Multicellular Mechanisms Driving Axon Regeneration

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ABSTRACT Permanent disabilities following central nervous system (CNS) injuries result from the failure of injured axons to re-build functional connections. There are currently no therapies to restore mobility and sensation following spinal cord injury or vision after optic nerve damage. The poor intrinsic regenerative capacity of mature CNS neurons is a major contributor to the regeneration failure and remains a major problem in neurobiology. In contrast, peripheral sensory neurons successfully switch to a regenerative state after axon injury. The long-term goal of my research program is to understand the multicellular mechanisms by which injured sensory neurons activate a pro-regenerative program and identify potential targets for future treatment of CNS injuries. Activation of an axon growth program relies in part on the expression of regeneration-associated genes. Because individual gene based approaches have yielded limited success in axon regeneration, we are focusing on epigenomic regulations, which affect globally, yet specifically a combination of multiple genes. Our goal is to uncover how the epigenetic landscape is re-organized in the context of axon injury to enable axon repair. These studies will incorporate cell-type specific epigenomic analyses to study the transcriptional and chromatin conformation changes elicited by peripheral and central axon injury. Axon regeneration is not cell autonomous and is influenced by the environment at the level of the axon injury site and at the level of the cell soma. We have recently discovered that satellite glial cells, the main type of glial cells in sensory ganglia respond to axon injury and contribute to the repair process. We propose to use powerful combinations of tools to pursue an innovative line of research aimed at dissecting the multicellular mechanisms orchestrating axon regeneration and build upon these findings to improve regeneration in CNS models. To achieve this goal, we will determine the intrinsic neuronal mechanisms controlling axon regeneration, focusing on epigenomics studies. We will elucidate the contribution of the microenvironment surrounding neuronal soma to the axon regeneration process, including satellite glial cells and other non-neuronal cells. To determine if findings made in the mouse model system are predictive of human physiology, we will determine the molecular profile of human cells surrounding sensory neurons. Finally we propose to manipulate novel pathways we discover to improve regeneration in two CNS models, spinal cord injury and optic nerve injury. This proposal will use powerful combinations of tools to pursue an innovative line of research aimed at dissecting the multicellular mechanisms orchestrating axon regeneration and build upon these findings to improve regeneration in CNS models.