Deficiency in repair of the mitochondrial genome sensitizes proliferating myoblasts to oxidative damage.
Reactive oxygen species (ROS), generated as a by-product of mitochondrial oxidative phosphorylation, are particularly damaging to the genome of skeletal muscle because of their high oxygen consumption. Proliferating myoblasts play a key role during muscle regeneration by undergoing myogenic differentiation to fuse and restore damaged muscle. This process is severely impaired during aging and in muscular dystrophies. In this study, we investigated the role of oxidatively damaged DNA and its repair in the mitochondrial genome of proliferating skeletal muscle progenitor myoblasts cells and their terminally differentiated product, myotubes. Using the C2C12 cell line as a well-established model for skeletal muscle differentiation, we show that myoblasts are highly sensitive to ROS-mediated DNA damage, particularly in the mitochondrial genome, due to deficiency in 5' end processing at the DNA strand breaks. Ectopic expression of the mitochondrial-specific 5' exonuclease, EXOG, a key DNA base excision/single strand break repair (BER/SSBR) enzyme, in myoblasts but not in myotubes, improves the cell's resistance to oxidative challenge. We linked loss of myoblast viability by activation of apoptosis with deficiency in the repair of the mitochondrial genome. Moreover, the process of myoblast differentiation increases mitochondrial biogenesis and the level of total glutathione. We speculate that our data may provide a mechanistic explanation for depletion of proliferating muscle precursor cells during the development of sarcopenia, and skeletal muscle dystrophies.
Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, United States of America.
Bartosz
B
Szczesny
Gabor
G
Olah
Dillon K
DK
Walker
Elena
E
Volpi
Blake B
BB
Rasmussen
Csaba
C
Szabo
Sankar
S
Mitra
D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D054629:Genome, Mitochondrial / Q000235:genetics*; D051379:Mice; D032446:Myoblasts / Q000166:cytology* / Q000378:metabolism*; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism*
D017382:Reactive Oxygen Species