The erythrocyte membrane abnormality of hereditary spherocytosis

Analysis of the red cell membrane in a family with hereditary elliptocytosis--total or partial of protein 4.1

In a 12-year-old boy carrying a clinically silent elliptocytosis, we observed a total lack of red cell membrane band 4.1. Band 4.1 was partially absent in the father who also displayed a clinically silent elliptocytosis and, remarkably, in the mother although she presented normal discocytes. Band (2 and 2.1.) phosphorylation was sharply reduced in the three persons examined. In the propositus and his mother, but not in his father, a clearly phosphorylated band appeared at the level of band 4.2. We suggest that the father and the mother carry two distinct alleles affecting differently the interactions within the spectrin-actin protein 4.1 complex. The father's allele is elliptocytogenic in the heterozygous state and, among other molecular alterations, prevents the attachment of protein 4.1. The mother's allele is morphologically silent in the heterozygous state, yet it also affects the binding of protein 4.1, possibly because the latter is shortened. The propositus, being doubly heterozygous, has the same morphological phenotype as his father, but his protein 4.1 electrophoretic phenotype is the addition of both parental phenotypes. The distinct phosphorylation patterns in the region of bands 4.1 and 4.2 are also consistent with the two-allele hypothesis.

Thrombocyte aggregation in hereditary spherocytosis

Thrombocyte function was studied in seven splenectomized patients and one unsplenectomized patient with hereditary or congenital spherocytosis (HS). Adenosine diphosphate (ADP) concentrations, which trigger the aggregation of control thrombocytes, induced only a release reaction in thrombocytes from six of the HS patients. Collagen-induced thrombocyte aggregation was also diminished in two patients, and epinephrine-induced thrombocyte aggregation in one patient. Two patients whose thrombocytes responded normally to ADP, collagen and epinephrine, were identical twins with spherocytosis of equivocal hereditary. Ristocetin-induced aggregation was normal in all the patients studied. Xanthines (pentoxifylline, theophylline) had no effect on the aggregation of thrombocytes from HS patients or controls. Half-life of thrombocytes was normal in the two splenectomized patients studied. The results demonstrate that not only red cells but also thrombocytes are defective in HS.

Hereditary spherocytosis of man. Altered binding of cytoskeletal components to the erythrocyte membrane

Human erythrocytes possess a lattice work of extrinsic proteins on the inner face of the membrane (;cytoskeleton') that maintains the shape and deformability of the cell. The major proteins of the cytoskeleton are spectrin and actin, which are attached to the membrane by protein bands 2.1 (;ankyrin') and 4.1. The interactions of spectrin/actin with erythrocyte membranes from normal subjects and from patients with hereditary spherocytosis (HS) have been studied by using an air-driven ultracentrifuge, which can rapidly separate membranes from soluble proteins (150000g for 30s). The total amount of spectrin/actin in HS and normal ghosts is similar. However, the rate of dissociation of spectrin and actin from HS erythrocyte membranes at low ionic strength is significantly lower than that observed for normal membranes. Spectrin and actin isolated from either HS or normal membranes re-associated in a similar manner to spectrin/actin-depleted vesicles prepared from normal cells. Scatchard analysis showed an average binding capacity of 278mug/mg of membrane protein. However, spectrin/actin-depleted vesicles prepared from HS cells bound significantly less spectrin/actin prepared from either the normal or abnormal cells (average binding capacity 158mug/mg of membrane protein). The defect was defined further by studying the cytoskeleton obtained by Triton X-100 extraction of membranes. Under conditions of low ionic strength cytoskeletons prepared from HS membranes dissociated more slowly than those prepared from normal membranes, and only 80% of the protein from HS cytoskeletons could be solubilized after 180min compared with 100% for normal cytoskeletons. The difference between HS and normal membranes, which persists in isolated cytoskeletons, suggests that alterations in either the primary structure or the degree of phosphorylation of protein bands 2.1 or 4.1 may be central to the molecular basis of hereditary spherocytosis.

Plasma and erythrocyte lipids in hereditary spherocytosis

Determinations were made of the concentrations of cholesterol, triglycerides and phospholipids in plasma from 18 patients with hereditary or congenital spherocytosis (HS). The plasma cholesterol and phospholipid levels of these patients were significantly depressed, whereas the triglyceride levels were normal. Phospholipids from plasma and red cell ghosts were analysed by thin-layer chromatography. The relative amount of phosphatidylethanolamine was decreased in both plasma and red cell membranes from HS patients, whereas significant alterations were not observed in the relative amounts of the other major phospholipid classes. These data show that in HS the abnormal lipid metabolism is not confined only to the red cell; it also affects the plasma lipids and therefore probably other cells as well.

Fatty acid composition of erythrocytes in hereditary spherocytosis

The fatty acid distribution of the four major phospholipids has been determined in the erythrocytes of five patients with hereditary spherocytosis and in five control subjects. In contrast to a report by other workers, we are unable to confirm their findings of a defect in fatty acid chain lengthening activity leading to disappearance of long chain fatty acid conjugates of more than 20 carbon atoms in some of the phospholipid fractions.

Kinetics of red cell membrane phosphorylation: altered affinity of HS membrane protein acceptors

Membrane ghosts were prepared from red blood cells of normal and hereditary spherocytosis (HS) subjects. Time dependent phosphorylation studies of the membrane (in the presence of gamma labelled AT32P) showed that the HS membrane appeared to incorporate less phosphate than the normal membrane but the results were not significantly different. Using the initial linear rate of phosphorylation and varying the ATP concentration, it was found that the Michaelis constant (Km) for the normal membrane was 24.8 microns ATP and Vmax was 0.120 nmol phosphate bound/mg membrane protein/min. These values for the HS membrane were found to be 39.0 and 0.118 respectively. In one family the affected mother and son each showed a positive cooperativity effect for similar reciprocal plots. This indicates that phosphorylation of various HS membrane proteins may be an ordered rather than random process and suggests biochemical heterogencity of the HS condition. The constants, Km and Vmax, however, were found to be similar to the rest of HS subjects studied. Crude extracts of the enzyme protein kinase, which catalyses the membrane phosphorylation, showed no significant difference in the Km and Vmax value in HS compared with that from normal red cells. The kinetic difference in phosphorylation is probably due to abnormalities in the membrane protein(s) which accept the phosphate from protein kinase in HS red cells.

Investigation of poikilocytic normochromic normocytic anemia. 1. Round and elongated forms

Occasional nonspecific poikilocytes are found in most normal blood smears, but dominance of one or more forms of poikilocytes usually is indicative of a specific anemia or disease in an organ or organ system. For example, stomatocytes are most commonly associated with acute alcoholism, while teardrop cells classically reflect "spent" polycythemia vera or myelofibrosis. The clinical significance of the various round poikilocytes (spherocytes, stomatocytes, target cells) and elongated poikilocytes (ovalocytes and elliptocytes, teardrop cells, sickle cells) is discussed.