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  • 1
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] The molecular mechanisms by which the nuclear genome regulates the biosynthesis of mitochondrial DNA (mtDNA) are only beginning to be unravelled. A naturally occurring in vivo model for a defect in this cross–talk of two physically separate genomes is a human disease, an autosomal dominant ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1459
    Keywords: Mitochondrial encephalomyopathy ; Chronic progressive external ophthalmoplegia ; Lactic acidosis ; Stroke-like episodes ; Ragged-red fibres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied 22 subjects carrying the A3243G point mutation of human mitochondrial DNA (mtDNA). In 14 cases the clinical phenotype was characterized by mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), while 8 patients had chronic progressive external ophthalmoplegia (CPEO). The proportion of A3243G heteroplasmy in muscle was determined by two methods: densitometry on a diagnostic restriction-fragment length polymorphism and solid-phase mini-sequencing. We found a highly significant inverse correlation between the percentage of A3243G mutation and the specific activity of complex 1, the respiratory complex with the highest number of mtDNA-encoded subunits, suggesting a direct effect of the mutation on mtDNA translation. No correlation was observed between the percentage of mutated mtDNA and the presence or absence of specific clinical features, such as stroke, ophthalmoplegia and diabetes mellitus. However, in the MELAS group the percentage of mutated mtDNA molecules was strongly correlated with the age of onset, while no such correlation was found in the CPEO group, suggesting a different time-dependent evolution of the mutation in the two groups. Finally, in contrast with other mtDNA mutations associated with ragged-red fibres (RRF), in both MELAS3243 and CPE03243 we observed a high proportion of RRF that were positive to the histochemical reaction to cytochromec oxidase, a morphological feature that seems to be specific for the neuromuscular phenotypes associated with mutations affecting the tRNALeu(UUR) gene.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1459
    Keywords: Early-onset encephalomyopathy ; Mitochondrial DNA depletion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A male infant, born from consanguineous parents, suffered from birth with a progressive neuromuscular disorder characterized by psychomotor delay, hypotonia, muscle weakness and wasting, deep-tendon areflexia and spastic posture. High levels of lactic acid in blood and cerebrospinal fluid suggested a mitochondrial respiratory chain defect. Muscle biopsy revealed raggedred and cytochromec oxidase-negative fibres, lipid accumulation and dystrophic changes. Multiple defects of respiratory complexes were detected in muscle homogenate, but cultured fibroblasts, myoblasts and myotubes were normal. Southern blot analysis showed markedly reduced levels of mitochondrial DNA (mtDNA) in muscle, while lymphocytes, fibroblasts and muscle precursor cells were normal. Neither depletion of mtDNA nor abnormalities of the respiratory complexes were observed in innervated muscle fibres cultured for as long as 4 months. No mutations were observed in two candidate nuclear genes,mtTFA andmtSSB, retro-transcribed, amplified and sequenced from the proband's mRNA. Sequence analysis of the mtDNA D-loop and of the origin of replication of the mtDNA light strand failed to identify potentially pathogenic mutations of these replicative elements in the proband's muscle mtDNA. Our findings indicate that mtDNA depletion is due to a nuclear encoded gene and suggest that the abnormality underlying defective mtDNA propagation must occur after muscle differentiation in vivo.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 121-130 
    ISSN: 1573-6881
    Keywords: mtDNA ; multiple mtDNA deletions ; mtDNA depletion ; PEO ; oxidative phosphorylation ; respiratory chain ; mitochondrial disorders ; mitochondrial replication ; maternal inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract In addition to sporadic or maternally-inherited mutations of the mitochondrial genome, abnormalities of mtDNA can be transmitted as mendelian traits. The latter are believed to be caused by mutations in still unknown nuclear genes, which deleteriously interact with the mitochondrial genome. Two groups of mtDNA-related mendelian disorders are known: those associated with mtDNA large-scale rearrangements and those characterized by severe reduction of the mtDNA copy number. The most frequent presentation of the first group of disorders is an adult-onset encephalomyopathy, defined clinically by the syndrome of progressive external ophthalmoplegia “plus,” genetically by autosomal dominant transmission of the trait, and molecularly by the presence of multiple deletions of mtDNA. The second group of disorders comprises early-onset, organ-specific syndromes, associated with mtDNA depletion, that are presumably transmitted as autosomal recessive traits. Linkage analysis and search for candidate genes are two complementary strategies to clarify the molecular basis of these disorders of the nuclear-mitochondrial intergenomic signalling.
    Type of Medium: Electronic Resource
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