These asymmetries are thought to act as cues interpreted by downstream effector genes for the establishment of polarity dependent structures. In particular, each wing cell initiates the growth of a single trichome, an actin and tubulin rich wing hair at the Carmustine distal vertex at around 30 hrs after puparium formation. About 17 hrs later, the trichome has developed into a cuticle ensheathed, rose-thorn shaped spike filled with a highly organized actin and microtubule fibers that points towards the distal wing tip. In core PCP mutants, a wing hair typically forms in the center of a cell and shows aberrant polarity. Planar cell polarity effector genes, such as inturned, fuzzy, and fritz, act downstream of the core PCP genes. In contrast to core PCP mutants, in PPE mutant wings, an average of two independent trichomes are initiated at various positions in the apical periphery of a wing cell phenotype. A distinct phenotype with four hairs per cell is seen in multiple wing hair mutants, some of which appear to be smaller secondary hairs splitting from larger ones. Epistasis analyses and colocalization studies suggest that a complex of In, Frtz, and Fy localizes to proximal, apical cell vertices in a core PCP gene dependent manner and prevents local hair initiation and/or promotes distal hair initiation. Specifically, PCP effector genes recruit and/or activate Mwh via direct interaction with In leading to proximal enrichment of Mwh trailing off towards the distal end of cells. mwh encodes a protein that resembles Pramipexole formins in that it contains a Rho family GTPase binding domain followed by a formin homology 3 domain with a potential for dimerization, but lacks a FH2 domain able to catalyze actin polymerization. Mwh may inhibit ectopic actin filament formation either directly, or by interfering with Rho GTPase activation of formins, or formin mediated actin polymerization. Consistent with this, growing actin pimples are initially seen all over the apical surface of a mwh mutant wing cell. At around 34 hrs APF, Mwh relocalizes to the base of the forming prehair, where it prevents the formation of secondary trichomes.