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Haraguchi Y, Chiang TK, Yu M. Application of Electrophysiology in Non-Macular Inherited Retinal Dystrophies. J Clin Med 2023; 12:6953. [PMID: 37959417 PMCID: PMC10649281 DOI: 10.3390/jcm12216953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Revised: 11/02/2023] [Accepted: 11/03/2023] [Indexed: 11/15/2023] Open
Abstract
Inherited retinal dystrophies encompass a diverse group of disorders affecting the structure and function of the retina, leading to progressive visual impairment and, in severe cases, blindness. Electrophysiology testing has emerged as a valuable tool in assessing and diagnosing those conditions, offering insights into the function of different parts of the visual pathway from retina to visual cortex and aiding in disease classification. This review provides an overview of the application of electrophysiology testing in the non-macular inherited retinal dystrophies focusing on both common and rare variants, including retinitis pigmentosa, progressive cone and cone-rod dystrophy, bradyopsia, Bietti crystalline dystrophy, late-onset retinal degeneration, and fundus albipunctatus. The different applications and limitations of electrophysiology techniques, including multifocal electroretinogram (mfERG), full-field ERG (ffERG), electrooculogram (EOG), pattern electroretinogram (PERG), and visual evoked potential (VEP), in the diagnosis and management of these distinctive phenotypes are discussed. The potential for electrophysiology testing to allow for further understanding of these diseases and the possibility of using these tests for early detection, prognosis prediction, and therapeutic monitoring in the future is reviewed.
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Affiliation(s)
| | | | - Minzhong Yu
- Department of Ophthalmology, University Hospitals, Case Western Reserve University, Cleveland, OH 44106, USA
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Mayerl SJ, Bajgai S, Ludwig AL, Jager LD, Williams BN, Bacig C, Stoddard C, Sinha D, Philpot BD, Gamm DM. Human retinal organoids harboring IMPG2 mutations exhibit a photoreceptor outer segment phenotype that models advanced retinitis pigmentosa. Stem Cell Reports 2022; 17:2409-2420. [PMID: 36206764 PMCID: PMC9669399 DOI: 10.1016/j.stemcr.2022.09.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 09/06/2022] [Accepted: 09/07/2022] [Indexed: 11/05/2022] Open
Abstract
Interphotoreceptor matrix proteoglycan 2 (IMPG2) mutations cause a severe form of early-onset retinitis pigmentosa (RP) with macular involvement. IMPG2 is expressed by photoreceptors and incorporated into the matrix that surrounds the inner and outer segments (OS) of rods and cones, but the mechanism of IMPG2-RP remains unclear. Loss of Impg2 function in mice produces a mild, late-onset photoreceptor phenotype without the characteristic OS loss that occurs in human patients. We generated retinal organoids (ROs) from patient-derived induced pluripotent stem (iPS) cells and gene-edited embryonic stem cells to model human IMPG2-RP in vitro. All ROs harboring IMPG2 mutations lacked an OS layer, in contrast to isogenic controls. Subsequent protein analyses revealed that this phenotype arises due to a loss of IMPG2 expression or its inability to undergo normal post-translational modifications. We hypothesized that loss of IMPG2 function destabilizes the interphotoreceptor matrix and renders the OS vulnerable to physical stressors, which is accentuated in the tissue culture environment. In support of this mechanism, transplantation of IMPG2 mutant ROs into the protected subretinal space of immunocompromised rodents restored OS production. Beyond providing a robust platform to study IMPG2-RP, this human RO model system may serve a broader role in honing strategies to treat advanced photoreceptor-based diseases.
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Affiliation(s)
- Steven J Mayerl
- Cellular and Molecular Pathology University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA; Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
| | - Simona Bajgai
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
| | - Allison L Ludwig
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA; Waisman Center, University of Wisconsin-Madison, Madison, WI, USA; Comparative Biomedical Sciences, University of Wisconsin-Madison, Madison, WI, USA
| | - Lindsey D Jager
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
| | - Brittany N Williams
- Department of Cell Biology & Physiology, University of North Carolina, Chapel Hill, NC, USA; Carolina Institute for Developmental Disabilities, University of North Carolina, Chapel Hill, NC, USA; Neuroscience Center, University of North Carolina, Chapel Hill, NC, USA
| | - Cole Bacig
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
| | - Christopher Stoddard
- Department of Genetics and Genome Sciences, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Divya Sinha
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA; Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
| | - Benjamin D Philpot
- Department of Cell Biology & Physiology, University of North Carolina, Chapel Hill, NC, USA; Carolina Institute for Developmental Disabilities, University of North Carolina, Chapel Hill, NC, USA; Neuroscience Center, University of North Carolina, Chapel Hill, NC, USA
| | - David M Gamm
- Cellular and Molecular Pathology University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA; Waisman Center, University of Wisconsin-Madison, Madison, WI, USA; Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA.
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