Alström syndrome-wide clinical variability within the same variant: a case report and literature review.

Background: Alström disease is a rare disorder caused by various variants in the ALMS1 gene. It is characterised by multiorgan involvement, namely neurosensory deficits, endocrine and metabolic disturbances, cardiomyopathy, and hepatic and renal dysfunction. The disease exhibits marked interindividual variability, both in clinical manifestations and age of onset. Several attempts have been made to establish a relationship between phenotype and genotype, with little success. Methods: We present the case of an infant who presented with dilated cardiomyopathy, above-average weight and neurosensory deficits, raising the suspicion for Alström syndrome, later confirmed through genetic testing. Moreover, we conducted an extensive literature search to identify all reported cases having the same variant as our patient, in order to evaluate whether specific mutated alleles have a role in determining phenotype-genotype associations. Results: A 4-month-old female infant with a recent history of bronchiolitis was referred to our centre due to a systolic murmur. In our service, the clinical exam was significant for above-average weight, dyspnea, wheezing and a grade II systolic murmur. Echocardiography revealed dilated cardiomyopathy with severe systolic dysfunction of the left ventricle. Laboratory investigations revealed elevated NT-proBNP and troponin levels, along with positive IgM antibodies for CMV and EBV. Dilated cardiomyopathy attributed to viral myocarditis was suspected. Treatment with ACE inhibitors and diuretics was started, with a favourable response initially. However, after a few months, the patient presented with vertical nystagmus and head bobbing. The ophthalmologic exam revealed cone-rode dystrophy. Considering the constellation of symptoms, Alström syndrome was suspected. Genetic testing revealed a homozygous variant [c.4156dup (p.Thr1386Asnfs*15)] in the ALMS1 gene, confirming the diagnosis. Conclusion: Our literature review revealed 8 additional cases harbouring the same variant as our patient, five in a heterozygous state, two in a homozygous state and one with only one allele identified. The identified patients presented high heterogeneity of clinical manifestations and age of onset. The heterogeneity persisted even in patients with homozygous variants, suggesting the involvement of factors beyond the specific disease-causing variant in determining disease manifestation. Therefore, genotype-phenotype correlations might not be supported by specific variants.

Acute Angle Closure Glaucoma in a Patient With Jalili-Smith Syndrome.

We describe a 29-year-old Iranian male with Jalili-Smith syndrome (JSS), who presented with acute angle closure glaucoma. JSS is a rare autosomal recessive oculo-dental disorder characterized by cone-rod dystrophy and amelogenesis imperfecta. Though the disease is observed worldwide, many cases are concentrated in the Gaza Strip. Consanguinity is an important risk factor. Patients typically present with photophobia, nystagmus, and enamel deformation. Our patient exhibited nystagmus, photophobia, cataracts, hyperopia, narrow-angle glaucoma, marked thinning of the retina, and bull's eye maculopathy. In addition, we describe the findings of optical coherence tomography angiography (OCTA). Our patient also underwent phacoemulsification in both eyes with concomitant minimally invasive glaucoma surgeries (MIGS). To the best of our knowledge, narrow-angle glaucoma, OCTA findings, and cataract surgery combined with MIGS have not been reported before in patients with JSS.

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.

Effects of elevated intraocular pressure on alpha ganglion cells in experimental glaucoma mice.

Glaucoma is a leading cause of blindness worldwide and glaucoma patients exhibit an early diffuse loss of retinal sensitivity followed by focal loss of RGCs. Combining some previous published results and some new data, this paper provides our current view on how high IOP (H-IOP) affects the light response sensitivity of a subset of RGCs, the alpha-ganglion cells (αGCs), as well as their presynaptic bipolar cells (DBCs and HBCs) and A2 amacrine cells (AIIACs) in dark-adapted mouse retinas. Our data demonstrate that H-IOP in experimental glaucoma mice significantly decreases light-evoked spike response sensitivity of sONαGCs and sOFFαGCs (i.e., raises thresholds by 1.5-2.5 log units), but not that of the tONαGCs and tOFFαGCs. The sensitivity loss in sONαGCs and sOFFαGCs is mediated by a H-IOP induced suppression of AIIAC response which is caused by a decrease of transmission efficacy of the DBCR→AIIAC synapse. We also provide evidence supporting the hypothesis that BK channels in the A17AC→DBCR feedback synapse are the H-IOP sensor that regulates the DBCR→AIIAC synaptic efficacy, as BK channel blocker IBTX mimics the action of H-IOP. Our results provide useful information for designing strategies for early detection and possible treatments of glaucoma as physiological changes occur before irreversible structural damage.

A novel homozygous nonsense variant in CABP4 causing stationary cone/rod synaptic dysfunction.

INTRODUCTION: Variants in the CABP4 gene cause a phenotype to be included in the spectrum of congenital stationary night blindness, though some reports suggest that the clinical abnormalities are more accurately categorized as a synaptic disease of the cones and rods. We report a novel homozygous nonsense variant in CABP4 in a patient complaining of non-progressive reduced visual acuity and photophobia but not nyctalopia. METHODS: Complete ocular examination, fundus photographs, autofluorescence, optical coherence tomography, electroretinography, and targeted sequencing of known inherited retinal disease-associated genes. RESULTS: A 25-year-old man monitored for 13 years complains of a lifelong history of stable reduced visual acuity (20/150), impaired color vision (1 of 14 plates), small-amplitude nystagmus, and photophobia without nyctalopia. He is also hyperopic (+7D), and his electroretinography shows significantly reduced rod and cone responses. Targeted genetic analysis revealed a novel homozygous variant in the CABP4 gene at c.181C>T, p. (Gln61*) underlying his clinical presentation. CONCLUSIONS: A novel variant in CABP4 is associated with stationary cone and rod dysfunction resulting in decreased acuity, color deficit, and photophobia, but not nyctalopia.

Clinical, Genetic, and Histopathological Characteristics of CRX-associated Retinal Dystrophies.

PURPOSE: To describe phenotypic, genotypic, and histopathological features of inherited retinal dystrophies associated with the CRX gene (CRX-RDs). DESIGN: Retrospective multicenter cohort study including histopathology. SUBJECTS: Thirty-nine patients from 31 families with pathogenic variants in the CRX gene. METHODS: Clinical data of 152 visits were collected from medical records. The median follow-up time was 9.1 years (interquartile range (IQR), 3.3-15.3 years; range, 0.0-48.8 years). Histopathologic examination of the eye of a 17-year-old patient with advanced early-onset CRX-RD was performed. MAIN OUTCOME MEASURES: Visual acuity, retinal imaging, electroretinography, genotype-phenotype correlation, and histopathological examination were evaluated. RESULTS: The age at onset ranged from birth to the eighth decade of life. Median visual acuity was 1.00 logarithm of the minimum angle of resolution (logMAR) (IQR, 0.69-1.48 logMAR; range, 0.06-3.00 logMAR) at a mean age of 52.0 ± 19.9 years (range, 4.6-81.9 years). Sufficient imaging was available for 36 out of 39 patients (92.3%), and all showed degeneration of at least the macula. Of these 36 patients, 22 (61.1%) had only macular dystrophy. Another 10 patients (27.8%) had additional degeneration beyond the vascular arcades, and 4 patients (11.1%) panretinal degeneration. Two patients (5.1%) had Leber congenital amaurosis. In total, 21 different disease-associated heterozygous CRX variants were identified (10 frameshift, 7 missense, 2 deletion, 1 nonsense, 1 deletion-insertion variants). Missense variants in the CRX homeodomain and 2 variants deleting all functional domains, thus causing haploinsufficiency, generally tended to cause milder late-onset phenotypes. Histopathologic examination of the eye of a 17-year-old patient with advanced early-onset retinal dystrophy due to a heterozygous deletion of exons 3 and 4 of the CRX gene revealed loss of laminar integrity and widespread photoreceptor degeneration especially in the central retina, with extensive loss of photoreceptor nuclei and outer segments. CONCLUSIONS: This study illustrates the large clinical and genetic heterogenic spectrum of CRX-RDs, ranging from Leber congenital amaurosis to mild late-onset maculopathy resembling occult macular dystrophy. Haploinsufficiency and missense variants tended to be associated with milder phenotypes. Patients showed degeneration predominantly affecting the central retina on imaging. The histopathological findings also mirror these clinical findings and features similar to previously reported animal models of CRX-RDs. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

A GUCY2D variant associated cone-rod dystrophy with electronegative ERG: A case report and review.

Purpose: Cone-rod dystrophies (CORD) are inherited retinal dystrophies characterized by primary cone degeneration with secondary rod involvement. We report two patients from the same family with a dominant variant in the guanylate cyclase 2D (GUCY2D) gene with different phenotypes in the electroretinogram (ERG). Observations: A 21-year-old lady (Patient 1) was referred due to experiencing blurry vision and color vision impairment. Visual field testing revealed a central scotoma. Spectral-domain optical coherence tomography (SD-OCT) and fundus autofluorescence (FAF) documented macula dysfunction. Reduced amplitude was observed in the photopic responses of ERG. Her 54-year-old father (Patient 2) had similar issues with blurry vision. A dilated fundus examination displayed bilateral macular atrophy. Loss of the ellipsoid zone line and collapse of the outer nuclear segment were noted on the SD-OCT. Photopic ERG responses were extinguished, and an electronegative ERG was observed in the dark-adapted 3.0 ERG. The gene report revealed a c.2512C > T (p.Arg838Cys) variant in GUCY2D for both patients. They were respectively diagnosed as cone dystrophy (COD) and cone-rod dystrophy (CORD). Conclusions: We report two different clinical phenotypes in GUCY2D-associated COD despite sharing the same variant. A dysfunction in the synaptic junction between the photoreceptor and the secondary neuron was proposed to explain the electronegative ERG. This explanation might extend to other gene-related cases of CORD with electronegative ERG.

Clinical exome analysis and targeted gene repair of the c.1354dupT variant in iPSC lines from patients with PROM1-related retinopathies exhibiting diverse phenotypes.

BACKGROUND: Inherited retinal dystrophies (IRD) are one of the main causes of incurable blindness worldwide. IRD are caused by mutations in genes that encode essential proteins for the retina, leading to photoreceptor degeneration and loss of visual function. IRD generates an enormous global financial burden due to the lack of understanding of a significant part of its pathophysiology, molecular diagnosis, and the near absence of non-palliative treatment options. Patient-derived induced pluripotent stem cells (iPSC) for IRD seem to be an excellent option for addressing these questions, serving as exceptional tools for in-depth studies of IRD pathophysiology and testing new therapeutic approaches. METHODS: From a cohort of 8 patients with PROM1-related IRD, we identified 3 patients carrying the same variant (c.1354dupT) but expressing three different IRD phenotypes: Cone and rod dystrophy (CORD), Retinitis pigmentosa (RP), and Stargardt disease type 4 (STGD4). These three target patients, along with one healthy relative from each, underwent comprehensive ophthalmic examinations and their genetic panel study was expanded through clinical exome sequencing (CES). Subsequently, non-integrative patient-derived iPSC were generated and fully characterized. Correction of the c.1354dupT mutation was performed using CRISPR/Cas9, and the genetic restoration of the PROM1 gene was confirmed through flow cytometry and western blotting in the patient-derived iPSC lines. RESULTS: CES revealed that 2 target patients with the c.1354dupT mutation presented monoallelic variants in genes associated with the complement system or photoreceptor differentiation and peroxisome biogenesis disorders, respectively. The pluripotency and functionality of the patient-derived iPSC lines were confirmed, and the correction of the target mutation fully restored the capability of encoding Prominin-1 (CD133) in the genetically repaired patient-derived iPSC lines. CONCLUSIONS: The c.1354dupT mutation in the PROM1 gene is associated to three distinct AR phenotypes of IRD. This pleotropic effect might be related to the influence of monoallelic variants in other genes associated with retinal dystrophies. However, further evidence needs to be provided. Future experiments should include gene-edited patient-derived iPSC due to its potential as disease modelling tools to elucidate this matter in question.

Detailed phenotype and long-term follow-up of RAB28-associated cone-rod dystrophy.

PURPOSE: To gain an insight into the pathophysiology of RAB28-associated inherited retinal degeneration through detailed phenotyping and long-term longitudinal follow-up. METHODS: The patient underwent complete ophthalmic examinations. Visual function was assessed with microperimetry, full-field electroretinography (ffERG), imaging with optical coherence tomography (OCT), short-wave (SW), and near-infrared (NIR) fundus autofluorescence (FAF). RESULTS: A healthy Haitian woman with homozygous pathogenic variants (c.68C > T; p.Ser23Phe) in RAB28 presented at 16 years of age with a four-year history of blurred vision. Visual acuities were 20/125 in each eye, which remained relatively stable since. At age 27, cone ffERGs were non-detectable and borderline for rod-mediated responses. Kinetic fields were full to a V-4e target, undetectable to a small I-4e stimulus. Microperimetry showed an absolute central scotoma surrounded by a pericentral relative scotoma. SD-OCT showed an undetectable or barely detectable foveal and parafoveal photoreceptor outer nuclear layer (ONL), photoreceptor outer segment (POS), and retinal pigment epithelium (RPE) signals and loss of the SW- and NIR-FAF signals. This atrophic region was separated from a normally laminated retina by a narrow transition zone (TZ) of hyper SW- and NIR-FAF that co-localized with preserved ONL but abnormally thinned POS and RPE. There was minimal centrifugal (<100 µm) expansion over a six-year period. CONCLUSION: The cone-rod dystrophy phenotype documented herein supports a critical role of RAB28 for cone function and POS maintenance. Severe central photoreceptor and RPE loss with a predilection for POS loss in TZs suggests possible disruptions of complex mechanisms that maintain central cone photoreceptor and RPE homeostasis.

The Clinical and Mutational Spectrum of Bardet-Biedl Syndrome in Saudi Arabia.

The retinal features of Bardet-Biedl syndrome (BBS) are insufficiently characterized in Arab populations. This retrospective study investigated the retinal features and genotypes of BBS in Saudi patients managed at a single tertiary eye care center. Data analysis of the identified 46 individuals from 31 families included visual acuity (VA), systemic manifestations, multimodal retinal imaging, electroretinography (ERG), family pedigrees, and genotypes. Patients were classified to have cone-rod, rod-cone, or generalized photoreceptor dystrophy based on the pattern of macular involvement on the retinal imaging. Results showed that nyctalopia and subnormal VA were the most common symptoms with 76% having VA ≤ 20/200 at the last visit (age: 5-35). Systemic features included obesity 91%, polydactyly 56.5%, and severe cognitive impairment 33%. The predominant retinal phenotype was cone-rod dystrophy 75%, 10% had rod-cone dystrophy and 15% had generalized photoreceptor dystrophy. ERGs were undetectable in 95% of patients. Among the 31 probands, 61% had biallelic variants in BBSome complex genes, 32% in chaperonin complex genes, and 6% had biallelic variants in ARL6; including six previously unreported variants. Interfamilial and intrafamilial variabilities were noted, without a clear genotype-phenotype correlation. Most BBS patients had advanced retinopathy and were legally blind by early adulthood, indicating a narrow therapeutic window for rescue strategies.

Alström Syndrome: A Review Focusing on Its Diverse Clinical Manifestations and Their Etiology as a Ciliopathy.

Alström syndrome is a form of inherited obesity caused by a single gene abnormality and is inherited as an autosomal recessive trait. It is characterised by a variety of clinical manifestations, including progressive visual and hearing impairment, type 2 diabetes mellitus, dilated cardiomyopathy, and hepatic and renal dysfunction, in addition to obesity. Recent insights underline the pivotal involvement of the disease-associated gene (ALMS1) in cilia formation and function, leading to the classification of its clinical manifestations as a ciliopathy. This review delineates the diverse clinical indicators defining the syndrome and elucidates its pathological underpinnings.

Exploring the diverse clinical and variant spectrum of CEP78-associated syndrome: Novel pathogenic variants identified in a case series.

Dual sensory impairment, commonly referred to as combined hearing and vision loss, can stem from a diverse spectrum of conditions, each presenting with its unique set of clinical characteristics. Our understanding of dual sensory impairment has expanded significantly in the past decade, broadening the scope of genetic differential diagnoses, including genes such as CEP250, ARSG, TUBB4B, CEP78, and ABHD12. A case series including three patients from two families with genetically diagnosed CEP78-associated cone-rod dystrophy was identified. We collected and reviewed their clinical records, imaging data, and genetic testing results. In addition, a comprehensive literature review was conducted on the phenotype and the genetic testing modality employed in all published CEP78 cases through a PubMed search using the keyword "CEP78." A retinal dystrophy panel detected a novel homozygous CEP78 pathogenic variant (c.1447C>T, p.Arg483*) in siblings-Cases 1 and 2-from Family 1. Both teenagers have a clinical diagnosis of cone-rod dystrophy with presumed normal hearing. Case 3 from Family 2, diagnosed with cone-rod dystrophy and early-onset hearing loss, was found to carry a CEP78 pathogenic variant (c.1206-2A>C) and a likely pathogenic variant (c.856_857del, p.Leu286Glyfs*12) also through panel-based genetic testing. Intriguingly, neither of these variants was reported in an affected sibling's clinical whole-exome sequencing (WES) report when performed in 2015. A review of CEP78-related literature unveiled that the initial report linking CEP78 to cone-rod dystrophy and hearing loss was published in September 2016. Any pathogenic variant found in CEP78 before 2016 would have been categorized as a "clearly disruptive variant in a gene of uncertain significance (GUS)" and might not have been reported in the WES report. It is important to acknowledge that our understanding of genotype-phenotype associations is undergoing rapid expansion. It is also crucial to recognize that repeat genetic testing may represent a fundamentally different approach, given the technological advancements not only in the coverage of the sequencing but also in the more comprehensive understanding of genotype-phenotype associations. This case series also enriches the existing CEP78 literature by providing phenotypic details of the youngest case of CEP78-associated retinopathy reported in the literature (Case 2), which expands our perspective on the natural history of disease in this disorder.

In Silico CRISPR-Cas-Mediated Base Editing Strategies for Early-Onset, Severe Cone-Rod Retinal Degeneration in Three Crumbs homolog 1 Patients, including the Novel Variant c.2833G>A.

Pathogenic variants in the Crumbs homolog 1 (CRB1) gene lead to severe, childhood-onset retinal degeneration leading to blindness in early adulthood. There are no approved therapies, and traditional adeno-associated viral vector-based gene therapy approaches are challenged by the existence of multiple CRB1 isoforms. Here, we describe three CRB1 variants, including a novel, previously unreported variant that led to retinal degeneration. We offer a CRISPR-Cas-mediated DNA base editing strategy as a potential future therapeutic approach. This study is a retrospective case series. Clinical and genetic assessments were performed, including deep phenotyping by retinal imaging. In silico analyses were used to predict the pathogenicity of the novel variant and to determine whether the variants are amenable to DNA base editing strategies. Case 1 was a 24-year-old male with cone-rod dystrophy and retinal thickening typical of CRB1 retinopathy. He had a relatively preserved central outer retinal structure and a best corrected visual acuity (BCVA) of 60 ETDRS letters in both eyes. Genetic testing revealed compound heterozygous variants in exon 9: c.2843G>A, p.(Cys948Tyr) and a novel variant, c.2833G>A, p.(Gly945Arg), which was predicted to likely be pathogenic by an in silico analysis. Cases 2 and 3 were two brothers, aged 20 and 24, who presented with severe cone-rod dystrophy and a significant disruption of the outer nuclear layers. The BCVA was reduced to hand movements in both eyes in Case 2 and to 42 ETDRS letters in both eyes in Case 3. Case 2 was also affected with marked cystoid macular lesions, which are common in CRB1 retinopathy, but responded well to treatment with oral acetazolamide. Genetic testing revealed two c.2234C>T, p.(Thr745Met) variants in both brothers. As G-to-A and C-to-T variants, all three variants are amenable to adenine base editors (ABEs) targeting the forward strand in the Case 1 variants and the reverse strand in Cases 2 and 3. Available PAM sites were detected for KKH-nSaCas9-ABE8e for the c.2843G>A variant, nSaCas9-ABE8e and KKH-nSaCas9-ABE8e for the c.2833G>A variant, and nSpCas9-ABE8e for the c.2234C>T variant. In this case series, we report three pathogenic CRB1 variants, including a novel c.2833G>A variant associated with early-onset cone-rod dystrophy. We highlight the severity and rapid progression of the disease and offer ABEs as a potential future therapeutic approach for this devastating blinding condition.

PRPH2-Related Retinal Dystrophies: Mutational Spectrum in 103 Families from a Spanish Cohort.

PRPH2, one of the most frequently inherited retinal dystrophy (IRD)-causing genes, implies a high phenotypic variability. This study aims to analyze the PRPH2 mutational spectrum in one of the largest cohorts worldwide, and to describe novel pathogenic variants and genotype-phenotype correlations. A study of 220 patients from 103 families recruited from a database of 5000 families. A molecular diagnosis was performed using classical molecular approaches and next-generation sequencing. Common haplotypes were ascertained by analyzing single-nucleotide polymorphisms. We identified 56 variants, including 11 novel variants. Most of them were missense variants (64%) and were located in the D2-loop protein domain (77%). The most frequently occurring variants were p.Gly167Ser, p.Gly208Asp and p.Pro221_Cys222del. Haplotype analysis revealed a shared region in families carrying p.Leu41Pro or p.Pro221_Cys222del. Patients with retinitis pigmentosa presented an earlier disease onset. We describe the largest cohort of IRD families associated with PRPH2 from a single center. Most variants were located in the D2-loop domain, highlighting its importance in interacting with other proteins. Our work suggests a likely founder effect for the variants p.Leu41Pro and p.Pro221_Cys222del in our Spanish cohort. Phenotypes with a primary rod alteration presented more severe affectation. Finally, the high phenotypic variability in PRPH2 hinders the possibility of drawing genotype-phenotype correlations.

Rescue of cone and rod photoreceptor function in a CDHR1-model of age-related retinal degeneration.

Age-related macular degeneration (AMD) is the most common cause of untreatable blindness in the developed world. Recently, CDHR1 has been identified as the cause of a subset of AMD that has the appearance of the "dry" form, or geographic atrophy. Biallelic variants in CDHR1-a specialized protocadherin highly expressed in cone and rod photoreceptors-result in blindness from shortened photoreceptor outer segments and progressive photoreceptor cell death. Here we demonstrate long-term morphological, ultrastructural, functional, and behavioral rescue following CDHR1 gene therapy in a relevant murine model, sustained to 23-months after injection. This represents the first demonstration of rescue of a monogenic cadherinopathy in vivo. Moreover, the durability of CDHR1 gene therapy seems to be near complete-with morphological findings of the rescued retina not obviously different from wildtype throughout the lifespan of the mouse model. A follow-on clinical trial in patients with CDHR1-associated retinal degeneration is warranted. Hypomorphic CDHR1 variants may mimic advanced dry AMD. Accurate clinical classification is now critical, as their pathogenesis and treatment are distinct.

Structural and functional characterization of an individual with the M285R KCNV2 hypomorphic allele.

BACKGROUND: Disease-causing variants in the KCNV2 gene are associated with "cone dystrophy with supernormal rod responses," a rare autosomal recessive retinal dystrophy. There is no previous report of hypomorphic variants in the disease. MATERIAL AND METHODS: Medical history, genetic testing, ocular examination, high-resolution retinal imaging including adaptive optics scanning light ophthalmoscopy (AOSLO), and functional assessments. RESULTS: A 16-year-old male with mild cone-rod dystrophy presented with reduced central vision and photophobia. Genetic testing showed two variants in KCNV2, c.614_617dupAGCG (p.207AlafsTer166) and c.854T>G (p.Met285Arg), the latter which was previously considered benign. Electrophysiological assessment revealed the pathognomic electroretinogram waveforms associated with KCNV2-retinopathy. Optical coherence tomography showed discrete focal ellipsoid zone disruption, while fundus autofluorescence was normal. Non-waveguiding cones corresponding to areas of loss of photoreceptor integrity were visible on adaptive optics scanning light ophthalmoscopy. Retinal sensitivity and fixation were relatively preserved, with a demonstrable deterioration after 14 months of follow-up. CONCLUSIONS: We provide functional and structural evidence that the variant M285R is disease-causing if associated with a loss-of-function variant. To the best of our knowledge, this is the first hypomorphic allele reported in KCNV2.

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.

A Retrospective Longitudinal Study of 460 Patients with ABCA4-Associated Retinal Disease.

PURPOSE: To investigate the distribution of genotypes and natural history of ABCA4-associated retinal disease in a large cohort of patients seen at a single institution. DESIGN: Retrospective, single-institution cohort review. PARTICIPANTS: Patients seen at the University of Iowa between November 1986 and August 2022 clinically suspected to have disease caused by sequence variations in ABCA4. METHODS: DNA samples from participants were subjected to a tiered testing strategy progressing from allele-specific screening to whole genome sequencing. Charts were reviewed, and clinical data were tabulated. The pathogenic severity of the most common alleles was estimated by studying groups of patients who shared 1 allele. Groups of patients with shared genotypes were reviewed for evidence of modifying factor effects. MAIN OUTCOME MEASURES: Age at first uncorrectable vision loss, best-corrected visual acuity, and the area of the I2e isopter of the Goldmann visual field. RESULTS: A total of 460 patients from 390 families demonstrated convincing clinical features of ABCA4-associated retinal disease. Complete genotypes were identified in 399 patients, and partial genotypes were identified in 61. The median age at first vision loss was 16 years (range, 4-76 years). Two hundred sixty-five families (68%) harbored a unique genotype, and no more than 10 patients shared any single genotype. Review of the patients with shared genotypes revealed evidence of modifying factors that in several cases resulted in a > 15-year difference in age at first vision loss. Two hundred forty-one different alleles were identified among the members of this cohort, and 161 of these (67%) were found in only a single individual. CONCLUSIONS: ABCA4-associated retinal disease ranges from a very severe photoreceptor disease with an onset before 5 years of age to a late-onset retinal pigment epithelium-based condition resembling pattern dystrophy. Modifying factors frequently impact the ABCA4 disease phenotype to a degree that is similar in magnitude to the detectable ABCA4 alleles themselves. It is likely that most patients in any cohort will harbor a unique genotype. The latter observations taken together suggest that patients' clinical findings in most cases will be more useful for predicting their clinical course than their genotype. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Phenotyping and genotyping inherited retinal diseases: Molecular genetics, clinical and imaging features, and therapeutics of macular dystrophies, cone and cone-rod dystrophies, rod-cone dystrophies, Leber congenital amaurosis, and cone dysfunction syndromes.

Inherited retinal diseases (IRD) are a leading cause of blindness in the working age population and in children. The scope of this review is to familiarise clinicians and scientists with the current landscape of molecular genetics, clinical phenotype, retinal imaging and therapeutic prospects/completed trials in IRD. Herein we present in a comprehensive and concise manner: (i) macular dystrophies (Stargardt disease (ABCA4), X-linked retinoschisis (RS1), Best disease (BEST1), PRPH2-associated pattern dystrophy, Sorsby fundus dystrophy (TIMP3), and autosomal dominant drusen (EFEMP1)), (ii) cone and cone-rod dystrophies (GUCA1A, PRPH2, ABCA4, KCNV2 and RPGR), (iii) predominant rod or rod-cone dystrophies (retinitis pigmentosa, enhanced S-Cone syndrome (NR2E3), Bietti crystalline corneoretinal dystrophy (CYP4V2)), (iv) Leber congenital amaurosis/early-onset severe retinal dystrophy (GUCY2D, CEP290, CRB1, RDH12, RPE65, TULP1, AIPL1 and NMNAT1), (v) cone dysfunction syndromes (achromatopsia (CNGA3, CNGB3, PDE6C, PDE6H, GNAT2, ATF6), X-linked cone dysfunction with myopia and dichromacy (Bornholm Eye disease; OPN1LW/OPN1MW array), oligocone trichromacy, and blue-cone monochromatism (OPN1LW/OPN1MW array)). Whilst we use the aforementioned classical phenotypic groupings, a key feature of IRD is that it is characterised by tremendous heterogeneity and variable expressivity, with several of the above genes associated with a range of phenotypes.

Variants in UBAP1L lead to autosomal recessive rod-cone and cone-rod dystrophy.

PURPOSE: Progressive inherited retinal degenerations (IRDs) affecting rods and cones are clinically and genetically heterogeneous and can lead to blindness with limited therapeutic options. The major gene defects have been identified in subjects of European and Asian descent with only few reports of North African descent. METHODS: Genome, targeted next-generation, and Sanger sequencing was applied to cohort of ∼4000 IRDs cases. Expression analyses were performed including Chip-seq database analyses, on human-derived retinal organoids (ROs), retinal pigment epithelium cells, and zebrafish. Variants' pathogenicity was accessed using 3D-modeling and/or ROs. RESULTS: Here, we identified a novel gene defect with three distinct pathogenic variants in UBAP1L in 4 independent autosomal recessive IRD cases from Tunisia. UBAP1L is expressed in the retinal pigment epithelium and retina, specifically in rods and cones, in line with the phenotype. It encodes Ubiquitin-associated protein 1-like, containing a solenoid of overlapping ubiquitin-associated domain, predicted to interact with ubiquitin. In silico and in vitro studies, including 3D-modeling and ROs revealed that the solenoid of overlapping ubiquitin-associated domain is truncated and thus ubiquitin binding most likely abolished secondary to all variants identified herein. CONCLUSION: Biallelic UBAP1L variants are a novel cause of IRDs, most likely enriched in the North African population.