Fig. 6. Sema5A function blockade and RGC axon pathfinding errors. (A) ECD-Fc-mediated retinal growth cone collapse on an L1 substratum in the presence of anti-Sema5A antibody or pre-immune serum. (B) The incidence of axon guidance errors in optic nerves treated with anti-Sema5A antibody. (C) A normal, DiI-labeled E14 optic nerve showing retinal axons contained within the retinal pathway. The retina and optic disc are towards the left. (D-F) Examples of axon guidance errors in anti-Sema5A-treated optic nerves. The retina is towards the left. (D) A mild phenotype: a pair of short axons tipped with growth cones (arrowheads) are straying from the optic nerve bundle. (E) A more severe error showing a bundle of axons (arrowhead) veering away from the main portion of the optic nerve. Note that some aberrantly projecting axons are growing parallel to the optic nerve (arrow). (F) A large fascicle of axons near the optic disc (arrowhead) have split away from the main optic nerve bundle, and terminate in a knot-like structure. (G,H) Examples of stray RGC axons within the retina (arrowheads). Unlike normal axons, stray axons fail to grow completely through the optic disc, and extend inappropriately within the retina. Scale bars: (C-H) 50 µm.