Binds to the Wnt signaling protein wg, stabilizes it and promotes its extracellular distribution. This is required for establishment of a wg gradient during development to allow for regulation of target genes at different levels. Interacts (in heparan sulfate-bound form) with wg. In the wing disk, detected throughout the disk where it is localized primarily to the apical surface but is also present at the basal surface (at protein level). Contains heparan sulfate O-linked oligosaccharides. Predominantly embryonic lethal with 50% of embryos dying before cuticle formation and 10% showing a weak denticle belt fusion phenotype. RNAi-mediated knockdown in the developing wing results in development of ectopic chemosensory bristles along or near the wing margin on both the anterior and posterior sides.