Cone-rod Dystrophy Research Articles

Retinopathy in Mucopolysaccharidoses.

To determine the pattern(s) of onset, variation, and progression of retinopathy in patients with Mucopolysaccharidosis (MPS). Prospective, longitudinal, observational study. Between November 2015 and March 2023, individuals with MPS were recruited from Ophthalmology clinics at the Manchester Royal Eye Hospital, United Kingdom. Participants underwent assessment of visual acuity, corneal clouding, intraocular pressure, along with fundoscopy, ultra-widefield (UWF) colour fundus photography, fundus autofluorescence (FAF) imaging, optical coherence tomography (OCT), and electroretinography (ERG), where feasible. Evaluation of findings from clinical examination, retinal imaging, and electroretinogram studies, to ascertain the presence and patterns of retinopathy. Data was collected for 75 patients, including 45 MPS I, 9 MPS II, 13 MPS IVA, and 8 MPS VI, aged 3-58 years. Fundus photography was conducted in 65 patients, FAF in 61, OCT in 58, and electrodiagnostic studies in 36 participants. Retinopathy was defined as signs of retinal disease evident through retinal examination or fundus photography such as depigmentation, bone-spicule pigmentation, vascular tortuosity, retinal pigment epithelium (RPE) mottling/other changes, macular atrophy/puckering/epiretinal membranes, FAF findings such as a central hyperautofluorescent dot, hyperautofluorescent parafoveal ring, hypoautofluorescent lesions around fovea (double bull's eye), areas of hyper/hypoautofluorescence, and extrafoveal changes, OCT imaging features such as central external limiting membrane (ELM) thickening, RPE disturbance, photoreceptor layer loss, parafoveal retinal atrophy, and outer retinal/intrachoroidal cavities, or electroretinogram studies revealing rod-mediated retinopathy or rod-cone dystrophy. Retinopathy was confirmed in 32 patients, including 25 MPS I, 4 MPS II, 1 MPS IVA, and 2 MPS VI. Five participants were first diagnosed with retinopathy with clinical examination, while 31 participants were identified on UWF colour fundus photography supported by FAF and OCT. 21 patients exhibited ERG abnormalities consistent with retinopathy. Fifteen of the total 32 participants described symptoms of nyctalopia. The onset of retinopathy varied substantially, with initial detection between 2 and 53 years of age. MPS patients as young as 2 may develop retinopathy, diagnosed through fundus examination, ophthalmic imaging, or ERG. Emerging treatments, including gene therapy, may prevent or stabilise retinopathy. Phenotypic data and natural history of MPS-related retinopathy are thus of paramount importance.

Lack of retinal degeneration in a Dram2 knockout mouse model

Damage-regulated autophagy modulator 2 (DRAM2) is a homologue of the DRAM family protein, which can induce autophagy process. In the retina, DRAM2 is located to the inner segment of photoreceptors, the apical surface of retinal pigment epithelial (RPE) cells, and the lysosome. Pathogenic variants of DRAM2 lead to autosomal recessive Cone-rod dystrophy 21 (CORD21). Cone-rod dystrophy is characterised by primary cone involvement, or sometimes simultaneous cone and rod loss, thus leading to decreased visual acuity, colour vision deficits, photophobia, and decreased sensitivity of the central visual field. However, the mechanisms underlying DRAM2 related retinal diseases remained unclear. To further explore the role of Dram2 in the retina, we generated Dram2 knockout mice (KO) by CRISPR/Cas-9 technology and demonstrated that expression of DRAM2 was abolished in KO retinas. Dram2 ablation failed to manifest any retinal degenerative phenotypes. Dram2 KO did not exhibit visible defect in photo response and the overt structure of the retinas. Immunostaing analysis using antibodies against cone opsins revealed no detectable loss of cone cells. Moreover, no visible change was observed in the expression and localisation of rhodopsin and other membrane disc proteins in Dram2 KO retinas and no gliosis and apoptosis were detected in KO mice. In summary, these data revealed lack of overt retinal degeneration in Dram2 KO model and emphasized the importance of further investigation of the mechanisms underlying Cone-rod dystrophy 21.

First person – Brittany Carr

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Brittany Carr is first author on ‘ prominin-1-null Xenopus laevis develop subretinal drusenoid-like deposits, cone-rod dystrophy and RPE atrophy’, published in JCS. Brittany is an Assistant Professor in the Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada, where her lab investigates frog models of inherited and age-related blindness.

Phenotypic variability of RP1-related inherited retinal dystrophy associated with the c.5797 C > T (p.Arg1933*) variant in the Japanese population

The phenotypes of RP1-related inherited retinal dystrophies (RP1-IRD), causing autosomal dominant (AD) and autosomal recessive (AR) diseases, vary depending on specific RP1 variants. A common nonsense mutation near the C-terminus, c.5797 C > T (p.Arg1933*), is associated with RP1-IRD, but the exact role of this mutation in genotype-phenotype correlation remains unclear. In this study, we retrospectively analyzed patients with RP1-IRD (N = 42) from a single center in Japan. AR RP1-IRD patients with the c.5797 C > T mutation (N = 14) mostly displayed macular dystrophy but rarely retinitis pigmentosa or cone-rod dystrophy. Conversely, AR RP1-IRD patients without the c.5797 C > T mutation, including those with other pathogenic RP1 variants, were mostly diagnosed with severe retinitis pigmentosa. Full-field electroretinograms were significantly better in patients homozygous or compound heterozygous for the c.5797 C > T mutation than in those without this mutation, corresponding to their milder phenotypes. Clinical tests also revealed a slower onset of age and a better mean deviation value with the static visual field in AR RP1-IRD patients with the c.5797 C > T mutation compared to those without. Therefore, the presence of c.5797 C > T may partly account for the phenotypic variety of RP1-IRD and may yield milder phenotypes. These findings may be useful for predicting the prognosis of RP1-IRD patients.

Delayed-onset cord1 progressive retinal atrophy in English Springer Spaniels genetically affected with the RPGRIP1 variant.

Cone-rod dystrophy (cord1) is a form of progressive retinal atrophy. It is linked to an RPGRIP1 genetic variant which is the third most common canine disease variant thus far. While the variant affects various breeds, it is highly prevalent in English Springer Spaniels (ESSs). Yet its clinical and pathological implications remain equivocal. Herein, we study the retinal phenotype in ESSs genetically affected with the RPGRIP1 variant. Over 4 years, 494 ESSs (123 affected) were enrolled. Owner-perceived vision was collected via a questionnaire. Ophthalmic examination included fundus photography. In selected ESSs, retinal function and structure were assessed using electroretinography (ERG, 148 dogs) and optical coherence tomography (OCT, 4 dogs). Ophthalmoscopic changes included peripheral hypo-reflective lesions often with distinct borders progressing centripetally culminating in generalized retinal atrophy. Cross-sectional study revealed declining photopic ERG amplitudes with age in the affected group but not in controls. OCT indicated progressive photoreceptor loss. Despite ophthalmoscopic, ERG, or OCT abnormalities, most affected dogs were not visually impaired per their owners. In a fraction of afflicted ESSs, vision/globe-threatening complications were documented including cataracts, lens luxation, and glaucoma. In ESSs, the RPGRIP1 variant is associated with insidious pathology with delayed-onset visual defects. The subtle phenotype without apparent visual deficit until the final years of life, if at all, may have caused underdiagnosis of cord1. Still, DNA testing remains informative, and ERG and OCT indicate progressive pathology. Peripheral fundus examination and photopic ERG are particularly useful for early detection and monitoring of cord1.

Analysis of Henle's fiber layer and outer retinal layers in cone dystrophy.

To evaluate Henle's Fiber Layer (HFL) thickness and volume parameters in patients with cone photoreceptor atrophy with directional optical coherence tomography (D-OCT). Macular 20°×20° standard and D-OCT images were acquired from patients diagnosed with hereditary cone dystrophy with evident foveal ellipsoid zone defect in OCT, and age-matched healthy controls. Thickness and volume parameters of HFL, outer nuclear layer (ONL) and retinal layers between ellipsoid zone and Bruch membrane complex (EZ-BM) were calculated from manual segmentation through D-OCT images and comparative analysis is performed. Twelve eyes of 6 patients were compared to 12 eyes of 6 age-matched healthy controls (mean age: 29.5±16.6 and 26.6±3.9 years respectively; P=0.162). Patients had lower total HFL volume (0.45±0.03 and 0.85±0.15 mm3; P<0.001) and mean HFL thickness (16.1±1.1 and 30.1±5.3 µm; P<0.001) than healthy controls. Central subfield, parafoveal and perifoveal ETDRS zone HFL parameters in patients were significantly lower than healthy controls. A centrifugal correlation was found between central ONL and the corresponding parafoveal HFL (Spearman's rho: 0.785; P<0.001). HFL assessment might be a useful OCT biomarker in patients with cone photoreceptor atrophy. HFL thinning is observed in foveal, parafoveal and perifoveal areas of patients with cone photoreceptor atrophy, while volume reduction in ONL and EZ-BM components were limited to central and parafoveal zones.

Optical Coherence Tomography Split-Spectrum Amplitude-Decorrelation Optoretinography Detects Early Central Cone Photoreceptor Dysfunction in Retinal Dystrophies.

To investigate if split-spectrum amplitude-decorrelation optoretinography (SSADOR) can detect and measure macular cone dysfunction in inherited retinal dystrophies (IRDs). This study was a case series of participants presenting with various IRD pathologies. Participants were recruited from the Ophthalmic Genetics clinic at the Casey Eye Institute from February to August 2023. Multimodal and SSADOR imaging was obtained in all cases. We recruited nine participants, including four with macular dystrophy, one with fundus flavimaculatus, one with cone dystrophy, and three with retinitis pigmentosa. SSADOR decorrelation maps identified areas of cone functional impairment consistent with disease phenotypes. A correlation between the SSADOR signal and retinal sensitivity measured by microperimetry within the central 20° diameter area was observed. Additionally, SSADOR was able to demonstrate a decreased signal in mild cases when microperimetry measurements were still normal but subtle changes were also apparent on structural OCT. SSADOR is sensitive at detecting functional changes in macular cones, even prior to abnormalities in perimetry testing. We highlight the potential benefits of this innovative technology for the early detection of cone dysfunction and their potential contributions to earlier diagnosis and more accurate monitoring of progression. SSADOR is an innovative technology that detects early macular cone function changes, allowing for early diagnosis and precise monitoring of cone dysfunction progression. By serving as a potential clinical trial endpoint, SSADOR facilitates the translation of scientific findings into practical applications, ultimately improving patient care and outcomes.

Dual CRALBP isoforms unveiled: iPSC-derived retinal modeling and AAV2/5-RLBP1 gene transfer raise considerations for effective therapy

Inherited retinal diseases (IRDs) are characterised by progressive vision loss. There are over 270 causative IRD genes and variants within the same gene can cause clinically distinct disorders. One example is RLBP1 that encodes CRALBP. CRALBP is an essential protein in the rod and cone visual cycles that take place primarily in the retinal pigment epithelium (RPE) but also in Müller cells of the neuroretina. RLBP1 variants lead to three clinical subtypes: Bothnia dystrophy, retinitis punctata albescens and Newfoundland rod-cone dystrophy. We modelled RLBP1-IRD subtypes using patient-specific iPSC-derived RPE and identified pathophysiological markers that served as pertinent therapeutic read-outs. We developed an AAV2/5-mediated gene supplementation strategy and performed a proof-of-concept study in the human models, which was validated in vivo in an Rlbp1-/- murine model. Most importantly, we identified a previously unsuspected smaller CRALBP isoform that is naturally and differentially expressed both in the human and murine retina. This previously unidentified isoform is produced from an alternative methionine initiation site. This work provides further insights into CRALBP expression and RLBP1-associated pathophysiology and raises important considerations for successful gene supplementation therapy.

Cromosome X-linked pigmentary retinosis

To report a clinical case of X-linked Retinitis pigmentosa, highlighting the importance of complementary studies and genetic testing, to the patient and his family, to identify the underlying mutation. A 10-year-old boy was brought to the clinic for refractive changes and difficulty seeing at night (nyctalopia). As a relevant family history, the maternal grandmother had Retinitis pigmentosa and the mother had high myopia (14.0 D). On ophthalmologic examination she had 4/10 corrected vision in both eyes, with moderate to severe myopia. Fundus examination showed diffuse mottled pigmentary changes with multiple yellowish-white dots distributed throughout the midperiphery, with arteriolar attenuation and mild bilateral optic nerve pallor. Autofluorescence showed a hyperautofluorescent ring around the macula and more peripheral hypoautofluorescence. On optical coherence tomography the ellipsoid zone is preserved centrally and these outer layers are thinned towards the periphery. The flash electroretinogram showed a dysfunction of both cones and rods that is not absolute. Regarding the genetic study, a variant in hemizygosis has been identified in the RPGR gene, being this result compatible with X-linked retinitis pigmentosa. In conclusion, it is of high relevance that those patients in whom we suspect a cone and rod dystrophy are extensively studied by a complete ophthalmologic examination, complementary studies, electrophysiologic and fundamentally genetic studies to identify the underlying mutation, since the advent of gene therapy could provide them with a better quality of life.

Diagnosing retinal disorders with artificial intelligence: the role of large language models in interpreting pattern electroretinography data

Aims: To evaluate the diagnostic accuracy of Claude-3, a large language model, in detecting pathological features and diagnosing retinitis pigmentosa and cone-rod dystrophy using pattern electroretinography data. Methods: A subset of pattern electroretinography measurements from healthy individuals, patients with retinitis pigmentosa and cone-rod dystrophy was randomly selected from the PERG-IOBA dataset. The pattern electroretinography and clinical data, including age, gender, visual acuities, were provided to Claude-3 for analysis and diagnostic predictions. The model’s accuracy was assessed in two scenarios: “first choice,” evaluating the accuracy of the primary differential diagnosis and “top 3,” evaluating whether the correct diagnosis was included within the top three differential diagnoses. Results: A total of 46 subjects were included in the study: 20 healthy individuals, 13 patients with retinitis pigmentosa, 13 patients with cone-rod dystrophy. Claude-3 achieved 100% accuracy in detecting the presence or absence of pathology. In the “first choice” scenario, the model demonstrated moderate accuracy in diagnosing retinitis pigmentosa (61.5%) and cone-rod dystrophy (53.8%). However, in the “top 3” scenario, the model’s performance significantly improved, with accuracies of 92.3% for retinitis pigmentosa and 76.9% for cone-rod dystrophy. Conclusion: This is the first study to demonstrate the potential of large language models, specifically Claude-3, in analyzing pattern electroretinography data to diagnose retinal disorders. Despite some limitations, the model’s high accuracy in detecting pathologies and distinguishing between specific diseases highlights the potential of large language models in ocular electrophysiology. Future research should focus on integrating multimodal data, and conducting comparative analyses with human experts.

Mitochondrial functional impairment in ARL3-mutation related rod-cone dystrophy.

Mitochondria are vital for retinal cell function and survival, and there is growing evidence linking mitochondrial dysfunction to retinal degenerations. Although ARL3 mutations have been linked to multiple forms of retinal degeneration, the relationship between ARL3 and mitochondria remains unexplored. Herein, we investigated the effects of ARL3 T31A , ARL3 C118F , and ARL3 T31A/C118F mutations on mitochondrial function in fibroblasts obtained from patients with ARL3-related rod-cone dystrophy. Our findings revealed that these mutations led to a decrease in mitochondrial respiration, an increase in the accumulation mitochondrial reactive oxygen species (ROS), and induction of apoptosis in fibroblasts. Additionally, we conducted a comparative analysis of the effects of ARL3T31A, ARL3C118F, and ARL3T31A/C118F proteins on mitochondria in ARPE-19 cells. Results showed that ARL3T31A and ARL3T31A/C118F not only affected mitochondrial function but also induced apoptosis in ARPE-19 cells. Conversely, ARL3C118F primarily influenced cell apoptosis with minimal effects on mitochondrial function in ARPE-19 cells. Transcriptome analysis further suggested the involvement of respiratory electron transport, response to ROS, and apoptotic signaling pathways in ARL3T31A/C118F cells. Our study demonstrated that ARL3-related mutations play a significant role in the diversity of mitochondrial function, providing novel insights into the functional analysis of ARL3-related mutations.

Promotion of endoplasmic reticulum retrotranslocation by overexpression of E3 ubiquitin-protein ligase synoviolin 1 reduces endoplasmic reticulum stress and preserves cone photoreceptors in cyclic nucleotide-gated channel deficiency.

Cone photoreceptor cyclic nucleotide-gated (CNG) channels play an essential role in phototransduction and cellular Ca2+ homeostasis. Mutations in genes encoding the channel subunits CNGA3 and CNGB3 are associated with achromatopsia, progressive cone dystrophy, and early-onset macular degeneration. Cone loss in patients with achromatopsia and cone dystrophy associated with CNG channel mutations has been documented by optical coherence tomography and in mouse models of CNG channel deficiency. Cone death in CNG channel-deficient retinas involves endoplasmic reticulum (ER) stress-associated apoptosis, dysregulation of cellular/ER Ca2+ homeostasis, impaired protein folding/processing, and impaired ER-associated degradation (ERAD). The E3 ubiquitin-protein ligase synoviolin 1 (SYVN1) is the primary component of the SYVN1/SEL1L ER retrotranslocon responsible for ERAD. Previous studies have shown that manipulations that protect cones and reduce ER stress/cone death in CNG channel deficiency, such as increasing ER Ca2+ preservation or treatment with an ER chaperone, increase the expression of SYVN1 and other components of the ER retrotranslocon. The present work investigated the effects of SYVN1 overexpression. Intraocular injection of AAV5-IRBP/GNAT2-Syvn1 resulted in overexpression of SYVN1 in cones of CNG channel-deficient mice. Following treatment, cone density in Cnga3-/- mice was significantly increased, compared with untreated controls, outer segment localization of cone opsin was improved, and ER stress/apoptotic cell death was reduced. Overexpression of SYVN1 also led to increased expression levels of the retrotranslocon components, degradation in ER protein 1 (DERL1), ERAD E3 ligase adaptor subunit (SEL1L), and homocysteine inducible ER protein with ubiquitin-like domain 1 (HERPUD1). Moreover, overexpression of SYVN1 likely enhanced protein ubiquitination/proteasome degradation in CNG channel-deficient retinas. This study demonstrates the role of SYVN1/ERAD in cone preservation in CNG channel deficiency and supports the strategy of promoting ERAD for cone protection.

Expanding the genetic landscape of Usher syndrome type IV caused by pathogenic ARSG variants.

Usher syndrome (USH) is the most common cause of deafblindness. USH is autosomal recessively inherited and characterized by rod-cone dystrophy or retinitis pigmentosa (RP), often accompanied by sensorineural hearing loss. Variants in >15 genes have been identified as causative for clinically and genetically distinct subtypes. Among the ultra-rare and recently discovered genes is ARSG, coding for the lysosomal sulfatase Arylsulfatase G. This subtype was assigned as "USH IV" with a late onset of RP and usually late-onset progressive SNHL without vestibular involvement. Here, we describe nine new subjects and the clinical description of four cases with the USH IV phenotype bearing seven novel and two known pathogenic variants. Functional experiments indicated the complete loss of sulfatase enzymatic activity upon ectopic expression of mutated ARSG cDNA. Interestingly, we identified a homozygous missense variant, p.(Arg99His), previously described in dogs with neuronal ceroid lipofuscinosis. Our study expands the genetic landscape of ARSG-USH IV and the number of known subjects by more than 30%. These findings highlight that USH IV likely has been underdiagnosed and emphasize the need to test molecularly unresolved subjects with deafblindness syndrome. Finally, testing of ARSG should be considered for the genetic work-up of apparent isolated inherited retinal diseases.

Prominin 1 and Tweety Homology 1 both induce extracellular vesicle formation.

Prominin-1 (Prom1) is a five-transmembrane-pass integral membrane protein that associates with curved regions of the plasma membrane. Prom1 interacts with membrane cholesterol and actively remodels the plasma membrane. Membrane bending activity is particularly evident in photoreceptors, where Prom1 loss-of-function mutations cause failure of outer segment homeostasis, leading to cone-rod retinal dystrophy (CRRD). The Tweety Homology (Ttyh) protein family has been proposed to be homologous to Prominin, but it is not known whether Ttyh proteins have an analogous membrane-bending function. Here, we characterize the membrane-bending activity of human Prom1 and Ttyh1 in native bilayer membranes. We find that Prom1 and Ttyh1 both induce formation of extracellular vesicles (EVs) in cultured mammalian cells and that the EVs produced are physically similar. Ttyh1 is more abundant in EV membranes than Prom1 and produces EVs with membranes that are more tubulated than Prom1 EVs. We further show that Prom1 interacts more stably with membrane cholesterol than Ttyh1 and that this may contribute to membrane bending inhibition in Prom1 EVs. Intriguingly, a loss-of-function mutation in Prom1 associated with CRRD induces particularly stable cholesterol binding. These experiments provide mechanistic insight into Prominin function in CRRD and suggest that Prom and Ttyh belong to a single family of functionally related membrane-bending, EV-generating proteins.

Novel and Previously Known Mutations of the KCNV2 Gene Cause Various Variants of the Clinical Course of Cone Dystrophy with Supernormal Rod Response in Children.

Background/Objectives: Cone dystrophy with supernormal rod response (CDSRR) is a rare autosomal recessive retinal disorder characterized by a delayed and markedly decreased photoreceptor response. In this article, we aim to describe the clinical course and associated molecular findings in children with cone dystrophy with supernormal rod response associated with recessive mutations in the KCNV2 gene, which encodes a subunit (Kv8.2) of the voltage-gated potassium channel. Methods: The genetic testing of two patients included the next-generation sequencing of a retinal dystrophy panel and direct Sanger sequencing to confirm KCNV2 gene variants, in addition to an electroretinogram (ERG) and spectral domain optical coherence tomography (SD-OCT). Results: Cone dystrophy with supernormal rod response is associated with identified variants in the KCNV2 gene. The genetic analysis of the first case identified a compound heterozygous mutation in the KCNV2 gene, including a de novo nonsense duplication at cDNA position 1109, which led to the premature termination of the p.Lys371Ter codon in the second extracellular domain of the protein. Two patients showed changes in the full-field electroretinogram, especially in the first case, which demonstrated a close to supernormal total electroretinogram amplitude. This study increased the range of the KCNV2 mutation database, added an unreported de novo substitution pattern to KCNV2 gene variants, and linked it to the evaluated clinical studies. Conclusions: The initial clinical manifestations were varied, but both patients presented with hypermetropia and slight exotropia. The ERG findings are characteristic of KCNV2 mutations, and patients exhibited an increased b-wave latency in DA3.0 ERG (combined rod-cone response).

A Novel CEP78 Variant Presenting as Cone Dystrophy and Hearing Loss.

Mutations in CEP78 lead to abnormal production of cilia and have previously been identified to cause cone-rod dystrophy (CRD) with progressive sensorineural hearing loss. The authors describe a case of cone dystrophy (CD) with sensorineural hearing loss in a variant that had previously been reported to be of unknown significance and associated with CRD only. This report corroborates the pathogenicity of this variant and highlights that different phenotypes may be associated with one genotype. [Ophthalmic Surg Lasers Imaging Retina 2024;55:XX-XX.].

Rod-sparing in a bardet-biedl syndrome patient with mutations in the ARL6 gene.

Bardet-Biedl Syndrome (BBS) is an autosomal recessive disorder characterized by pleiotropism that affects multiple organ systems. The primary features of BBS include rod-cone dystrophy, renal anomalies, post axial polydactyly, and neurologic deficits. The clinical picture of BBS is extensively heterogenous, with inter and intra familial patients varying in levels of syndromic manifestations and severity of symptoms. In this study we examined a monocular BBS patient who was compound heterozygous for mutations in the ARL6 (BBS3) gene. The patient reported visual complaints consistent with a clinical picture of cone or cone-rod dystrophy. Fundus imaging showed retinal mottling on color photos and a parafoveal hyperfluorescent ring on short wave autofluorescence (SW-AF). Full field electroretinogram (ffERG) revealed normal scotopic step tracings and diminished amplitudes in the photopic steps. This rod-sparing result was consistent with cone-dystrophy and is the first known case of a rod-sparing ffERG phenotype in a BBS patient with mutations in the ARL6 gene. This contributes to the existing phenotype and may potentially contribute to furthering our understanding of BBS pathophysiology.

Establishment of a human induced pluripotent stem cell line (ABi004-A) carrying a compound heterozygous mutation in the KCNV2 gene

Pathogenic variants in the KCNV2 gene can cause a rare retinal dystrophy that can be inherited recessively, known as cone dystrophy with supernormal rod response (CDSRR). CDSRR leads to specific changes in photoreceptors’ electroretinogram response, especially in the rods, poor visual acuity, photophobia, and even maculopathy. The derived iPSC lines from patients with CDSRR may pave the way for apprehension of the pathogenetic mechanism and drug development using in vitro models. PBMCs were established into induced pluripotent stem cells and then characterized by confirming the expression of pluripotency markers, demonstrating the ability to differentiate into the three germ layers, and obtaining normal karyotyping.

Application of Convolutional Gated Recurrent Units U-Net for Distinguishing between Retinitis Pigmentosa and Cone–Rod Dystrophy

Abstract Artificial Intelligence (AI) has gained a prominent role in the medical industry. The rapid development of the computer science field has caused AI to become a meaningful part of modern healthcare. Image-based analysis involving neural networks is a very important part of eye diagnoses. In this study, a new approach using Convolutional Gated Recurrent Units (GRU) U-Net was proposed for the classifying healthy cases and cases with retinitis pigmentosa (RP) and cone–rod dystrophy (CORD). The basis for the classification was the location of pigmentary changes within the retina and fundus autofluorescence (FAF) pattern, as the posterior pole or the periphery of the retina may be affected. The dataset, gathered in the Chair and Department of General and Pediatric Ophthalmology of Medical University in Lublin, consisted of 230 ultra-widefield pseudocolour (UWFP) and ultra-widefield FAF images, obtained using the Optos 200TX device (Optos PLC). The data were divided into three categories: healthy subjects (50 images), patients with CORD (48 images) and patients with RP (132 images). For applying deep learning classification, which rely on a large amount of data, the dataset was artificially enlarged using augmentation involving image manipulations. The final dataset contained 744 images. The proposed Convolutional GRU U-Net network was evaluated taking account of the following measures: accuracy, precision, sensitivity, specificity and F1. The proposed tool achieved high accuracy in a range of 91.00%–97.90%. The developed solution has a great potential in RP diagnoses as a supporting tool.

Novel Variants in ABCA4-Related Retinopathies with Structural Re-Assessment of Variants of Uncertain Significance

Introduction: Conclusive molecular genetic diagnoses in inherited retinal diseases remains a major challenge due to the large number of variants of uncertain significance (VUS) identified in genetic testing. Here, we determined the genotypic and phenotypic spectrum of ABCA4 gene variants in a cohort of Canadian inherited retinal dystrophy subjects. Methods: This retrospective study evaluated 64 subjects with an inherited retinal dystrophy diagnosis with variants in the ABCA4 gene. Pathogenicity of variants was assessed by comparison to genetic databases and in silico modelling. ABCA4 variants classified as VUS were further evaluated using a cryo-electron structural model of the ABCA4 protein to predict impact on protein function and were also assessed for evolutionary conservation. Results: Conclusive disease-causing biallelic ABCA4 variants were detected in 52 subjects with either Stargardt’s disease, cone-rod dystrophy, macular dystrophy, or pattern dystrophy. A further 14 variants were novel comprising 1 nonsense, 1 frameshift, 3 splicing, and 9 missense variants. Based on in silico modelling, protein modelling and evolutionary conservation from human to zebrafish, we re-classified 5 of these as pathogenic and a further 3 as likely pathogenic. We also added to the ABCA4 phenotypic spectrum seen with four known pathogenic variants (c.2161-2A>G; Leu296Cysfs*4; Arg1640Gln; and Pro1380Leu). Conclusions: This study expands the genotypic and phenotypic spectrum of ABCA4 disease-associated variants. By panel-based genetic testing, we identified 14 novel ABCA4 variants of which 8 were determined to be disease-causing or likely disease-causing. These methodologies could circumvent somewhat the need for labour intensive in vitro and in vivo assessments of novel ABCA4 variants.