SEQUENTIAL ROLES OF AGRIN, MUSK AND RAPSYN DURING NEUROMUSCULAR-JUNCTION FORMATION

Formation of the neuromuscular junction requires a series of reciproca l inductive interactions between the motor neuron and the muscle cell that culminate in the precise juxtaposition of a highly specialized pr esynaptic nerve terminal with a complex postsynaptic endplate on the m uscle surface. Although nerve-derived agrin has long been thought to p lay a key role during neuromuscular junction formation, the molecular mechanisms underlying its actions are only now coming into focus, foll owing the recent discovery that agrin acts via the MUSK receptor tyros ine kinase.