(e,f) Images of BDA-labeled CST axons are from 6 serial sagittal cryosections spaced 280m apart superimposed over GFAP astroglial and NG2 staining at the center of injury

(e,f) Images of BDA-labeled CST axons are from 6 serial sagittal cryosections spaced 280m apart superimposed over GFAP astroglial and NG2 staining at the center of injury. of the main CST immediately rostral to the lesion (C3CC5), as a second dorsal column lesion at C3 reduces the functional recovery to control levels. Anatomical analyses showed significantly increased collateral sprouting of CST above and below the C5 injury and with pre-synaptic puncta in these axon sprouts. Using an optogenetic approach, we monitored the output map of the motor cortex, We found that, immediately after C5 dorsal column lesion, forelimb elbow flexion can be activated by a much larger cortical area, whereas forelimb extension was lost. Over time, the area that activates forelimb flexion reduced back to the original size and a new area, which used to activate the hind limb, was recruited to activate forelimb extension. After the second lesion at C3, the control of forelimb flexion was lost but that of the new control of the forelimb extension was largely unaffected. In cKO, these changes are more gradual and persistent. Finally, mice that did not undergo weekly behavioral testing displayed only limited skilled forelimb recovery with performance similar to that of mice tested at one week after injury. In the absence of weekly testing, refinement of cortical motor maps was also impaired, irrespective of Ryk conditional deletion, highlighting the importance of targeted plasticity. We demonstrate here that the cortical motor map undergoes dramatic changes to achieve recovery and this reorganization requires continued task-specific training. We also show genetic evidence demonstrating Wnt signaling as important regulator of axon plasticity in adult spinal cord using conditional knockout. Additionally, we demonstrate that a Ryk monoclonal antibody can Rabbit Polyclonal to IP3R1 (phospho-Ser1764) be a therapeutic tool as blocking Ryk function after lesion leads to improved functional recovery. A large proportion of patients have incomplete spinal cord injuries, providing a substrate for recovery. Our work illustrates that promoting circuit plasticity is a promising approach to restore function. RESULTS enhances recovery of fine motor control after SCI Mice underwent two weeks of training for the reaching and grasping task, followed by a C5 dorsal column spinal cord lesion: a partial spinal cord injury model leaving the dorsal gray matter, lateral white matter and the entire ventral spinal cord intact (Fig. 1a, d). Immediately after dorsal column lesion, forelimb reaching and grasping function is lost (Fig. 1f). With continued training, the success rate of sugar pellet retrieval recovers due to reconfiguration of neural circuits5. It has been shown that the CST undergoes robust collateral sprouting after injury and some of the GNE-317 new sprouts are thought be responsible for new functional circuits10C13. However, axon sprouting is inhibited by molecular cues that limit axon plasticity14,15. Open in a separate window Figure 1 conditional deletion enhances motor function recovery from spinal cord injury(a) Timeline outlining experimental details of bilateral cervical level 5 (C5) dorsal column lesion. (bCc) Generation of conditional allele. (b) Exons 3C6 were flanked with loxP sites. (c) Western blot of postnatal day 7 motor cortex extract from mice infected at postnatal day 0 with AAV2/1 synapsin Cre. Full-length blot presented in Supplementary Fig. 8. (dCe) Schematic showing the level of the C5 lesion in relation to motor neuron pools for distinct forelimb muscle GNE-317 groups (adapted from McKenna, Prusky, and Whishaw, 200033). (f) Behavioral performance on forelimb reach skilled food-pellet retrieval task shows enhanced recovery after conditional deletion in bilateral motor cortex (n=25 mice (control), 17 mice (cKO), from 21 litters, repeated measures ANOVA P=0.0003, F(1,40)=16.0102). Data presented as means.e.m. Members of the Wnt glycoprotein family are phylogenetically conserved axon guidance molecules that direct the growth along the rostro-caudal axis of both ascending sensory axons and descending CST axons during development6,16. The repulsive Wnt receptor, Ryk, which mediates Wnt repulsion of the developing CST neurons is either not expressed in normal adult motor cortex and the CST neurons or expressed at extremely low levels to be detected by hybridization GNE-317 or immunohistochemistry15. Spinal cord injury re-induces expression of GNE-317 Ryk mRNA and protein in the injured CST. By.