Multimodal Evaluation and Management of Wagner Syndrome-Three Patients from an Affected Family.

Wagner syndrome is a rare autosomal dominant vitreoretinopathy caused by mutations in chondroitin sulphate proteoglycan 2 (CSPG2)/Versican (VCAN). Here, we present a retrospective case series of a family pedigree with genetically confirmed Wagner syndrome (heterozygous VCAN exon 8 deletion), as follows: a 34-year-old mother (P1), 12-year-old daughter (P2), and a 2-year-old son (P3). The phenotype included early-onset cataract (P1), optically empty vitreous with avascular membranes (P1, 2), nasal dragging of optic nerve heads associated with foveal hypoplasia (P1, 2), tractional retinoschisis on optical coherence tomography (P2), and peripheral circumferential vitreo-retinal interface abnormality resembling white-without-pressure (P3) progressing to pigmented chorio-retinal atrophy (P1, 2). P2 developed a macula-off retinal detachment, which was treated initially with encircling band + vitrectomy + gas, followed by vitrectomy + heavy silicone oil tamponade for re-detachment from new inferior breaks. Strong vitreo-retinal adhesion was noted intraoperatively, which prevented the separation of posterior hyaloid beyond the equator. Electroretinograms from P1&2 demonstrated attenuated b-waves, a-waves, and flicker responses in light- and dark-adapted conditions, suggestive of generalised retinal dysfunction. Our patients demonstrated the clinical spectrum of Wagner syndrome, highlighting nasal dragging with foveal disruption as a distinguishing feature from other inherited vitreoretinopathies. Surgical outcomes demonstrate significant challenges in managing vitreo-retinal traction and need for further research into strategies to prevent sight loss.

Update on Clinical Trial Endpoints in Gene Therapy Trials for Inherited Retinal Diseases.

Inherited retinal diseases (IRDs) encompass a wide spectrum of rare conditions characterized by diverse phenotypes associated with hundreds of genetic variations, often leading to progressive visual impairment and profound vision loss. Multiple natural history studies and clinical trials exploring gene therapy for various IRDs are ongoing. Outcomes for ophthalmic trials measure visual changes in three main categories-structural, functional, and patient-focused outcomes. Since IRDs may range from congenital with poor central vision from birth to affecting the peripheral retina initially and progressing insidiously with visual acuity affected late in the disease course, typical outcome measures such as central visual acuity and ocular coherence tomography (OCT) imaging of the macula may not provide adequate representation of therapeutic outcomes including alterations in disease course. Thus, alternative unique outcome measures are necessary to assess loss of peripheral vision, color vision, night vision, and contrast sensitivity in IRDs. These differences have complicated the assessment of clinical outcomes for IRD therapies, and the clinical trials for IRDs have had to design novel specialized endpoints to demonstrate treatment efficacy. As genetic engineering and gene therapy techniques continue to advance with growing investment from industry and accelerated approval tracks for orphan conditions, the clinical trials must continue to improve their assessments to demonstrate safety and efficacy of new gene therapies that aim to come to market. Here, we will provide an overview of the current gene therapy approaches, review various endpoints for measuring visual function, highlight those that are utilized in recent gene therapy trials, and provide an overview of stage 2 and 3 IRD trials through the second quarter of 2024.

Telomere Biology Disorders: Report on Clinical and Angiographic Findings.

PURPOSE: To evaluate the retinal vasculature in pediatric patients with telomere biology disorders (TBD). DESIGN: Retrospective consecutive case series. SUBJECTS: Pediatric patients with a diagnosis of TBD who underwent widefield fluorescein angiography (FA). METHODS: Electronic medical records of pediatric patients with TBD at a tertiary referral eye center were reviewed from January 2019 to July 2023. Vascular phenotype was assessed by reviewing FA images. MAIN OUTCOMES MEASURES: Incomplete peripheral vascularization, aneurysmal dilatation, terminal arborization, anastomotic loops, capillary dropout, neovascularization, tortuosity, leakage from tractional membranes, and blockage from hemorrhage. RESULTS: Fourteen eyes from 7 patients were included. All patients were genetically confirmed for TBD. The most common genetic variants were in CTC1 (5 patients; 71.4%), ACD (1 patient; 14.3%), and RTEL1 (1 patient; 14.3%). On FA, the most common findings were incomplete peripheral vascularization (14 eyes, 100%), aneurysmal dilatation (12 eyes, 85.7%), terminal arborization (12 eyes, 85.7%), anastomotic loops (12 eyes, 85.7%), capillary dropout (10 eyes, 71.4%), and neovascularization (9 eyes, 64.3%). Regarding treatment, laser photocoagulation (14 eyes, 100%), intravitreal bevacizumab injection (13 eyes, 92.6%), and sub-tenon's Kenalog (11 eyes, 78.6%) were utilized. All patients managed with laser photocoagulation and/or bevacizumab required multiple treatments. CONCLUSION: Our study describes a spectrum of vascular changes evidenced by widefield FA in pediatric patients with genetically confirmed TBD. Although further research is warranted to fully understand the etiology of these subtle vascular anomalies, widefield FA should be conducted in patients with genetically confirmed or suspected TBD.

Refractive Error in Inherited Retinal Disease.

PURPOSE: Inherited retinal dystrophies (IRDs) lead to significant vision impairment. Refractive errors (RE) are also associated with vision impairment and an increased risk of ocular comorbidities and may compound impairment caused by IRDs. Identifying the pattern of RE in IRDs may assist in the better management of patients with IRD and provide insights into understanding genetic associations with RE. The aim of this study was to investigate the patterns of RE in patients with IRD from three academic ophthalmology referral centers. DESIGN: Retrospective tri-center cohort study. METHODS: Chart review of clinically and molecularly confirmed IRD cases seen at the University of California San Diego, Oregon Health & Science University, and Children's Hospital Los Angeles. Data retrieved included: demographics, disease phenotype, genotype, best-corrected visual acuity, objective, and/or subjective refraction. RESULTS: A total of 1942 patient notes were reviewed, of these 634 patients (1255 eyes) had refractive data. For genes associated with myopia, NYX (n=14 [1%]) was associated with the highest SER of myopia (mean -9.26 diopters (D) [95% CI -11.867, -6.651], P<0.001) followed by IMPG2 (n=16 [1.1%]) (mean -4.062 D [95% CI -6.254, -1.871], P=0.002), then RPGR (n=104 [7.2%]) (mean -2.664 D [95% CI [-3.618, -1.710], P=0.016) and for genes associated with hyperopia, BEST1 (n= 38 [2.6%]) had the highest SER for hyperopia (mean 2.996 D [95% CI 1.830, 4.162], P<0.001) followed by RS1 (n=26 [1.8%]) (mean 2.562 D [95% CI 1.454, 3.671], P<0.001), then CNGA3 (n=28 [1.9%]) (mean 0.603 D [(95% CI -0.48, 1.686]), P=0.009). Overall patients with IRD were significantly more myopic than age matched population controls. (n=eyes) CONCLUSION: By combining genetic testing with refraction data from a large cohort of patients, we identify IRD genes associated with myopia and hyperopia. However, we find that the pattern of ametropia varies widely not only by gene but also within a gene cohort. The genes identified to be associated with RE are candidates for further in-depth investigation to understand their functional role in RE.

Ophthalmic findings in Alström syndrome.

IMPORTANCE: Alström syndrome is a rare genetic disorder characterized by retinopathy and has life-threatening complications. Alström syndrome is frequently misdiagnosed or confused with other early childhood disorders with retinopathy.  Understanding the spectrum of ocular manifestations of Alström syndrome is essential for ophthalmologists to recognize the cause and institute-appropriate care for this disorder that requires multidisciplinary attention. OBJECTIVE: To quantify and summarize the common ocular findings of Alström syndrome. DESIGN: Case series, clinical exam data obtained from 2015 to 2023. SETTING: Semiannual multidisciplinary Alström syndrome clinics (2015-2023) at the Greater Baltimore Medical Center (GBMC), organized by Alström Syndrome International (ASI). PARTICIPANTS: Forty-eight patients (38 children, 10 adults) with a known diagnosis of Alström syndrome participated in the semiannual multidisciplinary Alström syndrome clinics. Patients apply to be seen and are accepted based on need and capacity. INTERVENTION(S) OR EXPOSURE(S): Not applicable. MAIN OUTCOME(S) AND MEASURE(S): Clinical ocular findings. RESULTS: Participants in this study had a median age of 8 years (15 months to 42 years). Visual acuity and progression of vision loss varied. The youngest patient who was legally blind was 2 years old. The oldest patient who maintained useful vision was 7 years old. All patients 8 years old or older were legally blind. Nystagmus (94%, 45 of 48) and photophobia (73%, 35 of 48) were the most common first presenting ocular symptoms in childhood. Retinal vascular attenuation (91%, 40 of 44) and retinal internal limiting membrane changes (68%, 30 of 44) were the most commonly documented retinal findings in both children and adults followed by optic nerve (ON) pallor and retinal pigment epithelium (RPE) mottling. Less than half of the children had ON pallor (38%, 14 of 37) and RPEmottling (38%, 14 of 37), while all adults had these two findings (100%, 7 of 7). Retinal pigment clumps were not common in children (11%, 4 of 37), while common in adults (86%, 6 of 7). CONCLUSIONS AND RELEVANCE: Knowledge of these ocular findings is key to promptly recognize Alström syndrome. The ocular phenotype of Alström syndrome is largely dependent on age, suggesting that low vision interventions and potential gene-based therapeutics should target children with this disorder.

Question: What are the common ocular findings in Alström syndrome?Findings: In this case series study that included 48 patients with Alström syndrome, common ocular findings were retinal vascular attenuation and retinal internal limiting membrane changes documented in both children and adults. Optic nerve (ON) pallor and retinal pigment epithelium (RPE) mottling were relatively less common.Meaning: Knowledge of these clinical findings is essential to recognize this potentially vision- and life-threatening condition and to guide the optimal timing for receiving gene-based treatment in the future.

Mild retinitis pigmentosa, including sector retinitis pigmentosa associated with 2 pathogenic variants in CDH23.

BACKGROUND: Biallelic pathogenic variants in CDH23 can cause Usher syndrome type I (USH1), typically characterized by sensorineural hearing loss, variable vestibular areflexia, and a progressive form of rod-cone dystrophy. While missense variants in CDH23 can cause DFNB12 deafness, other variants can affect the cadherin 23 function, more severely causing Usher syndrome type I D. The main purpose of our study is to describe the genotypes and phenotypes of patients with mild retinitis pigmentosa (RP), including sector RP with two pathogenic variants in CDH23. MATERIALS AND METHODS: Clinical examination included medical history, comprehensive ophthalmologic examination, and multimodal retinal imaging, and in case 1 and 2, full-field electroretinography (ERG). Genetic analysis was performed in all cases, and segregation testing of proband relatives was performed in case 1 and 3. RESULTS: Three unrelated cases presented with variable clinical phenotype for USH1 and were found to have two pathogenic variants in CDH23, with missense variant, c.5237 G > A: p.Arg1746Gln being common to all. All probands had mild to profound hearing loss. Case 1 and 3 had mild RP with mid peripheral and posterior pole sparing, while case 2 had sector RP. ERG results were consistent with the marked loss of retinal function in both eyes at the level of photoreceptor in case 1 and case 2, with normal peak time in the former. CONCLUSION: Patients harbouring c.5237 G > A: p.Arg1746Gln variants in CDH23 can present with a mild phenotype including sector RP. This can aid in better genetic counselling and in prognostication.

Investigating Splice Defects in USH2A Using Targeted Long-Read Sequencing.

Biallelic variants in USH2A are associated with retinitis pigmentosa (RP) and Type 2 Usher Syndrome (USH2), leading to impaired vision and, additionally, hearing loss in the latter. Although the introduction of next-generation sequencing into clinical diagnostics has led to a significant uplift in molecular diagnostic rates, many patients remain molecularly unsolved. It is thought that non-coding variants or variants of uncertain significance contribute significantly to this diagnostic gap. This study aims to demonstrate the clinical utility of the reverse transcription-polymerase chain reaction (RT-PCR)-Oxford Nanopore Technology (ONT) sequencing of USH2A mRNA transcripts from nasal epithelial cells to determine the splice-altering effect of candidate variants. Five affected individuals with USH2 or non-syndromic RP who had undergone whole genome sequencing were recruited for further investigation. All individuals had uncertain genotypes in USH2A, including deep intronic rare variants, c.8682-654C>G, c.9055+389G>A, and c.9959-2971C>T; a synonymous variant of uncertain significance, c.2139C>T; p.(Gly713=); and a predicted loss of function duplication spanning an intron/exon boundary, c.3812-3_3837dup p.(Met1280Ter). In silico assessment using SpliceAI provided splice-altering predictions for all candidate variants which were investigated using ONT sequencing. All predictions were found to be accurate; however, in the case of c.3812-3_3837dup, the outcome was a complex cryptic splicing pattern with predominant in-frame exon 18 skipping and a low level of exon 18 inclusion leading to the predicted stop gain. This study detected and functionally characterised simple and complex mis-splicing patterns in USH2A arising from previously unknown deep intronic variants and previously reported variants of uncertain significance, confirming the pathogenicity of the variants.

Genetic Testing of Patients with Inherited Retinal Diseases in the European Countries: An International Survey by the European Vision Institute.

INTRODUCTION: The purpose of this project was to explore the current standards of clinical care genetic testing and counseling for patients with inherited retinal diseases (IRDs) from the perspective of leading experts in selected European countries. Also, to gather opinions on current bottlenecks and future solutions to improve patient care. METHODS: On the initiative of the European Vision Institute, a survey questionnaire with 41 questions was designed and sent to experts in the field from ten European countries. Each participant was asked to answer with reference to the situation in their own country. RESULTS: Sixteen questionnaires were collected by November 2023. IRD genetic tests are performed in clinical care settings for 80% or more of tested patients in 9 countries, and the costs of genetic tests in clinical care are covered by the public health service to the extent of 90% or more in 8 countries. The median proportion of patients who are genetically tested, the median rate of genetically solved patients among those who are tested, and the median proportion of patients receiving counseling are 51-70%, 61-80%, and 61-80%, respectively. Improving the education of healthcare professionals who facilitate patient referrals to specialized centers, improving access of patients to more thorough genotyping, and increasing the number of available counselors were the most advocated solutions. CONCLUSION: There is a significant proportion of IRD patients who are not genetically tested, whose genetic testing is inconclusive, or who do not receive counseling. Educational programs, greater availability of state-of-the-art genotyping and genetic counselors could improve healthcare for IRD patients.

The Surviving, Not Thriving, Photoreceptors in Patients with ABCA4 Stargardt Disease.

Stargardt disease (STGD1), associated with biallelic variants in the ABCA4 gene, is the most common heritable macular dystrophy and is currently untreatable. To identify potential treatment targets, we characterized surviving STGD1 photoreceptors. We used clinical data to identify macular regions with surviving STGD1 photoreceptors. We compared the hyperreflective bands in the optical coherence tomographic (OCT) images that correspond to structures in the STGD1 photoreceptor inner segments to those in controls. We used adaptive optics scanning light ophthalmoscopy (AO-SLO) to study the distribution of cones and AO-OCT to evaluate the interface of photoreceptors and retinal pigment epithelium (RPE). We found that the profile of the hyperreflective bands differed dramatically between patients with STGD1 and controls. AO-SLOs showed patches in which cone densities were similar to those in healthy retinas and others in which the cone population was sparse. In regions replete with cones, there was no debris at the photoreceptor-RPE interface. In regions with sparse cones, there was abundant debris. Our results raise the possibility that pharmaceutical means may protect surviving photoreceptors and so mitigate vision loss in patients with STGD1.

Cross-species single-cell landscapes identify the pathogenic gene characteristics of inherited retinal diseases.

Introduction: Inherited retinal diseases (IRDs) affect ∼4.5 million people worldwide. Elusive pathogenic variants in over 280 genes are associated with one or more clinical forms of IRDs. It is necessary to understand the complex interaction among retinal cell types and pathogenic genes by constructing a regulatory network. In this study, we attempt to establish a panoramic expression view of the cooperative work in retinal cells to understand the clinical manifestations and pathogenic bases underlying IRDs. Methods: Single-cell RNA sequencing (scRNA-seq) data on the retinas from 35 retina samples of 3 species (human, mouse, and zebrafish) including 259,087 cells were adopted to perform a comparative analysis across species. Bioinformatic tools were used to conduct weighted gene co-expression network analysis (WGCNA), single-cell regulatory network analysis, cell-cell communication analysis, and trajectory inference analysis. Results: The cross-species comparison revealed shared or species-specific gene expression patterns at single-cell resolution, such as the stathmin family genes, which were highly expressed specifically in zebrafish Müller glias (MGs). Thirteen gene modules were identified, of which nine were associated with retinal cell types, and Gene Ontology (GO) enrichment of module genes was consistent with cell-specific highly expressed genes. Many IRD genes were identified as hub genes and cell-specific regulons. Most IRDs, especially the retinitis pigmentosa (RP) genes, were enriched in rod-specific regulons. Integrated expression and transcription regulatory network genes, such as congenital stationary night blindness (CSNB) genes GRK1, PDE6B, and TRPM1, showed cell-specific expression and transcription characteristics in either rods or bipolar cells (BCs). IRD genes showed evolutionary conservation (GNAT2, PDE6G, and SAG) and divergence (GNAT2, MT-ND4, and PDE6A) along the trajectory of photoreceptors (PRs) among species. In particular, the Leber congenital amaurosis (LCA) gene OTX2 showed high expression at the beginning of the trajectory of both PRs and BCs. Conclusion: We identified molecular pathways and cell types closely connected with IRDs, bridging the gap between gene expression, genetics, and pathogenesis. The IRD genes enriched in cell-specific modules and regulons suggest that these diseases share common etiological bases. Overall, mining of interspecies transcriptome data reveals conserved transcriptomic features of retinas across species and promising applications in both normal retina anatomy and retina pathology.

Retinal vascular reactivity in carriers of X-linked inherited retinal disease - a study using optical coherence tomography angiography.

Purpose: Female carriers of X-linked inherited retinal diseases (IRDs) can show highly variable phenotypes and disease progression. Vascular reactivity, a potential disease biomarker, has not been investigated in female IRD carriers. In this study, functional optical coherence tomography angiography (OCT-A) was used to dynamically assess the retinal microvasculature of X-linked IRD carriers. Methods: Genetically confirmed female carriers of IRDs (choroideremia or X-linked retinitis pigmentosa), and healthy women were recruited. Macular angiograms (3x3mm, Zeiss Plex Elite 9000) were obtained in 36 eyes of 15 X-linked IRD female carriers and 21 age-matched control women. Two tests were applied to test vascular reactivity: (i) mild hypoxia and (ii) handgrip test, to induce a vasodilatory or vasoconstrictive response, respectively. Changes to vessel density (VD) and vessel length density (VLD) were independently evaluated during each of the tests for both the superficial and deep capillary plexuses. Results: In the control group, the superficial and deep VD decreased during the handgrip test (p<0.001 and p=0.037, respectively). Mean superficial VLD also decreased during the handgrip test (p=0.025), while the deep plexus did not change significantly (p=0.108). During hypoxia, VD and VLD increased in the deep plexus (p=0.027 and p=0.052, respectively) but not in the superficial plexus. In carriers, the physiologic vascular responses seen in controls were not observed in either plexus during either test, with no difference in VD or VLD noted (all p>0.05). Conclusions: Functional OCT-A is a useful tool to assess dynamic retinal microvascular changes. Subclinical impairment of the physiological vascular responses seen in carriers of X-linked IRDs may serve as a valuable clinical biomarker.

Investigating the impact of asymmetric macular sensitivity on visual acuity chart reading in choroideremia.

INTRODUCTION: Degeneration in choroideremia, unlike typical centripetal photoreceptor degenerations, is centred temporal to the fovea. Once the fovea is affected, the nasal visual field (temporal retina) is relatively spared, and the preferred retinal locus shifts temporally. Therefore, when reading left to right, only the right eye reads into a scotoma. We investigate how this unique property affects the ability to read an eye chart. METHODS: Standard- and low-luminance visual acuity (VA) for right and left eyes were measured with the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart. Letters in each line were labelled by column position. The numbers of letter errors for each position across the whole chart were summed to produce total column error scores for each participant. Macular sensitivity was assessed using microperimetry. Central sensitivity asymmetry was determined by the temporal-versus-nasal central macular difference and subsequently correlated to a weighted ETDRS column error score. Healthy volunteers and participants with X-linked retinitis pigmentosa GTPase regulator associated retinitis pigmentosa (RPGR-RP) were used as controls. RESULTS: Thirty-nine choroideremia participants (median age 44.9 years [IQR 35.7-53.5]), 23 RPGR-RP participants (median age 30.8 years [IQR 26.5-40.5]) and 35 healthy controls (median age 23.8 years [IQR 20.3-29.0]) were examined. In choroideremia, standard VA in the right eye showed significantly greater ETDRS column errors on the temporal side compared with the nasal side (p = 0.002). This significantly correlated with greater asymmetry in temporal-versus-nasal central macular sensitivity (p = 0.04). No significant patterns in ETDRS column errors or central macular sensitivity were seen in the choroideremia left eyes, nor in RPGR-RP and control eyes. CONCLUSION: Difficulty in tracking across lines during ETDRS VA testing may cause excess errors independent of true VA. VA assessment with single-letter optotype systems may be more suitable, particularly for patients with choroideremia, and potentially other retinal diseases with asymmetric central macular sensitivity or large central scotomas including geographic atrophy.

A cohort study of 19 patients with gyrate atrophy of the choroid and retina (GACR).

PURPOSE: Gyrate atrophy of the choroid and retina (GACR) is an autosomal recessive inherited metabolic disorder (IMD) characterised by progressive retinal degeneration, leading to severe visual impairment. The rapid developments in ophthalmic genetic therapies warrant knowledge on clinical phenotype of eligible diseases such as GACR to define future therapeutic parameters in clinical trials. METHODS: Retrospective chart analysis was performed in nineteen patients. Data were analysed using IBM SPSS Statistics version 28.0.1.1. RESULTS: Nineteen patients were included with a mean age of 32.6 years (range 8-58). Mean age at onset of ophthalmic symptoms was 7.9 years (range 3-16). Median logMAR of visual acuity at inclusion was 0.26 (range -0.18-3.00). Mean age at cataract surgery was 28.8 years (n = 11 patients). Mean spherical equivalent of the refractive error was -8.96 (range -20.87 to -2.25). Cystoid maculopathy was present in 68% of patients, with a loss of integrity of the foveal ellipsoid zone (EZ) in 24/38 eyes. Of the 14 patients treated with dietary protein restriction, the four patients who started the diet before age 10 showed most benefit. CONCLUSION: This study demonstrates the severe ophthalmic disease course associated with GACR, as well as possible benefit of early dietary treatment. In addition to visual loss, patients experience severe myopia, early-onset cataract, and CME. There is a loss of foveal EZ integrity at a young age, emphasising the need for early diagnosis enabling current and future therapeutic interventions.

Comparison of The Results of Sponsored Genetic Testing Panels for Inherited Retinal Diseases.

Background/Objectives: Gene therapy's emergence has made molecular diagnosis for inherited retinal diseases clinically significant. Free genetic testing panels have improved testing access in clinical practice, yet the interpretation of results, especially variants of unknown significance (VUS), remains challenging and requires expertise. This study shares our experience in utilizing sponsored IRD panel tests by Invitae and Blueprint Genetics (BG), reporting their positivity rates, and comparing their reclassification of variants through amendments. Methods: This retrospective study analyzed genetic test reports from patients who underwent testing via Invitae or BG panels. A positive test was determined if there was a pathogenic mutation in an autosomal dominant gene, two pathogenic mutations in an autosomal recessive gene, or a pathogenic mutation in an X-linked gene in a male patient. Results: The testing positivity rates were 34.9% for Invitae (n = 109) and 42.1% for BG (n = 107). Invitae had more pathogenic variants per report (0.87 vs. 0.58 variants, p = 0.0038) and issued more amendments than BG (0.54 vs. 0.03 amendments; p < 0.01). Of the Invitae variant classification changes, 66.2% switched a VUS to benign. In the BG group, 75% of variant reclassifications changed a VUS to pathogenic. As a result of the Invitae amendments, 88% did not change the overall report result. Conclusions: While free-of-charge genetic testing panels offer valuable insights for diagnosing IRD, limitations such as low diagnostic yield and variant classification discrepancies persist between Invitae and BG. VUS should not be considered pathogenic in the clinical decision-making process. Careful interpretation of genetic testing is required.

Reduced Retinal Pigment Epithelial Autophagy Due to Loss of Rab12 Prenylation in a Human iPSC-RPE Model of Choroideremia.

Choroideremia is an X-linked chorioretinal dystrophy caused by mutations in CHM, encoding Rab escort protein 1 (REP-1), leading to under-prenylation of Rab GTPases (Rabs). Despite ubiquitous expression of CHM, the phenotype is limited to degeneration of the retina, retinal pigment epithelium (RPE), and choroid, with evidence for primary pathology in RPE cells. However, the spectrum of under-prenylated Rabs in RPE cells and how they contribute to RPE dysfunction remain unknown. A CRISPR/Cas-9-edited CHM-/- iPSC-RPE model was generated with isogenic control cells. Unprenylated Rabs were biotinylated in vitro and identified by tandem mass tag (TMT) spectrometry. Rab12 was one of the least prenylated and has an established role in suppressing mTORC1 signaling and promoting autophagy. CHM-/- iPSC-RPE cells demonstrated increased mTORC1 signaling and reduced autophagic flux, consistent with Rab12 dysfunction. Autophagic flux was rescued in CHM-/- cells by transduction with gene replacement (ShH10-CMV-CHM) and was reduced in control cells by siRNA knockdown of Rab12. This study supports Rab12 under-prenylation as an important cause of RPE cell dysfunction in choroideremia and highlights increased mTORC1 and reduced autophagy as potential disease pathways for further investigation.

Differential gene expression between central and peripheral retinal regions in dogs and comparison with humans.

The dog retina contains a central macula-like region, and there are reports of central retinal disorders in dogs with shared genetic etiologies with humans. Defining central/peripheral gene expression profiles may provide insight into the suitability of dogs as models for human disorders. We determined central/peripheral posterior eye gene expression profiles in dogs and interrogated inherited retinal and macular disease-associated genes for differential expression between central and peripheral regions. Bulk tissue RNA sequencing was performed on 8 mm samples of the dog central and superior peripheral regions, sampling retina and retinal pigmented epithelium/choroid separately. Reads were mapped to CanFam3.1, read counts were analyzed to determine significantly differentially expressed genes (DEGs). A similar analytic pipeline was used with a published bulk-tissue RNA sequencing human dataset. Pathways and processes involved in significantly DEGs were identified (Database for Annotation, Visualization and Integrated Discovery). Dogs and humans shared the extent and direction of central retinal differential gene expression, with multiple shared biological pathways implicated in differential expression. Many genes implicated in heritable retinal disorders in dogs and humans were differentially expressed between central and periphery. Approximately half of genes associated with human age-related macular degeneration were differentially expressed in human and dog tissues. We have identified similarities and differences in central/peripheral gene expression profiles between dogs and humans which can be applied to further define the relevance of dogs as models for human retinal disorders.

Comparative 3D genome analysis between neural retina and retinal pigment epithelium reveals differential cis-regulatory interactions at retinal disease loci.

BACKGROUND: Vision depends on the interplay between photoreceptor cells of the neural retina and the underlying retinal pigment epithelium (RPE). Most genes involved in inherited retinal diseases display specific spatiotemporal expression within these interconnected retinal components through the local recruitment of cis-regulatory elements (CREs) in 3D nuclear space. RESULTS: To understand the role of differential chromatin architecture in establishing tissue-specific expression at inherited retinal disease loci, we mapped genome-wide chromatin interactions using in situ Hi-C and H3K4me3 HiChIP on neural retina and RPE/choroid from human adult donor eyes. We observed chromatin looping between active promoters and 32,425 and 8060 candidate CREs in the neural retina and RPE/choroid, respectively. A comparative 3D genome analysis between these two retinal tissues revealed that 56% of 290 known inherited retinal disease genes were marked by differential chromatin interactions. One of these was ABCA4, which is implicated in the most common autosomal recessive inherited retinal disease. We zoomed in on retina- and RPE-specific cis-regulatory interactions at the ABCA4 locus using high-resolution UMI-4C. Integration with bulk and single-cell epigenomic datasets and in vivo enhancer assays in zebrafish revealed tissue-specific CREs interacting with ABCA4. CONCLUSIONS: Through comparative 3D genome mapping, based on genome-wide, promoter-centric, and locus-specific assays of human neural retina and RPE, we have shown that gene regulation at key inherited retinal disease loci is likely mediated by tissue-specific chromatin interactions. These findings do not only provide insight into tissue-specific regulatory landscapes at retinal disease loci, but also delineate the search space for non-coding genomic variation underlying unsolved inherited retinal diseases.

Neovascular Glaucoma in MELAS syndrome.

Purpose: To describe examination and findings in a case of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) with particular focus on the ocular sequelae from diabetes. Observations: Neovascular glaucoma is not a common manifestation of MELAS. Conclusions and Importance: We present a rare case of neovascular glaucoma in a patient with MELAS with a history of diabetes, hearing loss, and macular dystrophy. MELAS should be suspected in patients with this constellation of symptoms.

PRPS1-associated retinopathy: a diagnostic odyssey.

PURPOSE: This study describes how the diagnosis of Usher syndrome was revised to PRPS1-associated retinopathy and Charcot-Marie-Tooth disease type 5. CASE REPORT: A 38-year-old female with bilaterally subnormal vision and non-congenital hearing loss was initially diagnosed with Usher syndrome, based on finding variants in three genes (MYO7A, USH2A, and PCDH15), was re-evaluated at the inherited retinal disorders clinic. She had asymmetric retinopathy and right macular pseudocoloboma. She was also found to have myopathic facies, poor grip strength and atrophy of the calf muscles. Whole exome sequencing including variants in PRPS1 showed a variant (NM_002764.4:c.287 G > A; p.Arg96Gln), which was not detected by targeted Sanger sequencing of the DNA from her mother and sister. CONCLUSION: The constellation of asymmetric retinopathy and non-congenital hearing impairment should prompt the clinician to search for other diagnoses that may not be covered by an Usher syndrome next generation sequencing panel. Interpretation of genetic testing results should be correlated with a detailed clinical phenotype.