Fig. 5. The formation of plexiform layers and the differentiation of photoreceptors depends on shh signaling. All images are confocal sections of the retina, with anterior to the top. (A) F-actin staining in a wild-type retina at 50 hpf. Note the prominent staining of the inner and outer plexiform layers. (B) F-actin staining in a shh^–/– retina at 50 hpf. Note the complete absence of plexiform layer formation. (C) Zpr1 protein in a wild-type retina at 72 hpf. Note the staining in cones of the ONL. (D) Zpr1 protein in a shh^–/– retina at 72 hpf. Note the severely reduced number of cells expressing Zpr1, which are present in a ventronasal patch. (E) Zpr3 protein in a wild-type retina at 72 hpf. Note the staining in rods of the ONL. (F) Zpr3 protein in a shh^–/– embryo at 72 hpf. Note the reduced cell number, as observed with Zpr1 (E).