Development and characterization of an inducible model for myocilin POAG

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Primary Open Angle Glaucoma (POAG) is the leading cause of irreversible blindness affecting over 57 million people worldwide. Progressive loss of retinal ganglion cells (RGCs) and degeneration of optic nerve axons is the pathological hallmark of glaucoma. Elevated intraocular pressure (IOP) due to dysfunction of trabecular meshwork (TM) is the most significant and the only known modifiable risk factor for glaucoma. Understanding of the pathological mechanisms of glaucomatous TM dysfunction and neurodegeneration is limited due to lack of robust and faithful mouse model that mimics both TM dysfunction and glaucomatous neurodegeneration. Developing a mouse model of known genetic cause of POAG represents an ideal strategy to understand the pathophysiology of POAG. Mutations in myocilin (MYOC) gene are the most common genetic cause of POAG. Using TARGATT site-specific knockin strategy, we developed a Cre-inducible transgenic mice that expresses DsRed-tagged Y437H mutant of human myocilin (Tg.Cre-MYOCY437H). This technology utilizes serine integrase, PhiC31 (ΦC31) to insert any gene of interest (a single copy) into a preselected intergenic and transcriptionally active genomic locus (Hipp11), which has been engineered with a docking site. This allows stable and site- specific transgene integration. In our preliminary studies, we observed that a single intravitreal injection of helper adenovirus (HAd) 5 expressing Cre selectively induced human mutant myocilin protein in mouse TM. Importantly, Ad5.Cre injection resulted in significant and sustained IOP elevation in Tg.Cre-MYOCY437H mice. We hypothesize that TM-specific expression of mutant myocilin leads significant and pronounced IOP elevation and glaucomatous neurodegeneration in Tg.Cre-MYOCY437H mice. The major goals of this application are to induce mutant myocilin expression in TM using HAd5-cre injections and to characterize glaucoma phenotypes of Tg.Cre-MYOCY437H mice. In Aim 1, we will determine whether HAd5-mediated Cre induces mutant myocilin expression in TM and elevates IOP in Tg.Cre-MYOCY437H mice. In Aim 2, we will determine whether HAd5-Cre- induced IOP elevation leads to glaucomatous neurodegeneration in Tg.Cre-MYOCY437H mice. Our proposal will utilize highly innovative approaches. These include use of efficient and site-specific gene knockin strategy for generation of transgenic mice, a comprehensive investigation of outflow pathway, RGC functional and structural loss, optic nerve damage and damage to the visual centers of the brain. Our proposed studies will develop much needed mouse model of POAG that faithfully replicate all features of glaucoma.