Postsynaptic expression of tetanus toxin light chain blocks synaptogenesisin Drosophila

During the development of the nervous system embryonic neurons are incorpor ated into neural networks that underlie behaviour. For example, during embr yogenesis in Drosophila, motor neurons in every body segment are wired into the circuitry that drives the simple peristaltic locomotion of the larva. Very little is known about the way in which the necessary central synapses are formed in such a network or how their properties are controlled. One po ssibility is that presynaptic and postsynaptic elements form relatively ind ependently of each other. Alternatively, there might be an interaction betw een presynaptic and postsynaptic neurons that allows for adjustment and pla sticity in the embryonic network. Here we have addressed this issue by anal ysing the role of synaptic transmission ire the formation of synaptic input s onto identified motorneurons as the locomotor circuitry is assembled in t he Drosophila embryo. We targeted the expression of tetanus toxin light cha in (TeTxLC) to single identified neurons using the GAL4 system. TeTxLC prev ents the evoked release of neurotransmitter by enzymatically cleaving the s ynaptic-vesicle-associated protein neuronal-Synaptobrevin (n-Syb) [1]. Unex pectedly, we found that the cells that expressed TeTxLC, which were themsel ves incapable of evoked release, showed a dramatic reduction in synaptic in put. We detected this reduction both electrophysiologically and ultrastruct urally. (C) 1999 Elsevier Science Ltd. All rights reserved.