Myotubes reactivated by CKI KD undergo apoptosis, which can be delayed by forced Bcl-2 expression.

(A) MSC-derived myotubes were transfected with the indicated siRNAs and harvested at the time points shown. The indicated proteins were analyzed by western blotting. GAPDH was used as a loading control. (B) MSC-derived myotubes were transfected with siRNAs to p21 and p27 and mock-treated (mock) or infected with an empty adenoviral vector or a Bcl-2-carrying virus at the indicated multiplicities of infection. The myotubes were continuously incubated with BrdU until fixation, 48 hours later. BrdU incorporation was detected by immunofluorescence and nuclei were counterstained with Hoechs 33258. The percentages of BrdU-positive (BrdU+) and mitotic or micronucleated myotubes (mitoses) are shown. Casp  =  caspase; cl.  =  cleaved; moi  =  multiplicity of infection.