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.

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.

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.

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.

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.

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.

Cortical Visual Mapping following Ocular Gene Augmentation Therapy for Achromatopsia.

The ability of the adult human brain to develop function following correction of congenital deafferentation is controversial. Specifically, cases of recovery from congenital visual deficits are rare. CNGA3-achromatopsia is a congenital hereditary disease caused by cone-photoreceptor dysfunction, leading to impaired acuity, photoaversion, and complete color blindness. Essentially, these patients have rod-driven vision only, seeing the world in blurry shades of gray. We use the uniqueness of this rare disease, in which the cone-photoreceptors and afferent fibers are preserved but do not function, as a model to study cortical visual plasticity. We had the opportunity to study two CNGA3-achromatopsia adults (one female) before and after ocular gene augmentation therapy. Alongside behavioral visual tests, we used novel fMRI-based measurements to assess participants' early visual population receptive-field sizes and color regions. Behaviorally, minor improvements were observed, including reduction in photoaversion, marginal improvement in acuity, and a new ability to detect red color. No improvement was observed in color arrangement tests. Cortically, pretreatment, patients' population-receptive field sizes of early visual areas were untypically large, but were decreased following treatment specifically in the treated eye. We suggest that this demonstrates cortical ability to encode new input, even at adulthood. On the other hand, no activation of color-specific cortical regions was demonstrated in these patients either before or up to 1 year post-treatment. The source of this deficiency might be attributed either to insufficient recovery of cone function at the retinal level or to challenges that the adult cortex faces when computing new cone-derived input to achieve color perception.SIGNIFICANCE STATEMENT The possibility that the adult human brain may regain or develop function following correction of congenital deafferentation has fired the imagination of scientists over the years. In the visual domain, cases of recovery from congenital deficits are rare. Gene therapy visual restoration for congenital CNGA3-achromatopsia, a disease caused by cone photoreceptor dysfunction, gave us the opportunity to examine cortical function, to the best of our knowledge for the first time, both before and after restorative treatment. While behaviorally only minor improvements were observed post-treatment, fMRI analysis, including size algorithms of population-receptive fields, revealed cortical changes, specifically receptive field size decrease in the treated eyes. This suggests that, at least to some degree, the adult cortex is able to encode new input.

Identification of autosomal recessive novel genes and retinal phenotypes in members of the solute carrier (SLC) superfamily.

PURPOSE: This study aimed to investigate the clinical and genetic aspects of solute carrier (SLC) genes in inherited retinal diseases (IRDs). METHODS: Exome sequencing data were filtered to identify pathogenic variants in SLC genes. Analysis of transcript and protein expression was performed on fibroblast cell lines and retinal sections. RESULTS: Comprehensive analysis of 433 SLC genes in 913 exome sequencing IRD samples revealed homozygous pathogenic variants in 6 SLC genes, including 2 candidate novel genes, which were 2 variants in SLC66A1, causing autosomal recessive retinitis pigmentosa (ARRP), and a variant in SLC39A12, causing autosomal recessive mild widespread retinal degeneration with marked macular involvement. In addition, we present 4 families with ARRP and homozygous null variants in SLC37A3 that were previously suggested to cause retinitis pigmentosa, 2 of which cause exon skipping. The recently reported SLC4A7- c.2007dup variant was found in 2 patients with ARRP resulting in the absence of protein. Finally, variants in SLC24A1 were found in 4 individuals with either ARRP or congenital stationary night blindness. CONCLUSION: We report on SLC66A1 and SLC39A12 as candidate novel IRD genes, establish SLC37A3 pathogenicity, and provide further evidence of SLC4A7 as IRD genes. We extend the phenotypic spectrum of SLC24A1 and suggest that its ARRP phenotype may be more common than previously reported.

Autosomal dominant retinitis pigmentosa with incomplete penetrance due to an intronic mutation of the PRPF31 gene.

Purpose: To identify the molecular mechanisms of the development of autosomal dominant retinitis pigmentosa (adRP) with incomplete penetrance in an Israeli Muslim Arab family. Methods: Two patients with adRP underwent a detailed ophthalmic evaluation, including funduscopic examination, visual field testing, optical coherence tomography, and electroretinography. Genetic analysis was performed using a combination of whole exome sequencing (WES) and Sanger sequencing. The pathogenicity of the identified intronic variant was evaluated in silico using several web-based tools, in vitro using a minigene-based assay, and in vivo using reverse transcription PCR analysis of lymphocyte-derived RNA. The relative abundance of alternatively spliced transcripts was evaluated using amplicon-based next-generation sequencing. The relative expression levels of PRPF31 and CNOT3 were measured using quantitative PCR (qPCR) analysis. Results: The two patients recruited in this study had childhood-onset RP, with night blindness as the initial symptom, followed by concentric restriction of the visual field. The funduscopic findings included narrowed retinal blood vessels and peripheral bone spicule pigmentation. By the third decade of life, the full-field electroretinography findings had been remarkably attenuated. In these patients, we identified a novel heterozygous intronic variant at position +5 of PRPF31 intron 11 (c.1146+5G>T). The same variant was also detected in one asymptomatic family member. Through in silico analysis, the variant was predicted to alter the splicing of intron 11. An in vitro splicing assay and a reverse transcription PCR analysis of lymphocyte-derived RNA revealed that the mutant allele yielded mainly a shorter transcript in which exon 11 was skipped. The skipping of exon 11 was expected to cause a frameshift and an aberrant truncated protein (p.Tyr359Serfs*29). The qPCR analysis revealed reduced PRPF31 expression levels in the mutation carriers, without a significant difference between the affected patient and his asymptomatic brother. We evaluated several factors that have been suggested to correlate with non-penetrance of PRPF31 mutations, including the number of cis-acting MSR1 elements adjacent to the PRPF31 core promoter, CNOT3 expression level, and CNOT3 rs4806718 single-nucleotide polymorphism. None of these factors correlated with non-penetrance in the family in this study. Conclusions: We report a novel intronic mutation in PRPF31 underlying adRP. This report expands the spectrum of pathogenic mutations in PRPF31 and further demonstrates the importance of intronic mutations. Moreover, it demonstrates the phenomenon of incomplete penetrance previously associated with PRPF31 mutations. The fact that the non-penetrance in the family in this study could not be explained by any of the known mechanisms suggests the possible contribution of a novel modifier of PRPF31 penetrance.

Relatively mild blue cone monochromacy phenotype caused by various haplotypes in the L- and M-cone opsin genes.

Purpose: Blue cone monochromacy (BCM) is an X-linked retinopathy caused by mutations in the red and green cone opsin genes. The aim of this study was to establish the clinical, genetic, and electrophysiological characteristics of a specific form of BCM. Methods: Patients harboring mutations in the OPN1LW/OPN1MW genes underwent a full clinical examination, including ocular examination, color vision, full-field electroretinography, color fundus and autofluorescence photography, and optical coherence tomography. Genetic analysis was performed using whole-exome sequencing, duplex PCR, PCR/restriction fragment length polymorphism, and Sanger sequencing. IBM SPSS Statistics v. 21.0 was used for the data analysis. Results: Twenty-five patients harboring various haplotypes in exon 3 of the OPN1LW/OPN1MW genes were recruited. They showed a milder incomplete phenotype of BCM than the typical BCM control group. They presented significantly better visual acuity (logarithm of the minimum angle of resolution [logMAR] 0.48 ± 0.26 vs. 1.10 ± 0.54; p < 0.0001) and a highly myopic refraction (-7.81 ± 5.81 D vs. -4.78 ± 5.27 D; p = 0.0222) compared with the BCM control group. The study group had higher 30-Hz cone flicker responses (28.60 ± 15.02 µv; n = 24), whereas the BCM group had none (0.66 ± 2.12 µv; n = 21; p < 0.0001). The Lanthony 15-HUE desaturated test was variable for the exon 3 haplotype group, with a tendency toward the deutan-protan axis. Conclusions: The present study included genetic and clinical data from the largest cohort of patients with exon 3 haplotypes that were previously shown to cause missplicing of the OPN1LW and OPN1MW genes. Analysis of the clinical data revealed better best-corrected visual acuity, more severe myopia, and higher 30-Hz cone flicker responses in the patients with exon 3 haplotypes than in those with typical BCM.

Ultra-widefield fundus autofluorescence imaging in patients with autosomal recessive retinitis pigmentosa reveals a genotype-phenotype correlation.

PURPOSE: To analyze the genotype-phenotype correlation in patients with retinitis pigmentosa (RP) caused by mutations in the FAM161A, DHDDS, or MAK genes using ultra-widefield fundus autofluorescence (UWF-FAF) imaging. METHODS: Retrospective case series of patients with autosomal recessive RP (ARRP) with confirmed causative genetic mutations and available UWF-FAF imaging data. The UWF-FAF data were graded in a blinded fashion using the following criteria: the pattern of macular abnormalities on FAF, the presence or absence of horizontal linear hyperautofluorescence, the extent of decreased autofluorescence (DAF), the shape of DAF, and the presence of hyperautofluorescence at the optic disk. RESULTS: A total of 43 patients (mean age of 47 ± 16 years, ranging from 17 to 79 years) with ARRP (86 eyes) were included in our analysis. Genotyping data revealed biallelic mutations in the FAM161A, DHDDS, and MAK genes in 20, 12, and 11 patients, respectively. We found significant differences between the three groups with respect to the pattern of macular abnormalities on FAF (p = 0.001), DAF configuration (p = 0.007), and extent of DAF (p = 0.037). The largest difference between groups was found for macular abnormalities on FAF, with DHDDS patients differing significantly from the MAK and FAM161A groups (p = 0.001). Specifically, DHDDS patients had a more abnormal macular FAF pattern and more widespread decrease in peripheral autofluorescence. No other parameters differed significantly between the three groups. CONCLUSIONS: Patients with ARRP can present with specific UWF-FAF patterns based on the underlying causative gene. Future studies are warranted in order to expand this analysis to include additional genes, mutations, and patients as well as assessment of disease progression by following patients over longer periods of time.

Autoimmune retinopathy: clinical, electrophysiological, and immunological features in nine patients with long-term follow-up.

PURPOSE: We aim to report on the clinical, imaging, immunological, and electrophysiological features of patients with autoimmune retinopathy (AIR) with long-term follow-up. METHODS: Single-center, retrospective study of a consecutive group of AIR patients treated in a tertiary academic medical center. RESULTS: Included were nine patients with a mean ± SD age at presentation of 65 ± 13 years and a median follow-up of 63 months (range 18-120). Five patients were known to have cancer. Median interval between onset of ocular symptoms and diagnosis of AIR was 36 months. Mean baseline and final LogMAR visual acuity were 0.72 ± 0.9 and 1.1 ± 1.2, respectively (p = 0.17). The most common funduscopic findings included optic atrophy and bone-spicule-like pigmentation. Thinning of the nerve fiber layer was the most frequent optical coherence tomographic abnormality. Electroretinographic (ERG) recordings demonstrated variably reduced cone- and rod-derived amplitudes in the majority of eyes at presentation. The most commonly detected anti-retinal antibody was anti-α-enolase. Treatment included immunomodulatory therapy and plasmapheresis. ERG tests showed stability in 64% of eyes throughout the treatment period. CONCLUSION: This study highlights the importance of maintaining a high index of suspicion of AIR, particularly in late middle-aged and elderly patients with "unexplained" visual loss, in light of the non-specific posterior segment signs and the inconsistency of the routinely used ancillary tests.

Translational Read-Through Drugs (TRIDs) Are Able to Restore Protein Expression and Ciliogenesis in Fibroblasts of Patients with Retinitis Pigmentosa Caused by a Premature Termination Codon in FAM161A.

Ataluren and Gentamicin are translational readthrough drugs (TRIDs) that induce premature termination codon (PTC) readthrough, resulting in the production of full-length proteins that usually harbor a single missense substitution. FAM161A is a ciliary protein which is expressed in photoreceptors, and pathogenic variants in this gene cause retinitis pigmentosa (RP). Applying TRIDs on fibroblasts from RP patients due to PTC in the FAM161A (p.Arg523*) gene may uncover whether TRIDs can restore expression, localization and function of this protein. Fibroblasts from six patients and five age-matched controls were starved prior to treatment with ataluren or gentamicin, and later FAM161A expression, ciliogenesis and cilia length were analyzed. In contrast to control cells, fibroblasts of patients did not express the FAM161A protein, showed a lower percentage of ciliated cells and grew shorter cilia after starvation. Ataluren and Gentamicin treatment were able to restore FAM161A expression, localization and co-localization with α-tubulin. Ciliogenesis and cilia length were restored following Ataluren treatment almost up to a level which was observed in control cells. Gentamicin was less efficient in ciliogenesis compared to Ataluren. Our results provide a proof-of-concept that PTCs in FAM161A can be effectively suppressed by Ataluren or Gentamicin, resulting in a full-length functional protein.

A deep intronic substitution in CNGB3 is one of the major causes of achromatopsia among Jewish patients.

Purpose: Although most (or even all) genes that can cause achromatopsia (ACHM) when mutated are known, some patients are still negative for mutations even after screening the coding sequence of all known genes. Our aim was to characterize the genetic and clinical aspects of a deep intronic (c.1663-1205G>A, IVS14-1205G>A) CNGB3 variant. Methods: Clinical evaluation included visual acuity testing, refractive error, a full clinical eye exam, full-field electroretinography (ffERG), color vision testing, and retinal imaging. Genetic analysis of CNGB3 exons, as well as part of intron 14, was performed by Sanger sequencing of PCR products. Results: Screening for the CNGB3 c.1663-1205G>A variant revealed 17 patients belonging to 12 unrelated families who were either homozygous for this variant (7 cases, 5 families) or heterozygous in combination with another heterozygous known CNGB3 mutation (10 cases, 7 families). All patients were diagnosed with cone-dominated disease, mainly complete ACHM. In all cases, the disease had an early, congenital onset. Visual acuity was markedly impaired, ranging between 0.07 and 0.32 on the Early Treatment Diabetic Retinopathy Study (ETDRS) scale (logarithm of the minimum angle of resolution [LogMAR] +1.18 to +0.50), with a mean visual acuity of 0.15 ETDRS (LogMAR +0.80). Additional typical signs of ACHM, including impaired color vision, light aversion, and nystagmus, were also noted in all patients. As is common in ACHM, fundus exams were largely unremarkable in most patients, with mild foveal RPE changes seen in some cases at older ages. ERG was available for 14 out of 17 patients, and in all of them-including infants from the age of 6 months-cone responses were nondetectable. In a few cases, rod involvement was also evident, with a mild reduction of amplitudes. Optical coherence tomography (OCT) imaging showed irregularity of the ellipsoid zone in the foveal area in some patients. Conclusions: CNGB3 is the most common cause of ACHM in patients of European descent; this is mainly due to a panethnic founder mutation, c.1148del. Here, we report on an intronic CNGB3 variant that is more frequent than the c.1148del mutation in our cohort of Jewish patients. Among our ACHM cohort, 63.7% of patients had biallelic CNGA3 mutations and 26.4% had biallelic CNGB3 mutations. The phenotype of patients harboring the intronic mutation falls largely within the spectrum commonly seen in ACHM. Since gene therapy for CNGB3 is currently under investigation, these patients might benefit from this promising therapy. Given that this variant is not detectable by current commonly used genetic testing platforms, these patients could easily be missed.

Heterozygous deletions of noncoding parts of the PRPF31 gene cause retinitis pigmentosa via reduced gene expression.

Purpose: Heterozygous mutations in the gene PRPF31, encoding a pre-mRNA splicing factor, cause autosomal dominant retinitis pigmentosa (adRP) with reduced penetrance. At the molecular level, pathogenicity results from haploinsufficiency, as the largest majority of such mutations trigger nonsense-mediated mRNA decay or involve large deletions of coding exons. We investigated genetically two families with a history of adRP, one of whom showed incomplete penetrance. Methods: All patients underwent thorough ophthalmological examination, including electroretinography (ERG) and Goldmann perimetry. Array-based comparative genomic hybridization (aCGH) and multiplex ligation-dependent probe amplification (MLPA) were used to map heterozygous deletions, while real-time PCR on genomic DNA and long-range PCR allowed resolving the mutations at the base-pair level. PRPF31 transcripts were quantified with real-time PCR on patient-derived lymphoblastoid cell lines. Results: We identified two independent deletions affecting the promoter and the 5' untranslated region (UTR) of PRPF31 but leaving its coding sequence completely unaltered. Analysis of PRPF31 mRNA from lymphoblastoid cell lines from one of these families showed reduced levels of expression in patients versus controls, probably due to the heterozygous ablation of its promoter sequences. Conclusions: In addition to reporting the identification of two novel noncoding deletions in PRPF31, this study provides strong additional evidence that mRNA-mediated haploinsufficiency is the primary cause of pathogenesis for PRPF31-linked adRP.

SENIOR-LØKEN SYNDROME: A Case Series and Review of the Renoretinal Phenotype and Advances of Molecular Diagnosis.

PURPOSE: To report genetic and clinical findings in a case series of 10 patients from eight unrelated families diagnosed with Senior-Løken syndrome. METHODS: A retrospective study of patients with Senior-Løken syndrome. Data collected included clinical findings electroretinography and ocular imaging. Genetic analysis was based on molecular inversion probes, whole-exome sequencing (WES), and Sanger sequencing. RESULTS: All patients who underwent electrophysiology (8/10) had widespread photoreceptor degeneration. Genetic analysis revealed two mutations in NPHP1, two mutations in NPHP4, and two mutations in IQCB1 (NPHP5). Five of the six mutations identified in the current study were found in a single family each in our cohort. The IQCB1-p.R461* mutation has been identified in 3 families. Patients harboring mutations in IQCB1 were diagnosed with Leber congenital amaurosis, while patients with NPHP4 and NPHP1 mutations showed early and sector retinitis pigmentosa, respectively. Full-field electroretinography was extinct for 6 of 10 patients, moderately decreased for two, and unavailable for another 2 subjects. Renal involvement was evident in 7/10 patients at the time of diagnosis. Kidney function was normal (based on serum creatinine) in patients younger than 10 years. Mutations in IQCB1 were associated with high hypermetropia, whereas mutations in NPHP4 were associated with high myopia. CONCLUSION: Patients presenting with infantile inherited retinal degeneration are not universally screened for renal dysfunction. Modern genetic tests can provide molecular diagnosis at an early age and therefore facilitate early diagnosis of renal disease with recommended periodic screening beyond childhood and family planning.

Cell-Based Therapies for Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) is a leading cause of blindness worldwide. The pathogenesis of AMD involves dysfunction and loss of the retinal pigment epithelium (RPE), a monolayer of cells that provide nourishment and functional support for the overlying photoreceptors. RPE cells in mammals are not known to divide, renew or regenerate in vivo, and in advanced AMD, RPE loss leads to degeneration of the photoreceptors and impairment of vision. One possible therapeutic approach would be to support and replace the failing RPE cells of affected patients, and indeed moderate success of surgical procedures in which relatively healthy autologous RPE from the peripheral retina of the same eye was transplanted under the retina in the macular area suggested that RPE replacement could be a means to attenuate photoreceptor cell loss. This prompted exploration of the possibility to use pluripotent stem cells (PSCs) as a potential source for "healthy and young" RPE cells for such cell-based therapy of AMD. Various approaches ranging from the use of allogeneic embryonic stem cells to autologous induced pluripotent stem cells are now being tested within early clinical trials. Such PSC-derived RPE cells are either injected into the subretinal space as a suspension, or transplanted as a monolayer patch upon scaffold support. Although most of these approaches are at early clinical stages, safety of the RPE product has been demonstrated by several of these studies. Here, we review the concept of cell-based therapy of AMD and provide an update on current progress in the field of RPE transplantation.

A nationwide genetic analysis of inherited retinal diseases in Israel as assessed by the Israeli inherited retinal disease consortium (IIRDC).

Inherited retinal diseases (IRDs) cause visual loss due to dysfunction or progressive degeneration of photoreceptors. These diseases show marked phenotypic and genetic heterogeneity. The Israeli IRD consortium (IIRDC) was established in 2013 with the goal of performing clinical and genetic mapping of the majority of Israeli IRD patients. To date, we recruited 2,420 families including 3,413 individuals with IRDs. On the basis of our estimation, these patients represent approximately 40% of Israeli IRD patients. To the best of our knowledge, this is, by far, the largest reported IRD cohort, and one of the first studies addressing the genetic analysis of IRD patients on a nationwide scale. The most common inheritance pattern in our cohort is autosomal recessive (60% of families). The most common retinal phenotype is retinitis pigmentosa (43%), followed by Stargardt disease and cone/cone-rod dystrophy. We identified the cause of disease in 56% of the families. Overall, 605 distinct mutations were identified, of which 12% represent prevalent founder mutations. The most frequently mutated genes were ABCA4, USH2A, FAM161A, CNGA3, and EYS. The results of this study have important implications for molecular diagnosis, genetic screening, and counseling, as well as for the development of new therapeutic strategies for retinal diseases.

Whole-exome sequencing reveals POC5 as a novel gene associated with autosomal recessive retinitis pigmentosa.

Retinitis pigmentosa (RP), the most common form of inherited retinal degeneration, is associated with different groups of genes, including those encoding proteins involved in centriole and cilium biogenesis. Exome sequencing revealed a homozygous nonsense mutation [c.304_305delGA (p. D102*)] in POC5, encoding the Proteome Of Centriole 5 protein, in a patient with RP, short stature, microcephaly and recurrent glomerulonephritis. The POC5 gene is ubiquitously expressed, and immunohistochemistry revealed a distinct POC5 localization at the photoreceptor connecting cilium. Morpholino-oligonucleotide-induced knockdown of poc5 translation in zebrafish resulted in decreased length of photoreceptor outer segments and a decreased visual motor response, a measurement of retinal function. These phenotypes could be rescued by wild-type human POC5 mRNA. These findings demonstrate that Poc5 is important for normal retinal development and function. Altogether, this study presents POC5 as a novel gene involved autosomal recessively inherited RP, and strengthens the hypothesis that mutations in centriolar proteins are important cause of retinal dystrophies.