The Ds ICD has context-dependent effects on tissue growth. (A) Structure of Ds^ΔICD:GFP. The ICD was replaced with GFP (green) using CRISPR-Cas9. ICD (red line) and TM, transmembrane domain (sky blue). (B and C) Localization of Ds^:GFP in a ds^GFP homozygote (B) and Ds^ΔICD:GFP in a ds^ΔICD:GFP homozygote (C). Ds:GFP and Ds^ΔICD:GFP localize at the junctional cortex. Adherens junctions are marked by DE-Cad staining. (D) Ft localization is normal in ds^ΔICD:GFP mutant cells. Mutant clones are marked with the absence of nuclear GFP. (E–G) Representative adult wings in indicated genotypes. The ds^ΔICD:GFP wing displays undergrowth (F). (H) Quantification of wing size in wild-type, ds^ΔICD:GFP, and ds^ΔICD (GFP-) mutants. ****P < 0.0001, ns, not significant (two-tailed unpaired t test between each genotype). Wild-type (n = 21), ds^ΔICD:GFP (n = 21), ds^ΔICD (n = 22). (I–M) Growth of wing discs with the indicated ds and ft alleles. Genotypes: wild-type (I), ds^ΔICD:GFP (J), ds^UAO71 (K), ft^G-rv/ft^fd (L), and ds^ΔICD:GFPft^G-rv/ds^ΔICD:GFPft^fd (M). Although loss of the Ds ICD leads to undergrowth (J), in combination with loss of ft mutant it causes severe overgrowth (M). Panels L and M were stitched together because of their large size. Scale bars, (B and C) 1 µm, (D) 5 µm, and (E–G and I–M) 100 µm.