Generation of a gene-corrected isogenic iPSC cell line from an X-linked retinoschisis patient with a hemizygous mutation c.304C > T (p.R102W) in RS1 gene.

X-linked retinoschisis (XLRS) is one of the most common retinal genetic diseases with progressive visual impairment in childhood affecting males. It is manifested with macular and/or peripheral schisis in neural retinas with no effective treatment. Previously, we successfully generated a human-induced pluripotent stem cell (iPSC) line from an XLRS patient carrying the hemizygous RS1 c. 304C > T (p.R102W) mutation. Here, we corrected the c.304C > T mutation in the RS1 gene using CRISPR/Cas9 technology to generate an isogenic control. This cell line is valuable for the study of XLRS.

Identification and molecular characterization of two recurrent missense mutations in the RS1 gene in two families with X-linked retinoschisis from North India.

X-linked retinoschisis (XLR) is a rare medical condition that involves in the splitting of neurosensory layers and the impairment of vision in the retina. In majority of the XLR cases, pathogenic variants in Retinoschisin 1 (RS1) gene have been implicated in males with an early age of onset during early childhood. In the present study, we have recruited two North Indian families having multiple affected male members, who were diagnosed with XLR. The entire protein-coding region of RS1 was screened by PCR-Sanger sequencing and two recurrent pathogenic variants (p.I81N and p.R102Q) were unraveled. The in vitro study of these variants demonstrated the aggregation of mutant RS1 within the endoplasmic reticulum. Furthermore, mutant forms of this protein showed significant intracellular retention, which was evident by the absence of retinoschisin protein fractions in the extracellular media. These inferences were also supported by extensive bioinformatics analysis of the mutants, which showed dramatic conformational changes in the local structure of retinoschisin. Thus, our study suggests that the identified pathogenic variants interfere with proper protein folding, leading to anomalous structural changes ultimately resulting in intracellular retention of retinoschisin within the retina.

Advances in understanding the molecular structure of retinoschisin while questions remain of biological function.

Retinoschisin (RS1) is a secreted protein that is essential for maintaining integrity of the retina. Numerous mutations in RS1 cause X-linked retinoschisis (XLRS), a progressive degeneration of the retina that leads to vision loss in young males. A key manifestation of XLRS is the formation of cavities (cysts) in the retina and separation of the layers (schisis), disrupting synaptic transmission. There are currently no approved treatments for patients with XLRS. Strategies using adeno-associated viral (AAV) vectors to deliver functional copies of RS1 as a form of gene augmentation therapy, are under clinical evaluation. To improve therapeutic strategies for treating XLRS, it is critical to better understand the secretion of RS1 and its molecular function. Immunofluorescence and immunoelectron microscopy show that RS1 is located on the surfaces of the photoreceptor inner segments and bipolar cells. Sequence homology indicates a discoidin domain fold, similar to many other proteins with demonstrated adhesion functions. Recent structural studies revealed the tertiary structure of RS1 as two back-to-back octameric rings, each cross-linked by disulfides. The observation of higher order structures in vitro suggests the formation of an adhesive matrix spanning the distance between cells (∼100 nm). Several studies indicated that RS1 readily binds to other proteins such as the sodium-potassium ATPase (NaK-ATPase) and extracellular matrix proteins. Alternatively, RS1 may influence fluid regulation via interaction with membrane proteins such as the NaK-ATPase, largely inferred from the use of carbonic anhydrase inhibitors to shrink the typical intra-retinal cysts in XLRS. We discuss these models in light of RS1 structure and address the difficulty in understanding the function of RS1.

XLRS Rat with Rs1-/Y Exon-1-Del Shows Failure of Early Postnatal Outer Retina Development.

We generated a Long Evans transgenic rat with targeted deletion of the whole Rs1 exon-1 and evaluated the pathological retinal phenotype of this Rs1-/Y rat model of X-linked retinoschisis (XLRS). The Rs1-/Y rat exhibited very early onset and rapidly progressive photoreceptor degeneration. The outer limiting membrane (OLM) was disrupted and discontinuous by post-natal day (P15) and allowed photoreceptor nuclei to dislocate from the outer nuclear layers (ONL) into the sub-retinal side of the OLM. Dark-adapted electroretinogram (ERG) a-wave and b-wave amplitudes were considerably reduced to only 20-25% of WT by P17. Microglia and Müller glial showed cell marker activation by P7. Intravitreal application of AAV8-RS1 at P5-6 induced RS1 expression by P15 and rescued the inner nuclear layer (INL) and outer plexiform layer (OPL) cavity formation otherwise present at P15, and the outer-retinal structure was less disrupted. This Rs1-/Y exon-1-del rat model displays substantially faster rod cell loss compared to the exon-1-del Rs1-KO mouse. Most unexpected was the rapid appearance of schisis cavities between P7 and P15, and then cavities rapidly disappeared by P21/P30. The rat model provides clues on the molecular and cellular mechanisms underlying XLRS pathology in this model and points to a substantial and early changes to normal retinal development.

Targeted Expression of Retinoschisin by Retinal Bipolar Cells in XLRS Promotes Resolution of Retinoschisis Cysts Sans RS1 From Photoreceptors.

Purpose: Loss of retinoschisin (RS1) function underlies X-linked retinoschisis (XLRS) pathology. In the retina, both photoreceptor inner segments and bipolar cells express RS1. However, the loss of RS1 function causes schisis primarily in the inner retina. To understand these cell type-specific phenotypes, we decoupled RS1 effects in bipolar cells from that in photoreceptors. Methods: Bipolar cell transgene RS1 expression was achieved using two inner retina-specific promoters: (1) a minimal promoter engineered from glutamate receptor, metabotropic glutamate receptor 6 gene (mini-mGluR6/ Grm6) and (2) MiniPromoter (Ple155). Adeno-associated virus vectors encoding RS1 gene under either the mini-mGluR6 or Ple-155 promoter were delivered to the XLRS mouse retina through intravitreal or subretinal injection on postnatal day 14. Retinal structure and function were assessed 5 weeks later: immunohistochemistry for morphological characterization, optical coherence tomography and electroretinography (ERG) for structural and functional evaluation. Results: Immunohistochemical analysis of RS1expression showed that expression with the MiniPromoter (Ple155) was heavily enriched in bipolar cells. Despite variations in vector penetrance and gene transfer efficiency across the injected retinas, those retinal areas with robust bipolar cell RS1 expression showed tightly packed bipolar cells with fewer cavities and marked improvement in inner retinal structure and synaptic function as judged by optical coherence tomography and electroretinography, respectively. Conclusions: These results demonstrate that RS1 gene expression primarily in bipolar cells of the XLRS mouse retina, independent of photoreceptor expression, can ameliorate retinoschisis structural pathology and provide further evidence of RS1 role in cell adhesion.

Retinoschisin and novel Na/K-ATPase interaction partners Kv2.1 and Kv8.2 define a growing protein complex at the inner segments of mammalian photoreceptors.

The RS1 gene on Xp 22.13 encodes retinoschisin which is known to directly interact with the retinal Na/K-ATPase at the photoreceptor inner segments. Pathologic mutations in RS1 cause X-linked juvenile retinoschisis (XLRS), a hereditary retinal dystrophy in young males. To further delineate the retinoschisin-Na/K-ATPase complex, co-immunoprecipitation was performed with porcine and murine retinal lysates targeting the ATP1A3 subunit. This identified the voltage-gated potassium (Kv) channel subunits Kv2.1 and Kv8.2 as direct interaction partners of the retinal Na/K-ATPase. Colocalization of the individual components of the complex was demonstrated at the membrane of photoreceptor inner segments. We further show that retinoschisin-deficiency, a frequent consequence of molecular pathology in XLRS, causes mislocalization of the macromolecular complex during postnatal retinal development with a simultaneous reduction of Kv2.1 and Kv8.2 protein expression, while the level of retinal Na/K-ATPase expression remains unaffected. Patch-clamp analysis revealed no effect of retinoschisin-deficiency on Kv channel mediated potassium ion currents in vitro. Together, our data suggest that Kv2.1 and Kv8.2 together with retinoschisin and the retinal Na/K-ATPase are integral parts of a macromolecular complex at the photoreceptor inner segments. Defective compartmentalization of this complex due to retinoschisin-deficiency may be a crucial step in initial XLRS pathogenesis.

Clinical manifestation and current therapeutics in X-juvenile retinoschisis.

X-linked juvenile retinoschisis (XLRS) is one of the common early-onset hereditary retinal degenerative diseases in men. The common symptoms of XLRS range from mild to severe central vision loss and radial stripes created by the fovea, the division of the inner layer of the retina in the peripheral retina and the significant decrease in b-wave amplitude (ERG). Retinoschisin, the 224-amino-acid protein product of the retinoschisis 1 (RS1) gene, contains a discoid domain as the primary structural unit, an N-terminal cleavable signal sequence, and an oligomerization-area component. Retinoschisin is a homo-octamer complex with disulfide links that are released by retinal cells. It helps preserve the retina's integrity by binding to the surface of photoreceptors and bipolar cells. As a recessive genetic disease, XLRS was usually treated by prescribing low vision aids in most clinical cases. A gene replacement therapy based on adeno-associated virus vectors was initiated and showed a breakthrough in treating XLRS in 2014. Understanding the revolution of gene therapy for treating XLRS may accelerate its development and make this gene therapy the template for developing therapeutics against other inherited retinal diseases.

Immune function in X-linked retinoschisis subjects in an AAV8-RS1 phase I/IIa gene therapy trial.

This study explored systemic immune changes in 11 subjects with X-linked retinoschisis (XLRS) in a phase I/IIa adeno-associated virus 8 (AAV8)-RS1 gene therapy trial (ClinicalTrials.gov: NCT02317887). Immune cell proportions and serum analytes were compared to 12 healthy male controls. At pre-dosing baseline the mean CD4/CD8 ratio of XLRS subjects was elevated. CD11c+ myeloid dendritic cells (DCs) and the serum epidermal growth factor (EGF) level were decreased, while CD123+ plasmacytoid DCs and serum interferon (IFN)-γ and tumor necrosis factor (TNF)-α were increased, indicating that the XLRS baseline immune status differs from that of controls. XLRS samples 14 days after AAV8-RS1 administration were compared with the XLRS baseline. Frequency of CD11b+CD11c+ DCc was decreased in 8 of 11 XLRS subjects across all vector doses (1e9-3e11 vector genomes [vg]/eye). CD8+human leukocyte antigen-DR isotype (HLA-DR)+ cytotoxic T cells and CD68+CD80+ macrophages were upregulated in 10 of 11 XLRS subjects, along with increased serum granzyme B in 8 of 11 XLRS subjects and elevated IFN-γ in 9 of 11 XLRS subjects. The six XLRS subjects with ocular inflammation after vector application gave a modestly positive correlation of inflammation score to their respective baseline CD4/CD8 ratios. This exploratory study indicates that XLRS subjects may exhibit a proinflammatory, baseline immune phenotype, and that intravitreal dosing with AAV8-RS1 leads to systemic immune activation with an increase of activated lymphocytes, macrophages, and proinflammatory cytokines.

Engineered FnCas12a with enhanced activity through directional evolution in human cells.

Clustered regularly interspaced short palindromic repeat-Cas12a has been harnessed to manipulate the human genome; however, low cleavage efficiency and stringent protospacer adjacent motif hinder the use of Cas12a-based therapy and applications. Here, we have described a directional evolving and screening system in human cells to identify novel FnCas12a variants with high activity. By using this system, we identified IV-79 (enhanced activity FnCas12a, eaFnCas12a), which possessed higher DNA cleavage activity than WT FnCas12a. Furthermore, to widen the target selection spectrum, eaFnCas12a was engineered through site-directed mutagenesis. eaFnCas12a and one engineered variant (eaFnCas12a-RR), used for correcting human RS1 mutation responsible for X-linked retinoschisis, had a 3.28- to 4.04-fold improved activity compared with WT. Collectively, eaFnCas12a and its engineered variants can be used for genome-editing applications that requires high activity.

Carbonic anhydrase inhibition in X-linked retinoschisis: An eye on the photoreceptors.

The retinoschisin protein is encoded on the short arm of the X-chromosome by RS1, is expressed abundantly in photoreceptor inner segments and in bipolar cells, and is secreted as an octamer that maintains the structural integrity of the retina. Mutations in RS1 lead to X-linked retinoschisis (XLRS), a disease characterized by the formation of cystic spaces between boys' retinal layers that frequently present in ophthalmoscopy as a "spoke-wheel" pattern on their maculae and by progressively worsening visual acuity (VA). There is no proven therapy for XLRS, but there is mixed evidence that carbonic anhydrase inhibitors (CAIs) produce multiple beneficial effects, including improved VA and decreased volume of cystic spaces. Consequently, linear mixed-effects (LME) models were used to evaluate the effects of CAI therapy on VA and central retinal thickness (CRT, a proxy for cystic cavity volume) in a review of 19 patients' records. The mechanism of action of action of CAIs is unclear but, given that misplaced retinoschisin might accumulate in the photoreceptors, it is possible-perhaps even likely-that CAIs act to benefit the function of photoreceptors and the neighboring retinal pigment epithelium by acidification of the extracellular milieu; patients on CAIs have among the most robust photoreceptor responses. Therefore, a small subset of five subjects were recruited for imaging on a custom multimodal adaptive optics retinal imager for inspection of their parafoveal cone photoreceptors. Those cones that were visible, which numbered far fewer than in controls, were enlarged, consistent with the retinoschisin accumulation hypothesis. Results of the LME modeling found that there is an initial benefit to both VA and CRT in CAI therapy, but these wane, in both cases, after roughly two years. That said, even a short beneficial effect of CAIs on the volume of the cystic spaces may give CAI therapy an important role as pretreatment before (or immediately following) administration of gene therapy.

Retinoschisin and Cardiac Glycoside Crosstalk at the Retinal Na/K-ATPase.

Purpose: Mutations in the RS1 gene, which encodes retinoschisin, cause X-linked juvenile retinoschisis, a retinal dystrophy in males. Retinoschisin specifically interacts with the retinal sodium-potassium adenosine triphosphatase (Na/K-ATPase), a transmembrane ion pump. Na/K-ATPases also bind cardiac glycosides, which control the activity of the pump and have been linked to disturbances in retinal homeostasis. In this study, we investigated the crosstalk between retinoschisin and cardiac glycosides at the retinal Na/K-ATPase and the consequences of this interplay on retinal integrity. Methods: The effect of cardiac glycosides (ouabain and digoxin) on the binding of retinoschisin to the retinal Na/K-ATPase was investigated via western blot and immunocytochemistry. Also, the influence of retinoschisin on the binding of cardiac glycosides was analyzed via enzymatic assays, which quantified cardiac glycoside-sensitive Na/K-ATPase pump activity. Moreover, retinoschisin-dependent binding of tritium-labeled ouabain to the Na/K-ATPase was determined. Finally, a reciprocal effect of retinoschisin and cardiac glycosides on Na/K-ATPase localization and photoreceptor degeneration was addressed using immunohistochemistry in retinoschisin-deficient murine retinal explants. Results: Cardiac glycosides displaced retinoschisin from the retinal Na/K-ATPase; however, retinoschisin did not affect cardiac glycoside binding. Notably, cardiac glycosides reduced the capacity of retinoschisin to regulate Na/K-ATPase localization and to protect against photoreceptor degeneration. Conclusions: Our findings reveal opposing effects of retinoschisin and cardiac glycosides on retinal Na/K-ATPase binding and on retinal integrity, suggesting that a fine-tuned interplay between both components is required to maintain retinal homeostasis. This observation provides new insight into the mechanisms underlying the pathological effects of cardiac glycoside treatment on retinal integrity.

Effect of light and diurnal variation on macular thickness in X-linked retinoschisis: a case series.

BACKGROUND: Diurnal variations in foveal thickness have been reported in several ocular pathologies including X-linked retinoschisis (XLRS), but its underlying mechanism is poorly understood. Rods are active under scotopic conditions with high metabolic demand, and its decrease may have positive effect on metabolic activity and macular thickness. The purpose of this study is to evaluate whether exposure to light and diurnal variation influence macular thickness in XLRS patients. METHODS: Five patients with clinical suspicion of XLRS underwent RS1 gene sequencing and optical coherence tomography measurements at three consecutive times: morning following sleep in a dark room, morning following sleep in an illuminated room, and late afternoon following sleep in an illuminated room. Central macular thickness (CMT) was compared between measurements, and molecular analysis was performed. RESULTS: Five RS1 mutations were identified: p.Gly140Arg, p.Arg141Cys, p.Gly109Glu, p.Pro193Leu, and p.Arg200His in patients 1-5, respectively. Two patients (4-5) had atrophied macula and were excluded from macular thickness variation analysis. A significant decrease in CMT between morning and afternoon measurements was observed in all patients (1-3: mean: 455.0 ± 32 µm to 342.17 ± 39 µm, 25%). Morning measurements following sleep in an illuminated room show a CMT reduction in all eyes of all patients with a mean reduction of 113 µm (mean: 547.17 ± 105 µm to 455.0 ± 32 µm, 17%). CONCLUSIONS: Among XLRS patients, CMT decreased at the afternoon compared to the morning of the same day and may be reduced following sleep in an illuminated room. These results help shed light on the pathophysiologic process underlying intraretinal fluid accumulation involved with the disease.

Establishment of CSUASOi001-A, a non-integrated induced pluripotent stem cell line from urine-derived cells of a Chinese patient carrying RS1 gene mutation.

X-linked juvenile retinoschisis (XLRS) is one of the most severely affected genetic causes of irreversible retinal degeneration diseases in young males, especially school-age boys. Here, we generated induced pluripotent stem cells (iPSCs) from a Chinese 11-year-old male with clinically diagnosed XLRS. Urine sample was collected with appropriate cooperation, then isolated cells were expanded for subsequent reprogramming procedure using integration-free Sendai virus. The newly derived CSUASOi001-A iPS cell line harboring the c.304C > T mutation in the RS1 gene (p.R102W) provides a useful resource to investigate pathogenic mechanisms in XLRS.

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

Morphologic, Biomechanical, and Compositional Features of the Internal Limiting Membrane in Pathologic Myopic Foveoschisis.

Purpose: To investigate alterations in the morphologic, compositional, and biomechanical properties of the internal limiting membrane (ILM) in pathologic myopic foveoschisis (MF) eyes. Methods: ILM specimens were peeled from 61 eyes with MF and 56 eyes with stage III/IV idiopathic macular hole (IMH) as a control. Samples were analyzed for transmission electron microscopy (TEM), scanning electron microscopy, immunofluorescence, Western blotting, and atomic force microscopy. ILM characteristics were compared between the two groups. Results: TEM findings revealed that thickness of the MF ILMs significantly decreased compared with that of IMH ILMs (0.753 ± 0.215 vs. 1.894 ± 0.247 µm; P < 0.0001). The vitreal side stiffness of the MF ILMs was markedly higher than that of the IMH ILMs (3.520 ± 0.803 vs. 0.879 ± 0.230 MPa, P < 0.0001). Comparing with the IMH group, collagen IV exhibited decreased concentration and different immunofluorescence distribution in ILMs of MF eyes, so also protein α3 (IV), α4 (IV), and α5 (IV). The immunofluorescence staining results showed that astrocytes were observed in none of the IMH eyes and in 12 of 16 MF eyes (75%, P < 0.0001). Conclusions: These alterations in the MF ILMs appear to be associated with Müller cell and astrocyte reactive gliosis. The present findings contribute to a more in-depth understanding of the pathogenesis of MF.

Retinal AAV8-RS1 Gene Therapy for X-Linked Retinoschisis: Initial Findings from a Phase I/IIa Trial by Intravitreal Delivery.

This study evaluated the safety and tolerability of ocular RS1 adeno-associated virus (AAV8-RS1) gene augmentation therapy to the retina of participants with X-linked retinoschisis (XLRS). XLRS is a monogenic trait affecting only males, caused by mutations in the RS1 gene. Retinoschisin protein is secreted principally in the outer retina, and its absence results in retinal cavities, synaptic dysfunction, reduced visual acuity, and susceptibility to retinal detachment. This phase I/IIa single-center, prospective, open-label, three-dose-escalation clinical trial administered vector to nine participants with pathogenic RS1 mutations. The eye of each participant with worse acuity (≤63 letters; Snellen 20/63) received the AAV8-RS1 gene vector by intravitreal injection. Three participants were assigned to each of three dosage groups: 1e9 vector genomes (vg)/eye, 1e10 vg/eye, and 1e11 vg/eye. The investigational product was generally well tolerated in all but one individual. Ocular events included dose-related inflammation that resolved with topical and oral corticosteroids. Systemic antibodies against AAV8 increased in a dose-related fashion, but no antibodies against RS1 were observed. Retinal cavities closed transiently in one participant. Additional doses and immunosuppressive regimens are being explored to pursue evidence of safety and efficacy (ClinicalTrials.gov: NCT02317887).

Pathomechanism of mutated and secreted retinoschisin in X-linked juvenile retinoschisis.

Mutations in the RS1 gene encoding retinoschisin cause X-linked juvenile retinoschisis (XLRS), a hereditary retinal dystrophy in males. While most of the XLRS associated mutations strongly interfere with cellular secretion, this is not true for mutants RS1-F108C, -R141G, -R141H, -R182C, -H207Q and -R209H. Native retinoschisin builds double-octamers and binds to retinal membranes, interacting with the retinal Na/K-ATPase. Functionally, it regulates MAP kinase signaling and Na/K-ATPase localization, and hampers photoreceptor degeneration. In this study, we investigated the capacity of the retinoschisin mutants still secreted extracellularly to fulfil these tasks. We addressed secretion and oligomerization of the heterologously expressed mutants as well as their binding to recombinant retinal Na/K-ATPases and murine retinoschisin-deficient (Rs1h-/Y) retinal and non-retinal explants. This has refined the categorization of secreted retinoschisin mutants: (i) no octamerization, unspecific membrane binding (RS1-F108C and -R182C), (ii) double-octamerization but no membrane binding (RS1-R141H), and (iii) double-octamerization and unspecific membrane binding (RS1-R141G, -H207Q, and -R209H). Notably, selected mutants of all categories (RS1-F108C, -R141H, and -R209H) failed to regulate retinal MAP kinase signaling and Na/K-ATPase localization in Rs1h-/Y retinal explants, and could not attenuate photoreceptor degeneration. Bioinformatic modeling of the secreted mutants depicted prominent alterations in the spatial and temporal conformation of a substructure called "spike 3" and its vicinity, implying a crucial role of this substructure for binding capacity and specificity. Taken together, our data point to a pathomechanism for secreted retinoschisin mutants, specifically to disturbances of the retinoschisin interface accompanied by unphysiological membrane interactions and impaired regulatory functions.

Understanding variable disease severity in X-linked retinoschisis: Does RS1 secretory mechanism determine disease severity?

X-linked retinoschisis (XLRS) is a retinal degenerative disorder caused by mutations in RS1 gene leading to splitting of retinal layers (schisis) which impairs visual signal processing. Retinoschisin (RS1) is an adhesive protein which is secreted predominantly by the photoreceptors and bipolar cells as a double-octameric complex. In general, XLRS patients show wide clinical heterogeneity, presenting practical challenges in disease management. Though researchers have attempted various approaches to offer an explanation for clinical heterogeneity, the molecular basis has not been understood yet. Therefore, this study aims at establishing a link between the phenotype and genotype based on the molecular mechanism exerted by the mutations. Twenty seven XLRS patients were enrolled, of which seven harboured novel mutations. The mutant constructs were genetically engineered and their secretion profiles were studied by in vitro cell culture experiments. Based on the secretory profile, the patients were categorized as either secreted or non-secreted group. Various clinical parameters such as visual acuity, location of schisis, foveal thickness and ERG parameters were compared between the two groups and control. Although the two groups showed severe disease phenotype in comparison with control, there was no significant difference between the two XLRS groups. However, the secreted group exhibited relatively severe disease indications. On the other hand molecular analysis suggests that most of the RS1 mutations result in intracellular retention of retinoschisin. Hence, clinical parameters of patients with non-secreted profile were analyzed which in turn revealed wide variability even within the group. Altogether, our results indicate that disease severity is not merely dependent on secretory profile of the mutations. Thus, we hypothesize that intricate molecular detail such as the precise localization of mutant protein in the cell as well as its ability to assemble into a functionally active oligomer might largely influence disease severity among XLRS patients.

Generation of induced pluripotent stem cells from a patient with X-linked juvenile retinoschisis.

X-linked juvenile retinoschisis (XLRS) is a hereditary retinal dystrophy manifested as splitting of anatomical layers of retina. In this report, we generated a patient-specific induced pluripotent stem cell (iPSC) line, TVGH-iPSC-013-05, from the peripheral blood mononuclear cells of a male patient with XLRS by using the Sendai-virus delivery system. We believe that XLRS patient-specific iPSCs provide a powerful in vitro model for evaluating the pathological phenotypes of the disease.