myotube differentiation skeletal muscle cell differentiation skeletal muscle fiber differentiation 2013-10-15T14:00:34Z The process in which a relatively unspecialized cell acquires specialized features of a skeletal muscle fiber cell. Skeletal muscle fiber differentiation starts with myoblast fusion and the appearance of specific cell markers (this is the cell development step). Then individual skeletal muscle fibers fuse to form bigger myotubes and start to contract. biological_process GO:0098528 dos