Novel mutations in the long isoform of the USH2A gene in patients with Usher syndrome type II or non-syndromic retinitis pigmentosa

Natural History of Microperimetry and Optical Coherence Tomography in USH2A-Retinopathy: A Structure-Function Association Study

PURPOSE

To describe the natural history of optical coherence tomography (OCT) and mesopic microperimetry (MP) parameters in the Rate of Progression of USH2A-related Retinal Degeneration (RUSH2A) study.

DESIGN

Multi-center, international, prospective, longitudinal natural history study.

METHODS

STUDY POPULATION: 105 participants with biallelic disease-causing variants in USH2A with a clinical diagnosis of Usher Syndrome or autosomal recessive retinitis pigmentosa who underwent annual testing over 4 years.

MAIN OUTCOME MEASURE(S)

Ellipsoid zone (EZ) area and central sub-field thickness (CST) on OCT. Mean sensitivity (MS) and mean pointwise sensitivity at predefined functional transition points (MSFTP) on MP.

RESULTS

102 and 94 participants met criteria for OCT and MP analysis, respectively. The average EZ area was 3.9 ± 5.3 mm2 at baseline which decreased to 3.3 ± 4.1 mm2 at 4 years [rate of change (ROC) (-0.18 mm2/year)]. The average CST decreased from 249.7 ± 35.6 to 244.1 ± 39.3 microns over 4 years (-2.14 microns/year). The average MP MS declined from 6.0 ± 5.1 dB (baseline) to 4.5 ± 4.2 (4 years) (-0.39 dB/year). The MSFTP significantly decreased over time [17.9 dB (baseline) to 10.8 dB (4 years)]. Notably, at 4 years, there was a meaningful decrease (≥ 7dB) in MSFTP in 46% of study eyes.

CONCLUSIONS

This study establishes the natural history of key structural and functional parameters in USH2A-retinopathy. The MSFTP is a novel, robust parameter that showed clinically meaningful change over time and is a promising tool to monitor treatment efficacy in clinical trials.

Nanoparticle-Based gene therapy strategies in retinal delivery

Vision loss and blindness are significant issues in both developed and developing countries. There are a wide variety of aetiologies that can cause vision loss, which are outlined in this review. Although treatment has significantly improved over time for some conditions, nearly half of all people with vision impairment are left untreated. Gene delivery is an emerging field that may assist with the treatment of some of these difficult to manage forms of vision loss. Here we review how a component of nanotechnology-based, non-viral gene delivery systems are being applied to help resolve vision impairment. This review focuses on the use of lipid and polymer nanoparticles, and quantum dots as gene delivery vectors to the eye. Finally, we also highlight some emerging technologies that may be useful in this discipline.

Characterization of Visual Field Loss Over 4 Years in the Rate of Progression in USH2A-Related Retinal Degeneration (RUSH2A) Study

PURPOSE

To report visual field loss using static perimetry (SP) and kinetic perimetry (KP) over 4 years in the Rate of Progression of USH2A-related Retinal Degeneration (RUSH2A) study.

DESIGN

Prospective, observational cohort study.

SUBJECTS, PARTICIPANTS, AND/OR CONTROLS

Participants had USH2A-related rod-cone degeneration, visual acuity ≥20/80, and KP III4e ≥10° at baseline in the study eye. Preserved cohorts with baseline visual fields sufficient to detect progression were identified.

METHODS

Participants were examined annually through 4 years. Mixed-effects models were used to estimate the annual, standardized rate, and percentage rates of change.

MAIN OUTCOME MEASURES

SP measures included hill of vision (total: VTOT, central 30°: V30, and peripheral: VPERIPH) and centrally weighted mean sensitivity (MScw). Percentages with 4-year progression exceeding the coefficient of repeatability (CoR) and with change meeting Food and Drug Administration (FDA)-recommended criteria were estimated. KP seeing area (dB-steradian (sr)/degree) for I4e, III4e, and V4e isopters was calculated.

RESULTS

The average decline with SP (95% CI) was 1.94 (1.62, 2.25) dB-sr/y for VTOT, 0.54 (0.45, 0.62) dB-sr/y for V30, 1.37 (1.11, 1.63) dB-sr/y for VPERIPH, and 0.56 (0.48, 0.64) dB/y for MScw. Average percentage decline per year was 8.6% (7.2, 10.0) for VTOT, 6.4% (5.3, 7.5) for V30, 13.6% (10.4, 16.7) for VPERIPH, and 5.6% (4.7, 6.4) for MScw. The standardized rate of change was greatest at -1.35 for MScw. Rates were higher in the preserved cohorts. Progression exceeding the CoR was 18% (11, 28) for VTOT, 21% (13, 31) for V30, 21% (13, 31) for VPERIPH and 17% (10, 27) for MScw. Progression exceeding an FDA-recommended threshold was 5% (2%, 12%) for all SP points and 45% (35%, 55%) for functional transition points. Average KP annual percentage decline was 13.1% (7.5, 18.5) for I4e, 12.1% (8.1,15.9) for III4e, and 9.2% (6.3,12.0) for V4e.

CONCLUSIONS

All quantitative perimetry measures declined over 4 years. Progression was greater than the CoR in a relatively low percentage of eyes (17%-21%); 45% exceeded the FDA-recommended threshold when only functional transition points were considered. Standardized rate of change was greatest for MScw. These measures are useful characterizations of vision loss in USH2A-related retinal degeneration.

Visual Acuity, Full-field Stimulus Thresholds, and Electroretinography for 4 Years in The Rate of Progression of USH2A-related Retinal Degeneration (RUSH2A) Study

Purpose

To describe progression of best-corrected visual acuity (BCVA), full-field stimulus thresholds (FST), and electroretinography (ERG) over 4 years in the USH2A-related Retinal Degeneration study and to assess their suitability as clinical trial endpoints.

Design

Prospective natural history study.

Participants

Participants (n = 105) with biallelic disease-causing sequence variants in USH2A and BCVA letter scores of ≥54 were included.

Methods

BCVA, FST, fundus-guided microperimetry, static perimetry, and spectral domain OCT were performed annually and ERG at baseline and 4 years only. Mixed effects models were used to estimate annual rates of change with 95% confidence intervals. Associations of change from baseline to 4 years between BCVA, FST, ERG, and other metrics were assessed with Spearman correlation coefficients (rs).

Main Outcome Measures

Best-corrected visual acuity, FST, and ERG.

Results

The annual rate of decline in BCVA was 0.83 (95% confidence interval: 0.65-1.02) letters/year. For FST, the change was 0.09 (0.07-0.11) log cd.s/m2/year for white threshold, 0.10 (0.08-0.12) log cd.s/m2/year for blue threshold, and 0.05 (0.04-0.06) log cd.s/m2/year for red threshold. Changes were 22.6 (17.4-28.2)%/year for white threshold, 26.0 (20.3-32.1)%/year for blue threshold, and 12.3 (8.7-16.0)%/year for red threshold. The high percentage of eyes with undetectable ERGs at baseline limited assessment of change.

Conclusions

Best-corrected visual acuity was not a sensitive measure of progression over 4 years. Full-field stimulus threshold was a more sensitive measure; however, additional information on the clinical relevance of changes in FST is needed before this test can be adopted as an endpoint for clinical trials.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

[N-Acetylcysteine (NAC) for Retinitis pigmentosa]

Retinitis pigmentosa (RP) is a genetically mediated degenerative retinal disease that leads to progressive photoreceptor degeneration and, ultimately, blindness. Oxidative stress plays a central role in the pathogenesis of RP. This study examines the effect of N-acetylcysteine (NAC), an antioxidant and glutathione precursor, on the disease progression in RP patients. NAC can reduce oxidative stress in the retina and has shown potential neuroprotective effects in preclinical models. Initial clinical studies indicate improvements in visual acuity and macular function with NAC therapy, though no structural changes have yet been demonstrated. The ongoing multicentre Phase III trial "NAC Attack" aims to evaluate the long-term efficacy and safety of NAC in RP.

Genetic Landscape of Nonsyndromic Retinitis Pigmentosa in Portugal

Inherited retinal degenerations (IRDs) comprise a heterogeneous group of disorders that cause severe vision loss or even blindness. With an estimated prevalence of 1:4000, Retinitis Pigmentosa (RP) is the most prevalent IRD. RP is characterized by progressive centripetal degeneration of rods, followed by degeneration of cone photoreceptors. Clinically, RP presents with nyctalopia of variable age of onset and progressive narrowing of the peripheral visual field. Most patients eventually experience some degree of central vision loss, leading to legal blindness. We have evaluated the most common RP-causing genes in a Portuguese IRD registry (IRD-PT, www.retina.com.pt ).

Expanding the Mutation Spectrum for Inherited Retinal Diseases

BACKGROUND/OBJECTIVES

Inherited retinal diseases (IRDs) represent a diverse group of genetic disorders characterized by degeneration of the retina, leading to visual impairment and blindness. IRDs are heterogeneous, sharing common clinical features that can be difficult to diagnose without knowing the genetic basis of the disease. To improve diagnostic accuracy and advance understanding of disease mechanisms, genetic testing was performed for 103 unrelated patients with an IRD at a single clinical site between 30 August 2022 and 5 February 2024.

METHODS

Informed consent was obtained before buccal samples were collected for panel-based sequencing at BluePrint Genetics (BpG), sponsored by the Foundation Fighting Blindness MyRetina Tracker program. A retina specialist performed standard visit assessments, including visual acuity (Snellen chart), slit lamp examination, fundus photography (Optos®, Dunfermline, UK), and spectral-domain optical coherence tomography (SD-OCT; Zeiss).

RESULTS

From 103 patients, genetic findings were reported for 70 individuals. Among these included 20 novel variants.

CONCLUSIONS

These results clarify and confirm clinical diagnoses, aid in counseling patients on prognosis and family planning, and guide treatment options. This study not only holds promise for affected individuals but also expands the mutation spectrum to guide understanding of IRD.

Syndromic Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a progressive inherited retinal dystrophy, characterized by the degeneration of photoreceptors, presenting as a rod-cone dystrophy. Approximately 20-30% of patients with RP also exhibit extra-ocular manifestations in the context of a syndrome. This manuscript discusses the broad spectrum of syndromes associated with RP, pathogenic mechanisms, clinical manifestations, differential diagnoses, clinical management approaches, and future perspectives. Given the diverse clinical and genetic landscape of syndromic RP, the diagnosis may be challenging. However, an accurate and timely diagnosis is essential for optimal clinical management, prognostication, and potential treatment. Broadly, the syndromes associated with RP can be categorized into ciliopathies, inherited metabolic disorders, mitochondrial disorders, and miscellaneous syndromes. Among the ciliopathies associated with RP, Usher syndrome and Bardet-Biedl syndrome are the most well-known. Less common ciliopathies include Cohen syndrome, Joubert syndrome, cranioectodermal dysplasia, asphyxiating thoracic dystrophy, Mainzer-Saldino syndrome, and RHYNS syndrome. Several inherited metabolic disorders can present with RP including Zellweger spectrum disorders, adult Refsum disease, α-methylacyl-CoA racemase deficiency, certain mucopolysaccharidoses, ataxia with vitamin E deficiency, abetalipoproteinemia, several neuronal ceroid lipofuscinoses, mevalonic aciduria, PKAN/HARP syndrome, PHARC syndrome, and methylmalonic acidaemia with homocystinuria type cobalamin (cbl) C disease. Due to the mitochondria's essential role in supplying continuous energy to the retina, disruption of mitochondrial function can lead to RP, as seen in Kearns-Sayre syndrome, NARP syndrome, primary coenzyme Q10 deficiency, SSBP1-associated disease, and long chain 3-hydroxyacyl-CoA dehydrogenase deficiency. Lastly, Cockayne syndrome and PERCHING syndrome can present with RP, but they do not fit the abovementioned hierarchy and are thus categorized as 'Miscellaneous'. Several first-in-human clinical trials are underway or in preparation for some of these syndromic forms of RP.

A Comparative Evaluation of the Genetic Variant Spectrum in the USH2A Gene in Russian Patients with Isolated and Syndromic Forms of Retinitis Pigmentosa

Pathogenic variants in the USH2A gene are the primary cause of both non-syndromic autosomal recessive inherited retinitis pigmentosa (RP) and the syndromic form, characterized by retinal degeneration and sensorineural hearing loss. This study presents a comparative assessment of the genetic variant spectrum in the USH2A gene among Russian patients in two clinical groups. A retrospective analysis was conducted on massive parallel panel sequencing data from 2415 blood samples of unrelated patients suspected of having hereditary retinal diseases. The copy number of USH2A exons was determined using the quantitative MLPA method with the MRC-Holland SALSA MLPA kit. Biallelic pathogenic and likely pathogenic variants in the USH2A gene were identified in 69 patients (8.7%). In the group of patients with isolated hereditary RP (55 patients), the most frequent pathogenic variants were p.(Glu4445_Ser4449delinsAspLeu) (20.9%), p.(Trp3955*) (15.5%), and p.(Cys934Trp) (5.5%). In patients with the syndromic form (14 patients), the most frequent variants were p.(Trp3955*) (35.7%) and c.8682-9A>G (17.9%). It was found that patients with isolated vision impairment rarely had two "null" variants (17.8%), whereas this was common among patients with both hearing and vision impairment (71.4%) (p ≤ 0.05), explaining the severity of the disease and the earlier onset of clinical symptoms in the syndromic form of RP. Ten previously undescribed loss-of-function variants were identified. The estimated prevalence of USH2A-associated retinal dystrophy in Russia was 1.9 per 100,000 individuals. The obtained data on the differences in the spectra of genetic variants in the USH2A gene in the two studied groups highlight the importance of establishing genotype-phenotype correlations and predicting disease severity, aiming at potential early cochlear implantation and selection of target therapy.

Endpoints and Design for Clinical Trials in USH2A-Related Retinal Degeneration: Results and Recommendations From the RUSH2A Natural History Study

Purpose

To evaluate functional and structural assessments as endpoints for clinical trials for USH2A-related retinal degeneration.

Methods

People with biallelic disease-causing variants in USH2A, visual acuity ≥ 20/80, and visual field ≥ 10° diameter were enrolled in a 4-year, natural history study. Participants underwent static perimetry, microperimetry, visual acuity, fullfield stimulus testing (FST), and optical coherence tomography annually. Rates of change estimated from mixed-effects linear models and percentages of eyes with changes exceeding the coefficient of repeatability (CoR) or thresholds conforming with U.S. Food and Drug Administration (FDA) guidelines were evaluated.

Results

Rates of change were generally more sensitive to change than proportions of eyes exceeding a threshold such as the CoR. Baseline ellipsoid zone area ≥ 3 mm2 was necessary to detect change. Mean sensitivity and volumetric hill of vision measures on static perimetry had similar properties and were the most sensitive to changes of the continuous measures. The highest 4-year proportions of eyes exceeding the CoR were from FST testing (47%) and microperimetry (32%). Specification of loci as functional transition points (FTPs) resulted in 45% (static perimetry) and 46% (microperimetry) at 4 years, meeting FDA guidelines for progression.

Conclusions

Rate of change of mean sensitivity on static perimetry was a sensitive perimetric continuous measure. Percentages of within-eye change were largest with FST testing and microperimetry. FTPs appear to be particularly sensitive to change. These results affect clinical trial design for USH2A-related retinal degeneration.

Translational Relevance

Analyses of natural history data from the Rate of Progression in USH2A-Related Retinal Degeneration (RUSH2A) study can inform eligibility criteria and endpoints for clinical trials.

Genotype Characterization and MiRNA Expression Profiling in Usher Syndrome Cell Lines

Usher syndrome (USH) is an inherited disorder characterized by sensorineural hearing loss (SNHL), retinitis pigmentosa (RP)-related vision loss, and vestibular dysfunction. USH presents itself as three distinct clinical types, 1, 2, and 3, with no biomarker for early detection. This study aimed to explore whether microRNA (miRNA) expression in USH cell lines is dysregulated compared to the miRNA expression pattern in a cell line derived from a healthy human subject. Lymphocytes from USH patients and healthy individuals were isolated and transformed into stable cell lines using Epstein-Barr virus (EBV). DNA from these cell lines was sequenced using a targeted panel to identify gene variants associated with USH types 1, 2, and 3. Microarray analysis was performed on RNA from both USH and control cell lines using NanoString miRNA microarray technology. Dysregulated miRNAs identified by the microarray were validated using droplet digital PCR technology. DNA sequencing revealed that two USH patients had USH type 1 with gene variants in USH1B (MYO7A) and USH1D (CDH23), while the other two patients were classified as USH type 2 (USH2A) and USH type 3 (CLRN-1), respectively. The NanoString miRNA microarray detected 92 differentially expressed miRNAs in USH cell lines compared to controls. Significantly altered miRNAs exhibited at least a twofold increase or decrease with a p value below 0.05. Among these miRNAs, 20 were specific to USH1, 14 to USH2, and 5 to USH3. Three miRNAs that are known as miRNA-183 family which are crucial for inner ear and retina development, have been significantly downregulated as compared to control cells. Subsequently, droplet digital PCR assays confirmed the dysregulation of the 12 most prominent miRNAs in USH cell lines. This study identifies several miRNA signatures in USH cell lines which may have potential utility in Usher syndrome identification.

Ocular genetics in the Japanese population

In today's globalized society, ophthalmologists can examine people of different ethnicities regardless of where they live. The frequency of disease-causing genes varies according to a patient's ethnic background. We explain genetic findings for Japanese patients with inherited eye diseases. Ocular genetics has made great advances over the past 30 years. For example, detecting mutations at nucleotide position 11778 in mitochondrial DNA was useful in the genetic diagnosis of Leber's hereditary optic neuropathy (LHON). I evaluated the genotype-phenotype relationship in cases of corneal dystrophy and inherited retinal dystrophy (IRD). I identified the entire exon sequence of the eyes shut homolog (EYS) gene in patients with autosomal recessive retinitis pigmentosa (RP). EYS gene mutations are the most frequent cause of autosomal recessive RP. RPGRIP1 may be a common causative gene with early-onset severe retinal dystrophy, including Leber congenital amaurosis. However, some genes have complex structures that are difficult to analyze, including the OPN1LW/OPN1MW gene cluster in blue cone monochromacy and the IKBKG/NEMO genes in incontinentia pigmenti. This review will also present two cases with uniparental disomy, a case of IRD with double mutations, and a case with RP complicated with LHON-like neuropathy. Precise understanding of the effects of genetic variants may reveal differences in the clinical characteristics of patients with the same variant. When starting genome medicine, accurately diagnosing the patient, making accurate prediction, determining the genetic pattern, and providing genetic counseling are important. Above all, that both the doctors and patients understand genetic diseases correctly is important.

Clinical characterizations and molecular genetic study of two co-segregating variants in PDZD7 and PDE6C genes leading simultaneously to non-syndromic hearing loss and achromatopsia

BACKGROUND

Autosomal recessive non-syndromic hearing loss (NSHL) and cone dystrophies (CODs) are highly genetically and phenotypically heterogeneous disorders. In this study, we applied the whole exome sequencing (WES) to find the cause of HL and COD in an Iranian consanguineous family with three affected individuals.

METHODS

Three members from an Iranian consanguineous family who were suffering from NSHL and visual impairment were ascertained in this study. Comprehensive clinical evaluations and genetic analysis followed by bioinformatic and co-segregation studies were performed to diagnose the cause of these phenotypes. Data were collected from 2020 to 2022.

RESULTS

All cases showed congenital bilateral NSHL, decreased visual acuity, poor color discrimination, photophobia and macular atrophy. Moreover, cornea, iris and anterior vitreous were within normal limit in both eyes, decreased foveal sensitivity, central scotoma and generalized depression of visual field were seen in three cases. WES results showed two variants, a novel null variant (p.Trp548Ter) in the PDE6C gene causing COD type 4 (Achromatopsia) and a previously reported variant (p.Ile84Thr) in the PDZD7 gene causing NSHL. Both variants were found in the cis configuration on chromosome 10 with a genetic distance of about 8.3 cM, leading to their co-inheritance. However, two diseases could appear independently in subsequent generations due to crossover during meiosis.

CONCLUSIONS

Here, we could successfully determine the etiology of a seemingly complex phenotype in two adjacent genes. We identified a novel variant in the PDE6C gene, related to achromatopsia. Interestingly, this variant could cooperatively cause visual disorders: cone dystrophy and cone-rod dystrophy.

Functional Vision in Patients With Biallelic USH2A Variants

PURPOSE

To describe functional vision (FV) and investigate the relationship between FV, visual acuity (VA), and hill of vision (VTOT) at baseline in patients with biallelic USH2A variants.

DESIGN

Multicenter, international, cross-sectional study.

METHODS

In individuals with biallelic disease-causing variants in USH2A, clinical diagnosis of Usher syndrome type 2 (USH2) or autosomal recessive nonsyndromic retinitis pigmentosa (ARRP) was based on history of hearing loss and audiology examinations. The VALVVFQ-48 was administered verbally to participants ≥18 years old. VA was measured in both eyes; VTOT was determined from static perimetry in the study eye (better VA). FV scores were calculated using Rasch analysis.

RESULTS

Median age of 121 participants (76 with USH2, 45 with ARRP) was 41 years (range: 19-80); 54% were female. FV scores varied from -2.0 to 7.6 logits (median [interquartile range (IQR)]: 2.8 [1.5-3.8]). ARRP and USH2 participants had similar FV scores, both before [mean (95% CI): 2.8 (2.3-3.4) and 2.7 (2.3-3.2), respectively], and after [mean (95% CI): 2.5 (2.1-3.0) and 2.9 (2.6-3.3), respectively; P = .24] adjusting for age, VA, disease duration, and VTOT. VA and VTOT accounted for 29% and 26% of the variance in FV scores, respectively (P < .001 for each). Together, they accounted for 36% of variance observed.

CONCLUSIONS

Biallelic USH2A variants were associated with a large range of FV, yet similar in ARRP and USH2, despite hearing loss in USH2. The modified VALVVFQ-48 we evaluated is not ideal for detecting the impact of USH2A-associated retinal degenerations on activities of daily living.

Spectrum of variants associated with inherited retinal dystrophies in Northeast Mexico

BACKGROUND

Inherited retinal dystrophies are hereditary diseases which have in common the progressive degeneration of photoreceptors. They are a group of diseases with clinical, genetic, and allelic heterogeneity. There is limited information regarding the genetic landscape of inherited retinal diseases in Mexico, therefore, the present study was conducted in the northeast region of the country.

METHODS

Patients with inherited retinal dystrophies were included. A complete history, full ophthalmological and medical genetics evaluations, and genetic analysis through a targeted NGS panel for inherited retinal dystrophies comprising at least 293 genes were undertaken.

RESULTS

A total of 126 patients were included. Cases were solved in 74.6% of the study's population. Retinitis pigmentosa accounted for the most found inherited retinal disease. Ninety-nine causal variants were found, being USH2A and ABCA4 the most affected genes (26 and 15 cases, respectively).

CONCLUSIONS

The present study documents the most prevalent causative genes in IRDs, as USH2A, in northeastern Mexico. This contrasts with previous reports of IRDs in other zones of the country. Further studies, targeting previously unstudied populations in Mexico are important to document the genetic background of inherited retinal dystrophies in the country.

The effects of ush2a gene knockout on vesicle transport in photoreceptors

USH2A (Usher syndrome type 2A) gene mutations are the predominant cause of Usher syndrome type 2, characterized by sensorineural hearing loss and retinitis pigmentosa (RP), and also significant contributors to non-syndromic RP. To date, there is a lack of definitive therapeutic interventions to mitigate the associated disorders caused by USH2A mutations, and the precise pathogenic mechanisms underlying their onset remain unclear. In the present study, we utilized the ush2a knockout zebrafish model to investigate the pathological mechanisms of RP. In late-stage ush2a-/- zebrafish, the outer segments of rods displayed shortened length and decreased number. Anomalous vesicle accumulation was observed at the junction between the inner and outer segments, accompanied by reduced expression and structural damage of actin filaments in the photoreceptor cells. Furthermore, we discovered that Rab8 expression was downregulated and exhibited aberrant localization in ush2a-/- zebrafish. Additionally, we identified an interaction between USH2A and Rab8. Therefore, the knockout of ush2a may potentially affect vesicle transport through the regulation of Rab8, providing a novel target for maintaining the survival of photoreceptor cells. These findings also contribute to our understanding of the potential molecular pathogenesis underlying RP caused by USH2A gene mutations.

Detailed Clinical, Ophthalmic, and Genetic Characterization of ADGRV1-Associated Usher Syndrome

PURPOSE

To present the clinical characteristics, retinal features, natural history, and genetics of ADGRV1-Usher syndrome (USH).

DESIGN

Multicenter international retrospective cohort study.

METHODS

Clinical notes, hearing loss history, multimodal retinal imaging, and molecular diagnosis were reviewed. Thirty patients (28 families) with USH type 2 and disease-causing variants in ADGRV1 were identified. Visual function, retinal imaging, and genetics were evaluated and correlated, with retinal features also compared with those of the commonest cause of USH type 2, USH2A-USH.

RESULTS

The mean age at the first visit was 38.6 ± 12.0 years (range: 19-74 years), and the mean follow-up time was 9.0 ± 7.7 years. Hearing loss was reported in the first decade of life by all patients, 3 (10%) described progressive loss, and 93% had moderate-severe impairment. Visual symptom onset was at 17.0 ± 7.7 years of age (range: 6-32 years), with 13 patients noticing problems before the age of 16. At baseline, 90% of patients had no or mild visual impairment. The most frequent retinal features were a hyperautofluorescent ring at the posterior pole (70%), perimacular patches of decreased autofluorescence (59%), and mild-moderate peripheral bone-spicule-like deposits (63%). Twenty-six (53%) variants were previously unreported, 19 families (68%) had double-null genotypes, and 9 were not-double-null. Longitudinal analysis showed significant differences between baseline and follow-up central macular thickness (-1.25 µm/y), outer nuclear layer thickness (-1.19 µm/y), and ellipsoid zone width (-40.9 µm/y). The rate of visual acuity decline was 0.02 LogMAR (1 letter)/y, and the rate of constriction of the hyperautofluorescent ring was 0.23 mm2/y.

CONCLUSIONS

ADGRV1-USH is characterized by early-onset, usually non-progressive, mild-to-severe hearing loss and generally good central vision until late adulthood. Perimacular atrophic patches and relatively retained ellipsoid zone and central macular thickness in later adulthood are more often seen in ADGRV1-USH than in USH2A-USH.

Successful large gene augmentation of USH2A with non-viral episomal vectors

USH2A mutations are a common cause of autosomal recessive retinitis pigmentosa (RP) and Usher syndrome, for which there are currently no approved treatments. Gene augmentation is a valuable therapeutic strategy for treating many inherited retinal diseases; however, conventional adeno-associated virus (AAV) gene therapy cannot accommodate cDNAs exceeding 4.7 kb, such as the 15.6-kb-long USH2A coding sequence. In the present study, we adopted an alternative strategy to successfully generate scaffold/matrix attachment region (S/MAR) DNA plasmid vectors containing the full-length human USH2A coding sequence, a GFP reporter gene, and a ubiquitous promoter (CMV or CAG), reaching a size of approximately 23 kb. We assessed the vectors in transfected HEK293 cells and USH2A patient-derived dermal fibroblasts in addition to ush2au507 zebrafish microinjected with the vector at the one-cell stage. pS/MAR-USH2A vectors drove persistent transgene expression in patient fibroblasts with restoration of usherin. Twelve months of GFP expression was detected in the photoreceptor cells, with rescue of Usher 2 complex localization in the photoreceptors of ush2au507 zebrafish retinas injected with pS/MAR-USH2A. To our knowledge, this is the first reported vector that can be used to express full-length usherin with functional rescue. S/MAR DNA vectors have shown promise as a novel non-viral retinal gene therapy, warranting further translational development.

Change in Cone Structure Over 24 Months in USH2A-Related Retinal Degeneration

PURPOSE

To describe cone structure changes using adaptive optics scanning laser ophthalmoscopy (AOSLO) in the Rate of Progression of USH2A-related Retinal Degeneration (RUSH2A) study.

DESIGN

Multicenter, longitudinal natural history study.

METHODS

AOSLO images were acquired at 4 centers, twice at baseline and annually for 24 months in this natural history study. For each eye, at least 10 regions of interest (ROIs) with ≥50 contiguous cones were analyzed by masked, independent graders. Cone spacing Z-scores, standard deviations from the normal mean at the measured location, were compared between graders and tests at baseline. The association of cone spacing with clinical characteristics was assessed using linear mixed effects regression models weighted by image quality score. Annual rates of change were calculated based on differences between visits.

RESULTS

Fourteen eyes of 14 participants were imaged, with 192 ROIs selected at baseline. There was variability among graders, which was greater in images with lower image quality score (P < .001). Cone spacing was significantly correlated with eccentricity, quality score, and disease duration (P < .02). On average, the cone spacing Z-score increased 0.14 annually (about 9%, P < .001). We observed no significant differences in rate of change between disease type (Usher syndrome or retinitis pigmentosa), imaging site, or grader.

CONCLUSIONS

Using current methods, the analysis of quantitative measures of cone structure showed some challenges, yet showed promise that AOSLO images can be used to characterize progressive change over 24 months. Additional multicenter studies using AOSLO are needed to advance cone mosaic metrics as sensitive outcome measures for clinical trials. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

A protein domain-oriented approach to expand the opportunities of therapeutic exon skipping for USH2A-associated retinitis pigmentosa

Loss-of-function mutations in USH2A are among the most common causes of syndromic and non-syndromic retinitis pigmentosa (RP). We previously presented skipping of USH2A exon 13 as a promising treatment paradigm for USH2A-associated RP. However, RP-associated mutations are often private, and evenly distributed along the USH2A gene. In order to broaden the group of patients that could benefit from therapeutic exon skipping strategies, we expanded our approach to other USH2A exons in which unique loss-of-function mutations have been reported by implementing a protein domain-oriented dual exon skipping strategy. We first generated zebrafish mutants carrying a genomic deletion of the orthologous exons of the frequently mutated human USH2A exons 30-31 or 39-40 using CRISPR-Cas9. Excision of these in-frame combinations of exons restored usherin expression in the zebrafish retina and rescued the photopigment mislocalization typically observed in ush2a mutants. To translate these findings into a future treatment in humans, we employed in vitro assays to identify and validate antisense oligonucleotides (ASOs) with a high potency for sequence-specific dual exon skipping. Together, the in vitro and in vivo data demonstrate protein domain-oriented ASO-induced dual exon skipping to be a highly promising treatment option for RP caused by mutations in USH2A.

Nationwide genetic analysis of more than 600 families with inherited eye diseases in Argentina

This study corresponds to the first large-scale genetic analysis of inherited eye diseases (IED) in Argentina and describes the comprehensive genetic profile of a large cohort of patients. Medical records of 22 ophthalmology and genetics services throughout 13 Argentinian provinces were analyzed retrospectively. Patients with a clinical diagnosis of an ophthalmic genetic disease and a history of genetic testing were included. Medical, ophthalmological and family history was collected. A total of 773 patients from 637 families were included, with 98% having inherited retinal disease. The most common phenotype was retinitis pigmentosa (RP, 62%). Causative variants were detected in 379 (59%) patients. USH2A, RPGR, and ABCA4 were the most common disease-associated genes. USH2A was the most frequent gene associated with RP, RDH12 early-onset severe retinal dystrophy, ABCA4 Stargardt disease, PROM1 cone-rod dystrophy, and BEST1 macular dystrophy. The most frequent variants were RPGR c.1345 C > T, p.(Arg449*) and USH2A c.15089 C > A, p.(Ser5030*). The study revealed 156/448 (35%) previously unreported pathogenic/likely pathogenic variants and 8 possible founder mutations. We present the genetic landscape of IED in Argentina and the largest cohort in South America. This data will serve as a reference for future genetic studies, aid diagnosis, inform counseling, and assist in addressing the largely unmet need for clinical trials to be conducted in the region.

USH2A mutational spectrum causing syndromic and non-syndromic retinal dystrophies in a large cohort of Mexican patients

Background

Mutations in the USH2A gene are the leading cause of both non-syndromic autosomal recessive retinitis pigmentosa (RP) and Usher syndrome, a syndromic form of RP characterized by retinal dystrophy and sensorineural hearing loss. To contribute to the expansion of the USH2A-related molecular spectrum, the results of genetic screening in a large cohort of Mexican patients are presented.

Methods

The study population comprised 61 patients with a clinical diagnosis of either non-syndromic RP (n = 30) or Usher syndrome type 2 (USH2; n = 31) who were demonstrated to carry biallelic pathogenic variants in USH2A in a three-year period. Genetic screening was performed either by gene panel sequencing or by exome sequencing. A total of 72 available first- or second-degree relatives were also genotyped for familial segregation of the identified variants.

Results

The USH2A mutational spectrum in RP patients included 39 distinct pathogenic variants, most of them of the missense type. The most common RP-causing variants were p.Cys759Phe (c.2276G>T), p.Glu767Serfs*21 (c.2299delG), and p.Cys319Tyr (c.956G>A), which together accounted for 25% of all RP variants. Novel USH2A mutations included three nonsense, two missense, two frameshift, and one intragenic deletion. The USH2A mutational spectrum in USH2 patients included 26 distinct pathogenic variants, most of them of the nonsense and frameshift types. The most common Usher syndrome-causing variants were p.Glu767Serfs*21 (c.2299delG), p.Arg334Trp (c.1000C>T), and c.12067-2A>G), which together accounted for 42% of all USH2-related variants. Novel Usher syndrome USH2A mutations included six nonsense, four frameshift, and two missense mutations. The c.2299delG mutation was associated with a common haplotype for SNPs located in exons 2-21 of USH2A, indicating a founder mutation effect.

Conclusions

Our work expands the USH2A mutational profile by identifying 20 novel pathogenic variants causing syndromic and non-syndromic retinal dystrophy. The prevalent c.2299delG allele is shown to arise from a founder effect. Our results emphasize the usefulness of molecular screening in underrepresented populations for a better characterization of the molecular spectrum of common monogenic diseases.

Rare variant analyses across multiethnic cohorts identify novel genes for refractive error

Refractive error, measured here as mean spherical equivalent (SER), is a complex eye condition caused by both genetic and environmental factors. Individuals with strong positive or negative values of SER require spectacles or other approaches for vision correction. Common genetic risk factors have been identified by genome-wide association studies (GWAS), but a great part of the refractive error heritability is still missing. Some of this heritability may be explained by rare variants (minor allele frequency [MAF] ≤ 0.01.). We performed multiple gene-based association tests of mean Spherical Equivalent with rare variants in exome array data from the Consortium for Refractive Error and Myopia (CREAM). The dataset consisted of over 27,000 total subjects from five cohorts of Indo-European and Eastern Asian ethnicity. We identified 129 unique genes associated with refractive error, many of which were replicated in multiple cohorts. Our best novel candidates included the retina expressed PDCD6IP, the circadian rhythm gene PER3, and P4HTM, which affects eye morphology. Future work will include functional studies and validation. Identification of genes contributing to refractive error and future understanding of their function may lead to better treatment and prevention of refractive errors, which themselves are important risk factors for various blinding conditions.

Alternative splicing in shaping the molecular landscape of the cochlea

The cochlea is a complex organ comprising diverse cell types with highly specialized morphology and function. Until now, the molecular underpinnings of its specializations have mostly been studied from a transcriptional perspective, but accumulating evidence points to post-transcriptional regulation as a major source of molecular diversity. Alternative splicing is one of the most prevalent and well-characterized post-transcriptional regulatory mechanisms. Many molecules important for hearing, such as cadherin 23 or harmonin, undergo alternative splicing to produce functionally distinct isoforms. Some isoforms are expressed specifically in the cochlea, while some show differential expression across the various cochlear cell types and anatomical regions. Clinical phenotypes that arise from mutations affecting specific splice variants testify to the functional relevance of these isoforms. All these clues point to an essential role for alternative splicing in shaping the unique molecular landscape of the cochlea. Although the regulatory mechanisms controlling alternative splicing in the cochlea are poorly characterized, there are animal models with defective splicing regulators that demonstrate the importance of RNA-binding proteins in maintaining cochlear function and cell survival. Recent technological breakthroughs offer exciting prospects for overcoming some of the long-standing hurdles that have complicated the analysis of alternative splicing in the cochlea. Efforts toward this end will help clarify how the remarkable diversity of the cochlear transcriptome is both established and maintained.

Novel compound heterozygous variants in the USH2A gene associated with autosomal recessive retinitis pigmentosa without hearing loss

Background: Retinitis pigmentosa (RP) is a group of progressive inherited retinal dystrophies characterized by the primary degeneration of rod photoreceptors and the subsequent loss of cone photoreceptors because of cell death. It is caused by different mechanisms, including inflammation, apoptosis, necroptosis, pyroptosis, and autophagy. Variants in the usherin gene (USH2A) have been reported in autosomal recessive RP with or without hearing loss. In the present study, we aimed to identify causative variants in a Han-Chinese pedigree with autosomal recessive RP. Methods: A six-member, three-generation Han-Chinese family with autosomal recessive RP was recruited. A full clinical examination, whole exome sequencing, and Sanger sequencing, as well as co-segregation analysis were performed. Results: Three heterozygous variants in the USH2A gene, c.3304C>T (p.Q1102*), c.4745T>C (p.L1582P), and c.14740G>A (p.E4914K), were identified in the proband, which were inherited from parents and transmitted to the daughters. Bioinformatics analysis supported the pathogenicity of the c.3304C>T (p.Q1102*) and c.4745T>C (p.L1582P) variants. Conclusions: Novel compound heterozygous variants in the USH2A gene, c.3304C>T (p.Q1102*) and c.4745T>C (p.L1582P), were identified as the genetic causes of autosomal recessive RP. The findings may enhance the current knowledge of the pathogenesis of USH2A-associated phenotypes, expand the spectrum of the USH2A gene variants, and contribute to improved genetic counseling, prenatal diagnosis, and disease management.

Genetic Diagnosis for 64 Patients with Inherited Retinal Disease

The overlapping genetic and clinical spectrum in inherited retinal degeneration (IRD) creates challenges for accurate diagnoses. The goal of this work was to determine the genetic diagnosis and clinical features for patients diagnosed with an IRD. After signing informed consent, peripheral blood or saliva was collected from 64 patients diagnosed with an IRD. Genetic testing was performed on each patient in a Clinical Laboratory Improvement Amendments of 1988 (CLIA) certified laboratory. Mutations were verified with Sanger sequencing and segregation analysis when possible. Visual acuity was measured with a traditional Snellen chart and converted to a logarithm of minimal angle of resolution (logMAR). Fundus images of dilated eyes were acquired with the Optos® camera (Dunfermline, UK). Horizontal line scans were obtained with spectral-domain optical coherence tomography (SDOCT; Spectralis, Heidelberg, Germany). Genetic testing combined with segregation analysis resolved molecular and clinical diagnoses for 75% of patients. Ten novel mutations were found and unique genotype phenotype associations were made for the genes RP2 and CEP83. Collective knowledge is thereby expanded of the genetic basis and phenotypic correlation in IRD.

Baseline Microperimetry and OCT in the RUSH2A Study: Structure-Function Association and Correlation With Disease Severity

PURPOSE

To investigate baseline mesopic microperimetry (MP) and spectral domain optical coherence tomography (OCT) in the Rate of Progression in USH2A-related Retinal Degeneration (RUSH2A) study.

DESIGN

Natural history study METHODS: Setting: 16 clinical sites in Europe and North AmericaStudy Population: Participants with Usher syndrome type 2 (USH2) (N = 80) or autosomal recessive nonsyndromic RP (ARRP) (N = 47) associated with biallelic disease-causing sequence variants in USH2AObservation Procedures: General linear models were used to assess characteristics including disease duration, MP mean sensitivity and OCT intact ellipsoid zone (EZ) area. The associations between mean sensitivity and EZ area with other measures, including best corrected visual acuity (BCVA) and central subfield thickness (CST) within the central 1 mm, were assessed using Spearman correlation coefficients.

MAIN OUTCOME MEASURES

Mean sensitivity on MP; EZ area and CST on OCT.

RESULTS

All participants (N = 127) had OCT, while MP was obtained at selected sites (N = 93). Participants with Usher syndrome type 2 (USH2, N = 80) and nonsyndromic autosomal recessive Retinitis Pigmentosa (ARRP, N = 47) had the following similar measurements: EZ area (median (interquartile range [IQR]): 1.4 (0.4, 3.1) mm2 vs 2.3 (0.7, 5.7) mm2) and CST (median (IQR): 247 (223, 280) µm vs 261 (246, 288), and mean sensitivity (median (IQR): 3.5 (2.1, 8.4) dB vs 5.1 (2.9, 9.0) dB). Longer disease duration was associated with smaller EZ area (P < 0.001) and lower mean sensitivity (P = 0.01). Better BCVA, larger EZ area, and larger CST were correlated with greater mean sensitivity (r > 0.3 and P < 0.01). Better BCVA and larger CST were associated with larger EZ area (r > 0.6 and P < 0.001).

CONCLUSIONS

Longer disease duration correlated with more severe retinal structure and function abnormalities, and there were associations between MP and OCT metrics. Monitoring changes in retinal structure-function relationships during disease progression will provide important insights into disease mechanism in USH2A-related retinal degeneration.

Novel mutations of the USH2A gene cause Usher syndrome in five Chinese families

Background

Usher syndrome (USH) is a leading disorder of deaf–blindness. The phenotypic and genetic heterogeneity of USH makes the diagnosis of this disorder difficult. However, diagnosis can be facilitated by employing molecular approaches, especially for diseases without pronounced pathognomonic symptoms. Therefore, this study aimed to reveal the genetic defects in five USH patients using clinical targeted exome sequencing (TES).

Methods

USH patients and their family members from five unrelated Chinese USH families were recruited and subjected to TES. Ophthalmic information was obtained for all patients to ensure a meaningful interpretation. The TES data were analysed using an established bioinformatics pipeline to identify causative mutations. Further verification by Sanger sequencing and cosegregation analysis were performed on available family members.

Results

We identified genetic mutations in five USH patients using TES. Seven mutations, four of which were novel, were identified in the USH2A gene. One proband (F1-II-3) was found to have a homozygous mutation inherited from nonconsanguineous parents, and another proband (F5-III-1) was found to carry three USH2A gene mutations.

Conclusion

In conclusion, the study revealed the importance of TES in the clinical diagnosis of USH patients with variable phenotypes. The correlation between USH2A gene mutations and clinical phenotypes will help to refine the clinical diagnosis of USH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02532-6.

Exome Sequencing Identified Molecular Determinants of Retinal Dystrophies in Nine Consanguineous Pakistani Families

Inherited retinal dystrophies (IRDs) are a heterogeneous group of degenerative disorders of the retina. Retinitis Pigmentosa (RP) is a common type of IRD that causes night blindness and loss of peripheral vision and may progress to blindness. Mutations in more than 300 genes have been associated with syndromic and non-syndromic IRDs. Recessive forms are more frequent in populations where endogamy is a social preference, such as Pakistan. The aim of this study was to identify molecular determinants of IRDs with the common presentation of night blindness in consanguineous Pakistani families. This study included nine consanguineous IRD-affected families that presented autosomal recessive inheritance of the night blindness phenotype. DNA was extracted from blood samples. Targeted exome sequencing of 344 known genes for retinal dystrophies was performed. Screening of nine affected families revealed two novel (c.5571_5576delinsCTAGATand c.471dup in EYS and SPATA7 genes, respectively) and six reported pathogenic mutations (c.304C>A, c.187C>T, c.1560C>A, c.547C>T, c.109del and c.9911_11550del in PDE6A, USH2A, USH2A, NMNAT1, PAX6 and ALMS1 genes, respectively) segregating with disease phenotype in each respective family. Molecular determinants of hereditary retinal dystrophies were identified in all screened families. Identification of novel variants aid future diagnosis of retinal dystrophies and help to provide genetic counseling to affected families.

Genetic Characteristics and Variation Spectrum of USH2A-Related Retinitis Pigmentosa and Usher Syndrome

Purposes: We aimed to characterize the USH2A genotypic spectrum in a Chinese cohort and provide a detailed genetic profile for Chinese patients with USH2A-IRD.

Methods: We designed a retrospective study wherein a total of 1,334 patients diagnosed with IRD were included as a study cohort, namely 1,278 RP and 56 USH patients, as well as other types of IEDs patients and healthy family members as a control cohort. The genotype-phenotype correlation of all participants with USH2A variant was evaluated.

Results: Etiological mutations in USH2A, the most common cause of RP and USH, were found in 16.34% (n = 218) genetically solved IRD patients, with prevalences of 14.87% (190/1,278) and 50% (28/56). After bioinformatics and QC processing, 768 distinct USH2A variants were detected in all participants, including 136 disease-causing mutations present in 665 alleles, distributed in 5.81% of all participants. Of these 136 mutations, 43 were novel, nine were founder mutations, and two hot spot mutations with allele count ≥10. Furthermore, 38.5% (84/218) of genetically solved USH2A-IRD patients were caused by at least one of both c.2802T&gt;G and c.8559–2 A&gt;G mutations, and 36.9% and 69.6% of the alleles in the RP and USH groups were truncating, respectively.

Conclusion: USH2A-related East Asian-specific founder and hot spot mutations were the major causes for Chinese RP and USH patients. Our study systematically delineated the genotype spectrum of USH2A-IRD, enabled accurate genetic diagnosis, and provided East Asian and other ethnicities with baseline data of a Chinese origin, which would better serve genetic counseling and therapeutic targets selection.

Case report: Disease phenotype associated with simultaneous biallelic mutations in ABCA4 and USH2A due to uniparental disomy of chromosome 1

Inherited retinal diseases (IRDs) represent a spectrum of clinically and genetically heterogeneous disorders. Our study describes an IRD patient carrying ABCA4 and USH2A pathogenic biallelic mutations as a result of paternal uniparental disomy (UPD) in chromosome 1. The proband is a 9-year-old girl born from non-consanguineous parents. Both parents were asymptomatic and denied family history of ocular disease. Clinical history and ophthalmologic examination of the proband were consistent with Stargardt disease. Whispered voice testing disclosed moderate hearing loss. Next-generation sequencing and Sanger sequencing identified pathogenic variants in ABCA4 (c.4926C>G and c.5044_5058del) and USH2A (c.2276G>T). All variants were present homozygously in DNA from the proband and heterozygously in DNA from the father. No variants were found in maternal DNA. Further analysis of single nucleotide polymorphisms confirmed paternal UPD of chromosome 1. This is the first known patient with confirmed UPD for two recessively mutated IRD genes. Our study expands on the genetic heterogeneity of IRDs and highlights the importance of UPD as a mechanism of autosomal recessive disease in non-consanguineous parents. Moreover, a long-term follow-up is essential for the identification of retinal features that may develop as a result of USH2A-related conditions.

Phenotypic and Genetic Characteristics in a Cohort of Patients with Usher Genes

Background: This study aimed to compare phenotype−genotype correlation in patients with Usher syndrome (USH) to those with autosomal recessive retinitis pigmentosa (NS-ARRP) caused by genes associated with Usher syndrome. Methods: Case notes of patients with USH or NS-ARRP and a molecularly confirmed diagnosis in genes associated with Usher syndrome were reviewed. Phenotypic information, including the age of ocular symptoms, hearing impairment, visual acuity, Goldmann visual fields, fundus autofluorescence (FAF) imaging and spectral domain optical coherence tomography (OCT) imaging, was reviewed. The patients were divided into three genotype groups based on variant severity for genotype-phenotype correlations. Results: 39 patients with Usher syndrome and 33 patients with NS-ARRP and a molecular diagnosis in an Usher syndrome-related gene were identified. In the 39 patients diagnosed with Usher syndrome, a molecular diagnosis was confirmed as follows: USH2A (28), MYO7A (4), CDH23 (2), USH1C (2), GPR98/VLGR1 (2) and PCDH15 (1). All 33 patients with NS-ARRP had variants in USH2A. Further analysis was performed on the patients with USH2A variants. USH2A patients with syndromic features had an earlier mean age of symptom onset (17.9 vs. 31.7 years, p < 0.001), had more advanced changes on FAF imaging (p = 0.040) and were more likely to have cystoid macular oedema (p = 0.021) when compared to USH2A patients presenting with non-syndromic NS-ARRP. Self-reported late-onset hearing loss was identified in 33.3% of patients with NS-ARRP. Having a syndromic phenotype was associated with more severe USH2A variants (p < 0.001). Eighteen novel variants in genes associated with Usher syndrome were identified in this cohort. Conclusions: Patients with Usher syndrome, whatever the associated gene in this cohort, tended to have an earlier onset of retinal disease (other than GPR98/VLGR1) when compared to patients presenting with NS-ARRP. Analysis of genetic variants in USH2A, the commonest gene in our cohort, showed that patients with a more severe genotype were more likely to be diagnosed with USH compared to NS-ARRP. USH2A patients with syndromic features have an earlier onset of symptoms and more severe features on FAF and OCT imaging. However, a third of patients diagnosed with NS-ARRP developed later onset hearing loss. Eighteen novel variants in genes associated with Usher syndrome were identified in this cohort, thus expanding the genetic spectrum of known pathogenic variants. An accurate molecular diagnosis is important for diagnosis and prognosis and has become particularly relevant with the advent of potential therapies for Usher-related gene

Emerging Gene Manipulation Strategies for the Treatment of Monogenic Eye Disease

Genetic eye diseases, representing a wide spectrum of simple and complex conditions, are one of the leading causes of visual loss in children and working adults, and progress in the field has led to changes in disease investigation, diagnosis, and management. The past 15 years have seen the emergence of novel therapies for these previously untreatable conditions to the extent that we now have a licensed therapy for one form of genetic eye disease and many more in clinical trial. This is a systematic review of published and ongoing clinical trials of gene therapies for monogenic eye diseases. Databases of clinical trials and the published literature were searched for interventional studies of gene therapies for eye diseases. Standard methodological procedures were used to assess the relevance of search results. A total of 59 registered clinical trials are referenced, showing the significant level of interest in the potential for translation of these therapies from bench to bedside. The breadth of therapy design is encouraging, providing multiple possible therapeutic mechanisms. Some fundamental questions regarding gene therapy for genetic eye diseases remain, such as optimal dosing, the relative benefits of adeno-associated virus (AAV)-packaging and the potential for a significant inflammatory response to the therapy itself. As a result, despite the promise of the eye as a target, it has proven difficult to deliver clinically effective gene therapies to the eye. Despite setbacks, the licensing of Luxturna (voretigene neparvovec, Novartis) for the treatment of RPE65-mediated Leber congenital amaurosis (LCA) is a major advance in efforts to treat these rare, but devastating, causes of visual loss.

Panel-based next-generation sequencing identifies novel mutations in Bulgarian patients with inherited retinal dystrophies

BACKGROUND

Next-generation sequencing (NGS)-based method is being used broadly for genetic testing especially for clinically and genetically heterogeneous disorders, such as inherited retinal degenerations (IRDs) but still not routinely used for molecular diagnostics in Bulgaria. Consequently, the purpose of this study was to evaluate the effectiveness of a molecular diagnostic approach, based on targeted NGS for the identification of the disease-causing mutations in 16 Bulgarian patients with different IRDs.

METHODS

We applied a customized NGS panel, including 125 genes associated with retinal and other eye diseases to the patients with hereditary retinopathies.

RESULTS

Systematic filtering approach coupled with copy number variation analysis and segregation study lead to the identification of 16 pathogenic and likely pathogenic variants in 12/16 (75%) of IRD patients, 2 of which novel (12.5%): ABCA4-c.668delA (p.K223Rfs18) and RР1-c.2015dupA (p.K673Efs*25). Mutations in the ABCA4, PRPH2, USH2A, BEST1, RР1, CDHR1, and RHO genes were detected reaching a diagnostic yield between 42.9% for Retinitis pigmentosa cases and 100% for macular degeneration, Usher syndrome, and cone-rod dystrophy patients.

CONCLUSION

Our results confirm the usefulness of targeted NGS approach based on frequently mutated genes as a comprehensive and successful genetic diagnostic tool for IRDs with significant impact on patients counseling.

Early audiological phenotype in patients with mutations in the USH2A gene

INTRODUCTION

Nowadays, due to universal newborn hearing screening (UNHS) the number of children with mild-to-moderate hearing loss diagnosed in the first year of life has increased significantly. Aside from that, identification of the genetic cause improves the genetic counselling of the families and allows to reveal possible comorbidities which may need a special approach.

OBJECTIVE

To present the characteristics of the early audiologic phenotype in hearing impaired patients with biallelic mutations in the USH2A gene based on systematic analysis of the audiological data.

PATIENTS AND METHODS

13 patients with mutations in the USH2A gene underwent audiological examination. Most of them were found among a large group of infants with bilateral nonsyndromic sensorineural hearing loss (SNHL) examined under 12 months.

RESULTS

Eight out of eleven children failed UNHS and were initially diagnosed as having bilateral nonsyndromic SNHL. Seven children underwent an audiological assessment before the age of 9 months. The earliest audiological examination was carried out at 1 and 3 months. The children with pathogenic variants in the USH2A gene in our examined group were identified in the first year of life via UNHS. The hearing threshold levels (HTL) for the USH2A group are compactly distributed between 51.25 dB and 66.25 dB, quartiles are 54 dB and 63.4 dB, with a median of 60 dB. The audiological profile of patients with biallelic USH2A mutations differs from audiograms of patients who had STRC-related hearing loss. We have not found any significant elevation in hearing thresholds in the first decade of life. We also estimated the prevalence of the USH2A and STRC mutations among GJB2-negative infants with bilateral nonsyndromic SNHL examined under 12 months, and it was 7.5% and 16.1%, respectively.

CONCLUSION

According to our results, the early hearing phenotype in pediatric patients with biallelic mutations in the USH2A- gene is characterized by nonsyndromic mild-to-moderate SNHL in the first decade of life. Our results indicate that the presence of mutations in the USH2A or STRC genes can be expected in a child with congenital mild-to-moderate nonsyndromic SNHL. This information is of practical importance for parents, as they have to know the prognosis of hearing loss for their child from the very beginning. Post-screening follow-up should include adequate clinical, genetic, and social support for children and their parents.

Retinal Phenotype of Patients with CLRN1-Associated Usher 3A Syndrome in French Light4Deaf Cohort

Purpose

Biallelic variants in CLRN1 are responsible for Usher syndrome 3A and non-syndromic rod–cone dystrophy (RCD). Retinal findings in Usher syndrome 3A have not been well defined. We report the detailed phenotypic description of RCD associated with CLRN1 variants in a prospective cohort.

Methods

Patients were clinically investigated at the National Reference Center for rare ocular diseases at the Quinze-Vingts Hospital, Paris, France. Best-corrected visual acuity (BCVA) tests, Goldmann perimetry, full-field electroretinography (ffERG), retinal photography, near-infrared reflectance, short-wavelength and near-infrared autofluorescence, and optical coherence tomography (OCT) were performed for all patients.

Results

Four patients from four unrelated families were recruited. Mean follow-up was 11 years for three patients, and only baseline data were available for one subject. Median BCVA at baseline was 0.2 logMAR (range, 0.3–0). ffERG responses were undetectable in all subjects. The III4e isopter of the Goldmann visual field was constricted to 10°. The retinal phenotype was consistent in all patients: small whitish granular atrophic areas were organized in a network pattern around the macula and in the midperiphery. OCT showed intraretinal microcysts in all patients. Upon follow-up, all patients experienced a progressive BCVA loss and further visual field constriction. Four distinct pathogenic variants were identified in our patients: two missense (c.144T>G, p.(Asn48Lys) and c.368C>A, p.(Ala123Asp)) and two frameshift variants (c.176del, p.(Gly59Valfs*13) and c.230dup, p.(Ala78Serfs*52)).

Conclusions

RCD in Usher 3A syndrome has some distinctive features. It is a severe photoreceptor dystrophy with whitish granular posterior pole appearance and cystic maculopathy.

SD-OCT analysis in syndromic and non-syndromic forms of retinitis pigmentosa due to USH2A gene mutations

INTRODUCTION

This study aims to analyze macular structure by using SD-OCT in a cohort of patients affected by autosomal recessive retinitis pigmentosa and Usher syndrome, due to genetic variants in USH2A gene, and to correlate OCT parameters with functional and genetic data.

METHODS

The subjects of this study were 92 patients, 46 syndromic (Ush2) and 46 non-syndromic (arRP), with clinical and genetic diagnosis of USH2A-related retinal dystrophy, who underwent a complete ophthalmic examination and spectral domain OCT analysis. The study focused on evaluating the differences between the two groups in the following parameters: best corrected visual acuity (BCVA), ellipsoid zone width (EZ), presence of epiretinal membrane (ERM) and cystic macular lesions (CML). Variants in USH2A gene were divided in 3 categories, according to the expected impact (low/high) at protein level of the different variants on each allele.

RESULTS

BCVA and EZ width were significantly lower in Ush2 than in arRP patients (p < 0.0001 and p = 0.001). ERM was detected in 34.8% (16/46) of arRP patients and in 65.2% (30/46) of Ush2 patients (p = 0.003). CML was detected in 17.4% (8/46) of arRP patients and 30.4% (14/46) of Ush2 patients (p = 0.14). The allelic distribution was statistically different (p = 0.0003) by dividing the two diseases: for Ush2 patients it was 45.7% (high/high), 39.1% (low/high) and 15.2% (low/low); for arRP patients it was 8.7% (high/high), 56.5% (low/high) and 34.8% (low/low). The severity class of the variants significantly affected VA and EZ width parameters (p = 0.004 and p = 0.002, respectively).

CONCLUSION

Retinal disease, as evaluated by means of SD-OCT, shows more advanced degeneration signs in the syndromic than the non-syndromic form of retinal dystrophy related to USH2A gene. Variant types and allelic profiles are determining factors for the onset of syndromic features. However, since the three allelic profiles can be found in both Usher and RP patients, other factors must necessarily play a determining role.

Characteristics of Retinitis Pigmentosa Associated with ADGRV1 and Comparison with USH2A in Patients from a Multicentric Usher Syndrome Study Treatrush

In contrast to USH2A, variants in ADGRV1 are a minor cause of Usher syndrome type 2, and the associated phenotype is less known. The purpose of the study was to characterize the retinal phenotype of 18 ADGRV1 patients (9 male, 9 female; median age 52 years) and compare it with that of 204 USH2A patients (111 male, 93 female; median age 43 years) in terms of nyctalopia onset, best corrected visual acuity (BCVA), fundus autofluorescence (FAF), and optical coherence tomography (OCT) features. There was no statistical difference in the median age at onset (30 and 18 years; Mann–Whitney U test, p = 0.13); the mean age when 50% of the patients reached legal blindness (≥1.0 log MAR) based on visual acuity (64 years for both groups; log-rank, p = 0.3); the risk of developing advanced retinal degeneration (patch or atrophy) with age (multiple logistic regression, p = 0.8); or the frequency of cystoid macular edema (31% vs. 26%, Fisher’s exact test, p = 0.4). ADGRV1 and USH2A retinopathy were indistinguishable in all major functional and structural characteristics, suggesting that the loss of function of the corresponding proteins produces similar effects in the retina. The results are important for counseling ADGRV1 patients, who represent the minor patient subgroup.

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.

Genetics, pathogenesis and therapeutic developments for Usher syndrome type 2

Usher syndrome (USH) is a rare, autosomal recessively inherited disorder resulting in a combination of sensorineural hearing loss and a progressive loss of vision resulting from retinitis pigmentosa (RP), occasionally accompanied by an altered vestibular function. More and more evidence is building up indicating that also sleep deprivation, olfactory dysfunction, deficits in tactile perception and reduced sperm motility are part of the disease etiology. USH can be clinically classified into three different types, of which Usher syndrome type 2 (USH2) is the most prevalent. In this review, we, therefore, assess the genetic and clinical aspects, available models and therapeutic developments for USH2. Mutations in USH2A, ADGRV1 and WHRN have been described to be responsible for USH2, with USH2A being the most frequently mutated USH-associated gene, explaining 50% of all cases. The proteins encoded by the USH2 genes together function in a dynamic protein complex that, among others, is found at the photoreceptor periciliary membrane and at the base of the hair bundles of inner ear hair cells. To unravel the pathogenic mechanisms underlying USH2, patient-derived cellular models and animal models including mouse, zebrafish and drosophila, have been generated that all in part mimic the USH phenotype. Multiple cellular and genetic therapeutic approaches are currently under development for USH2, mainly focused on preserving or partially restoring the visual function of which one is already in the clinical phase. These developments are opening a new gate towards a possible treatment for USH2 patients.

Auditory and olfactory findings in patients with USH2A-related retinal degeneration-Findings at baseline from the rate of progression in USH2A-related retinal degeneration natural history study (RUSH2A)

Sensorineural hearing loss (SNHL) is characteristic of Usher syndrome type 2 (USH2), but less is known about SNHL in nonsyndromic autosomal recessive retinitis pigmentosa (ARRP) and olfaction in USH2A-associated retinal degeneration. The Rate of Progression of USH2A-related Retinal Degeneration (RUSH2A) is a natural history study that enrolled 127 participants, 80 with USH2 and 47 with ARRP. Hearing was measured by pure-tone thresholds and word recognition scores, and olfaction by the University of Pennsylvania Smell Identification Test (UPSIT). SNHL was moderate in 72% of USH2 participants and severe or profound in 25%, while 9% of ARRP participants had moderate adult-onset SNHL. Pure-tone thresholds worsened with age in ARRP but not in USH2 participants. The degree of SNHL was not associated with other participant characteristics in either USH2 or ARRP. Median pure-tone thresholds in ARRP participants were significantly higher than the normative population (p < 0.001). Among 14 USH2 participants reporting newborn hearing screening results, 7 reported passing. Among RUSH2A participants, 7% had mild microsmia and 5% had moderate or severe microsmia. Their mean (±SD) UPSIT score was 35 (±3), similar to healthy controls (34 [±3]; p = 0.39). Olfaction differed by country (p = 0.02), but was not significantly associated with clinical diagnosis, age, gender, race/ethnicity, smoking status, visual measures, or hearing. Hearing loss in USH2A-related USH2 did not progress with age. ARRP patients had higher pure-tone thresholds than normal. Newborn hearing screening did not identify all USH2A-related hearing loss. Olfaction was not significantly worse than normal in participants with USH2A-related retinal degeneration.

Retinal Phenotype of Patients With Isolated Retinal Degeneration Due to CLN3 Pathogenic Variants in a French Retinitis Pigmentosa Cohort

Importance

Biallelic variants in CLN3 lead to a spectrum of diseases, ranging from severe neurodegeneration with retinal involvement (juvenile neuronal ceroid lipofuscinosis) to retina-restricted conditions.

Objective

To provide a detailed description of the retinal phenotype of patients with isolated retinal degeneration harboring biallelic CLN3 pathogenic variants and to attempt a phenotype-genotype correlation associated with this gene defect.

Design, Setting, and Participants

This retrospective cohort study included patients carrying biallelic CLN3 variants extracted from a cohort of patients with inherited retinal disorders (IRDs) investigated at the National Reference Center for Rare Ocular Diseases of the Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts from December 2007 to August 2020. Data were analyzed from October 2019 to August 2020.

Main Outcome and Measures

Functional (best-corrected visual acuity, visual field, color vision, and full-field electroretinogram), morphological (multimodal retinal imaging), and clinical data from patients were collected and analyzed. Gene defect was identified by either next-generation sequencing or whole-exome sequencing and confirmed by Sanger sequencing, quantitative polymerase chain reaction, and cosegregation analysis.

Results

Of 1533 included patients, 843 (55.0%) were women and 690 (45.0%) were men. A total of 15 cases from 11 unrelated families harboring biallelic CLN3 variants were identified. All patients presented with nonsyndromic IRD. Two distinct patterns of retinal disease could be identified: a mild rod-cone degeneration of middle-age onset (n = 6; legal blindness threshold reached by 70s) and a severe retinal degeneration with early macular atrophic changes (n = 9; legal blindness threshold reached by 40s). Eleven distinct pathogenic variants were detected, of which 4 were novel. All but 1, p.(Arg405Trp), CLN3 point variants and their genotypic associations were clearly distinct between juvenile neuronal ceroid lipofuscinosis and retina-restricted disease. Mild and severe forms of retina-restricted CLN3-linked IRDs also had different genetic background.

Conclusions and Relevance

These findings suggest CLN3 should be included in next-generation sequencing panels when investigating patients with nonsyndromic rod-cone dystrophy. These results document phenotype-genotype correlations associated with specific variants in CLN3. However, caution seems warranted regarding the potential neurological outcome if a pathogenic variant in CLN3 is detected in a case of presumed isolated IRD for the onset of neurological symptoms could be delayed.

Usher Syndrome: Genetics of a Human Ciliopathy

Usher syndrome (USH) is an autosomal recessive syndromic ciliopathy characterized by sensorineural hearing loss, retinitis pigmentosa and, sometimes, vestibular dysfunction. There are three clinical types depending on the severity and age of onset of the symptoms; in addition, ten genes are reported to be causative of USH, and six more related to the disease. These genes encode proteins of a diverse nature, which interact and form a dynamic protein network called the "Usher interactome". In the organ of Corti, the USH proteins are essential for the correct development and maintenance of the structure and cohesion of the stereocilia. In the retina, the USH protein network is principally located in the periciliary region of the photoreceptors, and plays an important role in the maintenance of the periciliary structure and the trafficking of molecules between the inner and the outer segments of photoreceptors. Even though some genes are clearly involved in the syndrome, others are controversial. Moreover, expression of some USH genes has been detected in other tissues, which could explain their involvement in additional mild comorbidities. In this paper, we review the genetics of Usher syndrome and the spectrum of mutations in USH genes. The aim is to identify possible mutation associations with the disease and provide an updated genotype-phenotype correlation.

Novel TTLL5 Variants Associated with Cone-Rod Dystrophy and Early-Onset Severe Retinal Dystrophy

Variants of the TTLL5 gene, which encodes tubulin tyrosine ligase-like family member five, are a rare cause of cone dystrophy (COD) or cone-rod dystrophy (CORD). To date, only a few TTLL5 patients have been clinically and genetically described. In this study, we report five patients harbouring biallelic variants of TTLL5. Four adult patients presented either COD or CORD with onset in the late teenage years. The youngest patient had a phenotype of early onset severe retinal dystrophy (EOSRD). Genetic analysis was performed by targeted next generation sequencing of gene panels and assessment of copy number variants (CNV). We identified eight variants, of which six were novel, including two large multiexon deletions in patients with COD or CORD, while the EOSRD patient harboured the novel homozygous p.(Trp640*) variant and three distinct USH2A variants, which might explain the observed rod involvement. Our study highlights the role of TTLL5 in COD/CORD and the importance of large deletions. These findings suggest that COD or CORD patients lacking variants in known genes may harbour CNVs to be discovered in TTLL5, previously undetected by classical sequencing methods. In addition, variable phenotypes in TTLL5-associated patients might be due to the presence of additional gene defects.

Molecular Inversion Probe-Based Sequencing of USH2A Exons and Splice Sites as a Cost-Effective Screening Tool in USH2 and arRP Cases

A substantial proportion of subjects with autosomal recessive retinitis pigmentosa (arRP) or Usher syndrome type II (USH2) lacks a genetic diagnosis due to incomplete USH2A screening in the early days of genetic testing. These cases lack eligibility for optimal genetic counseling and future therapy. USH2A defects are the most frequent cause of USH2 and are also causative in individuals with arRP. Therefore, USH2A is an important target for genetic screening. The aim of this study was to assess unscreened or incompletely screened and unexplained USH2 and arRP cases for (likely) pathogenic USH2A variants. Molecular inversion probe (MIP)-based sequencing was performed for the USH2A exons and their flanking regions, as well as published deep-intronic variants. This was done to identify single nucleotide variants (SNVs) and copy number variants (CNVs) in 29 unscreened or partially pre-screened USH2 and 11 partially pre-screened arRP subjects. In 29 out of these 40 cases, two (likely) pathogenic variants were successfully identified. Four of the identified SNVs and one CNV were novel. One previously identified synonymous variant was demonstrated to affect pre-mRNA splicing. In conclusion, genetic diagnoses were obtained for a majority of cases, which confirms that MIP-based sequencing is an effective screening tool for USH2A. Seven unexplained cases were selected for future analysis with whole genome sequencing.

Correlation between Genotype and Phenotype in 69 Chinese Patients with USH2A Mutations: A comparative study of the patients with Usher Syndrome and Nonsyndromic Retinitis Pigmentosa

PURPOSE

The aim of this study was to analyse 69 Chinese patients with USH2A mutations and to assess the genotype-phenotype correlation.

METHODS

All 36 Usher syndrome type IIA patients and 33 nonsyndromic RP (retinitis pigmentosa) patients underwent clinical examinations. Eye examinations included best-corrected visual acuity, slit-lamp biomicroscopy, fundus examination with dilated pupils, fundus fluorescent angiography, visual field test, full-field electroretinography and optic coherence tomography; audiological assessment included pure tone audiometry and hearing thresholds. The molecular diagnosis of genotype combined the single-gene Sanger sequencing and next-generation sequencing. This study is a retrospective study.

RESULTS

The mean age of first symptoms with Usher syndrome type IIa and nonsyndromic RP patients was 13.7 versus 29.8 years (ocular phenotypes, p < 0.001); 17.7 versus 29.9 years (nyctalopia, p < 0.001); 44.7 versus 54.8 years (low vision based on VF, p < 0.001); 41.7 versus 54.7 years (low vision based on VA, p < 0.001); and 46.0 versus 56.7 years (legal blindness based on VF, p < 0.001). There was significant difference in variants in the two groups (p < 0.05). Among patients with mutation c.2802T > G (p.Cys934Trp), more (66.7%) presented with normal hearing. All patients (3/3, 100%) with the variant c.8232G > C (p.Trp2744Cys) had hearing loss. Furthermore, we identified 23 novel variants in USH2A.

CONCLUSIONS

Patients with Usher syndrome type IIa had an earlier onset of the disease, inferior visual function and presented with more truncating variants, compared with the nonsyndromic RP patients.

The genetics of rod-cone dystrophy in Arab countries: a systematic review

Since a substantial difference in the prevalence of genetic causes of rod-cone dystrophy (RCD) was found among different populations, we conducted a systematic review of the genetic findings associated with RCD in Arab countries. Of the 816 articles retrieved from PubMed, 31 studies conducted on 407 participants from 11 countries were reviewed. Next-generation sequencing (NGS) was the most commonly used technique (68%). Autosomal recessive pattern was the most common pattern of inheritance (97%) and half of the known genes associated with RCD (32/63) were identified. In the Kingdom of Saudi Arabia, in addition to RP1 (20%) and TULP1 (20%), gene defects in EYS (8%) and CRB1 (7%) were also prevalently mutated. In North Africa, the main gene defects were in MERTK (18%) and RLBP1 (18%). Considering all countries, RP1 and TULP1 remained the most prevalently mutated. Variants in TULP1, RP1, EYS, MERTK, and RLBP1 were the most prevalent, possibly because of founder effects. On the other hand, only ten Individuals were found to have dominant or X-linked RCD. This is the first time a catalog of RCD genetic variations has been established in subjects from the Arabi countries. Although the last decade has seen significant interest, expertise, and an increase in RCD scientific publication, much work needs to be conducted.

USH2A gene variants cause Keratoconus and Usher syndrome phenotypes in Pakistani families

Background

Retinitis pigmentosa (RP) is the most common inherited retinal dystrophy, affecting approximately 1 in 4000 individuals worldwide. The most common form of syndromic RP is Usher syndrome (USH) accounting for approximately 20–30 % of RP cases. Mutations in the USH2A gene cause a significant proportion of recessive non-syndromic RP and USH type II (USH2). This study aimed to determine the causative role of the USH2A gene in autosomal recessive inherited ocular diseases and to establish genotype-phenotype correlation associated with USH2A variants.

Methods

We performed direct Sanger sequencing and co-segregation analysis of the USH2A gene to identify disease causing variants in a non-syndromic RP family, two USH2 families and two Keratoconus (KC) families.

Results

Disease causing variants in the USH2A gene were identified in two families displayed KC and USH2 phenotypes. A novel variant c.4029T > G, p.Asn1343Lys in the USH2A gene was detected in a Pakistani family with KC phenotype. In addition, a missense variant (c.7334 C > T, p. Ser2445Phe) in the USH2A gene was found segregating in another Pakistani family with USH2 phenotype. Homozygosity of identified missense USH2A variants was found associated with autosomal recessive inherited KC and USH2 phenotypes in investigated families. These variants were not detected in ethnically matched healthy controls. Moreover, the USH2A variants were predicted to be deleterious or potentially disease causing by PolyPhen-2, PROVEAN and SIFT.

Conclusions

This study provided first evidence for association of a novel USH2A variant with KC phenotype in a Pakistani family as well as established the phenotype-genotype correlation of a USH2A variant (c.7334 C > T, p. Ser2445Phe) with USH2 phenotype in another Pakistani family. The phenotype-genotype correlations established in present study may improve clinical diagnosis of affected individuals for better management and counseling.

Antisense oligonucleotide-based treatment of retinitis pigmentosa caused by USH2A exon 13 mutations

Mutations in USH2A are among the most common causes of syndromic and non-syndromic retinitis pigmentosa (RP). The two most recurrent mutations in USH2A, c.2299delG and c.2276G > T, both reside in exon 13. Skipping exon 13 from the USH2A transcript presents a potential treatment modality in which the resulting transcript is predicted to encode a slightly shortened usherin protein. Morpholino-induced skipping of ush2a exon 13 in zebrafish ush2a^rmc1 mutants resulted in the production of usherinΔexon 13 protein and a completely restored retinal function. Antisense oligonucleotides were investigated for their potential to selectively induce human USH2A exon 13 skipping. Lead candidate QR-421a induced a concentration-dependent exon 13 skipping in induced pluripotent stem cell (iPSC)-derived photoreceptor precursors from an Usher syndrome patient homozygous for the c.2299delG mutation. Mouse surrogate mQR-421a reached the retinal outer nuclear layer after a single intravitreal injection and induced a detectable level of exon skipping until at least 6 months post-injection. In conclusion, QR-421a-induced exon skipping proves to be a highly promising treatment option for RP caused by mutations in USH2A exon 13.

Genetic investigation of 211 Chinese families expands the mutational and phenotypical spectra of hereditary retinopathy genes through targeted sequencing technology

BACKGROUND

Hereditary retinopathy is a significant cause of blindness worldwide. Despite the discovery of many mutations in various retinopathies, a large number of patients remain genetically undiagnosed. Targeted next-generation sequencing of the human genome is a suitable approach for the molecular diagnosis of retinopathy.

METHODS

We describe a cohort of 211 families from central China with various forms of retinopathy; 95 patients were investigated using multigene panel sequencing, and the other 116 with suspected Leber hereditary optic neuropathy (LHON) were tested by Sanger sequencing. The detected variation of targeted sequencing was verified by PCR-based Sanger sequencing. We performed a comprehensive analysis of the cases using sequencing data and ophthalmologic examination information.

RESULTS

Potential causal mutations were identified in the majority of families with retinopathy (57.9% of 95 families) and suspected LHON (21.6% of 116 families). There were 68 variants of a certain significance distributed in 31 known disease-causing genes in the 95 families; 37 of the variants are novel and have not been reported to be related to hereditary retinopathy. The NGS panel solution provided a 45.3% potential diagnostic rate for retinopathy families, with candidate gene mutations of undefined pathogenicity revealed in another 12.6%of the families.

CONCLUSION

Our study uncovered novel mutations and phenotypic aspects of retinopathy and demonstrated the genetic and clinical heterogeneity of related conditions. The findings show the detection rate of pathogenic variants in patients with hereditary retinopathy in central China as well as the diversity and gene distribution of these variants. The significance of molecular genetic testing for patients with hereditary retinopathy is also highlighted.