Figure 1. Morphological characteristics of proliferating and differentiating C2C12 cells in vitro. Mouse C2C12 myoblasts were cultured for 3 days in growth medium (DMEM/HG plus10% FBS), followed by 4-day incubation in differentiation medium (DMEM/HG plus 2% HS). (A) Morphological changes in C2C12 cells during the time course of proliferation and differentiation. Representative micrographs were obtained using a light microscope at 40x (upper row) or 100x (lower row) magnification. The arrows indicate mature, multinucleated myotubes. (B) Cell cycle phase distributions during the course of C2C12 growth and myogenesis. (C) Whole-cell lysate immunoblots from cultured C2C12 cells assessing the expression of myogenic differentiation markers (myogenin, MYH, and troponin I) and cell cycle regulators (p21 and cyclin D1). β-actin was used as loading control. (D) RT-PCR analysis of myogenin, MYH, troponin I, p21 and cyclin D1 mRNA in cultured C2C12 cells. GAPDH was used as loading control. Data are presented as means ± SEM.