The generation of epithelial polarity in mammalian and Drosophila embryos

Early mammalian and Drosophila embryos share the ability to generate epithelial cells whose plasma membranes are divided into two non-identical domains. In the past several years, much has been learned about the cellular and molecular mechanisms involved in converting non-polar embryonic cells into polarized epithelia. A comparison of these processes in mammals and Drosophila reveals important differences as well as fundamental similarities. Many of the molecules required to generate and maintain epithelial polarity appear to be shared by both systems.