Fig. 5: Autophagy regulates the stability of synaptogenic filopodia at axon terminals.
a Live imaging of GFP-Atg5-expressing R7 axon terminals in intact, developing Drosophila brain shows formation of autophagosomes at the bulbous tips of synaptogenic filopodia14 followed by the collapse of filopodia (P + 60%). Repeated three times independently with similar results. b–e Live imaging of R7 axon terminals at P + 60% (during synaptogenesis) revealed increased stability of synaptogenic filopodia in autophagy-deficient R7 terminals (c, d) and decreased stability in R7 terminals with upregulated autophagy (e) compared with control (b). Yellow arrowheads: stable synaptogenic filopodia; white arrowheads: unstable bulbous tip filopodia. Repeated five to ten times independently with similar results. f Number of concurrently existing bulbous tip filopodia per R7 axon terminal per time instance. g Total number of synaptogenic filopodia per R7 axon terminal per hour. Autophagy-deficient R7 terminals exhibit significantly more stable synaptogenic filopodia (>40 min), whereas upregulated autophagy leads to filopodia destabilization. n = 8 terminals per condition. One-way ANOVA and Tukey’s HSD as post-hoc test; *p < 0.05, **p < 0.01, ***p < 0.001. Error bars denote mean ± SEM. Source data are provided as a Source Data file.
