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Sato T, Kuniyoshi K, Hayashi T, Nishiwaki H, Mizobuchi K, Kusaka S. Clinical course of two siblings with potassium voltage-gated channel modifier subfamily V member 2 (KCNV2)-associated retinopathy. Doc Ophthalmol 2024; 148:173-182. [PMID: 38630375 DOI: 10.1007/s10633-024-09971-0] [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: 03/15/2023] [Accepted: 03/15/2024] [Indexed: 08/10/2024]
Abstract
BACKGROUND KCNV2-associated retinopathy causes a phenotype reported as "cone dystrophy with nyctalopia and supernormal rod responses (CDSRR; OMIM# 610356)," featuring pathognomonic findings on electroretinography (ERG). Here, we report the clinical courses of two siblings with CDSRR. CASE REPORTS Patient 1: A 3-year-old boy with intermittent exophoria was referred to our hospital. The patient's decimal best-corrected visual acuity (BCVA) at age 6 was 0.7 and 0.7 in the right and left eyes, respectively. Photophobia and night blindness were also observed. Because the ERG showed a delayed and supernormal b-wave with a "squaring (trough-flattened)" a-wave in the DA-30 ERG, and CDSRR was diagnosed. The patient's vision gradually worsened, and faint bilateral bull's eye maculopathy was observed at the age of 27 years, although the fundi were initially unremarkable. Genetic examination revealed a homozygous missense variant, c.529T > C (p.Cys177Arg), in the KCNV2 gene. Patient 2: The second patient was Patient 1's younger sister, who was brought to our hospital at 3 years of age. The patient presented with exotropia, mild nystagmus, photophobia, night blindness, and color vision abnormalities. The patients' decimal BCVA at age 13 was 0.6 and 0.4 in the right and left eyes, respectively, and BCVA gradually decreased until the age of 24 years. The fundi were unremarkable. The siblings had similar ERG findings and the same homozygous missense variant in the KCNV2 gene. CONCLUSIONS The siblings had clinical findings typical of CDSRR. High-intense flash ERG is recommended for identifying pathognomonic "squaring" a-waves in patients with CDSRR.
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Affiliation(s)
- Tomoko Sato
- Department of Ophthalmology, Faculty of Medicine, Kindai University, Osaka-Sayama, Japan
| | - Kazuki Kuniyoshi
- Department of Ophthalmology, Faculty of Medicine, Kindai University, Osaka-Sayama, Japan.
| | - Takaaki Hayashi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | | | - Kei Mizobuchi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Shunji Kusaka
- Department of Ophthalmology, Faculty of Medicine, Kindai University, Osaka-Sayama, Japan
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Yang TH, Kang EYC, Lin PH, Wu PL, Sachs JA, Wang NK. The Value of Electroretinography in Identifying Candidate Genes for Inherited Retinal Dystrophies: A Diagnostic Guide. Diagnostics (Basel) 2023; 13:3041. [PMID: 37835784 PMCID: PMC10572658 DOI: 10.3390/diagnostics13193041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 09/08/2023] [Accepted: 09/13/2023] [Indexed: 10/15/2023] Open
Abstract
Inherited retinal dystrophies (IRDs) are a group of heterogeneous diseases caused by genetic mutations that specifically affect the function of the rod, cone, or bipolar cells in the retina. Electroretinography (ERG) is a diagnostic tool that measures the electrical activity of the retina in response to light stimuli, and it can help to determine the function of these cells. A normal ERG response consists of two waves, the a-wave and the b-wave, which reflect the activity of the photoreceptor cells and the bipolar and Muller cells, respectively. Despite the growing availability of next-generation sequencing (NGS) technology, identifying the precise genetic mutation causing an IRD can be challenging and costly. However, certain types of IRDs present with unique ERG features that can help guide genetic testing. By combining these ERG findings with other clinical information, such as on family history and retinal imaging, physicians can effectively narrow down the list of candidate genes to be sequenced, thereby reducing the cost of genetic testing. This review article focuses on certain types of IRDs with unique ERG features. We will discuss the pathophysiology and clinical presentation of, and ERG findings on, these disorders, emphasizing the unique role ERG plays in their diagnosis and genetic testing.
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Affiliation(s)
- Tsai-Hsuan Yang
- Department of Education, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan 33305, Taiwan;
- College of Medicine, National Yang Ming Chiao Tung University, Taipei 11217, Taiwan
| | - Eugene Yu-Chuan Kang
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan 33305, Taiwan;
- College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Pei-Hsuan Lin
- National Taiwan University Hospital, Yunlin 640203, Taiwan;
- Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University Irving Medical Center, Columbia University, New York, NY 10032, USA; (P.-L.W.); (J.A.S.)
| | - Pei-Liang Wu
- Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University Irving Medical Center, Columbia University, New York, NY 10032, USA; (P.-L.W.); (J.A.S.)
- Department of Medicine, National Taiwan University, Taipei 10617, Taiwan
| | - Jacob Aaron Sachs
- Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University Irving Medical Center, Columbia University, New York, NY 10032, USA; (P.-L.W.); (J.A.S.)
- College of Arts and Sciences, University of Miami, Coral Gables, FL 33146, USA
| | - Nan-Kai Wang
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan 33305, Taiwan;
- College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
- Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University Irving Medical Center, Columbia University, New York, NY 10032, USA; (P.-L.W.); (J.A.S.)
- Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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Liu PK, Ryu J, Yeh LK, Chen KJ, Tsang SH, Liu L, Wang NK. A novel KCNV2 mutation in a patient taking hydroxychloroquine associated with cone dystrophy with supernormal rod response. Ophthalmic Genet 2021; 42:458-463. [PMID: 33960280 DOI: 10.1080/13816810.2021.1920039] [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: 10/21/2022]
Abstract
BACKGROUND Cone dystrophy with supernormal rod response (CDSRR) is a rare inherited retinal degeneration. A patient superimposed with medical conditions requiring use of hydroxychloroquine (HCQ) may obscure accurate diagnosis of CDSRR. Herein, we report a referral case for HCQ retinopathy screening. Comprehensive ophthalmic examinations, however, guided the diagnosis of CDSRR from a novel mutation in potassium voltage-gated channel modifier subfamily V member 2 (KCNV2) gene. MATERIALS AND METHODS Comprehensive ophthalmic examinations were evaluated for two patients whose parents are first cousins. Direct sanger sequencing of KCNV2 was applied to confirm the mutation. RESULTS A 38-year-old male proband was referred for HCQ retinopathy screening after taking HCQ for systemic lupus erythematosus (SLE). Fundus examination showed bull's eye pattern, and photoreceptor loss in the foveal region of both eyes was noted on spectral domain-optical coherence tomography (SD-OCT). The full-field electroretinography (ffERG) revealed a disproportionate increase in scotopic maximal response with implicit time delay, as well as universal cone dysfunction. Proband's 24-year-old sister had similar ffERG pattern in both eyes. Direct sanger sequencing of KCNV2 gene revealed a novel homozygous mutation c.280_281 insG (p.Ala94GlyfsTer278), confirming a diagnosis of CDSRR. CONCLUSIONS We report a novel KCNV2 mutation in a consanguineous family. The unique ffERG features of CDSRR are pathognomonic and thus crucial in guiding clinicians toward genetic testing of the KCNV2 gene. Altogether, multimodal imaging, ffERG, and detailed history taking are important diagnostic tools for differentiating between acquired and inherited retinal disorders.
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Affiliation(s)
- Pei-Kang Liu
- Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University, New York, New York, USA.,Department of Ophthalmology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.,School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.,Institute of Biomedical Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Joseph Ryu
- Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University, New York, New York, USA
| | - Lung-Kun Yeh
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Kuan-Jen Chen
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Stephen H Tsang
- Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University, New York, New York, USA
| | - Laura Liu
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Nan-Kai Wang
- Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University, New York, New York, USA
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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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Hou X, Guo Y, Liu J, Li S, Fan W, Lin M, Rokohl AC, Heindl LM. A Systematic Review of the Clinical Manifestations and Diagnostic Methods for Macular Coloboma. Curr Eye Res 2021; 46:913-918. [PMID: 33478254 DOI: 10.1080/02713683.2020.1853779] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Objectives: To present the clinical features of and diagnostic methods used for macular coloboma (MC), and to analyze the factors associated with best-corrected visual acuity (BCVA) in patients with MC.Methods: A systematic review using the MEDLINE (PubMed), EMBASE, LILACS, and Cochrane databases was performed. The factors associated with BCVA were analyzed.Results: A total of 21 patients (mean age at diagnosis, 18.1 ± 14.6 years) with 36 eyes affected by MC (5 unilateral, 16 bilateral) were included in the study. All 21 patients (100%) had undergone a good-quality fundus examination. The size of the MC lesions ranged from 1.0 × 1.2 to 4.0 × 4.0 disc diameters (DD). Twenty-seven (73%) eyes had pigmented MC, seven (19%) had non-pigmented MC, and one (3%) had an unspecific type. The diagnosis was confirmed using spectral-domain optical coherence tomography (SD-OCT) in 16 (43.2%) eyes. A positive correlation was found between BCVA and the type of MC (β = 0.876, p = .006) and abnormal eye movement (β = 0.087, p = .018), and a negative correlation was found between BCVA and a contributory medical history of ventricular septal defect (β = -0.327, p = .001).Conclusions: Pigmented MC was the most common type and had the highest possibility of causing impaired vision in the affected eyes. Additionally, joint examinations should be applied for diagnostic confirmation of MC. Furthermore, fundoscopy, electroretinogram, electrooculography, fundus fluorescein angiography, and SD-OCT are all critical for differential diagnosis of MC-like lesions.
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Affiliation(s)
- Xiaoyi Hou
- Department of Ophthalmology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Yongwei Guo
- Eye Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Jinhua Liu
- Department of Ophthalmology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Senmao Li
- Department of Ophthalmology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Wanlin Fan
- Department of Ophthalmology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Ming Lin
- Department of Ophthalmology, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Alexander C Rokohl
- Department of Ophthalmology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Ludwig M Heindl
- Department of Ophthalmology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany.,Center for Integrated Oncology (CIO) Aachen-Bonn-Cologne-Duesseldorf, Cologne, Germany
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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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