Crumbs (Crb) was the first Drosophila gene shown to be a key developmental regulator of epithelial apical-basal polarity (1). The transmembrane protein Crb is now known to be one of many protein complexes along the plasma membrane that participate in cell-to-cell contacts, such as zonulae adherentes. The molecular interactions of Crb with other proteins controlling epithelial cell polarity in Drosophila are actively being explored (2,3). CRB1, one of three Crb human homologues (4), came to scientific and medical attention when mutations in this gene were identified in severe forms of retinal blindness known as retinitis pigmentosa (RP) and Leber congenital amaurosis (LCA) (5–7).