Figure 4: LR asymmetric Myo-II accumulation in A8a epithelial cells.
(a–f) Myo-II protein observed by the GFP fluorescence of sqh::GFP in control (a–c) and myoID dsRNA-expressing flies (d–f), at 23 h APF (a,d), 26 h APF (b,e) and 29 h APF (c,f). Scale bar, 10 μm. (g–l) Rose diagrams showing the mean of the normalized sqh::GFP fluorescence intensities at cell boundaries in the A8a of control (g–i) and myoID knockdown flies (j–l), at 30° intervals of angle θ, at 23 h APF (g,j), 26 h APF (h,k) and 29 h APF (i,l). Right, histograms showing the mean of normalized intensities representing the indicated ranges of angle θ, and error bars indicating s.d. Number of flies, N; number of cell boundaries, n. (m–o) Cell intercalation tracked by sqh:GFP expression. The junction length (red) and Myo-II intensity (blue) are shown in n, and the inverse correlation between junction length and Myo-II intensity is plotted in o. Scale bar, 10 μm. Fly genotypes: sqhAX3/Y; sqh::GFP (a-c, g-i, and m-o), sqhAX3/Y; sqh::GFP; AbdB-GAL4/UAS-myoID dsRNA (d–f and j–l). (p,q) Schematic of germ-band elongation (p) and our model of collective cell migration (q), which are both mediated by cell intercalation. Red arrow: direction of contraction; black arrow: direction of elongation; green line: Myo-II distribution; blue arrow: direction of cellular movement; grey arrow: direction of global cellular flow.
