Cleavage of myotubes and cell cycle reactivation have different pathways.

<p>(A), (B) RT/PCR and protein analysis on cells co-transfected with myogenin siRNA and AdMyoD showed normal MyoD levels compared to cells transfected with myogenin siRNA only which showed significantly reduced MyoD levels. Cells co-transfected with myogenin siRNA and AdMyoD showed normal cyclin D1 and cyclin E2 levels compared to cells transfected with myogenin siRNA only, which showed to be substantially increased. Cells co-transfected with negative siRNA and AdC revealed similar levels of cyclin D1 and cyclin E2. Cells transfected with AdMyoD showed to some extent higher myogenin and MyoD levels compared to cells co-transfected with negative siRNA and AdC. GAPDH was used as an internal control. (C) Myotubes transfected as described above were treated with EdU and detected by immunofluorescence. Cells transfected with siRNA myogenin showed significantly high levels of EdU, compared to the cleaved cells co-transfected with myogenin siRNA and AdMyoD. Cells transfected with AdMyoD only or negative siRNA co-transfected with AdC showed no signs of cleavage.