Mechanical severing of larval axons induces changes in presynaptic F-actin and integrin receptors. (A) Diagram of Drosophila fillet preparation upon axotomy (light-blue line) of all proximal neurons descending from the larval brain. This procedure removes the axonal tension exerted at presynaptic compartments. (B) mNGMA-labeled presynaptic actin at NMJs from live larvae with intact brains (left) or upon severing of the brain/axotomy (right) (see also Videos 10 and 11). (C) Quantification of the fluorescence per µm² for the QmNGMA actin marker in whole NMJs. (D) Quantifications of the number of round F-actin assemblies per µm², as well as the area and fluorescence of the individual round presynaptic actin structures. (E) Graphs representing the percentage of NMJ area covered with linear F-actin, as well as the area and fluorescence of the individual assemblies. (F) Immunostaining of integrin-β (cyan) at NMJs of control larvae (C155-Gal4>CTRL³⁵⁷⁸⁵) after 15 min with uncut and cut axons. (G) Integrin-β fluorescence in the HRP-delineated, postsynaptic, and muscle ROIs. (H) Quantifications of the abundance, size, and fluorescence of WEKA-segmented integrin-β structures along linear areas. Box-and-whisker graphs were used to represent the results of the area and fluorescence intensity of the individual presynaptic actin structures and integrin-β entities. Whiskers represent 10^th to 90^th percentile, while the rest of the data points are shown as individual values. The y axis in these graphs represents log₁₀, to capture the broad distribution of the individual values. In bar graphs with linear y axis, error bars represent the SEM. N in bar graphs—NMJs; N in box and whiskers—individual actin assemblies or integrin-β entities. ns—not significant, *P < 0.05, **P < 0.01, and ***P < 0.001 upon the unpaired, nonparametric Mann–Whitney test. Error bars represent the SEM. g–Hedges’ g represents the effect size. Scale bar—2 µm. See Table S1 for detailed genotypes and N.