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Colombo L, Bonetti G, Maltese PE, Iarossi G, Ziccardi L, Fogagnolo P, De Ruvo V, Murro V, Giorgio D, Falsini B, Placidi G, Martella S, Galantin E, Bertelli M, Rossetti L. Genotypic and Phenotypic Characterization of a Cohort of Patients Affected by Rod Cyclic Nucleotide Channel-Associated Retinitis Pigmentosa. Ophthalmic Res 2024; 67:301-310. [PMID: 38705136 DOI: 10.1159/000538746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 03/12/2024] [Indexed: 05/07/2024]
Abstract
INTRODUCTION Retinitis pigmentosa (RP), a heterogeneous inherited retinal disorder causing gradual vision loss, affects over 1 million people worldwide. Pathogenic variants in CNGA1 and CNGB1 genes, respectively, accounting for 1% and 4% of cases, impact the cyclic nucleotide-gated channel in rod photoreceptor cells. The aim of this study was to describe and compare genotypic and clinical characteristics of a cohort of patients with CNGA1- or CNGB1-related RP and to explore potential genotype-phenotype correlations. METHODS The following data from patients with CNGA1- or CNGB1-related RP, followed in five Italian inherited retinal degenerations services, were retrospectively collected: genetic variants in CNGA1 and CNGB1, best-corrected visual acuity (BCVA), ellipsoid zone (EZ) width, fundus photographs, and short-wavelength fundus autofluorescence (SW-AF) images. Comparisons and correlation analyses were performed by first dividing the cohort in two groups according to the gene responsible for the disease (CNGA1 and CNGB1 groups). In parallel, the whole cohort of RP patients was divided into two other groups, according to the expected impact of the variants at protein level (low and high group). RESULTS In total, 29 patients were recruited, 11 with CNGA1- and 18 with CNGB1-related RP. In both CNGA1 and CNGB1, 5 novel variants in CNGA1 and 5 in CNGB1 were found. BCVA was comparable between CNGA1 and CNGB1 groups, as well as between low and high groups. CNGA1 group had a larger mean EZ width compared to CNGB1 group, albeit not statistically significant, while EZ width did not differ between low and high groups A statistically significant correlation between EZ width and BCVA as well as between EZ width and age were observed in the whole cohort of RP patients. Fundus photographs of all patients in the cohort showed classic RP pattern, and in SW-AF images an hyperautofluorescent ring was observed in 14/21 patients. CONCLUSION Rod CNG channel-associated RP was demonstrated to be a slowly progressive disease in both CNGA1- and CNGB1-related forms, making it an ideal candidate for gene augmentation therapies.
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Affiliation(s)
- Leonardo Colombo
- Department of Ophthalmology, ASST Santi Paolo e Carlo Hospital, University of Milan, Milan, Italy
| | - Gabriele Bonetti
- MAGI'S LAB S.R.L., Rovereto, Italy
- Department of Pharmaceutical Sciences, University of Perugia, Perugia, Italy
| | | | - Giancarlo Iarossi
- Department of Ophthalmology, Bambino Gesù Children's Hospital, Rome, Italy
| | | | - Paolo Fogagnolo
- Department of Ophthalmology, ASST Santi Paolo e Carlo Hospital, University of Milan, Milan, Italy
| | - Valentino De Ruvo
- Department of Ophthalmology, ASST Santi Paolo e Carlo Hospital, University of Milan, Milan, Italy
| | - Vittoria Murro
- Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy
| | - Dario Giorgio
- Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy
| | - Benedetto Falsini
- Department of Ophthalmology, Bambino Gesù Children's Hospital, Rome, Italy
- Ophthalmology Unit, Fondazione Policlinico Universitario "A. Gemelli" IRCCS/Università Cattolica del S. Cuore, Rome, Italy
| | - Giorgio Placidi
- Ophthalmology Unit, Fondazione Policlinico Universitario "A. Gemelli" IRCCS/Università Cattolica del S. Cuore, Rome, Italy
| | - Salvatore Martella
- Department of Ophthalmology, ASST Santi Paolo e Carlo Hospital, University of Milan, Milan, Italy
| | - Eleonora Galantin
- Department of Ophthalmology, ASST Santi Paolo e Carlo Hospital, University of Milan, Milan, Italy
| | - Matteo Bertelli
- MAGI'S LAB S.R.L., Rovereto, Italy
- MAGI EUREGIO, Bolzano, Italy
- MAGISNAT, Atlanta Tech Park, Peachtree Corners, Georgia, USA
| | - Luca Rossetti
- Department of Ophthalmology, ASST Santi Paolo e Carlo Hospital, University of Milan, Milan, Italy
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Kolesnikov AV, Murphy DP, Corbo JC, Kefalov VJ. Germline knockout of Nr2e3 protects photoreceptors in three distinct mouse models of retinal degeneration. Proc Natl Acad Sci U S A 2024; 121:e2316118121. [PMID: 38442152 PMCID: PMC10945761 DOI: 10.1073/pnas.2316118121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Accepted: 01/17/2024] [Indexed: 03/07/2024] Open
Abstract
Retinitis pigmentosa (RP) is a common form of retinal dystrophy that can be caused by mutations in any one of dozens of rod photoreceptor genes. The genetic heterogeneity of RP represents a significant challenge for the development of effective therapies. Here, we present evidence for a potential gene-independent therapeutic strategy based on targeting Nr2e3, a transcription factor required for the normal differentiation of rod photoreceptors. Nr2e3 knockout results in hybrid rod photoreceptors that express the full complement of rod genes, but also a subset of cone genes. We show that germline deletion of Nr2e3 potently protects rods in three mechanistically diverse mouse models of retinal degeneration caused by bright-light exposure (light damage), structural deficiency (rhodopsin-deficient Rho-/- mice), or abnormal phototransduction (phosphodiesterase-deficient rd10 mice). Nr2e3 knockout confers strong neuroprotective effects on rods without adverse effects on their gene expression, structure, or function. Furthermore, in all three degeneration models, prolongation of rod survival by Nr2e3 knockout leads to lasting preservation of cone morphology and function. These findings raise the possibility that upregulation of one or more cone genes in Nr2e3-deficient rods may be responsible for the neuroprotective effects we observe.
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Affiliation(s)
- Alexander V. Kolesnikov
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, CA92697
| | - Daniel P. Murphy
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO63110
| | - Joseph C. Corbo
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO63110
| | - Vladimir J. Kefalov
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, CA92697
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Gerhardt MJ, Petersen-Jones SM, Michalakis S. CNG channel-related retinitis pigmentosa. Vision Res 2023; 208:108232. [PMID: 37054604 PMCID: PMC10373105 DOI: 10.1016/j.visres.2023.108232] [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: 02/13/2023] [Revised: 03/27/2023] [Accepted: 03/27/2023] [Indexed: 04/15/2023]
Abstract
The genes CNGA1 and CNGB1 encode the alpha and beta subunits of the rod CNG channel, a ligand-gated cation channel whose activity is controlled by cyclic guanosine monophosphate (cGMP). Autosomal inherited mutations in either of the genes lead to a progressive rod-cone retinopathy known as retinitis pigmentosa (RP). The rod CNG channel is expressed in the plasma membrane of the outer segment and functions as a molecular switch that converts light-mediated changes in cGMP into a voltage and Ca2+ signal. Here, we will first review the molecular properties and physiological role of the rod CNG channel and then discuss the characteristics of CNG-related RP. Finally, we will summarize recent activities in the field of gene therapy aimed at developing therapies for CNG-related RP.
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Affiliation(s)
- Maximilian J Gerhardt
- Department of Ophthalmology, University Hospital, LMU Munich, Mathildenstraße 8, 80336 München, Germany
| | - Simon M Petersen-Jones
- College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, United States
| | - Stylianos Michalakis
- Department of Ophthalmology, University Hospital, LMU Munich, Mathildenstraße 8, 80336 München, Germany.
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Biology, Pathobiology and Gene Therapy of CNG Channel-Related Retinopathies. Biomedicines 2023; 11:biomedicines11020269. [PMID: 36830806 PMCID: PMC9953513 DOI: 10.3390/biomedicines11020269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 01/16/2023] [Accepted: 01/17/2023] [Indexed: 01/21/2023] Open
Abstract
The visual process begins with the absorption of photons by photopigments of cone and rod photoreceptors in the retina. In this process, the signal is first amplified by a cyclic guanosine monophosphate (cGMP)-based signaling cascade and then converted into an electrical signal by cyclic nucleotide-gated (CNG) channels. CNG channels are purely ligand-gated channels whose activity can be controlled by cGMP, which induces a depolarizing Na+/Ca2+ current upon binding to the channel. Structurally, CNG channels belong to the superfamily of pore-loop cation channels and share structural similarities with hyperpolarization-activated cyclic nucleotide (HCN) and voltage-gated potassium (KCN) channels. Cone and rod photoreceptors express distinct CNG channels encoded by homologous genes. Mutations in the genes encoding the rod CNG channel (CNGA1 and CNGB1) result in retinitis-pigmentosa-type blindness. Mutations in the genes encoding the cone CNG channel (CNGA3 and CNGB3) lead to achromatopsia. Here, we review the molecular properties of CNG channels and describe their physiological and pathophysiological roles in the retina. Moreover, we summarize recent activities in the field of gene therapy aimed at developing the first gene therapies for CNG channelopathies.
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Optimizing ERG Measures of Scotopic and Photopic Critical Flicker Frequency. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018. [PMID: 29721938 DOI: 10.1007/978-3-319-75402-4_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register]
Abstract
A visual response to flickering light requires complex retinal computation, and thus ERG measures are an excellent test of retinal circuit fidelity. Critical flicker frequency (CFF) is the frequency at which the retinal response is no longer modulated. Traditionally, CFF is obtained with a series of steady flicker stimuli with increasing frequencies. However, this method is slow and susceptible to experimental drift and/or adaptational effects. The current study compares the steady flicker method to CFF measurements obtained using a frequency sweep protocol. We introduce a light source programmed to produce a linear sweep of frequencies in a single trial. Using the traditional steady flicker method and a criterion response of 3 μV, we obtained a scotopic CFF of 18.4 ± 0.66 Hz and a photopic CFF of 44.4 ± 1.67 Hz. Our sweep flicker method, used on the same animals, produces a waveform best analyzed by Fourier transform; wherein a 6.18 log μV2 threshold was found to yield CFF values equal to those of the steady flicker method. Thus, the two flicker ERG techniques give comparable results, under both dark- and light-adapted conditions, and the flicker sweep method is faster to administer and analyze and may be less susceptible to blinking, breathing, and eye movement artifacts.
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Chakraborty D, Conley SM, Pittler SJ, Naash MI. Role of RDS and Rhodopsin in Cngb1-Related Retinal Degeneration. Invest Ophthalmol Vis Sci 2016; 57:787-97. [PMID: 26934134 PMCID: PMC4777275 DOI: 10.1167/iovs.15-18516] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Rod photoreceptor outer segment (OS) morphogenesis, structural integrity, and proper signal transduction rely on critical proteins found in the different OS membrane domains (e.g., plasma, disc, and disc rim membrane). Among these key elements are retinal degeneration slow (RDS, also known as peripherin-2), rhodopsin, and the beta subunit of the cyclic nucleotide gated channel (CNGB1a), which have been found to interact in a complex. The purpose of this study was to evaluate the potential interplay between these three proteins by examining retinal disease phenotypes in animal models expressing varying amounts of CNGB1a, rhodopsin, and RDS. Methods Outer segment trafficking, retinal function, and photoreceptor structure were evaluated using knockout mouse lines. Results Eliminating Cngb1 and reducing RDS leads to additive defects in RDS expression levels and rod electroretinogram (ERG) function, (e.g., Cngb1−/−/rds+/− versus rds+/− or Cngb1−/−) but not to additive defects in rod ultrastructure. These additive effects also manifested in cone function: Photopic ERG responses were significantly lower in the Cngb1−/−/rds+/− versus rds+/− or Cngb1−/−, suggesting that eliminating Cngb1 can accelerate the cone degeneration that usually presents later in the rds+/−. This was not the case with rhodopsin; reducing rhodopsin levels in concert with eliminating CNGB1a did not lead to phenotypes more severe than those observed in the Cngb1 knockout alone. Conclusions These data support a role for RDS as the core component of a multiprotein plasma membrane-rim-disc complex that has both a structural role in photoreceptor OS formation and maintenance and a functional role in orienting proteins for optimal signal transduction.
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Affiliation(s)
- Dibyendu Chakraborty
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Steven J Pittler
- Department of Vision Sciences, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States
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Uversky VN. The alphabet of intrinsic disorder: II. Various roles of glutamic acid in ordered and intrinsically disordered proteins. INTRINSICALLY DISORDERED PROTEINS 2013; 1:e24684. [PMID: 28516010 PMCID: PMC5424795 DOI: 10.4161/idp.24684] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 03/27/2013] [Accepted: 04/12/2013] [Indexed: 11/19/2022]
Abstract
The ability of a protein to fold into unique functional state or to stay intrinsically disordered is encoded in its amino acid sequence. Both ordered and intrinsically disordered proteins (IDPs) are natural polypeptides that use the same arsenal of 20 proteinogenic amino acid residues as their major building blocks. The exceptional structural plasticity of IDPs, their capability to exist as heterogeneous structural ensembles and their wide array of important disorder-based biological functions that complements functional repertoire of ordered proteins are all rooted within the peculiar differential usage of these building blocks by ordered proteins and IDPs. In fact, some residues (so-called disorder-promoting residues) are noticeably more common in IDPs than in sequences of ordered proteins, which, in their turn, are enriched in several order-promoting residues. Furthermore, residues can be arranged according to their “disorder promoting potencies,” which are evaluated based on the relative abundances of various amino acids in ordered and disordered proteins. This review continues a series of publications on the roles of different amino acids in defining the phenomenon of protein intrinsic disorder and concerns glutamic acid, which is the second most disorder-promoting residue.
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Affiliation(s)
- Vladimir N Uversky
- Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute; College of Medicine; University of South Florida; Tampa, FL USA.,Institute for Biological Instrumentation; Russian Academy of Sciences; Moscow, Russia
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