FIG. 4.

Calcineurin is sufficient to induce differentiation in an IGF-inhibited cell line. (A to D) C2BP-5 cells failed to differentiate in DM after 48 or 96 h in the absence of exogenous IGF-1 (A and B); however, supplementation with IGF-1 rescued differentiation by 96 h but not by 48 h (C and D). (E and F) AdCnA infection of C2BP-5 myoblasts maintained in DM demonstrated noticeable differentiation by 48 and 96 h. (G and H) AdCnA infection in the presence of IGF-1 promoted even greater differentiation and increased the myotube size by 96 h. (I) Western blotting for total MyHC protein demonstrated that Adβgal-infected C2BP-5 cells completely lacked MyHC protein at 48 or 96 h in the absence of IGF-1 (lanes 3 and 9). However, AdCnA-infected cells displayed abundant MyHC protein expression at 48 and 96 h in the absence of IGF-1 (lanes 5 and 11).