Signaling endosomes trigger synapse assembly.

In this issue of Neuron, Sharma et al. report that target-derived NGF exerts long-distance control of postsynaptic assembly. A major advance is the discovery that TrkA signaling endosomes are retrogradely transported to neuronal dendrites and directly trigger the clustering of postsynaptic density proteins. (c) 2010 Elsevier Inc. All rights reserved.