(A) Immunostaining for MHC (green) of Ad.EV (a,c,e,g) or Ad.cre (b,d,f,h) transduced Rbf/f, Rbf/f:p107−/−, Rbf/f:p130−/− and Rbf/f:p107−/−:p130−/− cultures at DM-5 in hypoxia. Inlets, DAPI staining for nuclei. (B) Quantification of myotube formation in Rbf/f, Rbf/f:p107−/−, Rbf/f:p130−/− and Rbf/f:p107−/−:p130−/− cultures transduced with Ad.EV or Ad.cre and induced to differentiate 48 hr later for 5 days. Counts represent the average number of myotubes at DM-5 of 6 representative fields (n = 4); error bars represent s.d. *-p<0.05 and **-p<0.07. (C) Quantification of percent multinucleated myotubes relative to total number of MHC-positive cells in Ad.EV or Ad.cre transduced Rbf/f, Rbf/f:p107−/−, Rbf/f:p130−/− and Rbf/f:p107−/−:p130−/− cultures at DM-5 under hypoxia. Numbers within bars indicate % for respective samples. (D) Quantification of myotube formation in Rbf/f, Rbf/f:p107−/−, Rbf/f:p130−/− and Rbf/f:p107−/−:p130−/− cultures transduced with Ad.EV or Ad.cre and induced to differentiate in hypoxia. Counts were conducted at DM-2 and DM-6. Error bars represent s.d.