Primary open angle glaucoma (POAG) is a leading cause of irreversible vision loss and blindness. Current treatments of POAG are aimed at reducing intraocular pressure (IOP), the most important risk factor for the development and progression of the disorder. However, current glaucoma treatments do not address the underlying disease mechanisms. Mutations in the myocilin gene (MYOC) are the most common known genetic cause of glaucoma. Three developments provide us with an opportunity to investigate novel treatments of glaucoma directed at the underlying disease mechanisms: 1. The development of a POAG mouse model (Tg- MYOCY437H) in our laboratory that expresses mutant myocilin encoded by the MYOC gene; 2. The use of the Tg-MYOCY437H mouse model to demonstrate in vivo that mutant myocilin accumulates in the endoplasmic reticulum (ER) and induces ER stress in the trabecular meshwork (TM) of the eye as a key mechanistic component leading to glaucoma; and 3. The recent development of genome editing nucleases as a valuable tool for gene therapy applications. Furthermore, the fact that myocilin-associated POAG results from dominant gain of function mutations and the fact that ER stress induced apoptosis in the TM leads to POAG provide an opportunity to explore novel glaucoma treatments by in vivo elimination of mutant MYOC and/or apoptosis pathway genes (e.g. Chop). We propose to utilize the Tg-MYOCY437H mouse model of glaucoma to further explore the role of ER stress in POAG and to use a novel genome editing method (CRISPR) to explore novel POAG treatments, specifically the elimination of mutant myocilin from the TM of Tg-MYOCY437H mice, as well as the elimination of ER stress genes from TM cells. Clustered regularly interspaced short palindromic repeats (CRISPR) is an endogenous nuclease system, which uses RNA sequences to guide the cleavage of DNA by the CRISPR-associated nuclease Cas9. In addition, we will explore the role of ER stress in steroid induced glaucoma for the purpose of determining whether the genome editing strategy of glaucoma treatment can be applied to this form of glaucoma. Importantly, we will extend our work to humans by exploring the utility of genome editing in a human eye perfusion organ culture system. We believe that Cas9 can be used to remove the mutant MYOC gene and provide the first effective cure for MYOC mutation-induced glaucoma. In addition, the eye is an ideal test site for establishing the therapeutic potential of the Cas9 technology, and this work will pave the path for the application of Cas9 for treating a variety of genetic eye disorders, as well disorders affecting other organ systems.
The successful completion of this project will lead to insight into the disease mechanisms causing primary open angle glaucoma, a major human blinding disorder. The results will potentially improve diagnosis, genetic risk assessment, and treatment of this common disorder.
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