Assessment for linear F-actin in axons. (A) Diagrams of Drosophila fillet preparations denoting proximal and distal axons along the larva. For simplicity, in the diagram on the left, we denoted only three axonal bundles and a few muscles were left out. On right, distal axons branch out (“exit” marked with red star) from distal axonal bundles (light blue) to form NMJs. (B) Distal axons (blue arrows) of larvae expressing neuronally (nSybQF) the F-actin marker QmNGMA feature possible linear F-actin structures along with visible linear F-actin at the NMJ. In contrast, larvae expressing neuronal (C155-Gal4) GFP exhibit diffuse GFP signal both in the distal axon and at the NMJ. (C) In the narrow axonal shafts of proximal axonal bundles, putative linear F-actin QmNGMA structures are not distinguishable from the distribution of free GFP, either visually or quantified via WEKA segmentation. Error bars represent the SEM. N—axons. ns—nonsignificant upon the unpaired, nonparametric Mann–Whitney test.