distal renal tubular acidosis (RTA) and hereditary elliptocytosis (HE) are apparently distinct, genetic conditions. We report a family with 3 children having both hereditary elliptocytosis and distal renal tubular acidosis. The simultaneous occurrence of these two conditions in three siblings could be due to covariations in the same family, although a possible contiguous gene syndrome for distal RTA and HE cannot be excluded. This report emphasises the importance of excluding a renal tubular defect in any child who presents with elliptocytosis and failure to thrive.
Sialoglycoprotein beta, a minor sialoglycoprotein of the red cell membrane, was studied in homozygous and heterozygous 4.1(-) hereditary elliptocytosis, a variety of hereditary elliptocytosis characterized by total or partial absence of protein 4.1. Erythrocytes were treated with the periodic acid-NaB3H4 procedure. Following polyacrylamide gel electrophoresis in the presence of SDS, labelled sialoglycoproteins were revealed by fluorography. (i) In the ghosts from the 4.1(-) homozygote, sialoglycoprotein beta was sharply decreased. It is not sure whether the residual material is sialoglycoprotein beta itself, or a distinct sialoglycoprotein migrating in the same place. In long exposure fluorograms, sialoglycoprotein gamma (a sialoglycoprotein related to sialoglycoprotein beta) also turned out to be reduced. In the homozygote's Triton-shells, sialoglycoprotein beta and gamma appeared completely absent. (ii) In the 4.1(-) heterozygote, sialoglycoprotein beta appeared slightly reduced, whereas sialoglycoprotein gamma appeared normal. Both of these proteins were extracted in seemingly normal amounts in the Triton-shells. These observations bring further support to the view that there is an interaction between skeletal membrane protein 4.1 and sialoglycoprotein beta, that is additional to other interactions between the former protein and the lipid bilayer and/or other transmembrane proteins.
Hereditary elliptocytosis (HE) is a group of hemolytic anemias characterized by the presence of elliptical erythrocytes. The underlying alterations lie in the proteins of the membrane skeleton. Defects of the alphaI domain of spectrin have been defined based on a decrease in the normal 80-kD alphaI domain and a concomitant increase in one or more lower molecular weight peptides. We have studied three Brazilian kindreds with black ancestry, who presented mild common spalphaI/50 HE. Our aim was to determine the molecular alteration responsible for the spalphaI/50 HE observed in these three kindreds and to evaluate the presence and influence of allele alphaLELY in the expression of this type of HE. In order to establish the molecular defect, exons 5, 6 and 11 were amplified and submitted to a nonradioactive single strand conformation polymorphism protocol. An identical band shift in exon 6 was observed in all 3 patients and their affected relatives. Direct sequencing of the amplification products of exon 6 showed the same molecular defect in all patients: a T-->C substitution, responsible for the L260P mutation. Allele alphaLELY, detected by PCR and restriction enzyme digestion, was present in the heterozygous form in the three propositi and was associated in trans with the elliptocytogenic mutation. Blood smears of the patients with HE and alphaLELY in trans showed pronounced elliptocytosis, poikilocytosis and a few small red cell fragments, whereas the blood smears of their relatives, who had HE without allele alphaLELY, showed mild common HE with a predominance of ovalocytes and the absence of poikilocytes. We conclude that allele alphaLELY does not lead to the worsening of clinical conditions when associated in trans with mild HE, but can be easily distinguished by a blood smear analysis. The predominance of the L260P mutation in the kindreds studied could be related to the colonization of Brazil during the slave trade by Africans from the Benin-Togo area, where this mutation is particularly common.
Two variant spectrins have been described in hereditary elliptocytosis (HE) and pyropoikilocytosis (HPP). Both are characterized by increased susceptibility of the alpha I (N-terminal) 80-kD domain to mild tryptic digestion, yielding peptides of 46-50 or 65-68 kD (T50a and T68 in our terminology). In this report we add a third unstable spectrin alpha I domain found in three kindreds with HE; alpha IT80 in this type of spectrin is cleaved by mild tryptic digestion to a 50-kD peptide (T50b) distinguished from T50a by its more basic isoelectric point. All three spectrins show impaired self-association to form oligomers. Intermediate tryptic peptides of the three unstable alpha I domains from HE spectrins were characterized by monoclonal immunoblotting and I125 limit peptide mapping and affinity purified using polyclonal anti-alpha IT80. Partial amino acid sequences of alpha I domain peptides were obtained from two unrelated patients for each of the three variant spectrins. T50a results from cleavage at arginine 250 or lysine 252 of alpha IT80; a proline replaced the normal leucine or serine at residues 254 and 255, respectively. T50b and a 19-kD peptide result from cleavage at arginine 462 or arginine 464; a proline replaced the normal residue 465 (in T19b) in one of the two patients studied. T68 results from cleavage at arginine 131. In both 68-kD peptides examined, a leucine is inserted at residue 150. The relationship of the sequence changes to the new tryptic cleavages, to the current model of alpha I domain structure, and to defective spectrin self-association is discussed.
Electron microscopic study of the spleen of an adult with hereditary elliptocytosis demonstrated features of erythrocyte pooling in the splenic cords with decreased red cells in transit through the basement membrane slits between the sinus littoral cells and decreased erythrocytes in splenic sinuses. Cordal reticulum cells, macrophages, and platelets were prominent. Light microscopy demonstrated relatively empty sinuses, and electron microscopy confirmed that the sinuses contained variable numbers of intact red cells. The morphology of the splenic red pulp in hereditary elliptocytosis was found to simulate that seen in hereditary spherocytosis but to a lesser degree.
It is generally considered that abnormality of the erythrocyte membrane skeleton co elliptocytes. There are, however, few reports of beta spectrin variants. We found a new variant of beta spectrin in a child and her mother. This report is the first case of abnormality of beta spectrin in Japan. The propositus was an 8 month-old girl who was first examined by us in 1988. On laboratory findings, she showed anemia, increased reticulocyte count and decreased haptoglobin concentration. Both peripheral blood smears of patient and her mother showed typical elliptocytosis and they were diagnosed as hereditary elliptocytosis. SDS-PAGE patterns of the red cell membranes of the propositus and her mother were characterized by the presence of an abnormal component migrating immediately below the spectrin chains. We confirmed that the abnormal spectrin appeared clearly at the expense of normal beta chain. The abnormal spectrin (M.W. 216,000d) makes up 16% of the total beta chain. The inheritance of our case was autosomal dominant. The present case is considered as a new spectrin variant.
Red cell membrane proteins have been examined in a family in which three children have severe transfusion-dependent homozygous hereditary elliptocytosis. The membranes in all three show a considerable excess of spectrin dimers over tetramers in spectrin extracts. The red cell membranes of their parents with heterozygous hereditary elliptocytosis show a lesser but significant increase in spectrin dimers. Some of the family members also have an alpha-globin gene deletion and haemoglobin D trait. The present results are the first demonstration of a defect of spectrin dimer-dimer association in homozygous elliptocytosis and provide strong support for the concept that this defect is the primary cause of the red cell abnormality in at least some families of hereditary elliptocytosis.
Heterozygous 4.1(-) hereditary elliptocytosis results from the absence of one haploid set of protein 4.1, a major component of the red cell skeleton. Two successive epidemiological investigations revealed fifteen probands in the French Northern Alps. The frequency of this disease seems to be very high in four small villages isolated in the Aravis mountains. The genealogical study shows that eleven probands share common ancestors who lived eight or ten generations ago in these villages. Thus there was probably a founder effect from one pair of ancestors, strengthened by endogamy. In contrast, four probands originate from another area and are not genealogically related. Recent results in molecular genetics support the present data.
Hereditary elliptocytosis in North Africa is frequently associated with the alpha I/65 spectrin variant, characterized by an abnormal alpha I 65-kD instead of the normal alpha I 80-kD peptide following limited trypsin digestion of whole spectrin. A similar variant (although it yielded a 68-kD fragment) has been shown recently, in two black patients, to result from the insertion of a leucyl residue at position 148 (Marchesi et al: J Clin Invest 80:191, 1987). In order to determine if the underlying molecular defect was the same in North Africans and blacks (who originate from both sides of the Sahara Desert), we performed analysis directly at the DNA level. Starting from the DNA of an Algerian alpha I/65 heterozygote in whom the mutation was associated with identifiable RFLPs, we cloned and sequenced the alpha-spectrin gene region, which includes the mutation. We thus identified an extra leucine codon (TTG) between codons 147 and 149, the coding sequence becoming CAG TTG TTG CTG instead of CAG TTG CTG. We then used the polymerase chain reaction (PCR) method and dot-blot hybridization of the amplified DNA with mutant and normal allele-specific oligonucleotides to screen the DNA from four other unrelated North African subjects with Sp alpha I/65 hereditary elliptocytosis. In all families we studied, these subjects were heterozygous for the TTG insertion. These results demonstrate that Sp alpha I/65 hereditary elliptocytosis has the same molecular basis in North Africans and blacks.