Nationwide Prevalence of Inherited Retinal Diseases in the Israeli Population.

Importance: Data regarding the prevalence of various inherited retinal diseases (IRDs) are limited and vary across populations; moreover, nationwide prevalence studies may be limited to a specific IRD phenotype, potentially leading to inaccurate prevalence estimations. Therefore, nationwide prevalence data are needed. Objective: To determine the prevalence of 67 IRD phenotypes in the Israeli population. Design, Setting, and Participants: This cohort study collected nationwide data regarding the number of individuals affected with IRD phenotypes assessed in 10 clinical and academic centers in Israel as part of the research activity of the Israeli inherited retinal disease consortium. Data were collected in May 2023 on 9396 individuals residing in Israel who were diagnosed by an ophthalmologist with an IRD using either electroretinography or retinal imaging where included. Individuals with retinal diseases known to have a nonmendelian basis or without a clear genetic basis and those who were reported as deceased at the time of data collection were excluded from this study. Main Outcomes and Measures: Prevalence of 67 IRD phenotypes. Results: Among the 9396 participants in our cohort, the most common IRD in Israel was retinitis pigmentosa with a disease prevalence of approximately 1:2400 individuals, followed by cone-rod dystrophy (approximately 1:14 000), Stargardt disease (approximately 1:16 000), Usher syndrome (approximately 1:16,000), and congenital stationary night blindness (approximately 1:18 000). The prevalence of all IRDs combined was 1:1043 individuals. Conclusions and Relevance: The current study provides large prevalence dataset of 67 IRD phenotypes, some of which are extremely rare, with only a single identified case. This analysis highlights the potential importance of performing additional nationwide prevalence studies to potentially assist with determining the prevalence of IRDs worldwide.

Retinal Disorders.

Retinal disorders caused by genetic or environmental factors cause severe visual impairment and often result in blindness. The past ten years have seen rapid progress in our understanding of the biological basis of these conditions, as well as significant advances towards gene and cell-based therapies. Regulatory challenges remain, but there is reason to hope that creative approaches will lead to safe and effective breakthrough treatments for these conditions in the near future.

Development and Evaluation of a New Self-Administered Near Visual Acuity Chart: Accuracy and Feasibility of Usage.

Background: Visual acuity (VA) assessments are crucial in ophthalmology but traditionally rely on in-clinic evaluations. The emergence of telemedicine has spurred interest in creating dependable self-administered VA tests for use beyond standard clinical environments. This study evaluated the practicality and validity of a self-administered near VA card test against traditional Snellen and Rosenbaum Pocket Vision Screener (RPVS) methods for home monitoring and enhancing clinical workflow. Methods: In a cross-sectional study, a near VA card (Hadassah Self-Visual Acuity Screener (HSVA)) was developed with written and videotaped instructions for self-use. Patients with a minimal best-corrected VA (BCVA) of 1.0 LogMAR in at least one eye were recruited from ophthalmology and optometry clinics. Outcomes included the mean BCVA difference between the self-administered values and those obtained by the examiner, and correlations between BCVA values obtained by the Snellen, RPVS, HSVA, and previous distance BCVA methods according to the patients' electronic medical records. Results: A total of 275 participants (mean age: 42.5 ± 19.4 years; range: 18-89 years; 47% female) were included. Test-retest reliability analysis of the HSVA demonstrated a very good correlation and repeatability (n = 38 patients; Rs = 1.0; p < 0.001). Accuracy analysis revealed the mean LogMAR BCVA values of an additional 237 patients obtained by the Snellen, RPVS, and HSVA methods were similar (p = 0.10). The self-test BCVA results obtained by the HSVA agreed with the masked examiner-tested VA results (n = 67 patients; p = 0.17; Rs = 0.87; ICC = 0.96). Similar results were obtained when stratification by median age (42 years) was performed. Bland-Altman analysis of the HSVA and RPVS methods demonstrated a good agreement. To assess whether the HSVA could predict the VA results in the clinically used charts, multivariate analysis was used and revealed that the HSVA predicted the RPVS results (ß = 0.91; p = 0.001; R2 = 0.88), and the self-test HSVA predicted the Snellen VA results within two lines (ß = 0.93; p = 0.01; R2 = 0.36). Conclusions: The home-based HSVA assessment exhibited high test-retest reliability, accuracy, and alignment with clinical-standard VA tests. Its efficacy in self-testing mirrored examiner-conducted VA assessments and accurately predicted Snellen VA outcomes, indicating the HSVA's suitability for self-monitoring in chronic ocular conditions or when access to conventional examinations is limited. The utility of self-administered VA tests may extend beyond ophthalmology and optometry, potentially benefiting primary care, emergency medicine, and neurology. Further research is needed to explore and validate the practical applications of remote VA testing.

Fine-tuning FAM161A gene augmentation therapy to restore retinal function.

For 15 years, gene therapy has been viewed as a beacon of hope for inherited retinal diseases. Many preclinical investigations have centered around vectors with maximal gene expression capabilities, yet despite efficient gene transfer, minimal physiological improvements have been observed in various ciliopathies. Retinitis pigmentosa-type 28 (RP28) is the consequence of bi-allelic null mutations in the FAM161A, an essential protein for the structure of the photoreceptor connecting cilium (CC). In its absence, cilia become disorganized, leading to outer segment collapses and vision impairment. Within the human retina, FAM161A has two isoforms: the long one with exon 4, and the short one without it. To restore CC in Fam161a-deficient mice shortly after the onset of cilium disorganization, we compared AAV vectors with varying promoter activities, doses, and human isoforms. While all vectors improved cell survival, only the combination of both isoforms using the weak FCBR1-F0.4 promoter enabled precise FAM161A expression in the CC and enhanced retinal function. Our investigation into FAM161A gene replacement for RP28 emphasizes the importance of precise therapeutic gene regulation, appropriate vector dosing, and delivery of both isoforms. This precision is pivotal for secure gene therapy involving structural proteins like FAM161A.

Towards Uncovering the Role of Incomplete Penetrance in Maculopathies through Sequencing of 105 Disease-Associated Genes.

Inherited macular dystrophies (iMDs) are a group of genetic disorders, which affect the central region of the retina. To investigate the genetic basis of iMDs, we used single-molecule Molecular Inversion Probes to sequence 105 maculopathy-associated genes in 1352 patients diagnosed with iMDs. Within this cohort, 39.8% of patients were considered genetically explained by 460 different variants in 49 distinct genes of which 73 were novel variants, with some affecting splicing. The top five most frequent causative genes were ABCA4 (37.2%), PRPH2 (6.7%), CDHR1 (6.1%), PROM1 (4.3%) and RP1L1 (3.1%). Interestingly, variants with incomplete penetrance were revealed in almost one-third of patients considered solved (28.1%), and therefore, a proportion of patients may not be explained solely by the variants reported. This includes eight previously reported variants with incomplete penetrance in addition to CDHR1:c.783G>A and CNGB3:c.1208G>A. Notably, segregation analysis was not routinely performed for variant phasing-a limitation, which may also impact the overall diagnostic yield. The relatively high proportion of probands without any putative causal variant (60.2%) highlights the need to explore variants with incomplete penetrance, the potential modifiers of disease and the genetic overlap between iMDs and age-related macular degeneration. Our results provide valuable insights into the genetic landscape of iMDs and warrant future exploration to determine the involvement of other maculopathy genes.

Loss-of-function variants in UBAP1L cause autosomal recessive retinal degeneration.

PURPOSE: Inherited retinal diseases (IRDs) are a group of monogenic conditions that can lead to progressive blindness. Their missing heritability is still considerable, due in part to the presence of disease genes that await molecular identification. The purpose of this work was to identify novel genetic associations with IRDs. METHODS: Patients underwent a comprehensive ophthalmological evaluation using standard-of-care tests, such as detailed retinal imaging (macular optical coherence tomography and short-wavelength fundus autofluorescence) and electrophysiological testing. Exome and genome sequencing, as well as computer-assisted data analysis were used for genotyping and detection of DNA variants. A minigene-driven splicing assay was performed to validate the deleterious effects of 1 of such variants. RESULTS: We identified 8 unrelated families from Hungary, the United States, Israel, and The Netherlands with members presenting with a form of autosomal recessive and nonsyndromic retinal degeneration, predominantly described as rod-cone dystrophy but also including cases of cone/cone-rod dystrophy. Age of disease onset was very variable, with some patients experiencing first symptoms during their fourth decade of life or later. Myopia greater than 5 diopters was present in 5 of 7 cases with available refractive data, and retinal detachment was reported in 2 cases. All ascertained patients carried biallelic loss-of-function variants in UBAP1L (HGNC: 40028), a gene with unknown function and with homologies to UBAP1, encoding a protein involved in ubiquitin metabolism. One of these pathogenic variants, the intronic NM_001163692.2:c.910-7G>A substitution, was identified in 5 unrelated families. Minigene-driven splicing assays in HEK293T cells confirmed that this DNA change is responsible for the creation of a new acceptor splice site, resulting in aberrant splicing. CONCLUSION: We identified UBAP1L as a novel IRD gene. Although its function is currently unknown, UBAP1L is almost exclusively expressed in photoreceptors and the retinal pigment epithelium, hence possibly explaining the link between pathogenic variants in this gene and an ocular phenotype.

Best Disease: Global Mutations Review, Genotype-Phenotype Correlation, and Prevalence Analysis in the Israeli Population.

Purpose: To review all reported disease-causing mutations in BEST1, perform genotype-phenotype correlation, and estimate disease prevalence in the Israeli population. Methods: Medical records of patients diagnosed with Best disease and allied diseases from nine Israeli medical centers over the past 20 years were collected, as were clinical data including ocular findings, electrophysiology results, and retina imaging. Mutation detection involved mainly whole exome sequencing and candidate gene analysis. Demographic data were obtained from the Israeli Bureau of Statistics (January 2023). A bibliometric study was also conducted to gather mutation data from online sources. Results: A total of 134 patients were clinically diagnosed with Best disease and related conditions. The estimated prevalence of Best disease was calculated to be 1 in 127,000, with higher rates among Arab Muslims (1 in 76,000) than Jews (1 in 145,000). Genetic causes were identified in 76 individuals (57%), primarily showing autosomal-dominant inheritance due to BEST1 mutations (58 patients). Critical conserved domains were identified consisting of a high percentage of dominant missense mutations, primarily in transmembrane domains and the intracellular region (Ca2+ binding domain) of the BEST1 protein. Conclusions: This study represents the largest cohort of patients with Best disease reported in Israel and globally. The prevalence in Israel is akin to that in Denmark but is lower than that in the United States. Critical conserved domains within the BEST1 protein are pivotal for normal functioning, and even minor missense alterations in these areas lead to a dominant disease manifestation. Genetic testing is indispensable as the gold standard for Best disease diagnosis due to the variable clinical presentation of the disease.

A pipeline for identifying guide RNA sequences that promote RNA editing of nonsense mutations that cause inherited retinal diseases.

Adenosine deaminases acting on RNA (ADARs) are endogenous enzymes catalyzing the deamination of adenosines to inosines, which are then read as guanosines during translation. This ability to recode makes ADAR an attractive therapeutic tool to edit genetic mutations and reprogram genetic information at the mRNA level. Using the endogenous ADARs and guiding them to a selected target has promising therapeutic potential. Indeed, different studies have reported several site-directed RNA-editing approaches for making targeted base changes in RNA molecules. The basic strategy has been to use guide RNAs (gRNAs) that hybridize and form a double-stranded RNA (dsRNA) structure with the desired RNA target because of ADAR activity in regions of dsRNA formation. Here we report on a novel pipeline for identifying disease-causing variants as candidates for RNA editing, using a yeast-based screening system to select efficient gRNAs for editing of nonsense mutations, and test them in a human cell line reporter system. We have used this pipeline to modify the sequence of transcripts carrying nonsense mutations that cause inherited retinal diseases in the FAM161A, KIZ, TRPM1, and USH2A genes. Our approach can serve as a basis for gene therapy intervention in knockin mouse models and ultimately in human patients.

Whole exome sequencing of 491 individuals with inherited retinal diseases reveals a large spectrum of variants and identification of novel candidate genes.

BACKGROUND: Inherited retinal diseases (IRDs) include a range of vision loss conditions caused by variants in different genes. The clinical and genetic heterogeneity make identification of the genetic cause challenging. Here, a cohort of 491 unsolved cases from our cohort of Israeli and Palestinian families with IRDs underwent whole exome sequencing (WES), including detection of CNVs as well as single nucleotide variants (SNVs). METHODS: All participants underwent clinical examinations. Following WES on DNA samples by 3 billion, initial SNV analysis was performed by 3 billion and SNV and CNV analysis by Franklin Genoox. The CNVs indicated by the programme were confirmed by PCR followed by gel electrophoresis. RESULTS: WES of 491 IRD cases revealed the genetic cause of disease in 51% of cases, of which 11% were due wholly or in part to CNVs. In two cases, we clarified previously incorrect or unclear clinical diagnoses. This analysis also identified ESRRB and DNM1 as potential novel genes. CONCLUSION: This analysis is the most extensive one to include CNVs to examine IRD causing genes in the Israeli and Palestinian populations. It has allowed us to identify the causative variant of many patients with IRDs including ones with unclear diagnoses and potential novel genes.

Achromatopsia-Visual Cortex Stability and Plasticity in the Absence of Functional Cones.

Purpose: Achromatopsia is a rare inherited disorder rendering retinal cone photoreceptors nonfunctional. As a consequence, the sizable foveal representation in the visual cortex is congenitally deprived of visual input, which prompts a fundamental question: is the cortical representation of the central visual field in patients with achromatopsia remapped to take up processing of paracentral inputs? Such remapping might interfere with gene therapeutic treatments aimed at restoring cone function. Methods: We conducted a multicenter study to explore the nature and plasticity of vision in the absence of functional cones in a cohort of 17 individuals affected by autosomal recessive achromatopsia and confirmed biallelic disease-causing CNGA3 or CNGB3 mutations. Specifically, we tested the hypothesis of foveal remapping in human achromatopsia. For this purpose, we applied two independent functional magnetic resonance imaging (fMRI)-based mapping approaches, i.e. conventional phase-encoded eccentricity and population receptive field mapping, to separate data sets. Results: Both fMRI approaches produced the same result in the group comparison of achromatopsia versus healthy controls: sizable remapping of the representation of the central visual field in the primary visual cortex was not apparent. Conclusions: Remapping of the cortical representation of the central visual field is not a general feature in achromatopsia. It is concluded that plasticity of the human primary visual cortex is less pronounced than previously assumed. A pretherapeutic imaging workup is proposed to optimize interventions.

KCNV2-associated retinopathy: genotype-phenotype correlations - KCNV2 study group report 3.

BACKGROUND/AIMS: To investigate genotype-phenotype associations in patients with KCNV2 retinopathy. METHODS: Review of clinical notes, best-corrected visual acuity (BCVA), molecular variants, electroretinography (ERG) and retinal imaging. Subjects were grouped according to the combination of KCNV2 variants-two loss-of-function (TLOF), two missense (TM) or one of each (MLOF)-and parameters were compared. RESULTS: Ninety-two patients were included. The mean age of onset (mean±SD) in TLOF (n=55), TM (n=23) and MLOF (n=14) groups was 3.51±0.58, 4.07±2.76 and 5.54±3.38 years, respectively. The mean LogMAR BCVA (±SD) at baseline in TLOF, TM and MLOF groups was 0.89±0.25, 0.67±0.38 and 0.81±0.35 for right, and 0.88±0.26, 0.69±0.33 and 0.78±0.33 for left eyes, respectively. The difference in BCVA between groups at baseline was significant in right (p=0.03) and left eyes (p=0.035). Mean outer nuclear layer thickness (±SD) at baseline in TLOF, MLOF and TM groups was 37.07±15.20 µm, 40.67±12.53 and 40.38±18.67, respectively, which was not significantly different (p=0.85). The mean ellipsoid zone width (EZW) loss (±SD) was 2051 µm (±1318) for patients in the TLOF, and 1314 µm (±965) for MLOF. Only one patient in the TM group had EZW loss at presentation. There was considerable overlap in ERG findings, although the largest DA 10 ERG b-waves were associated with TLOF and the smallest with TM variants. CONCLUSIONS: Patients with missense alterations had better BCVA and greater structural integrity. This is important for patient prognostication and counselling, as well as stratification for future gene therapy trials.

Current Status of Clinical Trials Design and Outcomes in Retinal Gene Therapy.

With the rapid expansion of methods encompassed by the term gene therapy, new trials exploring the safety and efficacy of these methods are initiated more frequently. As a result, important questions arise pertaining the design of these trials and patient participation. One of the most important aspects of any clinical trial is the ability to measure the trial's outcome in a manner that will reflect the effect of the treatment and allow its quantification, whether the trial is aimed at preservation or restoration of retinal cells (photoreceptors and others), vision, or both. Here we will review the existing methods for quantification of trial outcomes, stressing the importance of assessing the participant's visual function and not just visual acuity. We will also describe the key considerations in trial design. Finally, as patient safety remains the primary concern in any trial participation, we will outline the key principles in that regard.

Gene augmentation therapy attenuates retinal degeneration in a knockout mouse model of Fam161a retinitis pigmentosa.

Photoreceptor cell degeneration and death is the major hallmark of a wide group of human blinding diseases including age-related macular degeneration and inherited retinal diseases such as retinitis pigmentosa. In recent years, inherited retinal diseases have become the "testing ground" for novel therapeutic modalities, including gene and cell-based therapies. Currently there is no available treatment for retinitis pigmentosa caused by FAM161A biallelic pathogenic variants. In this study, we injected an adeno-associated virus encoding for the longer transcript of mFam161a into the subretinal space of P24-P29 Fam161a knockout mice to characterize the safety and efficacy of gene augmentation therapy. Serial in vivo assessment of retinal function and structure at 3, 6, and 8 months of age using the optomotor response test, full-field electroretinography, fundus autofluorescence, and optical coherence tomography imaging as well as ex vivo quantitative histology and immunohistochemical studies revealed a significant structural and functional rescue effect in treated eyes accompanied by expression of the FAM161A protein in photoreceptors. The results of this study may serve as an important step toward future application of gene augmentation therapy in FAM161A-deficient patients by identifying a promising isoform to rescue photoreceptors and their function.

Factors Affecting Readthrough of Natural Versus Premature Termination Codons.

Nonsense mutations occur within the open-reading frame of a gene resulting in a premature termination codon (PTC). PTC-containing mRNAs can either be degeraded or cause premature translation termination producing a truncated protein that can be either nonfunctional or toxic. Translational readthrough inducing drugs (TRIDs) are small molecules that are able to induce readthrough, resulting in the restoration of full-length protein expression. The re-expressed proteins usually harbor a missense change. The effciency of individual TRIDs is variable and varies between different genes and even different nonsense mutations in the same gene. This review summarizes factors, including the sequences located upstream and downstream the disease-causing mutation and the type of PTC, affecting the translational readthrough process by modulating the type of amino acid insertion and the efficiency of the process during readthrough following TRIDs treatments.

Exonic Variants that Affect Splicing - An Opportunity for "Hidden" Mutations Causing Inherited Retinal Diseases.

Inherited retinal diseases (IRDs) are an extremely diverse group of ocular disorders characterized by progressive loss of photoreceptors leading to blindness. So far, pathogenic variants in over 300 genes are reported to structurally and functionally affect the retina resulting in visual impairment. Around 15% of all IRD mutations are known to affect an essential regulatory mechanism, pre-mRNA splicing, which contributes to the transcriptomic diversity. These variants disrupt potential donor and acceptor splice sites as well as other crucial cis-acting elements resulting in aberrant splicing. One group of these elements, the exonic splicing enhancers (ESEs), are involved in promoting exon definition and are likely to harbor "hidden" mutations since sequence-analyzing pipelines cannot identify them efficiently. The main focus of this review is to discuss the molecular mechanisms behind various exonic variants affecting splice sites and ESEs that lead to impaired splicing which in turn result in an IRD pathology.

Morphological and Functional Comparison of Mice Models for Retinitis Pigmentosa.

Retinitis pigmentosa (RP) is the predominant form of inherited retinal degenerations (IRDs) caused by abnormalities and loss of photoreceptor cells ensuing diminishment of vision. RP is a heterogenous genetic disorder associated with mutations in over 80 genes, showing various inheritance patterns. Laboratory mouse models are important for our understanding of disease mechanisms, modifier effects, and development of therapeutic modalities. In this review, we have summarized a comprehensive comparison of our previously reported Fam161a knockout (KO) mouse model with other well-studied RP mouse models, Fam161aGT/GT, Pde6brd1, Nr2e3rd7, Rpgrrd9, and Pde6brd10 using structural and functional analysis of the retina. Fam161atm1b/tm1b mouse models are important for developing novel therapies and mainly AAV-based gene therapy and translational read-through-inducing drugs.

Seeing color following gene augmentation therapy in achromatopsia.

How will people who spent their visual lives with only rods respond to cone function restoration? Will they be able suddenly see the colors of the rainbow? CNGA3-achromatopsia is a congenital hereditary disease in which cone dysfunction leads patients to have rod photoreceptor-driven vision only in daylight,1,2,3,4 seeing the world in blurry shades of gray.5,6 We studied color perception in four CNGA3-achromatopsia patients following monocular retinal gene augmentation therapy.7,8,9 Following treatment, although some cortical changes were reported,3,4 patients did not report a dramatic change in their vision.3,9 However, in accordance with the fact that sensitivity of rods and cones is most different at long wavelengths, they consistently reported seeing red objects on dark backgrounds differently than they did before surgery.3 Because clinical color assessments failed to find any indication of color vision, we conducted a gamut of tailored tests to better define patients' descriptions. We evaluated patients' perceived lightness of different colors, color detection, and saliency, comparing their treated with their untreated eyes. Although the perceived lightness of different colors was generally similar between the eyes and matched a rod-input model, patients could detect a colored stimulus only in their treated eyes. In a search task, long response times, which were further extended with array size, suggested low saliency. We suggest that treated CNGA3-achromatopsia patients can perceive a stimulus's color attribute, although in a manner that is different and very limited compared with sighted individuals. We discuss the retinal and cortical obstacles that might explain this perceptual gap.

Genetic causes of inherited retinal diseases among Israeli Jews of Ethiopian ancestry.

Purpose: This study sought to describe the phenotype frequency and genetic basis of inherited retinal diseases (IRDs) among a nationwide cohort of Israeli Jewish patients of Ethiopian ancestry. Methods: Patients' data-including demographic, clinical, and genetic information-were obtained through members of the Israeli Inherited Retinal Disease Consortium (IIRDC). Genetic analysis was performed by either Sanger sequencing for founder mutations or next-generation sequencing (targeted next-generation sequencing or whole-exome sequencing). Results: Forty-two patients (58% female) from 36 families were included, and their ages ranged from one year to 82 years. Their most common phenotypes were Stargardt disease (36%) and nonsyndromic retinitis pigmentosa (33%), while their most common mode of inheritance was autosomal recessive inheritance. Genetic diagnoses were ascertained for 72% of genetically analyzed patients. The most frequent gene involved was ABCA4. Overall, 16 distinct IRD mutations were identified, nine of which are novel. One of them, ABCA4-c.6077delT, is likely a founder mutation among the studied population. Conclusions: This study is the first to describe IRDs' phenotypic and molecular characteristics in the Ethiopian Jewish community. Most of the identified variants are rare. Our findings can help caregivers with clinical and molecular diagnosis and, we hope, enable adequate therapy in the near future.

Survival of Neural Progenitors Derived from Human Embryonic Stem Cells Following Subretinal Transplantation in Rodents.

Purpose: To examine the survival of neural progenitors (NPs) cells derived from human embryonic stem cells (hESCs) following subretinal (SR) transplantation in rodents. Methods: hESCs engineered to express enhanced green fluorescent protein (eGFP) were differentiated in vitro toward an NP fate using a 4-week protocol. State of differentiation was characterized by quantitative-PCR. NPs in suspension (75,000/µl) were transplanted to the SR-space of Royal College of Surgeons (RCS) rats (n = 66), nude-RCS rats (n = 18), and NOD scid gamma (NSG) mice (n = 53). Success of engraftment was determined at 4 weeks post-transplant by in vivo visualization of GFP-expression using a properly filtered rodent fundus camera. Transplanted eyes were examined in vivo at set time points using the fundus camera, and in select cases, by optical coherence tomography imaging, and after enucleation, by retinal histology and immunohistochemistry. Results: In RCS rats, cell rejection was observed in 29% of eyes at 6 weeks, rising to 92% at 8 weeks. In the more immunodeficient nude-RCS rats, the rejection rate was still high reaching 62% of eyes at 6 weeks post-transplant. Following transplantation in highly immunodeficient NSG mice, survival of the hESC-derived NPs was much improved, with 100% survival at 9 weeks and 72% at 20 weeks. A small number of eyes that were followed past 20 weeks showed survival also at 22 weeks. Conclusions: Immune status of recipient animals influences transplant survival. Highly immunodeficient NSG mice provide a better model for studying long-term survival, differentiation, and possible integration of hESC-derived NPs. Clinical Trial Registration numbers: NCT02286089, NCT05626114.

Homozygous Knockout of Cep250 Leads to a Relatively Late-Onset Retinal Degeneration and Sensorineural Hearing Loss in Mice.

Purpose: Usher syndrome (USH) is the most common syndromic inherited retinal disease, causing retinitis pigmentosa and sensorineural hearing loss. We reported previously that a nonsense mutation in the centrosome-associated protein CEP250 gene (encoding C-Nap1) causes atypical USH in patients of Iranian Jewish origin. To better characterize CEP250, we aimed to generate and study a knockout (KO) mouse model for Cep250. Methods: Mice heterozygous for a "knockout-first" Cep250 construct were generated and bred with Cre recombinase mice to generate the null allele and produce homozygous Cep250 KO mice. Retinal function was evaluated by full-field electroretinography (ffERG) at variable ages, and retinal structure changes were examined using histological analysis. Hearing thresholds were detected using auditory brainstem response (ABR) at the age of 20 months. Results: The Cep250 KO mouse model was generated by activating a construct harboring a deletion of exons 6 and 7. At 6 months, the ffERG was normal, but it decreased gradually with age. For both photopic and scotopic ffERG responses, very low amplitudes were evident at 20 months. Histological analysis confirmed late-onset retinal degeneration. ABR tests illustrated that hearing threshold significantly increased at the age of 20 months. Conclusions: Although most USH animal models have normal retinal function and structure, the Cep250 KO mouse model shows both retinal degeneration and hearing loss with a relatively late age of onset. This model may shed more light on CEP250-associated retinal and hearing deficits and represents an efficient platform for the development of treatment modalities for USH. Translational Relevance: Our study demonstrates better understanding of Cep250-associated retinal and hearing disease in a mouse model and may help in developing more efficient gene therapy modalities.