Cyst maintains epithelial polarity. (A) Schematic of Cyst, Cyst^R (shRNA resistant), and cyst¹. Cyst^R is encoded by a cyst genomic sequence including the endogenous promotor that has been mutagenized to render it immune to cyst shRNA. cyst¹ is a genomic deletion in which cyst sequence has been replaced by GFP driven by the P3 promoter. (B–K) Cuticles of embryos of the indicated genotypes. cyst RNAi (C and I) and scrib RNAi (H and I) embryos were derived from mothers expressing shRNAs with mat-Gal4. cyst¹(M/Z) and lgl⁴(M/Z) are cyst¹ mutant (D, E, and K) and/or lgl⁴ mutant (J and K) germline clones. cyst OE (overexpression), mat-Gal4 UAS-cyst^R embryo (F, n = 30). crb^11A22, crb-null mutant embryo (G). Inset in C shows cuticle vesicles/cysts. The schematics in C and G illustrate the cellular organization of epithelial cysts in cyst- and crb-compromised embryos with cuticle highlighted as gray lines. Insets in H and I show the bubbly cuticle defects typical for scrib-depleted embryos. The schematic in H illustrates the cellular organization of bubbles in scrib-compromised embryos with cuticle highlighted as gray line. Dashed lines encircle cuticle shields. Arrows point to head defects. Scale bars, 100 µm; insets, 25 µm. (L–N) Quantification of cuticle defects of indicated genotypes.