Retinal Architecture in ​\u3cem\u3eRGS9-\u3c/em\u3e and ​\u3cem\u3eR9AP\u3c/em\u3e-Associated Retinal Dysfunction (Bradyopsia)

Purpose To characterize photoreceptor structure and mosaic integrity in subjects with RGS9- and R9AP-associated retinal dysfunction (bradyopsia) and compare to previous observations in other cone dysfunction disorders such as oligocone trichromacy. Design Observational case series. Methods setting: Moorfields Eye Hospital (United Kingdom) and Medical College Wisconsin (USA). study population: Six eyes of 3 subjects with disease-causing variants in RGS9 or R9AP. main outcome measures: Detailed retinal imaging using spectral-domain optical coherence tomography and confocal adaptive-optics scanning light ophthalmoscopy. Results Cone density at 100 μm from foveal center ranged from 123 132 cones/mm2to 140 013 cones/mm2. Cone density ranged from 30 573 to 34 876 cones/mm2 by 600 μm from center and from 15 987 to 16,253 cones/mm2 by 1400 μm from center, in keeping with data from normal subjects. Adaptive-optics imaging identified a small, focal hyporeflective lesion at the foveal center in both eyes of the subject with RGS9-associated disease, corresponding to a discrete outer retinal defect also observed on spectral-domain optical coherence tomography; however, the photoreceptor mosaic remained intact at all other observed eccentricities. Conclusions Bradyopsia and oligocone trichromacy share common clinical symptoms and cannot be discerned on standard clinical findings alone. Adaptive-optics imaging previously demonstrated a sparse mosaic of normal wave-guiding cones remaining at the fovea, with no visible structure outside the central fovea in oligocone trichromacy. In contrast, the subjects presented in this study with molecularly confirmed bradyopsia had a relatively intact and structurally normal photoreceptor mosaic, allowing the distinction between these disorders based on the cellular phenotype and suggesting different pathomechanisms

Isolated rod dysfunction associated with a novel genotype of CNGB1

Purpose: To describe the clinical and electrophysiological features of an unusual retinopathy in a patient with a novel genotype of CNGB1, mutations in which are implicated in autosomal recessive retinitis pigmentosa (rod-cone dystrophy). Observations: A 61-year old asymptomatic woman was referred to the inherited retinal disorders clinic because of peripheral retinal pigmentary changes. She had normal visual acuity and color vision. Clinical examination and detailed imaging of the macula were normal, but there was atrophy of the outer retina in the periphery with sparse intra-retinal pigmentation. Electroretinography (ERG) revealed undetectable rod responses, with normal cone-mediated responses. The pattern ERG was normal. Genetic analysis identified two previously unreported variants in CNGB1: (c.2258T > A, p.[Leu753*] and c.807G > C, p.[Gln269His]), shown to be in trans. Conclusions and importance: This report describes a functionally cone-isolated retina in an adult, apparently hemizygous for a novel missense mutation in CNGB1, a novel phenotype for this gene. The p.[Gln269His] allele is the first missense change, within the glutamic acid-rich protein (GARP) domain of CNGB1, to be associated with retinal disease in humans

CERKL-associated retinal dystrophy: Genetics, Phenotype and Natural History

PURPOSE: To analyze the clinical characteristics, natural history, and genetics of CERKL-associated retinal dystrophy in the largest series to date. DESIGN: Multicenter retrospective cohort study. SUBJECTS: 47 patients (37 families) with likely disease-causing CERKL variants METHODS: Review of clinical notes, ophthalmic images, and molecular diagnosis from two international centres. MAIN OUTCOME MEASURES: Visual function, retinal imaging and characteristics were evaluated and correlated. RESULTS: The mean age at the first visit was 29.6 + 13.9 years and the mean follow-up time was 9.1 + 7.4 years. The most frequent initial symptom was central vision loss (40%) and the most common retinal feature was well-demarcated areas of macular atrophy (57%). Seventy percent of the participants had double-null genotypes and 64% had electrophysiological assessment. Amongst the latter, 53% showed similar severity of rod and cone dysfunction, 27% revealed a rod-cone, 10% a cone-rod, and 10% a macular dystrophy dysfunction pattern. Patients without double-null genotypes tended to have fewer pigment deposits and included a higher proportion of older patients with a relatively mild electrophysiological phenotype. Longitudinal analysis showed that over half of the cohort lost 15 ETDRS letters or more in at least one eye during the first 5 years of follow up. CONCLUSIONS: The phenotype of CERKL-retinal dystrophy is broad, encompassing isolated macular disease to severe retina-wide involvement, with a range of functional phenotypes, generally not fitting in the rod-cone/cone-rod dichotomy. Disease onset is often earlier, with more severe retinal degenerative changes and photoreceptor dysfunction, in nullizygous cases

Ceramide synthase TLCD3B is a novel gene associated with human recessive retinal dystrophy

PURPOSE: Previous studies suggest that ceramide is a proapoptotic lipid as high levels of ceramides can lead to apoptosis of neuronal cells, including photoreceptors. However, no pathogenic variant in ceramide synthases has been identified in human patients and knockout of various ceramide synthases in mice has not led to photoreceptor degeneration. METHODS: Exome sequencing was used to identify candidate disease genes in patients with vision loss as confirmed by standard evaluation methods, including electroretinography (ERG) and optical coherence tomography. The vision loss phenotype in mice was evaluated by ERG and histological analyses. RESULTS: Here we have identified four patients with cone-rod dystrophy or maculopathy from three families carrying pathogenic variants in TLCD3B. Consistent with the phenotype observed in patients, the Tlcd3bKO/KO mice exhibited a significant reduction of the cone photoreceptor light responses, thinning of the outer nuclear layer, and loss of cone photoreceptors across the retina. CONCLUSION: Our results provide a link between loss-of-function variants in a ceramide synthase gene and human retinal dystrophy. Establishment of the Tlcd3b knockout murine model, an in vivo photoreceptor cell degeneration model due to loss of a ceramide synthase, will provide a unique opportunity in probing the role of ceramide in survival and function of photoreceptor cells

Genetic Basis of Inherited Retinal Disease in a Molecularly Characterized Cohort of More Than 3000 Families from the United Kingdom.

PURPOSE: In a large cohort of molecularly characterized inherited retinal disease (IRD) families, we investigated proportions with disease attributable to causative variants in each gene. DESIGN: Retrospective study of electronic patient records. PARTICIPANTS: Patients and relatives managed in the Genetics Service of Moorfields Eye Hospital in whom a molecular diagnosis had been identified. METHODS: Genetic screening used a combination of single-gene testing, gene panel testing, whole exome sequencing, and more recently, whole genome sequencing. For this study, genes listed in the Retinal Information Network online resource (https://sph.uth.edu/retnet/) were included. Transcript length was extracted for each gene (Ensembl, release 94). MAIN OUTCOME MEASURES: We calculated proportions of families with IRD attributable to variants in each gene in the entire cohort, a cohort younger than 18 years, and a current cohort (at least 1 patient encounter between January 1, 2017, and August 2, 2019). Additionally, we explored correlation between numbers of families and gene transcript length. RESULTS: We identified 3195 families with a molecular diagnosis (variants in 135 genes), including 4236 affected individuals. The pediatric cohort comprised 452 individuals from 411 families (66 genes). The current cohort comprised 2614 families (131 genes; 3130 affected individuals). The 20 most frequently implicated genes overall (with prevalence rates per families) were as follows: ABCA4 (20.8%), USH2A (9.1%), RPGR (5.1%), PRPH2 (4.6%), BEST1 (3.9%), RS1 (3.5%), RP1 (3.3%), RHO (3.3%), CHM (2.7%), CRB1 (2.1%), PRPF31 (1.8%), MY07A (1.7%), OPA1 (1.6%), CNGB3 (1.4%), RPE65 (1.2%), EYS (1.2%), GUCY2D (1.2%), PROM1 (1.2%), CNGA3 (1.1%), and RDH12 (1.1%). These accounted for 71.8% of all molecularly diagnosed families. Spearman coefficients for correlation between numbers of families and transcript length were 0.20 (P = 0.025) overall and 0.27 (P = 0.017), -0.17 (P = 0.46), and 0.71 (P = 0.047) for genes in which variants exclusively cause recessive, dominant, or X-linked disease, respectively. CONCLUSIONS: Our findings help to quantify the burden of IRD attributable to each gene. More than 70% of families showed pathogenic variants in 1 of 20 genes. Transcript length (relevant to gene delivery strategies) correlated significantly with numbers of affected families (but not for dominant disease)

Broadening INPP5E phenotypic spectrum: detection of rare variants in syndromic and non-syndromic IRD

Pathogenic variants in INPP5E cause Joubert syndrome (JBTS), a ciliopathy with retinal involvement. However, despite sporadic cases in large cohort sequencing studies, a clear association with non-syndromic inherited retinal degenerations (IRDs) has not been made. We validate this association by reporting 16 non-syndromic IRD patients from ten families with bi-allelic mutations in INPP5E. Additional two patients showed early onset IRD with limited JBTS features. Detailed phenotypic description for all probands is presented. We report 14 rare INPP5E variants, 12 of which have not been reported in previous studies. We present tertiary protein modeling and analyze all INPP5E variants for deleteriousness and phenotypic correlation. We observe that the combined impact of INPP5E variants in JBTS and non-syndromic IRD patients does not reveal a clear genotype–phenotype correlation, suggesting the involvement of genetic modifiers. Our study cements the wide phenotypic spectrum of INPP5E disease, adding proof that sequence defects in this gene can lead to early-onset non-syndromic IRD

Clinical Features of a Retinopathy Associated With a Dominant Allele of the RGR Gene

Purpose: We describe the clinical features in two pedigrees with dominantly inherited retinopathy segregating the previously reported frameshifting mutation, c.836dupG (p.Ile280Asn*78) in the terminal exon of the RGR gene, and compare their haplotypes to that of the previously reported pedigree. Methods: The probands were ascertained at West Virginia University Eye Institute (WVU) and Moorfields Eye Hospital (MEH) through next generation sequencing (NGS) and whole genome sequencing (WGS) respectively. Clinical data included visual acuity (VA), visual fields, fundus autofluorescence (FAF), optical coherence tomography (OCT), and electroretinography (ERG). Haplotype analysis was performed using Sanger sequencing of the DNA from the molecularly ascertained individuals from the three pedigrees. Results: Nine heterozygous mutation carriers were identified in two families. Four carriers were asymptomatic; five carriers had variable VA reduction, visual field constriction, and experienced difficulty under dim illumination. Fundus examination of the asymptomatic carriers showed diffuse or reticular pigmentation of the retina; the symptomatic carriers had chorioretinal atrophy. FAF imaging showed widespread signal loss in advanced retinopathy, and reticular hyperautofluorescence in mild cases. OCT showed loss of outer retinal lamina in advanced disease. ERG showed moderate-to-severe rod–cone dysfunction in two symptomatic carriers; and was normal in three asymptomatic carriers. A shared haplotype flanking the mutation of up to 6.67 Mb was identified in both families. Within this region, 1.27 Mb were shared with the first family reported with this retinopathy. Conclusions: The clinical data suggest a variable and slow degeneration of the RPE. A shared chromosomal segment surrounding the RGR gene suggests a single ancestral mutational event underlying all three families