Fig. 2. Glypicans are required for Wingless activity in embryos. (A-D) Expression of rhomboid in various mutant embryos at about stage 13. (A) Expression of rhomboid in wingless mutants is characterised by a `tramtrack pattern' (this is seen in all embryos, n=100). (B) No such pattern is seen in hedgehog mutants, which express rhomboid in broadened stripes compared with wild type (stripes become occasionally split as shown on the right hand side). (C) In wingless hedgehog mutants, rhomboid stripes collapse into ventral rings (this is true for most segments in all embryos, n=53). Such rings are never seen in wingless mutants, n=100, and rarely so in hedgehog mutants (12% of hedgehog mutants have one or two ventral rings, none have more n=25). (D) The phenotype of embryos lacking maternal and zygotic dally and dlp is similar to - though slightly more variable than - that of wingless hedgehog mutants (a majority of abdominal rhomboid stripes collapse into rings in 69% of embryos and all embryos have at least one collapsed stripe, n=26). (E) Cuticle phenotype of wingless hedgehog double mutant. The epidermis is covered with denticles (the lawn phenotype) and two mid-ventral `whorls' can be seen (arrows). Whorls are sometimes seen in hedgehog mutants but not in the mid-ventral region. (F) The phenotype of embryos lacking maternal and zygotic dally and dlp is similar although more variable with fewer less marked mid-ventral whorls. This suggests that weak residual signalling could occur in the absence of the glypicans.