Fig. 5. Intraretinal axonal phenotype caused by RCAS-Irx4 virus infection, viewed at lower magnification. The retinas were infected at stage 10-11 and harvested at E7 (A-D) or E12 (E,F). Axons were stained with an anti-neurofilament antibody (A,C,E,F), whereas the infected area was visualized by staining with an anti-viral GAG antibody (p27) (B,D). Images in A,C are in the same fields as in B,D, respectively. The broken white arrows in A,C,E,F indicate the direction of axon projection towards the optic disc. Note the axons turned to avoid the infected area (marked with IF in A,C). However, the area that exhibited phenotype was smaller than the infected area. Some newly infected areas with only scattered infection (marked with and asterisk in A-D) did not show axonal abnormality. (E) At E12, the retina was completely infected with the RCAS-Irx4 virus (data not shown); however, the area with the phenotype did not expand to the entire retina. Some areas still appeared normal (marked with an asterisk), indicating that axons no longer responded to low Slit1 levels after they had passed through the area. (F) The axons in the control virus RCAS-GFP-infected retina appeared completely normal at E12. Scale bar: 200 µm.