Wnt ligands are not required for planar cell polarity in theDrosophilawing or notum

Thefrizzled(fz) anddisheveled(dsh) genes are highly conserved members of the core planar cell polarity (PCP) pathway and of the Wnt signaling pathway. Given these dual functions, a number of studies have examined whether Wnt ligands may provide a global, tissue-scale orientation cue for PCP establishment during development, and these studies have reached differing conclusions. In this study, we re-examine this issue in theDrosophila melanogasterwing and notum using split-Gal4 co-expression analysis, systematic pairwise and triple somatic CRISPR-based knock-outs and double RNAi experiments. Pairwise loss-of-function experiments targetingwgtogether with other Wnt genes does not produce PCP defects, neither via somatic CRISPR nor RNAi. In addition, somatic knock-out ofevi(akawntless), which is required for the secretion of all Wnt ligands expressed in these tissues, did not produce detectable PCP phenotypes. Altogether, we were unable to find support for the hypothesis that Wnt ligands contribute to PCP signaling in theDrosophilawing or notum.