Homozygous clones in medial regions of the wing disc epithelium show defects in their ability to establish or maintain the pseudostratified columnar cell shape, resulting in their retraction from the apical epithelial surface and subsequent basal extrusion as inverted epithelial cysts. Fewer mutant clones are recovered compared to their twin spot controls in the presumptive medial blade territory, suggesting that some mutant clones undergo cell death. A large number of extruding clones are recovered in the presumptive hinge and notum regions, with a fraction of these extending apically rather than basally. Apical microtubule arrays are eliminated cell-autonomously in homozygous clones in the wing disc, while basal microtubule networks are unaffected. The cells also show a subtle but consistent reduction of F-actin at the basolateral cortex of cells on the clone interior, transient ectopic accumulation of F-actin at the apical adherens junctions and ectopic accumulation of F-actin at boundaries between mutant cells and their wild-type neighbours. Many homozygous clones survive metamorphosis, forming differentiated inverted cuticular vesicles lodged between the dorsal and ventral surfaces of the adult wing or leg.