Ocular RTEF-1 Isoforms and Control of VEGF Expression: Implications for Therapy

Oregon Health & Science University, Portland OR

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Abstract

DESCRIPTION (provided by applicant): We are interested in characterizing factors that regulate the transcription of the vascular endothelial factor (VEGF) gene in ischemic conditions that lead to ocular angiogenesis. It is known that increased expression of the VEGF gene within the eye leads to ocular neovascular disease, and included within this gamut of diseases is retinopathy of prematurity (ROP), retinal vascular occlusions (RVO), age-related macular degeneration (AMD) and diabetic retinopathy (DR). Understanding the mechanism and factors involved in VEGF gene regulation under an ocular ischemic assault will allow for the development of new therapeutic targets for prevention or treatment of ocular neovascular disease. We have recently demonstrated the presence of novel alternatively spliced isoforms of the transcription factor Related Transcriptional Enhancer Factor-1 (RTEF-1) within human vascular endothelial cells isolated from ocular tissue and within the retina of a mouse model of retinopathy of prematurity (OIR model). The human isoforms are capable of modulating expression from the VEGF promoter in vitro, and appear to act independently of the hypoxia response element (HRE) mediated pathway. Depending on the isoform expression can either be enhanced or inhibited. In addition we discovered that certain isoforms are only produced under hypoxic conditions and levels of specific isoforms are elevated under the same conditions within the retina of animal model of OIR and retinal vein occlusion (RVO). We hypothesize that novel RTEF-1 isoforms are produced within ocular cells under hypoxic conditions, which mediate the expression levels of VEGF transcription, assisted by cell-specific cofactors, and hence influence progression of ocular neovascularization. We propose to test this hypothesis with the following aims. (1) In relation to the regulation of VEGF transcription, characterize the function of novel RTEF-1 isoforms identified within various human ocular cells cultured under normal and hypoxic conditions, and from retinal tissue isolated from an animal model of OIR. (2) Determine whether isoforms of RTEF-1 known to inhibit VEGF production can prevent or ameliorate neovascularization response in a mouse model of OIR. (3) Identify ocular cell-specific protein co-factors that are necessary for the function of each RTEF-1 isoform under a normoxic and hypoxic environment. The specific aims of this study are designed to further our knowledge of VEGF gene regulation by previously unidentified RTEF-1 isoforms within the normal and ischemic eye. Our long-term goal is to identify novel factors that influence the onset and progression of ischemic ocular neovascular disease, which will allow evolution and testing of non-destructive therapeutic reagents for treatment to prevent vision loss.