HIF dysregulation as a novel genetic model to study retinal neovascular disease.

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DESCRIPTION (provided by applicant): The overall goal of this proposal is to provide the principal investigator (PI) with the experience and skills necessary to become an independent researcher studying basic mechanisms of retinal neovascular disease. The scientific focus of this proposal is to gain a better understanding of pathological angiogenesis in the eye, a principal cause of irreversible blindness worldwide. Emerging evidence suggests a shared etiology for neovascularization in the eye in which local hypoxia leads to upregulation of the hypoxia inducible factor (HIFs). HIFs are a family of transcription factors which stimulate production of several "hypoxia inducible" genes, including angiogenic growth factors (e.g. vascular endothelial growth factor or VEGF), which, in turn, promote the growth of (leaky) blood vessels. Of interest, significant progress in our understanding of the regulation of HIFs in pathological angiogenesis has come from recent work examining the dysregulation of HIFs in patients with von Hippel-Lindau (VHL) disease. Retinal hemangioblastomas are neovascular tumors that remain the most common clinical manifestation in patients with VHL disease, often manifesting with profuse edema and resulting in profound loss of vision. The VHL protein (pVHL) targets HIFs for degradation. Therefore, loss of pVHL in patients with VHL disease results in dysregulation of HIFs and over expression of hypoxia-inducible genes, mimicking pathological angiogenesis. The underlying hypothesis of this proposal is that VHL retinal hemangioblastomas are a model for pathological angiogenesis and provide an ideal genetic model to examine the role(s) of HIFs and their targets in the breakdown of the inner blood- retinal barrier (iBRB), a poorly understood, but critical early event in retinal neovascular disease. To address this hypothesis, three specific aims are proposed: Aim 1: To examine the necessity for HIFs in the breakdown of the iBRB. Aim 2: To determine if HIF dysregulation is sufficient to promote breakdown of the iBRB. Aim 3: To determine the relative contribution of HIF-dependent growth factors in breakdown of the iBRB. In the course of the proposed research and selected didactic activities, the PI will gain invaluable training experience and mentoring in studying the molecular pathogenesis of retinal neovascular disease. This expertise is deemed essential for the PI who aspires to develop an independent research program studying basic mechanisms of retinal pathological angiogenesis. PUBLIC HEALTH RELEVANCE: Retinal neovascular disease is the leading cause of irreversible blindness in the developed world. This proposal intends to study the underlying cellular and biochemical changes leading to the breakdown of the inner blood-retinal barrier by studying a novel genetic model for retinal neovascular disease. In addition to numerous retinal diseases (e.g. proliferative diabetic retinopathy, ischemic vascular occlusions, retinopathy of prematurity, and macular degeneration), these studies may promote a greater appreciation for the cause of other ocular diseases which involve dysregulated angiogenesis (e.g. ocular tumors and neovascular glaucoma).