Wnt ligands are not required for planar cell polarity in the Drosophila wing or notum

The () and () 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 the wing 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 targeting together with other Wnt genes does not produce PCP defects, neither via somatic CRISPR nor RNAi. In addition, somatic knock-out of (aka ), 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 the wing or notum.