Figure 3: Myo-II-related LR asymmetric cell intercalation in A8a epithelial cells.

(a) DE-Cad::GFP was observed at all the cell boundaries at 21 h APF. Yellow-boxed region was magnified in b. Scale bar, 50 μm. (b) Time-lapse images of epithelial cell rearrangement and migration in the A8a, visualized with DE-Cad::GFP. Schematic drawing represents the cell intercalation observed in the upper panels (b’). Scale bar, 10 μm. (c) Schematic drawing of the procedure for analysing the angle (θ) between the line formed by each cell boundary and the AP axis. The AP axis of A8a radiates in all directions from the centre of A9 to the A7 epidermis. Because the A8 tergite forms a ring-like structure surrounding the A9 genitalia at the pupal stage, the AP axis of A8 radiates in all directions from the centre of A9 to the A7 epidermis. The cell boundary angles were classified as being in the −90° to 0° (blue arc) or the 0° to 90° (red arc) range. (d) The angle (θ) formed between each cell boundary undergoing cell intercalation and the AP axis before remodelling was measured. (e,g) Cell boundaries visualized with DE-Cad::GFP in control (e) and sqh knockdown flies (g). The AP axis of the A8 (yellow arrow) was defined as the line from the A7 epidermis to the A9 genitalia. The angle (θ) formed between each cell boundary undergoing junction remodelling, followed by cell intercalation and the AP axis was measured. The cell boundary angles were classified as ranging from −90° to 0° (cyan) or 0° to 90° (magenta). Scale bar, 10 μm. (f,h) Rose diagrams depicting the percentage of cell intercalation axes in the A8a of control flies (f) and sqh dsRNA-expressing flies (h) at 30° intervals of the angle θ during cell movement. The percentage of cell boundaries (showing junction remodelling) with angle θ in the ranges indicated are determined. The frequency of cell intercalation was 13.7% (83/607 in five samples) in the control, and 7.3% (53/726 in six samples) in the sqh dsRNA-expressing flies. Right histograms show the percentage of cell intercalation axes in the ranges indicated. Bars indicate s.d. The numbers of flies and cell boundaries analysed are indicated as N and n, respectively. Fly genotype: DE-Cad::GFP (a,b,e,f), DE-Cad::GFP; AbdB-GAL4 UAS-RedStinger/UAS-sqh dsRNA (g,h).