Fig. 3. Integrins are required to maintain epithelial polarity in the midgut. Embryos were stained for DE-cadherin to mark the apicolateral surface of the midgut epithelium (A'-D' and green in A-D) and laminin to mark the basal side (magenta in A-D). (A'-C') At stage 15, DE-cadherin is distributed apically and laterally in the midgut epithelium in wild type, ßPS^- and ßPS^- ß^- mutant embryos. (D,D') By stage 16, the midgut epithelium has lost its polarity and become highly disorganized in the absence of zygotic ßPS and maternal and zygotic ß.