Fig. 1

Expression pattern of Rtn4b in the zebrafish retina and optic nerve. Cross sections of the zebrafish retina normal (A) and 10 days after ONS (B,C) were exposed to ABs against Rtn4b (A,B) and MBP (C). Weak Rtn4b staining is seen across all retinal layers including RGCs (white arrow) in the normal retina (A). RGCs robustly upregulate Rtn4b 10 days after ONS (B). The RGC axons in the retina on top of the RGCs (bracket) are also weakly labeled but are more intensely stained by the AB against MBP (C). Scale bar, 50 µm. Cross sections through the normal zebrafish optic nerve (D,E,F) show very weak labeling with Rtn4b AB (D). (E) Rtn4a AB stains across the normal nerve similar to MBP. Labeling with the MBP AB is strong in the normal nerve (F) as well as at 10 days after ONS (M). Scale bar, 10 µm. Rtn4b AB in nerves at 10 days after ONS (G,I) labels portions of RGC axons identified as axonal (rather than glial) by the AB against neurolin (H). (I), overlay. Scale bar, 20 µm. (J) Rtn4a AB in the10-days ONS nerve stains, in particular, the boundaries of fascicles and subdivisions of the fascicles. (K,L) The neurolin-positive regenerating RGC axons are not labeled with Rtn4a to any significant extent, in contrast to Rtn4b labeling (I). (M) MBP staining is intense in the 10-day ONS nerve. (N,O) Neurolin-positive regenerating RGC axons are located amidst the myelin. Boxed areas in (I,L,O) are enlarged in (P,Q,R). Arrows point to neurolin-positive axons which are also Rtn4b AB-positive (P), but seem not significantly co-localized with Rtn4a (Q), and lie amidst the MBP labeling of myelin (R). Scale bar, 10 µm.