X-linked juvenile retinoschisis (XLRS): a review of genotype-phenotype relationships

The genetic spectrum and clinical features of X-linked juvenile retinoschisis in Central China

PURPOSE

X-linked juvenile retinoschisis (XLRS) is the most common congenital retinoschisis in rare vitreoretinopathy and causes visual disturbances. The study aimed to explore possible genetic mutations associated with XLRS and assess the clinical characteristics in Chinese families.

METHODS

Seventeen cases and thirty-four eyes of probands and thirty-nine cases and seventy-eight eyes of their guardians were recruited. Peripheral blood DNA was extracted and PCR-amplified for retinal disease second-generation panel sequencing to screen for mutated genes. Pathogenicity was referred to the guidelines of the American College of Medical Genetics and Genomics (ACMG).

RESULTS

A total of 17 male patients were included, with an average age of 9.73 years (range, 5 ~ 27 years). Clinical data indicate typical macular retinoschisis (97.06%), peripheral retinoschisis (46.67%), retinal holes (32.35%). Fifteen mutations (10 missense mutations, 4 shift mutations, and 3 nonsense mutations) of RS1 gene were identified, including 5 novel mutations. In novel mutations, amino acid conservation analysis shows W33, W50, E62, and G70 were highly conserved, and software predicts mutations to be pathogenic. SWISS-MODEL protein prediction software showed protein structural changes in proband 13.

CONCLUSIONS

We have identified and described five novel mutations in the RS1 gene and their corresponding clinical manifestations. These findings not only expand the range of known RS1 mutations and associated clinical phenotypes but also provide a basis for mechanistic studies and diagnosis of XLRS.

Multimodal Retinal Imaging Findings in Two Cousins With VCAN-Related Vitreoretinopathy or Wagner Disease

Wagner disease is a rare, nonsyndromic vitreoretinopathy caused by autosomal dominant variants in the versican (VCAN) gene. It is associated with abnormalities of the vitreoretinal interface that can lead to peripheral traction and retinal detachments, which also occur in other vitreoretinopathies such as X-linked retinoschisis (XLRS), familial exudative vitreoretinopathy (FEVR) and Stickler syndrome. There is variability in the clinical phenotype in Wagner disease potentially due to variants in VCAN gene variants. In this article, we report a family harboring the VCAN c.9265+1G>C variant and describe the clinical and retinal findings in two members. [Ophthalmic Surg Lasers Imaging Retina 2022;53:639-643.].

RS1 gene is a novel prognostic biomarker for lung adenocarcinoma

Background

Although it has a poor prognosis, patients with lung adenocarcinoma (LUAD) have a relatively higher 5‐year survival period. Thus, it is necessary to identify effective prognostic markers to evaluate the effect of early treatment. RS1 gene encodes retinoschisin, a key protein in congenital retinoschisis, while few studies have been reported on the association between RS1 and cancer prognosis.

Methods

We performed bioinformatic analyses based on the data obtained from The Cancer Genome Atlas and Gene Expression Omnibus databases to demonstrate the expression level of RS1 was related to the LUAD prognosis and our findings were verified in‐vitro and clinical samples. Then, we explored the potential mechanism of how RS1 expression influenced the prognosis of LUAD.

Results

Compared with normal tissues, the RS1 expression was significantly lower in tumor tissues. The Multivariate Cox regression model showed that RS1 could be used as an independent prognostic indicator. Furthermore, we found significant differences in immune cell infiltration between RS1 high and low expression groups, and the proteasome pathway was found enriched in RS1 low expression samples.

Conclusion

In conclusion, our study suggests that RS1 is a novel prognostic biomarker for LUAD. Differences in immune cell infiltration and signaling pathways may contribute to the poor prognosis of LUAD caused by low RS1 expression.

Compendium of causative genes and their encoded proteins for common monogenic disorders

A compendium is presented of inherited monogenic disorders that have a prevalence of >1:20,000 in the human population, along with their causative genes and encoded proteins. "Simple" monogenic diseases are those for which the clinical features are caused by mutations impacting a single gene, usually in a manner that alters the sequence of the encoded protein. Of course, for a given "monogenic disorder", there is sometimes more than one potential disease gene, mutations in any one of which is sufficient to cause phenotypes of that disorder. Disease-causing mutations for monogenic disorders are usually passed on from generation to generation in a Mendelian fashion, and originate from spontaneous (de novo) germline founder mutations. In the past monogenic disorders have often been written off as targets for drug discovery because they sometimes are assumed to be rare disorders, for which the meager projected financial payoff of drug discovery and development has discouraged investment. However, not all monogenic diseases are rare. Here, we report that that currently available data identifies 72 disorders with a prevalence of at least 1 in 20,000 humans. For each, we tabulate the gene(s) for which mutations cause the spectrum of phenotypes associated with that disorder. We also identify the gene and protein that most commonly causes each disease. 34 of these disorders are caused exclusively by mutations in only a single gene and encoded protein.

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.

X-Linked Retinoschisis: Novel Clinical Observations and Genetic Spectrum in 340 Patients

PURPOSE

To describe the natural course, phenotype, and genotype of patients with X-linked retinoschisis (XLRS).

DESIGN

Retrospective cohort study.

PARTICIPANTS

Three hundred forty patients with XLRS from 178 presumably unrelated families.

METHODS

This multicenter, retrospective cohort study reviewed medical records of patients with XLRS for medical history, symptoms, visual acuity (VA), ophthalmoscopy, full-field electroretinography, and retinal imaging (fundus photography, spectral-domain [SD] OCT, fundus autofluorescence).

MAIN OUTCOME MEASURES

Age at onset, age at diagnosis, severity of visual impairment, annual visual decline, and electroretinography and imaging findings.

RESULTS

Three hundred forty patients were included with a mean follow-up time of 13.2 years (range, 0.1-50.1 years). The median ages to reach mild visual impairment and low vision were 12 and 25 years, respectively. Severe visual impairment and blindness were observed predominantly in patients older than 40 years, with a predicted prevalence of 35% and 25%, respectively, at 60 years of age. The VA increased slightly during the first 2 decades of life and subsequently transitioned into an average annual decline of 0.44% (P < 0.001). No significant difference was found in decline of VA between variants that were predicted to be severe and mild (P = 0.239). The integrity of the ellipsoid zone (EZ) as well as the photoreceptor outer segment (PROS) length in the fovea on SD OCT correlated significantly with VA (Spearman's ρ = -0.759 [P < 0.001] and -0.592 [P = 0.012], respectively). Fifty-three different RS1 variants were found. The most common variants were the founder variant c.214G→A (p.(Glu72Lys)) (101 patients [38.7%]) and a deletion of exon 3 (38 patients [14.6%]).

CONCLUSIONS

Large variabilities in phenotype and natural course of XLRS were seen in this study. In most patients, XLRS showed a slow deterioration starting in the second decade of life, suggesting an optimal window of opportunity for treatment within the first 3 decades of life. The integrity of EZ as well as the PROS length on SD OCT may be important in choosing optimal candidates for treatment and as potential structural end points in future therapeutic studies. No clear genotype-phenotype correlation was found.

Genetic Rescue of X-Linked Retinoschisis Mouse (Rs1-/y) Retina Induces Quiescence of the Retinal Microglial Inflammatory State Following AAV8-RS1 Gene Transfer and Identifies Gene Networks Underlying Retinal Recovery

To understand RS1 gene interaction networks in the X-linked retinoschisis (XLRS) mouse retina (Rs1^-/y), we analyzed the transcriptome by RNA sequencing before and after in vivo expression of exogenous retinoschisin (RS1) gene delivered by AAV8. RS1 is a secreted cell adhesion protein that is critical for maintaining structural lamination and synaptic integrity of the neural retina. RS1 loss-of-function mutations cause XLRS disease in young boys and men, with splitting ("schisis") of retinal layers and synaptic dysfunction that cause progressive vision loss with age. Analysis of differential gene expression profiles and pathway enrichment analysis of Rs1-KO (Rs1^-/y) retina identified cell surface receptor signaling and positive regulation of cell adhesion as potential RS1 gene interaction networks. Most importantly, it also showed massive dysregulation of immune response genes at early age, with characteristics of a microglia-driven proinflammatory state. Delivery of AAV8-RS1 primed the Rs1-KO retina toward structural and functional recovery. The disease transcriptome transitioned toward a recovery phase with upregulation of genes implicated in wound healing, anatomical structure (camera type eye) development, metabolic pathways, and collagen IV networks that provide mechanical stability to basement membrane. AAV8-RS1 expression also attenuated the microglia gene signatures to low levels toward immune quiescence. This study is among the first to identify RS1 gene interaction networks that underlie retinal structural and functional recovery after RS1 gene therapy. Significantly, it also shows that providing wild-type RS1 gene function caused the retina immune status to transition from a degenerative inflammatory phenotype toward immune quiescence, even though the transgene is not directly linked to microglia function. This study indicates that inhibition of microglial proinflammatory responses is an integral part of therapeutic rescue in XLRS gene therapy, and gene therapy might realize its full potential if delivered before microglia activation and photoreceptor cell death. Clinical Trials. gov Identifier NTC 02317887.

Outcome measures in juvenile X-linked retinoschisis: A systematic review

X-linked retinoschisis (XLRS) is a leading cause of hereditary juvenile macular degeneration in males resulting in significant vision impairment. Outcome measures to monitor disease progression or therapeutic interventions have evolved with technology. A systematic review was undertaken to evaluate outcome measures for XLRS. Inclusion criteria were all publications examining outcome measures for natural history studies or following an interventional approach for patients with XLRS. Studies which did not present follow-up data were excluded. We searched medical databases including CENTRAL, Ovid Medline, pre-Medline and ahead of Print up to February 2019. Two authors independently assessed the risk of bias. Twelve studies meet the inclusion criteria with four prospective and eight retrospective case series. Five series were natural history observational studies and seven were interventional series using either topical or systemic carbonic anhydrase inhibitors. Visual acuity (VA) declined very slowly in the natural history studies equivalent to 0.22-0.5 letters per year. Five of the six interventional studies showed an improvement in VA and four a reduction in spectral domain optical coherence tomography (SD-OCT) parameters for central macular thickness (CMT). The full-field electroretinogram identified the 30-Hz latency as a further parameter to monitor function. VA was the measure most likely to show a statistically significant outcome. How functionally meaningful this is, requires further evaluation. CMT SD-OCT outcomes are variable depending on cystic changes. More refined measures are required to better correlate structure with function.

Findings from a Genotyping Study of Over 1000 People with Inherited Retinal Disorders in Ireland

The Irish national registry for inherited retinal degenerations (Target 5000) is a clinical and scientific program to identify individuals in Ireland with inherited retinal disorders and to attempt to ascertain the genetic cause underlying the disease pathology. Potential participants first undergo a clinical assessment, which includes clinical history and analysis with multimodal retinal imaging, electrophysiology, and visual field testing. If suitable for recruitment, a sample is taken and used for genetic analysis. Genetic analysis is conducted by use of a retinal gene panel target capture sequencing approach. With over 1000 participants from 710 pedigrees now screened, there is a positive candidate variant detection rate of approximately 70% (495/710). Where an autosomal recessive inheritance pattern is observed, an additional 9% (64/710) of probands have tested positive for a single candidate variant. Many novel variants have also been detected as part of this endeavor. The target capture approach is an economic and effective means of screening patients with inherited retinal disorders. Despite the advances in sequencing technology and the ever-decreasing associated processing costs, target capture remains an attractive option as the data produced is easily processed, analyzed, and stored compared to more comprehensive methods. However, with decreasing costs of whole genome and whole exome sequencing, the focus will likely move towards these methods for more comprehensive data generation.

Molecular characterization of a rare phenotype of X-linked retinoschisis with angle-closure glaucoma

A 11-year-old boy presented with complaints of blurred vision and on evaluation was found to have X-linked retinoschisis (XLRS) with angle-closure glaucoma. Clinical and genetic evaluation of first-degree family members was done. His brother had a milder form of XLRS with shallow anterior chamber. Topical dorzolamide 2% and timolol 0.5% were used to control intraocular pressure. Genetic analysis revealed a novel three base pair deleterious mutation (c. 375_377 del AGA) in exon-5 of the RS1 gene in three members of the family.

Optical Coherence Tomography Angiography Findings in X-Linked Retinoschisis

BACKGROUND AND OBJECTIVE

The aim of the study was to determine optical coherence tomography angiography (OCTA) findings and to identify mutations in the RS1 gene in a three-generation family with X-linked juvenile retinoschisis (XLRS).

PATIENTS AND METHODS

Clinical and genetic assessments were performed in 12 family members. OCTA was performed at baseline (12 members including cases and carriers) and after acetazolamide administration (three cases). Twenty healthy subjects (20 eyes, controls) were chosen for comparison. Molecular genetic analysis of the RS1 gene was performed in all family members.

RESULTS

Deep capillary plexus density was reduced in cases compared with controls (P < .01) and was negatively related with retinal thickness (P < .05). After treatment, retinal thickness decreased (P < .05) and deep capillary plexus density increased (P < .05) in cases. In three cases and in four carriers, p.Arg197 His mutation was found.

CONCLUSION

OCTA shows reduced macular deep vessel density in patients with XLRS probably related to vessel displacement and disruption due to schitic cysts. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:e20-e31.].

Swept-source and optical coherence tomography angiography in patients with X-linked retinoschisis

PurposeTo explore the structural features of juvenile X-linked retinoschisis (XLRS) using swept-source-optical coherence tomography (SS-OCT) and optical coherence tomography angiography (OCT-A).DesignRetrospective, observational cross-sectional study.Patients and methodsNine patients (18 eyes) diagnosed with juvenile XLRS were included. SS-OCT and OCT-A were used to evaluate the characteristics of the inner/outer retina and the choroid.ResultsSS-OCT showed that the inner nuclear layer (INL) was the most commonly affected area (16/18 eyes; 89%). No significant differences in central macular thickness (CMT) or subfield choroidal thickness (SFCT) were evidenced between eyes (CMT: 364 μm in the right eye vs 320 μm in the left eye; SFCT: 305 vs 307 μm; P=0.895). Best-corrected visual acuity (BCVA) did not correlate with CMT (rs= -0.19; P=0.445) or SFCT (rs=0.06; P=0.795). BCVA was significantly correlated with the following defects: outer plexiform layer (OPL; rs=0.50; P=0.036); external limiting membrane (ELM; rs=0.65; P=0.003); ellipsoid portion of inner segment (EPIS; rs=0.67; P=0.002); and the cone outer segment tips (COST; rs=0.69; P=0.001). Schisis at the INL revealed a spoke-like pattern in the foveal region and a reticular pattern in the parafoveal region on en-face imaging. In cases in which the schisis affected the OPL, multiple polygonal hyporeflective cavities were observed in the foveal region.ConclusionsThe hyporeflective spaces on SS-OCT were primarily located at the INL and OPL. BCVA did not correlate with CMT or SFCT; however, ELM, EPIS, and COST defects were significantly correlated with worse BCVA. There was a positive correlation between age and SFCT.

Optical Coherence Tomography Evolution in a Case of X-Linked Juvenile Retinoschisis: 15 Years of Follow-Up

PURPOSE

We present the evolution of X-linked juvenile retinoschisis (XLRS) in a male patient using optical coherence tomography (OCT) with a long-term follow-up time of 15 years.

CASE DESCRIPTION

A 10-year-old male patient presented at the Medical Retina Department of our hospital complaining for blurred vision in both eyes. At the initial presentation in 2001, his best corrected visual acuity (BCVA) was 6/12 in both eyes on the Snellen chart. Based on clinical and OCT findings, the diagnosis of XLRS was made, and it was confirmed by genetic testing. No treatment was performed, but the patient was regularly examined. His BCVA and OCT findings remained relatively stable from 2001 to 2012, when BCVA decreased to 6/18 and 6/24 in the right and left eye, respectively. In 2016, his BCVA was 6/24 and 6/36 in right and left eye, respectively, while OCT depicted significant macular thinning, accompanied by irregularities of the foveal contour in both eyes.

CONCLUSION

Patients with XLRS should be monitored regularly to evaluate the progression of the disease and manage the potential complications.

Design and Validation of a New MLPA-Based Assay for the Detection of RS1 Gene Deletions and Application in a Large Family with X-Linked Juvenile Retinoschisis

AIMS

X-linked juvenile retinoschisis (XLRS) is a severe ocular disorder that can evolve to blindness. More than 200 different disease-causing mutations have been reported in the RS1 gene and approximately 10% of these are deletions. Since transmission is X-linked, males are always affected and females are usually carriers. The identification of female carriers is always important and poses a technical challenge. Therefore, we sought to develop a multiplex ligation dependent probe amplification (MLPA)-based method to identify deletions or duplications in this gene. We then used our assay to study a large XLRS family.

METHODS

We designed six probes specific for each RS1 exon and then optimized and validated our method using control samples with known gene deletions. In the XLRS family, RS1 gene copy number variation was assessed by "home-made" MLPA analysis and by single nucleotide polymorphism (SNP) array analysis using the CytoScan HD Array. Direct sequencing was used for deletion breakpoint mapping.

RESULTS

Our assay detected all deletions in control samples. All affected males of the family were positive for a deletion of exon 2 of the RS1 gene (RS1:NM_000330:c.53-?_78+?del). Carrier females were also identified.

CONCLUSION

Our method is easily replicated, reliable, and inexpensive and allows female carriers to be detected. This is the first report of deep characterization of a whole exon deletion in the RS1 gene.

Current Understanding of the Genetic Architecture of Rhegmatogenous Retinal Detachment

Rhegmatogenous retinal detachment (RRD) is a common and potentially blinding surgical retinal disease. While the precise molecular mechanisms leading to RRD are poorly understood, there is an increasing body of literature supporting the role of heritable factors in the pathogenesis of the condition. Much work has been undertaken investigating genes important in syndromic forms of RRD (e.g., Stickler, Wagner Syndrome, etc.) and research pertaining to genetic investigations of idiopathic or non-syndromic RRD has also recently been reported. To date, at least 12 genetic loci have been implicated in the development of syndromes of which RRD is a feature. A recent GWAS identified five loci implicated in the development of idiopathic RRD.This article provides an overview of the genetic mechanisms of both syndromic and idiopathic RRD. The genetics of predisposing conditions, such as myopia and lattice degeneration, are also discussed.