Absence of junctional glutamate receptor clusters in Drosophila mutants lacking spontaneous transmitter release

Little is known about the functional significance of spontaneous miniature synaptic potentials, which are the result of vesicular exocytosis at nerve terminals. Here, by using Drosophila mutants with specific defects in presy naptic function, we found that glutamate receptors clustered normally at ne uromuscular junctions of mutants that retained spontaneous transmitter secr etion but had Lost the ability to release transmitter in response to action potential. In contrast, receptor clustering was defective in mutants in wh ich both spontaneous and evoked vesicle exocytosis were absent. Thus, spont aneous vesicle exocytosis appears to be tightly Linked to the clustering of glutamate receptors during development.