Polarized epithelial layers protect tissues from the harsh conditions of the outside world, such as the outside of an embryo or the lumen of a gut. This “outside” is faced by an epithelial cell's apical domain, which contains a set of membrane proteins and cytoskeletal elements that is distinct from the proteins found on the cell's basolateral domain (Yeaman et al. 1999). Establishing the differences that define these domains is one of the fundamental challenges confronting an epithelial cell. Several recent papers in the Journal of Cell Biology (Hunter and Wieschaus 2000; Lecuit and Wieschaus 2000; Sisson et al. 2000; Tanentzapf et al. 2000; Wodarz et al. 2000) use Drosophila to explore this process, and they showed surprising parallels among epithelia in Drosophila, vertebrates, and Caenorhabditis elegans.
In the...
