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Li JX, Meng LR, Hou BK, Hao XL, Wang DJ, Qu LH, Li ZH, Zhang L, Jin X. Detection of Novel BEST1 Variations in Autosomal Recessive Bestrophinopathy Using Third-generation Sequencing. Curr Med Sci 2024; 44:419-425. [PMID: 38619684 DOI: 10.1007/s11596-024-2865-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 03/07/2024] [Indexed: 04/16/2024]
Abstract
OBJECTIVE Autosomal recessive bestrophinopathy (ARB), a retinal degenerative disease, is characterized by central visual loss, yellowish multifocal diffuse subretinal deposits, and a dramatic decrease in the light peak on electrooculogram. The potential pathogenic mechanism involves mutations in the BEST1 gene, which encodes Ca2+-activated Cl- channels in the retinal pigment epithelium (RPE), resulting in degeneration of RPE and photoreceptor. In this study, the complete clinical characteristics of two Chinese ARB families were summarized. METHODS Pacific Biosciences (PacBio) single-molecule real-time (SMRT) sequencing was performed on the probands to screen for disease-causing gene mutations, and Sanger sequencing was applied to validate variants in the patients and their family members. RESULTS Two novel mutations, c.202T>C (chr11:61722628, p.Y68H) and c.867+97G>A, in the BEST1 gene were identified in the two Chinese ARB families. The novel missense mutation BEST1 c.202T>C (p.Y68H) resulted in the substitution of tyrosine with histidine in the N-terminal region of transmembrane domain 2 of bestrophin-1. Another novel variant, BEST1 c.867+97G>A (chr11:61725867), located in intron 7, might be considered a regulatory variant that changes allele-specific binding affinity based on motifs of important transcriptional regulators. CONCLUSION Our findings represent the first use of third-generation sequencing (TGS) to identify novel BEST1 mutations in patients with ARB, indicating that TGS can be a more accurate and efficient tool for identifying mutations in specific genes. The novel variants identified further broaden the mutation spectrum of BEST1 in the Chinese population.
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Affiliation(s)
- Jia-Xun Li
- Department of Senior Ophthalmology, the Third Medical Center of PLA General Hospital, Beijing, 100853, China
| | - Ling-Rui Meng
- Department of Senior Ophthalmology, the Third Medical Center of PLA General Hospital, Beijing, 100853, China
| | - Bao-Ke Hou
- Department of Senior Ophthalmology, the Third Medical Center of PLA General Hospital, Beijing, 100853, China
| | - Xiao-Lu Hao
- Department of Senior Ophthalmology, the Third Medical Center of PLA General Hospital, Beijing, 100853, China
| | - Da-Jiang Wang
- Department of Senior Ophthalmology, the Third Medical Center of PLA General Hospital, Beijing, 100853, China
| | - Ling-Hui Qu
- Department of Ophthalmology, the 74th Army Group Hospital, Guangzhou, 510318, China
| | - Zhao-Hui Li
- Department of Senior Ophthalmology, the Third Medical Center of PLA General Hospital, Beijing, 100853, China
| | - Lei Zhang
- Department of Senior Ophthalmology, the Third Medical Center of PLA General Hospital, Beijing, 100853, China
| | - Xin Jin
- Department of Senior Ophthalmology, the Third Medical Center of PLA General Hospital, Beijing, 100853, China.
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Beryozkin A, Sher I, Ehrenberg M, Zur D, Newman H, Gradstein L, Simaan F, Rotenstreich Y, Goldenberg-Cohen N, Bahar I, Blumenfeld A, Rivera A, Rosin B, Deitch-Harel I, Perlman I, Mechoulam H, Chowers I, Leibu R, Ben-Yosef T, Pras E, Banin E, Sharon D, Khateb S. Best Disease: Global Mutations Review, Genotype-Phenotype Correlation, and Prevalence Analysis in the Israeli Population. Invest Ophthalmol Vis Sci 2024; 65:39. [PMID: 38411968 PMCID: PMC10910552 DOI: 10.1167/iovs.65.2.39] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 02/04/2024] [Indexed: 02/28/2024] Open
Abstract
Purpose To review all reported disease-causing mutations in BEST1, perform genotype-phenotype correlation, and estimate disease prevalence in the Israeli population. Methods Medical records of patients diagnosed with Best disease and allied diseases from nine Israeli medical centers over the past 20 years were collected, as were clinical data including ocular findings, electrophysiology results, and retina imaging. Mutation detection involved mainly whole exome sequencing and candidate gene analysis. Demographic data were obtained from the Israeli Bureau of Statistics (January 2023). A bibliometric study was also conducted to gather mutation data from online sources. Results A total of 134 patients were clinically diagnosed with Best disease and related conditions. The estimated prevalence of Best disease was calculated to be 1 in 127,000, with higher rates among Arab Muslims (1 in 76,000) than Jews (1 in 145,000). Genetic causes were identified in 76 individuals (57%), primarily showing autosomal-dominant inheritance due to BEST1 mutations (58 patients). Critical conserved domains were identified consisting of a high percentage of dominant missense mutations, primarily in transmembrane domains and the intracellular region (Ca2+ binding domain) of the BEST1 protein. Conclusions This study represents the largest cohort of patients with Best disease reported in Israel and globally. The prevalence in Israel is akin to that in Denmark but is lower than that in the United States. Critical conserved domains within the BEST1 protein are pivotal for normal functioning, and even minor missense alterations in these areas lead to a dominant disease manifestation. Genetic testing is indispensable as the gold standard for Best disease diagnosis due to the variable clinical presentation of the disease.
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Affiliation(s)
- Avigail Beryozkin
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Ifat Sher
- Goldschleger Eye Institute, Sheba Medical Center, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Miriam Ehrenberg
- Ophthalmology Unit, Schneider Children's Medical Center, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Dinah Zur
- Ophthalmology Division, Tel Aviv Medical Center, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Hadas Newman
- Ophthalmology Division, Tel Aviv Medical Center, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Libe Gradstein
- Department of Ophthalmology, Soroka Medical Center and Clalit Health Services, Faculty of Health Sciences, Ben-Gurion University, Be'er Sheva, Israel
| | - Francis Simaan
- Department of Ophthalmology, Assaf Harofeh Medical Center, Zerifin, Israel
| | - Ygal Rotenstreich
- Goldschleger Eye Institute, Sheba Medical Center, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Nitza Goldenberg-Cohen
- Department of Ophthalmology, Bnai Zion Medical Center, Haifa, Israel
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Irit Bahar
- Ophthalmology Division, Tel Aviv Medical Center, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Ophthalmology Department and Laboratory of Eye Research, Felsenstein Medical Research Center, Rabin Medical Center, Petach Tikva, Israel
| | - Anat Blumenfeld
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Antonio Rivera
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Boris Rosin
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Iris Deitch-Harel
- Ophthalmology Department and Laboratory of Eye Research, Felsenstein Medical Research Center, Rabin Medical Center, Petach Tikva, Israel
| | - Ido Perlman
- Ophthalmology Division, Tel Aviv Medical Center, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Hadas Mechoulam
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Itay Chowers
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Rina Leibu
- Department of Ophthalmology, Rambam Health Care Center, Haifa, Israel
| | - Tamar Ben-Yosef
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Eran Pras
- Department of Ophthalmology, Assaf Harofeh Medical Center, Zerifin, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Eyal Banin
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Dror Sharon
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Samer Khateb
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
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Kerschensteiner D. Losing, preserving, and restoring vision from neurodegeneration in the eye. Curr Biol 2023; 33:R1019-R1036. [PMID: 37816323 PMCID: PMC10575673 DOI: 10.1016/j.cub.2023.08.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2023]
Abstract
The retina is a part of the brain that sits at the back of the eye, looking out onto the world. The first neurons of the retina are the rod and cone photoreceptors, which convert changes in photon flux into electrical signals that are the basis of vision. Rods and cones are frequent targets of heritable neurodegenerative diseases that cause visual impairment, including blindness, in millions of people worldwide. This review summarizes the diverse genetic causes of inherited retinal degenerations (IRDs) and their convergence onto common pathogenic mechanisms of vision loss. Currently, there are few effective treatments for IRDs, but recent advances in disparate areas of biology and technology (e.g., genome editing, viral engineering, 3D organoids, optogenetics, semiconductor arrays) discussed here enable promising efforts to preserve and restore vision in IRD patients with implications for neurodegeneration in less approachable brain areas.
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Affiliation(s)
- Daniel Kerschensteiner
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Li Y, Bracha P, Aleman TS, Brucker AJ. ADULT-ONSET BEST1 -VITELLIFORM DYSTROPHY ASSOCIATED WITH ANGIOID STREAK-LIKE CHANGES IN TWO SIBLINGS. Retin Cases Brief Rep 2023; 17:256-260. [PMID: 34001763 DOI: 10.1097/icb.0000000000001164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND/PURPOSE To describe the association between autosomal dominant Best disease and peripapillary angioid streak-like changes. METHODS Case report of two siblings. RESULTS A 76-year-old White man was referred for evaluation of bilateral macular changes and worsening visual distortion over the preceding 2 years. Best-corrected visual acuity measured 20/30 in the right eye and 20/80 in the left eye. Funduscopic examination revealed multifocal yellow lesions in the posterior pole that were hyperautofluorescent on short-wavelength excitation and corresponded with subretinal hyperreflective material on optical coherence tomography. The posterior pole examination was interesting because of the juxtapapillary involvement of the vitelliform lesions and the presence of bilateral peripapillary angioid streak-like changes despite no history of conditions associated with angioid streaks. On further workup, an electrooculogram revealed reduced Arden ratios and a known heterozygous missense mutation in BEST1 (c.903T>G; p .D301E) was found. The patient's 69-year-old younger brother was brought in and found to have a remarkably similar phenotype, including the presence of angioid streak-like changes associated with the same BEST1 mutation. CONCLUSION These two cases demonstrate the possibility of late-onset multifocal vitelliform disease due to dominantly inherited BEST1 . A consistent phenotype in this family with macular lesions extending into the peripapillary region, associated with angioid streak-like changes, suggests susceptibility of this region to changes in dominant BEST1 -vitelliform macular dystrophy.
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Affiliation(s)
- Yafeng Li
- Department of Ophthalmology, Scheie Eye Institute, Perelman School of Medicine of the University of Pennsylvania, Philadelphia, Pennsylvania. Dr. P. Bracha is now at Gundersen Eye Institute, Gundersen Health System, La Crosse, Wisconsin
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Haque OI, Chandrasekaran A, Nabi F, Ahmad O, Marques JP, Ahmad T. A novel compound heterozygous BEST1 gene mutation in two siblings causing autosomal recessive bestrophinopathy. BMC Ophthalmol 2022; 22:493. [PMID: 36527004 PMCID: PMC9756692 DOI: 10.1186/s12886-022-02703-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 11/23/2022] [Indexed: 12/23/2022] Open
Abstract
PURPOSE To describe the clinical features, imaging characteristics, and genetic test results associated with a novel compound heterozygous mutation of the BEST1 gene in two siblings with autosomal recessive bestrophinopathy. METHODS Two siblings underwent a complete ophthalmic examination, including dilated fundus examination, fundus photography, fundus autofluorescence imaging, spectral-domain optical coherence tomography, fluorescein angiography, electroretinography, and electrooculography. A clinical diagnosis of autosomal recessive bestrophinopathy was established based on ocular examination and multimodal retinal imaging. Subsequently, clinical exome sequencing consisting of a panel of 6670 genes was carried out to confirm the diagnosis and assess genetic alterations in the protein-coding region of the genome of the patients. The identified mutations were tested in the two affected siblings and one of their parents. RESULTS Two siblings (a 17-year-old female and a 15-year-old male) presented with reduced visual acuity and bilaterally symmetrical subretinal deposits of hyperautofluorescent materials in the posterior pole, which showed staining in the late phase of fluorescein angiogram. Spectral-domain optical coherence tomography demonstrated hyperreflective subretinal deposits and subretinal fluid accumulation. Both patients shared two mutations in the protein-coding region of the BEST1 gene, c.103G > A, p.(Glu35Lys) and c.313C > A, p.(Arg105Ser) (a novel disease-causing mutation). Sanger sequencing confirmed that the unaffected mother of the proband was carrying p.(Glu35Lys) variant in a heterozygous state. CONCLUSIONS We have identified and described the phenotype of a novel disease-causing mutation NM_004183.4:c.313C > A, p.(Arg105Ser) in a heterozygous state along with a previously reported mutation NM_004183.4:c.103G > A, p.(Glu35Lys) of the BEST1 gene in two related patients with autosomal recessive bestrophinopathy.
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Affiliation(s)
| | | | - Faisal Nabi
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
| | - Owais Ahmad
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India
| | - João Pedro Marques
- Ophthalmology Unit, Centro Hospitalar E Universitário de Coimbra (CHUC), Coimbra, Portugal
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Wang Y, Jiang Y, Li X, Xiao X, Li S, Sun W, Wang P, Zhang Q. Genetic and clinical features of BEST1-associated retinopathy based on 59 Chinese families and database comparisons. Exp Eye Res 2022; 223:109217. [PMID: 35973442 DOI: 10.1016/j.exer.2022.109217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 07/20/2022] [Accepted: 08/08/2022] [Indexed: 11/04/2022]
Abstract
Variants in BEST1 are one of the most common cause of retinopathy mainly involving the retinal pigment epithelium with both dominant and recessive traits. This study aimed to describe the characteristics of potential pathogenic variants (PPVs) in BEST1 and their associated clinical features. Variants in BEST1 were collected from our in-house exome sequencing data and systematically evaluated by in silico prediction tools as well as genotype-phenotype analysis. The pathogenicity features of the BEST1 variants were further assessed through database comparison among the in-house data, Genome Aggregation Database from the general population, and all previously published literature. The clinical information of the in-house patients was summarized. The PPVs in BEST1 were identified in 66 patients from 59 families, including 32 families with Best vitelliform macular dystrophy (BVMD) and 27 families with autosomal recessive bestrophinopathy (ARB). These PPVs included 31 missense variants, seven truncation variants, one in-frame deletion, and a known 3-untranslated region variant. All the truncations detected in our study were exclusively involved in ARB but not BVMD. Among the 31 missense variants, 18 missenses associated with BVMD in the dominant trait were clustered in four hotspot regions with statistically significant differences from the recessive missenses. Except for distinct macular changes, there were no statistically significant differences among the other associated clinical features between BVMD and ARB, including peripheral retinopathy, high hyperopia, and angle-closure glaucoma. In conclusion, BEST1-associated dominant retinopathy was preferentially caused by missense variants located in important functional regions. Truncations were most likely benign in heterozygous status. Future studies are expected to elucidate the mystery of the same missense variants contributing to both BVMD and ARB.
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Affiliation(s)
- Yingwei Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Yi Jiang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Xueqing Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Xueshan Xiao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Shiqiang Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Wenmin Sun
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Panfeng Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Qingjiong Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China.
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Impaired Bestrophin Channel Activity in an iPSC-RPE Model of Best Vitelliform Macular Dystrophy (BVMD) from an Early Onset Patient Carrying the P77S Dominant Mutation. Int J Mol Sci 2022; 23:ijms23137432. [PMID: 35806438 PMCID: PMC9266689 DOI: 10.3390/ijms23137432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 07/01/2022] [Indexed: 01/25/2023] Open
Abstract
Best Vitelliform Macular dystrophy (BVMD) is the most prevalent of the distinctive retinal dystrophies caused by mutations in the BEST1 gene. This gene, which encodes for a homopentameric calcium-activated ion channel, is crucial for the homeostasis and function of the retinal pigment epithelia (RPE), the cell type responsible for recycling the visual pigments generated by photoreceptor cells. In BVMD patients, mutations in this gene induce functional problems in the RPE cell layer with an accumulation of lipofucsin that evolves into cell death and loss of sight. In this work, we employ iPSC-RPE cells derived from a patient with the p.Pro77Ser dominant mutation to determine the correlation between this variant and the ocular phenotype. To this purpose, gene and protein expression and localization are evaluated in iPSC-RPE cells along with functional assays like phagocytosis and anion channel activity. Our cell model shows no differences in gene expression, protein expression/localization, or phagocytosis capacity, but presents an increased chloride entrance, indicating that the p.Pro77Ser variant might be a gain-of-function mutation. We hypothesize that this variant disturbs the neck region of the BEST1 channel, affecting channel function but maintaining cell homeostasis in the short term. This data shed new light on the different phenotypes of dominant mutations in BEST1, and emphasize the importance of understanding its molecular mechanisms. Furthermore, the data widen the knowledge of this pathology and open the door for a better diagnosis and prognosis of the disease.
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8
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Self-organization and surface properties of hBest1 in models of biological membranes. Adv Colloid Interface Sci 2022; 302:102619. [PMID: 35276535 DOI: 10.1016/j.cis.2022.102619] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 02/19/2022] [Accepted: 02/20/2022] [Indexed: 11/22/2022]
Abstract
The transmembrane Ca2+ - activated Cl- channel - human bestrophin-1 (hBest1) is expressed in retinal pigment epithelium and mutations of BEST1 gene cause ocular degenerative diseases colectivelly referred to as "bestrophinopathies". A large number of genetical, biochemical, biophysical and molecular biological studies have been performed to understand the relationship between structure and function of the hBest1 protein and its pathophysiological significance. Here, we review the current understanding of hBest1 surface organization, interactions with membrane lipids in model membranes, and its association with microdomains of cellular membranes. These highlights are significant for modulation of channel activity in cells.
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Chowdhury S, Duvesh R, Kumaran M, Anjanamurthy R, Kumar J, Vanniarajan A, Devarajan B, Sundaresan P. Clinical reassessments and whole-exome sequencing uncover novel BEST1 mutation associated with bestrophinopathy phenotype. Ophthalmic Genet 2021; 43:191-200. [PMID: 34751623 DOI: 10.1080/13816810.2021.1998553] [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: 10/19/2022]
Abstract
BACKGROUND The diagnosis of retinal dystrophies can be challenging due to the spectrum of protean phenotypic manifestations. This study employed trio-whole-exome sequencing (trio-WES) to unveil the genetic cause of an inherited retinal disorder in a south Indian family. MATERIALS AND METHODS Proband's initial ophthalmic examinations was performed in the year 2016. WES was performed on a proband-parent trio to identify causative mutation followed by Sanger validation, segregation analysis, sequence and structure-based computational analysis to assess its pathogenicity. Based on the genetic findings, detailed clinical reassessments were performed in year 2020 for the proband and available family members. RESULTS WES revealed a novel homozygous BEST1 mutation c.G310A (p.D104N) in the proband and heterozygous for the parents, indicating autosomal recessive inheritance. Segregation analysis showed heterozygous mutation in maternal grandfather and normal genotype for younger brother and maternal grandmother. Moreover, the structure-based analysis revealed the mutation p.D104N in the cytoplasmic domain, causing structural hindrance by altering hydrogen bonds and destabilizing the BEST1 protein structure. Proband's clinical assessments were consistent with autosomal recessive bestrophinopathy (ARB) phenotype. Additionally, characteristic absent light rise and decreased light peak-to-dark trough ratio (LP:DT) was observed bilaterally in EOG. CONCLUSIONS Our study demonstrates the utility of WES and clinical re-evaluations in establishing the precise diagnosis of autosomal recessive bestrophinopathy associated with a novel mutation, thus expanding the BEST1-related mutation spectrum.
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Affiliation(s)
- Susmita Chowdhury
- Department of Genetics, Aravind Medical Research Foundation, Madurai, India.,Department of Molecular Biology, Aravind Medical Research Foundation - Affiliated to Alagappa University, Karaikudi, India
| | - Roopam Duvesh
- Department of Genetics, Aravind Medical Research Foundation, Madurai, India
| | - Manojkumar Kumaran
- Department of Bioinformatics, Aravind Medical Research Foundation, Madurai, India.,School of Chemical and Biotechnology, SASTRA (Deemed to Be University), Thanjavur, India
| | - Rupa Anjanamurthy
- Department of Paediatric Ophthalmology & Adult Strabismus Services, Aravind Eye Hospital, Madurai, India
| | - Jayant Kumar
- Department of Vitreo-Retina Services, Aravind Eye Hospital, Madurai, India
| | - Ayyasamy Vanniarajan
- Department of Molecular Genetics, Aravind Medical Research Foundation, Madurai, India
| | | | - Periasamy Sundaresan
- Department of Genetics, Aravind Medical Research Foundation, Madurai, India.,Department of Molecular Biology, Aravind Medical Research Foundation - Affiliated to Alagappa University, Karaikudi, India
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Lin Y, Li T, Liu B, Lyu C, Lian Y, Li J, Huang Y, Li H, Wu Q, Jin C, Lu L. Multimodal imaging and genetic analysis of adult-onset best vitelliform macular dystrophy in Chinese patients. Exp Ther Med 2021; 22:1034. [PMID: 34373720 PMCID: PMC8343652 DOI: 10.3892/etm.2021.10466] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 06/16/2021] [Indexed: 01/09/2023] Open
Abstract
Compared to juvenile-onset best vitelliform macular dystrophy (BVMD), adult-onset BVMD is not well characterized and lacks strict diagnostic criteria. The present study aimed to evaluate the clinical and genetic characteristics of four advanced-age Chinese patients with adult-onset BVMD by combining multimodal imaging and genetic analysis. The four patients (all older than 50 years) were diagnosed with adult-onset BVMD at Zhongshan Ophthalmic Center (Guangzhou, China). Comprehensive ophthalmic examinations were performed, including analyses of best-corrected visual acuity, intraocular pressure, slit-lamp examination, fundus photography, optical coherence tomography, fundus fluorescein angiography and electrooculography. Genomic DNA was extracted from leukocytes isolated from peripheral blood obtained from these patients, their family members and 200 unrelated subjects from the same population. A total of 11 exons of the bestrophin-1 (BEST1) gene were amplified using PCR and sequenced. All of the four patients presented with lesions in the macular area. The patients were diagnosed with adult-onset BVMD based on multimodal imaging and genetic analysis. A total of four recurrent mutations, namely c.763C>T (p.Arg255Trp, p.R255W) in exon 7, c.584C>T (p.Ala195Val, p.A195V) in exon 5, c.910_912del GAT (p.304delAsp, p.D304del) in exon 8 and c.310G>C (p.Asp104His, p.D104H) in exon 4 of BEST1, were identified. Sorting intolerant from tolerant predicted that the amino acid substitutions p.R255W, p.A195V and p.D104H in the BEST1 protein were causing the damage. Combining multimodal imaging and genetic analysis was helpful in confirming the diagnosis of patients with adult-onset BVMD. These results maybe valuable for clinical and genetic counseling and for the development of therapeutic interventions for patients with BVMD.
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Affiliation(s)
- Ying Lin
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Tao Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Bingqian Liu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Cancan Lyu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China.,Department of Pharmacology, University of Iowa, Iowa City, IA 52242, USA
| | - Yu Lian
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Jizhu Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Ying Huang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Haichun Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Qingxiu Wu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Chenjin Jin
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Lin Lu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
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Singh Grewal S, Smith JJ, Carr AJF. Bestrophinopathies: perspectives on clinical disease, Bestrophin-1 function and developing therapies. Ther Adv Ophthalmol 2021; 13:2515841421997191. [PMID: 33738427 PMCID: PMC7934022 DOI: 10.1177/2515841421997191] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 01/27/2021] [Indexed: 12/17/2022] Open
Abstract
Bestrophinopathies are a group of clinically distinct inherited retinal dystrophies that typically affect the macular region, an area synonymous with central high acuity vision. This spectrum of disorders is caused by mutations in bestrophin1 (BEST1), a protein thought to act as a Ca2+-activated Cl- channel in the retinal pigment epithelium (RPE) of the eye. Although bestrophinopathies are rare, over 250 individual pathological mutations have been identified in the BEST1 gene, with many reported to have various clinical expressivity and incomplete penetrance. With no current clinical treatments available for patients with bestrophinopathies, understanding the role of BEST1 in cells and the pathological pathways underlying disease has become a priority. Induced pluripotent stem cell (iPSC) technology is helping to uncover disease mechanisms and develop treatments for RPE diseases, like bestrophinopathies. Here, we provide a comprehensive review of the pathophysiology of bestrophinopathies and highlight how patient-derived iPSC-RPE are being used to test new genomic therapies in vitro.
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Affiliation(s)
| | - Joseph J Smith
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Amanda-Jayne F Carr
- UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
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12
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Shah M, Broadgate S, Shanks M, Clouston P, Yu J, MacLaren RE, Németh AH, Halford S, Downes SM. Association of Clinical and Genetic Heterogeneity With BEST1 Sequence Variations. JAMA Ophthalmol 2021; 138:544-551. [PMID: 32239196 DOI: 10.1001/jamaophthalmol.2020.0666] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Importance Detailed phenotypic information on the spectrum of fundus abnormalities and clinical variability of all phenotypes associated with sequence variations in BEST1 is limited. Objective To report a detailed phenotypic and genetic analysis of a patient cohort with sequence variations in BEST1. Design, Setting, and Participants This retrospective case series took place at the Oxford Eye Hospital in Oxford, UK. Thirty-six patients from a single center with disease-causing sequence variations in BEST1 from 25 different families were analyzed. Data were collected from November 2017 to June 2018, and analysis began April 2018. Main Outcomes and Measures Results of ocular phenotyping and genetic testing using targeted next-generation sequencing to identify BEST1 sequence variations. Results Thirty-six patients from 25 families with disease-causing sequence variations in BEST1 were included. Of 36 patients, 20 (55.6%) were female. Three distinct clinical phenotypes were identified: autosomal recessive bestrophinopathy (ARB), best vitelliform macular dystrophy (BVMD), and adult-onset vitelliform macular dystrophy. The ARB phenotype group comprised 18 patients from 9 families with age in years at symptom onset ranging from less than 10 to 40s. All patients showed a common phenotype of fundus autofluorescence abnormalities, and spectral-domain optical coherence tomography features were similar in all patients with schitic and cystoid changes. A phenotype of a beaten metallic retinal appearance extending from the mid periphery to the far periphery was identified in 8 patients. Four patients from 1 family with ARB were previously reported to have autosomal recessive retinitis pigmentosa but were reclassified as having ARB as part of this study. The BVMD phenotype group comprised 16 patients from 14 families with age at symptom onset ranging from less than 10 to 70s. Fundus features were localized to the macula and consistent with the stage of BVMD. In the adult-onset vitelliform macular dystrophy phenotype group, the age in years at symptom onset varied from 50s to 70s in 2 patients from 2 families. Fundus features included small vitelliform lesions. Where available, electro-oculogram results demonstrated a reduced or absent light rise in all patients with ARB and BVMD. Genetic testing identified 22 variants in BEST1. Conclusions and Relevance These findings support the notion that ARB, BVMD, and adult-onset vitelliform macular dystrophy are clinically distinct and recognizable phenotypes and suggest that the association of autosomal recessive retinitis pigmentosa with sequence variations in BEST1 should be rereviewed.
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Affiliation(s)
- Mital Shah
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom.,Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Suzanne Broadgate
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Morag Shanks
- Oxford Medical Genetics Laboratories, Churchill Hospital, Oxford, United Kingdom
| | - Penny Clouston
- Oxford Medical Genetics Laboratories, Churchill Hospital, Oxford, United Kingdom
| | - Jing Yu
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Robert E MacLaren
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom.,Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Andrea H Németh
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Oxford Centre for Genomic Medicine, Oxford, United Kingdom
| | - Stephanie Halford
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Susan M Downes
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom.,Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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Fernandez-Abascal J, Graziano B, Encalada N, Bianchi L. Glial Chloride Channels in the Function of the Nervous System Across Species. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1349:195-223. [PMID: 35138616 DOI: 10.1007/978-981-16-4254-8_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
In the nervous system, the concentration of Cl- in neurons that express GABA receptors plays a key role in establishing whether these neurons are excitatory, mostly during early development, or inhibitory. Thus, much attention has been dedicated to understanding how neurons regulate their intracellular Cl- concentration. However, regulation of the extracellular Cl- concentration by other cells of the nervous system, including glia and microglia, is as important because it ultimately affects the Cl- equilibrium potential across the neuronal plasma membrane. Moreover, Cl- ions are transported in and out of the cell, via either passive or active transporter systems, as counter ions for K+ whose concentration in the extracellular environment of the nervous system is tightly regulated because it directly affects neuronal excitability. In this book chapter, we report on the Cl- channel types expressed in the various types of glial cells focusing on the role they play in the function of the nervous system in health and disease. Furthermore, we describe the types of stimuli that these channels are activated by, the other solutes that they may transport, and the involvement of these channels in processes such as pH regulation and Regulatory Volume Decrease (RVD). The picture that emerges is one of the glial cells expressing a variety of Cl- channels, encoded by members of different gene families, involved both in short- and long-term regulation of the nervous system function. Finally, we report data on invertebrate model organisms, such as C. elegans and Drosophila, that are revealing important and previously unsuspected functions of some of these channels in the context of living and behaving animals.
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Affiliation(s)
- Jesus Fernandez-Abascal
- Department Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Bianca Graziano
- Department Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Nicole Encalada
- Department Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Laura Bianchi
- Department Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, FL, USA.
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NOVEL BEST1 MUTATIONS DETECTED BY NEXT-GENERATION SEQUENCING IN A CHINESE POPULATION WITH VITELLIFORM MACULAR DYSTROPHY. Retina 2020; 39:1613-1622. [PMID: 29781975 DOI: 10.1097/iae.0000000000002183] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
PURPOSE To characterize novel BEST1 mutations and the phenotype-genotype correlations in vitelliform macular dystrophy in a Chinese population. METHODS Seventeen individuals affected by vitelliform macular dystrophy underwent detailed ophthalmic examinations, including a best-corrected visual acuity test, slit-lamp biomicroscopy, fundus photography, spectral-domain optical coherence tomography, fundus autofluorescence, fluorescein angiography, and optical coherence tomography angiography. Next-generation sequencing was used to screen 790 genes frequently involved in common inherited nonsyndromic eye diseases in all participants. Sanger sequencing was used to identify possible disease-causing variants. RESULTS The mean ± SD age of the patients was 44.20 ± 15.09 (range: 16-69) years. Seven novel BEST1 mutations were identified: six heterozygous missense (p.Thr307Asn, p.Ile295The, p.Leu75Pro, p.Thr2Ser, p.Ser79Tyr, and p.Val81Leu) and one frameshift (p.Glu115GlufsX120) mutation. Choroidal neovascularization was detected in two probands. One individual presented with subfoveal focal choroidal excavation. Arden ratios obtained by electrooculography were less than the 1.5 cutoff value in 7 patients. No mutations were identified in 2 patients, one of whom had a fundus appearance typical of vitelliform macular dystrophy and a decreased Arden ratio (1.2/1.2). CONCLUSION Patients with the same heterozygous BEST1 mutations exhibited varying phenotypes. Our results have expanded the BEST1 mutation spectrum in a Chinese population with vitelliform macular dystrophy.
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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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16
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Xuan Y, Zhang Y, Zong Y, Wang M, Li L, Ye X, Liu W, Chen J, Sun X, Zhang Y, Chen Y. The Clinical Features and Genetic Spectrum of a Large Cohort of Chinese Patients With Vitelliform Macular Dystrophies. Am J Ophthalmol 2020; 216:69-79. [PMID: 32278767 DOI: 10.1016/j.ajo.2020.03.047] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 03/18/2020] [Accepted: 03/31/2020] [Indexed: 11/18/2022]
Abstract
PURPOSE To provide the clinical and genetic characteristics of a large cohort of Chinese patients with vitelliform macular dystrophies. DESIGN Cross-sectional study. METHODS One hundred and thirty-four unrelated Chinese patients diagnosed with Best vitelliform macular dystrophy (BVMD), autosomal recessive bestrophinopathy (ARB), or adult vitelliform macular dystrophy (AVMD) were enrolled. Detailed ophthalmic examinations and genetic testing on vitelliform macular dystrophy-related genes were performed. Genotype and phenotype association were analyzed among different diagnostic groups. RESULTS In total, 87 BVMD, 30 AVMD, and 17 ARB patients were enrolled in this study. Genetic analysis identified 37 BEST1 mutations in 53 patients with BVMD and ARB. Of these, 5 variants (c.254A>C, c.291C>G, c.722C>G, c.848_850del, c.1740-2A>C) were novel. The variant c.898G>A was a hotspot mutation, which was identified in 13 patients with BVMD and 1 patient with ARB. There were significant differences of ocular biometric parameters among patients with homozygous or compound heterozygous mutations, heterozygous mutations, and those without mutations of BEST1. Homozygous or compound heterozygous patients had shortest axial length (AL), shallowest anterior chamber depth (ACD), and highest intraocular pressure (IOP); patients without mutations had longest AL, deepest ACD, and lowest IOP; and heterozygous patients were in between. Moreover, 7 patients harboring heterozygous mutations in BEST1 and 3 patients without BEST1 mutations showed similar clinical appearance to ARB in our cohort. CONCLUSIONS This is the largest sample size study of Chinese vitelliform macular dystrophy patients. Our results indicated that assessment of angle-closure risk is a necessary consideration for all types of BEST1-related vitelliform macular dystrophies. The study expanded both the clinical and genetic findings of 3 common types of vitelliform macular dystrophies in a Chinese population.
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Affiliation(s)
- Yi Xuan
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
| | - Youjia Zhang
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
| | - Yuan Zong
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China; NHC Key Laboratory of Myopia, Fudan University, Chinese Academy of Medical Sciences, Shanghai, China
| | - Min Wang
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
| | - Lei Li
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
| | - Xiaofeng Ye
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
| | - Wei Liu
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
| | - Junyi Chen
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China; NHC Key Laboratory of Myopia, Fudan University, Chinese Academy of Medical Sciences, Shanghai, China
| | - Xinghuai Sun
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China; State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Fudan University, Shanghai, China; NHC Key Laboratory of Myopia, Fudan University, Chinese Academy of Medical Sciences, Shanghai, China
| | - Yongjin Zhang
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
| | - Yuhong Chen
- Department of Ophthalmology & Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China; NHC Key Laboratory of Myopia, Fudan University, Chinese Academy of Medical Sciences, Shanghai, China.
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Milenkovic A, Milenkovic VM, Wetzel CH, Weber BHF. BEST1 protein stability and degradation pathways differ between autosomal dominant Best disease and autosomal recessive bestrophinopathy accounting for the distinct retinal phenotypes. Hum Mol Genet 2019; 27:1630-1641. [PMID: 29668979 PMCID: PMC5905664 DOI: 10.1093/hmg/ddy070] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 02/19/2018] [Indexed: 12/21/2022] Open
Abstract
Mutations in bestrophin-1 (BEST1) are associated with distinct retinopathies, notably three forms with autosomal dominant inheritance and one condition with an autosomal recessive mode of transmission. The molecular mechanisms underlying their distinct retinal phenotypes are mostly unknown. Although heterozygous missense mutations in BEST1 reveal dominant-negative effects in patients with autosomal dominant Best disease (BD), heterozygous mutations associated with autosomal recessive bestrophinopathy (ARB) display no disease phenotype. Here we show that the recessive mutations trigger a strong and fast protein degradation process in the endoplasmic reticulum (ER), thereby favoring a decreased stoichiometry of mutant versus normal BEST1 subunits in the assembly of the homo-pentameric BEST1 chloride channel. In contrast, dominant mutations escape ER-associated degradation and are subjected to a slightly delayed post-ER degradation via the endo-lysosomal degradation pathway. As a result, increased formation of a non-functional BEST1 channel occurs due to a roughly equimolar incorporation of normal and mutant BEST1 subunits into the channel complex. Taken together, our data provide insight into the molecular pathways of dominantly and recessively acting BEST1 missense mutations suggesting that the site of subcellular protein quality control as well as the rate and degree of mutant protein degradation are ultimately responsible for the distinct retinal disease phenotypes in BD and ARB.
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Affiliation(s)
- Andrea Milenkovic
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
| | - Vladimir M Milenkovic
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, 93053 Regensburg, Germany
| | - Christian H Wetzel
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, 93053 Regensburg, Germany
| | - Bernhard H F Weber
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
- To whom correspondence should be addressed at: Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauß-Allee 11, D-93053 Regensburg, Germany. Tel: +49 9419445400; Fax: +49 9419445402;
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18
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Next generation sequencing identifies novel disease-associated BEST1 mutations in Bestrophinopathy patients. Sci Rep 2018; 8:10176. [PMID: 29976937 PMCID: PMC6033935 DOI: 10.1038/s41598-018-27951-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 06/13/2018] [Indexed: 12/30/2022] Open
Abstract
Bestinopathies are a spectrum of retinal disorders associated with mutations in BEST1 including autosomal recessive bestrophinopathy (ARB) and autosomal dominant Best vitelliform macular dystrophy (BVMD). We applied whole-exome sequencing on four unrelated Indian families comprising eight affected and twelve unaffected individuals. We identified five mutations in BEST1, including p.Tyr131Cys in family A, p.Arg150Pro in family B, p.Arg47His and p.Val216Ile in family C and p.Thr91Ile in family D. Among these, p.Tyr131Cys, p.Arg150Pro and p.Val216Ile have not been previously reported. Further, the inheritance pattern of BEST1 mutations in the families confirmed the diagnosis of ARB in probands in families A, B and C, while the inheritance of heterozygous BEST1 mutation in family D (p.Thr91Ile) was suggestive of BVMD. Interestingly, the ARB families A and B carry homozygous mutations while family C was a compound heterozygote with a mutation in an alternate BEST1 transcript isoform, highlighting a role for alternate BEST1 transcripts in bestrophinopathy. In the BVMD family D, the heterozygous BEST1 mutation found in the proband was also found in the asymptomatic parent, suggesting an incomplete penetrance and/or the presence of additional genetic modifiers. Our report expands the list of pathogenic BEST1 genotypes and the associated clinical diagnosis.
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20
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Effects of Ca 2+ ions on bestrophin-1 surface films. Colloids Surf B Biointerfaces 2016; 149:226-232. [PMID: 27768912 DOI: 10.1016/j.colsurfb.2016.10.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 10/07/2016] [Accepted: 10/12/2016] [Indexed: 01/01/2023]
Abstract
Human bestrophin-1 (hBest1) is a transmembrane calcium-activated chloride channel protein - member of the bestrophin family of anion channels, predominantly expressed in the membrane of retinal pigment epithelium (RPE) cells. Mutations in the protein cause ocular diseases, named Bestrophinopathies. Here, we present the first Fourier transform infrared (FTIR) study of the secondary structure elements of hBest1, π/A isotherms and hysteresis, Brewster angle microscopy (BAM) and atomic force microscopy (AFM) visualization of the aggregation state of protein molecules dispersed as Langmuir and Langmuir-Blodgett films. The secondary structure of hBest1 consists predominantly of 310-helices (27.2%), α-helixes (16.3%), β-turns and loops (32.2%). AFM images of hBest1 suggest approximate lateral dimensions of 100×160Å and 75Å height. Binding of calcium ions (Ca2+) induces conformational changes in the protein secondary structure leading to assembly of protein molecules and changes in molecular and macro-organization of hBest1 in monolayers. These data provide basic information needed in pursuit of molecular mechanisms underlying retinal and other pathologies linked to this protein.
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Wu L, Sun Y, Ma L, Zhu J, Zhang B, Pan Q, Li Y, Liu H, Diao A, Li Y. A C-terminally truncated mouse Best3 splice variant targets and alters the ion balance in lysosome-endosome hybrids and the endoplasmic reticulum. Sci Rep 2016; 6:27332. [PMID: 27265833 PMCID: PMC4893618 DOI: 10.1038/srep27332] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 05/16/2016] [Indexed: 02/07/2023] Open
Abstract
The Bestrophin family has been characterized as Cl(-) channels in mammals and Na(+) channels in bacteria, but their exact physiological roles remian unknown. In this study, a natural C-terminally truncated variant of mouse Bestrophin 3 (Best3V2) expression in myoblasts and muscles is demonstrated. Unlike full-length Best3, Best3V2 targets the two important intracellular Ca stores: the lysosome and the ER. Heterologous overexpression leads to lysosome swelling and renders it less acidic. Best3V2 overexpression also results in compromised Ca(2+) release from the ER. Knocking down endogenous Best3 expression in myoblasts makes these cells more excitable in response to Ca(2+) mobilizing reagents, such as caffeine. We propose that Best3V2 in myoblasts may work as a tuner to control Ca(2+) release from intracellular Ca(2+) stores.
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Affiliation(s)
- Lichang Wu
- Department of Animal Sciences and Technology, Qingdao Agricultural University, Qingdao, China.,College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Yu Sun
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Liqiao Ma
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Jun Zhu
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Baoxia Zhang
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Qingjie Pan
- Department of Animal Sciences and Technology, Qingdao Agricultural University, Qingdao, China
| | - Yuyin Li
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Huanqi Liu
- Department of Animal Sciences and Technology, Qingdao Agricultural University, Qingdao, China
| | - Aipo Diao
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Yinchuan Li
- Department of Animal Sciences and Technology, Qingdao Agricultural University, Qingdao, China
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Chen CJ, Kaufman S, Packo K, Stöhr H, Weber BHF, Goldberg MF. Long-Term Macular Changes in the First Proband of Autosomal Dominant Vitreoretinochoroidopathy (ADVIRC) Due to a Newly Identified Mutation in BEST1. Ophthalmic Genet 2016; 37:102-8. [PMID: 26849243 DOI: 10.3109/13816810.2015.1039893] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Mutations in BEST1 account for autosomal dominant vitreoretinochoroidopathy (ADVIRC), a rare inherited retinal dystrophy with presenile cataracts and incomplete anterior segment development. The long-term clinical findings and visual prognosis of these patients continues to evolve over time. MATERIALS AND METHODS The retina was assessed by fundus photography, fluorescein angiography, and spectral domain optical coherence tomography. Sanger dideoxy chain-termination sequencing identified mutations in BEST1. Bioinformatic tools were used to predict changes in splicing. An in vitro splicing assay was applied to evaluate for altered pre-mRNA splicing. RESULTS Long-term follow up of the first ever reported ADVIRC proband revealed progressive foveal atrophy in both eyes 3 decades after his initial presentation. Progressive retinal ischemia, bilateral iris atrophy, and pseudophakodnesis were observed on follow up. The patient was heterozygous for a c.248G > A missense mutation in exon 4 of BEST1, affecting a highly conserved transmembrane domain. Although computational prediction models suggest a change in the binding probability of splicing-associated SR proteins, in vitro splicing assays failed to demonstrate an effect of the c.248G > A mutation on splicing of BEST1 exon 3 or exon 4. CONCLUSIONS Progressive posterior chorioretinal changes occurred over time in the initial ADVIRC proband, leading to visual loss. The causative mutation in this patient falls in the transmembrane domain of the BEST1 protein, with unclear functional consequences. Although previous studies showed alteration in pre-mRNA splicing, in vitro splicing assays failed to demonstrate this in our patient.
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Affiliation(s)
- Connie J Chen
- a Wilmer Eye Institute, Johns Hopkins Hospital , Baltimore , MD , USA
| | | | - Kirk Packo
- c Department of Ophthalmology , Rush University Medical Center , Chicago , IL , USA , and
| | - Heidi Stöhr
- d Institute of Human Genetics, University of Regensburg , Regensburg , Germany
| | - Bernhard H F Weber
- d Institute of Human Genetics, University of Regensburg , Regensburg , Germany
| | - Morton F Goldberg
- a Wilmer Eye Institute, Johns Hopkins Hospital , Baltimore , MD , USA
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23
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Johnson AA, Bachman LA, Gilles BJ, Cross SD, Stelzig KE, Resch ZT, Marmorstein LY, Pulido JS, Marmorstein AD. Autosomal Recessive Bestrophinopathy Is Not Associated With the Loss of Bestrophin-1 Anion Channel Function in a Patient With a Novel BEST1 Mutation. Invest Ophthalmol Vis Sci 2015. [PMID: 26200502 DOI: 10.1167/iovs.15-16910] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
PURPOSE Mutations in BEST1, encoding bestrophin-1 (Best1), cause autosomal recessive bestrophinopathy (ARB). Encoding bestrophin-1 is a pentameric anion channel localized to the basolateral plasma membrane of the RPE. Here, we characterize the effects of the mutations R141H (CGC > CAC) and I366fsX18 (c.1098_1100+7del), identified in a patient in our practice, on Best1 trafficking, oligomerization, and channel activity. METHODS Currents of Cl- were assessed in transfected HEK293 cells using whole-cell patch clamp. Best1 localization was assessed by confocal microscopy in differentiated, human-induced pluripotent stem cell-derived RPE (iPSC-RPE) cells following expression of mutants via adenovirus-mediated gene transfer. Oligomerization was evaluated by coimmunoprecipitation in iPSC-RPE and MDCK cells. RESULTS Compared to Best1, Best1 I366fsX18 currents were increased while Best1 R141H Cl- currents were diminished. Coexpression of Best1 R141H with Best1 or Best1 I366fsX18 resulted in rescued channel activity. Overexpressed Best1, Best1 R141H, and Best1 I366fsX18 were all properly localized in iPSC-RPE cells; Best1 R141H and Best1 I366fsX18 coimmunoprecipitated with endogenous Best1 in iPSC-RPE cells and with each other in MDCK cells. CONCLUSIONS The first 366 amino acids of Best1 are sufficient to mediate channel activity and homo-oligomerization. The combination of Best1 and Best1 R141H does not cause disease, while Best1 R141H together with Best1 I366fsX18 causes ARB. Since both combinations generate comparable Cl- currents, this indicates that ARB in this patient is not caused by a loss of channel activity. Moreover, Best1 I366fsX18 differs from Best1 in that it lacks most of the cytosolic C-terminal domain, suggesting that the loss of this region contributes significantly to the pathogenesis of ARB in this patient.
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Affiliation(s)
- Adiv A Johnson
- Department of Ophthalmology Mayo Clinic, Rochester, Minnesota, United States
| | - Lori A Bachman
- Department of Ophthalmology Mayo Clinic, Rochester, Minnesota, United States
| | - Benjamin J Gilles
- Department of Ophthalmology Mayo Clinic, Rochester, Minnesota, United States
| | - Samuel D Cross
- Department of Ophthalmology Mayo Clinic, Rochester, Minnesota, United States
| | - Kimberly E Stelzig
- Center for Regenerative Medicine, Mayo Clinic, Rochester, Minnesota, United States
| | - Zachary T Resch
- Center for Regenerative Medicine, Mayo Clinic, Rochester, Minnesota, United States
| | - Lihua Y Marmorstein
- Department of Ophthalmology Mayo Clinic, Rochester, Minnesota, United States
| | - Jose S Pulido
- Department of Ophthalmology Mayo Clinic, Rochester, Minnesota, United States 3Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States
| | - Alan D Marmorstein
- Department of Ophthalmology Mayo Clinic, Rochester, Minnesota, United States
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Leblanc N, Forrest AS, Ayon RJ, Wiwchar M, Angermann JE, Pritchard HAT, Singer CA, Valencik ML, Britton F, Greenwood IA. Molecular and functional significance of Ca(2+)-activated Cl(-) channels in pulmonary arterial smooth muscle. Pulm Circ 2015; 5:244-68. [PMID: 26064450 DOI: 10.1086/680189] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 07/22/2014] [Indexed: 12/31/2022] Open
Abstract
Increased peripheral resistance of small distal pulmonary arteries is a hallmark signature of pulmonary hypertension (PH) and is believed to be the consequence of enhanced vasoconstriction to agonists, thickening of the arterial wall due to remodeling, and increased thrombosis. The elevation in arterial tone in PH is attributable, at least in part, to smooth muscle cells of PH patients being more depolarized and displaying higher intracellular Ca(2+) levels than cells from normal subjects. It is now clear that downregulation of voltage-dependent K(+) channels (e.g., Kv1.5) and increased expression and activity of voltage-dependent (Cav1.2) and voltage-independent (e.g., canonical and vanilloid transient receptor potential [TRPC and TRPV]) Ca(2+) channels play an important role in the functional remodeling of pulmonary arteries in PH. This review focuses on an anion-permeable channel that is now considered a novel excitatory mechanism in the systemic and pulmonary circulations. It is permeable to Cl(-) and is activated by a rise in intracellular Ca(2+) concentration (Ca(2+)-activated Cl(-) channel, or CaCC). The first section outlines the biophysical and pharmacological properties of the channel and ends with a description of the molecular candidate genes postulated to encode for CaCCs, with particular emphasis on the bestrophin and the newly discovered TMEM16 and anoctamin families of genes. The second section provides a review of the various sources of Ca(2+) activating CaCCs, which include stimulation by mobilization from intracellular Ca(2+) stores and Ca(2+) entry through voltage-dependent and voltage-independent Ca(2+) channels. The third and final section summarizes recent findings that suggest a potentially important role for CaCCs and the gene TMEM16A in PH.
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Affiliation(s)
- Normand Leblanc
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Abigail S Forrest
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Ramon J Ayon
- Department of Medicine, University of Illinois, Chicago, Illinois, USA
| | - Michael Wiwchar
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Jeff E Angermann
- School of Community Health Sciences, University of Nevada, Reno, Nevada, USA
| | - Harry A T Pritchard
- Vascular Biology Research Centre, Institute of Cardiovascular and Cell Sciences, St. George's University of London, London, United Kingdom
| | - Cherie A Singer
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Maria L Valencik
- Department of Biochemistry and Molecular Biology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Fiona Britton
- Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Iain A Greenwood
- Vascular Biology Research Centre, Institute of Cardiovascular and Cell Sciences, St. George's University of London, London, United Kingdom
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25
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Mladenova K, Petrova S, Moskova-Doumanova V, Topouzova-Hristova T, Stoitsova S, Tabashka I, Chakarova C, Lalchev Z, Doumanov J. Transepithelial resistance in human bestrophin-1 stably transfected Madin-Darby canine kidney cells. BIOTECHNOL BIOTEC EQ 2015; 29:101-104. [PMID: 26019622 PMCID: PMC4434050 DOI: 10.1080/13102818.2014.988078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 10/10/2014] [Indexed: 11/04/2022] Open
Abstract
Bestrophin-1 (Best1) is a transmembrane protein, found in the basolateral plasma membrane of retinal pigmented epithelial cells. The exact structure and functions of Best1 protein are still unclear. The protein is thought to be a regulator of ion channels, or an ion channel itself: it was shown to be permeable for chloride, thiocyanate, bicarbonate, glutamate and γ-aminobutyric acid (GABA). Mutations in the gene for Best1 are leading to best vitelliform macular dystrophy (BVMD) and are found in several other types of maculopathy. In order to obtain additional information about Best1 protein, we determined cell polarization of a stably transfected Madin–Darby canine kidney cell line II (MDCK II) cell line, expressing human Best1. We measured the transepithelial resistance of transfected and non-transfected MDCK cells by voltmeter EVOM, over 10 days at 24 hour intervals. The first few days (first–fourth day) both cell lines showed the same or similar values of transmembrane resistance. As expected, on the fifth day the non-transfected cells showed maximum value of epithelial resistance, corresponding to the forming of monolayer. The transfected cells showed maximum value of transepithelial resistance on the ninth day of their cultivation. Phalloidin staining of actin demonstrated the difference in actin arrangements between transfected and non-transfected cells due to Best1. As a consequence of actin rearrangement, Best1 strongly affects the transepithelial resistance of polarizing stably transfected MDCK cells. Our results suggest that Best1 protein has an effect on transepithelial resistance and actin rearrangements of polarized stably transfected MDCK cells.
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Affiliation(s)
- Kirilka Mladenova
- Faculty of Biology, Sofia University "St. Kliment Ohridski" , Sofia , Bulgaria
| | - Svetla Petrova
- Faculty of Biology, Sofia University "St. Kliment Ohridski" , Sofia , Bulgaria
| | | | | | - Stoyanka Stoitsova
- Institute of Microbiology, Bulgarian Academy of Science , Sofia , Bulgaria
| | - Irena Tabashka
- Faculty of Biology, Sofia University "St. Kliment Ohridski" , Sofia , Bulgaria
| | | | - Zdravko Lalchev
- Faculty of Biology, Sofia University "St. Kliment Ohridski" , Sofia , Bulgaria
| | - Jordan Doumanov
- Faculty of Biology, Sofia University "St. Kliment Ohridski" , Sofia , Bulgaria
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26
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Interaction of Bestrophin-1 with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in surface films. Colloids Surf B Biointerfaces 2014; 122:432-438. [PMID: 25156781 DOI: 10.1016/j.colsurfb.2014.01.045] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 01/14/2014] [Accepted: 01/27/2014] [Indexed: 11/21/2022]
Abstract
Human bestrophin-1 (hBest1) is a transmembrane channel protein, predominantly expressed in the membrane of retinal pigment epithelium (RPE) cells. Although it is clear that hBest1's interactions with lipids are crucial for its function such studies were not performed as the protein was not purified. Here we describe an effective purification of hBest1 from Madin-Darby Canine Kidney (MDCK) cells via simple gel-filtration and affinity chromatographic steps, which makes possible to probe the protein interplay with lipids. The interaction of the purified hBest1 with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) was studied in Langmuir monolayers. The surface pressure (π)-area (A) isotherms and compression/expansion isocycles of POPC monolayer were recorded in absence and presence of hBest1 in the subphase. The π(A) isotherms were analyzed in terms of surface compressional modulus and via two-dimensional virial equation of state. The dilatational rheological properties of the surface films and their surface potential were also measured. The morphology of the films was observed by Brewster angle microscopy. The inclusion of the protein in the film subphase does not lead to in-depth penetration of hBest1 but interaction takes place in the headgroup region of the monolayer. The hBest1/POPC interaction resulted in formation of more condensed films, which rheological properties and lateral structure differed significantly from the pure POPC monolayers. Our study sheds light on the still unclear question how hBest1 gets in touch with biomembrane phospholipids of eukaryotic cells that might be of key importance for the proper structure and function of RPE biomembranes.
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27
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Yang T, Liu Q, Kloss B, Bruni R, Kalathur RC, Guo Y, Kloppmann E, Rost B, Colecraft HM, Hendrickson WA. Structure and selectivity in bestrophin ion channels. Science 2014; 346:355-9. [PMID: 25324390 DOI: 10.1126/science.1259723] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Human bestrophin-1 (hBest1) is a calcium-activated chloride channel from the retinal pigment epithelium, where mutations are associated with vitelliform macular degeneration, or Best disease. We describe the structure of a bacterial homolog (KpBest) of hBest1 and functional characterizations of both channels. KpBest is a pentamer that forms a five-helix transmembrane pore, closed by three rings of conserved hydrophobic residues, and has a cytoplasmic cavern with a restricted exit. From electrophysiological analysis of structure-inspired mutations in KpBest and hBest1, we find a sensitive control of ion selectivity in the bestrophins, including reversal of anion/cation selectivity, and dramatic activation by mutations at the cytoplasmic exit. A homology model of hBest1 shows the locations of disease-causing mutations and suggests possible roles in regulation.
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Affiliation(s)
- Tingting Yang
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Qun Liu
- New York Structural Biology Center, Synchrotron Beamlines, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Brian Kloss
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA
| | - Renato Bruni
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA
| | - Ravi C Kalathur
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA
| | - Youzhong Guo
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Edda Kloppmann
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA. Department of Informatics, Bioinformatics and Computational Biology, TUM (Technische Universität München), Garching 85748, Germany
| | - Burkhard Rost
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA. Department of Informatics, Bioinformatics and Computational Biology, TUM (Technische Universität München), Garching 85748, Germany
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Wayne A Hendrickson
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA. New York Structural Biology Center, Synchrotron Beamlines, Brookhaven National Laboratory, Upton, NY 11973, USA. New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA. Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA.
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28
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Lee YS, Marmorstein LY, Marmorstein AD. Soluble adenylyl cyclase in the eye. Biochim Biophys Acta Mol Basis Dis 2014; 1842:2579-83. [PMID: 25108282 DOI: 10.1016/j.bbadis.2014.07.032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 07/26/2014] [Accepted: 07/30/2014] [Indexed: 11/26/2022]
Abstract
Adenylyl cyclases (ACs) are a family of enzymes which convert ATP to cAMP, an essential intermediate in many signal transduction pathways. Of the 10 AC genes in man, 9 fall into the category of transmembrane ACs (tmACs), which associate with G-protein coupled receptors (GPCRs) and are activated by forskolin. The 10th AC, termed soluble AC (sAC) is neither activated by forskolin nor does it interact with GPCRs. Rather, sAC can be found in many compartments within the cell and is activated by bicarbonate. As such, sAC is considered a major sensor of bicarbonate in many tissues. The pathways involving sAC vary in different tissues and organ systems, and are as diverse as facilitating sperm capacitation and regulating pressure in the eye. The role of sAC in the eye has only recently begun to receive significant attention. Here we summarize what is known about the roles of sAC in the eye. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.
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Affiliation(s)
- Yong S Lee
- Department of Ophthalmology, Mayo Clinic, Rochester, MN 55902, USA
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29
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Effects of alternative splicing on the function of bestrophin-1 calcium-activated chloride channels. Biochem J 2014; 458:575-83. [PMID: 24341532 DOI: 10.1042/bj20121546] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The proposed Ca2+-activated Cl- channel protein Best1 (bestrophin 1) is expressed and functionally important in the retina and in the brain. Human BEST1 has two known splice variants, Best1V1 and Best1V2, which arise from alternative splicing of two exons: exon 2 splicing results in a unique N-terminal domain, whereas alternative splicing of exon 11 produces two mutually exclusive C-termini. Prior studies were limited to Best1V1 and its clinically relevant mutations. In the present work, we cloned a novel splice variant of Best1V1 missing exon 2 (Best1V1Δex2) and differing from each of the two previously identified isoforms by one alternatively spliced domain. This finding allowed us to determine the role for alternative splicing of the Best1 N- and C-termini. We heteroexpressed Best1V1Δex2 in HEK (human embryonic kidney)-293 cells, and compared its properties with Best1V1 and Best1V2. Western blot analysis confirmed protein expression from all three splice variants. Both Best1V1 and Best1V1Δex2 successfully formed Ca2+-activated Cl- channels, demonstrating that the N-terminus encoded by exon 2 is not essential for channel function. In contrast, Best1V2-expressing cells had no detectable Ca2+-activated Cl- currents, pointing to a critical role for splicing of the C-terminus. Surface protein biotinylation demonstrated that Best1V1 and Best1V1Δex2 are trafficked to the plasma membrane, whereas Best1V2 is not. These results define the impact of alternative splicing on Best1 function, and should be taken into consideration in future modelling of the Best1 protein structure.
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30
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Abstract
Human Bestrophin 1 (hBest1) is a calcium-activated chloride channel that regulates neuronal excitability, synaptic activity, and retinal homeostasis. Mutations in hBest1 cause the autosomal-dominant Best macular dystrophy (BMD). Because hBest1 mutations cause BMD, but a knockout does not, we wondered if hBest1 mutants exert a dominant negative effect through interaction with other calcium-activated chloride channels, such as hBest2, 3, or 4, or transmembrane member 16A (TMEM16A), a member of another channel family. The subunit architecture of Best channels is debated, and their ability to form heteromeric channel assemblies is unclear. Using single-molecule subunit analysis, we find that each of hBest1, 2, 3, and 4 forms a homotetrameric channel. Despite considerable conservation among hBests, hBest1 has little or no interaction with other hBests or mTMEM16A. We identify the domain responsible for assembly specificity. This domain also plays a role in channel function. Our results indicate that Best channels preferentially self-assemble into homotetramers.
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31
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Moskova-Doumanova V, Pankov R, Lalchev Z, Doumanov J. Best1 Shot Through the Eye—Structure, Functions and Clinical Implications of Bestrophin-1 Protein. BIOTECHNOL BIOTEC EQ 2014. [DOI: 10.5504/bbeq.2012.0124] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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32
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Johnson AA, Lee YS, Chadburn AJ, Tammaro P, Manson FD, Marmorstein LY, Marmorstein AD. Disease-causing mutations associated with four bestrophinopathies exhibit disparate effects on the localization, but not the oligomerization, of Bestrophin-1. Exp Eye Res 2014; 121:74-85. [PMID: 24560797 PMCID: PMC4123461 DOI: 10.1016/j.exer.2014.02.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 01/31/2014] [Accepted: 02/07/2014] [Indexed: 01/11/2023]
Abstract
BEST1 encodes Bestrophin-1 (Best1), a homo-oligomeric, integral membrane protein localized to the basolateral plasma membrane of the retinal pigment epithelium. Mutations in BEST1 cause five distinct retinal degenerative diseases, including adult vitelliform macular dystrophy (AVMD), autosomal recessive bestrophinopathy (ARB), autosomal dominant vitreoretinochoroidopathy (ADVIRC), and retinitis pigmentosa (RP). The mechanisms underlying these diseases and why mutations cause one disease over another are, for the most part, unknown. To gain insights into these four diseases, we expressed 28 Best1 mutants fused to YFP in polarized MDCK monolayers and, via confocal microscopy and immunofluorescence, live-cell FRET, and reciprocal co-immunoprecipitation experiments, screened these mutants for defects in localization and oligomerization. All 28 mutants exhibited comparable FRET efficiencies to and co-immunoprecipitated with WT Best1, indicating unimpaired oligomerization. RP- and ADVIRC-associated mutants were properly localized to the basolateral plasma membrane of cells, while two AVMD and most ARB mutants were mislocalized. When co-expressed, all mislocalized mutants caused mislocalization of WT Best1 to intracellular compartments. Our current and past results indicate that mislocalization of Best1 is not an absolute feature of any individual bestrophinopathy, occurring in AVMD, BVMD, and ARB. Furthermore, some ARB mutants that do not also cause dominant disease cause mislocalization of Best1, indicating that mislocalization is not a cause of disease, and that absence of Best1 activity from the plasma membrane is tolerated. Lastly, we find that the ARB truncation mutants L174Qfs*57 and R200X can form oligomers with WT Best1, indicating that the first ∼174 amino acids of Best1 are sufficient for oligomerization to occur.
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Affiliation(s)
- Adiv A Johnson
- Physiological Sciences Graduate Interdisciplinary Program, University of Arizona, Tucson, AZ 85724, USA; Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905, USA.
| | - Yong-Suk Lee
- Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905, USA.
| | - Andrew J Chadburn
- Faculty of Life Sciences, Faculty of Medical and Human Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom.
| | - Paolo Tammaro
- Faculty of Life Sciences, Faculty of Medical and Human Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom.
| | - Forbes D Manson
- Manchester Centre for Genomic Medicine, Faculty of Medical and Human Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom.
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Strauß O, Müller C, Reichhart N, Tamm ER, Gomez NM. The Role of Bestrophin-1 in Intracellular Ca2+ Signaling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 801:113-9. [DOI: 10.1007/978-1-4614-3209-8_15] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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34
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Pasquay C, Wang LF, Lorenz B, Preising MN. Bestrophin 1 – Phenotypes and Functional Aspects in Bestrophinopathies. Ophthalmic Genet 2013; 36:193-212. [DOI: 10.3109/13816810.2013.863945] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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35
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Doumanov JA, Zeitz C, Gimenez PD, Audo I, Krishna A, Alfano G, Diaz MLB, Moskova-Doumanova V, Lancelot ME, Sahel JA, Nandrot EF, Bhattacharya SS. Disease-causing mutations in BEST1 gene are associated with altered sorting of bestrophin-1 protein. Int J Mol Sci 2013; 14:15121-40. [PMID: 23880862 PMCID: PMC3742291 DOI: 10.3390/ijms140715121] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 07/02/2013] [Accepted: 07/04/2013] [Indexed: 01/03/2023] Open
Abstract
Mutations in BEST1 gene, encoding the bestrophin-1 (Best1) protein are associated with macular dystrophies. Best1 is predominantly expressed in the retinal pigment epithelium (RPE), and is inserted in its basolateral membrane. We investigated the cellular localization in polarized MDCKII cells of disease-associated Best1 mutant proteins to study specific sorting motifs of Best1. Real-time PCR and western blots for endogenous expression of BEST1 in MDCK cells were performed. Best1 mutant constructs were generated using site-directed mutagenesis and transfected in MDCK cells. For protein sorting, confocal microscopy studies, biotinylation assays and statistical methods for quantification of mislocalization were used. Analysis of endogenous expression of BEST1 in MDCK cells revealed the presence of BEST1 transcript but no protein. Confocal microscopy and quantitative analyses indicate that transfected normal human Best1 displays a basolateral localization in MDCK cells, while cell sorting of several Best1 mutants (Y85H, Q96R, L100R, Y227N, Y227E) was altered. In contrast to constitutively active Y227E, constitutively inactive Y227F Best1 mutant localized basolaterally similar to the normal Best1 protein. Our data suggest that at least three basolateral sorting motifs might be implicated in proper Best1 basolateral localization. In addition, non-phosphorylated tyrosine 227 could play a role for basolateral delivery.
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Affiliation(s)
- Jordan A. Doumanov
- Biological Faculty, Sofia University “Saint Kliment Ohridski”, 8 Dragan Tzankov str, Sofia 1164, Bulgaria; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +359-2-8167-204; Fax: +359-2-8656-641
| | - Christina Zeitz
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
| | - Paloma Dominguez Gimenez
- Andalusian Center of Molecular Biology and Regenerative Medicine, Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Avda. Americo Vespucio s/n, Parque Cientifico y Tecnologico, Isla de la Cartuja 41092, Sevilla, Spain; E-Mails: (P.D.G.); (A.K.); (M.L.B.D.)
| | - Isabelle Audo
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
- Centre de Référence Maladies Rares/Centre d’Investigation Clinique (CMR/CIC), 503 INSERM, CHNO des Quinze-Vingts, Paris F-75012, France
| | - Abhay Krishna
- Andalusian Center of Molecular Biology and Regenerative Medicine, Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Avda. Americo Vespucio s/n, Parque Cientifico y Tecnologico, Isla de la Cartuja 41092, Sevilla, Spain; E-Mails: (P.D.G.); (A.K.); (M.L.B.D.)
| | - Giovanna Alfano
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Maria Luz Bellido Diaz
- Andalusian Center of Molecular Biology and Regenerative Medicine, Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Avda. Americo Vespucio s/n, Parque Cientifico y Tecnologico, Isla de la Cartuja 41092, Sevilla, Spain; E-Mails: (P.D.G.); (A.K.); (M.L.B.D.)
| | - Veselina Moskova-Doumanova
- Biological Faculty, Sofia University “Saint Kliment Ohridski”, 8 Dragan Tzankov str, Sofia 1164, Bulgaria; E-Mail:
| | - Marie-Elise Lancelot
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
| | - José-Alain Sahel
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
- Centre de Référence Maladies Rares/Centre d’Investigation Clinique (CMR/CIC), 503 INSERM, CHNO des Quinze-Vingts, Paris F-75012, France
- Fondation Ophtalmologique Adolphe de Rothschild, Paris F-75019, France
| | - Emeline F. Nandrot
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
| | - Shomi S. Bhattacharya
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
- Andalusian Center of Molecular Biology and Regenerative Medicine, Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Avda. Americo Vespucio s/n, Parque Cientifico y Tecnologico, Isla de la Cartuja 41092, Sevilla, Spain; E-Mails: (P.D.G.); (A.K.); (M.L.B.D.)
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
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Sheng X, Chen X, Zhao K, Liu Y, Vollrath D, Zhao C. A Novel Homozygous BEST1 Mutation Correlates with Complex Ocular Phenotypes. Ophthalmology 2013; 120:1511-2.e2. [PMID: 23823511 DOI: 10.1016/j.ophtha.2013.03.043] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 03/27/2013] [Indexed: 11/16/2022] Open
Affiliation(s)
- Xunlun Sheng
- Ningxia Eye Hospital, Ningxia People's Hospital, Ningxia, China
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Cascavilla ML, Querques G, Stenirri S, Battaglia Parodi M, Querques L, Bandello F. Unilateral vitelliform phenotype in autosomal recessive bestrophinopathy. Ophthalmic Res 2012; 48:146-50. [PMID: 22584882 DOI: 10.1159/000338750] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2012] [Indexed: 11/19/2022]
Abstract
AIMS It was the aim of this study to report on a patient in whom a novel mutation in the BEST1 gene was responsible for unilateral vitelliform phenotype in autosomal recessive bestrophinopathy (ARB). METHODS An 8-year-old young girl (proband) with unilateral vitelliform phenotype underwent a complete ophthalmologic examination at baseline (time of diagnosis) and 2 years later. Genomic DNA was extracted to look for BEST1 gene mutations in the patient and her parents. RESULTS Fundus autofluorescence imaging and spectral-domain optical coherence tomography showed unchanged findings in the right eye over the 2-year follow-up period. Conversely, both fundus autofluorescence imaging and spectral-domain optical coherence tomography showed a partial reabsorption of the hyper-autofluorescent/hyper-reflective subretinal material in the left macula over the 2-year follow-up period. On BEST1 gene analysis, the patient presented a novel mutation c.535_537delAAC (p.Asn179del) in homozygous condition; interestingly, despite the absence of parents' consanguinity, both the father and mother showed the same novel mutation in heterozygous condition. CONCLUSION This case of unilateral vitelliform phenotype further supports the notion that ARB represents a disease spectrum in terms of severity, age at onset and heritability.
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Affiliation(s)
- Maria Lucia Cascavilla
- Department of Ophthalmology, University Vita Salute San Raffaele, San Raffaele Scientific Institute, Milan, Italy
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Milenkovic VM, Röhrl E, Weber BHF, Strauss O. Disease-associated missense mutations in bestrophin-1 affect cellular trafficking and anion conductance. J Cell Sci 2012; 124:2988-96. [PMID: 21878505 DOI: 10.1242/jcs.085878] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Bestrophin-1, an integral membrane protein encoded by the BEST1 gene, is localized predominantly to the basolateral membrane of the retinal pigment epithelium. Mutations in the BEST1 gene have been associated with Best vitelliforme macular dystrophy (BMD), a central retinopathy with autosomal dominant inheritance and variable penetrance. Over 120 disease-causing mutations are known, the majority of which result in amino acid substitutions within four mutational hot-spot regions in the highly conserved N-terminal half of the protein. Although initially thought to impair Cl⁻ channel function, the molecular pathology of BEST1 mutations is still controversial. We have analyzed the subcellular localization of 13 disease-associated BEST1 mutant proteins in polarized MDCK II cells, an established model of apical to basolateral protein sorting. Immunostaining demonstrated that nine of the 13 mutant proteins failed to integrate into the cell membrane. The defective proteins were predominantly retained in the cytoplasm, whereas wild-type bestrophin-1 revealed cell membrane localization. Functional analysis of I⁻ fluxes in HEK-293 cells showed that all mutants exhibited a significant reduction in anion conductance. Our data indicate that defective intracellular trafficking could be a common cause of BMD accompanied by impaired anion conductance, representing a loss of anion channel function that is probably due to mistargeting of mutant protein.
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Affiliation(s)
- Vladimir M Milenkovic
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, 93054 Regensburg, Germany
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Guziewicz KE, Aguirre GD, Zangerl B. Modeling the structural consequences of BEST1 missense mutations. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 723:611-8. [PMID: 22183385 PMCID: PMC3951900 DOI: 10.1007/978-1-4614-0631-0_78] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Yi L, Donsante A, Kennerson ML, Mercer JFB, Garbern JY, Kaler SG. Altered intracellular localization and valosin-containing protein (p97 VCP) interaction underlie ATP7A-related distal motor neuropathy. Hum Mol Genet 2011; 21:1794-807. [PMID: 22210628 DOI: 10.1093/hmg/ddr612] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
ATP7A is a P-type ATPase that regulates cellular copper homeostasis by activity at the trans-Golgi network (TGN) and plasma membrane (PM), with the location normally governed by intracellular copper concentration. Defects in ATP7A lead to Menkes disease or its milder variant, occipital horn syndrome or to a newly discovered condition, ATP7A-related distal motor neuropathy (DMN), for which the precise pathophysiology has been obscure. We investigated two ATP7A motor neuropathy mutations (T994I, P1386S) previously associated with abnormal intracellular trafficking. In the patients' fibroblasts, total internal reflection fluorescence microscopy indicated a shift in steady-state equilibrium of ATP7A(T994I) and ATP7A(P1386S), with exaggerated PM localization. Transfection of Hek293T cells and NSC-34 motor neurons with the mutant alleles tagged with the Venus fluorescent protein also revealed excess PM localization. Endocytic retrieval of the mutant alleles from the PM to the TGN was impaired. Immunoprecipitation assays revealed an abnormal interaction between ATP7A(T994I) and p97/VCP, an ubiquitin-selective chaperone which is mutated in two autosomal dominant forms of motor neuron disease: amyotrophic lateral sclerosis and inclusion body myopathy with early-onset Paget disease and fronto-temporal dementia. Small-interfering RNA (SiRNA) knockdown of p97/VCP corrected ATP7A(T994I) mislocalization. Flow cytometry documented that non-permeabilized ATP7A(P1386S) fibroblasts bound a carboxyl-terminal ATP7A antibody, consistent with relocation of the ATP7A di-leucine endocytic retrieval signal to the extracellular surface and partially destabilized insertion of the eighth transmembrane helix. Our findings illuminate the mechanisms underlying ATP7A-related DMN and establish a link between p97/VCP and genetically distinct forms of motor neuron degeneration.
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Affiliation(s)
- Ling Yi
- Unit on Human Copper Metabolism, Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892-1853, USA
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Tzekov R, Stein L, Kaushal S. Protein misfolding and retinal degeneration. Cold Spring Harb Perspect Biol 2011; 3:a007492. [PMID: 21825021 DOI: 10.1101/cshperspect.a007492] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The retina is a highly complex and specialized organ that performs preliminary analysis of visual information. Composed of highly metabolically active tissue, the retina requires a precise and well-balanced means of maintaining its functional activity during extended periods of time. Maintenance and regulation of a vast array of different structural and functional proteins is required for normal function of the retina. This process is referred to as protein homeostasis and involves a variety of activities, including protein synthesis, folding, transport, degradation, elimination, and recycling. Deregulation of any of these activities can lead to malfunctioning of the retina, from subtle subclinical signs to severe retinal degenerative diseases leading to blindness. Examples of retinal degenerative diseases caused by disruption of protein homeostasis include retinitis pigmentosa and Stargardt's disease. A detailed discussion of the role of disruption in protein homeostasis in these and other retinal diseases is presented, followed by examples of some existing and potential treatments.
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Affiliation(s)
- Radouil Tzekov
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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42
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Waldman YY, Tuller T, Keinan A, Ruppin E. Selection for translation efficiency on synonymous polymorphisms in recent human evolution. Genome Biol Evol 2011; 3:749-61. [PMID: 21803767 PMCID: PMC3163469 DOI: 10.1093/gbe/evr076] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Synonymous mutations are considered to be "silent" as they do not affect protein sequence. However, different silent codons have different translation efficiency (TE), which raises the question to what extent such mutations are really neutral. We perform the first genome-wide study of natural selection operating on TE in recent human evolution, surveying 13,798 synonymous single nucleotide polymorphisms (SNPs) in 1,198 unrelated individuals from 11 populations. We find evidence for both negative and positive selection on TE, as measured based on differentiation in allele frequencies between populations. Notably, the likelihood of an SNP to be targeted by positive or negative selection is correlated with the magnitude of its effect on the TE of the corresponding protein. Furthermore, negative selection acting against changes in TE is more marked in highly expressed genes, highly interacting proteins, complex members, and regulatory genes. It is also more common in functional regions and in the initial segments of highly expressed genes. Positive selection targeting sites with a large effect on TE is stronger in lowly interacting proteins and in regulatory genes. Similarly, essential genes are enriched for negative TE selection while underrepresented for positive TE selection. Taken together, these results point to the significant role of TE as a selective force operating in humans and hence underscore the importance of considering silent SNPs in interpreting associations with complex human diseases. Testifying to this potential, we describe two synonymous SNPs that may have clinical implications in phenylketonuria and in Best's macular dystrophy due to TE differences between alleles.
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Affiliation(s)
- Yedael Y Waldman
- Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv, Israel
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43
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Autosomal recessive vitelliform macular dystrophy in a large cohort of vitelliform macular dystrophy patients. Retina 2011; 31:581-95. [PMID: 21273940 DOI: 10.1097/iae.0b013e318203ee60] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
PURPOSE To report 11 cases of autosomal recessive vitelliform macular dystrophy and to compare their molecular findings and phenotypic characteristics with those of patients with the more common and well-described dominant form of the disease. METHODS Blood samples were obtained from 435 unrelated individuals with a clinical diagnosis of vitelliform macular dystrophy and screened for mutations in the coding sequences of BEST1. Medical records and retinal photographs of selected patients were reviewed. RESULTS Nine of the 435 probands were found to have 2 plausible disease-causing variations in BEST1, while 198 individuals were found to have heterozygous variations compatible with autosomal dominant inheritance. Inheritance phase was determined in three of the recessive families. Six novel disease-causing mutations were identified among these recessive patients: Arg47Cys, IVS7-2A>G, IVS7+4G>A, Ile205del12ATCCTGCTCCAGAG, Pro274Arg, and Ile366delCAGGTGTGGC. Forty-four novel disease-causing mutations were identified among the patients with presumed autosomal dominant disease. The phenotype of patients with recessive alleles for BEST1 ranged from typical vitelliform lesions to extensive extramacular deposits. CONCLUSION The authors provide evidence that two abnormal BEST1 alleles, neither of which causes macular disease alone, can act in concert to cause early-onset vitelliform macular dystrophy.
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Wittström E, Ponjavic V, Bondeson ML, Andréasson S. Anterior Segment Abnormalities and Angle-Closure Glaucoma in a Family with a Mutation in theBEST1Gene and Best Vitelliform Macular Dystrophy. Ophthalmic Genet 2011; 32:217-27. [DOI: 10.3109/13816810.2011.567884] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Wittström E, Ekvall S, Schatz P, Bondeson ML, Ponjavic V, Andréasson S. Morphological and functional changes in multifocal vitelliform retinopathy and biallelic mutations in BEST1. Ophthalmic Genet 2010; 32:83-96. [PMID: 21192766 DOI: 10.3109/13816810.2010.535890] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE To describe morphological and functional changes in a single patient with multifocal Best vitelliform macular dystrophy (BVMD) and to perform a genotype/phenotype correlation. METHODS The proband with multifocal BVMD and three of her family members were examined with electrooculography (EOG), full-field electroretinography (full-field ERG), multifocal electroretinography (mfERG) and optical coherence tomography (OCT). Genomic DNA was screened for mutation in the BEST1 gene by DNA sequencing analysis. RESULTS The proband was observed regularly during a follow-up period of 4 years. Full-field ERG demonstrated reduced and delayed responses of both rods and cones. OCT demonstrated intra- and subretinal fluid which seemed to fluctuate with periods of stress, similar to that seen in chronic central serous chorioretinopathy. Two distinct heterozygous BEST1 mutations were identified in the proband, the recurrent p.R141H mutation and the p.P233A mutation. Heterozygous p.R141H mutations were also identified in two family members, while p.P233A was a de novo mutation. Abnormal EOG findings were observed in both the proband and in the carriers of p.R141H. Heterozygous carriers showed delayed implicit times in a- and b-waves of combined total rod and cone full-field ERG responses. CONCLUSIONS The p.R141H mutation is frequently seen together with multifocal vitelliform retinopathy and biallelic mutations in BEST1. Our results show that carriers of the p.R141H mutation are clinically unaffected but present with abnormal EOG and full-field ERG findings. A patient with biallelic mutations of the BEST1 gene, causing multifocal BVMD with progressive, widespread functional disturbance of the retina, confirmed by full-field and mfERG is described.
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Chacon-Camacho OF, Camarillo-Blancarte L, Zenteno JC. OCT findings in young asymptomatic subjects carrying familialBEST1gene mutations. Ophthalmic Genet 2010; 32:24-30. [DOI: 10.3109/13816810.2010.524906] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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47
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Booij JC, Boon CJF, van Schooneveld MJ, ten Brink JB, Bakker A, de Jong PTVM, Hoyng CB, Bergen AAB, Klaver CCW. Course of visual decline in relation to the Best1 genotype in vitelliform macular dystrophy. Ophthalmology 2010; 117:1415-22. [PMID: 20381869 DOI: 10.1016/j.ophtha.2009.11.044] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 11/24/2009] [Accepted: 11/25/2009] [Indexed: 11/19/2022] Open
Abstract
PURPOSE To describe the disease course in patients with vitelliform macular dystrophy (VMD) with a Best1 mutation and to determine the association between Best1 genotype and visual prognosis. DESIGN Consecutive case series. PARTICIPANTS Fifty-three patients with VMD with Best1 mutations from 27 Dutch families, aged 11 to 87 years. METHODS Best-corrected visual acuity (VA), fundus appearance, and Arden ratio on the electro-oculogram (EOG) during clinical follow-up were assessed from medical records. Mutation analysis of the Best1 gene was performed on DNA samples using denaturing high-pressure liquid chromatography and direct sequencing. MAIN OUTCOME MEASURES Cumulative lifetime risk of visual decline below 0.5, 0.3, and 0.1 for the entire group and stratified for genotype. RESULTS Median age of onset of visual symptoms was 33 years (range: 2-78). The cumulative risk of VA below 0.5 (20/40) was 50% at 55 years and 75% at 66 years. The cumulative risk of decline less than 0.3 (20/63) was 50% by age 66 years and 75% by age 74 years. Two patients progressed to VA less than 0.1 (20/200). Fourteen different mutations were found. Most patients (96%) had missense mutations; the Thr6Pro, Ala10Val, and Tyr227Asn mutations were most common. Visual decline was significantly faster in patients with an Ala10Val mutation than either the Thr6Pro or the Tyr227Asn mutation (P=0.001). CONCLUSIONS Age of onset of visual symptoms varies greatly among patients with VMD. All patients show a gradual decrease in VA, and most progress to visual impairment at a relatively late age. Our data suggest a phenotype-genotype correlation, because the Ala10Val mutation has a more rapid disease progression than other common mutations. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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Affiliation(s)
- Judith C Booij
- Department of Clinical and Molecular Ophthalmogenetics, the Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
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Davidson AE, Millar ID, Urquhart JE, Burgess-Mullan R, Shweikh Y, Parry N, O'Sullivan J, Maher GJ, McKibbin M, Downes SM, Lotery AJ, Jacobson SG, Brown PD, Black GC, Manson FD. Missense mutations in a retinal pigment epithelium protein, bestrophin-1, cause retinitis pigmentosa. Am J Hum Genet 2009; 85:581-92. [PMID: 19853238 PMCID: PMC2775838 DOI: 10.1016/j.ajhg.2009.09.015] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 09/16/2009] [Accepted: 09/24/2009] [Indexed: 10/20/2022] Open
Abstract
Bestrophin-1 is preferentially expressed at the basolateral membrane of the retinal pigmented epithelium (RPE) of the retina. Mutations in the BEST1 gene cause the retinal dystrophies vitelliform macular dystrophy, autosomal-dominant vitreochoroidopathy, and autosomal-recessive bestrophinopathy. Here, we describe four missense mutations in bestrophin-1, three that we believe are previously unreported, in patients diagnosed with autosomal-dominant and -recessive forms of retinitis pigmentosa (RP). The physiological function of bestrophin-1 remains poorly understood although its heterologous expression induces a Cl--specific current. We tested the effect of RP-causing variants on Cl- channel activity and cellular localization of bestrophin-1. Two (p.L140V and p.I205T) produced significantly decreased chloride-selective whole-cell currents in comparison to those of wild-type protein. In a model system of a polarized epithelium, two of three mutations (p.L140V and p.D228N) caused mislocalization of bestrophin-1 from the basolateral membrane to the cytoplasm. Mutations in bestrophin-1 are increasingly recognized as an important cause of inherited retinal dystrophy.
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Affiliation(s)
- Alice E. Davidson
- Genetic Medicine, The University of Manchester, Manchester Academic Heath Science Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
| | - Ian D. Millar
- Faculty of Life Sciences, The University of Manchester, Manchester, UK
| | - Jill E. Urquhart
- National Genetics Reference Laboratory, St. Mary's Hospital, Manchester, UK
| | - Rosemary Burgess-Mullan
- Genetic Medicine, The University of Manchester, Manchester Academic Heath Science Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
| | - Yusrah Shweikh
- Genetic Medicine, The University of Manchester, Manchester Academic Heath Science Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
| | - Neil Parry
- Manchester Royal Eye Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
| | - James O'Sullivan
- National Genetics Reference Laboratory, St. Mary's Hospital, Manchester, UK
| | - Geoffrey J. Maher
- Genetic Medicine, The University of Manchester, Manchester Academic Heath Science Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
| | | | | | | | - Samuel G. Jacobson
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, PA, USA
| | - Peter D. Brown
- Faculty of Life Sciences, The University of Manchester, Manchester, UK
| | - Graeme C.M. Black
- Genetic Medicine, The University of Manchester, Manchester Academic Heath Science Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
- Manchester Royal Eye Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
| | - Forbes D.C. Manson
- Genetic Medicine, The University of Manchester, Manchester Academic Heath Science Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
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Best1 is a gene regulated by nerve injury and required for Ca2+-activated Cl- current expression in axotomized sensory neurons. J Neurosci 2009; 29:10063-71. [PMID: 19675239 DOI: 10.1523/jneurosci.1312-09.2009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We investigated the molecular determinants of Ca(2+)-activated chloride current (CaCC) expressed in adult sensory neurons after a nerve injury. Dorsal root ganglia express the transcripts of three gene families known to induce CaCCs in heterologous systems: bestrophin, tweety, and TMEM16. We found with quantitative transcriptional analysis and in situ hybridization that nerve injury induced upregulation of solely bestrophin-1 transcripts in sensory neurons. Gene screening with RNA interference in single neurons demonstrated that mouse Best1 is required for the expression of CaCC in injured sensory neurons. Transfecting injured sensory neurons with bestrophin-1 mutants inhibited endogenous CaCC. Exogenous expression of the fusion protein green fluorescent protein-Bestrophin-1 in naive neurons demonstrated a plasma membrane localization of the protein that generates a CaCC with biophysical and pharmacological properties similar to endogenous CaCC. Our data suggest that Best1 belongs to a group of genes upregulated by nerve injury and supports functional CaCC expression in injured sensory neurons.
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Xiao Q, Yu K, Cui YY, Hartzell HC. Dysregulation of human bestrophin-1 by ceramide-induced dephosphorylation. J Physiol 2009; 587:4379-91. [PMID: 19635817 DOI: 10.1113/jphysiol.2009.176800] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Best vitelliform macular dystrophy is an inherited autosomal dominant, juvenile onset form of macular degeneration caused by mutations in a chloride ion channel, human bestrophin-1 (hBest1). Mutations in Best1 have also been linked to several other forms of retinopathy. In addition to mutations, hBest1 dysfunction might come about by disruption of other processes that regulate Best1 function. Here we show that hBest1 chloride channel activity is regulated by ceramide and phosphorylation. We have identified a protein kinase C (PKC) phosphorylation site (serine 358) in hBest1 that is important for sustained channel function. Channel activity is maintained by PKC activators, protein phosphatase inhibitors, or pseudo-phosphorylation by substitution of glutamic acid for serine 358. When ceramide levels are elevated by exogenous addition of ceramide to the bath, by addition of bacterial sphingomyelinase, or by hypertonic stress, S358 is rapidly dephosphorylated. The dephosphorylation is mediated by protein phosphatase 2A. Hypertonic stress-induced dephosphorylation is blocked by a dihydroceramide, an inactive form of ceramide, and manumycin, an inhibitor of neutral sphingomyelinase. Our results support a model in which ceramide accumulation during early stages of retinopathy inhibits hBest1 function, leading to abnormal fluid transport across the retina, and enhanced inflammation.
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Affiliation(s)
- Qinghuan Xiao
- Department of Cell Biology and Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322, USA
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