Genetic testing and diagnosis of inherited retinal diseases

Voretigene neparvovec for inherited retinal dystrophy due to RPE65 mutations: a scoping review of eligibility and treatment challenges from clinical trials to real practice

Biallelic mutations in the RPE65 gene affect nearly 8% of Leber Congenital Amaurosis and 2% of Retinitis Pigmentosa cases. Voretigene neparvovec (VN) is the first gene therapy approach approved for their treatment. To date, real life experience has demonstrated functional improvements following VN treatment, which are consistent with the clinical trials outcomes. However, there is currently no consensus on the characteristics for eligibility for VN treatment. We reviewed relevant literature to explore whether recommendations on patient eligibility can be extrapolated following VN marketing. We screened 166 papers through six research questions, following scoping reviews methodology, to investigate: (1) the clinical and genetic features considered in VN treatment eligibility; (2) the psychophysical tests and imaging modalities used in the pre-treatment and follow-up; (3) the potential correlations between visual function and retinal structure that can be used to define treatment impact on disease progression; (4) retinal degeneration; (5) the most advanced testing modalities; and (6) the impact of surgical procedure on treatment outcomes. Current gaps concerning patients' eligibility in clinical settings, such as pre-treatment characteristics and outcomes are not consistently reported across the studies. No upper limit of retinal degeneration can be defined as the univocal factor in patient eligibility, although evidence suggested that the potential for function rescue is related to the preservation of photoreceptors before treatment. In general, paediatric patients retain more viable cells, present a less severe disease stage and show the highest potential for improvements, making them the most suitable candidates for treatment.

Impacts of X-linked Retinitis Pigmentosa and Patient Pathways in European Countries: Results from the Cross-sectional EXPLORE XLRP-1 Physician Survey

INTRODUCTION

X-linked retinitis pigmentosa (XLRP) is a rare, incurable, vision-threatening, genetic disease. In this study, we aimed to reveal the real-world burden of this disease from the viewpoint of retina specialists and geneticists involved directly in XLRP care and to identify unique insights that may not otherwise be available through typical clinical studies or health economic research.

METHODS

In this exploratory, cross-sectional study (EXPLORE XLRP-1), retina specialists (n = 20) and geneticists (n = 5) in France, Germany, Italy, Spain, and the UK provided anonymized insights on their experiences managing patients with XLRP (n = 80) via an online survey and 60-min telephone interview.

RESULTS

Survey respondents reported that patient independence decreased over time, where 37% of patients were considered "completely autonomous" at diagnosis versus 23% at the last consultation. At their last visit, 45% of patients were active in the workforce; 67% (12/18) of "completely autonomous" patients had active working status compared with 13% (1/8) of "completely dependent" patients. The average time from onset of symptoms to diagnosis was 4 years and varied among countries. In 78% of patients, XLRP was confirmed by genetic testing, the rate of which varied among countries (range, 50-94%), taking up to 6 months to receive results. Specialists identified unmet needs in XLRP management including more standardized assessments of quality of life (QoL) as well as easier and earlier access to specialists, genetic testing, patient support programs, and effective treatment options.

CONCLUSIONS

The diagnosis, genetic testing, and management pathways among patients with XLRP can vary considerably. There is a need for more standardized diagnosis and management pathways, and QoL assessments, due to the major impact that XLRP has on patients' lives.

A Comprehensive Review of Ocular Manifestations in Systemic Diseases

Ocular manifestations often serve as critical indicators of underlying systemic diseases, providing valuable diagnostic and prognostic information. This comprehensive review aims to elucidate the complex interplay between ocular symptoms and systemic conditions, emphasising the importance of early recognition and interdisciplinary collaboration in patient management. The review encompasses various systemic diseases, including cardiovascular, autoimmune, infectious, neurological, endocrine, hematologic, genetic, dermatologic, gastrointestinal, hepatic, renal, and connective tissue disorders, highlighting their specific ocular manifestations. Diagnostic approaches, including ophthalmologic examination techniques, imaging modalities, and laboratory tests, are discussed to enhance diagnostic accuracy. Furthermore, the review outlines current management and treatment strategies, emphasising the need for a multidisciplinary approach to care. Emerging therapies and future research directions are also explored, underscoring the necessity of continued innovation in this field. This review aims to improve clinical practices, promote integrative healthcare, and ultimately enhance patient outcomes by providing a detailed overview of ocular manifestations in systemic diseases.

Clinical and analytical validation of an 82-gene comprehensive genome-profiling panel for identifying and interpreting variants responsible for inherited retinal dystrophies

Inherited retinal dystrophies comprise a clinically complex and heterogenous group of diseases characterized by visual impairment due to pathogenic variants of over 300 different genes. Accurately identifying the causative gene and associated variant is crucial for the definitive diagnosis and subsequent selection of precise treatments. Consequently, well-validated genetic tests are required in the clinical practice. Here, we report the analytical and clinical validation of a next-generation sequencing targeted gene panel, the PrismGuide IRD Panel System. This system enables comprehensive genome profiling of 82 genes related to inherited retinal dystrophies. The PrismGuide IRD Panel System demonstrated 100% (n = 43) concordance with Sanger sequencing in detecting single-nucleotide variants, small insertions, and small deletions in the target genes and also in assessing their zygosity. It also identified copy-number loss in four out of five cases. When assessing precision, we evaluated the reproducibility of variant detection with 2,160 variants in 144 replicates and found 100% agreement in terms of single-nucleotide variants (n = 1,584) and small insertions and deletions (n = 576). Furthermore, the PrismGuide IRD Panel System generated sufficient read depth for variant calls across the purine-rich and highly repetitive open-reading frame 15 region of RPGR and detected all five variants tested. These results show that the PrismGuide IRD Panel System can accurately and consistently detect single-nucleotide variants and small insertions and deletions. Thus, the PrismGuide IRD Panel System could serve as useful tool that is applicable in clinical practice for identifying the causative genes based on the detection and interpretation of variants in patients with inherited retinal dystrophies and can contribute to a precise molecular diagnosis and targeted treatments.

Investigating G-quadruplex structures in RPGR gene: Implications for understanding X-linked retinal degeneration

Aims

This pilot study investigates the potential pathogenic role of G-quadruplex (G4) structures in RPGR-associated retinal degeneration, starting from a case of suspected X-linked form affected family. We hypothesize that the stabilization of these structures might alter DNA replication and transcription, inducing genetic instability and influencing gene expression.

Main methods

We conducted whole genome amplification experiments and next-generation sequencing to detect the blockade of polymerase activity by G4 structures. Our specific focus was the RPGR gene, which hosts a high concentration of predicted G4-forming motifs and is implicated in most X-linked retinal degeneration cases. To understand the potential interference of G4 structures, we applied computational and 3D molecular modeling to visualize interferences in DNA replication and transcription regulation.

Key findings

Our data confirmed the obstruction of DNA polymerase enzymes by G4 structures, particularly when stabilized by the compound pyridostatin. This obstruction was evident in the reduced amplification of RPGR gene regions and a shift in the start/end sites of putative G4 motifs. Moreover, the modeling indicated a potential disruption of critical promoter elements and RNA polymerase binding, which could drastically alter gene expression.

Significance

Our findings suggest that G4 formation in the RPGR gene could lead to genetic instability and affect the expression of RPGR, contributing to retinal dystrophy. Moreover, this study underscores the broader implications of G4 structures in other genetic disorders. Improved understanding of G4 structures could reveal novel therapeutic targets to combat genetic disorders, promoting the advancement of personalized medicine and precision health.

Patient experiences and perceived value of genetic testing in inherited retinal diseases: a cross-sectional survey

This study evaluated patient experiences with genetic testing for inherited retinal diseases (IRDs) and the association between underlying knowledge, testing outcomes, and the perceived value of the results. An online survey was distributed to adults with IRDs and parents/guardians of dependents with IRDs who had had genetic testing. Data included details of genetic testing, pre- and post- test perceptions, Decision Regret Scale, perceived value of results, and knowledge of gene therapy. Of 135 responses (85% from adults with IRDs), genetic testing was primarily conducted at no charge through public hospitals (49%) or in a research setting (30%). Key motivations for genetic testing were to confirm IRD diagnosis and to contribute towards research. Those who had received a genetic diagnosis (odds ratio: 6.71; p < 0.001) and those self-reported to have good knowledge of gene therapy (odds ratio: 2.69; p = 0.018) were more likely to have gained confidence in managing their clinical care. For over 80% of respondents, knowing the causative gene empowered them to learn more about their IRD and explore opportunities regarding clinical trials. Key genetic counselling information needs include resources for family communications, structured information provision, and ongoing genetic support, particularly in the context of emerging ocular therapies, to enhance consistency in information uptake.

PdmIRD: missense variants pathogenicity prediction for inherited retinal diseases in a disease-specific manner

Accurate discrimination of pathogenic and nonpathogenic variation remains an enormous challenge in clinical genetic testing of inherited retinal diseases (IRDs) patients. Computational methods for predicting variant pathogenicity are the main solutions for this dilemma. The majority of the state-of-the-art variant pathogenicity prediction tools disregard the differences in characteristics among different genes and treat all types of mutations equally. Since missense variants are the most common type of variation in the coding region of the human genome, we developed a novel missense mutation pathogenicity prediction tool, named Prediction of Deleterious Missense Mutation for IRDs (PdmIRD) in this study. PdmIRD was tailored for IRDs-related genes and constructed with the conditional random forest model. Population frequencies and a newly available prediction tool were incorporated into PdmIRD to improve the performance of the model. The evaluation of PdmIRD demonstrated its superior performance over nonspecific tools (areas under the curves, 0.984 and 0.910) and an existing eye abnormalities-specific tool (areas under the curves, 0.975 and 0.891). We also demonstrated the submodel that used a smaller gene panel further slightly improved performance. Our study provides evidence that a disease-specific model can enhance the prediction of missense mutation pathogenicity, especially when new and important features are considered. Additionally, this study provides guidance for exploring the characteristics and functions of the mutated proteins in a greater number of Mendelian disorders.

The Role of the Ophthalmic Genetics Multidisciplinary Team in the Management of Inherited Retinal Degenerations-A Case-Based Review

(1) Background: Inherited retinal degenertions are rare conditions which may have a dramatic impact on the daily life of those affected and how they interact with their environment. Coordination of clinical services via an ophthalmic genetics multidisciplinary team (OG-MDT) allows better efficiency of time and resources to reach diagnoses and facilitate patient needs. (2) Methods: This clinical case series was conducted by a retrospective review of patient records for patients enrolled in the Target 5000 programme and managed by the OG-MDT, at the Mater Hospital Dublin, Ireland (n = 865) (3) Results: Herein we describe clinical cases and how the use of the OG-MDT optimizes care for isolated and syndromic IRD pedigrees. (4) Conclusions: this paper demonstrates the benefits of an OG-MDT to patients with IRDs resulting in the holistic resolution of complex and syndromic cases. Furthermore, we demonstrate that this format can be adopted/developed by similar centres around the world, bringing with it the myriad benefits.

Combining a prioritization strategy and functional studies nominates 5'UTR variants underlying inherited retinal disease

BACKGROUND

5' untranslated regions (5'UTRs) are essential modulators of protein translation. Predicting the impact of 5'UTR variants is challenging and rarely performed in routine diagnostics. Here, we present a combined approach of a comprehensive prioritization strategy and functional assays to evaluate 5'UTR variation in two large cohorts of patients with inherited retinal diseases (IRDs).

METHODS

We performed an isoform-level re-analysis of retinal RNA-seq data to identify the protein-coding transcripts of 378 IRD genes with highest expression in retina. We evaluated the coverage of their 5'UTRs by different whole exome sequencing (WES) kits. The selected 5'UTRs were analyzed in whole genome sequencing (WGS) and WES data from IRD sub-cohorts from the 100,000 Genomes Project (n = 2397 WGS) and an in-house database (n = 1682 WES), respectively. Identified variants were annotated for 5'UTR-relevant features and classified into seven categories based on their predicted functional consequence. We developed a variant prioritization strategy by integrating population frequency, specific criteria for each category, and family and phenotypic data. A selection of candidate variants underwent functional validation using diverse approaches.

RESULTS

Isoform-level re-quantification of retinal gene expression revealed 76 IRD genes with a non-canonical retina-enriched isoform, of which 20 display a fully distinct 5'UTR compared to that of their canonical isoform. Depending on the probe design, 3-20% of IRD genes have 5'UTRs fully captured by WES. After analyzing these regions in both cohorts, we prioritized 11 (likely) pathogenic variants in 10 genes (ARL3, MERTK, NDP, NMNAT1, NPHP4, PAX6, PRPF31, PRPF4, RDH12, RD3), of which 7 were novel. Functional analyses further supported the pathogenicity of three variants. Mis-splicing was demonstrated for the PRPF31:c.-9+1G>T variant. The MERTK:c.-125G>A variant, overlapping a transcriptional start site, was shown to significantly reduce both luciferase mRNA levels and activity. The RDH12:c.-123C>T variant was found in cis with the hypomorphic RDH12:c.701G>A (p.Arg234His) variant in 11 patients. This 5'UTR variant, predicted to introduce an upstream open reading frame, was shown to result in reduced RDH12 protein but unaltered mRNA levels.

CONCLUSIONS

This study demonstrates the importance of 5'UTR variants implicated in IRDs and provides a systematic approach for 5'UTR annotation and validation that is applicable to other inherited diseases.

Genetic testing and gene therapy in retinal diseases: Knowledge and perceptions of optometrists in Australia and New Zealand

With advances in gene-based therapies for heritable retinal diseases, primary eye care clinicians should be informed on ocular genetics topics. This cross-sectional survey evaluated knowledge, attitudes, and concerns regarding genetic testing and gene therapy for retinal diseases among optometrists in Australia and New Zealand. Survey data included practitioner background, attitudes and practices towards genetic testing for monogenic inherited retinal disease (IRDs) and age-related macular degeneration, and knowledge of ocular genetics and gene therapy. Responses were received from 516 optometrists between 1 April and 31 December 2022. Key perceived barriers to accessing genetic testing were lack of clarity on referral pathways (81%), cost (65%), and lack of treatment options if a genetic cause is identified (50%). Almost all respondents (98%) believed that ophthalmologists should initiate genetic testing for IRDs and fewer understood the role of genetic counsellors and clinical geneticists. This study found that optometrists in Australia and New Zealand have a high level of interest in ocular genetics topics. However, knowledge gaps include referral pathways and awareness of genetic testing and gene therapy outcomes. Addressing perceived barriers to access and promoting sharing of knowledge between interdisciplinary networks can set the foundation for genetic education agendas in primary eye care.

Gene Therapy for Inherited Retinal Diseases: From Laboratory Bench to Patient Bedside and Beyond

This comprehensive review provides a thorough examination of inherited retinal diseases (IRDs), encompassing their classification, genetic underpinnings, and the promising landscape of gene therapy trials. IRDs, a diverse group of genetic conditions causing vision loss through photoreceptor cell death, are explored through various angles, including inheritance patterns, gene involvement, and associated systemic disorders. The focal point is gene therapy, which offers hope for halting or even reversing the progression of IRDs. The review highlights ongoing clinical trials spanning retinal cell replacement, neuroprotection, pharmacological interventions, and optogenetics. While these therapies hold tremendous potential, they face challenges like timing optimization, standardized assessment criteria, inflammation management, vector refinement, and raising awareness among vision scientists. Additionally, translating gene therapy success into widespread adoption and addressing cost-effectiveness are crucial challenges to address. Continued research and clinical trials are essential to fully harness gene therapy's potential in treating IRDs and enhancing the lives of affected individuals.

The genetic counselor workforce in inherited retinal disease clinics: a descriptive assessment

BACKGROUND

Genetic counselors (GCs) have practiced in Inherited Retinal Disease (IRD) clinics for several decades. In this small subspecialty of genetic counseling, GCs are critical for patient understanding of genetic information, which can have prognostic, systemic, family planning and therapeutic implications. Recently, both access to genetic testing for IRDs and the number of genes associated with IRDs (>350) has increased dramatically. However, the practice models and roles of IRD GCs have not been previously described.

MATERIALS AND METHODS

GCs working in academic IRD clinics were surveyed to assess their experience, clinical practices, and roles performed. The collected data was compared to the broader genetic counseling profession and to other specialties using publicly available data on GC professional practices.

RESULTS

While roles of IRD GCs were overlapping with those of the overall genetic counseling profession, all survey respondents reported diverse roles that included both clinical and non-clinical duties, spending up to half their time on research and educational responsibilities. Most respondents (89%) felt that their clinic's MD to GC ratio was too high, while clinical load varied. IRD GCs report varying degrees of prior genetic counseling and ophthalmology-specific experience but unanimously desire additional subspecialty-specific training.

CONCLUSIONS

This descriptive assessment of a small subspecialty suggests a need for growth in the number of GCs practicing in IRD clinics and could help to inform development of new GC positions in IRD centers. It also highlights the desire for additional GC-specific education and may be relevant to curriculum development within GC programs.

Microbiome and Inherited Retinal Degenerations

Inherited retinal degenerations (IRDs) represent a genetically and clinically heterogeneous group of progressive and visually debilitating disorders that can lead to irreversible visual loss. Our understanding of IRD pathogenesis at both the genetic and cellular levels has increased tremendously over the past two decades, but the exact pathogenic mechanisms remain incompletely understood. Enhanced understanding of the pathophysiology of these diseases can result in new treatment targets. Alterations in the human gut microbiome play a key role in the pathogenesis of many ocular and nonocular diseases, such as age-related macular degeneration, neurologic and metabolic disorders, and autoimmune conditions. The gut microbiome regulates the susceptibility of mice to develop experimental autoimmune uveitis, a model for autoimmune disease of the posterior portion of the eye elicited by the systemic response to retinal antigens. Because of the mounting evidence in favor of a role for local and systemic inflammatory and autoimmune-mediated components to IRD pathogenesis, this review presents the current knowledge of gut microbiome in IRDs and discusses the association between possible changes in gut microbiome and pathogenesis of these diseases, with special attention to their possible contribution to the inflammatory underpinnings of IRDs.

Clinical and Molecular Aspects of C2orf71/PCARE in Retinal Diseases

Mutations in the photoreceptor-specific C2orf71 gene (also known as photoreceptor cilium actin regulator protein PCARE) cause autosomal recessive retinitis pigmentosa type 54 and cone-rod dystrophy. No treatments are available for patients with C2orf71 retinal ciliopathies exhibiting a severe clinical phenotype. Our understanding of the disease process and the role of PCARE in the healthy retina significantly limits our capacity to transfer recent technical developments into viable therapy choices. This study summarizes the current understanding of C2orf71-related retinal diseases, including their clinical manifestations and an unclear genotype-phenotype correlation. It discusses molecular and functional studies on the photoreceptor-specific ciliary PCARE, focusing on the photoreceptor cell and its ciliary axoneme. It is proposed that PCARE is an actin-associated protein that interacts with WASF3 to regulate the actin-driven expansion of the ciliary membrane during the development of a new outer segment disk in photoreceptor cells. This review also introduces various cellular and animal models used to model these diseases and provides an overview of potential treatments.

Disease progression of retinitis pigmentosa caused by PRPF31 variants in a Nordic population: a retrospective study with up to 36 years follow-up

BACKGROUND/AIMS

To investigate the natural history of PRPF31-related retinitis pigmentosa (RP11).

MATERIALS AND METHODS

We identified individuals with RP11 and collected retrospective data from disease onset to present date including genetics, demographic data, Goldmann visual field areas, and visual acuity measurements. Visual fields were evaluated as summed squared degrees and best-corrected visual acuity was converted to logMAR. We performed linear mixed model regression analysis to evaluate annual disease progression, and survival analysis to evaluate the age of legal blindness.

RESULTS

We included 46 subjects with RP11. Median age of disease onset was 10 years (range 5-65). Follow-up spanned from 0 to 36 years with a median of 8 years. Median Goldmann visual field areas decreased by 10.0% per year (95% CI 7.5%-12.4%) with target IV4e, 7.9% (95% CI 4.5% - 11.2%) with target III4e, and 9.3% (95% CI: 7.0% -11.5%) when combining target sizes. Individuals with RP11 maintained good visual acuity until late stage of disease. Legal blindness was reached at a median age of 57 years (95% CI 50-75 years).

CONCLUSIONS

PRPF31 variants cause autosomal dominant retinitis pigmentosa that most commonly manifests in childhood with a variable disease progression. Visual field area deteriorates faster than visual acuity and was the major cause of legal blindness in our study population. This study characterizes disease progression in retinitis pigmentosa caused by PRPF31-variants and demonstrates the importance of differentiation between specific genotypes when counselling patients and conducting natural history studies of RP.

Design and Outcomes of a Novel Multidisciplinary Ophthalmic Genetics Clinic

The Multidisciplinary Ophthalmic Genetics Clinic (MOGC) at the University of Michigan Kellogg Eye Center aims to provide medical and ophthalmic genetics care to patients with inherited ocular conditions. We have developed a clinical and referral workflow where each patient undergoes coordinated evaluation by our multidisciplinary team followed by discussions on diagnosis, prognosis, and genetic testing. Testing approaches are specific to each patient and can be targeted (single-gene, gene panel), broad (chromosomal microarray, whole-exome sequencing), or a combination. We hypothesize that this clinic model improves patient outcomes and quality of care. A retrospective chart review of patients in the MOGC from July 2020 to October 2022 revealed that the most common referral diagnoses were congenital cataracts, optic neuropathy, and microphthalmia, with 52% syndromic cases. Within this patient cohort, we saw a 76% uptake for genetic testing, among which 33% received a diagnostic test result. Our results support a tailored approach to genetic testing for specific conditions. Through case examples, we highlight the power and impact of our clinic. By integrating ophthalmic care with medical genetics and counseling, the MOGC has not only helped solve individual patient diagnostic challenges but has aided the greater population in novel genetic discoveries and research towards targeted therapeutics.

Ribbon Synapses and Retinal Disease: Review

Synaptic ribbons are presynaptic protein complexes that are believed to be important for the transmission of sensory information in the visual system. Ribbons are selectively associated with those synapses where graded changes in membrane potential drive continuous neurotransmitter release. Defective synaptic transmission can arise as a result of the mutagenesis of a single ribbon component. Visual diseases that stem from malfunctions in the presynaptic molecular machinery of ribbon synapses in the retina are rare. In this review, we provide an overview of synaptopathies that give rise to retinal malfunction and our present understanding of the mechanisms that underlie their pathogenesis and discuss muscular dystrophies that exhibit ribbon synapse involvement in the pathology.

Literature Review on Health Emigration in Rare Diseases-A Machine Learning Perspective

The article deals with one of the effects of health inequalities and gaps in access to treatments for rare diseases, namely health-driven emigration. The purpose of the paper is to systematize knowledge about the phenomenon of health emigration observed among families affected by rare diseases, for which reimbursed treatment is available, but only in selected countries. The topic proved to be niche; the issue of "health emigration in rare diseases" is an area for exploration. Therefore, the further analysis used text mining and machine learning methods based on a database selected based on keywords related to this issue. The results made it possible to systematize the guesses made by researchers in management and economic fields, to identify the most common keywords and thematic clusters around the perspective of the patient, drug manufacturer and treatment reimbursement decision-maker, and the perspective integrating all the others. Since the topic of health emigration was not directly addressed in the selected sources, the authors attempted to define the related concepts and discussed the importance of this phenomenon in managing the support system in rare diseases. Thus, they indicated directions for further research in this area.

Challenges and Opportunities in the Genetic Analysis of Inherited Retinal Dystrophies in Africa, a Literature Review

Inherited retinal dystrophies (IRDs) are a global problem that is largely unaddressed, especially in Africa. Black indigenous Africans are rarely represented in research that develops genetic tests and genetic therapies for IRDs, yet their genomes are more diverse. The aim of this literature review is to synthesize information on the IRD genetic research conducted among indigenous black Africans to identify challenges and opportunities for progress. PubMed was searched to identify empirical publications reporting the genetic analysis of IRDs among indigenous Africans. A total of 11 articles were selected for the review. Based on the information in the articles, the main genetic testing methods in use include next-generation, whole exome, and Sanger sequencing. The main IRDs characterized by the genetic tests include retinitis pigmentosa, Leber Congenital Amaurosis, Stagardt disease, and cone dystrophy. Examples of implicated genes include MERTK, GUCY2D, ABCA4, and KCNV2 for the four IRDs, respectively. Research activities on the genetics of IRDs are generally scanty in Africa. Even in South Africa and North Africa where some research activities were noted, only a few indigenous black Africans were included in the study cohorts. There is an urgent need for genetic research on IRDs, especially in East, Central, and West Africa.

The extracellular microenvironment in immune dysregulation and inflammation in retinal disorders

Inherited retinal dystrophies (IRDs) as well as genetically complex retinal phenotypes represent a heterogenous group of ocular diseases, both on account of their phenotypic and genotypic characteristics. Therefore, overlaps in clinical features often complicate or even impede their correct clinical diagnosis. Deciphering the molecular basis of retinal diseases has not only aided in their disease classification but also helped in our understanding of how different molecular pathologies may share common pathomechanisms. In particular, these relate to dysregulation of two key processes that contribute to cellular integrity, namely extracellular matrix (ECM) homeostasis and inflammation. Pathological changes in the ECM of Bruch's membrane have been described in both monogenic IRDs, such as Sorsby fundus dystrophy (SFD) and Doyne honeycomb retinal dystrophy (DHRD), as well as in the genetically complex age-related macular degeneration (AMD) or diabetic retinopathy (DR). Additionally, complement system dysfunction and distorted immune regulation may also represent a common connection between some IRDs and complex retinal degenerations. Through highlighting such overlaps in molecular pathology, this review aims to illuminate how inflammatory processes and ECM homeostasis are linked in the healthy retina and how their interplay may be disturbed in aging as well as in disease.

Alström syndrome caused by maternal uniparental disomy

Purpose

To describe a case of Alström syndrome arising from maternal uniparental disomy.

Observations

A 13-month-old boy with poor vision and nystagmus was diagnosed with Alström syndrome based on genetic testing that identified a homozygous pathogenic variant, ALMS1 c.2141_2141del (p.Ser714Tyrfs*6), that was only found in his mother and not his father. In contrast to the usual autosomal recessive inheritance pattern in which a child inherits a variant from each parent, multi-step genetic testing of the child and both parents confirmed uniparental disomy as the mechanism of inheritance.

Conclusions and Importance

Confirmation of uniparental disomy in autosomal recessive disorders allows for parental assurance that future offspring will be unaffected.

Signal Peptide Variants in Inherited Retinal Diseases: A Multi-Institutional Case Series

Signal peptide (SP) mutations are an infrequent cause of inherited retinal diseases (IRDs). We report the genes currently associated with an IRD that possess an SP sequence and assess the prevalence of these variants in a multi-institutional retrospective review of clinical genetic testing records. The online databases, RetNet and UniProt, were used to determine which IRD genes possess a SP. A multicenter retrospective review was performed to retrieve cases of patients with a confirmed diagnosis of an IRD and a concurrent SP variant. In silico evaluations were performed with MutPred, MutationTaster, and the signal peptide prediction tool, SignalP 6.0. SignalP 6.0 was further used to determine the locations of the three SP regions in each gene: the N-terminal region, hydrophobic core, and C-terminal region. Fifty-six (56) genes currently associated with an IRD possess a SP sequence. Based on the records review, a total of 505 variants were present in the 56 SP-possessing genes. Six (1.18%) of these variants were within the SP sequence and likely associated with the patients' disease based on in silico predictions and clinical correlation. These six SP variants were in the CRB1 (early-onset retinal dystrophy), NDP (familial exudative vitreoretinopathy) (FEVR), FZD4 (FEVR), EYS (retinitis pigmentosa), and RS1 (X-linked juvenile retinoschisis) genes. It is important to be aware of SP mutations as an exceedingly rare cause of IRDs. Future studies will help refine our understanding of their role in each disease process and assess therapeutic approaches.

Late-Onset Retinal Degeneration: Clinical Perspectives

Late-onset retinal degeneration (L-ORD) is a type of retinal dystrophy marked by nyctalopia and subretinal pigment epithelium deposits, which eventually promote retinal atrophy with final visual compromise. L-ORD may also present with changes in the anterior segment, notably long anterior zonules and iris atrophy, distinguishing it from other inherited eye conditions. Although it can clinically simulate age-related macular degeneration, L-ORD has a different course of progression and prognosis, requiring adequate diagnosis for patient counseling. This review summarizes the main clinical, genetic, pathophysiological, diagnostic, and therapeutic aspects of L-ORD to help ophthalmologists identify and manage this rare ocular disease.

Advancements in ocular gene therapy delivery: vectors and subretinal, intravitreal, and suprachoroidal techniques

INTRODUCTION

: Ocular gene therapy represents fertile ground for rapid innovation, with ever-expanding therapeutic strategies, molecular targets, and indications.

AREAS COVERED

: Potential indications for ocular gene therapy have classically focused on inherited retinal disease (IRD), but more recently include acquired retinal diseases, such as neovascular age-related macular degeneration, geographic atrophy and diabetic retinopathy. Ocular gene therapy strategies have proliferated recently, and include gene augmentation, gene inactivation, gene editing, RNA modulation, and gene-independent gene augmentation. Viral vector therapeutic constructs include adeno-associated virus and lentivirus and continue to evolve through directed evolution and rationale design. Ocular gene therapy administration techniques have expanded beyond pars plana vitrectomy with subretinal injection to intravitreal injection and suprachoroidal injection.

EXPERT OPINION

: The success of treatment for IRD, paired with the promise of clinical research in acquired retinal diseases and in administration techniques, has raised the possibility of in-office gene therapy for common retinal disorders within the next five to ten years.