PROJECT SUMMARY The retinal pigment epithelium (RPE) is an essential monolayer that lies between the retina and the choroid and supports the function and integrity of the retinal photoreceptors. The RPE maintains tissue homeostasis in the adult mainly via long-term survival instead of cell turnover. Degeneration and atrophy of the central RPE causes the detrimental chronic disease age-related macular degeneration (AMD), which is the leading cause of blindness in the elderly population. A possibility for treating dry AMD in the future is by stimulating endogenous RPE regeneration, but little is known about the mechanisms that can drive RPE regeneration in vivo. One candidate pathway is the Hippo signaling pathway, as it plays a role in regulating cell proliferation and regeneration in many tissues and is also required in the developing RPE for cell fate specification. In developmental studies, we and others have discovered that Neurofibromin 2 (NF2) is critical for balancing RPE growth and proliferation. My preliminary data suggests that modulation of Hippo signaling through Nf2 disruption in the adult stimulates proliferation and differentiation of the RPE following injury. This proposal aims to determine how genetic manipulation of Hippo signaling promotes an intrinsic proliferative and regenerative response in the mammalian RPE. In Aim 1, I will characterize the role of NF2 in promoting RPE regeneration after injury in the adult. I have established an injury paradigm, in which I chemically injure the RPE of mice. Regeneration will be assessed on a cellular level by expression, co-localization, and quantification of RPE and proliferative markers, and on a functional level by electroretinography. In Aim 2, I will determine the mechanism by which YAP regulates RPE specification and maintenance in the RPE. Several studies demonstrate that YAP is required for RPE identity in the embryo and adult; however, the molecular mechanism is not well understood. Here, I will investigate the hypothesis that YAP and the transcription factor TEAD directly regulate expression of RPE- specific genes by using chromatin immunoprecipitation and luciferase assays. The results of these experiments will reveal how YAP regulates RPE specification, and how the Hippo signaling pathway can be modulated to promote RPE regeneration. Understanding the cellular and molecular mechanisms that promote RPE regeneration will help identify and develop therapeutic strategies for AMD.