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Salvatore DiMauro

Publications and source records attributed to Salvatore DiMauro.

At least 19 recordsLinked to original sources
PubMed2006

Human coenzyme Q10 deficiency.

Ubiquinone (coenzyme Q(10) or CoQ(10)) is a lipid-soluble component of virtually all cell membranes and has multiple metabolic functions. Deficiency of CoQ(10) (MIM 607426) has been associated with five different clinical presentations that suggest genetic heterogeneity, which may be related to the multiple steps in CoQ(10) biosynthesis. Patients with all forms of CoQ(10) deficiency have shown clinical improvements after initiating oral CoQ(10) supplementation. Thus, early diagnosis is of critical importance in the management of these patients. This year, the first molecular defect causing the infantile form of primary human CoQ(10) deficiency has been reported. The availability of genetic testing will allow for a better understanding of the pathogenesis of this disease and early initiation of therapy (even presymptomatically in siblings of patients) in this otherwise life-threatening infantile encephalomyopathy.

Brain Diseases, Metabolic, Inborn↗
PubMed2006

Mitochondrial DNA deletions inhibit proteasomal activity and stimulate an autophagic transcript.

Deletions within the mitochondrial DNA (mtDNA) cause Kearns Sayre syndrome (KSS) and chronic progressive external opthalmoplegia (CPEO). The clinical signs of KSS include muscle weakness, heart block, pigmentary retinopathy, ataxia, deafness, short stature, and dementia. The identical deletions occur and rise exponentially as humans age, particularly in substantia nigra. Deletions at >30% concentration cause deficits in basic bioenergetic parameters, including membrane potential and ATP synthesis, but it is poorly understood how these alterations cause the pathologies observed in patients. To better understand the consequences of mtDNA deletions, we microarrayed six cell types containing mtDNA deletions from KSS and CPEO patients. There was a prominent inhibition of transcripts encoding ubiquitin-mediated proteasome activity, and a prominent induction of transcripts involved in the AMP kinase pathway, macroautophagy, and amino acid degradation. In mutant cells, we confirmed a decrease in proteasome biochemical activity, significantly lower concentration of several amino acids, and induction of an autophagic transcript. An interpretation consistent with the data is that mtDNA deletions increase protein damage, inhibit the ubiquitin-proteasome system, decrease amino acid salvage, and activate autophagy. This provides a novel pathophysiological mechanism for these diseases, and suggests potential therapeutic strategies.

Autophagy↗
PubMed2006

Navajo neurohepatopathy is caused by a mutation in the MPV17 gene.

Navajo neurohepatopathy (NNH) is an autosomal recessive disease that is prevalent among Navajo children in the southwestern United States. The major clinical features are hepatopathy, peripheral neuropathy, corneal anesthesia and scarring, acral mutilation, cerebral leukoencephalopathy, failure to thrive, and recurrent metabolic acidosis with intercurrent infections. Infantile, childhood, and classic forms of NNH have been described. Mitochondrial DNA (mtDNA) depletion was detected in the livers of two patients, suggesting a primary defect in mtDNA maintenance. Homozygosity mapping of two families with NNH suggested linkage to chromosome 2p24. This locus includes the MPV17 gene, which, when mutated, causes a hepatocerebral form of mtDNA depletion. Sequencing of the MPV17 gene in six patients with NNH from five families revealed the homozygous R50Q mutation described elsewhere. Identification of a single missense mutation in patients with NNH confirms that the disease is probably due to a founder effect and extends the phenotypic spectrum associated with MPV17 mutations.

Adult↗
PubMed2006

MPV17 encodes an inner mitochondrial membrane protein and is mutated in infantile hepatic mitochondrial DNA depletion.

The mitochondrial (mt) DNA depletion syndromes (MDDS) are genetic disorders characterized by a severe, tissue-specific decrease of mtDNA copy number, leading to organ failure. There are two main clinical presentations: myopathic (OMIM 609560) and hepatocerebral (OMIM 251880). Known mutant genes, including TK2, SUCLA2, DGUOK and POLG, account for only a fraction of MDDS cases. We found a new locus for hepatocerebral MDDS on chromosome 2p21-23 and prioritized the genes on this locus using a new integrative genomics strategy. One of the top-scoring candidates was the human ortholog of the mouse kidney disease gene Mpv17. We found disease-segregating mutations in three families with hepatocerebral MDDS and demonstrated that, contrary to the alleged peroxisomal localization of the MPV17 gene product, MPV17 is a mitochondrial inner membrane protein, and its absence or malfunction causes oxidative phosphorylation (OXPHOS) failure and mtDNA depletion, not only in affected individuals but also in Mpv17-/- mice.

Amino Acid Sequence↗
PubMed2006

Aortic rupture in mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes.

BACKGROUND: Microangiopathy has been well described in the brain and muscle of patients with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). OBJECTIVE: To describe a patient with the common A3243G/MELAS point mutation who had aortic rupture and whose mother also died of large vessel rupture. DESIGN: Case report. SETTING: Collaboration between a primary care hospital and 2 academic tertiary care hospitals. RESULTS: Histologically, there was marked disarray of the smooth muscle architecture of the aorta, and immunohistochemical staining with antibodies against the mitochondrial DNA-encoded cytochrome-C oxidase I subunit showed uniformly decreased immunostaining of the endothelial and smooth muscle cells of the aorta and vasa vasorum. Polymerase chain reaction and restriction fragment length polymorphism analysis showed that the mutation load was 40.5% in blood but 85.3% in the blood vessels. CONCLUSIONS: The severe vasculopathy in this patient is probably directly related to the high mutation load in the blood vessels. Although aortic rupture is an unusual manifestation of MELAS, it is an important potential complication in patients undergoing minor surgical procedures.

Adolescent↗
PubMed2006

Nerve conduction abnormalities in patients with MELAS and the A3243G mutation.

BACKGROUND: Mitochondrial DNA point mutations are especially deleterious to tissues with high energy demand, including the peripheral nervous system. Neuropathy has been associated with several mitochondrial diseases, including MELAS (mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes). OBJECTIVE: To evaluate nerve conduction in a genotypically and phenotypically homogeneous group of patients with MELAS and the A3243G mutation. DESIGN: We studied 30 patients with MELAS and the A3243G mutation using neurophysiological techniques, medical history questionnaires, laboratory tests, and a standardized neurological examination. RESULTS: Twenty-three subjects (77%) had abnormal nerve conduction measures. Symptoms suggestive of neuropathy were present in only half of the patients, but almost all had decreased reflexes or distal sensory findings on examination. Nerve conduction abnormalities were predominantly axonal and sensory and mainly present in the legs. Patients with nerve conduction abnormalities tended to be older and were more likely male. CONCLUSIONS: Peripheral nerve impairment is common in those with MELAS and the A3243G mutation, and may be subclinical. Male sex and older age may add to the genetic disposition to develop neuropathy.

Adult↗
PubMed2006

Clinical spectrum of mitochondrial DNA depletion due to mutations in the thymidine kinase 2 gene.

BACKGROUND: Mitochondrial DNA depletion syndrome is an autosomal recessive disorder characterized by decreased mitochondrial DNA copy numbers in affected tissues. It has been linked to 4 genes involved in deoxyribonucleotide triphosphate metabolism: thymidine kinase 2 (TK2), deoxyguanosine kinase (DGUOK), polymerase gamma (POLG), and SUCLA2, the gene encoding the beta-subunit of the adenosine diphosphate-forming succinyl coenzyme A synthetase ligase. OBJECTIVE: To highlight the variability in the clinical spectrum of TK2-related mitochondrial DNA depletion syndrome. DESIGN: Review of patients and the literature. SETTING: Tertiary care university. PATIENTS: Four patients with mitochondrial DNA depletion syndrome and mutations in the TK2 gene. MAIN OUTCOME MEASURES: Definition of clinical variability. RESULTS: Patient 1 had evidence of lower motoneuron disease and was initially diagnosed as having spinal muscular atrophy type 3. Patient 2, who is alive and ambulatory at age 9 years, presented at age 2 years with a slowly progressive mitochondrial myopathy. Patient 3 had a more severe myopathy, with onset in infancy and death at age 6 years of respiratory failure. Patient 4 had a rapidly progressive congenital myopathy with rigid spine syndrome and he died at age 19 months. CONCLUSION: The clinical spectrum of TK2 mutations is not limited to severe infantile myopathy with motor regression and early death but includes spinal muscular atrophy type 3-like presentation, rigid spine syndrome, and subacute myopathy without motor regression and with longer survival.

Adolescent↗
PubMed2006

Early-onset familial parkinsonism due to POLG mutations.

OBJECTIVE: To define the molecular etiology of early-onset parkinsonism and peripheral neuropathy. METHODS: Two sisters had early-onset parkinsonism (dystonic toe curling, action tremor, masked face, bradykinesia, stooped posture, and rigidity), together with clinical and electrophysiological signs of sensorimotor axonal peripheral neuropathy. RESULTS: No mutations were found in the genes for parkin or PINK1. Muscle biopsies showed ragged-red and cytochrome c oxidase-negative fibers, and biochemistry showed decreased activities of respiratory chain complexes containing mitochondrial DNA-encoded subunits. Multiple mitochondrial DNA deletions were seen by long polymerase chain reaction, and sequencing of the POLG gene showed that the patients were compound heterozygous for two patogenic mutations. INTERPRETATION: POLG mutations can cause early-onset parkinsonism in the absence of progressive external ophthalmoplegia.

Adult↗
PubMed2006

Benign course of glycogen storage disease type IIb in two brothers: nature or nurture?

Two brothers with the childhood variant of type II glycogenosis (GSD-IIb) treated with nutrition and exercise therapy (NET) from a young age showed an unusually benign course. Muscle biopsy from the older brother, which showed characteristic vacuolar glycogen accumulation at age 2, had reverted to normal by age 16. A muscle biopsy from the younger brother was normal at 5 years. It is uncertain whether this anomalous evolution was spontaneous (nature) or due to the symptomatic therapy (nurture), but NET should be considered in patients with GSD-IIb until enzyme replacement or gene therapy become generally available.

DNA↗
PubMed2006

Approaches to the treatment of mitochondrial diseases.

Therapy for mitochondrial diseases is woefully inadequate. However, lack of a cure does not equate with lack of treatment. Palliative therapy is dictated by good medical practice and includes anticonvulsant medication, control of endocrine dysfunction, and surgical procedures. Removal of noxious metabolites is centered on combating lactic acidosis, but extends to other metabolites. Attempts to bypass blocks in the respiratory chain by administration of electron acceptors have not been successful, but this may be amenable to genetic engineering. Administration of metabolites and cofactors is the mainstay of real-life therapy and is especially important in disorders due to primary deficiencies of specific compounds, such as carnitine or coenzyme Q10 (CoQ10). There is increasing interest in the administration of reactive oxygen radicals (ROS) scavengers, both in primary mitochondrial diseases and in neurodegenerative diseases. Gene therapy is a challenge because of polyplasmy and heteroplasmy, but novel experimental approaches are being pursued. One important strategy is to decrease the ratio of mutant to wild-type mitochondrial genomes ("gene shifting") by different means: (1) converting mutated mitochondrial DNA (mtDNA) genes into normal nuclear DNA genes ("allotopic expression"); (2) importing cognate genes from other species ("xenotopic expression"); (3) correcting mtDNA mutations by importing specific restriction endonucleases; (4) selecting for respiratory function; and (5) inducing muscle regeneration. Germline therapy raises ethical problems but is being considered for prevention of maternal transmission of mtDNA mutations. Preventive therapy through genetic counseling and prenatal diagnosis is becoming increasingly important for nuclear DNA-related disorders.

Acidosis, Lactic↗
PubMed2006

Exercise-induced cramp, myoglobinuria, and tubular aggregates in phosphoglycerate mutase deficiency.

We report two patients in whom phosphoglycerate mutase (PGAM) deficiency was associated with the triad of exercise-induced cramps, recurrent myoglobinuria, and tubular aggregates in the muscle biopsy. Serum creatine kinase (CK) levels were elevated between attacks of myoglobinuria. Forearm ischemic exercise tests produced subnormal increases of venous lactate. Muscle biopsies showed subsarcolemmal tubular aggregates in type 2 fibers. Muscle PGAM activities were markedly decreased (3% of the normal mean) and molecular genetic studies showed that both patients were homozygous for a described missense mutation (W78X). A review of 15 cases with tubular aggregates in the muscle biopsies from our laboratory and 15 cases with PGAM deficiency described in the literature showed that this clinicopathological triad is highly suggestive of PGAM deficiency.

Adolescent↗
PubMed2006

Mitochondrial myopathies.

PURPOSE OF REVIEW: Our understanding of mitochondrial diseases (defined restrictively as defects of the mitochondrial respiratory chain) is expanding rapidly. In this review, I will give the latest information on disorders affecting predominantly or exclusively skeletal muscle. RECENT FINDINGS: The most recently described mitochondrial myopathies are due to defects in nuclear DNA, including coenzyme Q10 deficiency and mutations in genes controlling mitochondrial DNA abundance and structure, such as POLG, TK2, and MPV17. Barth syndrome, an X-linked recessive mitochondrial myopathy/cardiopathy, is associated with decreased amount and altered structure of cardiolipin, the main phospholipid of the inner mitochondrial membrane, but a secondary impairment of respiratory chain function is plausible. The role of mutations in protein-coding genes of mitochondrial DNA in causing isolated myopathies has been confirmed. Mutations in tRNA genes of mitochondrial DNA can also cause predominantly myopathic syndromes and--contrary to conventional wisdom--these mutations can be homoplasmic. SUMMARY: Defects in the mitochondrial respiratory chain impair energy production and almost invariably involve skeletal muscle, causing exercise intolerance, cramps, recurrent myoglobinuria, or fixed weakness, which often affects extraocular muscles and results in droopy eyelids (ptosis) and progressive external ophthalmoplegia.

Cell Nucleus↗
PubMed2005

hCOX18 and hCOX19: two human genes involved in cytochrome c oxidase assembly.

We identified the human homologues of yCOX18 and yCOX19, two Saccharomyces cerevisiae genes involved in the biogenesis of mitochondrial respiratory chain complexes. In yeast, these two genes are required for the expression of cytochrome c oxidase: Cox18p catalyses the insertion of Cox2p COOH-tail into the mitochondrial inner membrane, and Cox19p is probably involved in metal transport to the intermembrane space. Both hCox18p and hCox19p present significant amino acid identity with the corresponding yeast polypeptides and reveal highly conserved functional domains. In addition, their subcellular localization is analogous to that of the yeast proteins. These data strongly suggest that the human gene products share similar functions with their yeast homologues. These two COX-assembly genes represent new candidates for mutational analysis in patients with isolated COX deficiency of unknown etiology.

Amino Acid Sequence↗
PubMed2005

Congenital or late-onset myopathy in patients with the T14709C mtDNA mutation.

Three patients with different clinical phenotypes harbored the same point mutation at nucleotide 14709 (T14709C) in the tRNAGlu gene of mitochondrial DNA (mtDNA). The first patient was a 21-month-old child with severe congenital myopathy, respiratory distress and mild mental retardation. Muscle biopsy showed about 12% cytochrome c oxidase (COX)-negative ragged-red fibers (RRFs), and markedly decreased activities of mitochondrial respiratory chain complexes I, III and IV. The other two patients were 51- and 55-year-old siblings with slowly progressive myopathy and diabetes mellitus. Muscle biopsy showed focal COX-negative RRFs and decreased activities of complexes I, III and IV. In all three patients, the T14709C mutation was abundant in muscle but present at lower levels in accessible tissues. Previously described patients with the same mutation also showed congenital or late-onset myopathy. Diabetes is frequently associated with both phenotypes and is a clinical clue to the molecular diagnosis.

Cysteine↗
PubMed2005

Muscle coenzyme Q10 level in statin-related myopathy.

BACKGROUND: Statin drugs (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) reduce the level of cholesterol by inhibiting the synthesis of mevalonate, an intermediary in the cholesterol biosynthetic pathway. Use of statin drugs has been associated with a variety of skeletal muscle-related complaints. Coenzyme Q10 (CoQ10), a component of the mitochondrial respiratory chain, is also synthesized from mevalonate, and decreased muscle CoQ10 concentration may have a role in the pathogenesis of statin drug-related myopathy. OBJECTIVES: To measure the CoQ10 concentration and respiratory chain enzyme activities in muscle biopsy specimens from 18 patients with statin drug-related myopathy and to look for evidence of apoptosis using the TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling) assay. DESIGN: An open-labeled study of CoQ10 concentration in muscle from patients with increased serum creatine kinase concentrations while receiving standard statin drug therapy. SETTING: Neuromuscular centers at 2 academic tertiary care hospitals. RESULTS: Muscle structure was essentially normal in 14 patients and showed evidence of mitochondrial dysfunction and nonspecific myopathic changes in 2 patients each. Muscle CoQ10 concentration was not statistically different between patients and control subjects, but it was more than 2 SDs below the normal mean in 3 patients and more than 1 SD below normal in 7 patients. There was no TUNEL positivity in any patients. CONCLUSION: These data suggest that statin drug-related myopathy is associated with a mild decrease in muscle CoQ10 concentration, which does not cause histochemical or biochemical evidence of mitochondrial myopathy or morphologic evidence of apoptosis in most patients.

Adult↗
PubMed2005

Novel mitochondrial DNA ND5 mutation in a patient with clinical features of MELAS and MERRF.

BACKGROUND: The mitochondrial DNA gene encoding subunit 5 of complex I (ND5) has turned out to be a hot spot for mutations associated with mitochondrial encephalomyopathy with lactic acidosis and strokelike episodes (MELAS) and various overlap syndromes. OBJECTIVE: To describe a novel mutation in the ND5 gene in a young man man with an overlap syndrome of MELAS and myoclonus epilepsy with ragged-red fibers. DESIGN: Case report. PATIENT: A 25-year-old man had recurrent strokes, seizures, and myoclonus. His mother also had multiple strokes. A muscle biopsy specimen showed no ragged-red fibers but several strongly succinate dehydrogenase-reactive blood vessels. RESULTS: Biochemical analysis showed isolated complex I deficiency and molecular analysis revealed a novel heteroplasmic mutation (G13042A) in the ND5 gene. CONCLUSIONS: These data confirm that ND5 is a genetic hot spot for overlap syndromes, including MELAS and strokelike and myoclonus epilepsy with ragged-red fibers.

Adult↗