Understanding OPA1 mutation-driven dominant optic atrophy using human PSC-derived retinal ganglion cells

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PROJECT SUMMARY/ABSTRACT Dominant optic atrophy (DOA) is the most prevalent genetic optic neuropathy, affecting roughly 1:12,000 to 1:50,000 individuals worldwide. DOA patients exhibit retinal ganglion cell (RGC) degeneration, which leads to progressive bilateral vision loss. The majority of DOA cases are caused by mutations in the gene optic atrophy 1 (OPA1), a nuclear gene that encodes a protein targeted to the inner mitochondrial membrane. Interestingly, although OPA1 is ubiquitously expressed in all human tissues, RGCs appear to be the only cell type affected by OPA1 mutations. It is therefore essential to study DOA in human RGCs in order to understand the pathological mechanisms present in these cells that render them particularly prone to degeneration. However, studies of human RGCs have been historically difficult due to the rarity of primary retinal tissues and scarcity of RGCs, which only comprise ~2% of the total retinal cells. This proposal seeks to address the significant unmet need for developing human RGC models of DOA. Advances in stem cell technology have enabled our laboratory to routinely produce human RGCs from human pluripotent stem cell (hPSC)-derived 3D retinal organoid cultures. In addition, I have established OPA1 mutant hPSC lines by using gene editing technology and by reprogramming DOA patients’ peripheral blood cells. Differentiating these OPA1 mutant hPSC lines into retinal organoids will provide the first opportunity to establish DOA disease models in authentic, human RGCs. In the proposed study, I will use OPA1 mutant hPSC-derived human RGC populations to investigate pathological mechanisms of OPA1 mutation-mediated RGC degeneration. As OPA1 plays significant roles in promoting mitochondrial fusion, maintaining the integrity of the cristae, and stabilizing super complexes of the respiratory chain, RGC death observed in DOA patients is likely a result of mitochondrial defects that can lead to an insufficient energy supply, increased oxidative stress, and/or leakage of cytochrome c into the cytoplasm. I will investigate the mitochondrial dynamics, cristae structure, and metabolic state of OPA1-mutant RGCs to delineate whether changes in these fundamental processes underly the RGC degeneration observed in DOA patients. Findings from this study will advance our understanding of the pathological mechanisms affecting DOA patients’ RGCs and facilitate the development of therapies that can preserve or rescue vision in DOA patients. Additionally, our findings could provide important insights into other neurodegenerative diseases that share common metabolic deficiencies with DOA.