Transheterozygous interactions among Abl, Gef26, Epac, Rap1, and Vav during Gbb-induced presynaptic macropinocytosis and synaptic growth. (A) Representative NMJ 6/7 images of third instar larvae of indicated genotypes labeled with anti-HRP (green) following a 5-min pulse with TMR-Dex (red, 2 mg/ml) containing Gbb (50 ng/ml). Arrowheads indicate TMR-Dex-positive puncta within HRP-labeled presynaptic terminals. Scale bar, 2 μm. (B) Quantification of the number of TMR-Dex-positive puncta per bouton (n = 30 NMJ branches). Data represent mean ± SEM. Comparisons are with Gbb-unstimulated wild type (***, P < 0.001 by one-way ANOVA with multiple comparisons). (C) Representative NMJ 6/7 images of third instar larvae of indicated genotypes labeled with anti-HRP. Insets show higher magnification views of the areas marked by asterisks. Arrowheads indicate satellite boutons budding off axon terminal arbors. Scale bar: 20 μm. (D) Quantification of total and satellite bouton numbers normalized to muscle area. n = 15 NMJs. Data represent mean ± SEM. Comparisons are with the wild type (*, P < 0.05; **, P < 0.01; ***, P < 0.001 by one-way ANOVA with multiple comparisons).