Fig. 3

Fig. 3 Timing of DRG ray innervation and maturation during caudal fin development. (A-E) Confocal projections of caudal fins fixed at the indicated stages expressing transgenic markers for osteoblasts [Tg(sp7:mCherry-NTR)] and endothelium [Tg(fli1a:EGFP)] and immunostained for axons (acetylated tubulin antibody). ‘Zoom’ images are cropped, enlarged regions of merged images. Dotted lines denote caudal fin margins. The yellow arrowhead in C denotes the future position of the hypural diastema (HD). New rays are added symmetrically on either side of the HD. Double-headed arrows in the inset in C denote the bilateral, symmetrical pattern of innervation. Note the axons on the inner surface of each hemiray in the slice panel. The yellow arrows in D denote that the dorsal-most and ventral-most ray-associated axons originate along separate routes than the inner ray-associated axons. White arrowheads indicate the position of lateral line (LL) axons growing into the caudal fin in the inter-ray space. (F,G) Quantification of the number of innervated bony rays versus standard length (F) and notochord flexion angle (G). (H) Schematic illustrating the three posterior ganglia of the developing trunk, with DRG₍₀₎ (magenta) demarcating the most posterior cluster, DRG₍₋₁₎ marking the second most posterior cluster (purple) and DRG₍₋₂₎ marking the third most posterior cluster (blue). (I,J) Confocal projections of fish expressing neural crest lineage [sox10: Tg(Mmu.Sox10-Mmu.Fos:Cre);Tg(actb2:LOXP-BFP-LOXP-DsRed)] and sensory channel [TgBAC(trpa1b:EGFP)] reporters. Arrowheads indicate DRGs color-coded as in H. Arrows indicate trpa1b⁺ DRG soma. (K) Scatterplots with linear regression lines showing quantification of trpa1b⁺ soma (arrows in J) in each of the three posterior-most ganglia relative to standard length. Scale bars: 200 μm (A-E); 10 μm (inset in C); 50 μm (A-E zoom panels; I,J).