Differentiation of myoblast cell lines and biological methylation: 3-Deazaadenosine stimulates formation of multinucleated myofibers

Treatment of myoblast cell lines with 3-deazaadenosine stimulates differentiation into myofibers. Myoblast clone L5/3B5, which does not form myofibers after 6 days in fusion medium, was stimulated form myofibers after 5 days of culture in fusion medium containing 50 μM 3-deazaadenosine. Myoblast clone L5/3C4, which normally begins to form myofibers after 4 days in fusion medium, was stimulated by 50 μM 3-deazaadeosine to form myofibers after 3 days in culture and the extent of fusion was also increased. In the presence of 100 μM homocysteine thiolactone, the concentration of 3-deazaadenosine that stimulated maximal fusion was reduced by a factor of 10, from 50 μM to 5 μM 3-deazaadenosine. Stimulation of myofiber formation by 3-deazaadenosine suggests a requirement for one or more methylation reactions in myoblast differentiation and the potentiation by homocysteine thiolactone indicates that myofiber formation is specifically stimulated by an intracellular accumulation of 3-deazaadenosylhomocysteine.