Terminal msn clones induce a novel invasion phenotype. (A) Transverse section showing that a posterior terminal msn clone causes neighboring wild-type cells (GFP) to invade the germ cells (arrowheads). (B) An invasion event (arrowheads) does not disrupt planar polarization of the basal actin filaments. (C) Expressing msn-RNAi exclusively in the anterior follicle cells (GFP) also causes invasion (arrowheads). (D) Initial and final frames of a time lapse (Video 4) taken of an msn¹⁷² mosaic egg chamber with an anterior terminal clone (bracket). Wild-type cells (GFP) adjacent to the mutant clone invade the germ cells (arrowheads). (E) Stills from the same time lapse acquired at the basal surface show that the noninvading wild-type cells continue to migrate. Bars are as indicated in the figure. (F) Model for how the invasion phenotype develops over time.