Advancing novel therapies for optic neuropathy with a nonhuman primate model

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PROJECT SUMMARY Optic neuropathies are common causes of blindness worldwide, affect the lives of millions, and lack effective treatments to restore vision. Autosomal dominant optic atrophy (ADOA) is an inherited optic neuropathy that affects ~3 per 100,000 people worldwide, results in vision impairment, and has no treatment. It is primarily due to mutations in the optic atrophy 1 (OPA1) gene, which encodes a mitochondrial dynamin-related protein critical for mitochondrial stability and energy production. A major limitation to the development of effective therapies for optic neuropathies is the use of animal models that poorly replicate the human condition. Particularly for optic nerve and RGC disorders, studies would benefit from the use nonhuman primates (NHP) with optic nerve and retinal anatomy, physiology and pathology, which closely mirrors that of humans. Consequently, well-defined NHP models of optic neuropathy that are more predictive of human conditions are necessary to efficiently advance new therapies. We identified rhesus macaques heterozygous and homozygous for a missense mutation in OPA1 that demonstrate optic nerve head pallor and thinning of the retinal nerve fiber layer in comparison to wildtype controls; these findings are consistent with ADOA in human patients. We will fully define this NHP model of ADOA and determine its impact on RGC structure and function longitudinally over a 5-year period. Specifically, we will assess the onset and progression of retinal dysfunction utilizing electroretinography, retinal flavoprotein fluorescence and visual testing. Importantly, we will correlate the clinical findings with detailed transcriptomic, histologic, and immunohistochemical data for a comprehensive characterization of this NHP model of ADOA. The ADOA transcriptome from NHPs is highly likely to identify novel genes and pathways involved in RGC pathology and neurodegeneration as well as validate previously implicated pathways thus revealing new therapeutic targets. We will also perform detailed histological, immunohistochemical and ultrastructural analyses to assess RGC soma, axons and dendrites as well as their mitochondrial size and number in the macula, papillomacular bundle, and periphery of the retina. Finally, through selective breeding of ADOA-affected NHPs, we will generate a supply of macaques heterozygous and homozygous for the OPA1 mutation for future study. To make this new NHP optic neuropathy model available for therapeutic testing, we propose three Specific Aims: 1) To define the morphologic features and phenotypic spectrum of a NHP model of ADOA, 2) to determine the impact of the OPA1 A8S mutation on RGC function in NHPs, and 3) to determine mRNA and protein expression in RGCs of ADOA-affected NHPs. Once the most predictive endpoints of disease and sufficient animals with ADOA are identified, we will pursue additional studies of etiopathogenesis and novel therapeutic strategies. This comprehensive NHP model of ADOA will be a highly valuable resource for the vision science and neurodegenerative disease communities.