Project II: Summary Age-related Macular Degeneration (AMD) is the leading cause of vision loss among older Americans and is caused by dysfunction of the Retinal Pigmented Epithelium (RPE) leading to neurodegeneration. The RPE functions to maintain the outer blood-retinal barrier and support photoreceptor function, including regeneration of visual pigment and turnover of outer segments. Given that a major function of the RPE is to process photo- receptor outer segments, the proper functioning of the RPE endosomal pathway is important for retinal health. Thus, RPE-derived exosomes are a likely source of real-time biological information into retinal health and are available in the systemic circulation. The underlying hypothesis of this project is that release of exosomes (nano- sized extracellular vesicles) from stressed RPE cells plays a central role in desmosome disassembly, outer blood-retina barrier (oBRB) integrity, and contributes to pathognomonic deposit formation in AMD. To explore this hypothesis, I present two aims focused on neurodegeneration and the RPE with the goal of translation of this work to novel therapeutic interventions in retinal degenerative diseases: Aim 1 interrogates the role of exosome release in vitro in stressed RPE models of AMD and Aim 2 interrogates the role of exosome release in AMD and retinal degeneration mouse models. By evaluating complementary in vitro and in vivo AMD models, our approach is to determine the role of exosome secretion on RPE health, and test whether pharmacological or gene therapy interventions are possible by: (1) Characterizing the desmosomal and hemidesmosomal content of basal-side exosomes in aged RPE and RPE stressed by pathophysiological conditions implicated in AMD, while modulating exosome release, and (2) modulating the level of exosome release in two different and complementary mouse models of AMD features to identify novel approaches to therapy and/or intervention. This project is innovative as it tests the novel hypothesis that exosomes from the basolateral side of stressed RPE cells play a central role in disassembly of desmosomes which impacts oBRB integrity, and contribute to pathognomonic deposit formation in AMD. Moreover, the proposal is both significant and innovative as it explores possible avenues for therapeutic intervention aimed at regulating exosome release from RPE, a novel avenue for AMD treatment to achieve functional restoration in situ. The project is also significant in leveraging my background in developing and characterizing AMD mouse models, and my expertise in RPE cell biology and exosome biology. The project plan lays the foundation for my future research program.