Deep phenotypic characterization of the retinal dystrophy in patients with RNU4ATAC-associated Roifman syndrome.

PURPOSE: To characterize the retinal phenotype in RNU4ATAC-associated Roifman syndrome. METHODS: Ten patients (including 8 males) with molecularly confirmed Roifman syndrome underwent detailed ophthalmologic evaluation including fundus imaging, fundus autofluorescence (FAF) imaging, spectral-domain optical coherence tomography (SD-OCT), and electroretinography (ERG). Six patients had follow-up eye exams. All patients also underwent comprehensive examination for features of extra-retinal Roifman syndrome. RESULTS: All patients had biallelic RNU4ATAC variants. Nyctalopia was common (7/10). Visual acuity at presentation ranged from 20/20 to 20/200 (Age Range: 5-41 years). Retinal exam revealed features of generalized retinopathy with mid-peripheral pigment epithelial changes. A para or peri-foveal ring of hyper-autofluorescence was the commonest FAF abnormality noted (6/8). The SD-OCT demonstrated relative preservation of the foveal ellipsoid zone in six cases; associated features included cystoid changes (5/10) and posterior staphyloma (3/10). The ERG was abnormal in all patients; nine showed generalized rod-cone dystrophy, whilst one patient with sectoral retinal involvement only had isolated rod dystrophy (20 years old). On follow-up examination (Mean duration: 8.16 years), progressive loss of visual acuity (2/6), mid-peripheral retinal atrophy (3/6) or shortening of ellipsoid zone width (1/6) were observed. CONCLUSION: This study has characterized the retinal phenotype in RNU4ATAC-associated Roifman syndrome. Retinal involvement is universal, early-onset, and overall, the retinal and FAF features are consistent with rod-cone degeneration that is slowly progressive over time. The sub-foveal retinal ultrastructure is relatively preserved in majority of patients. Phenotypic variability independent of age exists, and more study of allelic- and sex-based determinants of disease severity are necessary.

Photoreceptor function and structure in retinal degenerations caused by biallelic BEST1 mutations.

The only approved retinal gene therapy is for biallelic RPE65 mutations which cause a recessive retinopathy with a primary molecular defect located at the retinal pigment epithelium (RPE). For a distinct recessive RPE disease caused by biallelic BEST1 mutations, a pre-clinical proof-of-concept for gene therapy has been demonstrated in canine eyes. The current study was undertaken to consider potential outcome measures for a BEST1 clinical trial in patients demonstrating a classic autosomal recessive bestrophinopathy (ARB) phenotype. Spatial distribution of retinal structure showed a wide expanse of abnormalities including large intraretinal cysts, shallow serous retinal detachments, abnormalities of inner and outer segments, and an unusual prominence of the external limiting membrane. Surrounding the central macula extending from 7 to 30 deg eccentricity, outer nuclear layer was thicker than expected from a cone only retina and implied survival of many rod photoreceptors. Co-localized however, were large losses of rod sensitivity despite preserved cone sensitivities. The dissociation of rod function from rod structure observed, supports a large treatment potential in the paramacular region for biallelic bestrophinopathies.

Unilateral cataract and congenital stationary night blindness in a child with novel variants in TRPM1.

Unilateral cataract can cause pediatric vision impairment. Although the majority of unilateral cataracts are idiopathic in nature, genetic causes have been reported. We present the case of a 4-week-old child of nonconsanguineous parents who was affected with unilateral cataract. Whole-genome sequencing using DNA extracted from blood and the lens epithelial cells following cataract surgery revealed two presumed pathogenic variants in the TRPM1 gene, the founding member of the melanoma-related transient receptor potential (TRPM) subfamily. TRPM1 is responsible for regulating cation influx to hyperpolarized retinal ON bipolar cells, and mutations in this gene are a major cause of autosomal recessive congenital stationary night blindness (CSNB). Electroretinography revealed findings consistent with CSNB, a phenotype that was not initially suspected, and which would likely have been missed without genome sequencing. It remains unclear whether the TRPM1 variants are associated with the cataract phenotype.

Novel OPN1LW/OPN1MW Exon 3 Haplotype-Associated Splicing Defect in Patients with X-Linked Cone Dysfunction.

Certain combinations of common variants in exon 3 of OPN1LW and OPN1MW, the genes encoding the apo-protein of the long- and middle-wavelength sensitive cone photoreceptor visual pigments in humans, induce splicing defects and have been associated with dyschromatopsia and cone dysfunction syndromes. Here we report the identification of a novel exon 3 haplotype, G-C-G-A-T-T-G-G (referring to nucleotide variants at cDNA positions c.453, c.457, c.465, c.511, c.513, c.521, c.532, and c.538) deduced to encode a pigment with the amino acid residues L-I-V-V-A at positions p.153, p.171, p.174, p.178, and p.180, in OPN1LW or OPN1MW or both in a series of seven patients from four families with cone dysfunction. Applying minigene assays for all observed exon 3 haplotypes in the patients, we demonstrated that the novel exon 3 haplotype L-I-V-V-A induces a strong but incomplete splicing defect with 3-5% of residual correctly spliced transcripts. Minigene splicing outcomes were similar in HEK293 cells and the human retinoblastoma cell line WERI-Rb1, the latter retaining a cone photoreceptor expression profile including endogenous OPN1LW and OPN1MW gene expression. Patients carrying the novel L-I-V-V-A haplotype presented with a mild form of Blue Cone Monochromacy or Bornholm Eye Disease-like phenotype with reduced visual acuity, reduced cone electroretinography responses, red-green color vision defects, and frequently with severe myopia.

Prevalence of Choroidal Abnormalities and Lisch Nodules in Children Meeting Clinical and Molecular Diagnosis of Neurofibromatosis Type 1.

PURPOSE: To determine the prevalence of choroidal abnormalities (CAs) and Lisch nodules (LNs) in children who met the clinical diagnostic criteria (CDC) alone and those with a molecularly confirmed diagnosis (MCD) of neurofibromatosis type 1 (NF1), and to ascertain any differences between the groups. METHODS: This was a cross-sectional observational study. All children who met the CDC and/or had MCD of NF1 and underwent eye examination were included. At least two CAs or LNs between the two eyes were set as a threshold to define the presence of either abnormality. Frequencies alongside 95% confidence intervals (CIs) were calculated. The relationship between patient age and the presence of LNs and/or CAs was estimated using logistic regression. RESULTS: The study cohort included 94 patients; CAs (64%) were more prevalent than LNs (41%) (0.22; 95% CI, 0.08-0.36; P = 0.0023). The probability of the presence of LNs was lower than that of CAs across all ages (odds ratio = 0.37; 95% CI, 0.20-0.69; P = 0.00173). CAs were exclusively found in 37% of patients and LNs in 16%; 80% had either CAs or LNs, or both. In the CDC group (n = 41), the difference in prevalence (CAs = 68%, LNs = 51%) did not attain statistical significance (0.17; 95% CI, -0.06 to 0.40; P = 0.18). In the MCD group (n = 53), the difference in prevalence (CAs = 60%, LNs = 34%) was significant (0.26; 95% CI, 0.006-0.47; P = 0.023). CONCLUSIONS: CAs were more frequent than LNs in pediatric NF1 patients regardless of age and MCD status. Combining ophthalmological exams with near-infrared imaging will increase the diagnostic reach in pediatric NF1. TRANSLATIONAL RELEVANCE: CAs detected on near-infrared imaging are objective biomarkers in NF1. They are more prevalent and detected earlier in the pediatric population compared with LNs. Hence, the presence of CAs should be routinely ascertained in children suspected with NF1.

Gene therapy: perspectives from young adults with Leber's congenital amaurosis.

AIMS/PURPOSE: To investigate Leber congenital amaurosis (LCA) patients' expectations, decision-making processes and gene therapy-related concerns. METHODS: Using a qualitative approach, we explored perceptions of gene therapy and clinical trials among individuals with LCA. Young adults with a clinical diagnosis of LCA were recruited through the Ocular Genetics Programme at the Hospital for Sick Children. Semi-structured interviews were conducted with ten patients and analysed following the principles of qualitative description. RESULTS: Study participants were aware of ongoing gene therapy research trials and actively sought information regarding advances in ophthalmology and vision restoration. The majority of participants would enrol or were enrolled in a gene-replacement therapy trial, while a minority was ambivalent or would not enrol if provided an opportunity. Participants attributed different values to clinical trials, which influenced their willingness to participate. Intrinsic factors related to coping, adaptation to vision loss and resilience also influenced decision-making. DISCUSSION: This study highlights the complex factors involved in gene-therapy-related decision-making and acts as a proponent for adopting patient-centred care strategies when counselling individuals considering gene therapy or clinical trial participation.

COG5 variants lead to complex early onset retinal degeneration, upregulation of PERK and DNA damage.

Leber congenital amaurosis (LCA), a form of autosomal recessive severe early-onset retinal degeneration, is an important cause of childhood blindness. This may be associated with systemic features or not. Here we identified COG5 compound-heterozygous variants in patients affected with a complex LCA phenotype associated with microcephaly and skeletal dysplasia. COG5 is a component of the COG complex, which facilitates retrograde Golgi trafficking; if disrupted this can result in protein misfolding. To date, variants in COG5 have been associated with a distinct congenital disorder of glycosylation (type IIi) and with a variant of Friedreich's ataxia. We show that COG5 variants can also result in fragmentation of the Golgi apparatus and upregulation of the UPR modulator, PKR-like endoplasmic reticulum kinase (PERK). In addition, upregulation of PERK induces DNA damage in cultured cells and in murine retina. This study identifies a novel role for COG5 in maintaining ER protein homeostasis and that disruption of that role results in activation of PERK and early-onset retinal degeneration, microcephaly and skeletal dysplasia. These results also highlight the importance of the UPR pathway in early-onset retinal dystrophy and as potential therapeutic targets for patients.

DYNC2H1 hypomorphic or retina-predominant variants cause nonsyndromic retinal degeneration.

PURPOSE: Determining the role of DYNC2H1 variants in nonsyndromic inherited retinal disease (IRD). METHODS: Genome and exome sequencing were performed for five unrelated cases of IRD with no identified variant. In vitro assays were developed to validate the variants identified (fibroblast assay, induced pluripotent stem cell [iPSC] derived retinal organoids, and a dynein motility assay). RESULTS: Four novel DYNC2H1 variants (V1, g.103327020_103327021dup; V2, g.103055779A>T; V3, g.103112272C>G; V4, g.103070104A>C) and one previously reported variant (V5, g.103339363T>G) were identified. In proband 1 (V1/V2), V1 was predicted to introduce a premature termination codon (PTC), whereas V2 disrupted the exon 41 splice donor site causing incomplete skipping of exon 41. V1 and V2 impaired dynein-2 motility in vitro and perturbed IFT88 distribution within cilia. V3, homozygous in probands 2-4, is predicted to cause a PTC in a retina-predominant transcript. Analysis of retinal organoids showed that this new transcript expression increased with organoid differentiation. V4, a novel missense variant, was in trans with V5, previously associated with Jeune asphyxiating thoracic dystrophy (JATD). CONCLUSION: The DYNC2H1 variants discussed herein were either hypomorphic or affecting a retina-predominant transcript and caused nonsyndromic IRD. Dynein variants, specifically DYNC2H1 variants are reported as a cause of non syndromic IRD.

CRB1-related retinopathy overlapping the ocular phenotype of S-adenosylhomocysteine hydrolase deficiency.

BACKGROUND: S-adenosylhomocysteine hydrolase deficiency due to pathologic variants in AHCY gene is a rare neurometabolic disease for which no eye phenotype has been documented. Pathologic variants in CRB1 gene are known to cause a wide spectrum of autosomal recessive retinal diseases with Leber's congenital amaurosis as a most common. The aim of this study is to report co-inheritance of neurometabolic disease and eye disease in a pedigree. MATERIALS AND METHODS: Comprehensive eye examination was performed in available family members together with color vision test, visual fields, fundus images, OCT, electroretinogram and visual evoked potentials. Genetic testing included whole-exome sequencing (WES), retinal dystrophy gene panel and segregation analysis. RESULTS: Two children from a family not known to be consanguineous were affected with neurometabolic disease and one of them presented with reduced vision due to maculopathy. The mother had symptoms of retinal degeneration of unspecified cause. Clinical WES revealed homozygous missense pathologic variants in AHCY gene c.148G>A, p.(Ala50Thr) as a cause of S-adenosylhomocysteine hydrolase deficiency. Retinal dystrophy gene panel sequencing revealed two heterozygous missense pathologic variants in CRB1 gene c.1831T>C, p.(Ser611Pro) and c.3955T>C, p.(Phe1319Leu) in the proband and her mother. These variants segregated with disease phenotype in family members. CONCLUSIONS: Establishing an ocular genetic diagnosis may be challenging with the co-existence of a rare systemic genetic disease with previously unknown eye involvement. Extensive phenotyping and genotyping of available family members showed that the proband and her mother shared a CRB1-related retinopathy at different stages while the brother did not.

Baseline Visual Field Findings in the RUSH2A Study: Associated Factors and Correlation With Other Measures of Disease Severity.

PURPOSE: To report baseline visual fields in the Rate of Progression in USH2A-related Retinal Degeneration (RUSH2A) study. DESIGN: Cross-sectional study within a natural history study. METHODS: Setting: multicenter, international. STUDY POPULATION: Usher syndrome type 2 (USH2) (n = 80) or autosomal recessive nonsyndromic retinitis pigmentosa (ARRP) (n = 47) associated with biallelic disease-causing sequence variants in USH2A. OBSERVATION PROCEDURES: Repeatability of full-field static perimetry (SP) and between-eye symmetry of kinetic perimetry (KP) were evaluated with intraclass correlation coefficients (ICCs). The association of demographic and clinical characteristics with total hill of vision (VTOT) was assessed with general linear models. Associations between VTOT and other functional and morphologic measures were assessed using Spearman correlation coefficients and t tests. MAIN OUTCOME MEASURES: VTOT (SP) and III4e isopter area (KP). RESULTS: USH2 participants had more severe visual field loss than ARRP participants (P < .001, adjusting for disease duration, age of enrollment). Mean VTOT measures among 3 repeat tests were 32.7 ± 24.1, 31.2 ± 23.4, and 31.7 ± 23.9 decibel-steradians (intraclass correlation coefficient [ICC] = 0.96). Better VA, greater photopic ERG 30-Hz flicker amplitudes, higher mean microperimetry sensitivity, higher central subfield thickness, absence of macular cysts, and higher III4e seeing area were associated with higher VTOT (all r > .48; P < .05). Mean III4e isopter areas for left (4561 ± 4426 squared degrees) and right eyes (4215 ± 4300 squared degrees) were concordant (ICC = 0.94). CONCLUSIONS: USH2 participants had more visual field loss than participants with USH2A-related ARRP, adjusting for duration of disease and age of enrollment. VTOT was repeatable and correlated with other functional and structural metrics, suggesting it may be a good summary measure of disease severity in patients with USH2A-related retinal degeneration.

Transient pupillary light reflex in CEP290- or NPHP5-associated Leber congenital amaurosis: Latency as a potential outcome measure of cone function.

Mutations in photoreceptor cilium genes CEP290 and NPHP5 cause a form of Leber congenital amaurosis (LCA) which typically lacks rods but retains central cones. The current study evaluated the transient pupillary light reflex (TPLR) as an objective outcome measure to assess efficacy of ongoing and future therapies. Eleven eyes of six patients selected for retained cone function were tested with TPLR using full-field stimuli in the dark-adapted state. Stimuli were red or blue with 1 s duration and spanned a 6-log unit dynamic range. TPLR response amplitude was quantified at fixed times of 0.9 and 2 s after stimulus onset and TPLR latency was defined as the time to reach 0.3 mm constriction. Full-field stimulus testing (FST) and static perimetry were used to correlate subjective perception with objective TPLR parameters. TPLR and FST thresholds with both red and blue stimuli were abnormally elevated in patients to near -1.25 log phot-cd·m-2 consistent with the lack of rods. TPLR latencies were delayed on average but showed some differences among patients. Remnant extrafoveal vision was correlated with faster TPLR latencies. Our results support the use of a short TPLR protocol with full-field red stimuli of 0.7 log phot-cd·m-2 or brighter as an objective and convenient outcome measure of cone function in CEP290- and NPHP5-LCA. The latency parameter of the TPLR would be expected to show a detectable change when an intervention modifies cone sensitivity in the extrafoveal region.

Progress in treating inherited retinal diseases: Early subretinal gene therapy clinical trials and candidates for future initiatives.

Due to improved phenotyping and genetic characterization, the field of 'incurable' and 'blinding' inherited retinal diseases (IRDs) has moved substantially forward. Decades of ascertainment of IRD patient data from Philadelphia and Toronto centers illustrate the progress from Mendelian genetic types to molecular diagnoses. Molecular genetics have been used not only to clarify diagnoses and to direct counseling but also to enable the first clinical trials of gene-based treatment in these diseases. An overview of the recent reports of gene augmentation clinical trials by subretinal injections is used to reflect on the reasons why there has been limited success in this early venture into therapy. These first-in human experiences have taught that there is a need for advancing the techniques of delivery of the gene products - not only for refining further subretinal trials, but also for evaluating intravitreal delivery. Candidate IRDs for intravitreal gene delivery are then suggested to illustrate some of the disorders that may be amenable to improvement of remaining central vision with the least photoreceptor trauma. A more detailed understanding of the human IRDs to be considered for therapy and the calculated potential for efficacy should be among the routine prerequisites for initiating a clinical trial.

Healthcare recommendations for Joubert syndrome.

Joubert syndrome (JS) is a recessive neurodevelopmental disorder defined by a characteristic cerebellar and brainstem malformation recognizable on axial brain magnetic resonance imaging as the "Molar Tooth Sign". Although defined by the neurological features, JS is associated with clinical features affecting many other organ systems, particularly progressive involvement of the retina, kidney, and liver. JS is a rare condition; therefore, many affected individuals may not have easy access to subspecialty providers familiar with JS (e.g., geneticists, neurologists, developmental pediatricians, ophthalmologists, nephrologists, hepatologists, psychiatrists, therapists, and educators). Expert recommendations can enable practitioners of all types to provide quality care to individuals with JS and know when to refer for subspecialty care. This need will only increase as precision treatments targeting specific genetic causes of JS emerge. The goal of these recommendations is to provide a resource for general practitioners, subspecialists, and families to maximize the health of individuals with JS throughout the lifespan.

Survey of practice patterns for the management of ophthalmic genetic disorders among AAPOS members: report by the AAPOS Genetic Eye Disease Task Force.

To better understand AAPOS member pediatric ophthalmologists' knowledge and needs regarding genetic eye disorders, the AAPOS Genetic Eye Disease Task Force developed a 16-question survey that was circulated to national and international AAPOS members. Responses to questions on practice patterns, baseline knowledge, and educational interests regarding patients with suspected ophthalmic genetic disorders were collected. A majority of respondents (93%) evaluate patients with suspected genetic disorders. Knowledge gaps were present in heritability of certain conditions, genetic testing strategies, and referral to clinical trials. Most respondents expressed interest in further education in these areas. A model for care is proposed as a first step in the education process.

Coupling of Human Rhodopsin to a Yeast Signaling Pathway Enables Characterization of Mutations Associated with Retinal Disease.

G protein-coupled receptors (GPCRs) are crucial sensors of extracellular signals in eukaryotes, with multiple GPCR mutations linked to human diseases. With the growing number of sequenced human genomes, determining the pathogenicity of a mutation is challenging, but can be aided by a direct measurement of GPCR-mediated signaling. This is particularly difficult for the visual pigment rhodopsin-a GPCR activated by light-for which hundreds of mutations have been linked to inherited degenerative retinal diseases such as retinitis pigmentosa. In this study, we successfully engineered, for the first time, activation by human rhodopsin of the yeast mating pathway, resulting in signaling via a fluorescent reporter. We combine this novel assay for rhodopsin light-dependent activation with studies of subcellular localization, and the upregulation of the unfolded protein response in response to misfolded rhodopsin protein. We use these assays to characterize a panel of rhodopsin mutations with known molecular phenotypes, finding that rhodopsin maintains a similar molecular phenotype in yeast, with some interesting differences. Furthermore, we compare our assays in yeast with clinical phenotypes from patients with novel disease-linked mutations. We demonstrate that our engineered yeast strain can be useful in rhodopsin mutant classification, and in helping to determine the molecular mechanisms underlying their pathogenicity. This approach may also be applied to better understand the clinical relevance of other human GPCR mutations, furthering the use of yeast as a tool for investigating molecular mechanisms relevant to human disease.

BEST1 gene therapy corrects a diffuse retina-wide microdetachment modulated by light exposure.

Mutations in the BEST1 gene cause detachment of the retina and degeneration of photoreceptor (PR) cells due to a primary channelopathy in the neighboring retinal pigment epithelium (RPE) cells. The pathophysiology of the interaction between RPE and PR cells preceding the formation of retinal detachment remains not well-understood. Our studies of molecular pathology in the canine BEST1 disease model revealed retina-wide abnormalities at the RPE-PR interface associated with defects in the RPE microvillar ensheathment and a cone PR-associated insoluble interphotoreceptor matrix. In vivo imaging demonstrated a retina-wide RPE-PR microdetachment, which contracted with dark adaptation and expanded upon exposure to a moderate intensity of light. Subretinal BEST1 gene augmentation therapy using adeno-associated virus 2 reversed not only clinically detectable subretinal lesions but also the diffuse microdetachments. Immunohistochemical analyses showed correction of the structural alterations at the RPE-PR interface in areas with BEST1 transgene expression. Successful treatment effects were demonstrated in three different canine BEST1 genotypes with vector titers in the 0.1-to-5E11 vector genomes per mL range. Patients with biallelic BEST1 mutations exhibited large regions of retinal lamination defects, severe PR sensitivity loss, and slowing of the retinoid cycle. Human translation of canine BEST1 gene therapy success in reversal of macro- and microdetachments through restoration of cytoarchitecture at the RPE-PR interface has promise to result in improved visual function and prevent disease progression in patients affected with bestrophinopathies.

Pupillary Light Reflexes in Severe Photoreceptor Blindness Isolate the Melanopic Component of Intrinsically Photosensitive Retinal Ganglion Cells.

Purpose: Pupillary light reflex (PLR) is driven by outer retinal photoreceptors and by melanopsin-expressing intrinsically photosensitive retinal ganglion cells of the inner retina. To isolate the melanopic component, we studied patients with severe vision loss due to Leber congenital amaurosis (LCA) caused by gene mutations acting on the outer retina. Methods: Direct PLR was recorded in LCA patients (n = 21) with known molecular causation and severe vision loss. Standard stimuli (2.5 log scot-cd.m-2; ∼13 log quanta.cm-2.s-1; achromatic full-field) with 0.1- or 5-second duration were used in all patients. Additional recordings were performed with higher luminance (3.9 log scot-cd.m-2) in a subset of patients. Results: The LCA patients showed no detectable PLR to the standard stimulus with short duration. With longer-duration stimuli, a PLR was detectable in the majority (18/21) of patients. The latency of the PLR was 2.8 ± 1.3 seconds, whereas normal latency was 0.19 ± 0.02 seconds. Peak contraction amplitude in patients was 1.1 ± 0.9 mm at 6.2 ± 2.3 seconds, considerably different from normal amplitude of 4.2 ± 0.4 mm at 3.0 ± 0.4 seconds. Recordings with higher luminance demonstrated that PLRs in severe LCA could also be evoked with short-duration stimuli. Conclusions: The PLR in severe LCA patients likely represents the activation of the melanopic circuit in isolation from rod and cone input. Knowledge of the properties of the human melanopic PLR allows not only comparison to those in animal models but also serves to define the fidelity of postretinal transmission in clinical trials targeting patients with no outer retinal function.