The failure of axon regeneration in the central nervous system (CNS) prevents treatment of a wide range of CNS afflictions, including spinal cord injury, stroke, and diseases like Parkinson's. One major reason that regeneration fails is that many CNS undergo a developmental loss in their intrinsic capacity for axon growth. To restore function after CNS injury or disease it is essential that we devise means to enhance the intrinsic growth state of CNS neurons. We recently identified the Kr?ppel-like family of transcription factors (KLFs) as key regulators of intrinsic regenerative capacity in CNS neurons. Critically, a transcriptionally active mutant, VP16-KLF7, promotes axon regeneration by injured corticospinal tract (CST) neurons, an important therapeutic target. Robust regenerative responses were achieved using viral delivery to adult wild-type animals, raising potential clinical relevance for this novel pro-regenerative tool. To further explore the potential of KLF7 activity t promote CNS regeneration, three key questions must be addressed, corresponding to our aims. First because recovery from SCI depends on multiple functional modalities carried by diverse fiber tracts, we will use viral-mediated gene delivery to test the ability of VP16-KLF7 to promote regeneration in additional neuronal populations. Targeting additional neuronal subtypes has the potential to broaden the range of behavioral improvement after SCI. Second, we will examine the expression of pro-regenerative genes in neurons stimulated by VP16-KLF7 in order to determine the potential relationship between with known pro-regenerative (e.g. mTOR, CNTF) or anti-regenerative (e.g. chondroitin sulfate proteoglycan (CSPG)) pathways and signals. Based on this information we will rationally combine VP16/KLF7 with viral particles that target complementary pathways, potentially inducing additive or synergistic improvements in axon regeneration. Finally, we will examine the extent to which KLF7-stimulated axons succeed in forming functional synapses on appropriate target cells and ultimately contribute to functional recovery. Using viral gene delivery we will co-express VP16- KLF7 with optogenetic constructs that enable the treated neurons to be reversibly activated or silenced. This technique will allow us to determine the specific contribution of the treated neurons to electrophysiological and behavioral output as regeneration proceeds. Taken together, these experiments have a strong potential to extend the use of a promising new pro-regenerative tool and lead to the development of novel combinatorial methods to promote axon regeneration and functional recovery in the injured CNS, leading to novel treatment options for people suffering from CNS afflictions.
A major challenge to treating injuries to the brain and spinal cord is that once severed, the axonal processes that carry information in the nervous system are unable to regrow. Using a rodent model of spinal cord injury we are testing a new gene therapy approach to restore connection and function across the injury site.
