The characterization of protein 4.1 Presles, a shortened variant of RBC membrane protein 4.1.

In a previous report (Blood 60:265, 1982), we described a family with an abnormal RBC membrane protein doublet, which we considered a shortened protein 4.1 on the basis of biochemical and genetic data. Using an anti-4.1 monoclonal antibody, we confirm here that the shortened protein derives from protein 4.1. One of the members of the family contemporaneously displayed the 4.1 (-) trait, eg, the heterozygous state of this variety of hereditary elliptocytosis that lacks protein 4.1. The 4.1a/4.1b ratio was low whenever the 4.1 trait was present, regardless of the type of protein 4.1 involved. The RBCs of the compound heterozygote, containing only the shortened species of protein 4.1, made it possible to analyze without interference the contact between shortened protein 4.1 and sialoglycoprotein beta, or glycoconnectin. Shortened protein 4.1 did not alter the amount of glycoconnectin in the ghosts nor did it change its extractability into the Triton shells. Limited proteolysis of shortened polypeptides 4.1a and 4.1b showed that they are sequence related. It is conflicting that the persons carrying the shortened protein 4.1 are devoid of specific clinical and morphological abnormalities, apart from those pertaining to the 4.1- trait, when the latter is present.

Abnormal electrophoretic mobility of spectrin tetramers in hereditary elliptocytosis.

Hereditary elliptocytosis (HE) is a genetically determined disorder of the red cell membrane. The main protein which composes the proteinaceous skeleton of the membrane is an elongated molecule named spectrin which is a heterodimer composed of two chains, alpha and beta. In the membrane spectrin dimers are associated head-to-head to form tetrameric structures. We and other authors have reported that spectrin studied from many HE patients exhibited a dimer self-association defect (type I HE). A mutation in the head of the spectrin alpha chain was mostly found in type I HE. We have previously described one of the three known spectrin pathological variants shown on mild tryptic digest pattern. This variant was characterized by the appearance of an abnormal 65,000-dalton peptide (Sp alpha I/65). Using nondenaturating gel electrophoresis, we describe in this paper a triplicated pattern of the spectrin tetramer bands which is found in heterozygous HE cases displaying the 65,000-dalton variant. Study of a homozygous case allowed us to characterize the electrophoretic mobility of the abnormal symmetrical spectrin tetramer (alpha 2I/65-beta 2) and to study the correlation between the fraction of this abnormal symmetrical tetramer found in heterozygous patients and the amount of the 65,000-dalton peptide observed in spectrin tryptic digests.

Hereditary elliptocytosis: clinical, morphological and biochemical studies of 38 cases.

We report clinical, morphological and biochemical studies performed on 38 cases of hereditary elliptocytosis (HE). The major determinant of membrane shape and stability is a proteinaceous meshwork named membrane skeleton, composed mainly of spectrin, actin, protein 4.1 and ankyrin. Spectrin is a heterodimer composed of two chains alpha and beta. Two spectrin dimers associate head to head to form a tetramer. Spectrin tetramers are cross-linked by actin and protein 4.1 to form the skeletal meshwork. We observed two types of membrane defects in the 38 patients studied: 24 patients (13 kindreds) exhibited spectrin self-association defect (type I HE) and 14 patients (6 kindreds) displayed deficiency in protein 4.1. A mutation in the spectrin chain was mostly found in the cases of type I HE. These mutations were depicted on tryptic digest patterns of spectrin. Three pathological variants were thus identified and characterized by the appearance of an abnormal peptide, with a molecular weight of either 74,000 or 65,000, or 46,000 daltons. In one family, the spectrin self-association defect was related to a shortened spectrin beta chain. Deficiency in protein 4.1 was found in 14 patients by means of polyacrylamide gel electrophoresis of red cell membranes. In 12 heterozygous cases of HE, the decrease in the amount of protein band 4.1 was between 40% and 50%. In 2 homozygous HE cases, protein band 4.1 was totally absent. Immunoelectrotransfer blots of red cell membrane proteins using a monoclonal antibody against protein 4.1 allowed characterization of additional bands in two families. In some cases variations in the amount of glycophorin C were noticed. Comparative studies of the two types of membrane abnormalities in HE clearly showed the absence of correlation between clinical, morphological phenotypes, and specific molecular etiology. However, all HE patients with protein 4.1 deficiency were caucasian and most of the type I HE were of black extraction. A study of red cell deformability using an ektacytometer revealed that the cell deformability under isotonic conditions was decreased in all HE patients. When the deformability was studied as a function of the osmolality of the suspending medium, the curve obtained had a trapezoid shape. This typical profile appeared to be constant in type I HE. We showed that the molecular abnormalities of the spectrin alpha chain, found in most type I HE correlated well with the functional spectrin defect.(ABSTRACT TRUNCATED AT 400 WORDS)

Double inheritance of an alpha I/65 spectrin variant in a child with homozygous elliptocytosis.

Hemolytic anemia with red cell fragmentation, poikilocytosis, and elliptocytosis was discovered in a 6-week-old black infant. Both parents and a brother of the propositus had compensated mild Hereditary Elliptocytosis (HE). Elliptocytosis was prominent in the proband's father with the presence of numerous rod-shaped cells whereas, in the proband's mother, elliptocytosis was less marked and cells were less elongated than in the father. The proband's red cells fragmented at 45 degrees C instead of 49 degrees C for control cells. Both the parents' and brother's red cells fragmented at 47 degrees C. The deformability of the proband's red cells was markedly reduced when measured with the ektacytometer; the red cells of both the proband's parent and brother exhibited an intermediate decrease in red cell deformability. Spectrin self-association was defective in the propositus as well as in his parents and brother. Limited tryptic digestion of the proband's spectrin, followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), revealed a complete absence of the normal 80,000 dalton alpha I domain and the presence of an abnormal 65,000 dalton peptide. Two-dimensional isoelectric focusing/SDS-PAGE of limited tryptic digests of spectrin from both the proband's parents and brother revealed a decrease in the normal 80,000 alpha I domain and the presence of the 65,000 peptide variant. On the basis of biochemic studies performed on the patients' spectrin, we concluded that the proband had homozygous HE, having inherited the structural defect of spectrin present in a heterozygous state in each of his parents. On a clinical and morphologic level, homozygous HE imitates two other forms of congenital hemolytic anemia associated with a spectrin self-association defect: HE with pycnocytosis in infancy and Hereditary Pyropoikilocytosis. This report emphasizes the importance of confronting clinical and rheological as well as biochemical investigations in studying and discussing different entities.

Pathologic and nonpathologic variants of the spectrin molecule in two black families with hereditary elliptocytosis.

Five patients with hereditary elliptocytosis (HE) from two unrelated black families were studied. The patients had prominent elliptocytosis and a decreased erythrocyte resistance to heat treatment. In one infant blood smears showed elliptocytosis and poikilocytosis; his erythrocytes fagmented at a lower temperature than those of his mother and sister, both having typical mild HE. Defective dimer-dimer association was present in all patients. Limited tryptic digestion of spectrin and subsequent analysis by one- and two-dimensional electrophoresis revealed a similar and reproducible decrease in the 80,000-dalton peptide (alpha I domain) and the concomitant appearance of a 46,000-dalton peptide. All the patients had the polymorphism of the spectrin alpha II domain commonly observed in black populations. In addition, modifications relative to the alpha III domain were detected; similar variants were found in one black control subject out of 136 and are likely related to a genetic polymorphism of the alpha III domain. No differences were observed between the peptide patterns in the infant with poikilocytosis and those of his HE sister and mother.

Red cell membrane alteration involving protein 4.1 and protein 3 in a case of recessively inherited haemolytic anaemia.

We present 2 siblings with a severe congenital haemolytic anaemia. Red cells displayed a variety of abnormal shapes, including leptocytes, schizocytes and elliptocytes. Repeatedly, skeletal protein 4.1 appeared reduced by 30%. The 4.1a/4.1b ratio was normal despite the haemolytic state. No change could be detected in spectrin, nor in sialoglycoproteins. Band 3 was denser, narrower and displaced downward. The parents, who are consanguineous, were devoid of any obvious biochemical abnormality; however, their red cells were not normal. These 2 cases with reduced protein 4.1 clearly depart from 4.1 (-) hereditary elliptocytosis. The possibility of an altered binding of protein 4.1 to some other membrane component is discussed.

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

We report an unusual case of congenital dyserythropoietic anaemia (CDA). The propositus is a 25-year-old gipsy female presenting with a recessively inherited haemolytic anaemia. The diagnosis of CDA was based on erythrokinetic data and the morphological appearance of the erythroid precursors. The direct assay of HEMPAS antigen was negative. In peripheral blood there were 15% dacryocytes. The red cell membrane protein pattern was dramatically altered, with four major aberrant bands. Band a (mol wt 86,000) was at the lower edge of band 3, band b (mol wt 82,000) was below band 3, band c (68,000) and band d (67,000) were below band 4.2. In addition, there was an array of aberrant minor bands below band d. Gel densitometric determinations and immunological characterization showed that these bands did not derive from any of the major components of the membrane. In fact, membrane proteins appeared normal in many respects, although periodic acid-Schiff staining revealed an apparent decrease of sialoglycoproteins. The major aberrant bands a, b and c occur in very low amounts in controls. These bands, as well as band d, also exist in normal cytosol and were strongly increased in the propositus.

Prenatal diagnosis of hereditary elliptocytosis with molecular defect of spectrin.

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 pyropoikilocytosis and elliptocytosis in a Caucasian family. Transmission of the same molecular defect in spectrin through three generations with different clinical expression.

Hereditary pyropoikilocytosis (HPP) is a severe hemolytic anemia characterized by a material instability of the red cell membrane leading to cell fragmentation. This fragility may be correlated with functional and structural defects of spectrin. Most HPP patients have been black. We now report three HPP patients from a Caucasian family, the proposita and her two maternal uncles. The proposita's mother and daughter presented mild type I hereditary elliptocytosis (HE), while the proposita's father was clinically and hematologically normal. Our studies revealed a defective ability of spectrin to self-associate, resulting in an excess of spectrin dimer in 4 degrees C extracts in the three HPP patients and to a similar extent in HE relatives. Limited tryptic digestion of spectrin showed a molecular variant in the alpha I domain as expressed by a decreased amount of 80,000-dalton peptide with a concomitant increase in the 74,000-dalton peptide. Investigations in the proposita's father revealed no abnormalities of the erythrocyte membrane. The co-transmission of HPP and HE phenotypes in the same lineage might suggest variability in the clinical expression of the same molecular defect and lead us to discuss the hypothesis of a double heterozygosity in HPP patients.

Spectrin Nice (beta 220/216): a shortened beta-chain variant associated with an increase of the alpha I/74 fragment in a case of elliptocytosis.

We describe a new spectrin variant with a truncated beta-chain. It was discovered in a 17-year-old white boy presenting with intermittent jaundice and spleen enlargement. He also displayed numerous smooth elliptocytes. On sodium dodecyl sulfate-polyacrylamide gel, the truncated beta-chain (beta'-chain) appeared as an additional band of approximately 216 kilodaltons, migrating between spectrin beta-chain and ankyrin. It represented 30% of total beta-chain. The beta'-chain reacted with an antispectrin beta-chain monoclonal antibody. It failed to become phosphorylated when ghosts were incubated in the presence of [gamma-32P] adenosine triphosphate. Whole spectrin tetramerization was defective since the amount of spectrin dimer was increased in spectrin crude extract and the association constant of the spectrin dimer self-association was decreased. Spectrin whole tetramer isolated from spectrin crude extracts contained small quantities of beta'-chain. Spectrin tryptic peptides showed an increase of the 74,000-dalton fragment at the expense of the 80,000-dalton fragment. So far, the latter abnormality has been used to characterize a number of cases of hereditary elliptocytosis or pyropoikilocytosis with no other apparent change. In the present case, we consider that the abnormality is a consequence of the beta-chain alteration. The parents seemed asymptomatic. As a result, we regard this new spectrin variant as deriving from a de novo mutation.

A variant of erythrocyte membrane skeletal protein band 4.1 associated with hereditary elliptocytosis.

A family comprising three patients (a mother and two children) with mild hereditary elliptocytosis was studied. Each patient had prominent elliptocytosis, reduced red cell deformability, and normal erythrocyte thermal sensitivity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the erythrocyte membranes in each patient showed decreased levels of band 4.1 (approximately half of the normal value) and the presence of an additional band migrating below protein band 4.2. This additional band was shown to derive from protein 4.1. Comparative partial proteolytic mapping of protein 4.1 and the additional band revealed a number of common peptides. Enzyme-linked immunoelectrotransfer blots of the patients' erythrocyte membranes using a monoclonal antibody to protein 4.1 revealed that, in addition to protein 4.1, two other bands below protein 4.2 were stained; one of these bands migrated in the same position as the additional band detected in the Coomassie Blue-stained gels. Immunoblotting of the patients' whole cells using the antibody to protein 4.1 revealed that this altered band 4.1 occurred as such in the intact red cell. SDS-PAGE of protein 4.1 purified from one patient showed the presence of two lower molecular weight bands below protein 4.1; the lower band migrated in the same position as the additional band found on SDS-PAGE of the patients' erythrocyte membranes. The patient's purified protein 4.1 displayed a decrease of about 40% in the binding activity with crude spectrin extracted from normal controls. Spectrin-spectrin interactions were normal in the three patients. The additional band present in the patients' red cell membranes probably represents a proteolytic degradation product. This alteration, present both in whole cells and isolated membranes, might affect the intact cells in vivo. We suggest that the patients' erythrocyte membrane instability may be related to the presence of an abnormal protein 4.1 whose modulatory influence on the spectrin-actin interaction in the skeleton is defective.