Mitochondria are dynamic organelles forming a tubular network that is 
continuously fusing and dividing to control their morphology and functions. 
Recent literature has shed new light on a potential link between the dynamic 
behavior of mitochondria and muscle development. In this study, we investigate 
the role of mitochondrial fission factor dynamin-related protein 1 (Drp1) in 
myogenic differentiation. We found that differentiation of C2C12 myoblasts 
induced by serum starvation was accompanied by a gradual increase in Drp1 
protein expression (to ∼350% up to 3 days) and a fast reduction of Drp1 
phosphorylation at Ser-637 (to ∼30%) resulting in translocation of Drp1 protein 
from the cytosol to mitochondria. During differentiation, treatment of myoblasts 
with mitochondrial division inhibitor (mdivi-1), a specific inhibitor of Drp1 
GTPase activity, caused extensive formation of elongated mitochondria, which 
coincided with increased apoptosis evidenced by both enhanced caspase-3 activity 
and increased number of terminal deoxynucleotidyl transferase-mediated dUTP 
nick-end labeling (TUNEL)-positive cells. Furthermore, the mdivi-1-treated 
myotubes (day 3 in differentiation media) showed a reduction in mitochondrial 
DNA content, mitochondrial mass, and membrane potential in a dose-dependent 
manner indicating defects in mitochondrial biogenesis during myogenic 
differentiation. Most interestingly, mdivi-1 treatment significantly suppressed 
myotube formation in both C2C12 cells and primary myoblasts. Likewise, stable 
overexpression of a dominant negative mutant Drp1 (K38A) dramatically reduced 
myogenic differentiation. These data suggest that Drp-1-dependent mitochondrial 
division is a necessary step for successful myogenic differentiation, and 
perturbation of mitochondrial dynamics hinders normal mitochondrial adaptations 
during muscle development. Therefore, in the present study, we report a novel 
physiological role of mitochondrial dynamics in myogenic differentiation.