Ds and Ft regulate App at cell junctions. (A–D) Ds, Dachs, and App colocalize at junctional puncta. Representative image (A) and line scan (yellow line) quantification of fluorescence intensity (B) showing colocalization of App:YFP and Dachs:GFP. Representative image (C) and line scan (yellow line) quantification of fluorescence intensity (D) showing colocalization of Ds:GFP and App:YFP. (E) Loss of ft causes mislocalization of App:YFP from junctional puncta to a more uniform distribution across the apical surface (clonal marker not shown). Note that App:YFP accumulates at the boundary between wild-type and ft mutant cells and appears reduced in the cytoplasm of ft cells at the edge of the clone (yellow dots). (F) The localization of App:YFP is altered in ds mutant cells. App:YFP is more diffuse in the absence of Ds and accumulates at the clone boundary (clonal marker not shown). Note that cytoplasmic App:YFP is reduced in ds cells adjacent to the boundary (yellow dots). (G and H) App:YFP accumulates at the boundary between wild-type and ft RNAi cells (G) but fails to accumulate at the boundary in ft, app double RNAi cells (H), indicating that App in ft depleted cells is recruited to contacts with wild-type cells. (I and J) App:YFP accumulates at the boundary between wild-type and ds RNAi cells (I) and at the boundary between wild-type and ds, app double RNAi cells (J), indicating that App in ds depleted cells is not recruited to contacts with wild-type cells. (K) Junctional puncta of App:YFP are much less apparent in ds^ΔICD clones. (L) The Ds ICD co-immunoprecipitates App in S2 cells. (M) Ectopic expression of Ds in the posterior compartment causes Dachs and App:YFP to colocalize in a planar polarized fashion for two to three cell diameters outside the Ds overexpression domain. Yellow dashed lines indicate the anterior/posterior boundary. Scale bars, 5 µm. Source data are available for this figure: SourceData F4.