Protein fuzzy (or FUZ) is a planar cell polarity (PCP) effector that controls multiple cellular processes during development. PCP signalling is an evolutionarily conserved pathway by which directional information regarding polarized cell movement is provided to cells. The PCP signalling axis involves PCP core and PCP effector genes, which are activated consecutively to govern orientated cell migration and the establishment of cytoskeletal structures. Dishevelled (Dvl in mammals or Dsh in Drosophila) and Fuz (or fuzzy in Drosophila) are two representative PCP core and effector genes, respectively. PCP regulates mammalian nervous system development; Fuz-null mutant mice display neural tube defects due to failure of directional cell motility and cell fusion.