FIG. 1.
DM cells have the lost ability to withdraw from the cell cycle. (A) Immunostaining of control and DM undifferentiated cells (day 0) and cells maintained in differentiation medium for 5 days (day 5) with antibodies to MyoD. (B) Protein levels of MyoD in control and DM cells, determined by Western blotting. Whole-cell extracts were isolated from the cells on different days after initiation of differentiation (shown on the top) and probed with antibodies against MyoD. The membrane was reprobed with antibodies to β-actin. Induction of MyoD as a ratio to β-actin is shown below the figure. (C) A significant portion of differentiating myoblasts from DM patients reenter the cell cycle. Differentiated myotubes (d5) from normal and DM patients were placed in growth medium. The DNA content was calculated by FACS analysis on days 2 (5–2) and 5 (5–5) after passage and growth in complete medium. The table above the diagrams shows the percentage of cells in the G1, S and G2/M phases of cell cycle.