GFP-BazS980A does not localize properly and causes the formation of protein aggregates when overexpressed. (a) GFP-tagged versions of Baz used in this study. + or − indicate whether overexpression of these variants of Baz causes the dominant-negative phenotype described in Overexpression of nonphosphorylatable Baz phenocopies mutations in crb and sdt. (b) STED imaging reveals localization of GFP-Baz basal to Crb in the embryonic ectoderm. (c) STED imaging reveals colocalization of GFP-BazS980A with Crb (arrow) and localization of GFP-BazS980A apical to Crb (arrowheads) in the embryonic ectoderm. (d) GFP-Baz localizes in dots at the apex of the lateral plasma membrane. (e) Overexpressed GFP-BazS980A localizes to aggregates containing additional proteins, including Crb and DE-cadherin, that are mislocalized to the cytosol. (f and g) Subcellular localization of Baz phosphorylated at S980. Embryos at stage 9 were stained with an antibody that recognizes Baz irrespective of its phosphorylation status (Baz) and with an antibody that recognizes Baz only when it is phosphorylated at S980 (pS980Baz). Note that in the epithelium, both signals overlap only partially, with pS980Baz staining (arrowheads) being enriched at the apical border of larger spots stained with the conventional Baz antibody (arrows). (g) pS980Baz staining is also detectable in the apical cortex of mitotic neuroblasts (asterisks). (d–g) Insets show overviews of the embryos from which the high magnification images were taken. Baz transgenes were overexpressed with da::GAL4. See also Fig. S1. Bars: (b and c) 1 µm; (d–g) 10 µm.