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de Guimaraes TAC, Georgiou M, Robson AG, Fujinami K, Vincent A, Nasser F, Khateb S, Mahroo OA, Pontikos N, Vargas ME, Thiadens AAHJ, Carvalho ERD, Nguyen XTA, Arno G, Fujinami-Yokokawa Y, Liu X, Tsunoda K, Hayashi T, Jiménez-Rolando B, Martin-Merida MI, Avila-Fernandez A, Salas EC, Garcia-Sandoval B, Ayuso C, Sharon D, Kohl S, Huckfeldt RM, Banin E, Pennesi ME, Khan AO, Wissinger B, Webster AR, Heon E, Boon CJF, Zrenner E, Michaelides M. KCNV2-associated retinopathy: genotype-phenotype correlations - KCNV2 study group report 3. Br J Ophthalmol 2024; 108:1137-1144. [PMID: 37852740 DOI: 10.1136/bjo-2023-323640] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 09/15/2023] [Indexed: 10/20/2023]
Abstract
BACKGROUND/AIMS To investigate genotype-phenotype associations in patients with KCNV2 retinopathy. METHODS Review of clinical notes, best-corrected visual acuity (BCVA), molecular variants, electroretinography (ERG) and retinal imaging. Subjects were grouped according to the combination of KCNV2 variants-two loss-of-function (TLOF), two missense (TM) or one of each (MLOF)-and parameters were compared. RESULTS Ninety-two patients were included. The mean age of onset (mean±SD) in TLOF (n=55), TM (n=23) and MLOF (n=14) groups was 3.51±0.58, 4.07±2.76 and 5.54±3.38 years, respectively. The mean LogMAR BCVA (±SD) at baseline in TLOF, TM and MLOF groups was 0.89±0.25, 0.67±0.38 and 0.81±0.35 for right, and 0.88±0.26, 0.69±0.33 and 0.78±0.33 for left eyes, respectively. The difference in BCVA between groups at baseline was significant in right (p=0.03) and left eyes (p=0.035). Mean outer nuclear layer thickness (±SD) at baseline in TLOF, MLOF and TM groups was 37.07±15.20 µm, 40.67±12.53 and 40.38±18.67, respectively, which was not significantly different (p=0.85). The mean ellipsoid zone width (EZW) loss (±SD) was 2051 µm (±1318) for patients in the TLOF, and 1314 µm (±965) for MLOF. Only one patient in the TM group had EZW loss at presentation. There was considerable overlap in ERG findings, although the largest DA 10 ERG b-waves were associated with TLOF and the smallest with TM variants. CONCLUSIONS Patients with missense alterations had better BCVA and greater structural integrity. This is important for patient prognostication and counselling, as well as stratification for future gene therapy trials.
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Affiliation(s)
- Thales A C de Guimaraes
- Institute of Ophthalmology, University College London, London, UK
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Michalis Georgiou
- Institute of Ophthalmology, University College London, London, UK
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Anthony G Robson
- Institute of Ophthalmology, University College London, London, UK
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Kaoru Fujinami
- Institute of Ophthalmology, University College London, London, UK
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
- Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, Tokyo, Japan
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Ajoy Vincent
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Fadi Nasser
- Centre for Ophthalmology, University Hospital Tubingen Institute for Ophthalmic Research, Tubingen, Germany
| | - Samer Khateb
- Department of Ophthalmology, Hadassah Medical Center, Jerusalem, Israel
| | - Omar A Mahroo
- Institute of Ophthalmology, University College London, London, UK
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Nikolas Pontikos
- Institute of Ophthalmology, University College London, London, UK
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | | | - Alberta A H J Thiadens
- Department of Opthalmology, Erasmus Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Emanuel R de Carvalho
- Institute of Ophthalmology, University College London, London, UK
- Department of Ophthalmology, Amsterdam University Medical Centres, Amsterdam, The Netherlands
| | - Xuan-Than-An Nguyen
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands
| | - Gavin Arno
- Institute of Ophthalmology, University College London, London, UK
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Yu Fujinami-Yokokawa
- Institute of Ophthalmology, University College London, London, UK
- Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, Tokyo, Japan
- Department of Health Policy and Management, Keio University School of Medicine, Tokyo, Japan
| | - Xiao Liu
- Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, Tokyo, Japan
| | - Kazushige Tsunoda
- Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, Tokyo, Japan
| | - Takaaki Hayashi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | | | - Maria Inmaculada Martin-Merida
- Instituto de Investigacion Sanitaria de la Fundacion Jimenez Diaz, Madrid, Spain
- Center for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Almudena Avila-Fernandez
- Instituto de Investigacion Sanitaria de la Fundacion Jimenez Diaz, Madrid, Spain
- Center for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Ester Carreño Salas
- Instituto de Investigacion Sanitaria de la Fundacion Jimenez Diaz, Madrid, Spain
| | | | - Carmen Ayuso
- Instituto de Investigacion Sanitaria de la Fundacion Jimenez Diaz, Madrid, Spain
- Center for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Dror Sharon
- Department of Ophthalmology, Hadassah Medical Center, Jerusalem, Israel
| | - Susanne Kohl
- Centre for Ophthalmology, University Hospital Tubingen Institute for Ophthalmic Research, Tubingen, Germany
| | - Rachel M Huckfeldt
- Department of Ophthalmology, Massachusetts Eye and Ear, Harvard, Massachusetts, USA
| | - Eyal Banin
- Department of Ophthalmology, Hadassah Medical Center, Jerusalem, Israel
| | - Mark E Pennesi
- Department of Ophthalmology, Oregon Health & Science University - Casey Eye Institute, Portland, Oregon, USA
| | - Arif O Khan
- Eye Institute, Cleveland Clinic Abu Dhabi, Abu Dhabi, UAE
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, USA
| | - Bernd Wissinger
- Centre for Ophthalmology, University Hospital Tubingen Institute for Ophthalmic Research, Tubingen, Germany
| | - Andrew R Webster
- Institute of Ophthalmology, University College London, London, UK
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Elise Heon
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Camiel J F Boon
- Department of Ophthalmology, Amsterdam University Medical Centres, Amsterdam, The Netherlands
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands
| | - Eberhard Zrenner
- Centre for Ophthalmology, University Hospital Tubingen Institute for Ophthalmic Research, Tubingen, Germany
| | - Michel Michaelides
- Institute of Ophthalmology, University College London, London, UK
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
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2
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Sakti DH, Cornish EE, Ali H, Retsas S, Raza M, Saakova N, Carvalho LS, Nash BM, Jamieson RV, Grigg JR. Natural history and biomarkers of KCNV2-associated retinopathy. Clin Exp Ophthalmol 2024; 52:528-544. [PMID: 38443311 DOI: 10.1111/ceo.14373] [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: 09/28/2023] [Revised: 01/31/2024] [Accepted: 02/14/2024] [Indexed: 03/07/2024]
Abstract
BACKGROUND KCNV2-associated retinopathy is an autosomal recessive inherited retinal disease classically named cone dystrophy with supernormal rod response (CDSRR). This study aims to identify the best biomarker for evaluating the condition. METHODS A retrospective review of eight patients from seven families with genetically confirmed KCNV2-associated retinopathy was performed. The best corrected visual acuity (BCVA), full-field electroretinogram (ffERG), pattern ERG (pERG), fundus imaging: retinal photograph and fundus autofluorescence (FAF), and optical coherence tomography (OCT) were analysed. RESULTS There was a disproportionate increase in b-wave amplitude with a relatively small light intensity increase, especially between the two dimmest stimuli of DA 0.002 and 0.01 (-2.7 and -2.0 log cd.s/m2). The a-wave amplitude was normal. The a-wave peak time was delayed in all stimuli. The b-wave peak time was delayed compared to normal, but the gap tightened as intensity increased. The b:a wave ratio was above or at the upper limit for the reference values. FAF bull's eye maculopathy pattern was prominent and variable foveal disruption on OCT was apparent in all patients. Legal blindness was reached before the age of 25. CONCLUSIONS We identified three potential electrophysiology biomarkers to assist in evaluating future therapies: the disproportionate b-wave amplitude jump, delayed a-wave and b-wave peak time, and the higher than normal b:a wave ratio. Any of these biomarkers found with photoreceptor ellipsoid zone foveal-perifoveal disruption should prompt consideration for KCNV2 retinopathy. The BCVA natural history data suggests the probable optimum therapeutic window in the first three decades of life.
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Affiliation(s)
- Dhimas H Sakti
- Save Sight Institute, University of Sydney, New South Wales, Australia
- Department of Ophthalmology, Faculty of Medicine, Public Health, and Nursing, Universitas Gadjah Mada, Yogyakarta, Indonesia
| | - Elisa E Cornish
- Save Sight Institute, University of Sydney, New South Wales, Australia
- Eye Genetics Research Unit, Children's Medical Research Institute, The Children's Hospital at Westmead, Westmead, New South Wales, Australia
| | - Haipha Ali
- Save Sight Institute, University of Sydney, New South Wales, Australia
| | - Stephanie Retsas
- Save Sight Institute, University of Sydney, New South Wales, Australia
| | - Marium Raza
- Save Sight Institute, University of Sydney, New South Wales, Australia
| | - Nonna Saakova
- Save Sight Institute, University of Sydney, New South Wales, Australia
| | - Livia S Carvalho
- Centre for Ophthalmology and Visual Sciences, Lions Eye Institute, The University of Western Australia, Nedlands, Australia
- Department of Optometry and Vision Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne, Australia
| | - Benjamin M Nash
- Eye Genetics Research Unit, Children's Medical Research Institute, The Children's Hospital at Westmead, Westmead, New South Wales, Australia
| | - Robyn V Jamieson
- Save Sight Institute, University of Sydney, New South Wales, Australia
- Eye Genetics Research Unit, Children's Medical Research Institute, The Children's Hospital at Westmead, Westmead, New South Wales, Australia
| | - John R Grigg
- Save Sight Institute, University of Sydney, New South Wales, Australia
- Eye Genetics Research Unit, Children's Medical Research Institute, The Children's Hospital at Westmead, Westmead, New South Wales, Australia
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Zobor D, Brühwiler B, Zrenner E, Weisschuh N, Kohl S. Genetic and Clinical Profile of Retinopathies Due to Disease-Causing Variants in Leber Congenital Amaurosis (LCA)-Associated Genes in a Large German Cohort. Int J Mol Sci 2023; 24:ijms24108915. [PMID: 37240262 DOI: 10.3390/ijms24108915] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Revised: 05/06/2023] [Accepted: 05/08/2023] [Indexed: 05/28/2023] Open
Abstract
To report the spectrum of Leber congenital amaurosis (LCA) associated genes in a large German cohort and to delineate their associated phenotype. Local databases were screened for patients with a clinical diagnosis of LCA and for patients with disease-causing variants in known LCA-associated genes independent of their clinical diagnosis. Patients with a mere clinical diagnosis were invited for genetic testing. Genomic DNA was either analyzed in a diagnostic-genetic or research setup using various capture panels for syndromic and non-syndromic IRD (inherited retinal dystrophy) genes. Clinical data was obtained mainly retrospectively. Patients with genetic and phenotypic information were eventually included. Descriptive statistical data analysis was performed. A total of 105 patients (53 female, 52 male, age 3-76 years at the time of data collection) with disease-causing variants in 16 LCA-associated genes were included. The genetic spectrum displayed variants in the following genes: CEP290 (21%), CRB1 (21%), RPE65 (14%), RDH12 (13%), AIPL1 (6%), TULP1 (6%), and IQCB1 (5%), and few cases harbored pathogenic variants in LRAT, CABP4, NMNAT1, RPGRIP1, SPATA7, CRX, IFT140, LCA5, and RD3 (altogether accounting for 14%). The most common clinical diagnosis was LCA (53%, 56/105) followed by retinitis pigmentosa (RP, 40%, 42/105), but also other IRDs were seen (cone-rod dystrophy, 5%; congenital stationary night blindness, 2%). Among LCA patients, 50% were caused by variants in CEP290 (29%) and RPE65 (21%), whereas variants in other genes were much less frequent (CRB1 11%, AIPL1 11%, IQCB1 9%, and RDH12 7%, and sporadically LRAT, NMNAT1, CRX, RD3, and RPGRIP1). In general, the patients showed a severe phenotype hallmarked by severely reduced visual acuity, concentric narrowing of the visual field, and extinguished electroretinograms. However, there were also exceptional cases with best corrected visual acuity as high as 0.8 (Snellen), well-preserved visual fields, and preserved photoreceptors in spectral domain optical coherence tomography. Phenotypic variability was seen between and within genetic subgroups. The study we are presenting pertains to a considerable LCA group, furnishing valuable comprehension of the genetic and phenotypic spectrum. This knowledge holds significance for impending gene therapeutic trials. In this German cohort, CEP290 and CRB1 are the most frequently mutated genes. However, LCA is genetically highly heterogeneous and exhibits clinical variability, showing overlap with other IRDs. For any therapeutic gene intervention, the disease-causing genotype is the primary criterion for treatment access, but the clinical diagnosis, state of the retina, number of to be treated target cells, and the time point of treatment will be crucial.
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Affiliation(s)
- Ditta Zobor
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn Strasse 7, 72076 Tübingen, Germany
- Department of Ophthalmology, Semmelweis University, 1085 Budapest, Hungary
| | - Britta Brühwiler
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn Strasse 7, 72076 Tübingen, Germany
| | - Eberhart Zrenner
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn Strasse 7, 72076 Tübingen, Germany
- Werner Reichardt Center for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany
| | - Nicole Weisschuh
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn Strasse 7, 72076 Tübingen, Germany
| | - Susanne Kohl
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn Strasse 7, 72076 Tübingen, Germany
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4
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Georgiou M, Fujinami K, Vincent A, Nasser F, Khateb S, Vargas ME, Thiadens AA, de Carvalho ER, Nguyen XTA, De Guimarães TAC, Robson AG, Mahroo OA, Pontikos N, Arno G, Fujinami-Yokokawa Y, Leo SM, Liu X, Tsunoda K, Hayashi T, Jimenez-Rolando B, Martin-Merida MI, Avila-Fernandez A, Carreño E, Garcia-Sandoval B, Ayuso C, Sharon D, Kohl S, Huckfeldt RM, Boon CJ, Banin E, Pennesi ME, Wissinger B, Webster AR, Héon E, Khan AO, Zrenner E, Michaelides M. KCNV2-Associated Retinopathy: Detailed Retinal Phenotype and Structural Endpoints-KCNV2 Study Group Report 2. Am J Ophthalmol 2021; 230:1-11. [PMID: 33737031 PMCID: PMC8710866 DOI: 10.1016/j.ajo.2021.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 03/02/2021] [Accepted: 03/03/2021] [Indexed: 12/01/2022]
Abstract
PURPOSE To describe the detailed retinal phenotype of KCNV2-associated retinopathy. STUDY DESIGN Multicenter international retrospective case series. METHODS Review of retinal imaging including fundus autofluorescence (FAF) and optical coherence tomography (OCT), including qualitative and quantitative analyses. RESULTS Three distinct macular FAF features were identified: (1) centrally increased signal (n = 35, 41.7%), (2) decreased autofluorescence (n = 27, 31.1%), and (3) ring of increased signal (n = 37, 44.0%). Five distinct FAF groups were identified based on combinations of those features, with 23.5% of patients changing the FAF group over a mean (range) follow-up of 5.9 years (1.9-13.1 years). Qualitative assessment was performed by grading OCT into 5 grades: (1) continuous ellipsoid zone (EZ) (20.5%); (2) EZ disruption (26.1%); (3) EZ absence, without optical gap and with preserved retinal pigment epithelium complex (21.6%); (4) loss of EZ and a hyporeflective zone at the foveola (6.8%); and (5) outer retina and retinal pigment epithelium complex loss (25.0%). Eighty-six patients had scans available from both eyes, with 83 (96.5%) having the same grade in both eyes, and 36.1% changed OCT grade over a mean follow-up of 5.5 years. The annual rate of outer nuclear layer thickness change was similar for right and left eyes. CONCLUSIONS KCNV2-associated retinopathy is a slowly progressive disease with early retinal changes, which are predominantly symmetric between eyes. The identification of a single OCT or FAF measurement as an endpoint to determine progression that applies to all patients may be challenging, although outer nuclear layer thickness is a potential biomarker. Findings suggest a potential window for intervention until 40 years of age.
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5
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Rashwan R, Hunt DM, Carvalho LS. The role of voltage-gated ion channels in visual function and disease in mammalian photoreceptors. Pflugers Arch 2021; 473:1455-1468. [PMID: 34255151 DOI: 10.1007/s00424-021-02595-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 05/31/2021] [Accepted: 06/10/2021] [Indexed: 12/26/2022]
Abstract
Light activation of the classical light-sensing retinal neurons, the photoreceptors, results in a graded change in membrane potential that ultimately leads to a reduction in neurotransmitter release to the post-synaptic retinal neurons. Photoreceptors show striking powers of adaptation, and for visual processing to function optimally, they must adjust their gain to remain responsive to different levels of ambient light intensity. The presence of a tightly controlled balance of inward and outward currents modulated by several different types of ion channels is what gives photoreceptors their remarkably dynamic operating range. Part of the resetting and modulation of this operating range is controlled by potassium and calcium voltage-gated channels, which are involved in setting the dark resting potential and synapse signal processing, respectively. Their essential contribution to visual processing is further confirmed in patients suffering from cone dystrophy with supernormal rod response (CDSRR) and congenital stationary night blindness type 2 (CSNB2), both conditions that lead to irreversible vision loss. This review will discuss these two types of voltage-gated ion channels present in photoreceptors, focussing on their structure and physiology, and their role in visual processing. It will also discuss the use and benefits of knockout mouse models to further study the function of these channels and what routes to potential treatments could be applied for CDSRR and CSNB2.
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Affiliation(s)
- Rabab Rashwan
- Lions Eye Institute, Nedlands, Western Australia, 6009, Australia
- Department of Microbiology and Immunology, Faculty of Medicine, Minia University, Minia, Egypt
| | - David M Hunt
- Lions Eye Institute, Nedlands, Western Australia, 6009, Australia
- Centre for Ophthalmology and Vision Science, The University of Western Australia, Perth, Western Australia, 6009, Australia
- School of Biological Sciences, University of Western Australia, Nedlands, Western Australia, 6009, Australia
| | - Livia S Carvalho
- Lions Eye Institute, Nedlands, Western Australia, 6009, Australia.
- Centre for Ophthalmology and Vision Science, The University of Western Australia, Perth, Western Australia, 6009, Australia.
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6
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Jiang X, Rashwan R, Voigt V, Nerbonne J, Hunt DM, Carvalho LS. Molecular, Cellular and Functional Changes in the Retinas of Young Adult Mice Lacking the Voltage-Gated K + Channel Subunits Kv8.2 and K2.1. Int J Mol Sci 2021; 22:4877. [PMID: 34063002 PMCID: PMC8124447 DOI: 10.3390/ijms22094877] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 04/24/2021] [Accepted: 04/29/2021] [Indexed: 02/06/2023] Open
Abstract
Cone Dystrophy with Supernormal Rod Response (CDSRR) is a rare autosomal recessive disorder leading to severe visual impairment in humans, but little is known about its unique pathophysiology. We have previously shown that CDSRR is caused by mutations in the KCNV2 (Potassium Voltage-Gated Channel Modifier Subfamily V Member 2) gene encoding the Kv8.2 subunit, a modulatory subunit of voltage-gated potassium (Kv) channels. In a recent study, we validated a novel mouse model of Kv8.2 deficiency at a late stage of the disease and showed that it replicates the human electroretinogram (ERG) phenotype. In this current study, we focused our investigation on young adult retinas to look for early markers of disease and evaluate their effect on retinal morphology, electrophysiology and immune response in both the Kv8.2 knockout (KO) mouse and in the Kv2.1 KO mouse, the obligate partner of Kv8.2 in functional retinal Kv channels. By evaluating the severity of retinal dystrophy in these KO models, we demonstrated that retinas of Kv KO mice have significantly higher apoptotic cells, a thinner outer nuclear cell layer and increased activated microglia cells in the subretinal space. Our results indicate that in the murine retina, the loss of Kv8.2 subunits contributes to early cellular and physiological changes leading to retinal dysfunction. These results could have potential implications in the early management of CDSRR despite its relatively nonprogressive nature in humans.
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Affiliation(s)
- Xiaotian Jiang
- Centre for Ophthalmology and Vision Science, The University of Western Australia, Perth, WA 6009, Australia; (X.J.); (D.M.H.)
| | - Rabab Rashwan
- Lions Eye Institute, Nedlands, WA 6009, Australia; (R.R.); (V.V.)
- Department of Microbiology and Immunology, Faculty of Medicine, Minia University, Minia 61519, Egypt
| | - Valentina Voigt
- Lions Eye Institute, Nedlands, WA 6009, Australia; (R.R.); (V.V.)
| | - Jeanne Nerbonne
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA;
| | - David M. Hunt
- Centre for Ophthalmology and Vision Science, The University of Western Australia, Perth, WA 6009, Australia; (X.J.); (D.M.H.)
- Lions Eye Institute, Nedlands, WA 6009, Australia; (R.R.); (V.V.)
| | - Livia S. Carvalho
- Centre for Ophthalmology and Vision Science, The University of Western Australia, Perth, WA 6009, Australia; (X.J.); (D.M.H.)
- Lions Eye Institute, Nedlands, WA 6009, Australia; (R.R.); (V.V.)
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7
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Georgiou M, Robson AG, Fujinami K, Leo SM, Vincent A, Nasser F, Cabral De Guimarães TA, Khateb S, Pontikos N, Fujinami-Yokokawa Y, Liu X, Tsunoda K, Hayashi T, Vargas ME, Thiadens AAHJ, de Carvalho ER, Nguyen XTA, Arno G, Mahroo OA, Martin-Merida MI, Jimenez-Rolando B, Gordo G, Carreño E, Ayuso C, Sharon D, Kohl S, Huckfeldt RM, Wissinger B, Boon CJF, Banin E, Pennesi ME, Khan AO, Webster AR, Zrenner E, Héon E, Michaelides M. KCNV2-Associated Retinopathy: Genetics, Electrophysiology, and Clinical Course-KCNV2 Study Group Report 1. Am J Ophthalmol 2021; 225:95-107. [PMID: 33309813 PMCID: PMC8186730 DOI: 10.1016/j.ajo.2020.11.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 11/18/2020] [Accepted: 11/25/2020] [Indexed: 12/01/2022]
Abstract
PURPOSE To investigate genetics, electrophysiology, and clinical course of KCNV2-associated retinopathy in a cohort of children and adults. STUDY DESIGN This was a multicenter international clinical cohort study. METHODS Review of clinical notes and molecular genetic testing. Full-field electroretinography (ERG) recordings, incorporating the international standards, were reviewed and quantified and compared with age and recordings from control subjects. RESULTS In total, 230 disease-associated alleles were identified from 117 patients, corresponding to 75 different KCNV2 variants, with 28 being novel. The mean age of onset was 3.9 years old. All patients were symptomatic before 12 years of age (range, 0-11 years). Decreased visual acuity was present in all patients, and 4 other symptoms were common: reduced color vision (78.6%), photophobia (53.5%), nyctalopia (43.6%), and nystagmus (38.6%). After a mean follow-up of 8.4 years, the mean best-corrected visual acuity (BCVA ± SD) decreased from 0.81 ± 0.27 to 0.90 ± 0.31 logarithm of minimal angle of resolution. Full-field ERGs showed pathognomonic waveform features. Quantitative assessment revealed a wide range of ERG amplitudes and peak times, with a mean rate of age-associated reduction indistinguishable from the control group. Mean amplitude reductions for the dark-adapted 0.01 ERG, dark-adapted 10 ERG a-wave, and LA 3.0 30 Hz and LA3 ERG b-waves were 55%, 21%, 48%, and 74%, respectively compared with control values. Peak times showed stability across 6 decades. CONCLUSION In KCNV2-associated retinopathy, full-field ERGs are diagnostic and consistent with largely stable peripheral retinal dysfunction. Report 1 highlights the severity of the clinical phenotype and established a large cohort of patients, emphasizing the unmet need for trials of novel therapeutics.
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Affiliation(s)
- Michalis Georgiou
- Moorfields Eye Hospital, London, United Kingdom; University College London Institute of Ophthalmology, London, United Kingdom
| | - Anthony G Robson
- Moorfields Eye Hospital, London, United Kingdom; University College London Institute of Ophthalmology, London, United Kingdom
| | - Kaoru Fujinami
- Moorfields Eye Hospital, London, United Kingdom; University College London Institute of Ophthalmology, London, United Kingdom; Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan; Department of Ophthalmology, Keio University School of Medicine, Tokyo, Ontario, Japan
| | - Shaun M Leo
- Moorfields Eye Hospital, London, United Kingdom; University College London Institute of Ophthalmology, London, United Kingdom
| | - Ajoy Vincent
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Fadi Nasser
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | | | - Samer Khateb
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Nikolas Pontikos
- Moorfields Eye Hospital, London, United Kingdom; University College London Institute of Ophthalmology, London, United Kingdom
| | - Yu Fujinami-Yokokawa
- University College London Institute of Ophthalmology, London, United Kingdom; Department of Health Policy and Management, Keio University School of Medicine, Tokyo, Japan
| | - Xiao Liu
- Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan; Department of Ophthalmology, Keio University School of Medicine, Tokyo, Ontario, Japan
| | - Kazushige Tsunoda
- Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan; Department of Ophthalmology, Keio University School of Medicine, Tokyo, Ontario, Japan
| | - Takaaki Hayashi
- Department of Ophthalmology, Katsushika Medical Center, The Jikei University School of Medicine, Tokyo, Japan
| | - Mauricio E Vargas
- Department of Ophthalmology, Oregon Health and Science University, Casey Eye Institute, Portland, Oregon, USA
| | | | - Emanuel R de Carvalho
- University College London Institute of Ophthalmology, London, United Kingdom; Department of Ophthalmology, Amsterdam UMC, Academic Medical Center, Amsterdam, the Netherlands
| | - Xuan-Thanh-An Nguyen
- Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands
| | - Gavin Arno
- Moorfields Eye Hospital, London, United Kingdom; University College London Institute of Ophthalmology, London, United Kingdom
| | - Omar A Mahroo
- Moorfields Eye Hospital, London, United Kingdom; University College London Institute of Ophthalmology, London, United Kingdom
| | - Maria Inmaculada Martin-Merida
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Belen Jimenez-Rolando
- Department of Ophthalmology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid, Madrid, Spain
| | - Gema Gordo
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Ester Carreño
- Department of Ophthalmology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid, Madrid, Spain
| | - Carmen Ayuso
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Dror Sharon
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Susanne Kohl
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Rachel M Huckfeldt
- Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
| | - Bernd Wissinger
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Camiel J F Boon
- Department of Ophthalmology, Amsterdam UMC, Academic Medical Center, Amsterdam, the Netherlands; Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands
| | - Eyal Banin
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Mark E Pennesi
- Department of Ophthalmology, Oregon Health and Science University, Casey Eye Institute, Portland, Oregon, USA
| | - Arif O Khan
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western University, Cleveland, Ohio, USA; Eye Institute, Cleveland Clinic Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Andrew R Webster
- Moorfields Eye Hospital, London, United Kingdom; University College London Institute of Ophthalmology, London, United Kingdom
| | - Eberhart Zrenner
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Elise Héon
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Michel Michaelides
- Moorfields Eye Hospital, London, United Kingdom; University College London Institute of Ophthalmology, London, United Kingdom.
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Transient electroretinographic abnormalities that mimic those of KCNV2 retinopathy: a case report. Doc Ophthalmol 2021; 143:221-228. [PMID: 33738644 PMCID: PMC8494656 DOI: 10.1007/s10633-021-09828-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 02/24/2021] [Indexed: 11/30/2022]
Abstract
Purpose The purpose of this report was to describe the case of a 68-year-old male patient with stage IV colon cancer who exhibited electroretinographic abnormalities that are similar to those of KCNV2 retinopathy. Methods The patient presenting with photophobia, reduced visual acuity, and poor general conditions, the onset of which occurred ten days before presentation, was examined using fundoscopy, full-field electroretinography, blood tests, and abdominal computed tomography. Results The patient’s decimal best-corrected visual acuity (BCVA) was 0.4 in each eye. Fundoscopy showed bull's eye-like maculopathy in both eyes. Electroretinographic findings were similar to the characteristic findings of KCNV2 retinopathy: Rod electroretinogram showed delayed and preserved b-wave amplitudes; bright-flash electroretinogram showed double troughs of a-waves; b/a ratios shown by bright-flash electroretinogram were higher than those shown by standard-flash electroretinogram; and both cone and 30-Hz flicker electroretinograms showed extinguished responses. His serum potassium level increased to 6.2 mmol/L (normal range 3.6–4.8 mmol/L) owing to hydronephrosis resulting from disseminated carcinoma. After performing an emergency surgery to treat this condition, the serum potassium level immediately decreased to a normal range. Eleven days after presentation, rod and standard/bright-flash electroretinography showed improvement in the implicit time of the rod b-waves and the a-waves. Unexpectedly, the responses recorded by cone and 30-Hz flicker electroretinography became normal. The symptoms and maculopathy disappeared, and his BCVA improved to 1.2. Conclusions The abnormal electroretinographic findings might be associated with the transient increase in serum potassium level.
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Esteves-Leandro J, Torres-Costa S, Estrela-Silva S, Santos-Silva R, Brandão E, Grangeia A, Fernandes S, Oliveira R, Falcão-Reis F, Rocha-Sousa A. Cone dystrophy with supernormal rod responses: A rare KCNV2 gene variant. Eur J Ophthalmol 2021; 32:664-672. [PMID: 33706576 DOI: 10.1177/11206721211000000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PURPOSE To describe the clinical, electrophysiological, and genetic findings of three Portuguese families with a rare variant in the KCNV2 gene resulting in "cone dystrophy with supernormal rod responses" (CDSRR). METHODS Retrospective clinical revision of five individuals from three unrelated families with CDSRR. Ophthalmological examination was described in all patients and included color vision testing, fundus photography, fundus autofluorescence (FAF) imaging, spectral domain-optical coherence tomography (SD-OCT), pattern electroretinogram (ERG), and full-field ERG. The mutational screening of the KCNV2 gene was performed with Sanger and Next Generation Sequencing. RESULTS All patients showed childhood-onset photophobia and progressive visual acuity loss with varying degrees of severity. In multimodal imaging, various degrees of retinal pigment epithelium disturbances and outer retinal atrophy, which tend to be worst with advancing age, were observed. Molecular screening identified a rare presumed truncating variant (p.Glu209Ter) in homozygosity in two families and in compound heterozygosity in a third family. Three patients showed ERG changes characteristic of CDSRR, however, two patients presented with incomplete electrophysiological features of the disease. CONCLUSION A rare variant in the KCNV2 gene was identified in five patients from three Portuguese families. This variant often leads to a severe and progressive form of retinopathy. Considerable variability in the ERG responses among patients with this KCNV2 variant was observed.
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Affiliation(s)
- João Esteves-Leandro
- Department of Ophthalmology, Centro Hospitalar Universitário de São João, Porto, Portugal
| | - Sónia Torres-Costa
- Department of Ophthalmology, Centro Hospitalar Universitário de São João, Porto, Portugal
| | - Sérgio Estrela-Silva
- Department of Ophthalmology, Centro Hospitalar Universitário de São João, Porto, Portugal.,Department of Surgery and Physiology, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Renato Santos-Silva
- Department of Ophthalmology, Centro Hospitalar Universitário de São João, Porto, Portugal.,Department of Surgery and Physiology, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Elisete Brandão
- Department of Ophthalmology, Centro Hospitalar Universitário de São João, Porto, Portugal
| | - Ana Grangeia
- Department of Genetics, Centro Hospitalar Universitário de São João, Porto, Portugal
| | - Susana Fernandes
- Department of Genetics, Centro Hospitalar Universitário de São João, Porto, Portugal.,Institute for Innovation and Health Research (I3S), University of Porto, Porto, Portugal
| | - Renata Oliveira
- Department of Genetics, Centro Hospitalar Universitário de São João, Porto, Portugal
| | - Fernando Falcão-Reis
- Department of Ophthalmology, Centro Hospitalar Universitário de São João, Porto, Portugal.,Department of Surgery and Physiology, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Amândio Rocha-Sousa
- Department of Ophthalmology, Centro Hospitalar Universitário de São João, Porto, Portugal.,Department of Surgery and Physiology, Faculty of Medicine, University of Porto, Porto, Portugal
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Stockman A, Henning GB, Rider AT. Clinical vision and molecular loss: Integrating visual psychophysics with molecular genetics reveals key details of normal and abnormal visual processing. Prog Retin Eye Res 2020; 83:100937. [PMID: 33388434 DOI: 10.1016/j.preteyeres.2020.100937] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 12/11/2020] [Accepted: 12/17/2020] [Indexed: 01/08/2023]
Abstract
Over the past two decades we have developed techniques and models to investigate the ways in which known molecular defects affect visual performance. Because molecular defects in retinal signalling invariably alter the speed of visual processing, our strategy has been to measure the resulting changes in flicker sensitivity. Flicker measurements provide not only straightforward clinical assessments of visual performance but also reveal fundamental details about the functioning of both abnormal and normal visual systems. Here, we bring together our past measurements of patients with pathogenic variants in the GNAT2, RGS9, GUCA1A, RPE65, OPA1, KCNV2 and NR2E3 genes and analyse the results using a standard model of visual processing. The model treats flicker sensitivity as the result of the actions of a sequence of simple processing steps, one or more of which is altered by the genetic defect. Our analyses show that most defects slow down the visual response directly, but some speed it up. Crucially, however, other steps in the processing sequence can make compensatory adjustments to offset the abnormality. For example, if the abnormal step slows down the visual response, another step is likely to speed up or attenuate the response to rebalance system performance. Such compensatory adjustments are probably made by steps in the sequence that usually adapt to changing light levels. Our techniques and modelling also allow us to tease apart stationary and progressive effects, and the localised molecular losses help us to unravel and characterise individual steps in the normal and abnormal processing sequences.
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Affiliation(s)
- Andrew Stockman
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, England, UK.
| | - G Bruce Henning
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, England, UK
| | - Andrew T Rider
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, England, UK
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11
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Lie H, Wang G, Liu X, Meng X, Long Y, Ren J, Yang L, Fujinami-Yokokawa Y, Kurihara T, Tsubota K, Fujinami K, Li S. Long-term follow-up of a Chinese patient with KCNV2-retinopathy. Ophthalmic Genet 2020; 42:144-149. [PMID: 33372566 DOI: 10.1080/13816810.2020.1861307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Purpose: To characterize and monitor the clinical and electrophysiological features of a Chinese patient with KCNV2 retinopathy.Methods: A 17-year-old Chinese male with the diagnosis of cone dystrophy with supernormal rod response (CDSRR) was followed-up for 5 years, with full ophthalmological examinations, including decimal best corrected visual acuity (BCVA), fundus photography, fundus autofluorescence (FAF) imaging, spectral-domain optical coherence tomography (SD-OCT), and full-field electroretinogram (ERG). Genetic screening was performed to detect the sequence variations in the retinal dystrophy associated genes in the patient and his parents.Results: The patient demonstrated the characteristic full-field electroretinography (ERG) features of CDSRR, namely a profound enlargement of the dark-adapted ERG b-wave amplitude with increasing flash strength and a broadened a-wave trough; this case also had undetectable light-adapted ERGs. A BCVA of 0.15 was maintained over 5 years in both eyes; while progressive macular atrophy was identified. Molecular genetic analyses revealed two novel disease-causing KCNV2 variants in compound heterozygous state: c.1408 G > C (p.Gly470Arg) and c.1500 C > G (p.Tyr500Ter).Conclusions: This is the first long-term case study of an East Asian patient with molecularly confirmed CDSRR. The progressive atrophy with maintained VA demonstrated in this case will be valuable for increasing the understanding of the natural course of KCNV2 retinopathy and it will help in counselling patients with this disease.
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Affiliation(s)
- Hongxuan Lie
- Ophthalmology Department, Southwest Hospital, Army Medical University (Third Military Medical University), Chongqing, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Gang Wang
- Ophthalmology Department, Southwest Hospital, Army Medical University (Third Military Medical University), Chongqing, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Xiao Liu
- Ophthalmology Department, Southwest Hospital, Army Medical University (Third Military Medical University), Chongqing, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China.,Laboratory of Visual Physiology, Division for Vision Research, National Institute of Sensory Organs, National Hospital Organization, Tokyo Medical Center, Tokyo, Japan.,Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Xiaohong Meng
- Ophthalmology Department, Southwest Hospital, Army Medical University (Third Military Medical University), Chongqing, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Yanling Long
- Ophthalmology Department, Southwest Hospital, Army Medical University (Third Military Medical University), Chongqing, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Jiayun Ren
- Ophthalmology Department, Southwest Hospital, Army Medical University (Third Military Medical University), Chongqing, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Lizhu Yang
- Laboratory of Visual Physiology, Division for Vision Research, National Institute of Sensory Organs, National Hospital Organization, Tokyo Medical Center, Tokyo, Japan.,Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Yu Fujinami-Yokokawa
- Laboratory of Visual Physiology, Division for Vision Research, National Institute of Sensory Organs, National Hospital Organization, Tokyo Medical Center, Tokyo, Japan.,Graduate School of Health Management, Keio University, Tokyo, Japan.,Department of Genetics, UCL Institute of Ophthalmology, London, UK.,Division of Inherited Eye Diseases, Moorfields Eye Hospital, London, UK
| | - Toshihide Kurihara
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Kazuo Tsubota
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Kaoru Fujinami
- Laboratory of Visual Physiology, Division for Vision Research, National Institute of Sensory Organs, National Hospital Organization, Tokyo Medical Center, Tokyo, Japan.,Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.,Department of Genetics, UCL Institute of Ophthalmology, London, UK.,Division of Inherited Eye Diseases, Moorfields Eye Hospital, London, UK
| | - Shiying Li
- Ophthalmology Department, Southwest Hospital, Army Medical University (Third Military Medical University), Chongqing, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
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12
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Sensing through Non-Sensing Ocular Ion Channels. Int J Mol Sci 2020; 21:ijms21186925. [PMID: 32967234 PMCID: PMC7554890 DOI: 10.3390/ijms21186925] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 09/17/2020] [Accepted: 09/18/2020] [Indexed: 12/12/2022] Open
Abstract
Ion channels are membrane-spanning integral proteins expressed in multiple organs, including the eye. In the eye, ion channels are involved in various physiological processes, like signal transmission and visual processing. A wide range of mutations have been reported in the corresponding genes and their interacting subunit coding genes, which contribute significantly to an array of blindness, termed ocular channelopathies. These mutations result in either a loss- or gain-of channel functions affecting the structure, assembly, trafficking, and localization of channel proteins. A dominant-negative effect is caused in a few channels formed by the assembly of several subunits that exist as homo- or heteromeric proteins. Here, we review the role of different mutations in switching a “sensing” ion channel to “non-sensing,” leading to ocular channelopathies like Leber’s congenital amaurosis 16 (LCA16), cone dystrophy, congenital stationary night blindness (CSNB), achromatopsia, bestrophinopathies, retinitis pigmentosa, etc. We also discuss the various in vitro and in vivo disease models available to investigate the impact of mutations on channel properties, to dissect the disease mechanism, and understand the pathophysiology. Innovating the potential pharmacological and therapeutic approaches and their efficient delivery to the eye for reversing a “non-sensing” channel to “sensing” would be life-changing.
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13
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Guimaraes TACD, Georgiou M, Robson AG, Michaelides M. KCNV2 retinopathy: clinical features, molecular genetics and directions for future therapy. Ophthalmic Genet 2020; 41:208-215. [PMID: 32441199 PMCID: PMC7446039 DOI: 10.1080/13816810.2020.1766087] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
-associated retinopathy or “cone dystrophy with supernormal rod responses” is an
autosomal recessive cone-rod dystrophy with pathognomonic ERG findings. This gene
encodes Kv8.2, a voltage-gated potassium channel subunit that acts as a modulator by
shifting the activation range of the K+ channels in photoreceptor inner
segments. Currently, no treatment is available for the condition. However, there is a
lack of prospective long-term data in large molecularly confirmed cohorts, which is a
prerequisite for accurate patient counselling/prognostication, to identify an optimal
window for intervention and outcome measures, and ultimately to design future therapy
trials. Herein we provide a detailed review of the clinical features, retinal imaging,
electrophysiology and psychophysical studies, molecular genetics, and briefly discuss
future prospects for therapy trials.
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Affiliation(s)
- Thales A C De Guimaraes
- UCL Institute of Ophthalmology, University College London , London, UK.,Moorfields Eye Hospital , London, UK
| | - Michalis Georgiou
- UCL Institute of Ophthalmology, University College London , London, UK.,Moorfields Eye Hospital , London, UK
| | - Anthony G Robson
- UCL Institute of Ophthalmology, University College London , London, UK.,Moorfields Eye Hospital , London, UK
| | - Michel Michaelides
- UCL Institute of Ophthalmology, University College London , London, UK.,Moorfields Eye Hospital , London, UK
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14
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Van Hook MJ, Nawy S, Thoreson WB. Voltage- and calcium-gated ion channels of neurons in the vertebrate retina. Prog Retin Eye Res 2019; 72:100760. [PMID: 31078724 PMCID: PMC6739185 DOI: 10.1016/j.preteyeres.2019.05.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/25/2019] [Accepted: 05/01/2019] [Indexed: 02/06/2023]
Abstract
In this review, we summarize studies investigating the types and distribution of voltage- and calcium-gated ion channels in the different classes of retinal neurons: rods, cones, horizontal cells, bipolar cells, amacrine cells, interplexiform cells, and ganglion cells. We discuss differences among cell subtypes within these major cell classes, as well as differences among species, and consider how different ion channels shape the responses of different neurons. For example, even though second-order bipolar and horizontal cells do not typically generate fast sodium-dependent action potentials, many of these cells nevertheless possess fast sodium currents that can enhance their kinetic response capabilities. Ca2+ channel activity can also shape response kinetics as well as regulating synaptic release. The L-type Ca2+ channel subtype, CaV1.4, expressed in photoreceptor cells exhibits specific properties matching the particular needs of these cells such as limited inactivation which allows sustained channel activity and maintained synaptic release in darkness. The particular properties of K+ and Cl- channels in different retinal neurons shape resting membrane potentials, response kinetics and spiking behavior. A remaining challenge is to characterize the specific distributions of ion channels in the more than 100 individual cell types that have been identified in the retina and to describe how these particular ion channels sculpt neuronal responses to assist in the processing of visual information by the retina.
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Affiliation(s)
- Matthew J Van Hook
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - Scott Nawy
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE, USA; Department Pharmacology & Experimental Neuroscience(2), University of Nebraska Medical Center, Omaha, NE, USA
| | - Wallace B Thoreson
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE, USA; Department Pharmacology & Experimental Neuroscience(2), University of Nebraska Medical Center, Omaha, NE, USA.
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15
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Johnson MA, Jeffrey BG, Messias AMV, Robson AG. ISCEV extended protocol for the stimulus-response series for the dark-adapted full-field ERG b-wave. Doc Ophthalmol 2019; 138:217-227. [PMID: 30929109 DOI: 10.1007/s10633-019-09687-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 03/13/2019] [Indexed: 11/28/2022]
Abstract
The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum protocol for clinical testing but encourages more extensive testing where appropriate. This ISCEV extended protocol describes an extension of the ISCEV full-field ERG standard, in which methods to record and evaluate the growth of the dark-adapted (DA) ERG b-wave with increasing stimulus energy are described. The flashes span a range that includes the weakest flash required to generate a reliable DA ERG b-wave and that required to generate a maximal b-wave amplitude. The DA ERG b-wave stimulus-response series (also known historically as the "intensity-response" or "luminance-response" series) can more comprehensively characterize generalized rod system function than the ISCEV standard ERG protocol and may be of diagnostic or prognostic value in disorders that cause generalized rod system dysfunction.
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Affiliation(s)
- Mary A Johnson
- Department of Ophthalmology and Visual Sciences, University of Maryland School of Medicine, 10 S. Pine St., MSTF Suite 500-A, Baltimore, MD, 21201, USA.
| | - Brett G Jeffrey
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, Bethesda, MD, USA
| | - André M V Messias
- Oftalmologia e Otorrinolaringologia e Cirurgia de Cabeça e Pescoço, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Anthony G Robson
- Department of Electrophysiology, Moorfields Eye Hospital, London, UK.,Institute of Ophthalmology, University College London, London, UK
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Abstract
PURPOSE To investigate receptor and post-receptor function in KCNV2 retinopathy [cone dystrophy with supernormal rod electroretinogram (ERG)], using the pupillary light reflex (PLR) and the ERG. METHODS Two unrelated patients (1 male and 1 female) with molecularly confirmed KCNV2 retinopathy underwent full-field two-color pupillometry testing in one eye, with monitoring of the stimulated eye by an infrared digital camera. Pupillometry stimuli consisted of 1-s duration, short-wavelength (465-nm, blue) and long-wavelength (642-nm, red) stimuli. Pupillometry intensity series were performed under both a dark-adapted condition and a light-adapted condition (on a 0.76-log cd m-2 blue background). The transient PLR, defined as the maximum constriction following flash onset, was measured under all conditions. The melanopsin-mediated sustained constriction was measured 5-7 s following flash offset for the highest flash luminance presented in the dark. Both patients were also tested in one eye with the full-field ERG, including a dark-adapted intensity series and ISCEV standard stimuli. RESULTS Dark-adapted PLRs were markedly attenuated or extinguished for low-luminance stimuli, but the responses to higher-luminance blue stimuli were within normal limits. Light-adapted PLRs to blue stimuli were generally within normal limits, exceeding the responses to photopically matched red stimuli. Thus, light-adapted responses were consistent with either rod or S-cone mediation of the PLR. Melanopsin-mediated sustained PLRs were within normal limits. ERG showed the characteristic findings previously reported in this condition. Cone-mediated ERG responses were markedly decreased in amplitude. Rod-mediated ERG responses were absent for low-luminance stimuli (- 3 log cd s m-2), but had normal amplitude for stimuli of - 2 log cd s m-2 and above (although none were "supernormal"). The b-wave for the dark-adapted ISCEV standard - 2 log cd s m-2 stimulus was markedly delayed, whereas the b-wave timing was generally normal for higher flash luminances. CONCLUSIONS The abnormalities measured by pupillometry have a similar pattern to the outer-retinal abnormalities measured by ERG in KCNV2 retinopathy. These findings as well as the normal sustained PLR suggest that inner-retinal function may be preserved in KCNV2 retinopathy and highlight the potential for therapies designed to restore outer-retinal function in these individuals.
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Kutsuma T, Katagiri S, Hayashi T, Yoshitake K, Iejima D, Gekka T, Kohzaki K, Mizobuchi K, Baba Y, Terauchi R, Matsuura T, Ueno S, Iwata T, Nakano T. Novel biallelic loss-of-function KCNV2 variants in cone dystrophy with supernormal rod responses. Doc Ophthalmol 2019; 138:229-239. [PMID: 30877594 DOI: 10.1007/s10633-019-09679-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 02/09/2019] [Indexed: 10/27/2022]
Abstract
PURPOSE To report clinical and genetic features including long-term full-field electroretinography (FF-ERG) findings of a patient with cone dystrophy with supernormal rod responses (CDSRR). METHODS Ophthalmological medical records including FF-ERG were retrospectively reviewed. Genetic analysis using whole-exome sequencing (WES) was performed. Identified KCNV2 variants were confirmed by Sanger sequencing. RESULTS A 30-year-old female patient was referred to our hospital for assessment of decreased vision from childhood. Funduscopy showed macular atrophy in both eyes. FF-ERG showed decreased amplitudes and delayed peak time of b-waves for dark-adapted (DA) 0.01 ERG, increased b/a-wave ratio with a slightly diminished a-wave for DA 3.0 and DA 25.7 ERG, residual a-waves and almost extinguished b-waves for light-adapted (LA) 3.0 ERG, and extremely diminished amplitudes in LA 30-Hz flicker responses. At 45 years of age, funduscopy showed progressive macular atrophy, whereas the responses for her FF-ERG remained unchanged compared to those observed at 30 years of age. WES identified the compound heterozygous KCNV2 variants (p.W67X and p.D174GfsX198) in the patient. These variants have previously been unreported as pathogenic variants. Each parent had one of the variants. Subsequently, the patient was finally diagnosed with CDSRR with the novel compound heterozygous KCNV2 variants. CONCLUSIONS Biallelic loss-of-function KCNV2 variants (p.W67X and p.D174GfsX198) were identified as the cause of CDSRR. Long-term FF-ERG findings demonstrated there were no ERG changes during 15 years of observation, indicating that there was no evidence of progressive peripheral retinal dysfunction, in spite of worsening macular atrophy.
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Affiliation(s)
- Tomoko Kutsuma
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Satoshi Katagiri
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Takaaki Hayashi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan. .,Department of Ophthalmology, Katsushika Medical Center, The Jikei University School of Medicine, 6-41-2 Aoto, Katsushika-ku, Tokyo, 125-8506, Japan.
| | - Kazutoshi Yoshitake
- National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Daisuke Iejima
- National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Tamaki Gekka
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Kenichi Kohzaki
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Kei Mizobuchi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Yukari Baba
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Ryo Terauchi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Tomokazu Matsuura
- Department of Laboratory Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Shinji Ueno
- Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Takeshi Iwata
- National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Tadashi Nakano
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
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18
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The Role of the Voltage-Gated Potassium Channel Proteins Kv8.2 and Kv2.1 in Vision and Retinal Disease: Insights from the Study of Mouse Gene Knock-Out Mutations. eNeuro 2019; 6:eN-NWR-0032-19. [PMID: 30820446 PMCID: PMC6393689 DOI: 10.1523/eneuro.0032-19.2019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 02/01/2019] [Accepted: 02/04/2019] [Indexed: 11/21/2022] Open
Abstract
Mutations in the KCNV2 gene, which encodes the voltage-gated K+ channel protein Kv8.2, cause a distinctive form of cone dystrophy with a supernormal rod response (CDSRR). Kv8.2 channel subunits only form functional channels when combined in a heterotetramer with Kv2.1 subunits encoded by the KCNB1 gene. The CDSRR disease phenotype indicates that photoreceptor adaptation is disrupted. The electroretinogram (ERG) response of affected individuals shows depressed rod and cone activity, but what distinguishes this disease is the supernormal rod response to a bright flash of light. Here, we have utilized knock-out mutations of both genes in the mouse to study the pathophysiology of CDSRR. The Kv8.2 knock-out (KO) mice show many similarities to the human disorder, including a depressed a-wave and an elevated b-wave response with bright light stimulation. Optical coherence tomography (OCT) imaging and immunohistochemistry indicate that the changes in six-month-old Kv8.2 KO retinae are largely limited to the outer nuclear layer (ONL), while outer segments appear intact. In addition, there is a significant increase in TUNEL-positive cells throughout the retina. The Kv2.1 KO and double KO mice also show a severely depressed a-wave, but the elevated b-wave response is absent. Interestingly, in all three KO genotypes, the c-wave is totally absent. The differential response shown here of these KO lines, that either possess homomeric channels or lack channels completely, has provided further insights into the role of K+ channels in the generation of the a-, b-, and c-wave components of the ERG.
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19
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Rodriguez JD, Lane K, Hollander DA, Shapiro A, Saigal S, Hertsenberg AJ, Wallstrom G, Narayanan D, Angjeli E, Abelson MB. Cone photoreceptor macular function and recovery after photostress in early non-exudative age-related macular degeneration. Clin Ophthalmol 2018; 12:1325-1335. [PMID: 30100705 PMCID: PMC6067527 DOI: 10.2147/opth.s165658] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Purpose To identify parameters from cone function and recovery after photostress that detect functional deficits in early non-exudative age-related macular degeneration (AMD) and to determine the repeatability of these parameters. Methods Cone-mediated visual function recovery after photostress was examined in three groups of subjects: young normal subjects (ages 20–29; N=8), older normal subjects (ages 50–90; N=9), and early non-exudative AMD subjects (ages 50–90; N=12). Eight AMD and four normal subjects were retested 1 year after the initial evaluation. Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity (VA) and parameters of cone function (baseline cone sensitivity and cone recovery half-life following photobleach) were measured and compared between AMD and normal subjects. Short-term repeatability was assessed for each subject’s initial evaluation. Long-term repeatability was assessed by comparing outcomes from the initial evaluation and 1-year follow-up. Results The mean baseline cone threshold was significantly worse in subjects with early AMD compared to older normal subjects (−1.80±0.04 vs −1.57±0.06 log cd/m2p=0.0027). Moreover, the baseline cone threshold parameter exhibited good short-term (intraclass correlation coefficient [ICC]=0.88) and long-term (ICC=0.85) repeatability in all subjects. The cone intercept parameter and ETDRS VA were not significantly different between AMD and older normal subject groups. Cone recovery half-life was significantly different between older normal and AMD subject groups (p=0.041). Neither ETDRS VA nor cone function parameters were significantly different for any group at the 1-year follow-up. Conclusion The baseline cone threshold shows potential as a novel parameter to assess visual dysfunction in early AMD. This outcome consistently detected deficits in AMD subjects, and differentiated them from age-matched controls with high test–retest repeatability.
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Affiliation(s)
| | | | - David A Hollander
- Ora, Inc., Andover, MA, USA, .,Jules Stein Eye Institute, University of California, Los Angeles, CA, USA
| | | | | | | | | | | | | | - Mark B Abelson
- Ora, Inc., Andover, MA, USA, .,Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
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20
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Heteromeric K V2/K V8.2 Channels Mediate Delayed Rectifier Potassium Currents in Primate Photoreceptors. J Neurosci 2018; 38:3414-3427. [PMID: 29483285 DOI: 10.1523/jneurosci.2440-17.2018] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 01/18/2018] [Accepted: 02/11/2018] [Indexed: 01/17/2023] Open
Abstract
Silent voltage-gated potassium channel subunits (KVS) interact selectively with members of the KV2 channel family to modify their functional properties. The localization and functional roles of these silent subunits remain poorly understood. Mutations in the KVS subunit, KV8.2 (KCNV2), lead to severe visual impairment in humans, but the basis of these deficits remains unclear. Here, we examined the localization, native interactions, and functional properties of KV8.2-containing channels in mouse, macaque, and human photoreceptors of either sex. In human retina, KV8.2 colocalized with KV2.1 and KV2.2 in cone inner segments and with KV2.1 in rod inner segments. KV2.1 and KV2.2 could be coimmunoprecipitated with KV8.2 in retinal lysates indicating that these subunits likely interact directly. Retinal KV2.1 was less phosphorylated than cortical KV2.1, a difference expected to alter the biophysical properties of these channels. Using voltage-clamp recordings and pharmacology, we provide functional evidence for Kv2-containing channels in primate rods and cones. We propose that the presence of KV8.2, and low levels of KV2.1 phosphorylation shift the activation range of KV2 channels to align with the operating range of rod and cone photoreceptors. Our data indicate a role for KV2/KV8.2 channels in human photoreceptor function and suggest that the visual deficits in patients with KCNV2 mutations arise from inadequate resting activation of KV channels in rod and cone inner segments.SIGNIFICANCE STATEMENT Mutations in a voltage-gated potassium channel subunit, KV8.2, underlie a blinding inherited photoreceptor dystrophy, indicating an important role for these channels in human vision. Here, we have defined the localization and subunit interactions of KV8.2 channels in primate photoreceptors. We show that the KV8.2 subunit interacts with different Kv2 channels in rods and cones, giving rise to potassium currents with distinct functional properties. Our results provide a molecular basis for retinal dysfunction in patients with mutations in the KCNV2 gene encoding KV8.2.
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21
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Bocksteins E. Kv5, Kv6, Kv8, and Kv9 subunits: No simple silent bystanders. J Gen Physiol 2016; 147:105-25. [PMID: 26755771 PMCID: PMC4727947 DOI: 10.1085/jgp.201511507] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 12/11/2015] [Indexed: 12/19/2022] Open
Abstract
Members of the electrically silent voltage-gated K(+) (Kv) subfamilies (Kv5, Kv6, Kv8, and Kv9, collectively identified as electrically silent voltage-gated K(+) channel [KvS] subunits) do not form functional homotetrameric channels but assemble with Kv2 subunits into heterotetrameric Kv2/KvS channels with unique biophysical properties. Unlike the ubiquitously expressed Kv2 subunits, KvS subunits show a more restricted expression. This raises the possibility that Kv2/KvS heterotetramers have tissue-specific functions, making them potential targets for the development of novel therapeutic strategies. Here, I provide an overview of the expression of KvS subunits in different tissues and discuss their proposed role in various physiological and pathophysiological processes. This overview demonstrates the importance of KvS subunits and Kv2/KvS heterotetramers in vivo and the importance of considering KvS subunits and Kv2/KvS heterotetramers in the development of novel treatments.
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Affiliation(s)
- Elke Bocksteins
- Laboratory for Molecular Biophysics, Physiology, and Pharmacology, Department for Biomedical Sciences, University of Antwerp, 2610 Antwerp, Belgium
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22
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Renner AB, Dietrich-Ntoukas T, Jägle H. Recurrent episodes of night blindness in a patient with short bowel syndrome. Doc Ophthalmol 2015; 131:221-30. [PMID: 26507840 DOI: 10.1007/s10633-015-9516-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 10/20/2015] [Indexed: 02/02/2023]
Abstract
PURPOSE To describe clinical characteristics in a patient with recurrent episodes of night blindness due to vitamin A deficiency caused by short bowel syndrome in Crohn disease. METHODS Retrospective analysis of best-corrected visual acuity (BCVA), kinetic perimetry, slit-lamp biomicroscopy, ophthalmoscopy, fundus photography, fundus autofluorescence (FAF), spectral domain optical coherence tomography (SD-OCT), dark adaptometry (DA) and electroretinography (ERG). Serum vitamin A level was measured. RESULTS A 44-year-old man with a 3-year history of night blindness suffered from a short bowel syndrome with chronic malabsorption due to ileocecal resection in Crohn disease. Both eyes had a BCVA of 0.9, Bitot's spots of the conjunctiva and no significant fundus abnormalities. SD-OCT showed no remarkable changes, whereas FAF was brighter than normal in the center of the fovea. DA showed normal cone and a lack of rod function. The dark-adapted 0.01 ERG was non-detectable, the dark-adapted 3.0 ERG severely diminished, but the light-adapted 3.0 and 30 Hz flicker ERGs were within normal limits. Serum vitamin A level was 0.11 µg/ml (normal 0.30-0.65 µg/ml). Treatment with intravenous vitamin A caused a rapid recovery of night vision and ERG. However, during the following 3 years, he had three further episodes of night blindness with loss of rod function. During each period, parenteral vitamin A substitution brought complete recovery of night vision and rod function. BCVA, fundus, FAF findings and SD-OCT remained unchanged during the course. CONCLUSIONS In patients with known chronic malabsorption serum vitamin A level should be regularly checked to avoid recurrent night blindness episodes. ERG might be more sensitive than serum vitamin A level and is recommended in case of night blindness but still normal vitamin A level.
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Affiliation(s)
- Agnes B Renner
- Klinik und Poliklinik für Augenheilkunde, Universitätsklinikum Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany.
| | - Tina Dietrich-Ntoukas
- Klinik und Poliklinik für Augenheilkunde, Universitätsklinikum Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany.,Klinik für Augenheilkunde, Charité Universitätsmedizin Berlin, Campus Virchow-Klinikum, Mittelallee 4, Augustenburgerplatz 1, 13353, Berlin, Germany
| | - Herbert Jägle
- Klinik und Poliklinik für Augenheilkunde, Universitätsklinikum Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany
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23
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Zobor D, Zobor G, Kohl S. Achromatopsia: on the doorstep of a possible therapy. Ophthalmic Res 2015; 54:103-8. [PMID: 26304472 DOI: 10.1159/000435957] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 06/15/2015] [Indexed: 11/19/2022]
Abstract
Achromatopsia (ACHM) is a rare autosomal recessive inherited retinal disorder with an incidence of approximately 1 in 30,000. It presents at birth or early infancy and is typically characterized by reduced visual acuity, nystagmus, photophobia, and very poor or absent color vision. The symptoms arise from isolated cone dysfunction, which can be caused by mutations in the crucial components of the cone phototransduction cascade. Although ACHM is considered a functionally nonprogressive disease affecting only the cone system, recent studies have described progressive age-dependent changes in retinal architecture. Currently, no specific therapy is available for ACHM; however, gene replacement therapy performed on animal models for three ACHM genes has shown promising results. Accurate genetic and clinical diagnosis of patients may therefore enhance and enable therapeutic intervention in the near future. This short review summarizes the genetic background, pathophysiology, clinical findings, diagnostics, and therapeutic perspectives in ACHM.
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Affiliation(s)
- Ditta Zobor
- Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
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24
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Grigg JR, Holder GE, Billson FA, Korsakova M, Jamieson RV. The importance of electrophysiology in revealing a complete homozygous deletion of KCNV2. J AAPOS 2013; 17:641-3. [PMID: 24210337 DOI: 10.1016/j.jaapos.2013.08.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 08/26/2013] [Indexed: 11/26/2022]
Abstract
Visual electrophysiology is an important ancillary investigation in children with poor vision and nystagmus. Cone dystrophy with supranormal rod electroretinogram (KCNV2 retinopathy) has pathognomonic electrophysiology findings that, if identified, direct molecular genetic testing. We report the case of a 6-year-old boy with typical electrophysiology findings of KCNV2 retinopathy but with abnormal cone dysfunction compared to other patients with mutations in KCNV2. Molecular genetic testing revealed complete homozygous deletion of KCNV2. To our knowledge, this is the first such report. The greater cone dysfunction seen in this case suggests a phenotypic link to the genetic changes.
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Affiliation(s)
- John R Grigg
- Save Sight Institute, Discipline of Ophthalmology, Sydney Eye Hospital Campus, The University of Sydney, Sydney, Australia.
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25
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Fujinami K, Tsunoda K, Nakamura N, Kato Y, Noda T, Shinoda K, Tomita K, Hatase T, Usui T, Akahori M, Itabashi T, Iwata T, Ozawa Y, Tsubota K, Miyake Y. Molecular characteristics of four Japanese cases with KCNV2 retinopathy: report of novel disease-causing variants. Mol Vis 2013; 19:1580-90. [PMID: 23885164 PMCID: PMC3718491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 07/15/2013] [Indexed: 12/02/2022] Open
Abstract
PURPOSE To describe the molecular characteristics of four Japanese patients with cone dystrophy with supernormal rod responses (CDSRR). METHODS Four individuals with a clinical and electrophysiological diagnosis of CDSRR were ascertained. The pathognomonic findings of the full-field electroretinograms (ERGs) included a decrease in the rod responses, a square-shaped a-wave, an excessive increase in the b-wave in the bright flash responses, and decreased cone-derived responses. Mutational screening of the coding regions and flanking intronic sequences of the potassium channel, subfamily V, member 2 (KCNV2) gene was performed with bidirectional sequencing. The segregation of each allele was confirmed by screening other family members. Subsequent in silico analyses of the mutational consequences for protein function were performed. RESULTS There were two siblings from one family and one case in each of the two families. One family had a consanguineous marriage. Mutational screening revealed compound heterozygosity for the two alleles, p.C177R and p.G461R, in three patients, and homozygosity for complex alleles, p.R27H and p.R206P, in one patient from the consanguineous family. There were three putative novel variants, p.R27H, p.C177R, and p.R206P. The four variants in the families with KCNV2 were highly conserved in other species. In silico analyses predicted that all of the missense variants would alter protein function. CONCLUSIONS Biallelic disease-causing variants were identified in four Japanese patients with CDSRR suggesting that the pathognomonic electrophysiological features are helpful in making a molecular diagnosis of KCNV2. Three novel variants were identified, and we conclude that there may be a distinct spectrum of KCNV2 alleles in the Japanese population.
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Affiliation(s)
- Kaoru Fujinami
- National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan,Department of Ophthalmology, Keio University, School of Medicine, Tokyo, Japan
| | - Kazushige Tsunoda
- National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
| | - Natsuko Nakamura
- National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
| | - Yu Kato
- National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
| | - Toru Noda
- National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
| | - Kei Shinoda
- School of Medicine, Teikyo University, Tokyo, Japan
| | | | - Tetsuhisa Hatase
- Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
| | | | - Masakazu Akahori
- National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
| | - Takeshi Itabashi
- National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
| | - Takeshi Iwata
- National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
| | - Yoko Ozawa
- Department of Ophthalmology, Keio University, School of Medicine, Tokyo, Japan
| | - Kazuo Tsubota
- Department of Ophthalmology, Keio University, School of Medicine, Tokyo, Japan
| | - Yozo Miyake
- National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan,Aichi Medical University, Aichi, Japan
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