Alternative splicing of human glucose-6-phosphate dehydrogenase messenger RNA in different tissues.

Different forms of glucose-6-phosphate dehydrogenase (G-6-PD) have been described in different tissues. Moreover, the directly determined amino acid sequence amino end of the red cell enzyme does not exactly match the sequence deduced from cDNA isolated from HeLa cells or lymphoblasts. We have therefore investigated the sequence of cDNA from sperm, granulocytes, reticulocytes, brain, placenta, liver, lymphoblastoid cells, and cultured fibroblasts. A novel human cDNA, which has extra 138 bases coding 46 amino acids, was isolated from a lymphoblastoid cell library. Sequencing of genomic DNA amplified by the polymerase chain reaction (PCR) revealed that the extra sequence was derived from the 3'-end of intron 7 by alternative splicing. This longer form of mRNA was also detected in sperm and granulocytes. Sequence analysis using PCR-amplified cDNA revealed that the 5'-end of the coding sequence of G6PD mRNA in reticulocytes is identical to those in other tissues.

Enzymatic diagnosis in non-spherocytic hemolytic anemia.

Blood samples from 722 unrelated patients with anemia and/or reticulocytosis were submitted to our laboratory for red cell enzyme assay during the past 7 years. Among these 722 cases, we found 82 cases of 7 different red cell enzyme deficiencies and 2 of unstable hemoglobin. Abnormalities of pyruvate kinase (PK) were found to cause hemolysis in 55 patients. Although their average PK activity was about 35% of the normal level, 5 showed normal and 2 demonstrated high PK activity. Among 17 patients in whom pyruvate kinase assays or screening tests had been carried out in routine laboratories, the correct diagnoses had been made in only 4. Glucose-6-phosphate dehydrogenase (G6PD) deficiency was found in 15 patients, pyrimidine 5'-nucleotidase deficiency in 5, glucose phosphate isomerase deficiency in 3, adenylate kinase deficiency in 2, phosphoglycerate kinase deficiency in 1, and glutathione synthetase deficiency in 1 patient. Even after we performed a panel of over 20 different red cell enzyme assays, 519 patients still remained undiagnosed.

Hereditary spherocytic anemia with deletion of the short arm of chromosome 8.

We describe a 30-month-old boy with multiple anomalies and mental retardation with hereditary spherocytic anemia. His karyotype was 46,XY,del(8)(p11.23p21.1). Genes for ankyrin and glutathione reductase (GSR) were localized to chromosome areas 8p11.2 and 8p21.1, respectively. Six patients with spherocytic anemia and interstitial deletion of 8p- have been reported. In these patients, severe mental retardation and multiple anomalies are common findings. This is a new contiguous gene syndrome. Lux et al. [1990: Nature 345:736-739] established that ankyrin deficiency and associated deficiencies of spectrin and protein 4.2 were responsible for spherocytosis in this syndrome. We reviewed the manifestations of this syndrome. Patients with spherocytic anemia and multiple congenital anomalies should be investigated by high-resolution chromosomal means to differentiate this syndrome.

Hemolytic crisis after excessive ingestion of fava beans in a male infant with G6PD Canton.

After ingesting fava beans, a 26-month-old Chinese-Japanese male infant showed a sickly complexion and yellowish-brownish skin and was hospitalized. Severe hemolytic anemia was observed on admission, and transfusion of 200 ml of packed red cells was required. Red cell enzyme assay revealed that the patient and the mother were deficient in glucose-6-phosphate dehydrogenase (G6PD). Subsequent molecular analysis showed that the patient had a missense mutation 1376 G to T (G6PD Canton) and his mother was a homozygote for the mutation. The patient was a son of a Chinese (Taiwanese) mother and a Japanese father. Although G6PD deficiency is rare in the original Japanese population, the number of "imported" cases could be rising rapidly. This is the first reported Japanese case of G6PD deficiency with G6PD Canton.

A new glucose-6-phosphate dehydrogenase variant G6PD Sugao (826C-->T) exhibiting chronic hemolytic anemia with episodes of hemolytic crisis immediately after birth.

A case of glucose-6-phosphate dehydrogenase (G6PD) deficiency associated with chronic hemolysis with episodes of hemolytic crisis immediately after birth is reported. The propositus was a 1-month-old Japanese male infant. Molecular analysis of the G6PD gene revealed a novel missense mutation (826C-->4T) in exon 8 predicting a single amino acid substitution, Pro276Ser. The mother was confirmed to be heterozygous for this mutation. We designated this novel class 1 variant as G6PD Sugao. Pro276 is a phylogenetically conserved residue that may play a significant role in dimer formation.

Three families with hereditary hemolytic anemia and pyrimidine 5'-nucleotidase deficiency: electrophoretic and kinetic studies.

Three new variants of pyrimidine 5'-nucleotidase (P5N) found in Japan were studied. They are characterized by slow electrophoretic mobility and a high Michaelis constant for cytidine 5'-monophosphate as has been described in previously reported cases, but are unique with respect to the thermostability test and in pH optima. P5N Kumamoto was thermostable and showed a markedly basic shift in the pH optimum. P5N Nagano was thermolabile and had a normal pH optimum. P5N Kurume was thermostable and showed a basic shift in the pH optimum. These data suggest that these variants have structural gene mutations and that they are clearly distinguished from previously reported cases.

Red cell enzymopathies as a model of inborn errors of metabolism.

The molecular abnormalities of erythroenzymopathies associated with hereditary hemolytic anemia have been determined using molecular techniques. Pyruvate kinase (PK) deficiency is the most common and well-characterized enzyme deficiency involving the glycolytic pathway and causing hereditary hemolytic anemia. We have identified six distinct missense mutations and a form of splicing mutation in 11 unrelated families with homozygous PK deficiency. Mutations located near the substrate binding site may change the conformation of the active site, resulting in a drastic loss of activity and severe clinical symptoms. Up to now, including these genetic defects, 21 missense, 1 nonsense and 2 splicing mutations, 2 insertions, and 3 deletions have been determined. G6PD deficiency is the most common metabolic disorder, and is associated with chronic and drug- or infection-induced hemolytic anemia. To date, sixty different mutations have now been identified. Except for three kinds of variants with small gene deletions or three nucleotide substitutions, all of those were found to be produced by one or two nucleotide substitutions. Molecular studies disclosed that all the class 1 variants associated with chronic hemolysis have the mutations surrounding either the substrate or the NADP binding site. Among rare enzymopathies, missense mutations have been determined in glucosephosphate isomerase deficiency, aldolase deficiency, triosephosphate isomerase (TPI) deficiency, phosphoglycerate kinase deficiency, and adenylate kinase deficiency. Compound heterozygous cases with missense mutation/nonsense mutation and missense mutation/decreased mRNA have been reported in TPI deficiency and diphosphoglyceromutase deficiency, respectively. In phosphofructokinase (PFK) deficiency, three kinds of 5'-splice junction mutations resulting in abnormally spliced PFK-M mRNA were identified. An exception is a hemolytic anemia due to increased adenosine deaminase activity. The basic abnormality appears to result from overproduction of structurally normal enzyme.

[A case of cervical myeloradiculopathy with positive serum anti-GT1a antibody].

A 19-year-old man with cervical myeloradiculopathy is reported. He was admitted to our hospital because of acute muscle weakness of upper limbs, which developed two weeks after respiratory tract infection. Neurologic examination revealed prominent muscular weakness of upper limbs. Deep tendon reflexes showed hyporeflexia in upper limbs and hyperreflexia in lower limbs. Serum IgG anti-GT1a antibody was detected by thin-layer chromatography and immunoblotting. Neck MRI revealed T2-weighted high intensity legions and swelling in spinal cord at third to sixth cervical segment. The muscular weakness and the cervical legion in MRI improved two weeks after steroid treatment. These findings indicate the involvement of cervical pyramidal tract as well as that of cervical roots in the patient. Neurological symptoms of the present case differed from those of pharyngeal-cervical-brachial variant (PCB) of Guillain-Barré syndrome, although serum anti-GT1a antibody was positive.

[Glutathione synthetase deficiency].

CASE REPORT: The patient was a boy born in June, 1990. The proband's father had a history of nonspherocytic hemolytic anemia. The patient was anemic at birth (Hb 11.9 g/dl) and had a hemolytic attack on postnatal day 2. His hemolysis became well compensated, and his second hemolytic episode occurred at three years of age. CLINICAL AND LABORATORY FINDINGS: The patient's mental development had so far been normal and he has no neurological symptoms. His only clinical manifestation has been compensated hemolytic anemia with a hemoglobin concentration of about 11.0 g/dl and a reticulocyte count of 3-6%. He was positive on the Heinz body formation test, and target cells were seen on his peripheral blood smear. The osmotic fragility test yielded slightly increased value. Decreased reduced glutathione (GSH) was observed (4.4 mg/dlRBC) (normal range: 63.9 +/- 9.6), and he also had decreased glutathione synthetase (GS) activity of 0.03 U/gHb (0.38 +/- 0.08 U/gHb). A diagnosis of GS deficiency was made. Decreased glutathione S-transferase (GST) activity was also found (0.57 U/gHb) (normal range: 6.65 +/- 1.20). DISCUSSION: GS deficiency has been reported in about 30 families all over the world. This patient was the first Japanese patient with red cell GS deficiency.

[Human red cell metabolism and its pathophysiology].

The erythrocyte is a highly differentiated cell which has simple but active metabolic pathways. It lacks a nucleus, mitochondria and ribosomes, while glycolysis, hexose monophosphate pathway and glutathione synthesis maintain a high activity. Glycolysis is the only energy producing pathway crucial for red cell function and survival. The main function of red cell hexose monophosphate pathway is to generate NADPH, which is indispensable for maintaining high levels of a potent antioxidant reduced glutathione. Rapoport-Luebering pathway and pyrimidine 5'-nucleotide system are unique metabolic pathways specific for red cells. The former produces 2,3-diphosphoglycerate and the latter dephosphorylates useless pyrimidine nucleotides derived from the degenerated RNA.

The impact of lesion length and vessel size on outcomes after sirolimus-eluting stent implantation for in-stent restenosis.

OBJECTIVES: We evaluated the predictors of recurrent restenosis and the impact of lesion length and vessel size on outcomes in patients treated with routine sirolimus-eluting stent (SES) implantation for in-stent restenosis (ISR) of bare-metal stent (BMS). METHODS: In this study, 250 consecutive patients with 275 lesions after SES implantation for ISR of BMS were enrolled. Follow-up angiogram was obtained in 239 patients with 258 lesions eight months after implantation (follow-up rate: 95.6%). We compared characteristics of patients and lesions between the two groups (the recurrent restenosis group and the no-restenosis group). RESULTS: Recurrent restenosis was angiographically documented in 43 lesions (16.7%). Recurrent restenosis was found in 30.4% with small vessel lesions (reference diameter of less than 2.5 mm, 92 lesions) and 23% with the diffuse type lesions (106 lesions). Seventy-two per cent of patients had a focal pattern of recurrent restenosis. Previously recurrent ISR lesions (odds ratio (OR) 1.94, 95% confidence interval (CI) 0.94 to 4.06, p = 0.05), reference diameter of less than 2.5 mm (OR 2.41, CI 1.05 to 5.41, p = 0.03), diffuse type restenosis (OR 4.48, CI 2.12 to 9.94, p = 0.0001) and dialysis patients (OR 4.72, CI 1.42 to 15.7, p = 0.01) were independent predictors of recurrent restenosis. CONCLUSIONS: Small vessels, diffuse type restenosis and dialysis patients were still the predictors of recurrent restenosis in patients treated with SES for ISR of BMS.

Human glucose-6-phosphate dehydrogenase: structure and function of normal and variant enzymes.

Glucose-6-phosphate dehydrogenase (G6PD) is a unique enzyme with many genetic variants. Recent progress in molecular biological techniques have provided several important findings about the structure-function relationship of human G6PD. A putative substrate glucose-6-phosphate binding (around Lys 205) and a putative 'structural' NADP binding site (around Lys 386) have been identified. A conservative segment (amino acid 38-44) near the N-terminus was proposed to be the possible second NADP binding region (amino acid 38-44). Analysis of amino acid substitutions of variants revealed that there might be some relationship between the position of substitution and the properties of variants.

Molecular cloning and nucleotide sequence of cDNA for human glucose-6-phosphate dehydrogenase variant A(-).

Glucose-6-phosphate dehydrogenase (G6PD; D-glucose-6-phosphate:NADP+ oxidoreductase, EC 1.1.1.49) A(-) is a common variant in Blacks that causes sensitivity to drug-and infection-induced hemolytic anemia. A cDNA library was constructed from Epstein-Barr virus-transformed lymphoblastoid cells from a male who was G6PD A(-). One of four cDNA clones isolated contained a sequence not found in the other clones nor in the published cDNA sequence. Consisting of 138 bases and coding 46 amino acids, this segment of cDNA apparently is derived from the alternative splicing involving the 3' end of intron 7. Comparison of the remaining sequences of these clones with the published sequence revealed three nucleotide substitutions: C33----G, G202----A, and A376----G. Each change produces a new restriction site. Genomic DNA from five G6PD A(-) individuals was amplified by the polymerase chain reaction. The base substitution at position 376, identical to the substitution that has been reported in G6PD A(+), was present in all G6PD A(-) samples and none of the control G6PD B(+) samples examined. The substitution at position 202 was found in four of the five G6PD A(-) samples and no normal control sample. At position 33 guanine was found in all G6PD A(-) samples and seven G6PD B(+) control samples and is, presumably, the usual nucleotide found at this position. The finding of the same mutation in G6PD A(-) as is found in G6PD A(+) strongly suggests that the G6PD A(-) mutation arose in an individual with G6PD A(+), adding another mutation that causes the in vivo instability of this enzyme protein.

Identification of two novel deletion mutations in glucose-6-phosphate dehydrogenase gene causing hemolytic anemia.

Among over 50 distinct mutations causing glucose-6-phosphate dehydrogenase (G6PD) deficiency, only two deletion mutations have so far been reported. Using nonradioisotopic single-strand conformation polymorphism analysis, we found two additional deletion mutations in two Japanese G6PD-deficient patients with nonspherocytic hemolytic anemia. Case no. 1 had a 3-nucleotide deletion in exon 6 predicting a deletion of a serine at amino acid 188 or 189, which caused a class 1 variant G6PD Tsukui. Case no. 2 had a 3-nucleotide deletion in exon 5 predicting a deletion of a lysine at residue 95, which caused a class 2 variant G6PD Urayasu. The 188th serine, which might be deleted in G6PD Tsukui, is located close to the putative G6P binding site. The 188th serine is also involved in the amino acid substitution in G6PD Mediterranean, but the kinetics of these two variants are totally different. The residue with an amino acid deletion in G6PD Urayasu was distant from the substrate binding sites and was located in a region with low sequence homology among species. The different properties of variants having mutations in exons 5 and 6 suggest that these two exons code distinct functional domains of the enzyme.

Molecular abnormality of G6PD Konan and G6PD Ube, the most common glucose-6-phosphate dehydrogenase variants in Japan.

G6PD Konan and G6PD Ube are the most common glucose-6-phosphate dehydrogenase (G6PD) variants found in Japan. To clarify the molecular abnormality of these two variants, the entire coding region was amplified by polymerase chain reaction from genomic DNA (G6PD Konan) or cDNA (G6PD Ube). Direct sequencing revealed that both variants have the same nucleotide substitution (241 C to T) in exon 4, which predicts an Arg to Cys substitution at amino acid 81.

Isozymes of human erythrocyte pyrimidine 5'-nucleotidase--chromatographic separation and their properties.

The biochemical properties of two isozymes of human erythrocyte pyrimidine 5'-nucleotidase (P5N) separated by ion-exchange chromatography were studied. These two isozymes, P5N-I and P5N-IIB, can be distinguished from each other by substrate specificity, pH dependent activity and thermostability. P5N-I is thermolabile and dephosphorylates various pyrimidine 5'-monophosphates optimally around pH 7. UMP and CMP were found to be most effective substrates. P5N-IIB is thermostable and characterized by its high Michaelis constant and maximum velocity for dUMP or dTMP and acidic pH optima. The molecular weight was estimated to be 39,000 for P5N-I and 44,000 for P5N-IIB by gel filtration. These data suggest that these two isozymes are independent proteins and probably encoded by distinct structural gene loci.

cDNA cloning of human R-type pyruvate kinase and identification of a single amino acid substitution (Thr384----Met) affecting enzymatic stability in a pyruvate kinase variant (PK Tokyo) associated with hereditary hemolytic anemia.

cDNA clones for human R-type pyruvate kinase (PK) were isolated from a human reticulocyte cDNA library, constructed by PCR with a single gene-specific primer. The full-length cDNA was 2060 base pairs long, and the cDNA encoded 574 amino acids, the same number as that by rat R-type PK. Compared with human L-type PK, R-type PK was 31 amino acids longer at the amino terminus. We also cloned and characterized R-type PK cDNA clones from patients with hereditary hemolytic anemia from a PK deficiency, PK Tokyo. A single nucleotide substitution (ACG to ATG) was found at nucleotide 1151 of the coding sequence of the R-type PK, which caused an amino acid substitution, Thr384----Met. Dot blot hybridization of PCR-amplified genomic DNA from patients and their parents by allele-specific oligonucleotide probes showed that the parents, who were second cousins, were heterozygous. To confirm that the nucleotide change was responsible for the variant phenotype, we expressed the L-type PK with the single amino acid change in Escherichia coli and characterized the enzyme. The variant PK was thermolabile and moved slowly in the polyacrylamide gel buffered in 10 mM Tris.HCl, pH 8.3; these characteristics were fully compatible with data obtained from the patient's PK. From these results, we concluded that enzymatic stability of the variant was affected by the point mutation of the PK-encoding gene.

G6PD Nara: a new class 1 glucose-6-phosphate dehydrogenase variant with an eight amino acid deletion.

In the course of molecular studies on Japanese glucose-6-phosphate dehydrogenase (G6PD) variants using single-strand conformation polymorphisms (SSCP) analysis, we found an unusual class 1 G6PD variant that had nucleotide deletion in exon 9. The patient showed chronic nonspherocytic hemolytic anemia associated with frequent episodes of severe hemolytic attack. The hemolysate exhibited no measurable activity. Although the partially purified enzyme had detectable activity, we could not perform kinetic studies because of its extreme instability. Nucleotide sequencing showed a unique 24 bp deletion at nucleotide 953-976 that predicts an eight amino acid deletion of TKGYLDDP at residue 319-326. While this is one of the most drastic structural alterations found in G6PD variants, the region with the amino acid deletion was distant from both the G6P and NADP+ binding sites and was located in a domain with low sequence homology among species. The comparatively low functional importance of the deleted region may have saved the patient from lethal tissue dysfunction.