a, Satellite cells treated with TGF-β1, with or without Notch activation, were analysed by western blotting for p15, p16, p21 and p27; quantified in b. *P ≤ 0.05 compared with untreated control (0); **P ≤ 0.05 compared with TGF-β. Smad3 co-precipitated proteins (c) were resolved by western blot; genomic DNA (d) was analysed by RT–qPCR, using primers specific for 5’ regions of CDK inhibitors; data are means ±s.d., n = 3. e, qPCR reactions after 44 cycles revealed fragments of expected molecular weight on agarose gel.