Fig. 4. Defects in epithelial organisation associated with unconstrained nuclear shape in char RNAi embryos. Sections showing phalloidin, a marker of F-actin (red), the apical protein Patj (green) and the nuclear dye Hoechst (blue) in control (A,B) and char RNAi (C,D) embryos at the end of cellularisation, viewed from the side (A,C) and from the top (B,D). The white lines define the cell contour determined by the localisation of phalloidin and PatJ. In B and D, z1 and z2 are, respectively, apical and more lateral sections indicated in A and C. The apicobasal morphology of cells is regular in control embryos. In char RNAi embryos, cell shape is irregular: many cells display a small apical section (D, arrows) and others have a larger apical section when the nuclei are located apically (D, arrowheads). Apical markers (PatJ) are abnormally present in the deeper section z2 (D), indicating defects in junctional organisation in char RNAi embryos. Scale bar: 5 µm.