The cytoskeletal motor proteins Dynein and MyoV direct apical transport of Crumbs

How epithelial cells polarize is a fascinating unsolved problem in biology. A key determinant of epithelial polarity is the transmembrane protein Crumbs, which localises specifically to the apical domain of epithelial cells and then helps direct the apical-basal polarization of the entire epithelial cell. How Crumbs itself becomes localized apically is still poorly understood. Here we define a key role for two motor proteins which can transport Crumbs apically along microtubules and actin filaments, respectively. Thus, a polarised cytoskeleton directs Crumbs delivery, which then helps define the apical-basal axis, which feeds back to polarize the cytoskeleton - a positive feedback loop.