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Fig. 8 Effects of cyclopamine treatment on Hedgehog pathway activity and ath5 expression. (A,B) Expression of patched1 (ptc1), a target of the Hh signaling pathway, reveals tissues in which the Hh pathway is active. Treatment from 25-41 hpf with cyclopamine (B), but not vehicle (A), drastically reduced or abolished the ptc1 signal (blue stain), indicating effective blockade of Hh signaling. Expression of patched2 was similarly affected (not shown). (C-E) Blockade of Hh signaling at 13 hpf, but not 25 hpf, delays the ath5 wave. Larvae treated with cyclopamine from 13-50 hpf (D) show ath5 expression by temporal retinoblasts (arrowheads), much like a 41 hpf wild type (Fig. 6C) or 50 hpf syu mutant (Fig. 6H). In vehicle-treated larvae (C), as well as larvae treated with cyclopamine from 25-50 hpf (E), the wave is over and ath5 expression is confined to the ciliary marginal zone (arrows). Anterior/nasal is left and dorsal up in all photos. CMZ, ciliary marginal zone; cycl., cyclopamine; veh., vehicle. Scale bar: 25 µm for C-E.