Antisense Oligonucleotide-Based Rescue of Complex Intronic Splicing Defects in ABCA4.

The ABCA4 gene, involved in Stargardt disease, has a high percentage of splice-altering pathogenic variants, some of which cause complex RNA defects. Although antisense oligonucleotides (AONs) have shown promising results in splicing modulation, they have not yet been used to target complex splicing defects. Here, we performed AON-based rescue studies on ABCA4 complex splicing defects. Intron 13 variants c.1938-724A>G, c.1938-621G>A, c.1938-619A>G, and c.1938-514A>G all lead to the inclusion of different pseudo-exons (PEs) with and without an upstream PE (PE1). Intron 44 variant c.6148-84A>T results in multiple PE inclusions and/or exon skipping events. Five novel AONs were designed to target these defects. AON efficacy was assessed by in vitro splice assays using midigenes containing the variants of interest. All screened complex splicing defects were effectively rescued by the AONs. Although varying levels of efficacy were observed between AONs targeting the same PEs, for all variants at least one AON restored splicing to levels comparable or better than wildtype. In conclusion, AONs are a promising approach to target complex splicing defects in ABCA4.

Preclinical Development of Antisense Oligonucleotides to Rescue Aberrant Splicing Caused by an Ultrarare ABCA4 Variant in a Child with Early-Onset Stargardt Disease.

Precision medicine is rapidly gaining recognition in the field of (ultra)rare conditions, where only a few individuals in the world are affected. Clinical trial design for a small number of patients is extremely challenging, and for this reason, the development of N-of-1 strategies is explored to accelerate customized therapy design for rare cases. A strong candidate for this approach is Stargardt disease (STGD1), an autosomal recessive macular degeneration characterized by high genetic and phenotypic heterogeneity. STGD1 is caused by pathogenic variants in ABCA4, and amongst them, several deep-intronic variants alter the pre-mRNA splicing process, generally resulting in the insertion of pseudoexons (PEs) into the final transcript. In this study, we describe a 10-year-old girl harboring the unique deep-intronic ABCA4 variant c.6817-713A>G. Clinically, she presents with typical early-onset STGD1 with a high disease symmetry between her two eyes. Molecularly, we designed antisense oligonucleotides (AONs) to block the produced PE insertion. Splicing rescue was assessed in three different in vitro models: HEK293T cells, fibroblasts, and photoreceptor precursor cells, the last two being derived from the patient. Overall, our research is intended to serve as the basis for a personalized N-of-1 AON-based treatment to stop early vision loss in this patient.

Nationwide epidemiologic survey on incidence of macular dystrophy in Japan.

PURPOSE: The aim of this study was to estimate the number of patients in Japan who had visited an ophthalmologist for macular dystrophy of various types, including Best vitelliform macular dystrophy (BVMD), Stargardt disease, occult macular dystrophy (OMD), cone (-rod) dystrophy, X-linked retinoschisis (XLRS), and central areolar choroid dystrophy (CACD). STUDY DESIGN: Nationwide epidemiologic survey METHODS: Questionnaires were distributed to 965 major facilities, including all the university hospitals in Japan. The aim of the questionnaire was to determine the number of patients with each type of macular dystrophy who had visited an outpatient clinic during the past 5 years (January 2015 to December 2019). RESULTS: Over 70% of the patients were diagnosed and followed up at university hospitals. The estimated annual number of newly diagnosed cases was as follows: 55.3 for BVMD, 36.7 for Stargardt disease, 35.8 for OMD, 160.6 for cone (-rod) dystrophy, 31.0 for XLRS, 29.8 for CACD, and 174.1 for other types of macular dystrophy. The total number of patients with macular dystrophy diagnosed and followed at major institutions was estimated to be 6651. CONCLUSION: This was the first nationwide survey of macular dystrophy in Japan and provided an approximate number of affected patients. The diagnosis of macular dystrophy is primarily carried out at facilities with affiliated specialists, such as university hospitals. By examining the incidence of multiple diseases simultaneously, we were able to compare the incidence of each type of macular dystrophy.

A Proximity Complementation Assay to Identify Small Molecules That Enhance the Traffic of ABCA4 Misfolding Variants.

ABCA4-related retinopathy is the most common inherited Mendelian eye disorder worldwide, caused by biallelic variants in the ATP-binding cassette transporter ABCA4. To date, over 2200 ABCA4 variants have been identified, including missense, nonsense, indels, splice site and deep intronic defects. Notably, more than 60% are missense variants that can lead to protein misfolding, mistrafficking and degradation. Currently no approved therapies target ABCA4. In this study, we demonstrate that ABCA4 misfolding variants are temperature-sensitive and reduced temperature growth (30 °C) improves their traffic to the plasma membrane, suggesting the folding of these variants could be rescuable. Consequently, an in vitro platform was developed for the rapid and robust detection of ABCA4 traffic to the plasma membrane in transiently transfected cells. The system was used to assess selected candidate small molecules that were reported to improve the folding or traffic of other ABC transporters. Two candidates, 4-PBA and AICAR, were identified and validated for their ability to enhance both wild-type ABCA4 and variant trafficking to the cell surface in cell culture. We envision that this platform could serve as a primary screen for more sophisticated in vitro testing, enabling the discovery of breakthrough agents to rescue ABCA4 protein defects and mitigate ABCA4-related retinopathy.

Intravitreal Delivery of PEGylated-ECO Plasmid DNA Nanoparticles for Gene Therapy of Stargardt Disease.

OBJECTIVE: Current gene therapy of inherited retinal diseases is achieved mainly by subretinal injection, which is invasive with severe adverse effects. Intravitreal injection is a minimally invasive alternative for gene therapy of inherited retinal diseases. This work explores the efficacy of intravitreal delivery of PEGylated ECO (a multifunctional pH-sensitive amphiphilic amino lipid) plasmid DNA (pGRK1-ABCA4-S/MAR) nanoparticles (PEG-ELNP) for gene therapy of Stargardt disease. METHODS: Pigmented Abca4-/- knockout mice received 1 µL of PEG-ELNP solution (200 ng/uL, pDNA concentration) by intravitreal injections at an interval of 1.5 months. The expression of ABCA4 in the retina was determined by RT-PCR and immunohistochemistry at 6 months after the second injection. A2E levels in the treated eyes and untreated controls were determined by HPLC. The safety of treatment was monitored by scanning laser ophthalmoscopy and electroretinogram (ERG). RESULTS: PEG-ELNP resulted in significant ABCA4 expression at both mRNA level and protein level at]6 months after 2 intravitreal injections, and a 40% A2E accumulation reduction compared with non-treated controls. The PEG-ELNP also demonstrated excellent safety as shown by scanning laser ophthalmoscopy, and the eye function evaluation from electroretinogram. CONCLUSIONS: Intravitreal delivery of the PEG-ELNP of pGRK1-ABCA4-S/MAR is a promising approach for gene therapy of Stargardt Disease, which can also be a delivery platform for gene therapy of other inherited retinal diseases.

Understanding and Rescuing the Splicing Defect Caused by the Frequent ABCA4 Variant c.4253+43G>A Underlying Stargardt Disease.

Pathogenic variants in ABCA4 are the underlying molecular cause of Stargardt disease (STGD1), an autosomal recessive macular dystrophy characterized by a progressive loss of central vision. Among intronic ABCA4 variants, c.4253+43G>A is frequently detected in STGD1 cases and is classified as a hypomorphic allele, generally associated with late-onset cases. This variant was previously reported to alter splicing regulatory sequences, but the splicing outcome is not fully understood yet. In this study, we attempted to better understand its effect on splicing and to rescue the aberrant splicing via antisense oligonucleotides (AONs). Wild-type and c.4253+43G>A variant-harboring maxigene vectors revealed additional skipping events, which were not previously detected upon transfection in HEK293T cells. To restore exon inclusion, we designed a set of 27 AONs targeting either splicing silencer motifs or the variant region and screened these in maxigene-transfected HEK293T cells. Candidate AONs able to promote exon inclusion were selected for further testing in patient-derived photoreceptor precursor cells. Surprisingly, no robust splicing modulation was observed in this model system. Overall, this research helped to adequately characterize the splicing alteration caused by the c.4253+43G>A variant, although future development of AON-mediated exon inclusion therapy for ABCA4 is needed.

ABCA4 variant screening in a Turkish cohort with Stargardt disease.

PURPOSE: This study aims to evaluate the ABCA4 variants in patients diagnosed with Stargardt disease. METHODS: This is a retrospective study designed to investigate variants in the ABCA4 in Stargardt disease and the clinical findings of the cases. Sex, age, age of onset of symptoms, best-corrected visual acuity, color fundus photography, optical coherence tomography, and visual field test of the patients were recorded. Genetic analyses were screened, and patients with at least two variants in the ABCA4 were included in this study. RESULTS: Twenty-seven patients diagnosed with Stargardt disease with the ABCA4 variants were included in this study. Twelve of them (44.4%) were female and fifteen (55.5%) were male. The mean age of the cases was 27.44 years (ranging from 8 to 56 years). Thirty different variants were detected in 54 ABCA4 alleles of 27 patients. The two most common pathogenic variants were c.5882 G>A p.(Gly1961Glu) and c.52C>T p.(Arg18Trp) in this cohort. Two novel variants were identified (c.3855_3856dup, c.1554 + 3_1554 + 4del) and the patient with the c.1554 + 3_1554 + 4del variant additionally had a different ABCA4 variant in trans. The other novel variant was homozygous. CONCLUSIONS: In this study, two novel variants were described in a Turkish cohort with Stargardt disease. The variant c.52C>T p.(Arg18Trp) was the most common disease-causing variant besides the c.5882 G>A p.(Gly1961Glu) which was identified frequently in the previous studies. A larger sample size is necessary for describing different pathogenic variants and understanding the phenotype-genotype correlations.

Identifying variants and their pathogenicity in inherited diseases is important for widening the disease-causing mutations and future treatment options.Two novel variants (c.3855_3856dup, c.5910_5912dup) were described in a cohort with Stargardt disease.The most common variants could be different in ethnic groups.The variant c.52C>T p.(Arg18Trp) was the most common variant besides the c.5882G>A p.(Gly1961Glu) which was frequently identified in the previous studies.Describing different pathogenic variants and clinical findings of the patients is important for understanding the phenotype-genotype correlations.

A Retrospective Longitudinal Study of 460 Patients with ABCA4-Associated Retinal Disease.

PURPOSE: To investigate the distribution of genotypes and natural history of ABCA4-associated retinal disease in a large cohort of patients seen at a single institution. DESIGN: Retrospective, single-institution cohort review. PARTICIPANTS: Patients seen at the University of Iowa between November 1986 and August 2022 clinically suspected to have disease caused by sequence variations in ABCA4. METHODS: DNA samples from participants were subjected to a tiered testing strategy progressing from allele-specific screening to whole genome sequencing. Charts were reviewed, and clinical data were tabulated. The pathogenic severity of the most common alleles was estimated by studying groups of patients who shared 1 allele. Groups of patients with shared genotypes were reviewed for evidence of modifying factor effects. MAIN OUTCOME MEASURES: Age at first uncorrectable vision loss, best-corrected visual acuity, and the area of the I2e isopter of the Goldmann visual field. RESULTS: A total of 460 patients from 390 families demonstrated convincing clinical features of ABCA4-associated retinal disease. Complete genotypes were identified in 399 patients, and partial genotypes were identified in 61. The median age at first vision loss was 16 years (range, 4-76 years). Two hundred sixty-five families (68%) harbored a unique genotype, and no more than 10 patients shared any single genotype. Review of the patients with shared genotypes revealed evidence of modifying factors that in several cases resulted in a > 15-year difference in age at first vision loss. Two hundred forty-one different alleles were identified among the members of this cohort, and 161 of these (67%) were found in only a single individual. CONCLUSIONS: ABCA4-associated retinal disease ranges from a very severe photoreceptor disease with an onset before 5 years of age to a late-onset retinal pigment epithelium-based condition resembling pattern dystrophy. Modifying factors frequently impact the ABCA4 disease phenotype to a degree that is similar in magnitude to the detectable ABCA4 alleles themselves. It is likely that most patients in any cohort will harbor a unique genotype. The latter observations taken together suggest that patients' clinical findings in most cases will be more useful for predicting their clinical course than their genotype. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Inner retinal thickness in Stargardt disease.

PURPOSE: To analyze the alterations at the level of the inner retina in patients affected by Stargardt disease (STGD1). METHODS: Cross-sectional investigation involving STGD1 patients with genetically confirmed diagnosis, who underwent optical coherence tomography (OCT), optical coherence tomography angiography (OCTA), and microperimetry. RESULTS: Overall, 31 patients (62 eyes) with genetically confirmed STGD1 were included in the study. Mean inner retinal thickness, vessel density of plexa, and retinal sensitivity resulted significantly reduced in STGD patients, compared with healthy controls (p < 0.05), both in the outer and in the inner ETDRS rings. Overall, 43% of eyes revealed an inner retinal thinning, whereas 21% and 35% showed a thicker or within normal range inner retina. CONCLUSIONS: Inner retina is irregularly altered in STGD1, showing variable quantitative alterations as detected on OCT. Inner retinal status might represent a useful biomarker to better characterize STGD1 and to ascertain the effects of new treatment approaches.

Phenotyping and genotyping inherited retinal diseases: Molecular genetics, clinical and imaging features, and therapeutics of macular dystrophies, cone and cone-rod dystrophies, rod-cone dystrophies, Leber congenital amaurosis, and cone dysfunction syndromes.

Inherited retinal diseases (IRD) are a leading cause of blindness in the working age population and in children. The scope of this review is to familiarise clinicians and scientists with the current landscape of molecular genetics, clinical phenotype, retinal imaging and therapeutic prospects/completed trials in IRD. Herein we present in a comprehensive and concise manner: (i) macular dystrophies (Stargardt disease (ABCA4), X-linked retinoschisis (RS1), Best disease (BEST1), PRPH2-associated pattern dystrophy, Sorsby fundus dystrophy (TIMP3), and autosomal dominant drusen (EFEMP1)), (ii) cone and cone-rod dystrophies (GUCA1A, PRPH2, ABCA4, KCNV2 and RPGR), (iii) predominant rod or rod-cone dystrophies (retinitis pigmentosa, enhanced S-Cone syndrome (NR2E3), Bietti crystalline corneoretinal dystrophy (CYP4V2)), (iv) Leber congenital amaurosis/early-onset severe retinal dystrophy (GUCY2D, CEP290, CRB1, RDH12, RPE65, TULP1, AIPL1 and NMNAT1), (v) cone dysfunction syndromes (achromatopsia (CNGA3, CNGB3, PDE6C, PDE6H, GNAT2, ATF6), X-linked cone dysfunction with myopia and dichromacy (Bornholm Eye disease; OPN1LW/OPN1MW array), oligocone trichromacy, and blue-cone monochromatism (OPN1LW/OPN1MW array)). Whilst we use the aforementioned classical phenotypic groupings, a key feature of IRD is that it is characterised by tremendous heterogeneity and variable expressivity, with several of the above genes associated with a range of phenotypes.

Proof-of-concept for multiple AON delivery by a single U7snRNA vector to restore splicing defects in ABCA4.

The high allelic heterogeneity in Stargardt disease (STGD1) complicates the design of intervention strategies. A significant proportion of pathogenic intronic ABCA4 variants alters the pre-mRNA splicing process. Antisense oligonucleotides (AONs) are an attractive yet mutation-specific therapeutic strategy to restore these splicing defects. In this study, we experimentally assessed the potential of a splicing modulation therapy to target multiple intronic ABCA4 variants. AONs were inserted into U7snRNA gene cassettes and tested in midigene-based splice assays. Five potent antisense sequences were selected to generate a multiple U7snRNA cassette construct, and this combination vector showed substantial rescue of all of the splicing defects. Therefore, the combination cassette was used for viral synthesis and assessment in patient-derived photoreceptor precursor cells (PPCs). Simultaneous delivery of several modified U7snRNAs through a single AAV, however, did not show substantial splicing correction, probably due to suboptimal transduction efficiency in PPCs and/or a heterogeneous viral population containing incomplete AAV genomes. Overall, these data demonstrate the potential of the U7snRNA system to rescue multiple splicing defects, but also suggest that AAV-associated challenges are still a limiting step, underscoring the need for further optimization before implementing this strategy as a potential treatment for STGD1.

Study of Late-Onset Stargardt Type 1 Disease: Characteristics, Genetics, and Progression.

PURPOSE: Late-onset Stargardt disease is a subtype of Stargardt disease type 1 (STGD1), defined by an age of onset of 45 years or older. We describe the disease characteristics, underlying genetics, and disease progression of late-onset STGD1 and highlight the differences from geographic atrophy. DESIGN: Retrospective cohort study. PARTICIPANTS: Seventy-one patients with late-onset STGD1. METHODS: Medical files were reviewed for clinical data including age at onset, initial symptoms, and best-corrected visual acuity. A quantitative and qualitative assessment of retinal pigment epithelium (RPE) atrophy was performed on fundus autofluorescence images and OCT scans. MAIN OUTCOME MEASURES: Age at onset, genotype, visual acuity, atrophy growth rates, and loss of external limiting membrane, ellipsoid zone, and RPE. RESULTS: Median age at onset was 55.0 years (range, 45-82 years). A combination of a mild and severe variant in ATP-binding cassette subfamily A member 4 (ABCA4) was the most common genotype (n = 49 [69.0%]). The most frequent allele, c.5603A→T (p.Asn1868Ile), was present in 43 of 71 patients (60.6%). No combination of 2 severe variants was found. At first presentation, all patients have flecks. Foveal-sparing atrophy was present in 33.3% of eyes, whereas 21.1% had atrophy with foveal involvement. Extrafoveal atrophy was present in 38.9% of eyes, and no atrophy was evident in 6.7% of eyes. Time-to-event curves showed a median duration of 15.4 years (95% confidence interval, 11.1-19.6 years) from onset to foveal involvement. The median visual acuity decline was -0.03 Snellen decimal per year (interquartile range [IQR], -0.07 to 0.00 Snellen decimal; 0.03 logarithm of the minimum angle of resolution). Median atrophy growth was 0.590 mm2/year (IQR, 0.046-1.641 mm2/year) for definitely decreased autofluorescence and 0.650 mm2/year (IQR, 0.299-1.729 mm2/year) for total decreased autofluorescence. CONCLUSIONS: Late-onset STGD1 is a subtype of STGD1 with most commonly 1 severe and 1 mild ABCA4 variant. The general patient presents with typical fundus flecks and retinal atrophy in a foveal-sparing pattern with preserved central vision. Misdiagnosis as age-related macular degeneration should be avoided to prevent futile invasive treatments with potential complications. In addition, correct diagnosis lends patients with late-onset STGD1 the opportunity to participate in potentially beneficial therapeutic trials for STGD1. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Analysis of the Outer Retinal Bands in ABCA4 and PRPH2-Associated Retinopathy using OCT.

PURPOSE: To evaluate the outer retinal bands using OCT in ABCA4- and PRPH2-associated retinopathy and develop a novel imaging biomarker to differentiate between these 2 genotypes. DESIGN: Multicenter case-control study. PARTICIPANTS: Patients with a clinical and genetic diagnosis of ABCA4- or PRPH2-associated retinopathy and an age-matched control group. METHODS: Macular OCT was used to measure the thickness of the outer retinal bands 2 and 4 by 2 independent examiners at 4 retinal loci. MAIN OUTCOME MEASURES: Outcome measures included the thicknesses of band 2, band 4, and the band 2/band 4 ratio. Linear mixed modeling was used to make comparisons across the 3 groups. Receiver operating characteristic (ROC) analysis determined the optimal cutoff for the band 2/band 4 ratio to distinguish PRPH2- from ABCA4-associated retinopathy. RESULTS: We included 45 patients with ABCA4 variants, 45 patients with PRPH2 variants, and 45 healthy controls. Band 2 was significantly thicker in patients with PRPH2 compared with ABCA4 (21.4 vs. 15.9 µm, P < 0.001) variants, whereas band 4 was thicker in patients with ABCA4 variants than those with PRPH2 variants (27.5 vs. 21.7 µm, P < 0.001). Similarly, the band 2/band 4 ratio was significantly different (1.0 vs. 0.6 for PRPH2 vs. ABCA4, P < 0.001). The area under the ROC curve was 0.87 for either band 2 (> 18.58 µm) or band 4 (< 26.17 µm) alone and 0.99 (95% confidence interval: 0.97-0.99) for the band 2/band 4 ratio with a cutoff threshold of 0.79, providing 100% specificity. CONCLUSIONS: We report an altered outer retinal band profile whereby the band 2/band 4 ratio was able to discriminate between PRPH2- and ABCA4-associated retinopathy. This may have future clinic utility in predicting the genotype and provide further insight into the anatomic correlate of band 2. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

PRPH2 mutation c.582-1G>A causing adult-onset macular dystrophy with a benign concentric annular macular dystrophy phenotype in a family / Mutação c.582-1G>A do gene PRPH2 causando distrofia macular de início adulto com fenótipo de distrofia macular anular concêntrica benigna em uma família

ABSTRACT The peripherin gene (PRPH2) mutation is associated with photoreceptor cell dysfunction as well as in several inherited retinal dystrophies. The PRPH2 mutation c.582-1G>A is a rare variant reported in retinitis pigmentosa and pattern dystrophy. Here Case 1 was of a 54-year-old woman with bilateral atrophy of the perifoveal retinal pigmentary epithelium and choriocapillaris with central foveolar respect. Autofluorescence and fluorescein angiography revealed perifoveal atrophy of the retinal pigmentary epithelium with an annular window effect without the "dark choroid" sign. Case 2 (mother of Case 1) presented with extensive atrophy of the retinal pigmentary epithelium and choriocapillaris. PRPH2 was evaluated and the c.582-1G>A mutation was identified in heterozygosity. An advanced adult-onset benign concentric annular macular dystrophy diagnosis was thereby proposed. The c.582-1G>A mutation is poorly known and not present in all common genomic databases. This case report is the first one to report a c.582-1G>A mutation associated with benign concentric annular macular dystrophy.

RESUMO Mutações do gene da periferina (PRPH2) estão associadas à disfunção das células fotorreceptoras e estão envolvidas em várias distrofias retinianas hereditárias. A mutação c.582-1G>A do gene PRPH2 é uma variante rara, relatada na retinite pigmentosa e nas distrofias em padrão. O caso 1 foi de uma mulher de 54 anos com atrofia bilateral do epitélio pigmentar da retina perifoveal e da coriocapilar, com acometimento foveolar central. A autofluorescência e a angiofluoresceinografia revelaram atrofia perifoveal do epitélio pigmentar da retina, com efeito de janela anular, sem o sinal da "coroide escura". O caso 2 (mãe) apresentava extensa atrofia do epitélio pigmentar da retina e da coriocapilar. Foi feito um estudo do gene PRPH2, que identificou a mutação c.582-1G>A em heterozigose. Foi proposto um diagnóstico de distrofia macular anular concêntrica benigna de início adulto em estágio avançado. A mutação c.582-1G>A é pouco conhecida e não está presente em todos os bancos de dados genômicos usuais. Este é o primeiro relato de caso publicado de uma mutação c.582-1G>A associada à distrofia macular anular concêntrica benigna.

Macular dystrophies associated with Stargardt-like phenotypes / Distrofias maculares associadas a fenótipos Stargardt-like

ABSTRACT Purpose: Stargardt-like phenotype has been described as associated with pathogenic variants besides the ABCA4 gene. This study aimed to describe four cases with retinal appearance of Stargardt disease phenotypes and unexpected molecular findings. Methods: This report reviewed medical records of four patients with macular dystrophy and clinical features of Stargardt disease. Ophthalmic examination, fundus imaging, and next-generation sequencing were performed to evaluate pathogenic variants related to the phenotypes. Results: Patients presented macular atrophy and pigmentary changes suggesting Stargardt disease. The phenotypes of the two patients were associated with autosomal dominant inheritance pattern genes (RIMS1 and CRX) and in the other two patients were associated with recessive dominant inheritance pattern genes (CRB1 and RDH12) with variants predicted to be pathogenic. Conclusion: Macular dystrophies may have phenotypic similarities to Stargardt-like phenotype associated with other genes besides the classic ones.

RESUMO Objetivo: Fenótipos Stargardt-like já foram asso-ciados a variantes patogênicas no gene ABCA4. O propósito desse estudo é descrever quatro pacientes com achados retinianos semelhantes a doença de Stargardt com resultados moleculares diferentes do esperado. Métodos: Esse relato fez a revisão de prontuários médicos de quatro pacientes com distrofia macular e achados clínicos sugestivos de doença de Stargardt. Foram realizados avaliação oftalmológica, exames de imagens e testes usando next generation sequencing para avaliar variantes patogênicas associadas aos fenótipos dos pacientes. Resultados: Os pacientes apresentavam atrofia macular e alterações pigmentares sugerindo achados clínicos de doença de Stargardt. Dois pacientes foram associados a genes com herança autossômica dominante (RIMS1 e CRX) e dois pacientes foram associados a genes com herança autossômica recessiva (CRB1 e RDH12) com variantes preditoras de serem patogênicas. Conclusão: Distrofias maculares podem ter similaridades fenotípicas com fenótipo de Stargardt-like associados a outros genes além dos classicamente já descritos.

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.

At-Home Trial of Four Different Head-Mounted Displays in Visual Rehabilitation of People with Stargardt Disease.

Purpose: To examine the potential of different head-mounted displays in the rehabilitation of individuals with visual impairment. Methods: This prospective explorative study conducted between September 2019 and August 2020 included participants with Stargardt disease with moderate to severe visual impairment and a relatively preserved peripheral visual field. AceSight, eSight 3, IrisVision Live, and Jordy were tested. After instruction and training, participants chose two head-mounted displays for home use for two weeks per device. The Canadian Occupational Performance Measure was used for evaluation. Results: Twelve participants (aged 16-53 years) tested all head-mounted displays in the clinic. Distance visual acuity and reading distance improved with all head-mounted displays and eSight and Irisvision improved near visual acuity. Six participants decided not to test the head-mounted display at home due to lack of time or energy, dizziness and discomfort, double vision and peripheral visual field limitation, or aesthetics. After home use, the participants reported improved visual function at a distance with IrisVision, AceSight, and e-Sight, whereas only AceSight improved vision during near tasks. IrisVision and eSight improved reading ability, and none of the devices improved vision during tasks involving computers. Five participants used the devices sparingly, and five avoided public use owing to aesthetics. Conclusion: We found an improvement in distance visual acuity and increased reading distance for all tested head-mounted displays. Additionally, IrisVision and eSight improved visual function at near and eSight also improved contrast vision at distance. Despite the possibility of improving vision, social stigma and device aesthetics kept the participants from using head-mounted displays in public and limited their use at home.

Diagnostic Challenges in ABCA4-Associated Retinal Degeneration: One Gene, Many Phenotypes.

(1) Purpose: ABCA4-associated retinal degeneration (ABCA4-RD) is a phenotypically diverse disease that often evades diagnosis, even by experienced retinal specialists. This may lead to inappropriate management, delayed genetic testing, or inaccurate interpretation of genetic testing results. Here, we illustrate the phenotypic diversity of ABCA4-RD using a series of representative cases and compare these to other conditions that closely mimic ABCA4-RD. (2) Methods: Genetically confirmed ABCA4-RD cases with representative phenotypes were selected from an inherited retinal disease cohort in Singapore and compared to phenocopies involving other retinal diseases. (3) Results: ABCA4-RD phenotypes in this series included typical adolescent-onset Stargardt disease with flecks, bull's eye maculopathy without flecks, fundus flavimaculatus, late-onset Stargardt disease, and severe early-onset Stargardt disease. Phenocopies of ABCA4-RD in this series included macular dystrophy, pattern dystrophy, cone dystrophy, advanced retinitis pigmentosa, Leber congenital amaurosis, drug toxicity, and age-related macular degeneration. Key distinguishing features that often suggested a diagnosis of ABCA4-RD were the presence of peripapillary sparing, macular involvement and centrifugal distribution, and a recessive pedigree. (4) Conclusions: ABCA4-RD demonstrates a remarkable phenotypic spectrum that makes diagnosis challenging. Awareness of the clinical spectrum of disease can facilitate prompt recognition and accurate diagnostic testing.

Distinct mouse models of Stargardt disease display differences in pharmacological targeting of ceramides and inflammatory responses.

Mutations in many visual cycle enzymes in photoreceptors and retinal pigment epithelium (RPE) cells can lead to the chronic accumulation of toxic retinoid byproducts, which poison photoreceptors and the underlying RPE if left unchecked. Without a functional ATP-binding cassette, sub-family A, member 4 (ABCA4), there is an elevation of all-trans-retinal and prolonged buildup of all-trans-retinal adducts, resulting in a retinal degenerative disease known as Stargardt-1 disease. Even in this monogenic disorder, there is significant heterogeneity in the time to onset of symptoms among patients. Using a combination of molecular techniques, we studied Abca4 knockout (simulating human noncoding disease variants) and Abca4 knock-in mice (simulating human misfolded, catalytically inactive protein variants), which serve as models for Stargardt-1 disease. We compared the two strains to ascertain whether they exhibit differential responses to agents that affect cytokine signaling and/or ceramide metabolism, as alterations in either of these pathways can exacerbate retinal degenerative phenotypes. We found different degrees of responsiveness to maraviroc, a known immunomodulatory CCR5 antagonist, and to the ceramide-lowering agent AdipoRon, an agonist of the ADIPOR1 and ADIPOR2 receptors. The two strains also display different degrees of transcriptional deviation from matched WT controls. Our phenotypic comparison of the two distinct Abca4 mutant-mouse models sheds light on potential therapeutic avenues previously unexplored in the treatment of Stargardt disease and provides a surrogate assay for assessing the effectiveness for genome editing.

Major Contribution of c.[1622T>C;3113C>T] Complex Allele and c.5882G>A Variant in ABCA4-Related Retinal Dystrophy in an Eastern European Population.

Inherited retinal diseases (IRDs) constitute a prevalent group of inherited ocular disorders characterized by marked genetic diversity alongside moderate clinical variability. Among these, ABCA4-related eye pathology stands as a prominent form affecting the retina. In this study, we conducted an in-depth analysis of 96 patients harboring ABCA4 variants in the European part of Russia. Notably, the complex allele c.[1622T>C;3113C>T] (p.Leu541Pro;Ala1038Val, or L541P;A1038V) and the variant c.5882G>A (p.Gly1961Glu or G1961E) emerged as primary contributors to this ocular pathology within this population. Additionally, we elucidated distinct disease progression characteristics associated with the G1961E variant. Furthermore, our investigation revealed that patients with loss-of-function variants in ABCA4 were more inclined to develop phenotypes distinct from Stargardt disease. These findings provide crucial insights into the genetic and clinical landscape of ABCA4-related retinal dystrophies in this specific population.