Fig. 5

ErbB signaling inhibition improves central branch regrowth. (a) Diagram of ErbBi central branch axotomy (CBA) ablation paradigm. Larval zebrafish were preincubated with 4 ?m ErbB inhibitor AG-1478 in 1% DMSO (ErbBi CBA) or vehicle control (DMSO CBA). (b) Percent of dorsal root ganglia (DRG) with successful or unsuccessful central branch regrowth into the dorsal spinal cord following CBA with DMSO or ErbBi (n = 32 DRGs from 24 fish; Pearson's ?² test, p = .015). (c) In vivo, time-lapse imaging of a Tg(ngn1:gfp;sox10:nls-eos) DRG at 3 dpf under ErbBi conditions before (Pre-injury) and after CBA (?0 h post-injury, hpi) with fluorescently labeled sensory neuron (asterisk; new dorsal neurite indicated by arrow) and satellite glial cell SGC nuclei (white arrowheads). Spinal cord boundary indicated by dashed line. Single Z-plane inset indicated by square outline. (d) Comparison of the number of DRGs that exhibit either zero or one or more dorsal neurite outgrowths following CBA, under DMSO (white fill, 35% with one or more dorsal neurite outgrowths; n = 6/17 DRGs from 13 fish) or ErbBi (dark fill, 86% with one or more dorsal neurite outgrowths; n = 12/14 DRGs from 11 fish; Barnard's test, p = .0047) conditions. (e) Quantification of initiation time (hours post-injury [hpi]) of neurites that fail (light curve, mean: 3.32 ± 2.87 hpi) or successfully regrow into the dorsal spinal cord (dark curve, mean: 1.25 ± 2.45 hpi), pooled from both DMSO and ErbBi treatment conditions (n = 25 neurites from 19 DRGs from 13 fish; Wilcoxon test, p = .023). Dashed lines indicate mean initiation time. (f) Graph comparing SGC nuclear speed under DMSO (mean: 1.00 ± 0.27 a.u.) and ErbBi (mean: 0.85 ± 0.30 a.u.) treatment conditions (n = 68 cells from 29 DRGs from 19 fish; Wilcoxon test, p = .0040). Dashed line indicates mean; measures normalized to DMSO. Triangles indicate SGC nuclei from DRGs with successful regrowth of the central branch and circles represent SGC nuclei from DRGs that did not successfully regrow the central branch. (g) Circular plots of SGC nucleus angular position relative to the neuronal soma at initial and end timepoints from the ErBbi CBA (mean: Initial 297 ± 87°, End 337 ± 92°; Watson's U2 two-sample test, p > .05) condition. Dashed arrows indicate mean initial angular position, solid arrows indicate mean end angular position, shaded regions indicate ±1standard deviation, and star bursts indicate mean central axon angular position pre-injury. Scale bars: 10 ?m. nsp ?.05, *p < .05, **p ? .01