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S DiMauro

Publications and source records attributed to S DiMauro.

At least 181 records · Page 10Linked to original sources
PubMed1995

Segregation patterns of a novel mutation in the mitochondrial tRNA glutamic acid gene associated with myopathy and diabetes mellitus.

We have identified a novel mtDNA mutation in a 29-year-old man with myopathy and diabetes mellitus. This T-->C transition at mtDNA position 14709 alters an evolutionarily conserved nucleotide in the region specifying for the anticodon loop of the mitochondrial tRNA(Glu). The nt-14709 mutation was heteroplasmic but present at very high levels in the patient's muscle, white blood cells (WBCs), and hair follicles; lower proportions of mutated mtDNA were observed in WBCs and hair follicles of all examined maternal relatives. In the patient's muscle, abnormal fibers showed mitochondrial proliferation, severe focal defects in cytochrome c oxidase activity, and absence of cross-reacting material for mitochondrially synthesized polypeptides. These fibers had higher levels of mutated mtDNA than did surrounding "normal" fibers. Although the percentage of mutated mtDNA in WBCs from family members were distributed around the percentage observed in the mothers, the pattern was different in hair follicles, where the mutated population tended to increase in subsequent generations. PCR/RFLP analysis of single hairs showed that the intercellular variations in the percentage of mutated mtDNA differed among family members, with younger generations having a more homogeneous distribution of mutated mtDNA in different hair follicles. These results suggest that the intercellular distribution of the mutated and wild-type mtDNA populations may drift toward homogeneity in subsequent generations.

Adult↗
PubMed1994

Dementia of adult polyglucosan body disease. Evidence of cortical and subcortical dysfunction.

OBJECTIVES: To characterize the dementia associated with adult polyglucosan body disease (APBD) and to correlate the cognitive deficits with abnormalities found on magnetic resonance imaging (MRI). METHODS: Quantitative neuropsychological testing and MRI in one man with APBD and a review of the literature. RESULTS: The dementia of APBD affects cortical and subcortical functions. The cognitive deficits correlate with MRI findings of cortical atrophy and white-matter abnormalities. CONCLUSION: Neuropsychological testing and MRI are helpful in the evaluation of patients with APBD.

Brain Diseases↗
PubMed1994

A splice junction mutation in a new myopathic variant of phosphoglycerate kinase deficiency (PGK North Carolina).

We report on a 12-year-old boy with the myopathic form of phosphoglycerate kinase (PGK) deficiency, and unique kinetic and physical characteristics of the mutant enzyme (PGK North Carolina). A G-to-T substitution at the 5' end of intron 4 was identified in the PGK gene of this patient. The mutation destroys the consensus sequence GT at the 5' splice junction of the intron. Activation of a cryptic splice site within intron 4 causes the insertion into the transcript of a 30-bp fragment at the 5' end of intron 4. This insertion results in ten additional amino acids within the "nose" of the PGK molecule, but does not generate a frameshift or a premature stop codon.

Base Sequence↗
PubMed1994

Molecular genetic studies of muscle lactate dehydrogenase deficiency in white patients.

We identified two new mutations in 2 white patients with muscle lactate dehydrogenase deficiency. Both patients had exercise intolerance, cramps, and recurrent myoglobinuria. One patient was homozygous for a 2-bp deletion in exon 5, resulting in a frameshift with premature termination of translation. The second patient was homozygous for a G-->A substitution at the 3' end of exon 2, leading to exon skipping and splicing of exon 1 to exon 3; the aberrantly spliced messenger RNA contains a frameshift, resulting in premature termination of translation. The present report provides evidence of molecular genetic heterogeneity in white patients with muscle lactate dehydrogenase deficiency.

Adult↗
PubMed1994

A new mtDNA mutation in the tRNA(Leu(UUR)) gene associated with maternally inherited cardiomyopathy.

We report a new mutation, a C to T transition at nt 3303 of mtDNA, in seven members of a family with cardiomyopathy and myopathy: the proband and two siblings had fatal infantile cardiomyopathy, whereas in three maternal relatives the disease manifested later in life as sudden cardiac death or as mitochondrial myopathy with cardiomyopathy. The mutation was homoplasmic in all tissues (including blood) from the proband and her brother, but heteroplasmic in blood from five oligosymptomatic or asymptomatic maternal relatives. This mutation disrupts a conserved base pair in the aminoacyl stem of the tRNA(Leu(UUR)). None of 70 controls carried the mutation. Our data indicate that this mutation is the genetic cause of the disorder in this family, and confirm that the tRNA(Leu(UUR)) is a "hot spot" for mutations in mtDNA.

Adolescent↗
PubMed1994

Skeletal muscle mitochondrial myopathy as a cause of exercise intolerance in a horse.

Although exertional myopathies are commonly recognized in horses, specific etiologies have not been identified. This is the first report in the horse of a deficiency of Complex I respiratory chain enzyme associated with profound exercise intolerance. Physical examination, routine blood tests, endoscopy, and ultrasonograms of the heart and iliac arteries were unremarkable. With slow, incremental exercise (speeds 1.5-7 m/s), the Arabian mare showed a marked lactic acidosis, increased mixed venous PVO2, and little change in oxygen consumption. Muscle biopsies contained large accumulations of mitochondria with bizarre cristae formations. Biochemical analyses revealed a very low activity of the first enzyme complex in the mitochondrial respiratory chain (NADH CoQ reductase). The exercise intolerance and muscle stiffness in this horse were attributed to a profound lactic acidosis resulting from impaired oxidative energy metabolism during exercise.

Acidosis, Lactic↗
PubMed1994

Ekbom's syndrome: lipomas, ataxia, and neuropathy with MERRF.

A 66-year-old woman with hereditary deafness and multiple symmetric lipomas presented with ataxia, slight myopathy, and neuropathy. Molecular genetic analysis of mitochondrial DNA revealed the adenine to guanine transition at position 8344 in the tRNA gene for lysine that has been associated with the myoclonic epilepsy and ragged red fiber (MERRF) syndrome. The deafness was transmitted by the patient's father and may have been an unrelated autosomal defect rather than a paternally transmitted mitochondrial point mutation.

Aged↗
PubMed1994

Mitochondrial encephalomyopathies: clinical and molecular analysis.

The classification of mitochondrial encephalomyopathies relied upon clinical, biochemical, and histological features until the discovery of mitochondrial DNA defects in 1988. Since then, an outburst of molecular genetic information has aided our understanding of the pathogenesis and the classification of these heterogeneous disorders. Novel concepts of maternal inheritance, mitochondrial DNA (mtDNA) heteroplasmy, tissue distribution, and threshold have explained many of the clinical characteristics. The discovery of point mutations, large-scale mtDNA deletions, duplications, and autosomally inherited disorders with multiple mtDNA deletions have revealed new genetic phenomena. Despite our rapidly expanding understanding of the molecular genetic defects, many questions remain to be explored to fill the gap in our knowledge of the relationship between genotype and clinical phenotype.

DNA, Mitochondrial↗
PubMed1994

Myophosphorylase deficiency: an unusually severe form with myoglobinuria.

Myophosphorylase deficiency (McArdle disease) is characterized by exercise intolerance that usually starts in childhood. Severe cramps and myoglobinuria are rarely problems in children. We describe an 8-year-old boy with exercise-induced myoglobinuria; he was homozygous for the mutation most commonly encountered in patients with typical McArdle disease.

Child↗
PubMed1994

Mitochondrial DNA deletion: a cause of chronic tubulointerstitial nephropathy.

We report the first case of a mitochondrial DNA (mtDNA) deletion diagnosed by renal biopsy. An eight-year-old girl with megaloblastic anemia and severe growth retardation developed progressive renal insufficiency accompanied by partial Fanconi syndrome. Histologic examination of the renal biopsy disclosed nonspecific chronic tubulointerstitial disease characterized by tubular atrophy and interstitial fibrosis. On ultrastructural examination, tubular cell mitochondria were extremely dysmorphic with prominent size variation, abnormal arborization, disorientation of the cristae and osmiophilic electron-dense inclusions. Functional histochemical stains for mitochondrial enzymes performed on cryostat renal sections revealed focal tubular absence of cytochrome C oxidase (COX), a respiratory chain enzyme partially encoded by mtDNA, with preservation of succinate dehydrogenase (SDH), a respiratory chain enzyme entirely encoded by nuclear DNA (nDNA). Immunoreactivity for COX subunit 2 (encoded by mtDNA) was weak to undetectable in most tubular cells, whereas reactivity for subunit 4 (encoded by nDNA) was intense in all cells. Molecular analysis of the mtDNA of kidney and peripheral blood leukocytes was performed using Southern blot and PCR. Both techniques disclosed a 2.7 kb mtDNA deletion located between nucleotide (nt) 9700 and nt 13700, a common site for mtDNA deletions associated with encephalomyopathies. Mitochondrial DNA deletions may be an under-recognized cause of idiopathic tubulointerstitial nephropathy in children lacking neurologic or myopathic manifestations.

Biopsy↗
PubMed1994

Distribution of wild-type and common deletion forms of mtDNA in normal and respiration-deficient muscle fibers from patients with mitochondrial myopathy.

We studied the cellular distribution of both deleted (delta) and wild-type (wt) mitochondrial DNAs (mtDNAs) in 'normal' and respiration-deficient muscle fibers from four patients with mitochondrial myopathy. PCR-based methods were used to quantitate both relative and absolute amounts of delta- and wt-mtDNAs in microdissected fiber segments. Although delta-mtDNAs were present in normal fibers (31% +/- 26), their percentages were much higher in affected fibers (95% +/- 2). Absolute levels of delta-mtDNA were also increased in affected fibers, whereas levels of wt-mtDNA were significantly reduced in these fibers. These results indicate that a threshold ratio of delta-/wt-mtDNA must be achieved before an impairment of respiration is observed in muscle. Moreover, the marked reduction in wt-mtDNA observed in affected fibers suggests that absolute amounts of mtDNA may play a role in the pathogenesis of mitochondrial myopathies.

Adolescent↗
PubMed1994

Aberrant splicing in adult onset glycogen storage disease type II (GSDII): molecular identification of an IVS1 (-13T-->G) mutation in a majority of patients and a novel IVS10 (+1GT-->CT) mutation.

Two newly identified splice site mutations (IVS1 -13T-->G and IVS10 +1GT-->CT) were found in a patient with adult onset of the autosomal recessive disorder glycogen storage disease type II (GSDII). The IVS1 -13T-->G transversion in the acceptor splice site was found on one allele in over two thirds of adult onset GSDII patients studied (28/41), but was not seen in 58 normal or 12 infantile onset GSDII chromosomes. Molecular analysis of cDNA from the index patient and four additional, ethnically different, individuals carrying the IVS1 -13T-->G transversion showed splicing out of the first coding exon as well as rare utilization of a cryptic splice site in the exon. An IVS10 +1GT-->CT transversion, unique to the index patient, was detected on the second chromosome. The IVS10 +1GT-->CT results in splicing out of exon 10 including part of the enzyme catalytic site. Additionally, a large deletion encompassing exon 18, previously described in four unrelated patients, was also detected in three unrelated adult GSDII patients, two of whom carried the IVS1 -13T-->G transversion. The frequency of the IVS1 splice site mutation suggests that detection of this mutation could potentially aid in the diagnosis of the phenotypically variable syndrome of adult onset GSDII. The finding that the -13T-->G mutation is a very common mutation in adult onset GSDII patients of varying ethnic and racial backgrounds, suggests that it is either an ancient mutation or confers a selective advantage. Although to our knowledge these are the first splice site mutations to be reported for GSDII, additional splice site mutations are likely and could provide the basis for later onset disease in GSDII.

Adult↗
PubMed1994

Extremely high levels of mutant mtDNAs co-localize with cytochrome c oxidase-negative ragged-red fibers in patients harboring a point mutation at nt 3243.

A single mtDNA point mutation at nt 3243 has been associated with two different clinical phenotypes: mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes ('MELAS3243') and progressive external ophthalmoplegia ('PEO3243'). It has been shown that there is a much higher proportion of ragged-red fibers (RRF) with cytochrome c oxidase (COX) deficiency in PEO3243 than in MELAS3243. Using PCR/RFLP analysis of isolated individual skeletal muscle fibers from patients with both syndromes, we found a direct correlation between the localized concentration of the nt 3243 mutation and impairment of COX function at the single muscle fiber level: we found relatively low levels of mutant mtDNAs (56 +/- 21%) in 'normal' fibers; high levels (90 +/- 6%) in COX-positive RRF; and an almost complete segregation of mutant mtDNAs (95 +/- 3%) in COX-negative RRF. Thus, the differential distribution of fibers with extremely high concentrations of mutant mtDNAs characterizes, and probably distinguishes, the skeletal muscle of PEO and MELAS patients harboring the same nt-3243 mutation.

Analysis of Variance↗
PubMed1994

Clinical and biochemical features of 10 adult patients with muscle phosphorylase kinase deficiency.

Ten adult patients complained of exercise intolerance; five of them had cramps and three had recurrent myoglobinuria. Resting serum CK was increased in five. Muscle biopsies showed phosphorylase b kinase (PbK) deficiency, whereas the activities of other enzymes of carbohydrate metabolism were normal. None of the patients exhibited symptoms indicative of liver PbK deficiency. Thus, these patients are new additions to a class of PbK glycogen storage disease characterized by enzyme deficiency in muscle but not liver. Family histories were consistent with autosomal recessive transmission. Monoclonal antibodies specific for the beta and gamma subunits of PbK cross-reacted differentially with muscle biopsies from three of these patients, suggesting that this phenotype of PbK deficiency is biochemically heterogeneous.

Adolescent↗
PubMed1994

A T-->C mutation at nt 8993 of mitochondrial DNA in a child with Leigh syndrome.

A 5-year-old child with clinical and radiologic evidence of Leigh syndrome (LS) showed a T-->C mutation at position nt 8993 in the mitochondrial DNA (instead of the more common T-->G substitution), resulting in an amino acid change from a highly conserved leucine to proline in subunit 6 of mitochondrial ATPase. The mutation was heteroplasmic and maternally inherited, and was present in high percentages in multiple tissues. This finding documents genetic heterogeneity of the ATPase 6 gene mutation associated with LS.

Adenosine Triphosphatases↗
PubMed1994

Clinical and morphologic features of a myopathy associated with a point mutation in the mitochondrial tRNA(Pro) gene.

We studied a 9-year-old girl with progressive weakness of her extremities for two years. Her neurologic evaluation showed weakness of proximal muscles but no ophthalmoparesis. With the exception of elevated serum lactic acid, the general blood screen, EMG, nerve conduction velocity tests, and ECG were normal. Light and electron microscopy of a muscle biopsy showed proliferation of mitochondria containing disorganized cristae. Activities of respiratory chain enzymes containing mitochondrial DNA (mtDNA)-encoded subunits were significantly impaired in muscle homogenates. A G-->A transition at position 15990 previously detected in this patient's muscle was not present in peripheral blood cells of her mother or sister. However, the patient's WBCs appeared to contain a very small percentage of mutant mtDNAs, indicating that the mutation may have originated during early embryogenesis.

Amino Acid Sequence↗