Dyn2 is directly involved in myoblast fusion. (A) Dyn2 domain structure and the mutations used in this study. (B and C) Fusion efficiency of myoblasts infected with different Dyn2 mutants were imaged (B) and quantified (C). These Dyn2 mutants were tetracycline-regulated and were induced 2 d after differentiation to avoid their effects on differentiation. **, P < 0.01; ***, P < 0.001. (D and E) Distribution of Dyn2 mutants in day 3 differentiated myoblasts. After 2 d of differentiation, C2C12 myoblasts were replated into lower density on fibronectin-coated coverslips and infected with HA-Dyn2 mutants expressing adenoviruses. After 16-h induction, Dyn2 mutants and F-actin were stained and imaged with confocal microscopy. The enrichment of Dyn2 mutants in invadosomes was quantified by the intensity of Dyn2 in actin focus divided by the intensity outside the invadosome (E). 20 cells of each mutant were analyzed. Scale bars, 10 µm.