Maged1 knockout myoblasts have a lower p21CIP1/WAF1expression level and fail to properly exit from the cell cycle. Wild-type and Maged1 knockout primary myoblasts were induced to differentiate by serum starvation. (A) The p21CIP1/WAF1 RNA level was quantified by qRT-PCR. GAPDH RNA was used for normalization. Data are presented as the ratio relative to the p21CIP1/WAF1 RNA level in wild-type cells at the time of serum starvation (t = 0 h). (B) Fractions of wild-type and Maged1-deficient myoblasts in S phase in GM (0 h) and 24 h after serum starvation. Cells were analyzed by FACS after staining with propidium iodide. (*p < 0.01). (C) BrdU incorporation of differentiating myoblasts was analyzed after 24 h in DM. Data are presented as the fraction of BrdU-labeled cells. (*p < 0.01).