The establishment of planar cell polarity (PCP) – the polarisation of epithelial cells within the plane of the epithelium – is central to the development of many animal organs. To understand how the multiprotein complexes that establish PCP in the Drosophila eye are localised, Das et al. have studied flies mutant for such PCP proteins (see ). They report that, by driving the membrane association of Diego (Dgo), the Wnt receptor Frizzled (Fz) maintains the apical localisation of Flamingo (Fmi), which controls the apical localisation of other PCP factors, including Fz. In this way, a positive-feedback loop is established that controls the initial uniform apical localisation of PCP multiprotein complexes. Later during development,PCP proteins become localised to opposite sides of the cells and, because Dgo is redundant to Prickle (Pk) and Strabismus (Stbm) in maintaining Fmi localisation, the authors speculate that Fz/Dgo and Stbm/Pk maintain Fmi localisation in the R3 and R4 photoreceptors, respectively.
