VRC: Develop regenerative therapies for neurological vision loss

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Abstract We propose to promote long-distance axon regeneration of injured optic nerve or tract and recovery of visual function in adult mammals by enhancing intrinsic growth capacity and growth cone dynamics of mature neurons. We will study whether inhibiting let-7 and/or upregulating its suppressors lin28 and lin41 in retinal cells promotes robust axon regeneration and functional recovery in adult mammals with optic axon injury. We will also study whether upregulating cytoskeletal TACC3 protein stimulates dramatic axon regeneration by targeting growth cones directly. CNS neurons lose the ability to regenerate axons with age, and this limits functional recovery after injury. Many genes have been identified to control the growth ability of mature neurons, but none have been translated to clinical use. The best targets are probably those with the potential to impact multiple genes simultaneously. Among them, let-7 miRNA seems important for regulating age- dependent decline in axon regeneration. We propose to enhance the growth capacity of mature neurons by targeting the lin28/let-7/lin41 pathway. Because dystrophic growth cones in axotomized CNS contribute to axon regeneration failure, we also propose to enhance cytoskeletal growth dynamics by upregulating the TACC3 gene. We hypothesize that the let-7 pathway regulates axon regeneration in mammalians and that targeting this pathway plus the cytoskeletal TACC3 gene stimulates robust axon regeneration and functional recovery of visual pathways. Using the novel AAV vectors developed in the PI’s lab, we will determine whether inhibiting let-7 and/or upregulating lin28, lin41, or TACC3 in retinal cells promotes robust axon regeneration and functional recovery in adult rodents with optic nerve or tract injury. Aim 1 proposes to study whether intravitreal injections of the individual or combined viral vectors for let-7 inhibitor, lin28, or lin41 enhance optic axon regeneration, retinal ganglion cells survival, and functional recovery in adult mice. In Aim 2, we will use our AAV vectors to study whether upregulating TACC3 stimulates dramatic axon regeneration and whether combination therapies targeting both let-7 and TACC3 signals yield better axon regeneration and functional recovery in adult rodents with optic axon injury than either individual approach. Use of our unique viral vectors has the potential not only to provide important new insights into the molecular control of growth in mature CNS neurons, but also to develop practical and effective strategies to promote axon regeneration and functional recovery in mammals. Our experiments with combined strategies to target both somatic neuronal program and growth cone cytoskeletal dynamics should stimulate further axon regeneration and functional recovery. We thus anticipate identifying extremely promising regenerative strategies in adult mammals. Our viral vectors, which are administered post-injury, can be applied to multiple axon tracts and readily translated into clinical trials. The success of this project may reverse the visual functional deficits, improve the quality of life in many patients, and reduce the financial burdens to patients, families, and the public.