11/24. Heterogeneity of the molecular lesions in inherited phosphofructokinase deficiency.Human phosphofructokinase (PFK; EC 2.7.1.11) exists in tetrameric isozymic forms. Muscle and liver contain the homotetramers M4 and L4, whereas erythrocytes contain five isozymes composed of M (muscle) and L (liver) subunits, i.e., M4, M3L, M2L2, ML3, and L4. Inherited defects of erythrocyte PFK are usually partial and are described in association with heterogeneous clinical syndromes. To define the molecular basis and pathogenesis of this enzymopathy, we investigated four unrelated individuals manifesting myopathy and hemolysis (glycogenosis type VII), isolated hemolysis, or no symptoms at all. The three symptomatic patients showed high-normal hemoglobin levels, despite hemolysis and early-onset hyperuricemia. They showed total lack of muscle-type PFK and suffered from exertional myopathy of varying severity. In the erythrocytes, a metabolic crossover was evident at the PFK step: the levels of hexose monophosphates were elevated and those of 2,3-diphosphoglycerate (2,3-DPG) were depressed, causing strikingly increased hemoglobin-oxygen affinity. In all cases, the residual erythrocyte PFK consisted exclusively of L4 isozyme, indicating homozygosity for the deficiency of the catalytically active M subunit. However, presence of immunoreactive M subunit was shown in cultured fibroblasts by indirect immunofluorescence with monoclonal anti-M antibody. The fourth individual was completely asymptomatic, had normal erythrocyte metabolism, and had no evidence of hemolysis. His residual erythrocyte PFK showed a striking decrease of the L4, ML3, and M2L2 isozymes, secondary to a mutant unstable L subunit. Identical alterations of erythrocyte PFK were found in his asymptomatic son, indicating heterozygosity for the mutant unstable L subunit in this kindred. These studies show that, except for the varying severity of the myopathic symptoms, glycogenosis type VII has highly uniform clinical and biochemical features and results from homozygosity for mutant inactive M subunit(s). The absence of anemia despite hemolysis may be explained by the low 2,3-DPG levels. The hyperuricemia may result from hyperactivity of the hexose monophosphate shunt. In contrast, the clinically silent carrier state results from heterozygosity for mutant M or L subunit. Of the two, the M subunit appears to be more critical for adequate glycolytic flux in the erythrocyte, since its absence is correlated with hemolysis.- - - - - - - - - - ranking = 1keywords = muscle (Clic here for more details about this article) |
12/24. Kinetic properties of erythrocyte phosphofructokinase in patients with type VII glycogenosis from two families--close similarity to liver type phosphofructokinase.The kinetic properties of phosphofructokinases (PFKs) from normal human liver, muscle and erythrocytes, and from erythrocytes of two unrelated patients with type VII glycogenosis (muscle PFK deficiency, McKusick 23280) were analysed in this study. Sensitivity to inhibition by ATP and to inhibition by 3-phosphoglycerate, 2-phosphoglycerate, phosphoenolpyruvate and citrate were quite different for muscle and liver PFKs. The kinetic characteristics of normal erythrocyte PFK were intermediate between those of muscle and liver PFKs. The kinetic constants of erythrocyte PFK of a patient in one family were indistinguishable from those in the other family. In addition, kinetic behaviour of residual PFK activity in erythrocytes from patients in the two families were quite similar to those of normal liver PFK. These results of kinetic analyses provide convincing evidence for the concept that normal erythrocyte PFK consists of muscle and liver type subunits. Residual erythrocyte PFK activity in type VII glycogenosis is thus concluded to reflect the activity of liver type PFK existing in patient's erythrocytes.- - - - - - - - - - ranking = 2.5keywords = muscle (Clic here for more details about this article) |
13/24. Muscle phosphofructokinase deficiency: abnormal polysaccharide in a case of late-onset myopathy.A 61-year-old woman with muscle phosphofructokinase (PFK) deficiency had mild limb weakness all her life but no cramps or myoglobinuria. For 5 years the limb weakness progressed. In muscle, PFK activity was 1% of normal and glycogen concentration was elevated (2.13%). By light microscopy, a minor component of the accumulated glycogen appeared as PAS-positive, diastase-resistant inclusions in 10% of muscle fibers. The inclusions had a filamentous fine structure that resembled the abnormal long-chain glycogen of brancher enzyme deficiency. iodine absorption spectra of both the inclusions and a diastase-resistant fraction of isolated glycogen resembled amylopectin. The abnormal polysaccharide in PFK deficiency may be related to greatly elevated concentration of muscle glucose-6-phosphate, an activator of the chain-elongating enzyme glycogen synthase.- - - - - - - - - - ranking = 120.75557762128keywords = cramp, muscle, limb (Clic here for more details about this article) |
14/24. Nonsense mutation in the phosphofructokinase muscle subunit gene associated with retention of intron 10 in one of the isolated transcripts in Ashkenazi Jewish patients with Tarui disease.Mutations in the human phosphofructokinase muscle subunit gene (PFKM) are known to cause myopathy classified as glycogenosis type VII (Tarui disease). Previously described molecular defects include base substitutions altering encoded amino acids or resulting in abnormal splicing. We report a mutation resulting in phosphofructokinase deficiency in three patients from an Ashkenazi Jewish family. Using a reverse transcription PCR assay, PFKM subunit transcripts differing by length were detected in skeletal muscle tissue of all three affected subjects. In the longer transcript, an insertion of 252 nucleotides totally homologous to the structure of the 10th intron of the PFKM gene was found separating exon 10 from exon 11. In addition, two single base transitions were identified by direct sequencing: [exon 6; codon 95; CGA (Arg) to TGA (stop)] and [exon 7; codon 172; ACC (Thr) to ACT (Thr)] in either transcript. Single-stranded conformational polymorphism and restriction enzyme analyses confirmed the presence of these point substitutions in genomic dna and strongly suggested homozygosity for the pathogenic allele. The nonsense mutation at codon 95 appeared solely responsible for the phenotype in these patients, further expanding genetic heterogeneity of Tarui disease. Transcripts with and without intron 10 arising from identical mutant alleles probably resulted from differential pre-mRNA processing and may represent a novel message from the PFKM gene.- - - - - - - - - - ranking = 3keywords = muscle (Clic here for more details about this article) |
15/24. Identification of three novel mutations in non-Ashkenazi Italian patients with muscle phosphofructokinase deficiency.We have identified three novel mutations in four non-Ashkenazi Italian patients with muscle phosphofructokinase (PFK-M) deficiency (Tarui disease). Patient 1 was homozygous for an A-to-C substitution at the 3' end of intron 6 of the PFK-M gene, changing the consensus splice-junction sequence AG to CG. The mutation leads to activation of two cryptic splice sites in exon 7, resulting in one 5 bp- and one 12 bp-deleted transcript. An affected brother was also homozygous, and both parents were heterozygous, for the splice-junction mutation. Patient 2 was homozygous for a G-to-C substitution at codon 39, changing an encoded arginine (CGA) to proline (CCA). Patient 3 was heterozygous for an A-to-C substitution at codon 543, changing an encoded aspartate (GAC) to alanine (GCC); the PFK-M gene on the other allele was not expressed, but sequencing of the reported regulatory region of the gene did not reveal any mutation.- - - - - - - - - - ranking = 2.5keywords = muscle (Clic here for more details about this article) |
16/24. A new variant case of muscle phosphofructokinase deficiency, coexisting with gastric ulcer, gouty arthritis, and increased hemolysis.Muscle phosphofructokinase (PFK) deficiency includes both clinically and genetically heterogeneous conditions. A 22-year-old man with muscle PFK deficiency due to previously unrecognized mutation was admitted because of gastric ulcer. He had noticed mild fatigability on vigorous exercise, but had never experienced painful cramps and myoglobinuria. His history included five time relapses of gastric ulcer and gouty arthritis at ages 19 and 21 years. His laboratory data showing impaired muscle glycolysis, increased hemolysis, and myogenic hyperuricemia had aspects in common with those reported for the classic form of this disease, except that lactate concentrations in his blood increased considerably after exercise. The mutant PFK enzyme of this patient, who was demonstrated to have a missense mutation, could exert some catalytic activity that permitted glycolytic flux in vivo, thus leading to the absence of typical myopathic symptoms. The association of relapsing gastric ulcer with muscle PFK deficiency was detected for the first time. There is a possibility that oxygen radical-induced tissue damage resulting from increased hypoxanthine on exertion plays a role in the pathogenesis of ulceration, since the patient is more tolerant to exercise than reported cases with the classic form of muscle PFK deficiency.- - - - - - - - - - ranking = 122.75028836508keywords = cramp, muscle (Clic here for more details about this article) |
17/24. Fetal akinesia sequence caused by glycogenosis type VII.We report on the autopsy study of a premature boy with multiple joint contractures who died soon after birth of severe lung hypoplasia. Muscle histology showed PAS-positive vacuoles, and electronmicroscopy revealed massive subsarcolemmal and intermyofibrillar accumulation of glycogen. Biochemical analysis of fresh-frozen muscle tissue disclosed increased glycogen content and a complete lack of phosphofructokinase (PFK) activity. The brain showed focal cerebral and diffuse cerebellar white matter gliosis, and patchy loss of internal granular and purkinje cells in the cerebellar cortex. The spinal cord was normal. This report describes the first case of PFK deficiency, presenting as a lethal fetal akinesia sequence.- - - - - - - - - - ranking = 0.5keywords = muscle (Clic here for more details about this article) |
18/24. A 5' splice junction mutation leading to exon deletion in an Ashkenazic Jewish family with phosphofructokinase deficiency (Tarui disease).A deficiency of the muscle isoform of the enzyme, phosphofructokinase (PFK, EC 2.7.1.11), leads to an illness (glycogenosis, Type VII) characterized by myopathy and hemolysis. A patient with this disease and an affected sister were found to have a G to A substitution at the 5' donor site of intron 5 of the PFK-M gene. This mutation led to a splicing defect: a complete deletion of the preceding exon in the patient's mRNA. The patient, an affected sister, and related and unrelated family members, who were of Ashkenazic Jewish background, were screened for the mutation by denaturing gradient gel electrophoresis and by allele specific hybridization of genomic dna. The affected sisters are homozygous for the mutation, and their children, who are unaffected, are heterozygous. The only previously characterized genetic defect in this disease, found in a Japanese patient, was a G to T mutation at the beginning of intron 15 with splicing to a cryptic site within exon 15 (1). Both mutations lead to inframe deletions, but of different parts of the protein. The differences between the two aberrant proteins may account for clinical differences between our patients and the Japanese patient.- - - - - - - - - - ranking = 0.5keywords = muscle (Clic here for more details about this article) |
19/24. Late-onset muscle weakness in partial phosphofructokinase deficiency: a unique myopathy with vacuoles, abnormal mitochondria, and absence of the common exon 5/intron 5 junction point mutation.Three patients (ages 51, 59, and 79) from two generations of an Ashkenazi Jewish family had partial (33% activity) phosphofructokinase (PFK) deficiency that presented with fixed muscle weakness after the age of 50 years. MR spectroscopy revealed accumulation of phosphomonoesters during exercise. Muscle biopsy showed a vacuolar myopathy with increased autophagic activity and several ragged-red and cytochrome c oxidase-negative fibers. The older patient, age 79 at biopsy, had several necrotic fibers. Electron microscopy revealed subsarcolemmal and intermyofibrillar glycogen accumulation and proliferation of mitochondria with paracrystalline inclusions, probably related to reduced availability of energy due to impaired glycolysis. The common point mutation of exon 5/intron 5 junction seen in Jewish Ashkenazi patients with PFK deficiency was excluded. We conclude that late-onset fixed muscle weakness occurs in partial PFK deficiency and it may represent the end result of continuing episodes of muscle fiber destruction. Partial enzyme deficiency in two successive generations suggests a unique molecular mechanism.- - - - - - - - - - ranking = 3.5keywords = muscle (Clic here for more details about this article) |
20/24. Glycogenosis type VII (Tarui disease) in a Swedish family: two novel mutations in muscle phosphofructokinase gene (PFK-M) resulting in intron retentions.Phosphofructokinase (PFK) plays a major role in glycolysis. Human PFK is composed of three isoenzyme subunits (muscle [Ml, liver [L], and platelet [P]), which are encoded by different genes. Deficiency of muscle isoenzyme (PFK-M), glycogenosis type VII (Tarui disease), is an autosomal recessive disorder characterized by an exertional myopathy and hemolytic syndrome. Several disease-causing mutations have been identified in the PFK-M gene in Japanese, Ashkenazi Jewish, Italian, French Canadian, and Swiss patients. We describe the genetic defect in a Swedish family with affected individuals in two generations. The patients are compound heterozygotes: two different mutations result in retention of intron 13 or intron 16 sequences into mRNA. A G1127A transition destroys the 5' donor site of intron 13, resulting in a 155-nt retention of the intronic sequence. An a-to-g base change in intron 16 creates a new acceptor splice site, resulting in a 63-nt retention of intronic sequence. Both mutations are predicted to result in premature termination of translation. Some of the transcripts generated from the intron 16 mutated allele also contain intron 10 sequence unspliced.- - - - - - - - - - ranking = 3keywords = muscle (Clic here for more details about this article) |
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