Best Vitelliform Macular Dystrophy Natural History Study Report 1: Clinical Features and Genetic Findings.

PURPOSE: To analyze the genetic findings, clinical spectrum, and natural history of Best vitelliform macular dystrophy (BVMD) in a cohort of 222 children and adults. DESIGN: Single-center retrospective, consecutive, observational study. PARTICIPANTS: Patients with a clinical diagnosis of BVMD from pedigrees with a likely disease-causing monoallelic sequence variant in the BEST1 gene. METHODS: Data were extracted from electronic and physical case notes. Electrophysiologic assessment and molecular genetic testing were analyzed. MAIN OUTCOME MEASURES: Molecular genetic test findings and clinical findings including best-corrected visual acuity (BCVA), choroidal neovascularization (CNV) rates, and electrophysiologic parameters. RESULTS: Two hundred twenty-two patients from 141 families were identified harboring 69 BEST1 variants. Mean age at presentation was 26.8 years (range, 1.3-84.8 years) and most patients (61.5%) demonstrated deterioration of central vision. Major funduscopic findings included 128 eyes (30.6%) with yellow vitelliform lesions, 78 eyes (18.7%) with atrophic changes, 49 eyes (11.7%) with fibrotic changes, 48 eyes (11.5%) with mild pigmentary changes, and 43 eyes (10.3%) showing a vitelliruptive appearance. Mean BCVA was 0.37 logarithm of the minimum angle of resolution (logMAR; Snellen equivalent, 20/47) for the right eye and 0.33 logMAR (Snellen equivalent, 20/43) for the left eye at presentation, with a mean annual loss rate of 0.013 logMAR and 0.009 logMAR, respectively, over a mean follow-up of 9.7 years. Thirty-seven patients (17.3%) received a diagnosis of CNV over a mean follow-up of 8.0 years. Eyes with CNV that received treatment with an anti-vascular endothelial growth factor (VEGF) agent showed better mean BCVA compared with eyes that were not treated with an anti-VEGF agent (0.28 logMAR [Snellen equivalent, 20/38] vs. 0.62 logMAR [Snellen equivalent, 20/83]). Most eyes exhibited a hyperopic refractive error (78.7%), and 13 patients (6.1%) received a diagnosis of amblyopia. Among the 3 most common variants, p.(Ala243Val) was associated with a later age of onset, better age-adjusted BCVA, and less advanced Gass stages compared with p.(Arg218Cys) and p.(Arg218His). CONCLUSIONS: BVMD shows a wide spectrum of phenotypic variability. The disease is very slowly progressive, and the observed phenotype-genotype correlations allow for more accurate prognostication and counselling. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Variants of BEST1 and CRYBB2 cause a complex ocular phenotype comprising microphthalmia, microcornea, cataract, and vitelliform macular dystrophy: case report.

BACKGROUND: Best vitelliform macular dystrophy (BVMD), caused by pathogenic variants of the BEST1 gene, has not been reported in association with cataracts and ocular malformations. We reported a case with a complex ocular phenotype comprising microphthalmia, microcornea, cataract, and vitelliform macular dystrophy. CASE PRESENTATION: A six-year-old girl manifested photophobia and a poor visual behavior. A thorough ophthalmic examination revealed the patient to have bilateral microphthalmia, microcornea, congenital cataract, and Best vitelliform macular dystrophy (BVMD). Whole exome sequencing (WES) identified one variant in the BEST1 and one variant in CRYBB2 genes: c.218 T > G p.(Ile73Arg) and c.479G > C p.(Arg160Pro). The first variant was inherited from the proband's father, who was diagnosed with subclinical BVMD, while the second was a de novo variant. A minigene assay showed that c.218 T > G in BEST1 did not affect pre-mRNA splicing. CONCLUSIONS: This case suggests that the complex ocular phenotype comprising BVMD and congenital cataract with microphthalmia cannot be explained by variation in one gene but is caused by variants in BEST1 and CRYBB2. This case highlights the importance of general clinical evaluation and comprehensive genetic testing for diagnosing complex eye diseases.

Elaborate Evaluation of Farnsworth Dichotomous D-15 Panel Test Can Help Differentiate between Best Vitelliform Macular Dystrophy and Autosomal Recessive Bestrophinopathy.

INTRODUCTION: The colour vision in bestrophinopathies has not been assessed in detail so far. The aim of this study was to explore the extent to which distinct types of bestrophinopathies differ in regard to colour vision deficiencies using Farnsworth Dichotomous D-15 and Lanthony Desaturated D-15 panel tests. METHODS: Both D-15 tests were performed in 52 eyes of 26 patients with Best vitelliform macular dystrophy (BVMD) and 10 eyes of 5 patients with autosomal recessive bestrophinopathy (ARB). Two methods were used for a quantitative assessment of the colour vision deficiencies: moment of inertia method and Bowman method. The following parameters were calculated: confusion angle, confusion index (C-index), selectivity index (S-index), total error score (TES), and colour confusion index (CCI). RESULTS: The median value of confusion angle for all stages of BVMD fell into a narrow range around 62, indicating normal results. The median confusion angle value was 57 in ARB patients within a very wide range down to -82, indicating non-specific deficits. These differences were statistically significant. Significantly abnormal C-index and CCI values were found only in ARB patients, being 2.0 and 1.49, respectively. The majority of parameters of D-15 tests were independent of the visual acuity in both bestrophinopathies. CONCLUSIONS: Elaborate evaluation of the D-15 panel tests might help establish a differential diagnosis between different bestrophinopathies, as the pattern of the colour vision loss is different between BVMD and ARB. The quantitative parameters of colour vision tests in bestrophinopathies are independent of the visual acuity.

The pseudohypopyon stage in adult-onset foveomacular vitelliform dystrophy.

PURPOSE: To gain insight into the pathogenesis of adult-onset foveomacular vitelliform dystrophy (AFVD) via assessment of its pseudohypopyon stage (PHS). METHODS: Retrospectively, data were collected in a tertiary center from established cohorts of a genetically evaluated AFVD and best vitelliform macular dystrophy (BVMD) eyes in the pseudohypopyon stage. Best-corrected visual acuity (BCVA, LogMAR), lesion characterization, including lesion dimensions, liquefaction areas and patterns (altitudinal or lateral), and ellipsoid zone integrity were analyzed from spectral-domain optical coherence tomography images. RESULTS: Out of 167 eyes of 90 AFVD patients and 56 eyes of 28 BVMD patients, 8 eyes of six AFVD patients and five eyes of four BVMD patients were at the PHS were included. The mean LogMAR BCVA ± SD was 0.21 ± 0.20 and 0.41 ± 0.10 in AFVD and BVMD diseases, respectively (p = 0.13). Seven AFVD eyes (87.5%) demonstrated lateral liquefaction, while all BVMD eyes demonstrated an altitudinal pattern (p = 0.005). Maximal horizontal lesion diameters were 1.41 ± 0.46 mm and 2.64 ± 0.77 mm in AFVD and BVMD, respectively (p = 0.02). AFVD patients were older (69 ± 14) than BVMD patients (22 ± 13; p = 0.009). CONCLUSION: The pseudohypopyon stage in AFVD is often characterized by a lateral liquefaction pattern, unlike the altitudinal pattern characterizing BVMD. Age, lesion size, or pathogenesis pathways may underline the different pseudohypopyon stage patterns in AFVD and BVMD.

Genetic and clinical features of BEST1-associated retinopathy based on 59 Chinese families and database comparisons.

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.

Clinical findings in eyes with BEST1-related retinopathy complicated by choroidal neovascularization.

PURPOSE: To determine the characteristics of eyes diagnosed with Best vitelliform macular dystrophy (BVMD) and autosomal recessive bestrophinopathy (ARB) complicated by choroidal neovascularization (CNV). METHODS: This was a retrospective, multicenter observational case series. Fourteen genetically confirmed BVMD patients and 9 ARB patients who had been examined in 2 ophthalmological institutions in Japan were studied. The findings in a series of ophthalmic examinations including B-scan optical coherence tomography (OCT) and OCT angiography (OCTA) were reviewed. RESULTS: CNV was identified in 5 eyes (17.9%) of BVMD patients and in 2 eyes (11.1%) of ARB patients. Three of 5 eyes with BVMD were classified as being at the vitelliruptive stage and 2 eyes at the atrophic stage. The CNV in 2 BVMD eyes were diagnosed as exudative because of acute visual acuity reduction, retinal hemorrhage, and intraretinal fluid, while the CNV in 3 BVMD eyes and 2 ARB eyes were diagnosed as non-exudative. The visual acuity of the two eyes with exudative CNV did not improve despite anti-VEGF treatments. None of the eyes with non-exudative CNV had a reduction of their visual acuity for at least 4 years. All of the CNV were located within hyperreflective materials which were detected in 16 eyes (57.1%) of the BVMD eyes and in 7 eyes (38.9%) of the ARB eyes. CONCLUSIONS: CNV is a relatively common complication in BEST1-related retinopathy in Asian population as well. The prognosis of eyes with exudative CNV is not always good, and OCTA can detect CNV in eyes possessing hyperreflective materials.

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.

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.

A novel phenotype in a family with autosomal dominant retinal dystrophy due to c.1430A > G in retinoid isomerohydrolase (RPE65) and c.37C > T in bestrophin 1 (BEST1).

PURPOSE: The c.1430A > G (Asp477Gly) variant in RPE65 has been reported in Irish and Scottish families with either an autosomal dominant retinal dystrophy (adRD) that resembles choroideremia, a vitelliform macular dystrophy or an isolated macular atrophy. We report novel features on multimodal imaging and the natural history of a family harbouring this variant in combination with the BEST1 c.37C > T (Arg13Cys) variant. METHODS: Members of a family with an adRD were examined clinically to ascertain phenotype and underwent genetic testing. Multimodal imaging included widefield colour fundus photography, quantitative autofluorescence (qAF) and spectral domain optical coherence tomography. Electrophysiology and microperimetry were also performed. RESULTS: Vision loss was attributed to foveal atrophy in the proband and choroidal neovascularisation and a vitello-eruptive lesion in one affected son. Peripheral retinal white dots corresponding to subretinal deposits were seen in three patients. The median qAF8 values in the proband (I:1) were low (40 and 101 in OD and OS) at age 79. Similarly, the qAF8 values for the middle son (II:2) were also low (100 and 87 in ODS and OS) at age 60. Electrophysiology showed disproportionate reduction in Arden ratio prior to the gradual loss of full-field responses. Microperimetry demonstrated an enlarging scotoma in the proband. CONCLUSIONS: The coexistence of the pathogenic BEST1 c.37C > T variant may modify clinical features observed in RPE65 adRD. This study expands our understanding of RPE65 adRD as a retinoid cycle disorder supported by the reduced qAF, fine white retinal dots and corresponding subretinal deposits on OCT in affected members.

SHORT-TERM MODIFICATIONS OF ELLIPSOID ZONE IN BEST VITELLIFORM MACULAR DYSTROPHY.

PURPOSE: To assess ellipsoid zone (EZ) alterations in Best vitelliform macular dystrophy using spectral-domain optical coherence tomography. METHODS: Prospective, observational case series. Forty-three patients (43 eyes) underwent complete ophthalmological examination at baseline and at 24 months: best-corrected visual acuity (BCVA), biomicroscopy, fundus photography, and spectral-domain optical coherence tomography were performed. Acquisition protocol included 19-line raster scan. Alterations in EZ were marked on spectral-domain optical coherence tomography, and the area was manually calculated on a near-infrared reflectance image. Three patterns were identified: A (decrease >0.25 mm2), B (±0.25 mm2), and C (increase >0.25 mm2). Primary outcome was to describe different patterns of EZ alteration. Secondary outcomes included their correlation with BCVA and the description of a central optically preserved islet. RESULTS: At baseline, altered EZ was identified in 40 eyes. Worse BCVA significantly correlated with larger EZ alterations but not with lesion extension on fundus photograph. Only "pattern-C" eyes unveiled BCVA worsening at follow-up. Optically preserved islet was detected in 16 eyes (37%), disclosing significantly better vision; its disappearance at follow-up (n = 7; 44% of 16 eyes) correlated with a decrease in BCVA. CONCLUSION: The assessment of EZ status might represent a valuable functional marker in Best vitelliform macular dystrophy because stable alterations and the maintenance of a central optically preserved islet are associated with better visual acuity.

INTRARETINAL HYPERREFLECTIVE LINES.

PURPOSE: To report intraretinal hyperreflective lines related to various macular conditions. METHODS: All cases were imaged with color photographs, autofluorescence images, and spectral-domain optical coherence tomography, some with fluorescein and/or indocyanine green angiography. Demographic data, imaging, course and outcome were retrospectively analyzed. RESULTS: Forty-nine eyes of 43 patients (16 men and 27 women) were included. Hyperreflective vertical lines (38 eyes) or curvilinear lines along the Henle fiber layer (11 eyes) were present in association with various macular conditions: adult vitelliform dystrophy or pattern dystrophy (24 eyes) frequently associated with an epiretinal membrane (six eyes) and/or thick choroid (nine eyes), age-related maculopathy or macular degeneration (nine eyes), partial resorption of subretinal or intraretinal hemorrhages (five eyes), idiopathic macular microhole (two eyes), vitreomacular traction (three eyes), multiple evanescent white dot syndrome (three eyes), fundus flavimaculatus (two eyes), and pachychoroid pigment epitheliopathy (one eye). The lines fully vanished in cases of hemorrhages, multiple evanescent white dot syndrome or resolution of vitreomacular traction, but usually persisted with gradual thinning in the other conditions. CONCLUSION: The present series showed that intraretinal hyperreflective lines could occur in various inflammatory, degenerative, or tractional conditions. They could reflect a previously unrecognized reaction to various photoreceptor, Müller cell, and/or retinal pigment epithelium damage.

Acute exudative polymorphous vitelliform maculopathy during pembrolizumab treatment for metastatic melanoma: a case report.

BACKGROUND: The use of immunomodulating therapy to treat various cancers has been on the rise and these immune checkpoint inhibitors are known to cause ocular side effects. In this article a case of acute exudative polymorphous vitelliform maculopathy (AEPVM) is reported which developed during a first line treatment with pembrolizumab. CASE PRESENTATION: A 54-year-old woman was referred because of blurry vision in both eyes with a yellow spot in the central visual field of the left eye. These symptoms started after four treatments with pembrolizumab (a monoclonal antibody against the programmed cell death receptor-1) for a metastatic recurrent vaginal mucosal melanoma. Her best corrected visual acuity was 10/10 in both eyes with a correction of + 2.00 bilaterally. There were no inflammatory findings in the anterior segment or the vitreous. Fundoscopy revealed an attenuation of the foveal reflex with subtle yellow-white subretinal macular deposits (vitelliform lesions) in both eyes. Fluorescein angiography did not show staining or leakage in the mid-phase, neither a late staining. Spectral-domain optical coherence tomography of the macula illustrated bilateral neurosensory retinal detachment with a thick, highly reflective band at the outer photoreceptor segment. En face structural OCT at the level of the photoreceptors showed focal areas of increased signal corresponding to hyperreflective vitelliform material. The treatment with pembrolizumab was ceased immediately. During the following visits we slowly saw an improvement of the neurosensory retinal detachment. After almost four months a total resolution of the subretinal fluid was visualized in both eyes without the use of additional treatment, though the vitelliform deposits persisted. CONCLUSIONS: The development of AEPVM in melanoma patients could be triggered by treatment with Pembrolizumab. Pembrolizumab has the potential to disturb indirectly the retinal pigment epithelium homeostasis with accumulation of lipofuscin deposits and subretinal fluid, both signs of AEPVM.

The Role of Optical Coherence Tomography Angiography (OCTA) in Detecting Choroidal Neovascularization in Different Stages of Best Macular Dystrophy: A Case Series.

Best macular dystrophy (BMD) is an autosomal dominant macular dystrophy of childhood onset characterized by bilateral and symmetric vitelliform lesions. Several stages of disease have been well-described in the literature. Choroidal neovascularization (CNV) has traditionally been considered a hallmark of end-stage disease, and anti-vascular endothelial growth factor (anti-VEGF) agents have been used to improve visual prognosis. While CNV was historically detected with fluorescein angiography, optical coherence tomography angiography (OCTA) has recently been employed as a novel mechanism for identifying CNV in BMD. In this case series, we discuss our institutional experience with using OCTA to detect CNV in BMD and contextualize this experience within the broader emerging literature. While OCTA allows for the identification of CNV in less severe stages of BMD, the management of this CNV remains uncertain.

Disease-causing mutations associated with bestrophinopathies promote apoptosis in retinal pigment epithelium cells.

PURPOSE: Best vitelliform macular dystrophy (BVMD) and autosomal recessive bestrophinopathy (ARB) are two kinds of bestrophinopathies which are caused by BEST1 mutations and characterized by accumulation of lipofuscin-like materials on the retinal pigment epithelium cell-photoreceptor interface. In the past two decades, research about the pathogenesis of bestrophinopathies was mainly focused on the anion channel and intracellular Ca2+ signaling, but seldom concentrated on the function of retinal pigment epithelium (RPE) cells. In this study, we explored the possible effect of the three BEST1 mutations p.V143F, p.S142G, and p.A146T on the apoptosis in human fetal RPE cells. METHODS: Wild-type plasmid and mutant plasmids BEST1-pcDNA3.1 p.V143F, p.S142G, and p.A146T were transfected to human fetal RPE cells. The molecules caspase-3, phospho-Bcl-2, BAX, PARP, and AIF associated with apoptosis were determined by quantitative PCR and Western blot. Apoptotic rate and active Caspase-3 staining were analyzed by flow cytometry. RESULTS: Caspase-3 and PARP expression were significantly increased in BEST1-pcDNA3.1 p.S142G and p.A146T group. Flow cytometry showed that the apoptosis rates were significantly increased in the BEST1-pcDNA3.1 p.V143F, p.S142G, and p.A146T group compared with the wild-type group. CONCLUSIONS: For the first time, we found that the three mutations promoted RPE cell apoptosis. Furthermore, the results indicated that BEST1 mutations p.S142G and p.A146T may contribute apoptosis of RPE cells by targeting Caspase 3. Our observations suggested that the apoptosis of RPE cells may be one of the mechanisms in bestrophinopathies, which may provide a new potential therapeutic target for the treatment of this disease.

Natural course of the vitelliform stage in best vitelliform macular dystrophy: a five-year follow-up study.

PURPOSE: The vitelliform stage is the typical phenotypic manifestation of Best vitelliform macular dystrophy (BVMD). As yet, no study has focused specifically on the clinical changes occurring in the vitelliform stage over the follow-up. METHODS: The survey takes the form of a prospective observational study with a 5-year follow-up. Twenty-one eyes of 11 patients in the vitelliform stage were examined annually. The primary outcome was the identification of the changes in the vitelliform lesion over a 5-year follow-up. Secondary outcomes included changes in structural optical coherence tomography (OCT) parameters and the correlation with the BCVA variation over the follow-up. RESULTS: Spectral domain OCT at baseline showed one subform characterized by solid vitelliform deposition, in 81% of eyes, and another subform characterized by a combination of solid deposition and subretinal fluid, in 19% of eyes. Overall, 62% of eyes showed an increase in the area of vitelliform deposition. Once the maximal area was reached, a progressive flattening of the vitelliform deposition took place, with subsequent flattening of the vitelliform lesion and formation of subretinal fluid. Hyperreflective foci (HF) increased in number as long as the vitelliform area continued to expand, with no variation in HF when the vitelliform lesion flattened or the subretinal fluid formed. CONCLUSIONS: The vitelliform stage reveals more subforms with clinical variations over the follow-up. Our data suggest that the substage before the flattening of the lesion, thus before the so-called subretinal fluid accumulates and when the visual acuity is still high, might offer the best opportunity for an optimal therapeutic approach.

SEROUS MACULAR DETACHMENT IN BEST DISEASE: A Masquerade Syndrome.

PURPOSE: To describe the clinical and multimodal imaging findings of a series of cases of serous macular detachment (SMD) caused by Best disease (BD) masquerading as neovascular age-related macular degeneration or central serous chorioretinopathy that were inappropriately treated with intravitreal anti-vascular endothelial growth factor or laser therapy. This study will also present data to support age-related progressive choroidal thickening in BD patients, which may play a role in the development of SMD in this population. METHODS: Clinical examination and multimodal imaging findings, including color fundus photography, spectral-domain optical coherence tomography, fundus autofluorescence, fluorescein angiography, and optical coherence tomography-angiography, were reviewed and analyzed. Subfoveal choroidal thickness was also formally measured, and an age-related choroidal thickness analysis was performed and compared with a normal population. RESULTS: Twenty-six eyes of 13 patients (5 women) were included. Median age was 44 years. Nine patients presented with a history of SMD and subretinal fluid recalcitrant to various therapies, including intravitreal anti-vascular endothelial growth factor injections and photodynamic therapy. Best disease was subsequently diagnosed genetically in six patients and by detailed family history in seven. Mean logarithm of the minimum angle of resolution best-corrected visual acuity for all 26 eyes at last follow-up was +0.36 (Snellen equivalent of 20/46). Subfoveal choroidal thickness positively correlated with age for our cohort, increasing linearly at a rate of 25.6 µm per decade (R = 0.64; P < 0.001). Choroidal neovascularization was identified in four eyes on optical coherence tomography angiography, but these eyes did not respond to anti-vascular endothelial growth factor treatment. CONCLUSION: The diagnosis of BD should be considered in patients presenting with SMD and recalcitrant subretinal fluid masquerading as neovascular age-related macular degeneration or chronic central serous chorioretinopathy to avoid unnecessary treatment procedures. The positive correlation of subfoveal choroidal thickness with age in BD patients may be a factor in the pathogenesis and development of SMD in this population. Recognizing the multimodal imaging features of SMD associated with BD, described in detail in this study, will guide practitioners to the accurate diagnosis of BD and reduce the risk of unnecessary intraocular procedures with potential complications.

Mutation-Dependent Pathomechanisms Determine the Phenotype in the Bestrophinopathies.

Best vitelliform macular dystrophy (BD), autosomal dominant vitreoretinochoroidopathy (ADVIRC), and the autosomal recessive bestrophinopathy (ARB), together known as the bestrophinopathies, are caused by mutations in the bestrophin-1 (BEST1) gene affecting anion transport through the plasma membrane of the retinal pigment epithelium (RPE). To date, while no treatment exists a better understanding of BEST1-related pathogenesis may help to define therapeutic targets. Here, we systematically characterize functional consequences of mutant BEST1 in thirteen RPE patient cell lines differentiated from human induced pluripotent stem cells (hiPSCs). Both BD and ARB hiPSC-RPEs display a strong reduction of BEST1-mediated anion transport function compared to control, while ADVIRC mutations trigger an increased anion permeability suggesting a stabilized open state condition of channel gating. Furthermore, BD and ARB hiPSC-RPEs differ by the degree of mutant protein turnover and by the site of subcellular protein quality control with adverse effects on lysosomal pH only in the BD-related cell lines. The latter finding is consistent with an altered processing of catalytic enzymes in the lysosomes. The present study provides a deeper insight into distinct molecular mechanisms of the three bestrophinopathies facilitating functional categorization of the more than 300 known BEST1 mutations that result into the distinct retinal phenotypes.

Natural course of adult-onset vitelliform lesions in eyes with and without comorbid subretinal drusenoid deposits.

PURPOSE: Adult vitelliform lesions (AVL) are associated with age related macular degeneration (AMD) and subretinal drusenoid deposits (SRDD). We evaluated the natural course of AVL, assessing the influence of SRDD on disease progression, visual function and incidence of macular atrophy (MA) and choroidal neovascular membranes (CNVM). METHODS: A retrospective cohort study was conducted between January 2011 and March 2016. Demographic, clinical and imaging data from 26 consecutive AVL patients were analysed following case note review. Optical coherence tomography images were graded for SRDD and patients divided into those with/without SRDD. Outcomes included presenting/changes in best corrected visual acuity (BCVA) and incidence of MA/CNVM. RESULTS: Mean age was 78.6 ± 7.6 years. Mean follow-up was 51.5 ± 25.6 months. Twelve patients (46.2%) had SRDD at presentation with 3 more (11.5%) developing them. Subjects with SRDD were older (mean 81.7 ± 6.1 years vs 74.3 ± 7.6 years, p = 0.010). Mean presenting BCVA was worse in SRDD eyes (0.39 ± 0.31 logMAR vs 0.19 ± 0.18 logMAR, p = 0.017). Eight of 15 patients with SRDD (53.3%) developed incident MA or CNVM; higher than those with no SRDD (1/11, 9.1%; p = 0.036). Two patients (7.7%) developed full thickness macular holes. CONCLUSIONS: Patients with AVL and SRDD likely represent an advanced pathological stage or phenotype with worse visual outcome and higher risk of MA/CNVM. Possible overlap with AMD exists. Follow-up, counselling and provisions for early detection/treatment of complications should be made. Better classification including improved understanding of phenotypic and genetic variations with reference to comorbid diseases including AMD is required. Presence of SRDD in AVL offers a dichotomous classification, indicating risk of future MA/CNVM formation.

Pathogenicity of new BEST1 variants identified in Italian patients with best vitelliform macular dystrophy assessed by computational structural biology.

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.

NOVEL BEST1 MUTATIONS DETECTED BY NEXT-GENERATION SEQUENCING IN A CHINESE POPULATION WITH VITELLIFORM MACULAR DYSTROPHY.

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.