BMP Receptor in the Neuromuscular Junction

Abstract

During development, neuromuscular junctions (NMJs) that form between motor neurons and muscle fibers are continually modified, forming new branches and boutons. Aberle et al. and Marques et al. have identifed a type II receptor for bone morphogenetic protein (BMP) in presynaptic motor neurons of the Drosophila NMJ that regulates this synaptic growth. Drosophila larvae that lacked the receptor, called wishful thinking (Wit), had smaller sized NMJs that showed reduced association between pre- and postsynaptic membranes that may be attributed to the concomitant decrease in the NMJ adhesion molecule Fas II. There was also a decrease in bouton number and increased spacing between them, but their morphology appeared otherwise normal. Electropysiological studies showed that mutant motor terminals released less neurotransmitter, possibly due to a decrease in the number of active zones. Thus, Wit plays a major role in regulating presynaptic growth at the NMJ. An activating ligand and its cellular source have yet to be determined.G. Marques, H. Bao, T. E. Haerry, M. J. Shimell, P. Duchek, B. Zhang, M. B. O'Connor, The Drosophila BMP type II receptor Wishful Thinking regulates neuromuscular synapse morphology and function. Neuron 33, 529-543 (2002). [Online Journal]H. Aberle, A. P. Haghighi, R. D. Fetter, B. D. McCabe, T. R. Magalhaes, C. S. Goodman, wishful thinking encodes a BMP type II receptor that regulates synaptic growth in Drosophila. Neuron 33, 545-558 (2002). [Online Journal]