Neue Einblicke in den Pathomechanismus des mitochondrialen DNA Depletionssyndroms
Zusammenfassung der Projektergebnisse
Mitochondrial DNA depletion syndrome (MDS), 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, P0LG1 (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 P0LG1 deficient myotubes, but not in TYMP deficiency and healthy controls. Supplementation with dAMP/dGMP lead to a significant and reproducible rescue of mtDNA depletion in DGUOK deficiency. P0LG1 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 P0LG1 deficient myotubes. Treatment with ethidium bromide resulted in very severe depletion and absence of COX staining in alt cell types, and no recovery was observed after supplementation with dAMP/dGMP. A milder depletion was triggered with diffderent nucleotide reverse transciptase inhibitors (NRTIs), used for chemotherapy or antiretroviral therapy and this effect was reversed by supplementation. In conclusion we showed 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.
Projektbezogene Publikationen (Auswahl)
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Abnormal neurological features predict poor survival and should preclude liver transplantation in patients with deoxyguanosine kinase deficiency. Liver Transpl 2008;14:1480-1485
Dimmock DP, Dunn JK, Feigenbaum A, Rupar A, Horvath R, Freisinger P, Mousson de Camaret B, Wong LJ, Scaglia F
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Altered cerebral glucose metabolism in a family with clinical features resembling MNGIE in association with multiple mtDNA deletions. Arch Neurol 2008;65:407-411
Lehnhardt FG, Horvath R, Ullrich R, Kracht L, Sobesky J, Möller-Hartmann W, Jacobs AH, Haupt WA
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A variable neurodegenerative phenotype with polymerase gamma mutation. J Neurol Neurosurg Psychiatry 2009;80:1181-1182
Stricker S, Prüss H, Horvath R, Baruffini E, Lodi T, Siebert E, Endres M, Zschenderlein R, Meisel A
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Collated mutations in mitochondrial DNA (mtDNA) depletion syndrome (excluding the mitochondrial gamma polymerase, POLG1). Biochim Biophys Acta 2009 Sep 11. Epub ahead of print
Poulton J, Hirano M, Spinazzola A, Arenas Hernandez M, Jardel C, Lombes A, Czermin B, Horvath R, Taanman JW, Rotig A, Zeviani M, Fratter C
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In vitro supplementation with dAMP/dGMP leads to partial restoration of mtDNA levels in mitochondrial depletion syndromes. Hum Mol Genet 2009;18;1590-1599
Bulst S, Abicht A, Holinski-Feder E, Müller-Ziermann S, Koehler U, Thirion C, Walter MC, Stewart JD, Chinnery PF, Lochmüller H, Horvath R
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Mitochondrial DNA depletion and fatal infantile hepatic failure due to mutations in the mitochondrial polymerase gamma (POLG) gene A combined morphological/enzyme histochemical and immunocytochemical/biochemical and molecular genetic study. J Cell Mol Meo 2009 Jun 16. [Epub ahead of print]
Müller-Höcker J, Horvath R, Schäfer S, Hessel H, Müller-Felber W, Kuhr J, Copeland WC, Seibel P
