Non-syndromic Retinitis Pigmentosa Research Articles

P.arg102ser is a common Pde6a mutation causing autosomal recessive retinitis pigmentosa in Pakistani families.

To explore the genetic cause of autosomal recessive retinitis pigmentosa in consanguineous families. The multi-centre study was conducted from July 2015 to June 2018 at Liaquat University of Medical and Health Sciences, Jamshoro, the University of Sindh, Jamshoro, and Islamia University, Bahawalpur, Pakistan, and comprised families affected with non-syndromic autosomal recessive retinitis pigmentosa. Ophthalmological investigations were done to assess the fundus of the patients and the status of the disease. Pedigrees were drawn and family histories were recorded to find out the mode of inheritance. A 10cc sample of whole blood was obtained from each participant and deoxyribonucleic acid was extracted. Homozygosity mapping was performed using three short tandem repeat polymorphisms closely linked to phosphodiesterase 6A gene, and the linked families were Sanger-sequenced for identification of the mutation. Bioinformatic tools were used to design amplification refractory mutation system assay and to assess the protein structure and pathogenic effects of the mutation. In the 80 consanguineous families, there were 464 individuals, and, of them, 236(51%) were affected with their age ranging between 4 and 80 years. Family history and pedigree drawings revealed autosomal recessive retinitis pigmentosa with early childhood onset. Linkage analysis indicated the homozygosity in 6(7.5%) families. Sanger-sequencing revealed a common mutation c.304C>A (p.Arg102Ser); segregating with the disease in the linked families. The findings may offer effective genetic counselling and minimise disease penetration in consanguineous families.

Truncating Variants Contribute to Hearing Loss and Severe Retinopathy in USH2A-Associated Retinitis Pigmentosa in Japanese Patients

USH2A is a common causal gene of retinitis pigmentosa (RP), a progressive blinding disease due to retinal degeneration. Genetic alterations in USH2A can lead to two types of RP, non-syndromic and syndromic RP, which is called Usher syndrome, with impairments of vision and hearing. The complexity of the genotype–phenotype correlation in USH2A-associated RP (USH2A-RP) has been reported. Genetic and clinical characterization of USH2A-RP has not been performed in Japanese patients. In this study, genetic analyses were performed using targeted panel sequencing in 525 Japanese RP patients. Pathogenic variants of USH2A were identified in 36 of 525 (6.9%) patients and genetic features of USH2A-RP were characterized. Among 36 patients with USH2A-RP, 11 patients had syndromic RP with congenital hearing problems. Amino acid changes due to USH2A alterations were similarly located throughout entire regions of the USH2A protein structure in non-syndromic and syndromic RP cases. Notably, truncating variants were detected in all syndromic patients with a more severe retinal phenotype as compared to non-syndromic RP cases. Taken together, truncating variants could contribute to more serious functional and tissue damages in Japanese patients, suggesting important roles for truncating mutations in the pathogenesis of syndromic USH2A-RP.

The RUSH2A Study: Best-Corrected Visual Acuity, Full-Field Electroretinography Amplitudes, and Full-Field Stimulus Thresholds at Baseline.

PurposeThe purpose of this study was to evaluate baseline best corrected visual acuity (BCVA), full-field electroretinography (ERG), full-field stimulus thresholds (FST), and their relationship with baseline demographic and clinical characteristics in the Rate of Progression in Usher syndrome type 2 (USH2A)-related Retinal Degeneration (RUSH2A) multicenter study.MethodsParticipants had Usher syndrome type 2 (USH2, N = 80) or autosomal recessive nonsyndromic retinitis pigmentosa (ARRP, N = 47) associated with biallelic variants in the USH2A gene. Associations of demographic and clinical characteristics with BCVA, ERG, and FST were assessed with regression models.ResultsIn comparison to ARRP, USH2 had worse BCVA (median 79 vs. 82 letters; P < 0.001 adjusted for age), lower rod-mediated ERG b-wave amplitudes (median 0.0 vs. 6.6 µV; P < 0.001) and 30 Hz flicker cone-mediated ERG amplitudes (median 1.5 vs. 3.1 µV; P = 0.001), and higher (white, blue, and red) FST thresholds (means [−26, −31, −23 dB] vs. [−39, −45, −28 dB]; P < 0.001 for all stimuli). After adjusting for age, gender, and duration of vision loss, the difference in BCVA between diagnosis groups was attenuated (P = 0.09). Only diagnosis was associated with rod- and cone-mediated ERG parameters, whereas both genders (P = 0.04) and duration of visual loss (P < 0.001) also were associated with FST white stimulus.ConclusionsUSH2 participants had worse BCVA, ERG, and FST than ARRP participants. FST was strongly associated with duration of disease; it remains to be determined whether it will be a sensitive measure of progression.Translational RelevanceUsing standardized research protocols in RUSH2A, measures have been identified to monitor disease progression and treatment response and differentiate features of prognostic relevance between USH2 and ARRP participants with USH2A mutations.

Identifying haplotypes in recessive inherited retinal dystrophies using whole-genome linked-read sequencing.

Conventional next-generation sequencing methods, used in most gene panels, cannot separate maternally and paternally derived sequence information of distant variants. In recessive diseases, two or more equally plausible causative variants with unsolved phase information prevent accurate molecular diagnosis. In reality, close relatives might be unavailable for segregation analysis. Here, we utilized whole genome linked-read sequencing to assign variants to haplotypes in two patients with inherited retinal dystrophies. Patient 1 with macular dystrophy had variants c.3442T>C, p.(Cys1148Arg), c.4209G>T, p.(Glu1403Asp), and c.1182C>T, p.(Cys394=) in CRB1, and Patient 2 with nonsyndromic retinitis pigmentosa had c.1328T>A, p.(Val443Asp) and c.3032C>G, p.(Ser1011*) in AHI1. The relatives were not available for genotyping. Using whole genome linked-read sequencing we phased the variants to haplotypes providing genetic background for the retinal dystrophies. In future, when the price of sequencing methods that provides long-read data decreases and their read-depth and accuracy increases, they are probably considered the primary or adjunctive sequencing methods in genetic testing, allowing the immediate collection of phase information and thus obviating the need for the carrier testing and segregation analysis.

Recent Developments on the major genes involved in retinitis pigmentosa

Retinitis pigmentosa (RP) is a common retinal dystrophy that affects millions of individuals, of both sexes, worldwide. The age of onset and the phenotypic characteristics vary between patients of different ethnicities. It may be syndromic when it coexists with several syndromes, like Usher syndrome, or non-syndromic. It follows autosomal dominant, autosomal recessive or X-linked inheritance. RP is genetically heterogeneous with, approximately, one hundred genes identified to date. The present mini review includes articles about the pathogenesis of syndromic and non-syndromic RP. Eighty-seven papers written in English and published in the last decade, about the pathogenesis of RP were reviewed and analyzed in order to summarize and highlight the major genes implicated in RP. We identified more than 80 genes associated with syndromic and 30 genes with non-syndromic RP. Among them RHO and RPGR, followed by PRPH2, PRPF31 and RP2 are the major genes involved in RP.

Diagnostic and Therapeutic Challenges due to Psychosis and Catatonia in Non-syndromic Retinitis Pigmentosa: A Case Report.

Diagnostic and Therapeutic Challenges due to Psychosis and Catatonia in Non-syndromic Retinitis Pigmentosa: A Case Report.

Multimodal imaging and genetic characteristics of Chinese patients with USH2A-associated nonsyndromic retinitis pigmentosa.

BackgroundTo determine the clinical characteristics and molecular genetic background responsible for USH2A mutations associated with nonsyndromic retinitis pigmentosa (RP) in five Chinese families, a retrospective cross‐sectional study was performed.MethodsData on detailed history and comprehensive ophthalmological examinations were extracted from medical charts. Genomic DNA was sequenced by whole‐exome sequencing. The pathogenicity predictions were evaluated by in silico analysis. The structural modeling of the wide‐type and mutant USH2A proteins was displayed based on the I‐Tasser software.ResultsThe ultra‐wide‐field fundus imaging showed a distinctive pattern of hyperautofluorescence in the parafoveal ring with macular sparing. Ten USH2A variants were detected, including seven missense mutations, two splicing mutations, and one insertion mutation. Six of these variants have already been reported, and the remaining four were novel. Of the de novo mutations, the p.C931Y and p.G4489S mutations were predicted to be deleterious or probably damaging; the p.M4853V mutation was predicted to be neutral or benign; and the IVS22+3A>G mutation was a splicing mutation that could influence mRNA splicing and affect the formation of the hairpin structure of the USH2A protein.ConclusionsOur data further confirm that USH2A protein plays a pivotal role in the maintenance of photoreceptors and expand the spectrum of USH2A mutations that are associated with nonsyndromic RP in Chinese patients.

FLVCR1-related disease as a rare cause of retinitis pigmentosa and hereditary sensory autonomic neuropathy

FLVCR1 encodes for a transmembrane heme exporter protein and it is known to cause a rare form of syndromic retinitis pigmentosa: posterior column ataxia with retinitis pigmentosa. Recently, the FLVCR1-associated phenotype has been expanded with sporadic reports of hereditary sensory-autonomic neuropathy or non-syndromic retinitis pigmentosa. Here, we report a 23-year- old female with early onset hypomyelinating sensory-autonomic neuropathy and retinitis pigmentosa. Both features were present since childhood. The patient developed signs of advanced retinitis pigmentosa by the age of 10 years leading to legal blindness after the age of 18. Following candidate gene panel testing, which was negative, whole exome sequencing revealed compound heterozygous pathogenic FLVCR1 variants: NM_014053.3: c.3G > T; p.(Met1?) and NM_014053.3: c.730G > A; p.(Gly244Ser), the latter variant is novel. In this report we highlight the association of retinitis pigmentosa with hypomyelinating sensory-autonomic neuropathy, which could be underdiagnosed due to variable severity. To summarize, the phenotypic heterogeneity of FLVCR1 variants is broad and should include retinitis pigmentosa along with range of neurological features.

A genetic and clinical study of individuals with nonsyndromic retinopathy consequent upon sequence variants in HGSNAT, the gene associated with Sanfilippo C mucopolysaccharidosis.

Pathogenic variants in the gene HGSNAT (heparan‐α‐glucosaminide N‐acetyltransferase) have been reported to underlie two distinct recessive conditions, depending on the specific genotype, mucopolysaccharidosis type IIIC (MPSIIIC)—a severe childhood‐onset lysosomal storage disorder, and adult‐onset nonsyndromic retinitis pigmentosa (RP). Here we describe the largest cohort to‐date of HGSNAT‐associated nonsyndromic RP patients, and describe their retinal phenotype, leukocyte enzymatic activity, and likely pathogenic genotypes. We identified biallelic HGSNAT variants in 17 individuals (15 families) as the likely cause of their RP. None showed any other symptoms of MPSIIIC. All had a mild but significant reduction of HGSNAT enzyme activity in leukocytes. The retinal condition was generally of late‐onset, showing progressive degeneration of a concentric area of paramacular retina, with preservation but reduced electroretinogram responses. Symptoms, electrophysiology, and imaging suggest the rod photoreceptor to be the cell initially compromised. HGSNAT enzymatic testing was useful in resolving diagnostic dilemmas in compatible patients. We identified seven novel sequence variants [p.(Arg239Cys); p.(Ser296Leu); p.(Phe428Cys); p.(Gly248Ala); p.(Gly418Arg), c.1543‐2A>C; c.1708delA], three of which were considered to be retina‐disease‐specific alleles. The most prevalent retina‐disease‐specific allele p.(Ala615Thr) was observed heterozygously or homozygously in 8 and 5 individuals respectively (7 and 4 families). Two siblings in one family, while identical for the HGSNAT locus, but discordant for retinal disease, suggest the influence of trans‐acting genetic or environmental modifying factors.

USH2A variants in Chinese patients with Usher syndrome type II and non-syndromic retinitis pigmentosa

AimsTo reveal the Usher syndrome type IIA (USH2A) gene variant profile in a large cohort of Chinese patients with non-syndromic retinitis pigmentosa (RP) or Usher syndrome type II (USH2) and...

Baseline Visual Field Findings in the RUSH2A Study: Associated Factors and Correlation With Other Measures of Disease Severity

To report baseline visual fields in the Rate of Progression in USH2A-related Retinal Degeneration (RUSH2A) study. Cross-sectional study within a natural history study. Setting: multicenter, international. Usher syndrome type 2 (USH2) (n= 80) or autosomal recessive nonsyndromic retinitis pigmentosa (ARRP) (n= 47) associated with biallelic disease-causing sequence variants in USH2A. Repeatability of full-field static perimetry (SP) and between-eye symmetry of kinetic perimetry (KP) were evaluated with intraclass correlation coefficients (ICCs). The association of demographic and clinical characteristics with total hill of vision (VTOT) was assessed with general linear models. Associations between VTOT and other functional and morphologic measures were assessed using Spearman correlation coefficients and t tests. VTOT (SP) and III4e isopter area (KP). USH2 participants had more severe visual field loss than ARRP participants (P < .001, adjusting for disease duration, age of enrollment). Mean VTOT measures among 3 repeat tests were 32.7 ± 24.1, 31.2 ± 23.4, and 31.7 ± 23.9 decibel-steradians (intraclass correlation coefficient [ICC]= 0.96). Better VA, greater photopic ERG 30-Hz flicker amplitudes, higher mean microperimetry sensitivity, higher central subfield thickness, absence of macular cysts, and higher III4e seeing area were associated with higher VTOT (all r > .48; P < .05). Mean III4e isopter areas for left (4561 ± 4426 squared degrees) and right eyes (4215 ± 4300 squared degrees) were concordant (ICC= 0.94). USH2 participants had more visual field loss than participants with USH2A-related ARRP, adjusting for duration of disease and age of enrollment. VTOT was repeatable and correlated with other functional and structural metrics, suggesting it may be a good summary measure of disease severity in patients with USH2A-related retinal degeneration.

Qualitative Interviews to Better Understand the Patient Experience and Evaluate Patient-Reported Outcomes (PRO) in RLBP1 Retinitis Pigmentosa (RLBP1 RP).

IntroductionRLBP1 RP is an autosomal recessive form of retinitis pigmentosa (RP), characterized by night blindness, prolonged dark adaptation, constricted visual fields and impaired macular function. This study aimed to better understand the patient experience of RLBP1 RP and evaluate the content validity of existing patient reported outcome (PRO) instruments in this condition.MethodsSemi-structured concept elicitation and cognitive debriefing interviews were conducted with RLBP1 RP patients in Canada and Sweden. Interviews started with open-ended concept elicitation questioning, and then patients were cognitively debriefed on The National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25), the Low Luminance Questionnaire (LLQ) and four light/dark adaptation items of the Visual Activities Questionnaire (VAQ). Qualitative interviews were also conducted with three expert clinicians. Anonymized, verbatim transcripts were analyzed using thematic analysis.ResultsTwenty-one patients were interviewed (Canada n = 10; Sweden n = 11). Symptoms reported included night blindness (n = 21), difficulty adapting to changes in lighting (n = 21) and difficulties seeing in bright lighting (n = 18). Patients experienced substantial impacts on daily activities (n = 21) and physical functioning (n = 17). Patients had difficulty interpreting and selecting a response for some items in the NEI VFQ-25 and LLQ. Some items were not relevant to patients’ disease experience. There were both gaps and overlaps in the conceptual coverage of the instruments.ConclusionsVisual impairment due to RLBP1 RP has a substantial impact on physical functioning and daily activities. To adequately assess all important symptoms and associated functional impacts in RLBP1 RP, it is recommended to either modify one or more existing instruments or to develop a new non-syndromic RP specific instrument.Electronic supplementary materialThe online version of this article (10.1007/s12325-020-01275-4) contains supplementary material, which is available to authorized users.

Using inducible lentiviral vectors to generate induced pluripotent stem cell line ZOCi001-A from peripheral blood cells of a patient with CRB1-/- retinitis pigmentosa.

We isolated peripheral blood mononuclear cells from a patient diagnosed with early-onset non-syndromic retinitis pigmentosa caused by compound heterozygous mutations in CRB1 (NM_001257965): c.1369C>T (p.R457X) and c.2027C>T (p.T676M). These cells were transfected with four inducible plasmids encoding human OCT4, SOX2, KLF4 or C-MYC together. Transfected cells were induced to form pluripotent stem cells (iPSCs) expressing the pluripotent stem cell markers SOX2, OCT4, KLF4, SSEA4 and NANOG and presenting a normal karyotype. These cells could be differentiated into three germ layers as well as retinal organoids, and thus provide a valuable cellular model for the study of development of major retina diseases.

Clinical and preclinical therapeutic outcome metrics for USH2A-related disease.

USH2A variants are the most common cause of Usher syndrome type 2, characterized by congenital sensorineural hearing loss and retinitis pigmentosa (RP), and also contribute to autosomal recessive non-syndromic RP. Several treatment strategies are under development; however, sensitive clinical trial endpoint metrics to determine therapeutic efficacy have not been identified. In the present study, we have performed longitudinal retrospective examination of the retinal and auditory symptoms in (i) 56 biallelic molecularly confirmed USH2A patients and (ii) ush2a mutant zebrafish to identify metrics for the evaluation of future clinical trials and rapid preclinical screening studies. The patient cohort showed a statistically significant correlation between age and both rate of constriction for the ellipsoid zone length and hyperautofluorescent outer retinal ring area. Visual acuity and pure tone audiograms are not suitable outcome measures. Retinal examination of the novel ush2au507 zebrafish mutant revealed a slowly progressive degeneration of predominantly rods, accompanied by rhodopsin and blue cone opsin mislocalization from 6 to 12 months of age with lysosome-like structures observed in the photoreceptors. This was further evaluated in the ush2armc zebrafish model, which revealed similar changes in photopigment mislocalization with elevated autophagy levels at 6 days post fertilization, indicating a more severe genotype-phenotype correlation and providing evidence of new insights into the pathophysiology underlying USH2A-retinal disease.

Identification of 13 novel USH2A mutations in Chinese retinitis pigmentosa and Usher syndrome patients by targeted next-generation sequencing.

Background: The USH2A gene encodes usherin, a basement membrane protein that is involved in the development and homeostasis of the inner ear and retina. Mutations in USH2A are linked to Usher syndrome type II (USH II) and non-syndromic retinitis pigmentosa (RP). Molecular diagnosis can provide insight into the pathogenesis of these diseases, facilitate clinical diagnosis, and identify individuals who can most benefit from gene or cell replacement therapy. Here, we report 21 pathogenic mutations in the USH2A gene identified in 11 Chinese families by using the targeted next-generation sequencing (NGS) technology.Methods: In all, 11 unrelated Chinese families were enrolled, and NGS was performed to identify mutations in the USH2A gene. Variant analysis, Sanger validation, and segregation tests were utilized to validate the disease-causing mutations in these families.Results: We identified 21 pathogenic mutations, of which 13, including 5 associated with non-syndromic RP and 8 with USH II, have not been previously reported. The novel variants segregated with disease phenotype in the affected families and were absent from the control subjects. In general, visual impairment and retinopathy were consistent between the USH II and non-syndromic RP patients with USH2A mutations.Conclusions: These findings provide a basis for investigating genotype–phenotype relationships in Chinese USH II and RP patients and for clarifying the pathophysiology and molecular mechanisms of the diseases associated with USH2A mutations.

Application of targeted panel sequencing and whole exome sequencing for 76 Chinese families with retinitis pigmentosa.

BackgroundThis study aimed to identify the gene variants and molecular etiologies in 76 unrelated Chinese families with retinitis pigmentosa (RP).MethodsIn total, 76 families with syndromic or nonsyndromic RP, diagnosed on the basis of clinical manifestations, were recruited for this study. Genomic DNA samples from probands were analyzed by targeted panels or whole exome sequencing. Bioinformatics analysis, Sanger sequencing, and available family member segregation were used to validate sequencing data and confirm the identities of disease‐causing genes.ResultsThe participants enrolled in the study included 62 families that exhibited nonsyndromic RP, 13 that exhibited Usher syndrome, and one that exhibited Bardet–Biedl syndrome. We found that 43 families (56.6%) had disease‐causing variants in 15 genes, including RHO, PRPF31, USH2A, CLRN1, BBS2, CYP4V2, EYS, RPE65, CNGA1, CNGB1, PDE6B, MERTK, RP1, RP2, and RPGR; moreover, 12 families (15.8%) had only one heterozygous variant in seven autosomal recessive RP genes, including USH2A, EYS, CLRN1, CERKL, RP1, CRB1, and SLC7A14. We did not detect any variants in the remaining 21 families (27.6%). We also identified 67 potential pathogenic gene variants, of which 24 were novel.ConclusionThe gene variants identified in this study expand the variant frequency and spectrum of RP genes; moreover, the identification of these variants supplies foundational clues for future RP diagnosis and therapy.

Usher syndrome: clinical features, molecular genetics and advancing therapeutics.

Usher syndrome has three subtypes, each being clinically and genetically heterogeneous characterised by sensorineural hearing loss and retinitis pigmentosa (RP), with or without vestibular dysfunction. It is the most common cause of deaf–blindness worldwide with a prevalence of between 4 and 17 in 100 000. To date, 10 causative genes have been identified for Usher syndrome, with MYO7A accounting for >50% of type 1 and USH2A contributing to approximately 80% of type 2 Usher syndrome. Variants in these genes can also cause non-syndromic RP and deafness. Genotype–phenotype correlations have been described for several of the Usher genes. Hearing loss is managed with hearing aids and cochlear implants, which has made a significant improvement in quality of life for patients. While there is currently no available approved treatment for the RP, various therapeutic strategies are in development or in clinical trials for Usher syndrome, including gene replacement, gene editing, antisense oligonucleotides and small molecule drugs.

Novel mutations in the 3-box motif of the BACK domain of KLHL7 associated with nonsyndromic autosomal dominant retinitis pigmentosa

BackgroundMutations in the Kelch-like protein 7 (KLHL7) represent a recently described and, to date, poorly characterized etiology of inherited retinal dystrophy. Dominant mutations in KLHL7 are a cause of isolated, non-syndromic retinitis pigmentosa (RP). In contrast, recessive loss-of-function mutations are known to cause Crisponi or Bohring-Opitz like cold induced sweating syndrome-3 (BOS-3). In this study, the phenotype and progression of five unrelated patients with KLHL7 mediated autosomal dominant RP (adRP) are characterized. Clinical evaluation of these patients involved a complete ophthalmic exam, full-field electroretinography (ffERG), and imaging, including fundus photography, spectral domain optical coherence tomography (SD-OCT), short wavelength fundus autofluorescence (SW-AF), and near-infrared fundus autofluorescence (NIR-AF). Molecular diagnoses were performed using whole-exome sequencing or gene panel testing. Disease progression was monitored in three patients with available data for a mean follow up time of 4.5 ± 2.9 years. Protein modeling was performed for all variants found in this study in addition to those documented in the literature for recessive loss-of-function alleles causing Crisponi or Bohring-Opitz like cold-induced sweating syndrome.ResultsGenetic testing in three patients identified two novel variants within the 3-box motif of the BACK domain: c.472 T > C:p.(Cys158Arg) and c.433A > T:p.(Asn145Tyr). Clinical imaging demonstrated hyperautofluorescent ring formation on both SW-AF and NIR-AF in three patients, with diffuse peripheral and peripapillary atrophy seen in all but one case. SD-OCT demonstrated a phenotypic spectrum, from parafoveal atrophy of the outer retina with foveal sparing to widespread retinal thinning and loss of photoreceptors. Incidence of cystoid macular edema was high with four of five patients affected. Protein modeling of dominant alleles versus recessive loss-of-function alleles showed dominant alleles localized to the BTB and BACK domains while recessive alleles were found in the Kelch domain.ConclusionsWe report the phenotype in five patients with KLHL7 mediated adRP, two novel coding variants, and imaging biomarkers using SW-AF and NIR-AF. These findings may influence future gene-based therapies for adRP and pave the way for mechanistic studies that elucidate the pathogenesis of KLHL7-mediated RP.

Modeling Retinitis Pigmentosa: Retinal Organoids Generated From the iPSCs of a Patient With the USH2A Mutation Show Early Developmental Abnormalities.

Retinitis pigmentosa (RP) represents a group of inherited retinopathies with early-onset nyctalopia followed by progressive photoreceptor degeneration causing irreversible vision loss. Mutations in USH2A are the most common cause of non-syndromic RP. Here, we reprogrammed induced pluripotent stem cells (iPSCs) from a RP patient with a mutation in USH2A (c.8559-2A > G/c.9127_9129delTCC). Then, multilayer retinal organoids including neural retina (NR) and retinal pigment epithelium (RPE) were generated by three-step “induction-reversal culture.” The early retinal organoids derived from the RP patient with the USH2A mutation exhibited significant defects in terms of morphology, immunofluorescence staining and transcriptional profiling. To the best of our knowledge, the pathogenic mutation (c.9127_9129delTCC) in USH2A has not been reported previously among RP patients. Notably, the expression of laminin in the USH2A mutation organoids was significantly lower than in the iPSCs derived from healthy, age- and sex-matched controls during the retinal organogenesis. We also observed that abnormal retinal neuroepithelium differentiation and polarization caused defective retinal progenitor cell development and retinal layer formation, disordered organization of NRs in the presence of the USH2A mutation. Furthermore, the USH2A mutation bearing RPE cells presented abnormal morphology, lacking pigmented foci and showing an apoptotic trend and reduced expression of specific makers, such as MITF, PEDF, and RPE65. In addition, the USH2A mutation organoids had lower expression of cilium-associated (especially CFAP43, PIFO) and dopaminergic synapse-related genes (including DLGAP1, GRIK1, SLC17A7, and SLC17A8), while there was higher expression of neuron apoptotic process-related genes (especially HIF1A, ADARB1, and CASP3). This study may provide essential assistance in the molecular diagnosis and screening of RP. This work recapitulates the pathogenesis of USH2A using patient-specific organoids and demonstrated that alterations in USH2A function due to mutations may lead to cellular and molecular abnormalities.

Whole-exome sequencing identifies novel mutations in genes responsible for retinitis pigmentosa in 2 nonconsanguineous Chinese families.

To detect the pathogenetic mutations responsible for nonsyndromic autosomal recessive retinitis pigmentosa (RP) in 2 nonconsanguineous Chinese families. The clinical data, including detailed medical history, best corrected visual acuity (BCVA), slit-lamp biomicroscope examination, fundus photography, optical coherence tomography, static perimetry, and full field electroretinogram, were collected from the members of 2 nonconsanguineous Chinese families preliminarily diagnosed with RP. Genomic DNA was extracted from the probands and other available family members; whole-exome sequencing was conducted with the DNA samples provided by the probands, and all mutations detected by whole-exome sequencing were verified using Sanger sequencing in the probands and the other available family members. The verified novel mutations were further sequenced in 192 ethnicity matched healthy controls. The patients from the 2 families exhibited the typical symptoms of RP, including night blindness and progressive constriction of the visual field, and the fundus examinations showed attenuated retinal arterioles, peripheral bone spicule pigment deposits, and waxy optic discs. Whole-exome sequencing revealed a novel nonsense mutation in FAM161A (c.943A>T, p.Lys315*) and compound heterozygous mutations in RP1L1 (c.56C>A, p.Pro19His; c.5470C>T, p.Gln1824*). The nonsense c.5470C>T, p.Gln1824* mutation was novel. All mutations were verified by Sanger sequencing. The mutation p.Lys315* in FAM161A co-segregated with the phenotype, and all the nonsense mutations were absent from the ethnicity matched healthy controls and all available databases. We identify 2 novel mutations in genes responsible for autosomal recessive RP, and the mutation in FAM161A is reported for the first time in a Chinese population. Our result not only enriches the knowledge of the mutation frequency and spectrum in the genes responsible for nonsyndromic RP but also provides a new target for future gene therapy.