The Role of mtDNA/ZBP1 in Retinal Neurodegeneration - Project title: The role of mtDNA/ZBP1 in retinal neurodegeneration SUMMARY Glaucoma is the second leading cause of irreversible blindness worldwide. It is characterized by progressive retinal ganglion cell (RGC) degeneration. Glaucoma is strongly associated with increased intraocular pressure (IOP) and IOP is the only treatable target for glaucoma. However, lowering IOP does not always stop the progression of glaucoma. It is urgent to identify other mechanisms of neuropathy in glaucoma for therapeutic intervention. Mitochondrial DNA (mtDNA) is very vulnerable to oxidative stress-induced damage and is released into the cytoplasm or extracellular environment. Given that mtDNA shares several characteristics with bacterial DNA including small size, multiple copies and methylation status, the released mtDNA can activate pathways historically reserved for pathogen recognition. ZBP1 senses double-stranded DNA and RNA that adopt, or are prone to adopt, a left-handed Z-form double-helical structure. It plays an important role in innate immune response by binding to viral nucleic acids, leading to the production of type I interferons and other inflammatory responses crucial in controlling viral infections and triggering death of infected cells. This application, led by muti-PIs possessing unique complimentary expertise, will test the hypothesis that damaged mtDNA acts as a crucial active signal in RGC degeneration during glaucoma by binding to the intracellular DNA/RNA sensor ZBP1. Novel ZBP1 conditional knockout or overexpression mice, in vivo tracking of CD63+ extracellular vesicles (EVs), and comprehensive in vitro mechanistic studies will be integrated to test this hypothesis. Completion of the proposed studies will provide important new knowledge about the damaged mtDNA, which acts as a novel immune factor, in induction of intrinsic signaling in RGCs and in the regulation of microglial activation by binding to a novel intracellular DNA/RNA sensor ZBP1. These mechanisms may guide the development of novel therapies for glaucoma. This proposal is in line with Vision for the Future in the NEI Strategic Plan, Areas of Emphasis “Immune System and Eye Health”: 1) investigate neurobiology roles for immune factors that challenge orthodoxy and examine whether these “immune” factors are playing nontraditional roles for vision function; 2) understand the role of resident retinal cells in promoting immune homeostasis.
