RNAi screen identifies kinases and phosphatases essential for synapse stability. (A–F) NMJs on muscles 1/9 and 2/10 were stained for the presynaptic active zone marker Brp (green), postsynaptic glutamate receptors (DGluRIII, red), and the presynaptic membrane marker Hrp (white). (A) A stable wild-type NMJ on muscles 1/9. (B–F) RNAi-mediated knockdown of the indicated kinases or phosphatases caused synaptic retractions that ranged from a few unopposed postsynaptic profiles (E) to the elimination of all presynaptic markers (B). Asterisks indicate regions shown at high magnification. (G) Quantification of synaptic retraction frequencies (**, P ≤ 0.01; ***, P ≤ 0.001; n = 9–15 animals, muscles 1/9 and 2/10). Two independent RNAi lines were analyzed when available (PP2A, CKIα, Mnb, and PI4K). (H) Quantification of synaptic retraction severity. Bars: (main panels) 10 µm; (enlarged panels below) 5 µm. Error bars represent SEM.