Fig. 6. Induced ablation of Cx43 expression inhibits myogenesis in primary cultures of myoblasts. (A) Western blot analysis of Cx43, myogenin (Myo), MyoD and -tubulin (Tub) in homogenates (100 µg) of Cx43^fl/fl or Cx43^Cre-ER(T)/fl satellite cell-derived myoblasts treated with 4-OH-tamoxifen every 24 hours for 5 days followed by 24 hours of differentiation. (B) At 24 hours of differentiation, positive Cx43 immunolabeling was detected in control Cx43^fl/fl myoblasts (left) but not in 4-OH-tamoxifen-treated cells of Cx43^Cre-ER(T)/fl mice (right; upper panel shows phase contrast view). Scale bar: 40 µm. (C) Bar chart of the incidence of coupling (%) of 4-OH-tamoxifen-treated myoblasts of Cx43^Cre-ER(T)/fl or Cx43^fl/fl mice after 24 hours of differentiation. (D) Bar chart showing the percentage of the average number of nuclei present in myotubes at day 4 of differentiation in 4-OH-tamoxifen-treated myoblasts of Cx43^Cre-ER(T)/fl mice as compared to 4-OH-tamoxifen-treated myoblasts of Cx43^fl/fl mice (**P<0.01 vertical bars indicate the standard deviation (s.d.), n=4 independent experiments). Upper images are phase-contrast views at day 4 of differentiation (D4) of 4-OH-tamoxifen-treated Cx43^fl/fl or Cx43^Cre-ER(T)/fl myoblasts. Scale bar: 40 µm. (E) Bar chart showing the relative creatine kinase activity of cultured myoblasts at day 4 of differentiation. 4-OH-tamoxifen-treated cells were from Cx43^Cre-ER(T)/fl or Cx43^fl/fl mice. (*P<0.05 vertical bars indicate s.d., n=3).