Multimodal imaging and genetic characteristics of autosomal recessive bestrophinopathy

PURPOSE

To report the ocular manifestations, multimodal imaging characteristics and genetic testing results of six patients with autosomal recessive bestrophinopathy (ARB).

METHODS

This was an observational case series including 12 eyes of 6 patients who were diagnosed with ARB. All patients underwent a complete ophthalmic examination including refraction, slit-lamp biomicroscopy, dilated fundus examination, fundus autofluorescence, optical coherence tomography and electrooculography. BEST1 gene sequencing was also performed for all patients.

RESULTS

The mean age was 22.8years and the male-female ratio was 0.50. All ARB patients had a hyperopic refractive error. A spectrum of fundus abnormalities, including multifocal yellowish subretinal deposits in the posterior pole, subfoveal accumulation of vitelliform material and cystoid macular edema, was observed. Fundus autofluorescence imaging demonstrated marked hyperautofluorescence corresponding to the yellowish subretinal deposits. Optical coherence tomography revealed serous retinal detachment, intraretinal cysts, brush border appearance caused by elongation of the outer segments of photoreceptors, and hyperreflective dome-shaped deposits at the level of the retinal pigment epithelium. Fundus fluorescein angiography showed hyperfluorescence with staining of the yellowish subretinal deposits. Electrooculography showed reduced Arden ratio in all patients. In addition, biallelic pathogenic variants in the BEST1 gene were detected in all patients.

CONCLUSION

ARB is a rare autosomal recessive inherited retinal disorder with biallelic pathogenic variants in the BEST1 gene and may present with a wide range of ocular abnormalities that may not be easily diagnosed. Multimodal retinal imaging in conjunction with EOG is helpful to establish the correct diagnosis.

The Retinal Phenotype Associated with the p.Pro101Thr BEST1 Variant

PURPOSE

To describe the retinal phenotype associated with the p.Pro101Thr BEST1 variant.

DESIGN

Retrospective, observational case series.

PARTICIPANTS

Patients diagnosed with bestrophinopathies in which molecular genetic testing identified the p.Pro101Thr BEST1 as well as healthy carriers among their first-degree relatives.

METHODS

Medical records were reviewed to obtain data on family history and ophthalmic examinations, including retinal imaging. The imaging protocol included OCT and fundus autofluorescence using Spectralis HRA + OCT (Heidelberg Engineering). Genetic analysis was performed by next-generation sequencing.

MAIN OUTCOME MEASURES

Results of ophthalmic examinations and multimodal imaging features of retinal phenotypes.

RESULTS

The c.301C>A, p.Pro101Thr BEST1 missense variant was identified as the causative variant in 8 individuals (all men) from 5 families, accounting for 13% of cases (8/61) and 10% of pathogenic alleles (9/93) in our cohort of patients affected by bestrophinopathies. Seven individuals (14 eyes) had the variant in heterozygous status: all eyes had a hyperopic refractive error (median spherical equivalent of + 3.75 diopters [D]) and 4 individuals had a macular dystrophy with mildly reduced visual acuity (median of 20/25 Snellen), whereas the other 3 were asymptomatic carriers. On multimodal retinal imaging, 5 (36%) out of 14 eyes had subclinical bestrophinopathy, 4 (29%) had typical findings of adult-onset foveomacular vitelliform dystrophy (AOFVD), and the remaining 5 (36%) displayed a pattern dystrophy-like phenotype. Follow-up data were available for 6 subjects, demonstrating clinical stability up to 11 years, in both subclinical and clinical forms. An additional patient with autosomal recessive bestrophinopathy was found to harbor the p.Pro101Thr variant in homozygosity.

CONCLUSIONS

The p.Pro101Thr BEST1 variant is likely a frequent cause of bestrophinopathy in the Italian population and can result in autosomal dominant macular dystrophies with incomplete penetrance and mild clinical manifestations as well as autosomal recessive bestrophinopathy. The spectrum of autosomal dominant maculopathy includes the typical AOFVD and a pattern dystrophy-like phenotype.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Macular neovascularization in inherited retinal diseases: A review

Inherited retinal diseases (IRDs) are the most common cause of blindness in working-age adults. Macular neovascularization (MNV) may be a presenting feature or occurs as a late-stage complication in several IRDs. We performed an extensive literature review on MNV associated with IRDs. MNV is a well-known complication of Sorsby fundus dystrophy and pseudoxanthoma elasticum. Those with late-onset Stargardt disease may masquerade as exudative age-related macular degeneration (AMD) when MNV is the presenting feature. Peripherinopathies may develop MNV that responds well to a short course of anti-vascular endothelial growth factor (anti-VEGF) therapy, while bestrophinopathies tend to develop MNV in the early stages of the disease without vision loss. Enhanced S-cone syndrome manifests type 3 MNV that typically regresses into a subfoveal fibrotic nodule. MNV is only a rare complication in choroideraemia and rod-cone dystrophies. Most IRD-related MNVs exhibit a favorable visual prognosis requiring less intensive regimens of anti-vascular endothelial growth factor therapy compared to age-related macular degeneration. We discuss the role of key imaging modalities in the diagnosis of MNV across a wide spectrum of IRDs and highlight the gaps in our knowledge with respect to the natural history and prognosis to pave the way for future directions of research.

Paradoxical autosomal recessive bestrophinopathy-like phenotypes shown in an autosomal dominant pedigree

PURPOSE

This study aimed to evaluate the clinical and genetic characteristics of eight members from a Chinese Han family who displayed autosomal recessive bestrophinopathy (ARB)-like retinal changes in autosomal dominant (AD) inheritance pattern.

METHODS

Clinical investigations included slit-lamp, tonometry, fundus photography, spectral-domain optical coherence tomography, fundus autofluorescence, electrooculography, and ultrasound biomicroscopy. Ocular axial length measurements were collected retrospectively. The targeted exome sequencing (TES) was applied for the genetic analysis of the proband. PCR-based Sanger sequencing was performed on the family for validation and co-segregation analysis.

RESULTS

Eight members in the three-generation pedigree complained about vision loss and seven of them had detailed clinical assessments, demonstrating ocular phenotypes including extramacular and vascular arcades subretinal deposits and Arden ratio decline on electrooculography that resembled ARB. Bilateral anterior chamber structure abnormalities were observed in seven cases and three patients were diagnosed with angle-closure glaucoma. Despite clinical phenotypes supporting ARB, there was only a single heterozygous mutation of c.227T > C (p.Ile76Thr) in the BEST1 gene detected in all eight patients, which showcased AD inheritance.

CONCLUSIONS

An ARB-like phenotype could be caused by a heterozygous mutation of the BEST1 gene and inherited in an AD fashion.

Prevalence of inherited retinal diseases in a large Egyptian cohort

BACKGROUND

Inherited retinal diseases form a rare, highly heterogeneous group of genetic disorders characterized by retinal degeneration. It is considered one of the leading causes of debilitating visual loss and blindness in children and young adults. Despite this few population-based data studies on prevalence of inherited retinal diseases exist. Moreover, prevalence can vary widely depending on geographical area, population ethnicity and cultural habits.

PURPOSE

To report the prevalence of different subtypes of Inherited retinal diseases in a large Egyptian cohort in a retrospective, hospital-based, cross-sectional study.

METHODS

We conducted an extensive electronic medical record search for all the patients attending the outpatient clinic and investigation unit of Ain Shams University Hospital and the two branches of Watany Eye Hospital in the period between January 2015 and October 2022 aiming to identify the prevalence rate of different types of IRDs, patient demographics and stratify them according to their phenotype.

RESULTS

We examined the electronic medical records of 478 222 patients, 971 patients were diagnosed with IRD by clinical examination with or without any of the following investigations: color fundus photography, fundus autofluorescence, fundus fluorescein angiography, optical coherence tomography and/or electrophysiological studies as electroretinogram, visual evoked potential and electrooculogram. The overall prevalence was 0.2%. The most common IRD encountered was isolated retinitis pigmentosa with a percentage of 78.9% followed by Stargardt disease at 6.3%, cone-rod dystrophy at 2.0%, autosomal recessive bestrophinopathy at 1.9% and unspecified IRD at 1.5%.

CONCLUSION

Retinitis pigmentosa was the most common IRD encountered followed by Stargardt disease. Many of the dystrophies are the subject of clinical intervention trials, and population-based epidemiological data can guide phenotype-based genetic testing and help assess the future need for treatment.

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.

A novel compound heterozygous BEST1 gene mutation in two siblings causing autosomal recessive bestrophinopathy

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.

Combination of Trabeculectomy and Primary Pars Plana Vitrectomy in the Successful Treatment of Angle-Closure Glaucoma with BEST1 Mutations: Self-Controlled Case Series

INTRODUCTION

This study aimed to illustrate the efficacy of the combination of lens extraction, trabeculectomy, and anterior vitrectomy in patients with secondary angle-closure glaucoma (ACG) with autosomal recessive bestrophinopathy or Best vitelliform macular dystrophy.

METHODS

This is a retrospective self-controlled case series study. Five patients undergoing a single trabeculectomy in one eye and triple surgery in the other eye were enrolled. All patients underwent a complete ophthalmic examination that included best-corrected visual acuity (BCVA), intraocular pressure (IOP), ultrasound biomicroscopy, and static gonioscopy. Multimodal fundus imaging was performed, including color fundus photography, fundus autofluorescence, and optical coherence tomography. Genetic testing was also analyzed.

RESULTS

 Among the 10 eyes, the mean IOP was 31.4 ± 4.7 mmHg before surgery. The mean axial length (AL) was 21.53 mm and the anterior chamber depth (ACD) was 2.31 mm. There were no statistically significant differences in preoperative IOP, BCVA, ACD, and AL between the two groups (all P > 0.05). The mean follow-up time was 64.0 months. All five eyes with a single trabeculectomy developed malignant glaucoma (MG). No complications were found in the other five eyes with triple surgery, and the anterior chamber was deepened and stable after surgery until the last visit. The mean IOP at the last visit was normalized to 16 mmHg without using any medications.

CONCLUSIONS

 Triple surgery is superior to single trabeculectomy for patients with ACG and BEST1 mutation, effectively bypassing MG complications. The vitreous may play a vital role in the mechanism of ACG in those patients and the high incidence of MG after filtering surgery.

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 and visual electrophysiological characteristics of vitelliform macular dystrophies in the first decade of life

Purpose:

To evaluate patterns of pediatric vitelliform macular dystrophy (PVMD).

Methods:

This is a retrospective analysis of Indian children with vitelliform macular dystrophy (VMD) presenting within the first decade of life. Records were evaluated for clinical findings, family screening, and investigative findings including optical coherence tomography (OCT), fundus autofluorescence (FAF), full-field electroretinogram (ERG) and electrooculogram (EOG). Electrophysiology was scrutinized and audited for acquisition and interpretation errors. Findings on follow-up were also recorded.

Results:

46 eyes of 24 patients were included. Mean age at presentation was 7.17 ± 2.17 years. Mean follow-up duration was 1.55 ± 1.69 years. Best disease was the commonest type of VMD detected (21 patients), while autosomal recessive bestrophinopathy was seen in three cases. Mean logMAR BCVA was 0.364 which decreased to 0.402 on follow-up. Hyperopia was noted in 29 out of 46 eyes (mean being +3.87 D, range ebing +0.75 to +8.75 D). Four eyes of four children had choroidal neovascular membrane at presentation, while another child developed while in follow-up. Solid type subretinal deposit was the commonest OCT finding (n = 29/38) and central hyper FAF was the commonest pattern (n = 18/32). EOG was available for review in 32 eyes, but was unreliable in 11 eyes. Seven eyes demonstrated complete absence of light rise on EOG.

Conclusion:

PVMD can present in advanced forms. Progression to complications with loss of visual acuity can happen within the first decade of life. EOG shows grossly suppressed waveforms in the light phase in a large number of such children.

Branch retina vein occlusion combined with angle-closure glaucoma is associated with a mutation in BEST1: a case report

BACKGROUND

It is rare for a patient to be diagnosed with branch retina vein occlusion (BRVO), angle-closure glaucoma (ACG) and autosomal recessive bestrophinopathy (ARB). ARB is strongly associated with ACG. Although glaucoma is a significant risk factor for RVO, there is a plausible relationship between ACG and BRVO. To discuss correlation of these diseases is necessary.

CASE PRESENTATION

The genetic testing and medical treatment of a patient with ocular fundus diseases and ACG were recorded. We present a 47-year-old male patient with BRVO who was diagnosed with angle-closure glaucoma and a homozygous mutation of c.140G > A (p.R47H) in BEST1. Intravitreal ranibizumab was administered in combination with three antiglaucomatous eyedrops to lower intraocular pressure (IOP) in the right eye. One month later, BCVA improved to 0.3. IOP was controlled at 13 mmHg.

CONCLUSIONS

ACG was likely combined to ARB, while there's a plausible relationship between ACG and BRVO.

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.

Autosomal Recessive Bestrophinopathy: Clinical Features, Natural History, and Genetic Findings in Preparation for Clinical Trials

Purpose

To investigate the clinical course, genetic findings, and phenotypic spectrum of autosomal recessive bestrophinopathy (ARB) in a large cohort of children and adults.

Design

Retrospective case series.

Participants

Patients with a detailed clinical phenotype consistent with ARB, biallelic likely disease-causing sequence variants in the BEST1 gene, or both identified at a single tertiary referral center.

Methods

Review of case notes, retinal imaging (color fundus photography, fundus autofluorescence, OCT), electrophysiologic assessment, and molecular genetic testing.

Main Outcome Measures

Visual acuity (VA), retinal imaging, and electrophysiologic changes over time.

Results

Fifty-six eyes of 28 unrelated patients were included. Compound heterozygous variants were detected in most patients (19/27), with 6 alleles recurring in apparently unrelated individuals, the most common of which was c.422G→A, p.(Arg141His; n = 4 patients). Mean presenting VA was 0.52 ± 0.36 logarithm of the minimum angle of resolution (logMAR), and final VA was 0.81 ± 0.75 logMAR (P = 0.06). The mean rate of change in VA was 0.05 ± 0.13 logMAR/year. A significant change in VA was detected in patients with a follow-up of 5 years or more (n = 18) compared with patients with a follow-up of 5 years or less (n = 10; P = 0.001). Presence of subretinal fluid and vitelliform material were early findings in most patients, and this did not change substantially over time. A reduction in central retinal thickness was detected in most eyes (80.4%) over the course of follow-up. Many patients (10/26) showed evidence of generalized rod and cone system dysfunction. These patients were older (P < 0.001) and had worse VA (P = 0.02) than those with normal full-field electroretinography results.

Conclusions

Although patients with ARB are presumed to have no functioning bestrophin channels, significant phenotypic heterogeneity is evident. The clinical course is characterized by a progressive loss of vision with a slow rate of decline, providing a wide therapeutic window for anticipated future treatment strategies.

Pathogenic role of the vitreous in angle-closure glaucoma with autosomal recessive bestrophinopathy: a case report

Background

Autosomal recessive bestrophinopathy (ARB) is caused by homozygous or compound heterozygous mutations in the BEST1 gene and always accompanied with refractory angle-closure glaucoma (ACG). The exact mechanism for the pan-ocular abnormalities in ARB is still unknown and the management of ACG in these cases is challenging.

Case presentation

A 26-year-old patient with a novel autosomal–recessively inherited c.1 A > G variant in BEST1 diagnosed as ARB and ACG, presented as widespread vitelliform deposits in the posterior pole, retinoschisis in the macula, vitreoretinal interface abnormalities, shallow anterior chamber depth (ACD) and angle closure with uncontrolled intraocular pressure (IOP). Combined phacoemulsification, intraocular lens implantation and goniosynechialysis did not improve any clinical presentation. However, low dose transscleral cyclophotocoagulation with subsequent vitreous liquefaction effectively lowered IOP, deepened ACD, and rehabilitated retinoschisis in both eyes.

Conclusions

This case implied vitreous condition may play a pathogenic role in formation of retinoschisis and ACG in the patients with ARB. Treatments that induce vitreous liquefaction could be used to treat young ACG patients with ARB or other kinds of ACG to avoid vision-threatening post-operative complications.

Familial autosomal recessive bestrophinopathy: identification of a novel variant in BEST1 gene and the specific metabolomic profile

BACKGROUND

Autosomal recessive bestrophinopathy (ARB) is a retinal degenerative disorder caused by BEST1 mutations with autosomal recessive inheritance. We aim to map a comprehensive genomic and metabolomic profile of a consanguineous Chinese family with ARB.

METHODS

Ophthalmic examinations were performed on the affected patients with ARB. The proband was screened for potential causative mutations in a panel with 256 known retinal disease genes by using target capture sequencing. The related mutation was further validated and segregated in the family members by Sanger sequencing. In silico prediction tools were used for pathogenicity assessment. A UHPLC-MS/MS metabolomic analysis was performed to explore the disease-associated metabolic feature.

RESULTS

The affected patients from this family were characterized by low vision, the presence of subretinal fluid, macular edema, and hyperopia with coincidental angle closure. DNA sequencing identified a novel missense mutation in the BEST1 gene c.646G > A (p.Val216Ile) of the proband. Sanger sequencing further confirmed the mutation. The missense mutation was co-segregation across the pedigree and predicted to be deleterious by SIFT (0.017). The blood metabolic profiles were highly similar among all family members probably because of the same lifestyle, habitat and genomic background. However, ARB patients presented a significant deregulation of metabolites, such as citric acid, L-Threonic acid, and eicosapentaenoic acid.

CONCLUSIONS

We identified a novel disease-associated variant in the BEST1 gene as well as a disease-specific metabolic feature in familial ARB. Our findings helped improve the understanding of ARB mechanisms.

Restoration of mutant bestrophin-1 expression, localisation and function in a polarised epithelial cell model

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.

Detailed analysis of family with autosomal recessive bestrophinopathy associated with new BEST1 mutation

Purpose

To describe the clinical and genetic findings in a patient with autosomal recessive bestrophinopathy (ARB) and his healthy parents.

Methods

The patient and his healthy non-consanguineous parents underwent detailed ophthalmic evaluations including electro-oculography (EOG), spectral-domain optical coherence tomography (SD-OCT), and fundus autofluorescence (FAF) imaging. Mutation analysis of the BEST1 gene was performed by Sanger sequencing.

Results

The FAF images showed multiple spots of increased autofluorescence, and the sites of these spots corresponded to the yellowish deposits detected by ophthalmoscopy. SD-OCT showed cystoid macular changes and a shallow serous macular detachment. The Arden ratio of the EOG was markedly reduced to 1.1 in both eyes. Genetic analysis of the proband detected two sequence variants of the BEST1 gene in the heterozygous state: a novel variant c.717delG, p.V239VfsX2 and an already described c.763C>T, p.R255W variant associated with Best vitelliform macular dystrophy and ARB. The proband’s father carried the c.717delG, p.V239VfsX2 variant in the heterozygous state, and the mother carried the c.763C>T, p.R255W variant in the heterozygous state. The parents who were heterozygous for the BEST1 variants had normal visual acuity, EOG, SD-OCT, and FAF images.

Conclusions

In a truncating BEST1 mutation, the phenotype associated with ARB is most likely due to a marked decrease in the expression of BEST1 promoted by the nonsense-mediated decay surveillance mechanism, and it may depend on the position of the premature termination of the codon created.