Fig. 3. Caspase-9 is activated during differentiation. (A) Caspase-9 processing was detected by immunoblotting over a 5-day differentiation time course. Staurosporine-treated (1 µM for 4 hours) C2C12 cells (+ve) were used as a positive control for caspase cleavage. (B) Affinity labelling of the 37-kDa band of processed caspsase-9. C2C12 cells were cultured for 12 hours in growth media (GM) or differentiation media (DM) in the presence or absence of 50 µM biotin-VAD-fmk. Labelled caspases were affinity purified and detected by immunoblot.