Fig. 4. HERG antisense depolarizes fusion-competent myoblasts and increases the rate of fusion. (A) Control: myoblasts transfected with a bicistronic vector containing only EGFP. AS-HERG: myoblasts transfected with a bicistronic vector expressing HERG antisense and EGFP. Myoblast transfection and fusion index determination are detailed in the Materials and Methods section. Photographs represent Haematoxylin-stained cultures in differentiation medium. Myotubes (arrows) were observed only in cultures of cells transfected with the HERG antisense vector. Scale bars: 40 µm. (B) Resting membrane potential of fusion-competent myoblasts before (-) and after (+) application of 5 µM dofetilide. Myoblasts were transfected as in A.