title: Novel mitochondrial tRNA(Ile) m.4282A>G gene mutation leads to chronic progressive external ophthalmoplegia plus phenotype.
abstract: OBJECTIVE
  To investigate the underlying pathomechanism in a 33-year-old female Caucasian patient presenting with chronic progressive external ophthalmoplegia (CPEO) plus symptoms.
  
  
  METHODS
  Histochemical analysis of skeletal muscle and biochemical measurements of individual oxidative phosphorylation (OXPHOS) complexes. Genetic analysis of mitochondrial DNA in various tissues with subsequent investigation of single muscle fibres for correlation of mutational load.
  
  
  RESULTS
  The patient's skeletal muscle showed 20% of cytochrome c oxidase-negative fibres and 8% ragged-red fibres. Genetic analysis of the mitochondrial DNA revealed a novel point mutation in the mitochondrial tRNA(Ile) (MTTI) gene at position m.4282G>A. The heteroplasmy was determined in blood, buccal cells and muscle by restriction fragment length polymorphism (RFLP) combined with a last fluorescent cycle. The total mutational load was 38% in skeletal muscle, but was not detectable in blood or buccal cells of the patient. The phenotype segregated with the mutational load as determined by analysis of single cytochrome c oxidase-negative/positive fibres by laser capture microdissection and subsequent LFC-RFLP.
  
  
  CONCLUSIONS
  We describe a novel MTTI transition mutation at nucleotide position m.4282G>A associated with a CPEO plus phenotype. The novel variant at position m.4282G>A disrupts the middle bond of the D-stem of the tRNA(Ile) and is highly conserved. The conservation and phenotype-genotype segregation strongly suggest pathogenicity and is in good agreement with the MTTI gene being frequently associated with CPEO. This novel variant broadens the spectrum of MTTI mutations causing CPEO.
authors.affiliation: Division of Human Genetics, Departments of Pediatrics and Clinical Research, Inselspital, University of Berne, Berne, Switzerland Institute of Clinical Chemistry, Inselspital, University of Berne, Berne, Switzerland Graduate School for Cellular and Biomedical Sciences, University of Berne, Berne, Switzerland.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Jackson
authors.affiliation: Neuromuscular Diseases Centre, Cantonal Hospital St.Gallen, St.Gallen, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Neuwirth
authors.affiliation: Institute of Clinical Chemistry, Inselspital, University of Berne, Berne, Switzerland.
authors.forename: Dagmar
authors.initials: D
authors.lastname: Hahn
authors.affiliation: Institute of Clinical Chemistry, Inselspital, University of Berne, Berne, Switzerland.
authors.forename: J-M
authors.initials: JM
authors.lastname: Nuoffer
authors.affiliation: Division of Neuropathology, Institute of Pathology, Basle University Hospital, Basle, Switzerland.
authors.forename: Stephan
authors.initials: S
authors.lastname: Frank
authors.affiliation: Division of Human Genetics, Departments of Pediatrics and Clinical Research, Inselspital, University of Berne, Berne, Switzerland.
authors.forename: Sabina
authors.initials: S
authors.lastname: Gallati
authors.affiliation: Division of Human Genetics, Departments of Pediatrics and Clinical Research, Inselspital, University of Berne, Berne, Switzerland.
authors.forename: André
authors.initials: A
authors.lastname: Schaller
mesh_terms: D000328:Adult; D004252:DNA Mutational Analysis; D004272:DNA, Mitochondrial / Q000235:genetics; D003576:Electron Transport Complex IV / Q000378:metabolism; D005260:Female; D006801:Humans; D008931:Mitochondria, Muscle / Q000235:genetics*; D018482:Muscle, Skeletal / Q000201:enzymology; D017246:Ophthalmoplegia, Chronic Progressive External / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D010641:Phenotype; D010766:Phosphorylation; D017354:Point Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012355:RNA, Transfer, Ile / Q000235:genetics*; D013385:Succinate Dehydrogenase / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D012355:RNA, Transfer, Ile; D013385:Succinate Dehydrogenase; D003576:Electron Transport Complex IV
keywords: Eye Lids; Genetics; Muscles