Frizzled2 receives the WntA morphogen during butterfly wing pattern formation

Abstract

AbstractButterfly color patterns provide visible and biodiverse phenotypic readouts of the patterning processes that occur in a developing epithelium. While the secreted ligand WntA was shown to instruct the color pattern formation in butterflies, its modes of reception and signal transduction remain elusive. Butterfly genomes encode four homologues of the Frizzled-family of Wnt receptors. Here we show that CRISPR mosaic knock-outs offrizzled2(fz2) phenocopy the color pattern effects ofWntAloss-of-function in multiple nymphalids. WhileWntAmosaic clones result in intermediate patterns of reduced size, consistently with a morphogen function,fz2clones are cell-autonomous. Shifts in pupal expression inWntAcrispants show thatWntAandfz2are under positive and negative feedback, respectively. Fz1 is required for Wnt-independent planar cell polarity (PCP) in the wing epithelium. Fz3 and Fz4 show phenotypes consistent with Wnt competitive-antagonist functions in vein formation (Fz3 and Fz4), wing margin specification (Fz3), and color patterning in the Discalis and Marginal Band Systems (Fz4). Overall, these data show that the WntA/Frizzled2 morphogen-receptor pair forms a signaling axis that instructs butterfly color patterning, and shed light on the functional diversity of insect Frizzled receptors.