Fig. 4. Ptc can alter Sxl subcellular location. (A-F) Embryos expressing different Ptc variants stained for Sxl (green, A-F), and propidium iodide (PI; red) merged with Sxl (A'-F'). (A') Sxl is primarily nuclear in wild-type (wt) embryos. Ptc⁺ (B') and Ptc^Loop2 (F') do not completely titrate Sxl out of the nucleus giving a diffuse image; the PI signal is yellow to orange. (C') Ptc^D584N resembles the wild type and Sxl is more distinctly nuclear. (D',E') Ptc^1130X and the carboxyl half of Ptc, PtcC, strongly titrate Sxl out of the nucleus; the PI signal is more red. (G-L) Effects of Ptc variants on Hh signaling in embryos reported by full-length Ci (red) and Wg (blue) expression. Relative to wt (G), Ci levels are increased by the expression of Ptc^D584N (I) and PtcC (K), decreased by Ptc⁺ (H) and Ptc^Loop2 (L). The increase caused by Ptc^1130X (J) is very modest. Wg expression is depressed by Ptc⁺ and Ptc^Loop2 (H' and L'; arrowheads mark disrupted Wg stripe), elevated by PtcC (K') and modestly elevated by Ptc^D584N (I'). The feedback between Ci and Wg (Lessing and Nusse, 1998) appears most affected by Ptc^1130X and Wg levels are not strongly elevated (J'). This is more evident as the embryos get older and the Wg levels drop. Embryos scanned at similar settings with a 40x objective. Bars, 20 µm.