Glaucoma is a heterogeneous ocular disease that affects nearly 70 million individuals worldwide. Despite the
availability of symptomatic treatments and surgeries, ~10% of patients reach permanent blindness, and
treatments do not address the underlying cause of the disease. In most glaucoma subtypes, elevated
intraocular pressure (IOP) is the causal risk factor. Elevated IOP originates from trabecular meshwork (TM)
dysfunction. Neuron-like TM cells maintain the TM extracellular matrix, an anterior eye segment tissue, and TM
cell loss an established pathological hallmark of a glaucomatous TM. Genetics also support TM cell death as
being an early event in glaucoma development. Coding mutations in myocilin are closely associated with the
early-onset autosomal-dominant inherited form of glaucoma and comprise the strongest genetic link to
glaucoma (4-10% of all glaucoma and ~30% of juvenile onset). Expressed robustly in TM cells, mutant myocilin
cannot be secreted and instead mutant myocilin is sequestered in the endoplasmic reticulum (ER) where it is
cytotoxic. TM cell loss hastens IOP elevation, leading to an accelerated timeline for retinal cell death and optic
nerve damage in the posterior eye, which are the proximal causes of vision loss in glaucoma. Molecular
pathways contributing to TM cytotoxicity are not established, however, hindering the development of disease-
modifying therapies. We will use our newly developed baker’s yeast (Saccharomyces cerevisiae) model of
myocilin-associated glaucoma to decipher the molecular mechanisms underlying the pathophysiology of TM
cell loss in glaucoma. S. cerevisiae is a model system that has been used to decipher mechanisms underlying
the pathophysiology of numerous human proteostasis disorders, including Parkinson’s, Alzheimer’s, and
Huntington’s diseases, and has led to new therapeutic targets. Our S. cerevisiae model faithfully replicates the
gain-of-function mechanism underlying glaucoma pathogenesis: when expressed in the ER of S. cerevisiae,
mutant myocilin is cytotoxic, and, depending on the experimental design, wild-type myocilin can either be
benign or moderately cytotoxic. Further, targeted screening of S. cerevisiae deletion clones associated with
proteostasis has identified gene-specific modulation of cytotoxicity, with new targets beyond those identified
previously from experiments using mammalian cells. We propose three Specific Aims to define the cytotoxicity
mechanisms caused by myocilin misfolding: (1) screen the S. cerevisiae gene deletion library to identify clones
that restore cell viability; (2) probe the mechanisms underlying preliminary hits obtained in preparation of Aim 1
and new hits that emerge as Aim 1 is completed; (3) conduct a high throughput screen to identify small
molecules that rescue cytotoxicity due to mutant myocilin misfolding. The expected outcomes are gene
products and pathways that sensitize cells to myocilin toxicity and small molecule leads for rescuing TM cell
death. In the long term, this work will identify new targets for disease-modifying therapies for glaucoma.