Effect of actin poison on GFP-APC localisation in COS-7 cells. Panels A-D. Treatment of GFP-actin expressing COS-7 cells with 1 μg/ml Cytochalasin D gradually perturbed the integrity of the cortical actin ribbon. With increasing time of exposure to drug the cortical actin ribbon thins, snaps and contracts (arrowheads, additional file 11 arrows). Bars = 20 μm. Panels E-H. Cytochalasin D treatment (1 μg/ml) of cells possessing both microtubule-associated and junctional GFP-APC (additional file 12). Following drug addition cell-cell contacts decorated with GFP-APC puncta can be seen to break (black arrow), followed by movement of the GFP-APC puncta along the cell edge towards cell vertices (white arrow shows direction of movement). The dynamic behaviour of microtubule-associated GFP-APC continues within the constraints imposed by retraction of the free cell edge. Bars = 10 μm. Panels I-K. Paraformaldehyde fixed, phalloidin-stained cells expressing GFP-APC after 30 min treatment with Cytochalasin D (1 μg/ml). Co-localization of GFP-APC with actin aggregates in the cytoplasm (arrows) and with cortical actin (arrowheads) is seen. GFP green, phalloidin red, panel K is a merged image. Bars = 20 μm.