Figure 7. The BM exocytic machinery is planar polarized at the basal epithelial surface.

(A) Rab10.T23N expression produces round eggs. (B) YFP-Rab10 is planar polarized at the level of the basal actin filaments. (C) YFP-Rab10’s planar polarization is lost in fat2^N103-2 epithelia. (D) Tango1 and GM130 are also planar polarized, and partially overlap with YFP-Rab10. (E) Live imaging reveals that YFP-Rab10 is enriched at the trailing edge of each migrating cell. (F) fat2^N103–2 epithelia fail to migrate and YFP-Rab10 is mis-polarized. (B–F) Scale bars are 10 μm. (E and F) FM4–64 marks cell membranes. Dashed lines mark the same 3–4 cells at each time point. (G) TIRF microscopy reveals that larger Rab10-positive structures are largely immobile (arrows), while smaller Rab10-positive structures (circles in G′ and G″) move rapidly through the cytoplasm. Scale bars are 2 μm. (H) Speculative model for how planar polarization of BM secretion would synergize with follicle cell migration to create the unusual BM fibrils associated with egg chamber elongation. Illustration adapted from (Bilder and Haigo, 2012). Experiments performed at stages 7–8. See also Figure S7 and Movies S1–S3.