3D Visualization and Investigation of Retinal Axon Regeneration Poor regeneration of retinal ganglion cell (RGC) axons is a major obstacle for treating ocular trauma and optic neuropathies. There are yet no therapies to repair damaged optic nerve. Our previous studies have demonstrated that modulation of distinct genes promotes long distance regeneration of some RGC axons in adult mice. However, promoting axons not only to regenerate into the lesion, but to travel long distances, and to reconnect with their central targets is still a major challenge. In fact, we and others have reported that only a few axons reinnervate the brain. It is unclear what cellular and molecular factors contribute to the limited pathfinding, and the lack of target re-innervation. The overall goal of this proposal is to; i) identify effective approaches that promote regeneration and reconnection of RGC axons, ii) optimize three dimensional imaging techniques to examine subtype-specific regeneration, and iii) assess the genes that are regulated by the regenerative- promoting factors using single nucleus RNA sequencing. Identifying strategies to further increase regeneration and re-innervation in the brain represents critical future studies. Results obtained from these studies will provide invaluable information on developing future therapies to repair degenerated optic nerve after trauma or in diseases.