title: In vitro supplementation with dAMP/dGMP leads to partial restoration of mtDNA levels in mitochondrial depletion syndromes.
abstract: Mitochondrial DNA depletion syndrome, a frequent cause of childhood (hepato)encephalomyopathies, is defined as a reduction of mitochondrial DNA copy number related to nuclear DNA. It was previously shown that mtDNA depletion can be prevented by dAMP/dGMP supplementation in deoxyguanosine kinase-deficient fibroblasts. We investigated myotubes of patients diagnosed with mtDNA depletion carrying pathogenic mutations in DGUOK, POLG1 (Alpers syndrome) and TYMP. Differentiating myotubes of all patients and controls were supplemented with different doses of dAMP/dGMP or dAMP/dGMP/dCMP in TYMP deficiency, and analysed for mtDNA/nDNA ratio and for cytochrome c oxidase (COX) activity. Serum deprivation and myotube formation triggered a decrease in mtDNA copy number in DGUOK or POLG1 deficient myotubes, but not in TYMP deficiency and healthy controls. Supplementation with dAMP/dGMP leads to a significant and reproducible rescue of mtDNA depletion in DGUOK deficiency. POLG1 deficient myotubes also showed a mild, not significant increase in mtDNA copy number. MtDNA depletion did not result in deficient COX staining in DGUOK and POLG1-deficient myotubes. Treatment with ethidium bromide resulted in very severe depletion and absence of COX staining in all cell types, and no recovery was observed after supplementation with dAMP/dGMP. We show that supplementation with dAMP/dGMP increases mtDNA copy number significantly in DGUOK deficient myotubes and, leads to a mild, non-significant improvement of mtDNA depletion in POLG1 deficiency. No adverse effect on mtDNA copy number was observed on high-dose supplementation in vitro. Further studies are needed to determine possible therapeutic implications of dAMP/dGMP supplementation for DGUOK deficiency in vivo.
authors.affiliation: Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University of Munich, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Bulst
authors.forename: Angela
authors.initials: A
authors.lastname: Abicht
authors.forename: Elke
authors.initials: E
authors.lastname: Holinski-Feder
authors.forename: Solvig
authors.initials: S
authors.lastname: Müller-Ziermann
authors.forename: Udo
authors.initials: U
authors.lastname: Koehler
authors.forename: Christian
authors.initials: C
authors.lastname: Thirion
authors.forename: Maggie C
authors.initials: MC
authors.lastname: Walter
authors.forename: Joanna D
authors.initials: JD
authors.lastname: Stewart
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Chinnery
authors.forename: Hanns
authors.initials: H
authors.lastname: Lochmüller
authors.forename: Rita
authors.initials: R
authors.lastname: Horvath
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000378:metabolism; D003838:Deoxyadenine Nucleotides / Q000378:metabolism*; D003848:Deoxyguanine Nucleotides / Q000378:metabolism*; D005260:Female; D018628:Gene Dosage; D006801:Humans; D007223:Infant; D008297:Male; D028361:Mitochondrial Diseases / Q000235:genetics / Q000378:metabolism*; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D032446:Myoblasts / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D003838:Deoxyadenine Nucleotides; D003848:Deoxyguanine Nucleotides; C007257:2'-deoxyguanosine 5'-phosphate; C026600:2'-deoxyadenosine triphosphate