Fig. 8. Apoptosis was increased at the sites of axon crossing-over. E10 retinas infected with RCAS-Zic3 were analyzed by TUNEL assay (A,D-F), followed by staining with anti-neurofilament (B) and anti-viral GAG (P27) antibodies (C). At the sites with axon crossing-over (arrows in B), there was an increase in the number of apoptotic cells (arrows in A) and intensity of anti-viral GAG staining (arrows in C). Note that the adjacent area was also completely infected (marked with *), and some of the fluorescent signals were blocked by the DAB precipitates from the TUNEL assay. In addition, the apoptotic cells tended to concentrate at the photoreceptor side, not the ganglion side (A,D-F). PR, photoreceptor layer; G, ganglion cell layer. Scale bar: 50 µm.