In vivo , inhibition of GSK3β via Ser9 phosphorylation is dispensable for gain of axonal regeneration capacity. (A) Quantification of neurite outgrowth, measured as the percentage of neurons with the longest axon within each range (<75 μm, 75 to 250 μm, or ≥250 μm), of naïve and conditioned (CL) DRG neurons from either WT or GSK3βSer9Ala KI mice (KI); (n = 29 to 100). (B) Representative images of CT-B + fibers in sagittal spinal cord sections following SCI (left panels) or conditioning lesion (right panels) in WT (upper panels) and GSK3βSer9Ala KI mice (lower panels). r: rostral; c: caudal; d: dorsal; v: ventral; arrowheads highlight axons regenerating rostrally to the SCI site. Dashed lines label the border of the glial scar. Scale bar: 50 μm. (C) Quantification of the number of CT-B + dorsal column fibers able to enter the glial scar; (n = 4 to 6). (D) Quantification of the longest distance of regeneration of CT-B + dorsal column fibers scored from the border of the lesion; (n = 4 to 6). (E) Quantification of P-GSK3βTyr216 in relation to total GSK3β, as assessed by western blot, in either WT or GSK3βSer9Ala KI mice subjected to SCI (WT SCI or KI SCI) or conditioning lesion (WT CL or KI CL). Results are presented as a percentage of the SCI condition. (F) Quantification of P-CRMP-2 in relation to total CRMP-2, as assessed by western blot, in either WT or GSK3βSer9Ala KI mice subjected to SCI (WT SCI or KI SCI) or conditioning lesion (WT CL or KI CL); (n = 3 to 4). Results are presented as a percentage of the SCI condition. All error bars are SEM. *P <0.05. **P <0.01. ***P <0.001. Two-tailed Student’s t test. CRMP-2, collapsin response mediator protein 2; DRG, dorsal root ganglia; GSK3β, glycogen synthase kinase 3β; SCI, spinal cord injury; SEM, standard error of the mean; WT, wild type.