lh3 directs the initial regrowing RGC axons. (A) Schematic of zebrafish larvae expressing Tg(isl2b:GFP) to label RGCs that were used for in vivo imaging. Larvae have one eye removed 1 day before timelapse imaging. The region outlined is shown in B-K. (B,G) Transected RGC axons in lh3 sibling (B) and lh3 mutant (G) larvae separate from the distal region of the optic nerve that will eventually degenerate (indicated by brackets in B-D,G-I). (C) In lh3 siblings, RGC axons initiate growth out from the proximal stump (white arrowhead). (D-F) A small group of axons (white arrowhead) in lh3 siblings projects directly toward the midline along the original path of the projection (D) and then subsequently additional axonal growth follows (E, white arrowhead, F) (n=7/10 nerves). (H-K) In lh3 mutants, axons grow out from the proximal stump (H), but persist along aberrant trajectories (I-K, magenta arrowheads; n=6/12 nerves). See also Fig. S1. Dashed lines indicate the outline of the eyes. Scale bar: 25 µm.
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