Among the genes implicated in this net movement of cells, known as convergent extension, are 2 asymmetric molecular systems that control PCP behaviour, the “core” genes and the “Fat-Dachsous” PCP system [261, 262]. The “core” genes give rise to multipass transmembrane proteins: Frizzled (Fzd-3, -6, and -7), Van Gogh (Vangl-1 and -2), Flamingo (Celsr-1, -2, and -3), and cytosolic components, Dishevelled (Dvl-1, -2, and -3), Diego (Inversin), and Prickle (Pk-1 and -2) . The Fat-Dachsous (Ft-Ds) pathway includes the large protocadherins Ft and Ds, acting as its ligand, and Four-jointed (Fj) as a Golgi resident transmembrane kinase . Downstream of the PCP system are PPE (Planar Polarity Effector) genes: Inturned (In), Fritz (Frtz), and Fuzzy (Fy) [265, 266]. The Multiple Wing Hairs (mwh) act downstream of both PCP and PPE  with Wnt4, Wnt5a, Wnt7a, and Wnt11 as regulators .