The planar cell polarity (PCP) pathway orients cells within the plane of an epithelium during development. Experiments in Drosophila indicate that the core PCP proteins move to the apical cell membrane during the initiation of PCP and implicate the actin-severing protein cofilin in PCP initiation. Now, on , Kathyrn Anderson and colleagues report that cofilin 1 (Cfl1) and the core PCP protein Vangl2 cooperate to control PCP initiation in the mouse embryo. The researchers analyse two aspects of PCP - convergent extension of the axial midline and posterior positioning of nodal cilia. Both these aspects of PCP are nearly normal in Cfl1 and Vangl2 single mutants, they report, but midline extension fails completely and nodal cilia do not polarise in Vangl2 Cfl1 double mutants because PCP protein complexes fail to move to the apical cell membrane. These and other results suggest that remodelling of the actin cytoskeleton is required to traffic vesicles containing PCP proteins to the apical membrane during PCP initiation.
