(A-L) Localisation of Stranded at second (Sas, A,B), Enabled (Ena, C,D), Actin (E,F), Zipper (Zip, E’,F’), Echinoid (Ed, G,H), phosphotyrosine (PY, G’,H’), Bazooka (Baz, I,J), and DE-cadherin (DE-cad, K,L) at the beginning of stage 14. In all images the AS is at the top half, for the genotypes w;foscrb;crbGX24 and w;foscrbY10A;crbGX24. Filopodia extend dorsally in foscrb embryos (A, arrow), but in foscrbY10A embryos filopodia are absent (B, arrowhead) or disorganised (B, empty arrowhead). Ena, Actin and Zip concentrate at the LE in foscrb embryos (C,E and E’, arrows), but these proteins are almost absent from the LE in foscrbY10A embryos (D,F and F’, arrowheads). Ed is absent from the LE of foscrb embryos (G, arrowhead), but the DME cells of foscrbY10A embryos show an important decrease of the protein (H, magenta overlay) though the PY staining is still clearly associated with the ZA in the same cells (H’, magenta overlay). Similarly, Baz decreases at the LE of foscrb embryos (I, arrowhead), but in foscrbY10A embryos, the cells that do not elongate keep Baz at the LE (J, arrow), while other DME cells show a reduction of Baz (J, and Figure 2—figure supplement 3). DE-cad (mTomato signal) localises at all cell-cell contacts in foscrb embryos (K). However, in foscrbY10A, the DE-cad localisation is affected in both the dorsal epidermis (L, solid arrowhead) and the AS (L, empty arrowheads). Scale bar: 10 μm. (M) Schematic representation of the changes in DME cells at the beginning of DC in embryos expressing either fosCrb or fosCrbY10F. The elongation of the DME cells is accompanied by the removal of the Crb protein complex, Ed, Baz and the septate junction components from the LE. At the LE a supracellular actomyosin cable is established and filopodia extend dorsally and attach to the AS cells. Representative images from 8–12 different embryos for each genotype. (N) Schematic representation of the defects in the DME cells of embryos expressing the fosCrbY10A variant. At the beginning of DC, the DME cells do not elongate uniformly. In the cells that do not elongate, the Crb protein complex and Baz remain at the LE. Reduced DE-cad suggest defects in the ZA function. Ed is dramatically reduced in DME cells, probably contributing to the absence of the supracellular actomyosin cable. Also, the DME cells exhibit disorganised filopodia. Nevertheless, the septate junction components are properly removed from the LE. The Crb protein complex is apical to the ZA, but Ed and the actomyosin cable are associated with the ZA.