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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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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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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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Functional assays of non-canonical splice-site variants in inherited retinal dystrophies genes. Sci Rep 2022; 12:68. [PMID: 34996991 PMCID: PMC8742059 DOI: 10.1038/s41598-021-03925-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 12/10/2021] [Indexed: 11/17/2022] Open
Abstract
Inherited retinal dystrophies are a group of disorders characterized by the progressive degeneration of photoreceptors leading to loss of the visual function and eventually to legal blindness. Although next generation sequencing (NGS) has revolutionized the molecular diagnosis of these diseases, the pathogenicity of some mutations casts doubts. After the screening of 208 patients with a panel of 117 genes, we obtained 383 variants that were analysed in silico with bioinformatic prediction programs. Based on the results of these tools, we selected 15 variants for their functional assessment. Therefore, we carried out minigene assays to unveil whether they could affect the splicing of the corresponding gene. As a whole, seven variants were found to induce aberrant splicing in the following genes: BEST1, CACNA2D4, PRCD, RIMS1, FSCN2, MERTK and MAK. This study shows the efficacy of a workflow, based on the association of the Minimum Allele Frequency, family co-segregation, in silico predictions and in vitro assays to determine the effect of potential splice site variants identified by DNA-based NGS. These findings improve the molecular diagnosis of inherited retinal dystrophies and will allow some patients to benefit from the upcoming gene-based therapeutic strategies.
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Frecer V, Iarossi G, Salvetti AP, Maltese PE, Delledonne G, Oldani M, Staurenghi G, Falsini B, Minnella AM, Ziccardi L, Magli A, Colombo L, D'Esposito F, Miertus J, Viola F, Attanasio M, Maggio E, Bertelli M. Pathogenicity of new BEST1 variants identified in Italian patients with best vitelliform macular dystrophy assessed by computational structural biology. J Transl Med 2019; 17:330. [PMID: 31570112 PMCID: PMC6771118 DOI: 10.1186/s12967-019-2080-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 09/21/2019] [Indexed: 11/18/2022] Open
Abstract
Background Best vitelliform macular dystrophy (BVMD) is an autosomal dominant macular degeneration. The typical central yellowish yolk-like lesion usually appears in childhood and gradually worsens. Most cases are caused by variants in the BEST1 gene which encodes bestrophin-1, an integral membrane protein found primarily in the retinal pigment epithelium. Methods Here we describe the spectrum of BEST1 variants identified in a cohort of 57 Italian patients analyzed by Sanger sequencing. In 13 cases, the study also included segregation analysis in affected and unaffected relatives. We used molecular mechanics to calculate two quantitative parameters related to calcium-activated chloride channel (CaCC composed of 5 BEST1 subunits) stability and calcium-dependent activation and related them to the potential pathogenicity of individual missense variants detected in the probands. Results Thirty-six out of 57 probands (63% positivity) and 16 out of 18 relatives proved positive to genetic testing. Family study confirmed the variable penetrance and expressivity of the disease. Six of the 27 genetic variants discovered were novel: p.(Val9Gly), p.(Ser108Arg), p.(Asn179Asp), p.(Trp182Arg), p.(Glu292Gln) and p.(Asn296Lys). All BEST1 variants were assessed in silico for potential pathogenicity. Our computational structural biology approach based on 3D model structure of the CaCC showed that individual amino acid replacements may affect channel shape, stability, activation, gating, selectivity and throughput, and possibly also other features, depending on where the individual mutated amino acid residues are located in the tertiary structure of BEST1. Statistically significant correlations between mean logMAR best-corrected visual acuity (BCVA), age and modulus of computed BEST1 dimerization energies, which reflect variations in the in CaCC stability due to amino acid changes, permitted us to assess the pathogenicity of individual BEST1 variants. Conclusions Using this computational approach, we designed a method for estimating BCVA progression in patients with BEST1 variants.
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Affiliation(s)
- Vladimir Frecer
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovakia
| | - Giancarlo Iarossi
- Department of Ophthalmology, Bambino Gesù IRCCS Children's Hospital, Rome, Italy
| | - Anna Paola Salvetti
- Department of Biomedical and Clinical Sciences "Luigi Sacco", Sacco Hospital, University of Milan, Milan, Italy
| | | | - Giulia Delledonne
- Department of Biomedical and Clinical Sciences "Luigi Sacco", Sacco Hospital, University of Milan, Milan, Italy
| | - Marta Oldani
- Department of Biomedical and Clinical Sciences "Luigi Sacco", Sacco Hospital, University of Milan, Milan, Italy
| | - Giovanni Staurenghi
- Department of Biomedical and Clinical Sciences "Luigi Sacco", Sacco Hospital, University of Milan, Milan, Italy
| | - Benedetto Falsini
- Institute of Ophthalmology, Visual Electrophysiology Service, Fondazione Policlinico Gemelli/UniversitàCattolica del S. Cuore, Rome, Italy
| | - Angelo Maria Minnella
- Institute of Ophthalmology, Visual Electrophysiology Service, Fondazione Policlinico Gemelli/UniversitàCattolica del S. Cuore, Rome, Italy
| | - Lucia Ziccardi
- Neurophthalmology and Neurophysiology Unit, GB Bietti Foundation-IRCCS, Rome, Italy
| | - Adriano Magli
- Department of Ophthalmology, Orthoptic and Pediatric Ophthalmology, University of Salerno, Salerno, Italy
| | - Leonardo Colombo
- Department of Ophthalmology, San Paolo Hospital, University of Milan, Milan, Italy
| | - Fabiana D'Esposito
- Imperial College Ophthalmic Research Unit, Western Eye Hospital, Imperial College Healthcare NHS Trust, London, UK.,Eye Clinic, Department of Neurosciences, Reproductive Sciences and Dentistry, University of Naples Federico II, Naples, Italy.,MAGI Euregio, Bolzano, Italy
| | | | - Francesco Viola
- Department of Ophthalmology, Fondazione IRCCS Cà Granda, Clinica Regina Elena, Milan, Italy
| | | | - Emilia Maggio
- IRCCS-Ospedale Sacro Cuore Don Calabria, Negrar, VR, Italy
| | - Matteo Bertelli
- MAGI'S Lab S.R.L., Via Delle Maioliche 57/D, 38068, Rovereto, TN, Italy.,MAGI Euregio, Bolzano, Italy
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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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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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Mislocalisation of BEST1 in iPSC-derived retinal pigment epithelial cells from a family with autosomal dominant vitreoretinochoroidopathy (ADVIRC). Sci Rep 2016; 6:33792. [PMID: 27653836 PMCID: PMC5031956 DOI: 10.1038/srep33792] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 08/26/2016] [Indexed: 12/31/2022] Open
Abstract
Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is a rare, early-onset retinal dystrophy characterised by distinct bands of circumferential pigmentary degeneration in the peripheral retina and developmental eye defects. ADVIRC is caused by mutations in the Bestrophin1 (BEST1) gene, which encodes a transmembrane protein thought to function as an ion channel in the basolateral membrane of retinal pigment epithelial (RPE) cells. Previous studies suggest that the distinct ADVIRC phenotype results from alternative splicing of BEST1 pre-mRNA. Here, we have used induced pluripotent stem cell (iPSC) technology to investigate the effects of an ADVIRC associated BEST1 mutation (c.704T > C, p.V235A) in patient-derived iPSC-RPE. We found no evidence of alternate splicing of the BEST1 transcript in ADVIRC iPSC-RPE, however in patient-derived iPSC-RPE, BEST1 was expressed at the basolateral membrane and the apical membrane. During human eye development we show that BEST1 is expressed more abundantly in peripheral RPE compared to central RPE and is also expressed in cells of the developing retina. These results suggest that higher levels of mislocalised BEST1 expression in the periphery, from an early developmental stage, could provide a mechanism that leads to the distinct clinical phenotype observed in ADVIRC patients.
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Uggenti C, Briant K, Streit AK, Thomson S, Koay YH, Baines RA, Swanton E, Manson FD. Restoration of mutant bestrophin-1 expression, localisation and function in a polarised epithelial cell model. Dis Model Mech 2016; 9:1317-1328. [PMID: 27519691 PMCID: PMC5117222 DOI: 10.1242/dmm.024216] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 07/21/2016] [Indexed: 01/13/2023] Open
Abstract
Autosomal recessive bestrophinopathy (ARB) is a retinopathy caused by mutations in the bestrophin-1 protein, which is thought to function as a Ca2+-gated Cl− channel in the basolateral surface of the retinal pigment epithelium (RPE). Using a stably transfected polarised epithelial cell model, we show that four ARB mutant bestrophin-1 proteins were mislocalised and subjected to proteasomal degradation. In contrast to the wild-type bestrophin-1, each of the four mutant proteins also failed to conduct Cl− ions in transiently transfected cells as determined by whole-cell patch clamp. We demonstrate that a combination of two clinically approved drugs, bortezomib and 4-phenylbutyrate (4PBA), successfully restored the expression and localisation of all four ARB mutant bestrophin-1 proteins. Importantly, the Cl− conductance function of each of the mutant bestrophin-1 proteins was fully restored to that of wild-type bestrophin-1 by treatment of cells with 4PBA alone. The functional rescue achieved with 4PBA is significant because it suggests that this drug, which is already approved for long-term use in infants and adults, might represent a promising therapy for the treatment of ARB and other bestrophinopathies resulting from missense mutations in BEST1. Summary: Chemical chaperone 4PBA fully restores Cl− conductance activity for mutant bestrophin-1 proteins associated with inherited retinal dystrophy, autosomal recessive bestrophinopathy.
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Affiliation(s)
- Carolina Uggenti
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Kit Briant
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Anne-Kathrin Streit
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Steven Thomson
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Yee Hui Koay
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Richard A Baines
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Eileithyia Swanton
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Forbes D Manson
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
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Marmorstein AD, Kinnick TR, Stanton JB, Johnson AA, Lynch RM, Marmorstein LY. Bestrophin-1 influences transepithelial electrical properties and Ca2+ signaling in human retinal pigment epithelium. Mol Vis 2015; 21:347-59. [PMID: 25878489 PMCID: PMC4390793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 03/30/2015] [Indexed: 11/16/2022] Open
Abstract
PURPOSE Mutations in BEST1, encoding Bestrophin-1 (Best1), cause Best vitelliform macular dystrophy (BVMD) and other inherited retinal degenerative diseases. Best1 is an integral membrane protein localized to the basolateral plasma membrane of the retinal pigment epithelium (RPE). Data from numerous in vitro and in vivo models have demonstrated that Best1 regulates intracellular Ca2+ levels. Although it is known from in vitro and crystal structure data that Best1 is also a calcium-activated anion channel, evidence for Best1 functioning as a channel in human RPE is lacking. To assess Best1-associated channel activity in the RPE, we examined the transepithelial electrical properties of fetal human RPE (fhRPE) cells, which express endogenous Best1. METHODS Using adenovirus-mediated gene transfer, we overexpressed Best1 and the BVMD mutant Best1W93C in fhRPE cells and assessed resting transepithelial potential (TEP), transepithelial resistance, short circuit current (Isc), and intracellular Ca2+ levels. Cl- currents were directly measured in transfected HEK293 cells using whole-cell patch clamp. RESULTS Best1W93C showed ablated Cl- currents and, when co-expressed, suppressed the channel activity of Best1 in HEK293 cells. In fhRPE, overexpression of Best1 increased TEP and Isc, while Best1W93C diminished TEP and Isc. Substitution of Cl- in the bath media resulted in a significant reduction of Isc in monolayers overexpressing Best1, but no significant Isc change in monolayers expressing Best1W93C. We removed Ca2+ as a limit on transepithelial electrical properties by treating cells with ionomycin, and found that changes in Isc and TEP for monolayers expressing Best1 were absent in monolayers expressing Best1W93C. Similarly, inhibition of calcium-activated anion channels with niflumic acid reduced both Isc and TEP of control and Best1 monolayers, but did not notably affect Best1W93C monolayers. Stimulation with extracellular ATP induced an increase in TEP in control monolayers that was greater than that observed in those expressing Best1(W93C). Examination of [Ca2+]i following ATP stimulation demonstrated that the expression of Best1W93C impaired intracellular Ca2+ signaling. CONCLUSIONS These data indicate that Best1 activity strongly influences electrophysiology and Ca2+ signaling in RPE cells, and that a common BVMD mutation disrupts both of these parameters. Our findings support the hypothesis that Best1 functions as an anion channel in human RPE.
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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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Veleva R, Petkova B, Moskova-Doumanova V, Doumanov J, Dimitrova M, Koleva P, Mladenova K, Petrova S, Yordanova Z, Kapchina-Toteva V, Topouzova-Hristova T. Changes in the functional characteristics of tumor and normal cells after treatment with extracts of white dead-nettle. BIOTECHNOL BIOTEC EQ 2014; 29:181-188. [PMID: 26019631 PMCID: PMC4433899 DOI: 10.1080/13102818.2014.989094] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 10/09/2014] [Indexed: 12/04/2022] Open
Abstract
Lamium album L. is a perennial herb widely used in folk medicine. It possesses a wide spectrum of therapeutic activities (anti-inflammatory, astringent, antiseptic, antibiotic, antispasmodic, antioxidant and anti-proliferative). Preservation of medicinal plant could be done by in vitro propagation to avoid depletion from their natural habitat. It is important to know whether extracts from L. album plants grown in vitro possess similar properties as extracts from plants grown in vivo. For these reasons, it is important to examine changes in the composition of secondary metabolites during in vitro cultivation of the plant and how they affect the biological activity. We used A549 human cancer cell line and normal kidney epithelial cells MDCKII (Madin–Darby canine kidney cells II) as controls in assessing the anti-cancer effect of plant extracts. To elucidate changes in some key functional characteristics, adhesion test, MTT (3-(4,5-dimethylthiazol-2-yl)-2-5-diphenyl tetrazolium bromide), transepithelial resistance (TER), immunofluorescence staining and trypan blue exclusion test were performed. Methanol and chloroform extracts of in vivo and in vitro propagated plants affected differently cancerous and non-cancerous cells. The most pronounced differences were observed in the morphological analysis and in the cell adhesive properties. We also detected suppressed epithelial transmembrane electrical resistance of MDCK II cells, by treatment with plant extracts, compared to non-treated MDCK II cells. A549 cells did not polarize under the same conditions. Altered organization of actin filaments in both cell types were noticed suggesting that extracts from L. album L. change TER and actin filaments, and somehow may block cell mechanisms, leading to the polarization of MDCK II cells.
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Affiliation(s)
- Ralitsa Veleva
- Department of Cytology, Histology and Embryology, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
| | - Bela Petkova
- Department of Plant Physiology, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
| | - Veselina Moskova-Doumanova
- Department of Cytology, Histology and Embryology, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
| | - Jordan Doumanov
- Department of Biochemistry, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
| | - Milena Dimitrova
- Department of Plant Physiology, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
| | - Petya Koleva
- Department of Cytology, Histology and Embryology, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
| | - Kirilka Mladenova
- Department of Biochemistry, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
| | - Svetla Petrova
- Department of Biochemistry, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
| | - Zhenya Yordanova
- Department of Plant Physiology, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
| | - Veneta Kapchina-Toteva
- Department of Plant Physiology, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
| | - Tanya Topouzova-Hristova
- Department of Cytology, Histology and Embryology, Faculty of Biology, Sofia University 'St. Kl. Ohridski' , Sofia , Bulgaria
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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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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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