Fig. 1. Tyrosyl phosphorylation and SHP-2 protein expression during myogenic differentiation in the murine C2C12 cell line. C2C12 myoblasts were cultured either in the presence of growth medium (GM) or in differentiation medium (DM) for the indicated times as described in Materials and Methods. (A) (Top) Total cell lysates were prepared, separated by SDS-PAGE and immunoblotted with 4G10 anti-phosphotyrosine antibodies (pTyr). The arrows to the right indicate either specific proteins or a molecular mass range in which total tyrosyl-phosphorylation changes are observed during differentiation. The molecular mass markers (Gibco-BRL) are depicted on the left. (Bottom) Representative photomicrographs of C2C12 myoblasts, fixed in methanol and visualized with Wright Giemsa Stain, at each stage of differentiation corresponding to the total tyrosyl-phosphorylation analysis in top panel. (B) C2C12 cell lysates (50 µg) prepared from A were immunoblotted with the indicated antibodies. The positions of molecular mass markers are shown.