Cm. Schuster et al., GENETIC DISSECTION OF STRUCTURAL AND FUNCTIONAL COMPONENTS OF SYNAPTIC PLASTICITY .2. FASCICLIN-II CONTROLS PRESYNAPTIC STRUCTURAL PLASTICITY, Neuron, 17(4), 1996, pp. 655-667
Increased neuronal activity (eag Shaker mutants) and cAMP concentratio
n (dunce mutants) lead to increased synaptic structure and function at
the Drosophila neuromuscular junction. Here, we show that the increas
e in synaptic growth is accompanied by an similar to 50% decrease in s
ynaptic levels of the cell adhesion molecule Fasciclin II (Fas II). Th
is decrease in Fas II is both necessary and sufficient for presynaptic
sprouting; FasII mutants that decrease Fas II levels by similar to 50
% lead to sprouting similar to eag Shaker and dunce, while transgenes
that maintain synaptic Fas II levels suppress sprouting in eag Shaker
and dunce. However, FasII mutants that cause a 50% increase in bouton
number do not alter synaptic strength; rather, evoked release from sin
gle boutons has a reduced quantal content, suggesting that the wild-ty
pe amount of release machinery is distributed throughout more boutons.