Polarization of the actin cytoskeleton to the outer rim of migrating border cell clusters. (A–C) Border cell clusters visualized with phalloidin (red) and DAPI (blue) form from a small group of anterior follicle cells that invade the germ line nurse cells at early stage 9 (A), migrate through the egg chamber during stage 9 (B), and reach the oocyte by stage 10 (C). MARCM clones expressing GFP-labeled border cells as well as some follicle cells. (D–F) High magnification views of phalloidin (red) and DAPI (blue) staining in migrating border cell clusters at the indicated stages. Note that F-actin accumulates strongly around the outer rim of the cluster and less so in internal membranes. Bars: (A–C) 50 µm; (D–F)5 µm.