Primary open angle glaucoma (POAG), the most common form of glaucoma, is usually accompanied by elevated intraocular pressure (IOP) due to failure of the trabecular meshwork (TM) to maintain normal levels of aqueous humor outflow. We recently generated a novel transgenic murine model (Tg-MYOCY437H) that expresses mutant myocilin, a known leading genetic cause of POAG in humans and replicates human glaucoma phenotypes. Importantly, we have associated endoplasmic reticulum (ER) stress to the pathogenesis of glaucoma in Tg-MYOCY437H mice. Misfolded myocilin accumulates in the ER, induces ER stress and activates a protective unfolded protein response (UPR). Along with UPR activation, mutant myocilin also induces autophagy, a process of lysosomal degradation known to degrade protein aggregates. However, failure to eliminate myocilin aggregates possibly due to insufficient UPR and impaired autophagy, TM cells induce the ER stress-initiated apoptotic transcriptional factor, Chop, which may further worsen ER homeostasis and cause TM dysfunction/loss, elevating IOP and resulting in POAG. The current proposal will further investigate the role of chronic ER stress in the pathogenesis of myocilin as well as non-myocilin associated POAG. During the mentored phase, the proposed studies will determine whether failure to activate the protective UPR (Atf-6?-/-) exacerbates glaucoma phenotypes, whereas interference with ER stress-induced apoptosis (Chop-/-) prevents glaucoma in Tg-MYOCY437H mice. In addition, we will investigate whether ER stress is activated in port-mortem TM tissues from POAG donors. During the independent phase, we will examine whether induction of ER stress in the TM is associated with elevation of IOP in a mouse model of dexamethasone-induced ocular hypertension. In addition, we will examine the role of autophagy in degradation of myocilin aggregates and will determine whether inducing autophagy by rapamycin will rescue the glaucoma of Tg-MYOCY437H mice. Specifically, the candidate will learn and generate new models of ER stress using Atf6? and Chop knockout mice, generate induced pluripotent stem cells (iPSCs)-derived trabecular meshwork- like cells from POAG patients, and characterize a dexamethasone-induced ocular hypertension mouse model in the laboratory of Dr. Val Sheffield. Additionally, during the mentored phase, the candidate will continue his professional and scientific career development through continual guidance from the advisory committee. He will attend scientific conferences, and collaborate with ER stress expert, Dr. Thomas Rutkowski and glaucoma clinical expert, Dr. Lee Alward. He will also acquire teaching experience. This project will facilitate continued technical, intellectul, and professional training of the candidate, and assist the candidate in the establishment of an independent research laboratory at an academic research institute.

Public Health Relevance

The successful completion of this project will lead to insight into elevated intraocular pressure, a major risk factor of the human blinding disorder, primary open angle glaucoma. The results will potentially improve diagnosis, genetic risk assessment and treatment of this common disorder.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Career Transition Award (K99)
Project #
1K99EY022077-01A1
Application #
8383990
Study Section
Special Emphasis Panel (ZEY1-VSN (10))
Program Officer
Agarwal, Neeraj
Project Start
2012-09-01
Project End
2014-08-31
Budget Start
2012-09-01
Budget End
2013-08-31
Support Year
1
Fiscal Year
2012
Total Cost
$87,678
Indirect Cost
$6,495
Name
University of Iowa
Department
Pediatrics
Type
Schools of Medicine
DUNS #
062761671
City
Iowa City
State
IA
Country
United States
Zip Code
52242
Kasetti, Ramesh B; Maddineni, Prabhavathi; Millar, J Cameron et al. (2017) Increased synthesis and deposition of extracellular matrix proteins leads to endoplasmic reticulum stress in the trabecular meshwork. Sci Rep 7:14951
Patel, Gaurang C; Phan, Tien N; Maddineni, Prabhavathi et al. (2017) Dexamethasone-Induced Ocular Hypertension in Mice: Effects of Myocilin and Route of Administration. Am J Pathol 187:713-723
Kasetti, Ramesh B; Phan, Tien N; Millar, J Cameron et al. (2016) Expression of Mutant Myocilin Induces Abnormal Intracellular Accumulation of Selected Extracellular Matrix Proteins in the Trabecular Meshwork. Invest Ophthalmol Vis Sci 57:6058-6069
Peters, Joseph C; Bhattacharya, Sanjoy; Clark, Abbot F et al. (2015) Increased Endoplasmic Reticulum Stress in Human Glaucomatous Trabecular Meshwork Cells and Tissues. Invest Ophthalmol Vis Sci 56:3860-8
Beckel, Jonathan M; Argall, Arthur J; Lim, Jason C et al. (2014) Mechanosensitive release of adenosine 5'-triphosphate through pannexin channels and mechanosensitive upregulation of pannexin channels in optic nerve head astrocytes: a mechanism for purinergic involvement in chronic strain. Glia 62:1486-501
Zode, Gulab S; Sharma, Arti B; Lin, Xiaolei et al. (2014) Ocular-specific ER stress reduction rescues glaucoma in murine glucocorticoid-induced glaucoma. J Clin Invest 124:1956-65