Presence of erythroid and nonerythroid spectrin transcripts in human lens and cerebellum

Spectrin is a major protein of the red cell membrane, and is composed of alpha- and beta-subunits. While spectrin was initially thought to be specific for erythrocytes, similar, but nonidentical peptides have recently been identified in other tissues, including lens, suggesting the existence of a spectrin gene family. To study the nature of spectrin-like peptides in the lens, we examined the transcription of erythroid and nonerythroid spectrin in human lens and cerebellum by direct hybridization with known human alpha- and beta-spectrin cDNA (erythroid probes), as well as with a human alpha-fodrin cDNA (nonerythroid probe). Northern blots of poly(A)+ RNA from erythroid, as well as several nonerythroid cells, and the total RNA from lens, showed that the beta-spectrin cDNA probe hybridized to two distinct bands of 8.6 and 7.4 kb mRNA in human lens, and was present in abundance. The erythroid beta-spectrin 11 kb mRNA transcript was also found in the human cerebellum. The beta-spectrin transcripts from these nonerythroid tissues were found to have different sizes compared to the major erythroid 7.8 kb beta-spectrin mRNA. Human lens contained a 7.5 kb transcript of the erythroid alpha-spectrin subunit. In addition, the human lens was found to have a 7.2 kb alpha-fodrin transcript; while the cerebellum had an 8.5 kb alpha-fodrin mRNA, the same size as that found in other nonerythroid tissues. The abundance of erythroid and nonerythroid spectrin transcripts in lens was significantly greater than in any other tissues examined. These data show that the human lens has abundant erythroid alpha- and beta-spectrin transcripts, as well as a unique alpha-fodrin transcript.(ABSTRACT TRUNCATED AT 250 WORDS)

Viscoelastic properties of red cell membrane in hereditary elliptocytosis

The viscoelastic properties of the RBC membrane are in part determined by a submembrane network of proteins consisting of spectrin alpha beta heterodimers (SpD) assembled head-to-head to form spectrin tetramers (SpT) and spectrin oligomers (SpO). SpT, in turn, are connected into a two-dimensional network by the linkage of distal ends of SpT to protein 4.1 and actin. With the micropipette technique, we determined the membrane viscoelastic properties of RBCs from a subset of patients with hereditary elliptocytosis (HE); these RBCs exhibit membrane skeletal instability, defective SpD self-association, and a molecular defect in the alpha I domain of spectrin, which is involved in the SpD-SpD contact (HE SpD alpha-SpD). The elastic modulus and viscosity of the membrane were significantly higher for the HE RBCs than for the control cells. Incubation of normal cells with N-ethyl-maleimide (NEM) produced a similar defective SpD self-association and a significant increase in the viscoelastic parameters of the membrane. The data provide evidence that the mode of assembly of membrane spectrin in the cytoskeletal protein network plays a major role in determining the rheologic behavior of erythrocyte membrane.

Characterization of a new G6PD variant: G6PD Titusville

We describe a new glucose-6-phosphate dehydrogenase mutant, G-6-PD Titusville. The propositus is a 7-month-old black male infant with a transient hemolytic episode. The mutant enzyme is characterized by abnormal electrophoretic mobility, thermolability, Km for NADP, abnormal deamino NADP use and a decreased sensitivity to inhibition by NADPH. G-6-PD activity of hemolysate, as measured under optimal in vitro conditions, was not initially decreased, whereas fibroblasts, granulocytes, and platelets showed a markedly decreased level of enzyme activity. These properties identify G6PD Titusville as a unique variant of this X-linked, housekeeping enzyme. We conclude that although the propositus with G6PD Titusville had a transient hemolytic episode, we cannot be certain whether this association was a causative one.

Spectrin-alpha I/61: a new structural variant of alpha-spectrin in a double-heterozygous form of hereditary pyropoikilocytosis

Recent biochemical studies have led to the identification of abnormal spectrins in the erythrocytes of patients with hereditary pyropoikilocytosis (HPP) and hereditary elliptocytosis (HE). In this report we describe the biochemical characterization of the erythrocytes from a proband with severe HPP who is doubly heterozygous for two mutant spectrins (Sp): Sp alpha I/74 and a new, previously undetected, mutant of alpha-spectrin designated Sp alpha I/61. The proband's erythrocytes are unstable when exposed to 45 degrees C, and her membrane skeletons exhibit instability to shear stress. The content of spectrin in the proband's erythrocyte membranes is decreased to 75% of control values. The amount of spectrin dimers in crude 4 degrees C spectrin extracts is increased (58%) as compared with control values (6% +/- 4%). Limited tryptic digestion reveals a marked decrease in the normal 80,000-dalton alpha I domain, an increase in the 74,000-dalton fragment that is characteristic of Sp alpha I/74, and an increase in a series of new fragments of 61,000, 55,000, 21,000, and 16,000 daltons. Both parents are asymptomatic, but they have increased amounts of spectrin dimers (17% to 25%). Limited tryptic digestion of the father's spectrin demonstrates the presence of a previously identified abnormal spectrin (Sp alpha I/74) that is characterized by a decrease in content of the 80,000-dalton peptide and an increase in concentration of the 74,000-dalton peptide. The mother's spectrin digests show a decrease in the amount of 80,000-dalton peptide and the formation of new peptides of 61,000, 55,000, 21,000, and 16,000 daltons. The data indicate that this severe form of HPP is due to the inheritance of two distinct abnormal spectrins, Sp alpha I/74 and a new spectrin mutant, Sp alpha I/61.

RFLP of the X chromosome-linked glucose-6-phosphate dehydrogenase locus in blacks

The X chromosome-linked glucose-6-phosphate dehydrogenase (G6PD) A(+) variant is found in approximately 20% of blacks. Examination of the structure of the G6PD A(+) gene revealed that AT----GC transition occurred in the variant gene, resulting in the amino acid substitution Asn----Asp at the one hundred forty-second position from the NH2-terminal of the enzyme (Takizawa and Yoshida 1987). The nucleotide change created an additional FokI cleavage site in the variant A(+) gene; thus, the FokI fragment type of the variant A(+) DNA differs from that of the normal B(+) DNA. PvuII fragment type is also found to be polymorphic in blacks, but not in Caucasians. The majority of blacks, as well all nonblacks, have a major hybridization-positive fragment of approximately 4.0 kbp (PvuII type 1), while approximately 20% of blacks have a major fragment of approximately 1.5 kbp (PvuII type 2). The G6PD gene with PvuII type 2 contains an additional PvuII cleavage site approximately 0.7 kbp downstream from the mutation site of the G6PD A(+). Approximately 40% of the G6PD A(+) genes have PvuII type 2, while only approximately 10% of the G6PD B(+) genes are associated with PvuII type 2. The data indicate a statistically significant (X2 = 6.85, P less than .020) linkage disequilibrium between the G6PD types and the PvuII types at the G6PD locus.

G6PD Huntsville: a new glucose-6-phosphate dehydrogenase associated with chronic hemolytic anemia

We describe a previously unreported glucose-6-phosphate dehydrogenase (G6PD) variant. G6PD Huntsville was found in a Caucasian male, resident of Huntsville, Alabama who was investigated for otherwise unexplained chronic hemolytic anemia. An unusual feature of this unique, apparently hemolytic, G6PD mutant is that its red cell enzymatic activity has not been decreased. The mutant enzyme is unstable. Additionally, the enzyme variant is characterized by normal electrophoretic mobility, biphasic and slightly alkaline pH optimum, and abnormal kinetics for the natural substrates G6PD and NADP as well as the artificial substrates deamino NADP. Its activity for another artificial substrate 2-deoxy G6PD is normal. The inhibition constant for NADPH is normal. The subject has had no evidence of episodic jaundice.

Characterization of a new glucose-6-phosphate dehydrogenase variant: G6PD Central City

Glucose-6-phosphate-dehydrogenase deficiency is the most common disease-producing enzyme deficiency in man. This paper describes a new glucose-6-phosphate-dehydrogenase variant discovered during the evaluation of an episode of acute hemolytic anemia in a 62-year-old black male, which was temporally related to the ingestion of Tolbutamide. The hemolysis resolved within 10 days despite continuation of Tolbutamide. The erythrocyte glucose-6-phosphate-dehydrogenase activity was significantly decreased, and its electrophoretic mobility was indistinguishable from wild type enzyme, though faster on starch gel with tris, borate, and phosphate buffers. The enzyme had a biphasic pH optimum reduced Km for G-6-P and NADP, decreased utilization of deamino-NADP, and reduced Ki for NADPH. Because the kinetic properties of this enzyme were unique, we have designated it as G6PD Central City.

Fibrinogen Birmingham: a heterozygous dysfibrinogenemia (A alpha 16 Arg----His) containing heterodimeric molecules

Fibrinogen was isolated from the plasma of a 25-year-old female with a history of mild bleeding and several recent moderate to severe hemorrhagic episodes. Coagulability with thrombin approached 100% and varied directly with the time of incubation with the enzyme. High-performance liquid chromatography analysis of thrombin-induced fibrinopeptide release demonstrated retarded fibrinopeptide A (FPA) and fibrinopeptide B (FPB) release and the presence of an abnormal A peptide (FPA) amounting to 50% of the total. The same biochemical abnormalities were found in her asymptomatic father. Amino acid analysis and carboxypeptidase digestion of FPA demonstrated the substitution of His for Arg at A alpha 16. In contrast to the thrombin- and reptilase-sensitive Arg-Gly bond in the normal A alpha chain, the abnormal A alpha chain (A alpha) sequence is resistant to reptilase attack but is slowly cleaved by thrombin. To evaluate whether Birmingham A alpha and A alpha chains had been assembled nonselectively into heterodimeric (ie, 50% A alpha, A alpha) and homodimeric (ie, 25% A alpha, A alpha; 25% A alpha, A alpha) species, the clot and the clot liquor resulting from reptilase treatment of normal or Birmingham fibrinogen were separated, and each was then further incubated with thrombin to release remaining fibrinopeptides. Assuming that fibrinogen Birmingham contained heterodimeric molecules and that these and the normal molecules were completely incorporated into a reptilase clot, the expected coagulability would be 75%. In addition, subsequent thrombin treatment of the reptilase clot would release 50% of the total FPA and 75% of the total FPB present in the original sample. On the other hand, if only homodimeric fibrinogen species (50% A alpha, A alpha; 50% A alpha, A alpha) existed, the maximum reptilase coagulability would be 50%, and after thrombin treatment, 50% of the total FPB and no FPA would be recovered from the reptilase clot. We found the propositus's fibrinogen to be 68% coagulable, and we recovered 45% of the FPA and 70% of the FPB from the reptilase clot. Essentially the same coagulability and distribution of fibrinopeptides was found in the reptilase clot from her father's fibrinogen. We therefore conclude that fibrinogen Birmingham contains heterodimeric species (A alpha, A alpha) amounting to approximately 50% of the circulating fibrinogen molecules. The existence of heterodimers is consistent with a nonselective intracellular process of constituent chain assembly of dimeric plasma fibrinogen molecules.

Two apparent glucose-6-phosphate dehydrogenase variants in normal XY males: G6PD Alabama

A six-year-old black boy who had transient hemolysis after a viral infection was found to have mildly decreased red cell glucose-6-phosphate dehydrogenase (G6PD) activity (1.25 IU/g hemoglobin). Two G6PD bands, both slightly faster than normal G6PD B, were seen on electrophoresis in both the propositus as well as in his maternal grandfather. This is an unexpected finding, since the G6PD gene is located on the long arm of the X chromosome that is subject to X-chromosome inactivation, and available evidence indicates that it is present as a single functional copy in the human genome. The obvious possibility of duplication of the X chromosome was eliminated by cytogenetic analysis with G-banding. G6PD duplication is unlikely, since peripheral blood granulocytes, platelets, and lymphocytes; cultured skin and bone marrow fibroblasts; and Epstein-Barr virus-stimulated lymphocytes yielded only a single electrophoretic band with mobility identical to the slower band seen in crude red blood cell hemolysate. Study of partially purified red blood cell hemolysate G6PD also yielded a single band with identical mobility. Kinetic studies of the enzyme in the propositus and in three generations of his family identified a unique, previously unpublished G6PD mutant that is herein designated G6PD Alabama. Red blood cells were separated by density gradient into a reticulocyte-enriched, an intermediate, and a dense, older portion. Two distinct enzyme bands were identified on electrophoresis of hemolysate from the reticulocyte-enriched portion, but not from the other two portions. It is postulated that two transcriptional products of the mutant G6PD gene exist; one with a short half-life and detectable only in young red blood cells, and another with a longer half-life present in all cells. The existence of two distinct mutant genes in the genome or a unique post-translational form of the mutant G6PD detected only in reticulocytes cannot be excluded.

G6PD Viangchan: a new glucose 6-phosphate dehydrogenase variant from Laos

We describe a previously unreported glucose-6-phosphate dehydrogenase-(G6PD) variant. G6PD Viangchan was found in a Laotian immigrant to Calgary, Canada, and was characterized by severe enzyme deficiency, normal electrophoretic mobility, increased pH optimum, and abnormal kinetics for the natural substrates G6PD and NADP, as well as the artificial substrates 2-deoxy G6PD and deamino NADP. The inhibition constant for NADPH was decreased. The subject has no evidence suggesting chronic or episodic hemolysis.

Isolation and characterization of cDNA clones for human erythrocyte beta-spectrin

Spectrin is an important structural component of the membrane skeleton that underlies and supports the erythrocyte plasma membrane. It is composed of nonidentical alpha (Mr 240,000) and beta (Mr 220,000) subunits, each of which contains multiple homologous 106-amino acid segments. We report here the isolation and characterization of a human erythroid-specific beta-spectrin cDNA clone that encodes parts of the beta-9 through beta-12 repeat segments. This cDNA was used as a hybridization probe to assign the beta-spectrin gene to human chromosome 14 and to begin molecular analysis of the gene and its mRNA transcripts. RNA transfer blot analysis showed that the reticulocyte beta-spectrin mRNA is 7.8 kilobases in length. Southern blot analysis of genomic DNA revealed the presence of restriction fragment length polymorphisms (RFLPs) within the beta-spectrin gene locus. The isolation of human spectrin cDNA probes and the identification of closely linked RFLPs will facilitate analysis of mutant spectrin genes causing congenital hemolytic anemias associated with quantitative and qualitative spectrin abnormalities.

Molecular determinants of clinical expression of hereditary elliptocytosis and pyropoikilocytosis

The clinical severity of common hereditary elliptocytosis (HE) is highly variable, ranging from an asymptomatic carrier state to a severe hemolytic anemia. To elucidate the molecular basis of this variable clinical expression, we evaluated 56 subjects from 24 HE kindred, who carry alpha spectrin mutants characterized by a spectrin dimer (SpD) self-association defect related to a structural abnormality of the alpha I domain of spectrin. Twenty-nine subjects had common HE, 13 subjects have a closely related disorder, hereditary pyropoikilocytosis (HPP), and 14 are asymptomatic carriers. We compared the severity of hemolysis with the following biochemical parameters: (a) spectrin heterodimer self-association, as manifested by the percentage of SpD in the 4 degrees C low ionic strength spectrin extract; (b) spectrin structure, as examined by limited tryptic digestion of spectrin; and (c) spectrin content of the RBC membrane. Our analysis indicates that the severity of hemolysis may be correlated with quantitative differences in the percentage of SpD in the 4 degrees C spectrin extract, as well as the total spectrin content of the membrane. Thus, HPP subjects, who have the most severe hemolytic anemia, have the highest percentage of SpD as well as a decreased spectrin content. HE subjects and asymptomatic carriers, respectively, have a lower percentage of SpD and a normal spectrin content. Factors influencing these two determinants include functional differences between the individual spectrin mutants, the relative amounts of mutant spectrin present in the cells, the stability of mutant spectrin, and the possibility of a superimposed genetic defect involving spectrin synthesis.

Analysis with antiidiotype antibody of a patient with chronic lymphocytic leukemia and a large cell lymphoma (Richter's syndrome)

A murine monoclonal antibody made against an idiotypic determinant (Id) of surface IgM/IgD lambda molecules on chronic lymphocytic leukemia (CLL) cells of a 71-year-old woman was used for clonal analysis by two-color immunofluorescence. The anti-Id antibody identified IgM+/IgD+/lambda+ B cells as the predominant cell type of her CLL clone. In addition, substantial proportions of the IgG and IgA B cells and most of the IgM plasma cells in her bone marrow and blood were Id+. Six years after diagnosis, the patient died of respiratory failure due to infiltration of lungs by malignant cells. Autopsy revealed a dramatic change in the tumor cell morphology. The lungs, hilar nodes, and liver were infiltrated by a diffuse large cell lymphoma admixed with the leukemic cells. By immunohistologic staining these anaplastic lymphoma cells were IgM+/IgD-/lambda+ B cells expressing the same Id noted earlier on the CLL cells. The immunoglobulin gene rearrangement pattern on Southern blot analysis was also the same in leukemic blood cells and in the tissues involved by the lymphoma. Thus, the combination of antiidiotype and immunoglobulin gene analyses in this patient with Richter's syndrome revealed that a CLL clone, seemingly "frozen" in differentiation, was actually undergoing isotype switching, differentiation into plasma cells, and evolution into a rapidly growing and fetal lymphoma.

Acute myelofibrosis and multiple chloromas of the mandible and skin

Acute myelofibrosis is a rare clinical entity characterized by severe marrow fibrosis and peripheral blood pancytopenia. It may be very closely related to and has been considered synonymous with megakaryocytic leukemia. Chloroma is also a rare entity composed of a localized collection of immature myeloid cells and is associated with a known or covert leukemia. A patient presenting with a rare combination of acute myelofibrosis, megakaryocytic leukemia and multiple chloromas of the mandible and skin, are described. Although presenting a diagnostic challenge, their combination in one patient aids in the understanding of the myeloproliferative process. To our knowledge, this is the 3rd case of chloroma involving the oral osseous structures.

Hemoglobin Long Island is caused by a single mutation (adenine to cytosine) resulting in a failure to cleave amino-terminal methionine

Hemoglobin Long Island has two separate amino acid abnormalities of beta-globin structure: an extension of the NH2 terminus by a methionine residue and a histidine-to-proline substitution at the normal second position. The NH2-terminal methionine residue, the translation product of an AUG initiation codon, is present only transiently in nascent proteins. Because of the general biological implications of this abnormality, we investigated the nature of the genetic defect of this mutant. We determined the sequence of the relevant portion of the beta-globin mRNA by means of dideoxynucleotide chain termination of the complementary DNA (cDNA) in which an oligonucleotide complementary to codons 10-17 was used as a primer for reverse transcriptase. A histidine-to-proline substitution was confirmed in the mutant mRNA by identifying an adenine-to-cytosine transversion in the second codon. However, we were unable to find any other abnormality at either the AUG initiation codon or in the 56 bases upstream from the adenine-to-cytosine transversion (encompassing most of the 5' untranslated region of the mutant beta-globin mRNA). Thus, it appears that this single lesion probably interferes with the poorly understood methionine-cleaving mechanism that modulates most of prokaryotic and eukaryotic proteins.

Translocation (6;9)(p23;q34) in acute nonlymphocytic leukemia: three new cases

Several recent reports have described cases of acute nonlymphocytic leukemia with a unique chromosome translocation, t(6;9)(p23;q34). We have studied three additional patients who have acute nonlymphocytic leukemia and t(6;9)(p23;q34). Our findings provide additional support for the suggestion that this translocation is yet another distinct cytogenetic abnormality associated with myeloproliferative disorders.

Autosomal dominant polycythemia

Two families with polycythemia inherited as an autosomal dominant trait are described. Serial hemoglobin determinations in multiple family members and RBC volume measurements in selected affected subjects documented their polycythemia. Measurements of arterial p02s, p50s, and blood oxygen affinity were normal in all affected individuals from each family who were tested. Erythropoietin (EPO) levels were low in affected individuals from family 1 and normal in affected members of family 2. Stimulation of in vitro CFU-E colony growth by low levels of EPO was significantly increased in subjects from family 1, but normal in those affected from family 2. We conclude that although the inheritance pattern for the polycythemia in both of these families appeared to be the same, the biologic defect leading to the disorder in each of these unique families was different. The precise mechanism of the increased EPO sensitivity noted in affected subjects from family 1 awaits elucidation.

Hb Long Island: a hemoglobin variant with a methionyl extension at the NH2 terminus and a prolyl substitution for the normal histidyl residue 2 of the beta chain

Hb Long Island was found in a diabetic man and his nondiabetic mother as the result of a routine clinical measurement of Hb AIc. It is present in amounts approximately equal to Hb A. Its alpha chains are normal but its beta chains have two alterations compared to the normal. A methionyl residue is attached to the usual NH2-terminal valyl residue. This valyl residue is followed by prolyl residue in place of the usual histidyl residue 2. The remaining sequence of the beta chain is normal. No hemoglobin or abnormal beta chain containing only the prolyl substitution could be detected by several different electrophoretic and HPLC procedures. We postulate that Hb Long Island is the result of a mutation in which a single nucleotide change causes the substitution of a prolyl residue for the normal histidyl residue at position 2 of the beta chain. We further postulate that this abnormal prolyl residue inhibits enzymatic cleavage of the initiator methionyl residue from the abnormal beta chain during posttranslational processing. Although the oxygen affinities of the whole blood, suspended cells, and hemolysate are normal, the affinity of the isolated Hb Long Island is slightly decreased and the effects of organic phosphates are reduced compared to normal. These changes are consistent with the loss of the normal histidyl residue 2 and the extension of the NH2-terminal end of the beta-chain molecule.

Immune hemolytic anemia following administration of antithymocyte globulin

Antithymocyte globulin is commonly used as a therapy for rejection of transplanted organs. Its use can be associated with many side effects. We report a significant hemolytic anemia following therapy with horse-derived antithymocyte globulin. Several commercial Coombs' sera failed to yield a positive Coombs' test with the patient's erythrocytes; however, we were able to detect horse immunoglobulin on the patient's cells as well as on control red cells incubated with this particular preparation of antithymocyte globulin.

Plasmacytoid T-cell lymphoma associated with chronic myeloproliferative disorder

This study reports the case of a patient who presented with evidence for a diagnosis of chronic myelogenous leukemia, as shown by blood and bone marrow analysis, and with generalized lymphadenopathy and splenomegaly. A lymph node biopsy revealed that the majority of the cells had plasmacytoid features but were consistently negative for surface or cytoplasmic immunoglobulin products, myelomonocytic surface markers, and peroxidase. Rather, lymph node plasmacytoid cells expressed T-cell markers (T 4/Leu 3+, T 10+), transferrin receptors (T 9+), and a proportion of them was also positive for sheep erythrocyte receptors (T 11/Leu 5+). This case is strikingly similar to a case reported by Lennert's group with respect to morphology, surface phenotypic features of the malignant plasmacytoid cells, and the association between a lymphoproliferative and a myeloproliferative disorder. This association suggests that plasmacytoid T-cells might exert a regulatory role on proliferation of myeloid cells.

Expression of NK-lineage markers on peripheral blood lymphocytes with T-helper (Leu3+/T4+) phenotype in B cell chronic lymphocytic leukemia

Heterogeneity within lymphocyte subsets expressing T-helper (T4+/Leu3+) or T-suppressor (T8+/Leu2+) markers was analyzed in 38 patients with B cell chronic lymphocytic leukemia (B-CLL) and in 11 age-matched controls. Co-expression of NK-lineage markers (M1, Leu7) on Leu2+ or Leu3+ cells was investigated by two-color immunofluorescence, and the proportion of granular lymphocytes within each subset was determined by cytochemical staining for acid phosphatase. B-CLL patients and normal controls had similar absolute numbers of cells per microL with T-suppressor phenotype. However, the proportion of Leu2+ cells co-expressing the Leu7 antigen was higher in the B-CLL patients than in the control subjects (54 +/- 3% v 27 +/- 4%, P less than .0001). The absolute number per microL of cells with T-helper phenotype was somewhat decreased in B-CLL patients compared with normal subjects (649 +/- 104 v 799 +/- 33, P less than .02), with a consequent decrease of the helper/suppressor ratio. Furthermore, co-expression of the Leu7 and, more strikingly, of the M1 markers was increased significantly on Leu3+ cells from B-CLL patients compared with normal controls (11 +/- 2% v 2 +/- 0.7%, P less than .002 for Leu7 and 40 +/- 5% v 4 +/- 1%, P less than .00001 for M1). Cytochemical studies showed that a large proportion of Leu3+ cells from B-CLL patients were granular lymphocytes, as suggested by the co-expression of natural killer (NK) cell markers. The emergence of a population of Leu3+ granular lymphocytes with NK markers, which is barely detectable in normal subjects, may provide an explanation for the impairment of T cell functions repeatedly described in B-CLL.