Actin dynamics are required for the local distribution of Scabrous.

(A) Bristle precursor cell in vivo co-expressing LifeAct-Ruby to label cell shape and ScabrousGFP. Pupae is ~14 hAP. Yellow arrowheads = Scabrous-GFP localized to signaling filopodia. Genotype: UAS-LifeAct-Ruby/UAS-scaGFP; neur-GAL4/+. Scale bar, 10 μm. (B) Timelapse panels of nota explants expressing the filamentous actin marker LifeAct-Ruby and treated with either DMSO or Cytochalasin B. Time in seconds. Either treatment was added at time = 0 seconds. Arrowheads point to individual signaling filopodia on the basal surface. Scale bars, 4 μm (CytB) and 10 μm (DMSO). Genotype: UAS-LifeAct-Ruby/+; pnr-GAL4/+. (C) Immunofluorescence image of a sensory bristle precursor cell from a nota under control conditions for 30 minutes prior to fixation. Signaling filopodia are still visible in F-actin panel. White arrow in Scabrous panel points to intracellular Scabrous. Yellow arrow in Scabrous panel points to local Scabrous. Scale bar, 10 μm. Genotype: neur-GAL4, UAS-GMCA/+. (D) Examples cell morphologies upon DMSO control or Cytochalasin B treatments for 5 minutes. Green, anti-GFP (GFP-actin binding domain of moesin labeling F-actin). Red, anti-Scabrous. Scale bar, 5 μm. Genotype: neur-GAL4, UAS-GMCA/+. (E) Quantification of signaling filopodia length after 5 minutes of treatment with either DMSO (n = 35 filopodia across 17 cells) or Cytochalasin B (n = 36 filopodia across 29 cells). ****, pS2 Fig.