Fig. 2. Otk is highly enriched in R1-R6 growth cones. Third-instar eye–brain complexes were double-stained with MAb 24B10 (green) and anti-Otk antibody (red). In a wild type optic lobe (A-C), anti-Otk immunoreactivity was detected in both lamina and medulla. The strongest staining was detected in the lamina plexus, consisting mainly of R1-R6 growth cones at this developmental stage. In an otk³ eye-specific mosaic individual in which most R-cell axons were otk³ mutant axons (D-F), anti-Otk immunoreactivity was largely absent in the lamina plexus. Scale bar: 20 µm.