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. Author manuscript; available in PMC: 2013 Jun 1.
Published in final edited form as: Mol Cell Neurosci. 2012 Apr 26;50(2):193–200. doi: 10.1016/j.mcn.2012.04.007

Figure 3. PyX-induced sprouting of intact CST fibers in PlexinA2-/- mice.

Figure 3

Myelination appears normal in adult PlexinA2-/- mice. Photomicrographs of transverse cervical sections from intact adult wild type (A, B) and PlexinA2-/- mice (C, D) demonstrate myelin staining (myelin stain in green, MBP in red) to be indistinguishable between genotypes (compare A and C). High power photomicrographs show a normal pattern of MBP staining around axon profiles of lateral column white matter of PlexinA2-/- mice (D), identical to that of wild type mice (B). Photomicrographs of transverse sections of cervical spinal cord from adult wild type (G, H) and PlexinA2-/- mice (E, F, I, J). PKCγ-immunoreactivity reveals a normal faciculated dorsal CST (E, F) in intact PlexinA2-/- mice. BDA+ CST axons can be seen in the right ventrodorsal column, from which CST collaterals project unilaterally into both dorsal and ventral horns in sham lesioned wild type (G, H) and PlexinA2-/- mice (I, J). A few BDA+ CST axons cross the midline in both wild type and PlexinA2-/- mice without injury (Q). Unilateral PyX is confirmed in all experimental mice by the complete absence of PKCγ-immunoreactivity in the contralateral ventrodorsal column (K, L). PyX PlexinA2-/- mice illustrate robust sprouting of intact BDA+ CST axons into the deafferented side of the spinal cord (O, P). The average number of BDA+ CST axons crossing the midline is significantly greater in PlexinA2-/- compared to wild type controls (compare O and P to M and N, Q, * P<0.01, ANOVA). As another measure of CST innervation, fiber length per cross sectional area was measured throughout the spinal cord grey matter (R, S). Fiber length was significantly greater on the intact side after PyX in PlexinA2-/- mice compared to fiber length on the intact side in sham lesioned PlexinA2-/-, wild type and PyX wild type mice (R, * P<0.01, ANOVA). CST fiber length was also significantly greater on the injured side of PlexinA2-/- mice in comparison to fiber length on the injured side of sham lesioned PlexinA2-/-, wild type and PyX wild type mice (S, * P<0.01 ANOVA). Scale bars in A = 250 μm; B = 25 μm; F = 50 μm. All data are mean ± sem from separate mice.