Fig. 3.

Loss of Fas2 disrupts R-cell axon–axon association. (A) Wild type. (B) In mutants defective in Sema1a reverse signaling [e.g., sema1a^P1/Df(2L)BSC204], R-cell axons displayed defects in axon–axon attraction, leading to the appearance of many gaps (more than three; arrows) at the lamina intermediate target region. (C) In Fas2 null mutant (i.e., Fas2^EB112) eye-specific mosaic animals, gaps (arrows) at the lamina target region were frequently observed. (D) In Fas2 eye-specific knockdown animals, similar disruption at the lamina target region was observed. The arrows indicate gaps at the lamina termination layer. la, lamina; me, medulla. (Scale bar, 20 μm.)