The formation of neuromuscular synapses.

The formation of synapses requires a series of steps including the generation of neurons and their target cells, the guidance of axons to their targets, and the induction of a specialized presynaptic terminal and postsynaptic membrane. This review is primarily concerned with the inductive events that lead to postsynaptic differentiation. Because this phase of synapse formation begins only after motor neurons have navigated to their target muscle cells, the first section of this review summarizes our current understanding of the principles that govern the guidance of motor axons to skeletal muscle cells. The second section will review our current knowledge of signaling molecules and mechanisms that are critical for inducing postsynaptic differentiation. Although the principles and mechanisms of synapse formation are likely to be similar in the PNS and the CNS, much of our understanding about the mechanisms of synapse formation arises from studies of the vertebrate neuromuscular synapse.