Membrane fusion in the growth cone-microspike region of embryonic nerve cells undergoing axon elongation in cell culture

Fine structural analysis of embryonic nerve cells undergoing axon elongation in vitro has revealed structural evidence supportive of the time lapse cinematographic observation that extensive areas of active membrane fusion are present in the distal tip of the axon. Pre-fusion membrane alignment and post-fusion strings of vesicles characterize the putative fusions between microspikes, between microspikes and growth cones, and between growth cones and the distal axon. The restriction and possible significance of these apparent fusions are discussed.