Fig. 5

KLF7/MEF2 promotes axon sprouting around the lesion site, prevents retraction and promotes sprouting into proximal spinal cord grey matter (A) Quantification of sprouting at the lesion site for all groups. Axon counts at each distance were divided by the number of axons present at -3 mm (B) Average total growth (mm) per axon at the lesion site, calculated as the area under the curve in A. KLF7/MEF2 overexpression promoted significantly more sprouting compared with all other groups (linear model, F-test p = 0.002, with Tukey’s post-hoc tests). (C) In many animals we saw substantial retraction of dorsal column axons after the lesion. Shown here is an example of a cluster of end bulbs of retracting GFP-labelled fibres, over 5 mm caudal to the lesion. The centres of such clusters were used to define the retraction distance (white dashed line). (D) Quantification of axon retraction in all groups. 0.0 mm represents the caudal lesion edge defined by GFAP staining. Average axon retraction distance was significantly less in the KLF7/MEF2 group than in the GFP group (p < 0.05; linear model with F-test and Dunnett’s post-hoc test with GFP as control). (E) Total labelled axon counts of the intact region of the dorsal column, defined as the area caudal to the retracting axons. No significant differences were found between groups in the numbers of CTB/ GFP positive (double-labelled) axons, or of GFP positive axons (right). (F) An example of GFP and CTB labelled axons (arrowhead) in the dorsal column (DC) leaving the main tract and entering the grey matter of the spinal cord at T8 in the region of Clarke’s column. (green: GFP, red: CTB). G, H. Example of tracing of axon collaterals in the thoracic spinal grey matter by the Neuromath software. G shows immunohistochemistry of GFP-positive axons and H shows the traced axons identified by Neuromath. I. Log of average traced collateral length, normalised to total GFP positive axon counts in the dorsal column. ATF3/KLF7/MEF2 and KLF7/MEF2 overexpression promoted significantly more sprouting than GFP (linear model with F-test and Dunnett’s post-hoc test with correction for heteroscedasticity; F-test p < 0.01). * p < 0.05 ** p < 0.01 for post-hoc tests. n = 8 for No TF, MEF2; n = 9 for other groups. Scale bars: C: 200 μm; F: 50 μm (applies to F, G,H)