Fig. 7. Additional defects caused by the repression of Shh signal transduction in C-RGCs. Confocal images of the optic nerve (A-C) or chiasm (D-F) from EGFP (C,F) or EGFP/Ptc1^loop2 (A,B,D,E) transfected mouse embryos at E16.5. In EGFP/Ptc1^loop2-positive embryos, a few fibres leave the nerve (A,B, arrow), project to the ipsilateral optic pathway (D, arrows), form tangles (E, white arrow) or turn back (E, yellow arrows). The boxed region in A indicates the location of the high-magnification image shown in B. (G,H) Schematic view of the behaviour of visual axons in control (G) and EGFP/Ptc1^loop2-transduced (H) C-RGCs. C-RGC axons are in green, I-RGC axons in red. Blockade of Shh signal transduction causes aberrant intraretinal growth (1,2), abnormal optic nerve (3) or chiasm/tract (4,5) turnings of C-RGCs axons. oc, optic chiasm; on, optic nerve. Scale bar: 200 µm in A; 155 µm in B-F.