title: High mutational burden in the mtDNA control region from aged muscles: a single-fiber study.
abstract: The ageing process is associated with the accumulation of somatic mutations of mitochondrial DNA (mtDNA). The aged human skeletal muscle tissue presents a mosaic of fibers when stained histochemically for cytochrome c oxidase (COX) activity with a proportion of COX negative fibers. Given the potential relevance of any alteration in the mtDNA control region for replication, we analysed the correlation between the presence of mutations and their degree of heteroplasmy and the COX phenotype in individual muscle fibers of aged healthy donors.A region of the mtDNA D-loop was cloned from single fiber-derived DNA and multiple clones were analysed. This strategy showed that a high level of mutational burden is present in all fibers and that several types of mtDNA rearrangements are detectable: recurrent (A189G, T408A and T414G) and rare point mutations, length variations affecting the homopolymeric tract and the (CA)(n) repeat and macrodeletions. The aggregate mutational load in the D-loop region correlated with the single fiber COX phenotype, suggesting that the cumulative burden of multiple, individually rare, mtDNA alterations might functionally impair the mitochondrial genetic machinery.
authors.affiliation: Centro Dino Ferrari, Centro di Eccellenza per le Malattie Neurodegenerative, Dipartimento di Scienze Neurologiche, Università degli Studi di Milano, I.R.C.C.S. Ospedale Maggiore Policlinico, Via F. Sforza, 35, 20122 Milan, Italy. gpcomi@mailserver.unimi.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Del Bo
authors.forename: Marco
authors.initials: M
authors.lastname: Crimi
authors.forename: Monica
authors.initials: M
authors.lastname: Sciacco
authors.forename: Giulia
authors.initials: G
authors.lastname: Malferrari
authors.forename: Andreina
authors.initials: A
authors.lastname: Bordoni
authors.forename: Laura
authors.initials: L
authors.lastname: Napoli
authors.forename: Alessandro
authors.initials: A
authors.lastname: Prelle
authors.forename: Ida
authors.initials: I
authors.lastname: Biunno
authors.forename: Maurizio
authors.initials: M
authors.lastname: Moggio
authors.forename: Nereo
authors.initials: N
authors.lastname: Bresolin
authors.forename: Guglielmo
authors.initials: G
authors.lastname: Scarlato
authors.forename: Giacomo
authors.initials: G
authors.lastname: Pietro Comi
mesh_terms: D000368:Aged / Q000502:physiology*; D000369:Aged, 80 and over; D001706:Biopsy; D004252:DNA Mutational Analysis; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000235:genetics*; D006801:Humans; D018485:Muscle Fibers, Skeletal / Q000201:enzymology / Q000473:pathology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000473:pathology / Q000502:physiology*; D017354:Point Mutation; D012016:Reference Values
chemical_list: D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV