Core planar cell polarity (PCP) proteins localised to opposite cell edges co-ordinate epithelial cell planar polarisation during development. Now, on , Strutt and Warrington report that PCP proteins control the site of hair production in developing Drosophila wings by regulating the localisation of the novel formin homology 3 domain protein Multiple Wing Hairs (Mwh). Each cell in the Drosophila wing blade has a single, distal hair that develops from an actin-rich prehair. In the absence of Mwh, the researchers report,actin bundles `sprout' across the entire apical surface of the wing cells rather than at the distal edge only, a result which suggests that Mwh represses actin filament formation. They also show that the proximally localised PCP protein Strabismus acts via the effector proteins Inturned,Fuzzy and Fritz to stabilise Mwh in the proximal region of the wing cells, and that the distally localised PCP protein Frizzled promotes prehair initiation. Together, these results suggest that both proximal and distal cues control prehair placement in Drosophila wings.
