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Biomedical subjects

M Zeviani

Publications and source records attributed to M Zeviani.

At least 145 records · Page 8Linked to original sources
PubMed1988

Subunit Va of human and bovine cytochrome c oxidase is highly conserved.

We have isolated a full-length cDNA clone specifying the nuclear-encoded subunit Va of the human mitochondrial respiratory enzyme cytochrome c oxidase (COX; EC 1.9.3.1.). The deduced sequence of the polypeptide is 95% identical to that of the corresponding subunit of bovine COX, which makes it the most conserved polypeptide among the known bovine/human pairs of COX subunits. This polypeptide contains an N-terminal presequence which is rich in basic and hydroxylated residues, but differs from the deduced presequences of all other previously isolated COX subunits in that it also contains a negatively charged residue. We find no evidence of tissue-specific isoforms of subunit Va, as Northern analysis showed a single, identically-sized transcript in RNA from human muscle, liver, and brain, while coxVa cDNAs isolated from both endothelial and fetal muscle cDNA libraries had identical nucleotide sequences.

Amino Acid Sequence↗
PubMed1988

Sequence of cDNAs encoding subunit Vb of human and bovine cytochrome c oxidase.

We have isolated a full-length human fetal muscle cDNA clone specifying the nuclear-encoded subunit Vb of the human mitochondrial respiratory chain enzyme, cytochrome c oxidase (COX; EC 1.9.3.1), and a partial-length brain cDNA clone specifying the analogous bovine subunit. The two cDNAs are 85% identical at the nucleotide level. Similar to other proteins imported into mitochondria, the deduced human COX Vb protein contains a presequence, 31 amino acids long, rich in basic residues. We find no evidence for tissue-specific transcripts for subunit Vb of human COX, as Northern analysis of total RNA from human muscle, liver, and brain showed a single, identically sized transcript in each cell type, while partial-length cDNA clones isolated from human muscle and endothelial cell cDNA libraries were identical in sequence to the fetal muscle cDNA.

Amino Acid Sequence↗
PubMed1988

McArdle's disease: biochemical and molecular genetic studies.

We have analyzed muscle biopsy specimens from 48 patients with biochemically proven phosphorylase deficiency (McArdle's disease) by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, and immunotitration (enzyme-linked immunosorbent assay [ELISA]). Thirty-five of the 42 patients studied by SDS-PAGE and immunoblot, and 41 of the 48 patients studied by ELISA had no detectable enzyme protein. Six patients had markedly decreased phosphorylase protein by all three assays, and only 1 patient had a normal amount of protein. No apparent correlation existed between the presence or absence of enzyme protein and the clinical presentation or muscle glycogen concentration. Northern analysis was performed on muscle RNA in 4 patients: messenger RNA was normal in 2, abnormally short in 1, and absent in the fourth, indicating heterogeneity of the molecular lesion in McArdle's disease.

Biopsy↗
PubMed1988

Molecular defects in cytochrome oxidase in mitochondrial diseases.

Defects of cytochrome c oxidase (COX) show remarkable clinical, biochemical, and genetic heterogeneity. Clinically, there are two main groups of disorders, one dominated by muscle involvement, the other by brain dysfunction. Biochemically, the enzyme defect may be confined to one or a few tissues (reflecting the existence of tissue-specific isozymes) or affect all tissues. Immunologically reactive enzyme protein is decreased in some forms of COX deficiency but not in others. Because COX is encoded both by nuclear and by mitochondrial genes, COX deficiencies may be due to mutations of either genome and may offer useful models to study the communication between nuclei and mitochondria. We have isolated full-length cDNA clones encoding human COX subunits IV, Vb, and VIII and a partial-length clone for subunit Va. These clones are being used as probes to analyze the DNA and RNA of patients with COX deficiency.

Brain Diseases↗
PubMed1988

Cloning and expression of human nebulin cDNAs and assignment of the gene to chromosome 2q31-q32.

We have isolated two nonoverlapping cDNAs encoding human nebulin, a muscle-specific protein. Northern hybridization analysis shows that nebulin is encoded by a huge message at least 25 kb in length. By hybridizing two nonoverlapping cDNAs to DNA isolated from rodent X human cell hybrids, we assign this presumably single-copy gene to human chromosome 2; sublocalization studies indicate that the nebulin gene is on the long arm of the chromosome, in the region 2q31-q32.

Amino Acid Sequence↗
PubMed1988

Immunocytochemical study of nebulin in Duchenne muscular dystrophy.

We used antibodies to nebulin in immunocytochemical studies. In normal muscle, nebulin was localized at the I band. The protein was also present in most fibers from all 15 Duchenne muscular dystrophy (DMD) patients studied, including patients who seemed to lack nebulin in electrophoretic gels and patients who demonstrated deletions of DNA in the region of Xp21. These results conform to other evidence that nebulin is not the primarily affected gene product in DMD; it may be affected secondarily.

Child↗
PubMed1988

MELAS syndrome: characteristic migrainous and epileptic features and maternal transmission.

Severe prolonged migrainous symptoms and prolonged partial status epilepticus are characteristic features of the MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes). Maternal transmission previously found in myoclonus epilepsy and ragged-red fibers (MERRF), another mitochondrial disease, is suggested in this disorder as well.

Adolescent↗
PubMed1988

Deletions of mitochondrial DNA in Kearns-Sayre syndrome.

We have identified large-scale deletions in muscle mitochondrial DNA (mtDNA) in seven of seven patients with Kearns-Sayre syndrome (KSS). We found no detectable deletions in the mtDNA of ten non-KSS patients with other mitochondrial myopathies or encephalomyopathies, or three normal controls. The deletions ranged in size from 2.0 to 7.0 kb, and did not localize to any single region of the mitochondrial genome. The proportion of mutated genomes in each KSS patient ranged from 45% to 75% of total mtDNA. There was no correlation between the size or site of the deletion, biochemical abnormality of mitochondrial enzymes, or clinical severity. The data bolster arguments that KSS is a unique disorder and genetic in origin.

Adolescent↗
PubMed1987

Cytochrome c oxidase deficiency in Leigh syndrome.

We studied 6 mitochondrial enzymes in crude extracts and isolated mitochondria from 5 children with pathologically proven subacute necrotizing encephalomyelopathy (Leigh syndrome). Samples were taken from brain (5 patients), skeletal muscle (4 patients), liver (4 patients), kidney (4 patients), heart (1 patient), and cultured fibroblasts (3 patients). An isolated defect of cytochrome c oxidase (COX) activity was found in brain (decrease of activity to 15 to 39% of the normal mean), muscle (9 to 20%), kidney (1 to 67%), and in the 1 available heart (4%) from a patient with cardiopathy. COX activity was also decreased in liver of 3 patients (2 to 13% of normal) and in cultured fibroblasts of 2 patients (18 and 27%), but it was normal in both liver and fibroblasts from 1 patient. Immunotitration using polyclonal antibodies against human heart COX showed essentially normal amounts of cross-reacting enzyme protein in various tissues from different patients. Electrophoresis of COX immunoprecipitated from brain mitochondrial extracts showed normal patterns of COX subunits in 2 patients. This study confirms the theory that COX deficiency is an important cause of Leigh syndrome.

Brain↗
PubMed1987

Mitochondrial myopathies.

The mitochondrial myopathies or encephalomyopathies with known biochemical defects can be divided into 5 groups: (1) defects of mitochondrial transport, such as CPT deficiency or carnitine deficiencies; (2) defects of substrate utilization, such as PDHC deficiency or defects of beta-oxidation; (3) defects of the Krebs cycle, such as fumarase deficiency; (4) defects of oxidation-phosphorylation coupling, such as Luft disease, and (5) defects of the respiratory chain. These disorders are reviewed, with particular emphasis on the defects of the respiratory chain. Defects of complex I, III and IV show remarkable clinical and biochemical heterogeneity. All 3 complexes contain some subunits encoded by mtDNA and others encoded by nuclear DNA. At least some of the cytoplasmically made subunits appear to be tissue specific and may be developmentally regulated, thus explaining the genetic heterogeneity of these disorders.

Adenosine Triphosphatases↗
PubMed1987

Isolation of a cDNA clone encoding subunit IV of human cytochrome c oxidase.

We have isolated a full-length human liver cDNA clone specifying the nuclear-encoded subunit IV of the human mitochondrial respiratory chain enzyme, cytochrome c oxidase (COX; EC 1.9.3.1). The human cDNA clone is highly homologous to its bovine counterpart in the coding regions for both the mature polypeptide and the presequence, and the gene is evolving more slowly than that of any of the three mitochondrially encoded COX subunit genes. We find no preliminary evidence for tissue-specific isoforms of COX subunit IV, as Northern analysis of muscle, liver, and HeLa cell RNA shows an identically sized transcript in each cell type.

Amino Acid Sequence↗
PubMed1987

Mitochondrial encephalomyopathy and partial cytochrome c oxidase deficiency.

A 52-year-old man had slowly progressive weakness and wasting of limb-muscles, sensorineural hearing loss, and complex partial seizures. CT showed cerebral atrophy, but he was not demented. Muscle biopsy showed ragged-red fibers and decreased histochemical stain for cytochrome c oxidase. Biochemical studies showed decreased cytochrome c oxidase activity in crude muscle extracts and in isolated mitochondria (44 and 30% of normal), while other mitochondrial enzymes were normal. A comparable decrease of immunologically reactive enzyme protein was shown by immunotitration with antibodies against human heart cytochrome c oxidase. Partial defects of cytochrome c oxidase may cause adult-onset, slowly progressive mitochondrial encephalomyopathies.

Atrophy↗
PubMed1987

Benign reversible muscle cytochrome c oxidase deficiency: a second case.

A 6-week-old boy had generalized weakness, requiring assisted ventilation, and lactic acidosis. At 6 months, the lactic acidosis resolved, and the patient started to improve; assisted ventilation was discontinued at 15 months. Muscle biopsies at 4 and 11 months showed accumulation of mitochondria, lipid, and glycogen; cytochrome c oxidase (COX) activity was 11% of the lowest control in the first biopsy and 57% in the second. Immunocytochemistry and immunotitration showed presence of immunologically reactive enzyme protein in both biopsies. This case confirms a previous report of benign infantile myopathy due to reversible COX deficiency. The severe fibrosis in the second biopsy may explain the slower rate of clinical recovery in this child.

Biopsy↗
PubMed1986

Myopathy and fatal cardiopathy due to cytochrome c oxidase deficiency.

A 3-day-old girl had a syndrome of lethargy and lactic acidosis. Pregnancy and delivery had been normal; there was no consanguinity or family history of neuromuscular disease. At age 4 1/2 months, she had generalized weakness, hypotonia, areflexia, and macroglossia. She developed cyanosis and respiratory failure, and marked cardiomegaly was noted. She died at age 8 1/2 months of cardiac arrest. Results from a muscle biopsy specimen obtained at age 4 1/2 months showed ragged-red fibers and increased glycogen and lipid droplets. With the cytochrome c oxidase reaction, only 5% of the fibers stained positively in the biopsy specimen. Cytochrome c oxidase activity was 7.3% of normal in muscle mitochondria and 12.2% of normal in heart mitochondria. Reduced-minus-oxidized cytochrome spectra showed lack of the cytochrome aa3 peak. Immunotitration using antibodies against purified human heart cytochrome c oxidase showed normal amount of cross-reacting material in both heart and muscle. The genetic error could have involved a cytochrome c oxidase isozyme common to heart and muscle.

Cytochrome-c Oxidase Deficiency↗