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Songstad AE, Wiley LA, Duong K, Kaalberg E, Flamme-Wiese MJ, Cranston CM, Riker MJ, Levasseur D, Stone EM, Mullins RF, Tucker BA. Generating iPSC-Derived Choroidal Endothelial Cells to Study Age-Related Macular Degeneration. Invest Ophthalmol Vis Sci 2016; 56:8258-67. [PMID: 26720480 DOI: 10.1167/iovs.15-17073] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Age-related macular degeneration (AMD), the most common cause of incurable blindness in the western world, is characterized by the dysfunction and eventual death of choroidal endothelial (CECs), RPE, and photoreceptor cells. Stem cell-based treatment strategies designed to replace photoreceptor and RPE cells currently are a major scientific focus. However, the success of these approaches likely also will require replacement of the underlying, supportive choroidal vasculature. The purpose of this study was to generate stem cell-derived CECs to develop efficient differentiation and transplantation protocols. METHODS Dermal fibroblasts from the Tie2-GFP mouse were isolated and reprogrammed into two independent induced pluripotent stem cell (iPSC) lines via viral transduction of the transcription factors Oct4, Sox2, Klf4, and c-Myc. Tie2-GFP iPSCs were differentiated into CECs using a coculture method with either the RF6A CEC line or primary mouse CECs. Induced pluripotent stem cell-derived CECs were characterized via RT-PCR and immunocytochemistry for EC- and CEC-specific markers. RESULTS Induced pluripotent stem cells generated from mice expressing green fluorescent protein (GFP) under control of the endothelial Tie2 promoter display classic pluripotency markers and stem cell morphology. Induced pluripotent stem cell-derived CECs express carbonic anhydrase IV, eNOS, FOXA2, PLVAP, CD31, CD34, ICAM-1, Tie2, TTR, VE-cadherin, and vWF. CONCLUSIONS Induced pluripotent stem cell-derived CECs will be a valuable tool for modeling of choriocapillaris-specific insults in AMD and for use in future choroidal endothelial cell replacement approaches.
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Collison FT, Park JC, Fishman GA, Stone EM, McAnany JJ. Two-color pupillometry in enhanced S-cone syndrome caused by NR2E3 mutations. Doc Ophthalmol 2016; 132:157-66. [PMID: 27033713 DOI: 10.1007/s10633-016-9535-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 03/22/2016] [Indexed: 11/29/2022]
Abstract
PURPOSE The purpose of this study was to evaluate pupillary light reflexes (PLRs) mediated by rod, cone, and intrinsically photosensitive retinal ganglion cell pathways as indices of outer- and inner-retinal function in patients who have enhanced S-cone syndrome (ESCS) due to NR2E3 mutations. METHODS Four patients with ESCS (ages 16-23 years) participated in the study. Subjects were tested with long- and short-wavelength single-flash full-field ERG stimuli under light-adapted conditions. They were also tested with an established pupillometry protocol involving 1-s duration, long- and short-wavelength stimuli under dark- and light-adapted conditions. The PLR was measured as a function of stimulus luminance. Transient PLRs were measured under all conditions, and sustained PLRs were measured under the highest luminance dark-adapted condition. RESULTS Two-color light-adapted full-field ERGs demonstrated larger amplitude responses for short-wavelength stimuli relative to long-wavelength stimuli of the same photopic luminance, with three of four ESCS patients having super-normal a-wave amplitudes to the short-wavelength stimulus. b/a wave ratios were reduced in all four cases. Transient PLRs elicited by low-luminance stimuli under dark-adapted conditions (rod-mediated) were unrecordable, whereas the sustained PLRs elicited by high-luminance stimuli (melanopsin-mediated) were normal. Cone-mediated PLRs were recordable for all four patients, but generally lower than normal in amplitude. However, the cone-mediated PLR was larger for the short-wavelength stimulus compared to the photopically matched long-wavelength stimulus at high luminances, a pattern that was not observed for control subjects. None of the PLR conditions demonstrated "super-normal" responses. CONCLUSION ESCS patients appear to have generally well-preserved cone- and melanopsin-mediated PLRs, indicating intact inner-retinal function. Two-color pupillometry demonstrates greater sensitivity to short-wavelength light under higher-luminance conditions and could complement the ERG as a tool for evaluating retinal function in ESCS.
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Collison FT, Park JC, Fishman GA, McAnany JJ, Stone EM. Full-Field Pupillary Light Responses, Luminance Thresholds, and Light Discomfort Thresholds in CEP290 Leber Congenital Amaurosis Patients. Invest Ophthalmol Vis Sci 2016; 56:7130-6. [PMID: 26529047 DOI: 10.1167/iovs.15-17467] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
PURPOSE To investigate visual function in patients with CEP290 Leber congenital amaurosis (LCA-CEP290), using three full-field tests that can be performed by patients with poor fixation. METHODS Six patients (age range, 9-39 years) with LCA-CEP290 participated in the study. Stimuli for all three tests (full-field stimulus test [FST], pupillometry, and light discomfort threshold [LDT] testing) were generated by the Diagnosys ColorDome ganzfeld, by using achromatic stimuli as well as long- and short-wavelength stimuli to target rod and cone photoreceptors with all three tests and, in the latter two tests, melanopsin photoreceptors. RESULTS Dark-adapted FST thresholds in LCA-CEP290 patients were cone mediated and elevated between 4.8 and 6.2 log units above the normal achromatic threshold. The FST threshold was not measurable in one patient. The rod-mediated transient pupillary light reflex (PLR) was absent in all but the youngest patient, where unreliable responses precluded PLR quantification. Cone-mediated transient PLRs were subnormal in five patients, and absent in another. Sustained melanopsin-mediated PLRs were measurable in all patients. Full-field LDT thresholds were elevated compared to normal controls, and were lower for short-wavelengh than for long-wavelength stimuli. CONCLUSIONS The FST thresholds and transient PLRs were cone mediated in our cohort LCA-CEP290 patients. Rod-mediated PLRs were undetectable, whereas melanopsin-mediated sustained responses were detected in all patients, suggesting a relative preservation of inner-retina function. The LDT elevations for the patients are somewhat paradoxical, given their subjective perception of photoaversion. Relative aversion to short-wavelength light suggests influence from melanopsin on LDTs in these patients.
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Drivas TG, Wojno AP, Tucker BA, Stone EM, Bennett J. Basal exon skipping and genetic pleiotropy: A predictive model of disease pathogenesis. Sci Transl Med 2016; 7:291ra97. [PMID: 26062849 DOI: 10.1126/scitranslmed.aaa5370] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Genetic pleiotropy, the phenomenon by which mutations in the same gene result in markedly different disease phenotypes, has proven difficult to explain with traditional models of disease pathogenesis. We have developed a model of pleiotropic disease that explains, through the process of basal exon skipping, how different mutations in the same gene can differentially affect protein production, with the total amount of protein produced correlating with disease severity. Mutations in the centrosomal protein of 290 kDa (CEP290) gene are associated with a spectrum of phenotypically distinct human diseases (the ciliopathies). Molecular biologic examination of CEP290 transcript and protein expression in cells from patients carrying CEP290 mutations, measured by quantitative polymerase chain reaction and Western blotting, correlated with disease severity and corroborated our model. We show that basal exon skipping may be the mechanism underlying the disease pleiotropy caused by CEP290 mutations. Applying our model to a different disease gene, CC2D2A (coiled-coil and C2 domains-containing protein 2A), we found that the same correlations held true. Our model explains the phenotypic diversity of two different inherited ciliopathies and may establish a new model for the pathogenesis of other pleiotropic human diseases.
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Braverman NE, Raymond GV, Rizzo WB, Moser AB, Wilkinson ME, Stone EM, Steinberg SJ, Wangler MF, Rush ET, Hacia JG, Bose M. Peroxisome biogenesis disorders in the Zellweger spectrum: An overview of current diagnosis, clinical manifestations, and treatment guidelines. Mol Genet Metab 2016; 117:313-21. [PMID: 26750748 PMCID: PMC5214431 DOI: 10.1016/j.ymgme.2015.12.009] [Citation(s) in RCA: 156] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Revised: 12/21/2015] [Accepted: 12/21/2015] [Indexed: 10/22/2022]
Abstract
Peroxisome biogenesis disorders in the Zellweger spectrum (PBD-ZSD) are a heterogeneous group of genetic disorders caused by mutations in PEX genes responsible for normal peroxisome assembly and functions. As a result of impaired peroxisomal activities, individuals with PBD-ZSD can manifest a complex spectrum of clinical phenotypes that typically result in shortened life spans. The extreme variability in disease manifestation ranging from onset of profound neurologic symptoms in newborns to progressive degenerative disease in adults presents practical challenges in disease diagnosis and medical management. Recent advances in biochemical methods for newborn screening and genetic testing have provided unprecedented opportunities for identifying patients at the earliest possible time and defining the molecular bases for their diseases. Here, we provide an overview of current clinical approaches for the diagnosis of PBD-ZSD and provide broad guidelines for the treatment of disease in its wide variety of forms. Although we anticipate future progress in the development of more effective targeted interventions, the current guidelines are meant to provide a starting point for the management of these complex conditions in the context of personalized health care.
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Zeng S, Whitmore SS, Sohn EH, Riker MJ, Wiley LA, Scheetz TE, Stone EM, Tucker BA, Mullins RF. Molecular response of chorioretinal endothelial cells to complement injury: implications for macular degeneration. J Pathol 2015; 238:446-56. [PMID: 26564985 DOI: 10.1002/path.4669] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 10/15/2015] [Accepted: 11/04/2015] [Indexed: 12/29/2022]
Abstract
Age-related macular degeneration (AMD) is a common, blinding disease of the elderly in which macular photoreceptor cells, retinal pigment epithelium and choriocapillaris endothelial cells ultimately degenerate. Recent studies have found that degeneration of the choriocapillaris occurs early in this disease and that endothelial cell drop-out is concomitant with increased deposition of the complement membrane attack complex (MAC) at the choroidal endothelium. However, the impact of MAC injury to choroidal endothelial cells is poorly understood. To model this event in vitro, and to study the downstream consequences of MAC injury, endothelial cells were exposed to complement from human serum, compared to heat-inactivated serum, which lacks complement components. Cells exposed to complement components in human serum showed increased labelling with antibodies directed against the MAC, time- and dose-dependent cell death, as assessed by lactate dehydrogenase assay and increased permeability. RNA-Seq analysis following complement injury revealed increased expression of genes associated with angiogenesis including matrix metalloproteinase (MMP)-3 and -9, and VEGF-A. The MAC-induced increase in MMP9 RNA expression was validated using C5-depleted serum compared to C5-reconstituted serum. Increased levels of MMP9 were also established, using western blot and zymography. These data suggest that, in addition to cell lysis, complement attack on choroidal endothelial cells promotes an angiogenic phenotype in surviving cells.
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Giacalone JC, Wiley LA, Burnight ER, Songstad AE, Mullins RF, Stone EM, Tucker BA. Concise Review: Patient-Specific Stem Cells to Interrogate Inherited Eye Disease. Stem Cells Transl Med 2015; 5:132-40. [PMID: 26683869 PMCID: PMC4729558 DOI: 10.5966/sctm.2015-0206] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 10/16/2015] [Indexed: 12/13/2022] Open
Abstract
Heritable diseases of the retina are major causes of blindness worldwide. The recent success of gene augmentation trials for the treatment of RPE65-associated Leber congenital amaurosis has underscored the need for model systems that accurately recapitulate disease. How induced pluripotent stem cell technology is being used to confirm the pathogenesis of novel genetic variants, interrogate the pathophysiology of disease, and accelerate the development of patient-centered treatments is discussed. Whether we are driving to work or spending time with loved ones, we depend on our sense of vision to interact with the world around us. Therefore, it is understandable why blindness for many is feared above death itself. Heritable diseases of the retina, such as glaucoma, age-related macular degeneration, and retinitis pigmentosa, are major causes of blindness worldwide. The recent success of gene augmentation trials for the treatment of RPE65-associated Leber congenital amaurosis has underscored the need for model systems that accurately recapitulate disease. With the advent of patient-specific induced pluripotent stem cells (iPSCs), researchers are now able to obtain disease-specific cell types that would otherwise be unavailable for molecular analysis. In the present review, we discuss how the iPSC technology is being used to confirm the pathogenesis of novel genetic variants, interrogate the pathophysiology of disease, and accelerate the development of patient-centered treatments. Significance Stem cell technology has created the opportunity to advance treatments for multiple forms of blindness. Researchers are now able to use a person’s cells to generate tissues found in the eye. This technology can be used to elucidate the genetic causes of disease and develop treatment strategies. In the present review, how stem cell technology is being used to interrogate the pathophysiology of eye disease and accelerate the development of patient-centered treatments is discussed.
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Tucker BA, Cranston CM, Anfinson KA, Shrestha S, Streb LM, Leon A, Mullins RF, Stone EM. Using patient-specific induced pluripotent stem cells to interrogate the pathogenicity of a novel retinal pigment epithelium-specific 65 kDa cryptic splice site mutation and confirm eligibility for enrollment into a clinical gene augmentation trial. Transl Res 2015; 166:740-749.e1. [PMID: 26364624 PMCID: PMC4702513 DOI: 10.1016/j.trsl.2015.08.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 08/18/2015] [Accepted: 08/24/2015] [Indexed: 01/07/2023]
Abstract
Retinal pigment epithelium-specific 65 kDa (RPE65)-associated Leber congenital amaurosis is an autosomal recessive disease that results in reduced visual acuity and night blindness beginning at birth. It is one of the few retinal degenerative disorders for which promising clinical gene transfer trials are currently underway. However, the ability to enroll patients in a gene augmentation trial is dependent on the identification of 2 bona fide disease-causing mutations, and there are some patients with the phenotype of RPE65-associated disease who might benefit from gene transfer but are ineligible because 2 disease-causing genetic variations have not yet been identified. Some such patients have novel mutations in RPE65 for which pathogenicity is difficult to confirm. The goal of this study was to determine if an intronic mutation identified in a 2-year-old patient with presumed RPE65-associated disease was truly pathogenic and grounds for inclusion in a clinical gene augmentation trial. Sequencing of the RPE65 gene revealed 2 mutations: (1) a previously identified disease-causing exonic leucine-to-proline mutation (L408P) and (2) a novel single point mutation in intron 3 (IVS3-11) resulting in an A>G change. RT-PCR analysis using RNA extracted from control human donor eye-derived primary RPE, control iPSC-RPE cells, and proband iPSC-RPE cells revealed that the identified IVS3-11 variation caused a splicing defect that resulted in a frameshift and insertion of a premature stop codon. In this study, we demonstrate how patient-specific iPSCs can be used to confirm pathogenicity of unknown mutations, which can enable positive clinical outcomes.
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Hazlewood RJ, Roos BR, Solivan-Timpe F, Honkanen RA, Jampol LM, Gieser SC, Meyer KJ, Mullins RF, Kuehn MH, Scheetz TE, Kwon YH, Alward WLM, Stone EM, Fingert JH. Heterozygous triplication of upstream regulatory sequences leads to dysregulation of matrix metalloproteinase 19 in patients with cavitary optic disc anomaly. Hum Mutat 2015; 36:369-78. [PMID: 25581579 DOI: 10.1002/humu.22754] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 12/23/2014] [Indexed: 11/06/2022]
Abstract
Patients with a congenital optic nerve disease, cavitary optic disc anomaly (CODA), are born with profound excavation of the optic nerve resembling glaucoma. We previously mapped the gene that causes autosomal-dominant CODA in a large pedigree to a chromosome 12q locus. Using comparative genomic hybridization and quantitative PCR analysis of this pedigree, we report identifying a 6-Kbp heterozygous triplication upstream of the matrix metalloproteinase 19 (MMP19) gene, present in all 17 affected family members and no normal members. Moreover, the triplication was not detected in 78 control subjects or in the Database of Genomic Variants. We further detected the same 6-Kbp triplication in one of 24 unrelated CODA patients and in none of 172 glaucoma patients. Analysis with a Luciferase assay showed that the 6-Kbp sequence has transcription enhancer activity. A 773-bp fragment of the 6-Kbp DNA segment increased downstream gene expression eightfold, suggesting that triplication of this sequence may lead to dysregulation of the downstream gene, MMP19, in CODA patients. Lastly, immunohistochemical analysis of human donor eyes revealed strong expression of MMP19 in optic nerve head. These data strongly suggest that triplication of an enhancer may lead to overexpression of MMP19 in the optic nerve that causes CODA.
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Cideciyan AV, Swider M, Schwartz SB, Stone EM, Jacobson SG. Predicting Progression of ABCA4-Associated Retinal Degenerations Based on Longitudinal Measurements of the Leading Disease Front. Invest Ophthalmol Vis Sci 2015; 56:5946-55. [PMID: 26377081 DOI: 10.1167/iovs.15-17698] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
PURPOSE To evaluate the progression of the earliest stage of disease in ABCA4-associated retinal degenerations (RDs). METHODS Near-infrared excited reduced-illuminance autofluorescence imaging was acquired across the retina up to 80 degrees eccentricity in 44 patients with two ABCA4 alleles. The eccentricity of the leading disease front (LDF) corresponding to the earliest stage of disease was measured along the four meridians. A mathematical model describing the expansion of the LDF was developed based on 6 years of longitudinal follow-up. RESULTS The extent of LDF along the superior, inferior, and temporal meridians showed a wide spectrum from 3.5 to 70 degrees. In patients with longitudinal data, the average centrifugal expansion rate was 2 degrees per year. The nasal extent of LDF between the fovea and ONH ranged from 4.3 to 16.5 degrees and expanded at 0.35 degrees per year. The extent of LDF beyond ONH ranged from 19 to 75 degrees and expanded on average at 2 degrees per year. A mathematical model fit well to the longitudinal data describing the expansion of the LDF. CONCLUSIONS The eccentricity of the LDF in ABCA4-RD shows a continuum from parafovea to far periphery along all four meridians consistent with a wide spectrum of severity observed clinically. The model of progression may provide a quantitative prediction of the LDF expansion based on the age and eccentricity of the LDF at a baseline visit, and thus contribute significantly to the enrollment of candidates appropriate for clinical trials planning specific interventions, efficacy outcomes, and durations.
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DeLuca AP, Weed MC, Haas CM, Halder JA, Stone EM. Apparent Usher Syndrome Caused by the Combination of BBS1-Associated Retinitis Pigmentosa and SLC26A4-Associated Deafness. JAMA Ophthalmol 2015; 133:967-8. [PMID: 26022370 DOI: 10.1001/jamaophthalmol.2015.1463] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Small KW, DeLuca AP, Whitmore SS, Rosenberg T, Silva-Garcia R, Udar N, Puech B, Garcia CA, Rice TA, Fishman GA, Héon E, Folk JC, Streb LM, Haas CM, Wiley LA, Scheetz TE, Fingert JH, Mullins RF, Tucker BA, Stone EM. North Carolina Macular Dystrophy Is Caused by Dysregulation of the Retinal Transcription Factor PRDM13. Ophthalmology 2015; 123:9-18. [PMID: 26507665 DOI: 10.1016/j.ophtha.2015.10.006] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 10/07/2015] [Accepted: 10/07/2015] [Indexed: 12/30/2022] Open
Abstract
PURPOSE To identify specific mutations causing North Carolina macular dystrophy (NCMD). DESIGN Whole-genome sequencing coupled with reverse transcription polymerase chain reaction (RT-PCR) analysis of gene expression in human retinal cells. PARTICIPANTS A total of 141 members of 12 families with NCMD and 261 unrelated control individuals. METHODS Genome sequencing was performed on 8 affected individuals from 3 families affected with chromosome 6-linked NCMD (MCDR1) and 2 individuals affected with chromosome 5-linked NCMD (MCDR3). Variants observed in the MCDR1 locus with frequencies <1% in published databases were confirmed using Sanger sequencing. Confirmed variants absent from all published databases were sought in 8 additional MCDR1 families and 261 controls. The RT-PCR analysis of selected genes was performed in stem cell-derived human retinal cells. MAIN OUTCOME MEASURES Co-segregation of rare genetic variants with disease phenotype. RESULTS Five sequenced individuals with MCDR1-linked NCMD shared a haplotype of 14 rare variants spanning 1 Mb of the disease-causing allele. One of these variants (V1) was absent from all published databases and all 261 controls, but was found in 5 additional NCMD kindreds. This variant lies in a DNase 1 hypersensitivity site (DHS) upstream of both the PRDM13 and CCNC genes. Sanger sequencing of 1 kb centered on V1 was performed in the remaining 4 NCMD probands, and 2 additional novel single nucleotide variants (V2 in 3 families and V3 in 1 family) were identified in the DHS within 134 bp of the location of V1. A complete duplication of the PRDM13 gene was also discovered in a single family (V4). The RT-PCR analysis of PRDM13 expression in developing retinal cells revealed marked developmental regulation. Next-generation sequencing of 2 individuals with MCDR3-linked NCMD revealed a 900-kb duplication that included the entire IRX1 gene (V5). The 5 mutations V1 to V5 segregated perfectly in the 102 affected and 39 unaffected members of the 12 NCMD families. CONCLUSIONS We identified 5 rare mutations, each capable of arresting human macular development. Four of these strongly implicate the involvement of PRDM13 in macular development, whereas the pathophysiologic mechanism of the fifth remains unknown but may involve the developmental dysregulation of IRX1.
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DeLuca AP, Whitmore SS, Barnes J, Sharma TP, Westfall TA, Scott CA, Weed MC, Wiley JS, Wiley LA, Johnston RM, Schnieders MJ, Lentz SR, Tucker BA, Mullins RF, Scheetz TE, Stone EM, Slusarski DC. Hypomorphic mutations in TRNT1 cause retinitis pigmentosa with erythrocytic microcytosis. Hum Mol Genet 2015; 25:44-56. [PMID: 26494905 DOI: 10.1093/hmg/ddv446] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 10/19/2015] [Indexed: 02/07/2023] Open
Abstract
Retinitis pigmentosa (RP) is a highly heterogeneous group of disorders characterized by degeneration of the retinal photoreceptor cells and progressive loss of vision. While hundreds of mutations in more than 100 genes have been reported to cause RP, discovering the causative mutations in many patients remains a significant challenge. Exome sequencing in an individual affected with non-syndromic RP revealed two plausibly disease-causing variants in TRNT1, a gene encoding a nucleotidyltransferase critical for tRNA processing. A total of 727 additional unrelated individuals with molecularly uncharacterized RP were completely screened for TRNT1 coding sequence variants, and a second family was identified with two members who exhibited a phenotype that was remarkably similar to the index patient. Inactivating mutations in TRNT1 have been previously shown to cause a severe congenital syndrome of sideroblastic anemia, B-cell immunodeficiency, recurrent fevers and developmental delay (SIFD). Complete blood counts of all three of our patients revealed red blood cell microcytosis and anisocytosis with only mild anemia. Characterization of TRNT1 in patient-derived cell lines revealed reduced but detectable TRNT1 protein, consistent with partial function. Suppression of trnt1 expression in zebrafish recapitulated several features of the human SIFD syndrome, including anemia and sensory organ defects. When levels of trnt1 were titrated, visual dysfunction was found in the absence of other phenotypes. The visual defects in the trnt1-knockdown zebrafish were ameliorated by the addition of exogenous human TRNT1 RNA. Our findings indicate that hypomorphic TRNT1 mutations can cause a recessive disease that is almost entirely limited to the retina.
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Mears K, Bakall B, Harney LA, Penticoff JA, Stone EM. Autosomal Dominant Microcephaly Associated With Congenital Lymphedema and Chorioretinopathy Due to a Novel Mutation in KIF11. JAMA Ophthalmol 2015; 133:720-1. [PMID: 25764055 DOI: 10.1001/jamaophthalmol.2015.199] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Bax NM, Sangermano R, Roosing S, Thiadens AAHJ, Hoefsloot LH, van den Born LI, Phan M, Klevering BJ, Westeneng-van Haaften C, Braun TA, Zonneveld-Vrieling MN, de Wijs I, Mutlu M, Stone EM, den Hollander AI, Klaver CCW, Hoyng CB, Cremers FPM. Heterozygous deep-intronic variants and deletions in ABCA4 in persons with retinal dystrophies and one exonic ABCA4 variant. Hum Mutat 2015; 36:43-7. [PMID: 25363634 DOI: 10.1002/humu.22717] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 10/18/2014] [Indexed: 11/05/2022]
Abstract
Variants in ABCA4 are responsible for autosomal-recessive Stargardt disease and cone-rod dystrophy. Sequence analysis of ABCA4 exons previously revealed one causative variant in each of 45 probands. To identify the "missing" variants in these cases, we performed multiplex ligation-dependent probe amplification-based deletion scanning of ABCA4. In addition, we sequenced the promoter region, fragments containing five deep-intronic splice variants, and 15 deep-intronic regions containing weak splice sites. Heterozygous deletions spanning ABCA4 exon 5 or exons 20-22 were found in two probands, heterozygous deep-intronic variants were identified in six probands, and a deep-intronic variant was found together with an exon 20-22 deletion in one proband. Based on ophthalmologic findings and characteristics of the identified exonic variants present in trans, the deep-intronic variants V1 and V4 were predicted to be relatively mild and severe, respectively. These findings are important for proper genetic counseling and for the development of variant-specific therapies.
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Khorram D, Choi M, Roos BR, Stone EM, Kopel T, Allen R, Alward WL, Scheetz TE, Fingert JH. Novel TMEM98 mutations in pedigrees with autosomal dominant nanophthalmos. Mol Vis 2015; 21:1017-23. [PMID: 26392740 PMCID: PMC4556162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 09/01/2015] [Indexed: 11/17/2022] Open
Abstract
PURPOSE Autosomal dominant nanophthalmos is an inherited eye disorder characterized by a structurally normal but smaller eye. Patients with nanophthalmos have high hyperopia (far-sightedness), a greater incidence of angle-closure glaucoma, and increased risk of surgical complications. In this study, the clinical features and the genetic basis of nanophthalmos were investigated in two large autosomal dominant nanophthalmos pedigrees. METHODS Fourteen members of a Caucasian pedigree from the United States and 15 members of a pedigree from the Mariana Islands enrolled in a genetic study of nanophthalmos and contributed DNA samples. Twenty of 29 family members underwent eye examinations that included measurement of axial eye length and/or refractive error. The genetic basis of nanophthalmos in the pedigrees was studied with linkage analysis, whole exome sequencing, and candidate gene (i.e., TMEM98) sequencing to identify the nanophthalmos-causing gene. RESULTS Nine members of the pedigree from the United States and 11 members of the pedigree from the Mariana Islands were diagnosed with nanophthalmos that is transmitted as an autosomal dominant trait. The patients with nanophthalmos had abnormally short axial eye lengths, which ranged from 15.9 to 18.4 mm. Linkage analysis of the nanophthalmos pedigree from the United States identified nine large regions of the genome (greater than 10 Mbp) that were coinherited with disease in this family. Genes within these "linked regions" were examined for disease-causing mutations using exome sequencing, and a His196Pro mutation was detected in the TMEM98 gene, which was recently reported to be a nanophthalmos gene. Sanger sequencing subsequently showed that all other members of this pedigree with nanophthalmos also carry the His196Pro TMEM98 mutation. Testing the Mariana Islands pedigree for TMEM98 mutations identified a 34 bp heterozygous deletion that spans the 3' end of exon 4 in all affected family members. Neither TMEM98 mutation was detected in public exome sequence databases. CONCLUSIONS A recent report identified a single TMEM98 missense mutation in a nanophthalmos pedigree. Our discovery of two additional TMEM98 mutations confirms the important role of the gene in the pathogenesis of autosomal dominant nanophthalmos.
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Abstract
Age-related macular degeneration is a very common condition that is caused by a complex interplay of genetic and environmental factors. It is likely that, in the future, genetic testing will allow physicians to achieve better clinical outcomes by administering specific treatments to patients based on their genotypes. However, improved outcomes for genotyped patients have not yet been demonstrated in a prospective clinical trial, and as a result, the costs and risks of routine genetic testing currently outweigh the benefits for patients with age-related macular degeneration.
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Shankar SP, Birch DG, Ruiz RS, Hughbanks-Wheaton DK, Sullivan LS, Bowne SJ, Stone EM, Daiger SP. Founder Effect of a c.828+3A>T Splice Site Mutation in Peripherin 2 (PRPH2) Causing Autosomal Dominant Retinal Dystrophies. JAMA Ophthalmol 2015; 133:511-7. [PMID: 25675413 DOI: 10.1001/jamaophthalmol.2014.6115] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
IMPORTANCE Screening for splice site mutation c.828+3A>T in the peripherin 2 (PRPH2) gene should be a high priority in families with highly variable retinal dystrophies. The correction of missplicing is a potential therapeutic target. OBJECTIVE To determine the prevalence, genetic origin, and molecular mechanism of a donor c.828+3A>T mutation in the PRPH2 (peripherin 2, retinal degeneration slow) gene in individuals with retinal dystrophies. DESIGN, SETTING, AND PARTICIPANTS Case-control study that took place at the University of Texas Health Science Center, the University of Iowa, and the Retina Foundation of the Southwest, from January 1, 1987, to August 1, 2014, including affected individuals from 200 families with a diagnosis of autosomal dominant retinitis pigmentosa, 35 families with unspecified macular dystrophies, and 116 families with pattern dystrophy. Participants were screened for the c.828+3A>T mutation by restriction-enzyme digest, single-strand conformational polymorphism screening, or bidirectional sequencing. Haplotypes of polymorphic markers flanking the PRPH2 locus and sequence variants within the gene were determined by denaturing gel electrophoresis or automated capillary-based cycle sequencing. The effect of the splice site mutation on the PRPH2 transcript was analyzed using NetGene2, a splice prediction program and by the reverse transcription polymerase chain reaction of illegitimate transcripts from peripheral white blood cells. MAIN OUTCOMES AND MEASURES Results of testing for splice site mutation, haplotypes, and alternate transcripts. RESULTS The PRPH2 mutation was found in 97 individuals of 19 independently ascertained families with a clinical diagnosis of retinitis pigmentosa, macular dystrophy, and/or pattern dystrophy. All affected individuals also shared a rare haplotype of approximately 644 kilobase pairs containing the c.828+3A>T mutation, which extends from the short tandem repeat polymorphism D6S282 to c.1013G>A (rs434102, a single-nucleotide polymorphism) in exon 3 of PRPH2, suggesting this mutation is from a common ancestor and is a founder mutation. It has a prevalence of 2% in families diagnosed as having autosomal dominant retinitis pigmentosa and 10% in families with variable clinical diagnosis of pattern, macular, and retinal dystrophies. Individuals with the c.828+3A>T mutation expressed a PRPH2 transcript not found in control participants and that was consistent with abnormal splicing. CONCLUSIONS AND RELEVANCE The PRPH2 c.828+3A>T splice site mutation is a frequent cause of inherited retinal dystrophies and is owing to the founder effect. The likely cause of disease is the missplicing of the PRPH2 message that results in a truncated protein product. Identifying the genetic etiology assists in more accurate management and possible future therapeutic options.
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Zode GS, Kuehn MH, Nishimura DY, Searby CC, Mohan K, Grozdanic SD, Bugge K, Anderson MG, Clark AF, Stone EM, Sheffield VC. Reduction of ER stress via a chemical chaperone prevents disease phenotypes in a mouse model of primary open angle glaucoma. J Clin Invest 2015; 125:3303. [PMID: 26237042 DOI: 10.1172/jci82799] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Sohn EH, Jiao C, Kaalberg E, Cranston C, Mullins RF, Stone EM, Tucker BA. Allogenic iPSC-derived RPE cell transplants induce immune response in pigs: a pilot study. Sci Rep 2015; 5:11791. [PMID: 26138532 PMCID: PMC4490339 DOI: 10.1038/srep11791] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 06/05/2015] [Indexed: 12/21/2022] Open
Abstract
Stem cell strategies focused on replacement of RPE cells for the treatment of geographic atrophy are under intense investigation. Although the eye has long been considered immune privileged, there is limited information about the immune response to transplanted cells in the subretinal space of large animals. The purpose of this study was to evaluate the survival of allogenic induced pluripotent stem cell-derived RPE cells (iPSC-RPE) delivered to the subretinal space of the pig as well as determine whether these cells induce an immune response in non-diseased eyes. GFP positive iPSC-RPE, generated from outbred domestic swine, were injected into the subretinal space of vitrectomized miniature swine. Control eyes received vehicle only. GFP positive iPSC-RPE cells were identified in the subretinal space 3 weeks after injection in 5 of 6 eyes. Accompanying GFP-negative cells positive for IgG, CD45 and macrophage markers were also identified in close proximity to the injected iPSC-RPE cells. All subretinal cells were negative for GFAP as well as cell cycle markers. We found that subretinal injection of allogenic iPSC-RPE cells into wild-type mini-pigs can induce the innate immune response. These findings suggest that immunologically matched or autologous donor cells should be considered for clinical RPE cell replacement.
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Almeida DRP, Zhang L, Chin EK, Mullins RF, Kucukevcilioglu M, Critser DB, Sonka M, Stone EM, Folk JC, Abràmoff MD, Russell SR. Comparison of retinal and choriocapillaris thicknesses following sitting to supine transition in healthy individuals and patients with age-related macular degeneration. JAMA Ophthalmol 2015; 133:297-303. [PMID: 25521616 PMCID: PMC5777152 DOI: 10.1001/jamaophthalmol.2014.5168] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
IMPORTANCE The effects of position on retinal and choroidal structure are absent from the literature yet may provide insights into disease states such as age-related macular degeneration (AMD). OBJECTIVE To evaluate the effect of postural change on retinal and choroidal structures in healthy volunteers and patients with non-neovascular AMD. DESIGN, SETTING, AND PARTICIPANTS Prospective observational case series at an academic tertiary care retina service from September 2013 to April 2014 involving 4 unaffected volunteers (8 eyes) and 7 patients (8 eyes) with intermediate AMD. Healthy volunteers selected for the study had no evidence of ocular disease. Patients with AMD were required to have at least 10 intermediate-sized drusen. EXPOSURES Spectral-domain optical coherence tomography with enhanced depth imaging in upright (sitting) and supine positions. Stable imaging was achieved using a rotating adjustable mechanical arm that we constructed to allow the optical coherence tomography transducer to rotate 90°. The Iowa Reference Algorithms were used to quantify choroid and choriocapillaris thicknesses. MAIN OUTCOMES AND MEASURES Changes in sitting and supine position central macular thickness (in micrometers), total macular volume (in cubic millimeters), choroidal thickness (in micrometers), and choriocapillaris-equivalent thickness (CCET, in micrometers). RESULTS Choriocapillaris-equivalent thickness was thinner in healthy participants (9.89 μm; range, 7.15-12.5 μm) compared with patients with intermediate AMD (16.73 μm; range, 10.31-27.38 μm) (P = .02); there was no difference in overall choroidal thickness between the 2 groups (P = .38). There was a 15% CCET reduction among healthy participants when transitioning from a sitting (9.89 μm) to supine (8.4 μm; range, 6.92-10.7 μm) position (P = .02) vs a CCET reduction of 11.1% from sitting (16.73 μm) to supine (14.88 μm; range, 8.76-20.8 μm) positioning (P = .10) in patients with intermediate AMD. CONCLUSIONS AND RELEVANCE Intermediate AMD appears to be associated with an increase in CCET and with a lack of positional responses that are observed in the CCET of normal eyes. Our results suggest that although outer portions of the choroid do not appear to be responsive to modest positional or hydrostatic pressure, the choriocapillaris capacity is, and this is measurable in vivo. Whether this physiologic deviation that occurs in AMD is related to atrophy, inflammation, or changes in autoregulatory factors or growth factors remains to be determined.
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Whitmore SS, Sohn EH, Chirco KR, Drack AV, Stone EM, Tucker BA, Mullins RF. Complement activation and choriocapillaris loss in early AMD: implications for pathophysiology and therapy. Prog Retin Eye Res 2015; 45:1-29. [PMID: 25486088 PMCID: PMC4339497 DOI: 10.1016/j.preteyeres.2014.11.005] [Citation(s) in RCA: 159] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 11/19/2014] [Accepted: 11/25/2014] [Indexed: 12/24/2022]
Abstract
Age-related macular degeneration (AMD) is a common and devastating disease that can result in severe visual dysfunction. Over the last decade, great progress has been made in identifying genetic variants that contribute to AMD, many of which lie in genes involved in the complement cascade. In this review we discuss the significance of complement activation in AMD, particularly with respect to the formation of the membrane attack complex in the aging choriocapillaris. We review the clinical, histological and biochemical data that indicate that vascular loss in the choroid occurs very early in the pathogenesis of AMD, and discuss the potential impact of vascular dropout on the retinal pigment epithelium, Bruch's membrane and the photoreceptor cells. Finally, we present a hypothesis for the pathogenesis of early AMD and consider the implications of this model on the development of new therapies.
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Zhang N, Tsybovsky Y, Kolesnikov AV, Rozanowska M, Swider M, Schwartz SB, Stone EM, Palczewska G, Maeda A, Kefalov VJ, Jacobson SG, Cideciyan AV, Palczewski K. Protein misfolding and the pathogenesis of ABCA4-associated retinal degenerations. Hum Mol Genet 2015; 24:3220-37. [PMID: 25712131 DOI: 10.1093/hmg/ddv073] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 02/22/2015] [Indexed: 12/13/2022] Open
Abstract
Mutations in the ABCA4 gene are a common cause of autosomal recessive retinal degeneration. All mouse models to date are based on knockouts of Abca4, even though the disease is often caused by missense mutations such as the complex allele L541P;A1038V (PV). We now show that the PV mutation causes severe human disease whereas the V mutation alone causes mild disease. Mutant ABCA4 proteins expressed heterologously in mammalian cells retained normal cellular localization. However, basal and all-trans-retinal-stimulated ATPase activities were reduced substantially for P and PV but only mildly for V. Electron microscopy revealed marked structural changes and misfolding for the P and PV mutants but few changes for the V mutant, consistent with the disease severity difference in patients. We generated Abca4(PV/PV) knock-in mice homozygous for the complex PV allele to investigate the effects of this misfolding mutation in vivo. Mutant ABCA4 RNA levels approximated WT ABCA4 RNA levels but, surprisingly, only trace amounts of mutant ABCA4 protein were noted in the retina. RNA sequencing of WT, Abca4(-/-) and Abca4(PV/PV) mice revealed mild gene expression alterations in the retina and RPE. Similar to Abca4(-/-) mice, Abca4(PV/PV) mice showed substantial A2E and lipofuscin accumulation in their RPE cells but no retinal degeneration up to 12 months of age. Thus, rapid degradation of this large misfolded mutant protein in mouse retina caused little detectable photoreceptor degeneration. These findings suggest likely differences in the unfolded protein response between murine and human photoreceptors and support development of therapies directed at increasing this capability in patients.
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Sohn EH, Wang K, Thompson S, Riker MJ, Hoffmann JM, Stone EM, Mullins RF. Comparison of drusen and modifying genes in autosomal dominant radial drusen and age-related macular degeneration. Retina 2015; 35:48-57. [PMID: 25077532 PMCID: PMC5513174 DOI: 10.1097/iae.0000000000000263] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Autosomal dominant radial drusen (ADRD), also termed Malattia Leventinese and Doyne honeycomb retinal dystrophy, causes early-onset vision loss because of mutation in EFEMP1. Drusen in an exceedingly rare ADRD human donor eye was compared with eyes affected with age-related macular degeneration (AMD). This study also elucidated whether variations in high-risk AMD genotypes modify phenotypic severity of ADRD. METHODS Morphologic and histochemical analyses of drusen in one ADRD donor and seven AMD donors. Evaluation of complement factor H (CFH) and ARMS2/HTRA1 alleles in a cohort of 25 subjects with ADRD. RESULTS Autosomal dominant radial drusen had unique onion skin-like lamination but otherwise shared many compositional features with hard, nodular drusen and/or diffuse soft drusen with basal deposits. Autosomal dominant radial drusen also possessed collagen type IV, an extracellular matrix protein that is absent in age-related drusen. Antibodies directed against the membrane attack complex showed robust labeling of ADRD. Vitronectin and amyloid P were present in drusen of both types. High-risk alleles in the CFH and ARMS2/HTRA1 genes were not associated with increasing ADRD severity. CONCLUSION Drusen from ADRD and AMD exhibit overlap of some major constituents, but ADRD exhibit distinct alterations in the extracellular matrix that are absent in AMD.
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Wiley LA, Burnight ER, Mullins RF, Stone EM, Tucker BA. Stem cells as tools for studying the genetics of inherited retinal degenerations. Cold Spring Harb Perspect Med 2014; 5:a017160. [PMID: 25502747 DOI: 10.1101/cshperspect.a017160] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The ability to provide early clinical intervention for inherited disorders is heavily dependent on knowledge of a patient's disease-causing mutations and the resultant pathophysiologic mechanism(s). Without knowing a patient's disease-causing gene, and how gene mutations alter the health and functionality of affected cells, it would be difficult to develop and deliver patient-specific molecular or small molecule therapies. Many believe that the field of stem cell biology holds the keys to the future development of disease-, patient-, and cell-specific therapies. In the case of the eye, which is susceptible to an extremely common late-onset degenerative disease known as age-related macular degeneration, stem cell-based therapies could increase the quality of life for millions of patients worldwide. Furthermore, autologous, patient-specific induced pluripotent stem cells could be a viable source to treat rare Mendelian retinal degenerative diseases such as retinitis pigmentosa, Stargardt disease, and Best disease, to name a few.
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