Fig. 5. Ptc is required for Hh-promoted Sxl nuclear entry. (A-F) Sxl nuclear levels are reduced in ptc^– clones: (A-C) ptc¹⁶ clones as marked by En expression (red, A) show decreased nuclear Sxl (green, B); merged image (C). Arrowhead marks where Sxl is nuclear between ptc negative clones. Scale bar: 20 µm. (D-F) ptc^S2 clones marked by lack of ß-gal expression (red, D) show decreased nuclear Sxl (green, panel E); merged image (F). Arrowhead marks where nuclear Sxl is absent between ptc negative clones with this amorphic allele that is capable of binding to Hh. (G-I) PtcD584N expressed in dorsal compartment of wing disc using the apterousGAL4 driver. Full-length Ci (red, G) and Sxl (green, H) and merged image (I). Note the weak signal of Sxl in the anterior dorsal compartment in both the wing pouch as well as notum because of decreased nuclear levels of the protein. Arrowhead points to the AP and dorsal/ventral boundary meeting point. The arrow indicates the overgrowth of disc in the anterior compartment as a result of the dominant negative effect of the PtcD584N protein. Scale bar: 40 µm. (J-L) ptc¹⁶ clones in a hh^MRT background stained for Ci (J), Sxl (K). (L) Merged image of J and K. Image is of the anterior region distant from the AP boundary of an overgrown disc. Large arrowhead marks region of lower Ci levels more posterior to region that has ectopic Hh, which is reported by the presence of full-length Ci (arrow). Note the brighter punctate signal for Sxl marking higher nuclear levels where there is an increase in levels of full-length Ci. ptc^– clones have lowered levels of Ci (some of the clones, which are round, are marked by small arrowheads) because of the induction of en which inhibits Ci transcription. As seen for ptc¹⁶-only clones, the levels of nuclear Sxl within the clones is lowered. Scale bar: 20 µm. All are confocal images; anterior is to the left, ventral at the top.