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Query: UMLS:C0029089 (ophthalmoplegia)
 3,338 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutations in the human ANT1 gene, coding for the ADP/ATP carrier, are responsible for the autosomal dominant and recessive forms of progressive external ophthalmoplegia, mitochondrial disorders characterized by the presence of multiple deletions of mitochondrial DNA in affected tissues. By introducing these mutations at equivalent position in AAC2, the yeast orthologue of ANT1, we created a suitable model for validation of the pathogenicity of the human mutations. Here, we describe the use of this approach in the case of mutations mapping in domains not conserved between human and yeast, taking advantage of a yAAC2/hANT1 chimeric construction as a template to introduce pathogenic hANT1 mutations. Application to the case of the D104G mutation indicated that the chimeric construction could be a tool for validation of pathogenic ANT1 mutations in yeast.
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PMID:Mutation D104G in ANT1 gene: complementation study in Saccharomyces cerevisiae as a model system. 1643 35

The authors sequenced POLG1, C10ORF2, and ANT1 in 38 sporadic progressive external ophthalmoplegia patients with multiple mitochondrial DNA (mtDNA) deletions. Causative mutations were identified in approximately 10% of cases, with two unrelated individuals harboring a novel premature stop codon mutation (1356T>G). None had a mutation in C10ORF2 or ANT1. In the majority of patients, the primary nuclear genetic defect is likely to affect other unknown genes important for mtDNA maintenance.
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PMID:POLG1, C10ORF2, and ANT1 mutations are uncommon in sporadic progressive external ophthalmoplegia with multiple mitochondrial DNA deletions. 1668 83

Mitochondrial DNA (mtDNA) is maternally inherited. After birth, secondary mtDNA defects can arise. MtDNA depletion is a reduction in the amount of mtDNA in particular tissues. Multiple deletions of mtDNA accumulate as somatic mutations in mainly postmitotic tissues. These disorders of mtDNA maintenance frequently show Mendelian inheritance. Positional cloning has identified several genes involved in the control of mtDNA stability. Recessive mutations in the genes ECGF1, dGK, TK2, SUCLA2 and POLG cause mtDNA depletion syndromes (MDS). Generally, MDS has infantile onset tissue specific features. Mutations in the genes ECGF1, ANT1, C10orf2 and POLG are associated with multiple mtDNA deletions. The nature of these mutations is dominant in ANT1, C10orf2 and POLG and recessive in ECGF1, C10orf2 and POLG. Mutations in these genes frequently cause progressive external ophthalmoplegia (PEO). However clinical heterogeneity results in different neurological syndromes with considerable overlap. The most common features are PEO, neuropathy, myopathy, ataxia, epilepsy and hepatopathy.
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PMID:Autosomal disorders of mitochondrial DNA maintenance. 1689 56

Mitochondrial genetic diseases can result from defects in mitochondrial DNA (mtDNA) in the form of deletions, point mutations, or depletion, which ultimately cause loss of oxidative phosphorylation. These mutations may be spontaneous, maternally inherited, or a result of inherited nuclear defects in genes that maintain mtDNA. This review focuses on our current understanding of nuclear gene mutations that produce mtDNA alterations and cause mitochondrial depletion syndrome (MDS), progressive external ophthalmoplegia (PEO), ataxia-neuropathy, or mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). To date, all of these etiologic nuclear genes fall into one of two categories: genes whose products function directly at the mtDNA replication fork, such as POLG, POLG2, and TWINKLE, or genes whose products supply the mitochondria with deoxynucleotide triphosphate pools needed for DNA replication, such as TK2, DGUOK, TP, SUCLA2, ANT1, and possibly the newly identified MPV17.
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PMID:Inherited mitochondrial diseases of DNA replication. 1789 33

Mutations in OPA1, a dynamin-related GTPase involved in mitochondrial fusion, cristae organization and control of apoptosis, have been linked to non-syndromic optic neuropathy transmitted as an autosomal-dominant trait (DOA). We here report on eight patients from six independent families showing that mutations in the OPA1 gene can also be responsible for a syndromic form of DOA associated with sensorineural deafness, ataxia, axonal sensory-motor polyneuropathy, chronic progressive external ophthalmoplegia and mitochondrial myopathy with cytochrome c oxidase negative and Ragged Red Fibres. Most remarkably, we demonstrate that these patients all harboured multiple deletions of mitochondrial DNA (mtDNA) in their skeletal muscle, thus revealing an unrecognized role of the OPA1 protein in mtDNA stability. The five OPA1 mutations associated with these DOA 'plus' phenotypes were all mis-sense point mutations affecting highly conserved amino acid positions and the nuclear genes previously known to induce mtDNA multiple deletions such as POLG1, PEO1 (Twinkle) and SLC25A4 (ANT1) were ruled out. Our results show that certain OPA1 mutations exert a dominant negative effect responsible for multi-systemic disease, closely related to classical mitochondrial cytopathies, by a mechanism involving mtDNA instability.
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PMID:OPA1 mutations induce mitochondrial DNA instability and optic atrophy 'plus' phenotypes. 1822 90

MtDNA instability is associated with a wide spectrum of clinical presentations, from dominant or recessive progressive external ophthalmoplegia (PEO) to juvenile-onset spino-cerebellar ataxia and epilepsy (SCAE) or infantile Alpers-Huttenlocher syndrome. We present here the clinical and molecular features of a patient with a clinical presentation characterized initially by PEO with mtDNA multiple deletions lately evolving into a severe neurological syndrome, which included sensory and cerebellar ataxia, peripheral neuropathy, parkinsonism, and depression. This complex phenotype is the result of mutations in two distinct proteins, ANT1 and PolgammaA, which cause additive, deleterious effects on mtDNA maintenance and integrity.
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PMID:Additive effects of POLG1 and ANT1 mutations in a complex encephalomyopathy. 1850 26

Multiple deletions of mitochondrial DNA (mtDNA) are associated with different mitochondrial disorders inherited as autosomal dominant and recessive traits. Causative mutations have been found in five genes, mainly involved in mtDNA replication and stability. They include POLG1, the gene encoding the catalytic subunit of mtDNA polymerase (pol gamma), POLG2 encoding its accessory subunit, ANT1 coding the adenine nucleotide translocator and PEO1 which codes for Twinkle, the mitochondrial helicase. Finally OPA1 missense mutations are involved in phenotypes presenting optic atrophy as a major feature.To define the relative contribution of POLG1, POLG2, ANT1 and PEO1 genes to the mtDNA multiple deletion syndromes, we analysed them in a cohort of 67 probands showing accumulation of multiple mtDNA deletions in muscle. The patients were predominantly affected with a mitochondrial myopathy with or without progressive external ophthalmoplegia (PEO). Genetic analysis revealed that 1) PEO1 has a major role in determining familial PEO, since it accounts for 26.8% of familial cases, followed by ANT1 (14.6%) and POLG1 (9.8%); 2) no mutations in any of the known genes were found in 53.7% of probands of this series. Six novel missense mutations contributing to the mutational load of PEO1 gene (p.R334P, p.W315S, p. S426N, p.W474S, p.F478I, p.E479K) were associated with an adult onset PEO phenotype.
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PMID:Novel Twinkle (PEO1) gene mutations in mendelian progressive external ophthalmoplegia. 1857 22

Autosomal-dominant progressive external ophthalmoplegia (adPEO) is a mitochondrial disorder that is characterized by accumulation of multiple mitochondrial DNA (mtDNA) deletions in postmitotic tissues. The disorder is heterogeneous, with five known nuclear disease genes that encode the proteins ANT1, Twinkle, POLG, POLG2, and OPA1. Defects in these proteins affect mtDNA maintenance, probably leading to stalled replication forks, consequent mtDNA deletion formation, and progressive respiratory chain deficiency. Here we present a large adPEO family with multiple mtDNA deletions, whose disease was not explained by mutations in any of the known adPEO loci. We mapped the disease locus in this family to chromosome 8q22.1-q23.3. The critical linkage region contained the RRM2B gene, which encodes the small subunit of the ribonucleotide reductase p53R2, which has previously been shown to be essential for the maintenance of mtDNA copy number. Mutation screening of RRM2B revealed a heterozygous nonsense mutation in exon 9 (c.979C-->T [p.R327X]) in all affected individuals that was absent in 380 control chromosomes. The same mutation was found to segregate in another adPEO family. The mutant mRNA escaped nonsense-mediated decay and resulted in a protein with truncation of 25 highly conserved C-terminal amino acids essential for the interaction with the ribonucleotide reductase subunit R1. We conclude that dominant-negative or gain-of-function mutations in RRM2B are a cause of multiple mtDNA deletions and adPEO.
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PMID:A heterozygous truncating mutation in RRM2B causes autosomal-dominant progressive external ophthalmoplegia with multiple mtDNA deletions. 1966 47

Maintenance and expression of mitochondrial DNA (mtDNA) are essential for the cell and the organism. In humans, several mutations in the adenine nucleotide translocase gene ANT1 are associated with multiple mtDNA deletions and autosomal dominant forms of progressive external ophthalmoplegia (adPEO). The mechanisms underlying the mtDNA instability are still obscure. A current hypothesis proposes that these pathogenic mutations primarily uncouple the mitochondrial inner membrane, which secondarily causes mtDNA instability. Here we show that the three adPEO-associated mutations equivalent to A114P, L98P, and V289M introduced into the Podospora anserina ANT1 ortholog dominantly cause severe growth defects, decreased reactive oxygen species production (ROS), decreased mitochondrial inner membrane potential (Deltapsi), and accumulation of large-scale mtDNA deletions leading to premature death. Interestingly, we show that, at least for the adPEO-type M106P and A121P mutant alleles, the associated mtDNA instability cannot be attributed only to a reduced membrane potential or to an increased ROS level since it can be suppressed without restoration of the Deltapsi or modification of the ROS production. Suppression of mtDNA instability due to the M106P and A121P mutations was obtained by an allele of the rmp1 gene involved in nucleo-mitochondrial cross- talk and also by an allele of the AS1 gene encoding a cytosolic ribosomal protein. In contrast, the mtDNA instability caused by the S296M mutation was not suppressed by these alleles.
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PMID:Suppression of mitochondrial DNA instability of autosomal dominant forms of progressive external ophthalmoplegia-associated ANT1 mutations in Podospora anserina. 1968 37

Autosomal dominant Progressive External Ophthalmoplegias are Mendelian disorders characterized by the accumulation of multiple deletions of mitochondrial DNA in critical tissues. Most of the Autosomal dominant Progressive External Ophthalmoplegias families carry heterozygous mutations in one of three genes: ANT1, encoding the muscle-heart specific mitochondrial adenine nucleotide translocator, Twinkle, encoding the mitochondrial DNA helicase, and POLG1, encoding the catalytic subunit of the mitochondrial DNA-specific polymerase. Mutations in both POLG1 alleles are also found in autosomal recessive Progressive External Ophthalmoplegias sibships with multiple affected members and in apparently sporadic cases. In addition, recessive POLG1 mutations are responsible for three additional diseases: Alpers-Huttenlocher hepatopathic poliodystrophy, Sensory-Ataxic Neuropathy Dysarthria and Ophthalmoplegia and juvenile SpinoCerebellar Ataxia-Epilepsy syndrome. Mitochondrial neuro-gastro-intestinal encephalomyopathy is an autosomal recessive disorder of juvenile onset, caused by mutations in the gene encoding Thymidine Phosphorylase. Thymidine Phosphorylase is involved in the control and maintenance of the pyrimidine nucleoside pool of the cell. Finally, mitochondrial DNA depletion syndrome is a heterogeneous group of disorders characterized by a reduction in mitochondrial DNA copy number. Clinically, they include a myopathic form, a more generalized encephalomyopathic form and a fatal infantile hepato-cerebral syndrome leading to rapidly progressive liver and brain failure. To date, eight genes have been associated with mitochondrial DNA depletion syndrome. Novel disease genes have recently been added to this list, including OPA1 and GFER, and new clinical variants add further complexity to this expanding area of mitochondrial medicine.
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PMID:Encephalomyopathies caused by abnormal nuclear-mitochondrial intergenomic cross-talk. 1977 89


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