Figure S4.

Additional controls showing presynaptic source of Syt4 and structural plasticity upon Tsg101^KD (associated with Fig. 6). (A and B) Syt4 protein is derived from the presynaptic neuron. (A) Schematic for Tissue-Specific Tagging of Endogenous Proteins (T-STEP). Scissors indicate a Prescission protease cleavage site and * indicates stop codons. (B) Representative confocal images from muscle 6/7, showing Syt4^TSTEP expressed from its endogenous promoter, and switched from TagRFP-T to GFP using either presynaptically (neuronal, C380-GAL4) or postsynaptically (muscle, C57-Gal4)-expressed recombinase (Rippase). Scale bar = 10 µm. (C) Representative confocal images from muscle 6/7 in spaced K⁺-stimulated larvae. Arrows indicate ghost boutons. Scale bar = 20 µm. (D) Quantification of ghost bouton numbers per NMJ. Scale bars = 10 µm. Data is represented as mean ± SEM; n represents NMJs. See Tables S1 and S3 for detailed genotypes, sample sizes, and statistical analyses.