During myogenesis, proliferating myoblasts withdraw from the cell cycle and fuse to form an ordered array of large, multinucleated muscle fibers. This highly regulated process can be divided temporally into a series of complex steps: commitment to a myoblast phenotype, acquisition of fusion competence, recognition and adhesion of like myoblasts, fusion of myoblasts into multinucleated myotubes, and differentiation of myotubes into muscle fibers. The end result is differentiated muscle fibers that contain several characteristic proteins, including: specific types of actin, myosin, tropomyosin, and troponin (which form part of the contractile apparatus), creatine phosphokinase, nicotinic receptors to respond to acetylcholine released from motor nerves, and various types of voltage-gated ion channels to generate actions potentials.
Commitment to a myoblast phenotype is an event that occurs early during embryonic development (Cossu et al. 1996). The steps that occur down...
