Wild-type (A-E), col4a6
rk18/rk18 (F-J), and col4a5
s510/s510 (K-O) mutant 5-dpf larvae harboring the pou4f3:Gal4, UAS:GAP-GFP transgene, which labels the axons of retinal ganglion cells (RGCs) in a mosaic manner, were stained with anti-Vglut1 (magenta) and anti-GFP (green) antibodies. Dorsal projection views (A-C, F-H, K-M) of the midbrain/hindbrain (A, F, K), left half of the rostral hindbrain (B, G, L), and half of the tectum (C, H, M). Lateral view of the tectum (D, I, N). Both col4a6 and col4a5 mutant larvae showed abnormal branching of the GC bundles (indicated by arrows, G, L). In wild type animals, each RGC projected to a single layer in the tectum (D), whereas in the col4a6 and col4a5 mutants some RGC axons trespassed between tectal layers (marked by arrows in I and N). (E, J, O) Schematic drawing of the RGC axons (lateral view). SO, stratum opticus; SFGS, stratum fibrosum et griseum superficiale. The statistic analysis is shown in S2 Table. Scale bars: 100 μm in K (applied to A, F); 20 μm in L (applied to B, G); 20 μm in M (applied to C, H); 20 μm in N (applied to D, I).