Wts is not required for border cell specification or membrane polarity. (A) Control egg chamber at mid stage 9 showing the slow border cells expression in the migrating border cell cluster, as revealed by the slbo-lacZ reporter. (B) Stage 10 egg chambers with clusters composed entirely of wts^X1 mutant border cells (MARCM, GFP positive, not depicted) display normal slbo-lacZ expression. (C) Control egg chamber at mid stage 9 showing the unpaired expression in the migrating border cell cluster, as revealed by the upd-lacZ reporter. (D) Stage 10 egg chambers with clusters composed entirely of wts^X1 mutant border cells (MARCM, GFP positive, not depicted). In both wild-type and mutant clusters, the upd expression is restricted to the two polar cells (red arrows). In addition, the expression of the polar cell–specific marker FasIII was unaffected in wts^X1 mutant clusters (not depicted), indicating that Wts is not required to specify border cells or to discriminate between polar cells and outer border cells. Anterior is to the left in all panels. (E) Control cluster at mid stage 9 showing normal aPKC localization to inner membranes. (F) wts^X1 mutant border cell clusters show normal localization of aPKC. (G) Control cluster at mid stage 9 showing normal Armadillo localization to inner membranes. (H) wts^X1 mutant border cell clusters show normal localization of Armadillo. Bars: (A–D) 50 µm; (E–H) 5 µm.