Cm. Schuster et al., GENETIC DISSECTION OF STRUCTURAL AND FUNCTIONAL COMPONENTS OF SYNAPTIC PLASTICITY .1. FASCICLIN-II CONTROLS SYNAPTIC STABILIZATION AND GROWTH, Neuron, 17(4), 1996, pp. 641-654
The glutamatergic neuromuscular synapse in Drosophila forms and differ
entiates into distinct boutons in the embryo and grows by sprouting ne
w boutons throughout larval life. We demonstrate that two axons form s
imilar to 18 boutons on muscles 7 and 6 by hatching and grow to simila
r to 180 boutons by third instar. We further show that, after synapse
formation, the hemophilic cell adhesion molecule Fasciclin II (Fas II)
is localized both pre- and postsynaptically where it controls synapse
stabilization. In FasII null mutants, synapse formation is normal, bu
t boutons then retract during larval development. Synapse elimination
and resulting lethality are rescued by transgenes that drive Fas II ex
pression both pre- and postsynaptically; driving Fas II expression on
either side alone is insufficient. Fas II can also control synaptic gr
owth; various FasII alleles lead to either an increase or decrease in
sprouting, depending upon the level of Fas II.