Percentage of Tk2+/+ and Tk2−/− positive cells for myogenin and p21 and of nuclei contained within multinucleated myotubes (fusion index) in growth and differentiation conditions.

The frequency of each marker was calculated from double immunofluorescence experiments of Tk2+/+ and Tk2−/− cells maintained in growth medium or exposed to differentiation medium for 1 or 2 days. The percentage of myogenin or p21 positives and the fusion index were expressed relative to the total number of DAPI stained nuclei in 10 different microscope fields (about 700–800 nuclei counted for each sample).