Genetic analysis and clinical features of X-linked retinoschisis in Chinese patients

The D126G mutation contributes to the early-onset X-linked juvenile retinoschisis

X-linked juvenile retinoschisis (XLRS) is an inherited retinal disease caused by mutations in the RS1 gene, resulting in splitting of the retinal layers and visual disturbances. To provide insights on this disease in our cohort, genetic examination, clinical presentation, and functional analysis were performed. We observed three main RS1 mutations in our cohort of six unrelated patients: RS1-D126G, RS1-R209H, and RS1-R213W. The RS1-D126G mutation, exclusively reported in Thai patients so far, showed the highest prevalence. Phenotypically, the D126G mutation manifested early (0.3-4 years old), presenting as asymmetrical visual acuity and schisis. Functional analysis revealed that the molecular pathomechanism of D126G was the failure of protein secretion attributable to endoplasmic reticulum retention. The understanding of the genotype-phenotype relationship and the pathomechanisms of specific mutations in a particular population could immensely benefit the pipeline of personalised treatment design for XLRS.

X-LINKED JUVENILE RETINOSCHISIS ASSOCIATED WITH AN RS1 IN-FRAME DELETION AND BILATERAL CENTRAL SEROUS CHORIORETINOPATHY

PURPOSE

To report the case of a patient with X-linked juvenile retinoschisis, caused by an in-frame deletion of the RS1 gene, who presented with visual loss because of bilateral central serous chorioretinopathy.

METHODS

Observational case report.

RESULTS

A 34-year-old man, with type-A personality, presented with a one-month history of decreased visual acuity and metamorphopsia in his right eye. Funduscopic examination showed a dome-like foveal elevation in both eyes as well as subtle pigmentary changes of the retinal pigment epithelium with a tapetal reflex in the fovea. Spectral-domain optical coherence tomography revealed intraretinal cystic foveal changes and serous retinal detachment in both eyes. Fundus fluorescein angiography of both eyes showed a focal area of intense hyperfluorescence with leakage in late phases. Electroretinogram revealed a markedly attenuated b-wave and a diminished a-wave in photopic and scotopic phases. Genetic testing revealed a hemizygous c.282_284delCTT deletion in the RS1 gene, predicting a p.Ser95del change at the protein level. The patient was diagnosed with X-linked juvenile retinoschisis and central serous chorioretinopathy as a coexisting condition. Patient was observed during a 3-month period but showed no improvement. Therefore, subthreshold micropulse laser was applied, achieving complete resolution of signs and symptoms of central serous chorioretinopathy.

CONCLUSION

Central serous chorioretinopathy can be a cause of acute or subacute visual loss in patients with X-linked juvenile retinoschisis when other complications such as vitreous hemorrhage and retinal detachment have been excluded.

Vitreous Hemorrhage in Pediatric Patients With X-Linked Retinoschisis: Characteristics and Outcomes

OBJECTIVE

To report the management and outcomes of vitreous hemorrhage in pediatric patients with X-linked retinoschisis (XLRS).

MATERIALS AND METHODS

Retrospective case series of pediatric patients with XLRS with vitreous hemorrhage between January 2000 and January 2022 at the Bascom Palmer Eye Institute.

RESULTS

Nine patients (12 eyes) met inclusion criteria. The average age at presentation was 5.75 years and mean follow-up time was 6 years. All eyes (58.3%) that underwent fluorescein angiography exhibited peripheral capillary dropout. Six of 12 eyes (50%) were observed without intervention. Four of 12 eyes (33.3%) underwent intravitreal injection of bevacizumab and 2 (16.6%) underwent vitreoretinal surgery. Seven of 12 eyes (58.3%) had documented recurrence of vitreous hemorrhage during follow-up. All retinas were attached and had clear media at final follow-up.

CONCLUSION

Fluorescein angiography is a helpful tool to evaluate the vascular phenotype in XLRS. Favorable anatomic outcomes were noted in this cohort, but recurrence of vitreous hemorrhage was common. [Ophthalmic Surg Lasers Imaging Retina 2023;54:513-518.].

Retinal honeycomb appearance and its role in patients with X-linked retinoschisis

BACKGROUND

To investigate the clinical characteristics of retinal honeycomb appearance in a large cohort of patients with X-linked retinoschisis (XLRS) and to determine whether it is associated with complications like retinal detachment (RD) and vitreous hemorrhage (VH).

METHODS

A retrospective observational case series. A chart review of medical records, wide-field fundus imaging, and optical coherence tomography (OCT) was performed on 78 patients (153 eyes) diagnosed with XLRS at Beijing Tongren eye center between Dec 2017 and Feb 2022. The chi-square test or Fisher exact test was performed on the 2 × 2 cross-tabulations of honeycomb appearance and other peripheral retinal findings and complications.

RESULTS

Thirty-eight patients (48.7%), and 60 eyes (39.2%) had a honeycomb appearance of different areas on the fundus. The supratemporal quadrant was the most commonly affected (45 eyes, 75.0%), followed by the infratemporal (23 eyes, 38.3%), the infranasal (10 eyes,16.7%), and supranasal (9 eyes,15.0%). The appearance was significantly associated with peripheral retinoschisis, inner retinal layer break, outer retinal layer break, RD, and rhegmatogenous retinal detachment (RRD) (p < 0.01, p = 0.032, p < 0.01, p = 0.008, p < 0.01, respectively). All the eyes complicated with RRD had the appearance. None of the eyes without the appearance had RRD.

CONCLUSIONS

The data suggest that the honeycomb appearance is not uncommon in patients with XLRS and is more likely to be accompanied by an RRD, and inner and outer layer breaks, thus should be treated with caution and close observation.

AAV2/4-RS1 gene therapy in the retinoschisin knockout mouse model of X-linked retinoschisis

OBJECTIVE

To evaluate efficacy of a novel adeno-associated virus (AAV) vector, AAV2/4-RS1, for retinal rescue in the retinoschisin knockout (Rs1-KO) mouse model of X-linked retinoschisis (XLRS). Brinzolamide (Azopt®), a carbonic anhydrase inhibitor, was tested for its ability to potentiate the effects of AAV2/4-RS1.

METHODS

AAV2/4-RS1 with a cytomegalovirus (CMV) promoter (2x1012 viral genomes/mL) was delivered to Rs1-KO mice via intravitreal (N = 5; 1μL) or subretinal (N = 21; 2μL) injections at postnatal day 60-90. Eleven mice treated with subretinal therapy also received topical Azopt® twice a day. Serial full field electroretinography (ERG) was performed starting at day 50-60 post-injection. Mice were evaluated using a visually guided swim assay (VGSA) in light and dark conditions. The experimental groups were compared to untreated Rs1-KO (N = 11), wild-type (N = 12), and Rs1-KO mice receiving only Azopt® (N = 5). Immunofluorescence staining was performed to assess RS1 protein expression following treatment.

RESULTS

The ERG b/a ratio was significantly higher in the subretinal plus Azopt® (p<0.0001), subretinal without Azopt® (p = 0.0002), and intravitreal (p = 0.01) treated eyes compared to untreated eyes. There was a highly significant subretinal treatment effect on ERG amplitudes collectively at 7-9 months post-injection (p = 0.0003). Cones showed more effect than rods. The subretinal group showed improved time to platform in the dark VGSA compared to untreated mice (p<0.0001). RS1 protein expression was detected in the outer retina in subretinal treated mice and in the inner retina in intravitreal treated mice.

CONCLUSIONS

AAV2/4-RS1 shows promise for improving retinal phenotype in the Rs1-KO mouse model. Subretinal delivery was superior to intravitreal. Topical brinzolamide did not improve efficacy. AAV2/4-RS1 may be considered as a potential treatment for XLRS patients.

A novel mutation in RS1 and clinical manifestations in a Chinese twin family with congenital retinoschisis

Purpose: We aim to analyze the clinical and genetic features in a Chinese family with congenital retinoschisis by whole-exome sequencing and comprehensive clinical examination.

Methods: Six members were recruited from a Chinese family. Three of them were diagnosed as congenital retinoschisis, including two twin siblings. All subjects received a full eye examination. Whole-exome sequencing (WES) and Sanger sequencing were performed on two twin probands and all participants, respectively.

Results: A novel splice site mutation RS1.c.53-1G&gt;A was identified in a Chinese congenital retinoschisis family. The mean onset age was 16.7 ± 2.4 years old. The average BCVA in patients was 0.37 ± 0.05. A typical spoke-wheel pattern was observed in all affected eyes. OCT examination results showed fovea schisis and schisis cavities were located in the inner nuclear layer in 100% eyes (6/6). ERG b/a ratio was decreased markedly, but was still more than 1 in the four eyes that were available.

Conclusion: The present study discovered a new pathogenic splice cite variant of RS1 in congenital retinoschisis, which expands the mutational spectrum. In contrast to previous research, the phenotype of patients with the same mutation within one family was highly similar. Early molecular testing is crucial for early diagnosis, clinical management, and genetic counseling of patients with congenital retinoschisis.

Genotype and phenotype characteristics of X-linked retinoschisis: the first report of a Turkish population

BACKGROUND

X-linked retinoschisis is an inherited retinal disease caused by mutations in the RS1 gene; however, a genotype-phenotype correlation regarding the mutation type or location within the RS1 gene and clinical characteristics of the patients has not been established yet. This is the first report documenting the genotypes and ophthalmological findings in a Turkish population with confirmed RS1 mutations.

MATERIALS AND METHODS

Fifty eyes of 25 male patients were included in the study. RS1 mutation analysis was performed by DNA sequencing. Retrospective analysis of ocular examinations and SD-OCT scans were applied.

RESULTS

The major mutation was c.422 G > A (p.Arg141His, exon 5) affecting 14 patients (56%) and c.531 T > G was the only non-sense mutation out of 7 pathogenic variants. At presentation; the mean age was 24.6 ± 16.2 (4-72) years, mean visual acuity (VA) was 0.61 ± 0.32 (logMAR, 0.10-1.30). Forty-six (92%) eyes had macular, 16 eyes (32%) had peripheral retinoschisis. None of the eyes had macular scar, whereas 7 eyes (14%) had macular atrophy. The most frequent location of schisis was inner nuclear layer (37.5%). The eyes with disruption of ellipsoid zone (EZ) or external limiting membrane (ELM) had worse VA (for EZ, 0.65 ± 0.25 versus 0.45 ± 0.34, logMAR, 31 versus 17 eyes, p = .013; for ELM, 0.66 ± 0.27 versus 0.45 ± 0.31, logMAR, 30 versus 18 eyes, p = .008).

CONCLUSIONS

Seven different pathogenic variants in the RS1 gene were identified; with c.422 G > A (p.Arg141His) as the most frequent variant and c.531 T > G as only non-sense mutation. Having EZ or ELM disruption were the significant factors affecting VA.

Clinical and Genetic Study of X-Linked Juvenile Retinoschisis in the Czech Population

The aim of this study was to identify RS1 pathogenic variants in Czech patients with X-linked retinoschisis (XLRS) and to describe the associated phenotypes, including natural history, in some cases. Twenty-one affected males from 17 families were included. The coding region of RS1 was directly sequenced and segregation of the identified mutations was performed in available family members. In total, 12 disease-causing variants within RS1 were identified; of these c.20del, c.275G>A, c.[375_379del; 386A>T], c.539C>A and c.575_576insT were novel, all predicted to be null alleles. The c.539C>A mutation occurred de novo. Three patients (aged 8, 11 and 19 years) were misdiagnosed as having intermediate uveitis and treated with systemic steroids. Repeat spectral domain optical coherence tomography examinations in four eyes documented the transition from cystoid macular lesions to macular atrophy in the fourth decade of life. Four individuals were treated with topical dorzolamide and in two of them, complete resolution of the cystic macular lesions bilaterally was achieved, while one patient was noncompliant. Rebound phenomenon after discontinuation of dorzolamide for 7 days was documented in one case. Misdiagnosis of XLRS for uveitis is not uncommon; therefore, identification of disease-causing variants is of considerable benefit to the affected individuals.

Whole-exome sequencing identifies an RS1 variant in a Chinese family with X-linked retinoschisis

A notable behavioural feature of X-linked retinoschisis (XLRS) is extensive structural schisis (splitting) of the outer plexiform and inner nuclear layers of the neurosensory retina, which is partly combined with complications related to vitreous hemorrhage, macular holes and retinal detachment. The present study aimed to identify the pathogenic gene mutation in a three-generation Chinese family with XLRS by whole-exome sequencing (WES). The clinical information of a three-generation Chinese family with cases of XLRS was collected. WES was performed for the proband. A comparison with the human reference genome sequence (hg38) and bioinformatic analysis were performed to reveal putative variants and Sanger sequencing was applied to verify mutations in this family and healthy control participants. Intraretinal cystic spaces were detected by optical coherence tomography imaging. Structures of the wild-type and mutant retinoschisin 1 (RS1) protein were modelled by PyMol. Almost all patients had a history of vision loss and abnormal blue-purple colour vision; however, the phenotypes of the 4 patients were distinctly different. There was no linear correlation between phenotypic severity and age. A recurrent RS1 (Xp22.2) mutation (NM_000330: c.559C>T) was detected, resulting in the p.Q187X variant. According to the protein model, this variant is likely pathogenic. The present study was the first to report that RS1:c.559C>T induces XLRS in a three-generation Chinese pedigree, with the mutation leading to premature termination of translation of the RS1 protein. WES was able to diagnose XLRS, which has the characteristics of clinical and genetic heterogeneity.

Comprehensive analysis of genetic and clinical characteristics of 30 patients with X-linked juvenile retinoschisis in China

Purpose

To provides the clinical and genetic characteristics of a series of Chinese patients with X‐linked juvenile retinoschisis (XLRS) through multimodal imaging and next‐generation sequencing.

Methods

Thirty patients (60 eyes) from 29 unrelated families of Chinese origin with XLRS were screened using multigene panel testing, and underwent a complete clinical evaluation. All variants identified in this study and reported in the Human Gene Mutation Database were analysed.

Results

Twenty‐five distinct variants in the retinoschisin gene were identified, of which eight were novel, and one was de novo. Missense mutations were the most prevalent type, and mutation hot spot was localized in the discoidin domain. The mean Snellen best‐corrected visual acuity was 0.28 ± 0.17. Of all eyes presenting with schisis, 92.86% had lamellar schisis and 62.5% had peripheral schisis. Schisis changes mostly involved inner and outer nuclear layers. X‐linked juvenile retinoschisis (XLRS) patients had a high incidence of complications, and peripheral schisis was a risk factor for it. No obvious genotype–phenotype association was observed.

Conclusion

This study provides comprehensive analyses of the genetic and clinical characteristics of XLRS in a cohort of Chinese patients. The fourth de novo mutation in RS1 was identified. And we show that XLRS has a wide spectrum of clinical characteristics; hence, molecular diagnosis is crucial for its diagnosis, differential diagnosis and genetic counselling. Peripheral schisis is a risk factor for the high incidence of complications, and no clear genotype–phenotype correlations were found.

A novel mutation in the RS1 gene in a Chinese family with X-linked congenital retinoschisis

The purpose of the present study was to assess the clinical characteristics of X-linked retinoschisis (XLRS) in a Chinese family over a 7-year period with the aim of identifying possible genetic mutations associated with this disease. A total of 2 male siblings from a family with XLRS were followed up for 7 years and the best-corrected visual acuity and data obtained using slit-lamp microscopy, indirect ophthalmoscopy, fundus photography, spectral domain-optical coherence tomography (OCT), fundus autofluorescence and fundus fluorescence (FFA) and multifocal electroretinograms (ERG) were examined. The coding regions of the retinoschisin 1 (RS1) gene were amplified by PCR and sequenced directly. The proband exhibited blurred vision at 12 years old and was indicated to exhibit a typical phenotype of XLRS at 30 years old. The elder brother exhibited blurred vision at 11 years old and was diagnosed with XLRS at 33 years old. There was no change in the best-corrected visual acuities in the two patients over the 7 years. The OCT results suggested that there were intraretinal cysts and macular atrophy in the eyes of the older sibling, whilst a ‘spoke-wheel’ pattern was present in the macula of the younger sibling. In addition, OCT examination revealed foveal schisis. FFA analysis indicated a hyperfluorescent signal in the central macula. Multifocal ERG recordings indicated that responses were markedly reduced in the central and outer rings bilaterally. The central retinal thickness of the younger sibling increased but the central retinal thickness of the older sibling was not changed during the 7 years. Sequencing analysis revealed that the mutation was c.366G>A (p.Trp122^*) in exon 5 of Xp22.1. Gene mutation analysis indicated that the affected male siblings harbored a Trp122^* (c.366G>A) mutation, while the patients' mother was demonstrated to be a heterozygous carrier of the pathogenic mutation. To conclude, the present study discovered a novel XLRS mutation in a Chinese family, where the Trp122^* mutation caused a significant change in the function of the RS1 protein. Over the 7 years of observation, although the vision was not significantly impaired in the two patients examined, the central retinal thickness of the younger sibling increased but the central retinal thickness of the older sibling was not altered.

Clinical findings and RS1 genotype in 90 Chinese families with X-linked retinoschisis

Purpose

X-linked retinoschisis (XLRS) is an early-onset retinal degenerative disorder caused by mutations in the RS1 gene. The objective of this study was to describe the clinical and genetic findings in 90 unrelated Chinese patients with XLRS.

Methods

All patients underwent clinical examination, including best-corrected visual acuity (BCVA), slit-lamp biomicroscopy, fundus examination, and spectral domain-optical coherence tomography (SD-OCT). A combination of molecular screening methods, including Sanger-DNA sequencing of RS1 and targeted next-generation sequencing (TES), were used to detect mutations. In silico programs were used to analyze the pathogenicity of all the variants. Long-range PCR with subsequent DNA sequencing was employed to find the breakpoints of large deletions.

Results

The 90 probands (mean age 17.29±12.94 years; 3-52 years) showed a variety of clinical phenotypes, and their average best correct visual acuity was 0.81±0.48 (logarithm of the minimal angle of resolution, 0-3). Of the 175 eyes analyzed, 140 (80%) had macular retinoschisis, 84 (48%) had peripheral retinoschisis, 28 (16%) had macular atrophy, and five (3%) had a normal macular structure. We identified 68 mutations in this cohort of patients, including 15 novel mutations. Most mutations (65%) were missense; the remaining null mutations included nonsense, splicing effect, frameshift indel, and large genomic DNA deletions. The 62 patients with missense mutations seemed to have relatively milder visual defects than the 28 patients with null mutations.

Conclusions

Patients with RS1 mutations present profound phenotypic variability and show no clear genotype-phenotype correlations. Patients with null mutations tend to have more severe XLRS-related visual defects.

An Ophthalmic Targeted Exome Sequencing Panel as a Powerful Tool to Identify Causative Mutations in Patients Suspected of Hereditary Eye Diseases

Purpose

We evaluate the power of a next-generation sequencing-based ophthalmic targeted sequencing panel (NGS-based OTSP) as a genetics-testing tool for patients suspected of a wide range of hereditary eye diseases.

Methods

NGS-based OTSP encompasses 126 genes with identified mutations that account for the majority of Chinese families with hereditary eye diseases. A total of 568 probands suspected of having hereditary eye diseases underwent genetic testing by OTSP with targeted phenotype-driven analysis.

Results

NGS-based OTSP detected 329 potential pathogenic variants in 62 genes. These mutations might represent the genetic cause in 52% (293/568) of probands suspected of having hereditary eye diseases. Within the disease subgroups, the detection rates were 61% (124/202) for retinal degeneration disease, 53% (35/66) for eye tumors, 49% (53/108) for retinal vessel disease, 46% (13/28) for retinal detachment, 33% (19/58) for significant refractive error, 35% (16/46) for optic atrophy, 48% (11/23) for anterior segment dysgenesis, and 59% (22/37) for other hereditary eye diseases. These detection rates are comparable to those obtained in our previous study performed with whole exome sequencing. Mutations in the same gene were detected in different forms of hereditary eye diseases. The average turnaround time for OTSP is 30 days, and the average cost is 139 USD per patient.

Conclusions

NGS-based OTSP is a powerful tool for routine clinical genetic diagnostic testing in patients suspected of having hereditary eye diseases.

Translational Relevance

NGS-based OTSP can be used as a routine clinical test to improve the genetic counseling and medical care of patients suspected of having hereditary eye diseases.

A case of X-linked retinoschisis with atypical fundus appearance

PURPOSE

Mutations in the RS1 gene are known to cause retinoschisis, an X-linked hereditary retinal degeneration. Here, we present a case of atypical retinoschisis with clinical findings of retinoschisis and retinitis pigmentosa.

METHODS

This report is an observational case report. The detailed ophthalmological examinations included visual field determination, multimodal imaging and electrophysiological recordings. Targeted next-generation sequencing of a retinal disease gene panel was performed.

RESULTS

The 55-year-old male, highly hyperopic patient, presented with a best-corrected Snellen visual acuity of 20/100 in the right eye and 20/400 in the left eye. In the kinetic visual field, there was a superior scotoma, as well as a ring scotoma in the inferior hemisphere in the right eye and a concentric visual field constriction to 10° in the left eye. Funduscopy revealed marked pigmentary changes (i.e. bone spicules) in the mid-periphery bilaterally and symmetrically, as well as two small intra-retinal haemorrhages in the left eye. Full-field electroretinography recordings showed extinguished rod and cone responses. Diagnostic-genetic testing revealed a hemizygous missense mutation in the RS1 gene (c.305G > A; p.Arg102Gln) was identified.

CONCLUSION

We present a case of atypical retinoschisis with clinical findings of retinitis pigmentosa.

Cryo-EM of retinoschisin branched networks suggests an intercellular adhesive scaffold in the retina

Mutations in the essential retinal protein retinoschisin (RS1) cause a form of macular degeneration. Heymann et al. use cryo-EM to show that RS1 assembles into branched networks that may play a stabilizing role in maintaining the integrity of the retina.

Mutations in the retinal protein retinoschisin (RS1) cause progressive loss of vision in young males, a form of macular degeneration called X-linked retinoschisis (XLRS). We previously solved the structure of RS1, a 16-mer composed of paired back-to-back octameric rings. Here, we show by cryo–electron microscopy that RS1 16-mers can assemble into extensive branched networks. We classified the different configurations, finding four types of interaction between the RS1 molecules. The predominant configuration is a linear strand with a wavy appearance. Three less frequent types constitute the branch points of the network. In all cases, the “spikes” around the periphery of the double rings are involved in these interactions. In the linear strand, a loop (usually referred to as spike 1) occurs on both sides of the interface between neighboring molecules. Mutations in this loop suppress secretion, indicating the possibility of intracellular higher-order assembly. These observations suggest that branched networks of RS1 may play a stabilizing role in maintaining the integrity of the retina.

Advanced Diabetic Nephropathy with "Clean" Eyes: An Extreme Phenotype

INTRODUCTION

It is generally accepted that renal and eye changes in diabetes are concordant. There are however a fair number of patients with diabetes who have end-stage renal disease (ESRD) without any of the typical eye changes. The present study highlights the discordance between retinopathy and nephropathy and describes a series of patients of long-standing diabetes undergoing renal transplant who had little or no evidence of retinopathy.

METHODS

All patients with ESRD undergoing renal transplants underwent comprehensive fundus evaluation including dilated indirect ophthalmoscopy, slit lamp biomicroscopy, and fundus photography. The patients' age, gender, physical parameters (body mass index and blood pressure), duration of diabetes, glycosylated hemoglobin (HbA1c), albumin creatinine ratio, and presence of diabetic peripheral neuropathy (DPN) were determined. Renal histopathology was reviewed, if available.

RESULTS

Five patients with diabetic nephropathy (DN) underwent renal transplant and had no evidence of diabetic retinopathy (DR) or up to two microaneurysms per fundus. All the patients were between 50 and 65 (mean ± standard deviation - 58.6 ± 4.67) years of age. The mean duration of diabetes was 16 ± 2.91 years. All had poor glycemic control with a mean HbA1c of 9.2 ± 0.837%. All had hypertension, macroalbuminuria, and DPN.

CONCLUSION

There is a well-recognized association between retinopathy and nephropathy, in which nephropathy without retinopathy is rare but retinopathy without nephropathy is common. We have identified a subset of patients with kidney disease of sufficient severity to warrant renal transplant but who are protected from retinopathy. It is possible that there is an extreme phenotype of DN patients with unaffected eyes who carry genes protecting against DR.