Disease modeling and pharmacological rescue of autosomal dominant retinitis pigmentosa associated with RHO copy number variation
Sangeetha Kandoi,
Cassandra Martinez,
Kevin Xu Chen,
Miika Mehine,
L Vinod K Reddy,
Brian C Mansfield,
Jacque L Duncan,
Deepak A Lamba
Affiliations
Sangeetha Kandoi
Department of Ophthalmology, University of California, San Francisco, San Francisco, United States; Eli and Edythe Broad Center of Regeneration Medicine & Stem Cell Research University of California, San Francisco, San Francisco, United States
Cassandra Martinez
Department of Ophthalmology, University of California, San Francisco, San Francisco, United States; Eli and Edythe Broad Center of Regeneration Medicine & Stem Cell Research University of California, San Francisco, San Francisco, United States
Kevin Xu Chen
Eli and Edythe Broad Center of Regeneration Medicine & Stem Cell Research University of California, San Francisco, San Francisco, United States
Miika Mehine
Blueprint Genetics, Bethesda, United States
L Vinod K Reddy
Department of Ophthalmology, University of California, San Francisco, San Francisco, United States; Eli and Edythe Broad Center of Regeneration Medicine & Stem Cell Research University of California, San Francisco, San Francisco, United States
Brian C Mansfield
Section on Cellular Differentiation, Division of Translational Medicine, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
Department of Ophthalmology, University of California, San Francisco, San Francisco, United States; Eli and Edythe Broad Center of Regeneration Medicine & Stem Cell Research University of California, San Francisco, San Francisco, United States; Immunology and Regenerative Medicine, Genentech, South San Francisco, United States
Retinitis pigmentosa (RP), a heterogenous group of inherited retinal disorder, causes slow progressive vision loss with no effective treatments available. Mutations in the rhodopsin gene (RHO) account for ~25% cases of autosomal dominant RP (adRP). In this study, we describe the disease characteristics of the first-ever reported mono-allelic copy number variation (CNV) in RHO as a novel cause of adRP. We (a) show advanced retinal degeneration in a male patient (68 years of age) harboring four transcriptionally active intact copies of rhodopsin, (b) recapitulated the clinical phenotypes using retinal organoids, and (c) assessed the utilization of a small molecule, Photoregulin3 (PR3), as a clinically viable strategy to target and modify disease progression in RP patients associated with RHO-CNV. Patient retinal organoids showed photoreceptors dysgenesis, with rod photoreceptors displaying stunted outer segments with occasional elongated cilia-like projections (microscopy); increased RHO mRNA expression (quantitative real-time PCR [qRT-PCR] and bulk RNA sequencing); and elevated levels and mislocalization of rhodopsin protein (RHO) within the cell body of rod photoreceptors (western blotting and immunohistochemistry) over the extended (300 days) culture time period when compared against control organoids. Lastly, we utilized PR3 to target NR2E3, an upstream regulator of RHO, to alter RHO expression and observed a partial rescue of RHO protein localization from the cell body to the inner/outer segments of rod photoreceptors in patient organoids. These results provide a proof-of-principle for personalized medicine and suggest that RHO expression requires precise control. Taken together, this study supports the clinical data indicating that RHO-CNV associated adRPdevelops as a result of protein overexpression, thereby overloading the photoreceptor post-translational modification machinery.
