SYNAPTIC DIFFERENTIATION - THE ROLE OF AGRIN IN THE FORMATION AND MAINTENANCE OF THE NEUROMUSCULAR-JUNCTION

Upon arrival of a motor axon at the muscle fiber, signals released fro m its growth cone initiate the formation of a synapse. This process co nsists of two stages: arrest of axon growth at the target area and dif ferentiation of pre-and postsynaptic cells at the site of nerve-muscle contact. Studies of regenerating neuromuscular junctions in vertebrat es have revealed that important signals for the formation of this syna pse are located in the synaptic basal lamina, and attempts to identify these signals have led to the isolation of agrin and other components . In this review, we discuss the evidence for the involvement of these molecules and their potential functional role in the formation and ma intenance of the neuromuscular junction, with emphasis on agrin.