[Regulation of synaptogenesis in the adult skeletal muscle]

Several behaviors that axons exhibit during reinnervation of adult skeletal muscle demonstrate that they are guided by cues that the muscle provides. For example, axons form synapses on denervated but not on normally innervated muscle fibers; axons selectively reinnervate original synaptic sites on denervated muscle fibers; regenerating axons become specialized for synaptic transmission only in regions where they contact muscle fibers; and motor axons prefer to reinnervate muscles derived from matching levels of the body's rostro-caudal axis. This chapter describes these phenomena and summarizes progress toward identifying the soluble, membrane-bound, and extracellular matrix molecules that underly them.