Disease mechanisms of X-linked retinitis pigmentosa due to RP2 and RPGR mutations

Application of Electrophysiology in Non-Macular Inherited Retinal Dystrophies

Inherited retinal dystrophies encompass a diverse group of disorders affecting the structure and function of the retina, leading to progressive visual impairment and, in severe cases, blindness. Electrophysiology testing has emerged as a valuable tool in assessing and diagnosing those conditions, offering insights into the function of different parts of the visual pathway from retina to visual cortex and aiding in disease classification. This review provides an overview of the application of electrophysiology testing in the non-macular inherited retinal dystrophies focusing on both common and rare variants, including retinitis pigmentosa, progressive cone and cone-rod dystrophy, bradyopsia, Bietti crystalline dystrophy, late-onset retinal degeneration, and fundus albipunctatus. The different applications and limitations of electrophysiology techniques, including multifocal electroretinogram (mfERG), full-field ERG (ffERG), electrooculogram (EOG), pattern electroretinogram (PERG), and visual evoked potential (VEP), in the diagnosis and management of these distinctive phenotypes are discussed. The potential for electrophysiology testing to allow for further understanding of these diseases and the possibility of using these tests for early detection, prognosis prediction, and therapeutic monitoring in the future is reviewed.

Translatability barriers between preclinical and clinical trials of AAV gene therapy in inherited retinal diseases

Inherited retinal diseases (IRDs) are progressive degenerative diseases which cause gradual vision loss or complete blindness. As over 270 gene mutations have been identified in the underlying pathology of IRDs, gene therapy as a treatment modality has been an increasingly active realm of investigation. Currently, the most common vehicle of ocular gene delivery is the adeno-associated virus (AAV) vector. This is injected into the immune-privileged subretinal space to mediate transgene expression in retinal cells. Although numerous animal models of IRDs have demonstrated successful outcomes following AAV-mediated gene delivery, many of these studies fail to translate into successful outcomes in clinical trials. The purpose of this review is to A) comparatively assess preclinical and clinical IRD trials in which the success of AAV-mediated therapy failed to translate between animal and human participants B) discuss factors which may complicate the translatability of gene therapy in animals to results in humans.

Functional Analysis of a Novel, Non-Canonical RPGR Splice Variant Causing X-Linked Retinitis Pigmentosa

X-linked retinitis pigmentosa (XLRP) caused by mutations in the RPGR gene is one of the most severe forms of RP due to its early onset and intractable progression. Most cases have been associated with genetic variants within the purine-rich exon ORF15 region of this gene. RPGR retinal gene therapy is currently being investigated in several clinical trials. Therefore, it is crucial to report and functionally characterize (all novel) potentially pathogenic DNA sequence variants. Whole-exome sequencing (WES) was performed for the index patient. The splicing effects of a non-canonical splice variant were tested on cDNA from whole blood and a minigene assay. WES revealed a rare, non-canonical splice site variant predicted to disrupt the wildtype splice acceptor and create a novel acceptor site 8 nucleotides upstream of RPGR exon 12. Reverse-transcription PCR analyses confirmed the disruption of the correct splicing pattern, leading to the insertion of eight additional nucleotides in the variant transcript. Transcript analyses with minigene assays and cDNA from peripheral blood are useful tools for the characterization of splicing defects due to variants in the RPGR and may increase the diagnostic yield in RP. The functional analysis of non-canonical splice variants is required to classify those variants as pathogenic according to the ACMG's criteria.

Thicknesses of the retina and choroid in children with retinitis pigmentosa

PURPOSE

To compare the retinal thicknesses (RT) and choroidal thicknesses (CT) in retinitis pigmentosa (RP) children with those of healthy children using enhanced depth imaging (EDI) optical coherence tomography (OCT). The RT and CT in different genetic subgroups of autosomal dominant RP (ADRP) and X-linked inheritance RP (XLRP) were further studied to investigate the characteristics of retinal and choroidal changes in the early stages of RP.

METHOD

A retrospective analysis was performed on a group of patients with RP who underwent EDI-OCT. Thirty-two children (64 eyes) with RP and 28 age- and refraction-matched healthy children (56 eyes) were included in the study. Seven of the 32 RP children (14 eyes) had X-linked inheritance RP, and 10 (20 eyes) had autosomal dominant inheritance RP. RT and CT were measured by optical coherence tomography and compared between the 32 children with RP and 28 controls and between 7 XLRP and 10 ADRP children.

RESULT

Among the 32 children with RP, there were 18 males and 14 females with an average age of 6.6 ± 2.4 years. The mean RT was smaller in the RP group than in the control group at all of the locations. The mean temporal CT was smaller in the RP group (243.76 ± 60.82 μm) than in the control group (275.23 ± 40.92 μm) (P = 0.001), while there was no significant thinning on the foveal or nasal side. The best-corrected visual acuity of the XLRP group (0.40 ± 0.19) was worse than that of the ADRP group (0.68 ± 0.21) (P = 0.001), but the disease duration was the same (P = 0.685). The mean foveal RT was smaller in the XLRP group (173.85 ± 22.87 μm) than in the ADRP group (192.20 ± 9.70 μm) (P = 0.003), while there was no significant thinning at the other locations we studied. The mean temporal CT was smaller in the XLRP group (211.21 ± 69.41 μm) than in the ADRP group (274.45 ± 57.91 μm) (P = 0.007); CT measurements in XLRP children showed a more severe reduction on the temporal side.

CONCLUSION

The choroid in RP children was preferentially smaller on the temporal side of the macula, and retinal thinning was relatively extensive. Children with RP have strong clinical and genetic heterogeneity. The XLRP children demonstrated greater RT reduction at the fovea and greater CT reduction at the temporal side of the macula than the ADRP children. Our findings also provide evidence that the changes in thicknesses may be indicative of the greater severity of XLRP versus ADRP in the early stage.

Zebrafish Model in Ophthalmology to Study Disease Mechanism and Drug Discovery

Visual impairment and blindness are common and seriously affect people’s work and quality of life in the world. Therefore, the effective therapies for eye diseases are of high priority. Zebrafish (Danio rerio) is an alternative vertebrate model as a useful tool for the mechanism elucidation and drug discovery of various eye disorders, such as cataracts, glaucoma, diabetic retinopathy, age-related macular degeneration, photoreceptor degeneration, etc. The genetic and embryonic accessibility of zebrafish in combination with a behavioral assessment of visual function has made it a very popular model in ophthalmology. Zebrafish has also been widely used in ocular drug discovery, such as the screening of new anti-angiogenic compounds or neuroprotective drugs, and the oculotoxicity test. In this review, we summarized the applications of zebrafish as the models of eye disorders to study disease mechanism and investigate novel drug treatments.

Spectrum of Disease Severity in Patients With X-Linked Retinitis Pigmentosa Due to RPGR Mutations

Purpose

The purpose of this study was to perform a detailed longitudinal phenotyping of X-linked retinitis pigmentosa (RP) caused by mutations in the RPGR gene during a long follow-up period.

Methods

An Italian cohort of 48 male patients (from 31 unrelated families) with RPGR-associated RP was clinically assessed at a single center (mean follow-up = 6.5 years), including measurements of best-corrected visual acuity (BCVA), Goldmann visual field (GVF), optical coherence tomography (OCT), fundus autofluorescence (FAF), microperimetry, and full-field electroretinography (ERG).

Results

Patients (29.6 ± 15.2 years) showed a mean BCVA of 0.6 ± 0.7 logMAR, mostly with myopic refraction (79.2%). Thirty patients (62.5%) presented a typical RP fundus, while the remaining sine pigmento RP. Over the follow-up, BCVA significantly declined at a mean rate of 0.025 logMAR/year. Typical RP and high myopia were associated with a significantly faster decline of BCVA. Blindness was driven primarily by GVF loss. ERG responses with a rod-cone pattern of dysfunction were detectable in patients (50%) that were significantly younger and more frequently presented sine pigmento RP. Thirteen patients (27.1%) had macular abnormalities without cystoid macular edema. Patients (50%) with a perimacular hyper-FAF ring were significantly younger, had a higher BCVA and a better-preserved ellipsoid zone band than those with markedly decreased FAF. Patients harboring pathogenic variants in exons 1 to 14 showed a milder phenotype compared to those with ORF15 mutations.

Conclusions

Our monocentric, longitudinal retrospective study revealed a spectrum disease progression in male patients with RPGR-associated RP. Slow disease progression correlated with sine pigmento RP, absence of high myopia, and mutations in RPGR exons 1 to 14.

A novel missense mutation of RPGR identified from retinitis pigmentosa affects splicing of the ORF15 region and causes loss of transcript heterogeneity

Mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene, are the major cause of X-linked retinitis pigmentosa (RP), in which exon open reading frame 15 (ORF15) of RPGR has been implicated to play a substantial role. We identified a novel hemizygous missense mutation E585K of RPGR from whole-exome sequencing of RP. RNA-Seq analysis and functional study were conducted to investigate the underlying pathogenic mechanism of the mutation. Our results showed that the mutation actually affected RPGR ORF15 splicing. RNA-Seq analysis of the human retina followed by validation in cells revealed a complex splicing pattern near the 3' boundary of RPGR exon 14 in the ORF15 region, resulting from a variety of alternative splicing events (ASEs). The wildtype RPGR mini-gene expressed in human 293T cells confirmed these ASEs in vitro. In contrast, without new RNA species detected, the mutant mini-gene disrupted the splicing pattern of the ORF15 region, and caused loss of RPGR transcript heterogeneity. The RNA species derived from the mutant mini-gene were predominated by a minor out-of-frame transcript that was also observed in wildtype RPGR, resulting from an upstream alternative 5' splice site in exon 14. Our findings therefore provide insights into the influence of RPGR exonic mutations on alternative splicing of the ORF15 region, and the underlying molecular mechanism of RP.

RP2-associated retinal disorder in a Japanese cohort: Report of novel variants and a literature review, identifying a genotype-phenotype association

The retinitis pigmentosa 2 (RP2) gene is one of the causative genes for X-linked inherited retinal disorder. We characterized the clinical/genetic features of four patients with RP2-associated retinal disorder (RP2-RD) from four Japanese families in a nationwide cohort. A systematic review of RP2-RD in the Japanese population was also performed. All four patients were clinically diagnosed with retinitis pigmentosa (RP). The mean age at examination was 36.5 (10-47) years, and the mean visual acuity in the right/left eye was 1.40 (0.52-2.0)/1.10 (0.52-1.7) in the logarithm of the minimum angle of resolution unit, respectively. Three patients showed extensive retinal atrophy with macular involvement, and one had central retinal atrophy. Four RP2 variants were identified, including two novel missense (p.Ser6Phe, p.Leu189Pro) and two previously reported truncating variants (p.Arg120Ter, p.Glu269CysfsTer3). The phenotypes of two patients with truncating variants were more severe than the phenotypes of two patients with missense variants. A systematic review revealed additional 11 variants, including three missense and eight deleterious (null) variants, and a statistically significant association between phenotype severity and genotype severity was revealed. The clinical and genetic spectrum of RP2-RD was illustrated in the Japanese population, identifying the characteristic features of a severe form of RP with early macular involvement.

Detailed comparison of phenotype between male patients carrying variants in exons 1-14 and ORF15 of RPGR

PURPOSE

To compare disease severity in detail between patients carrying variants in exons 1-14 and ORF15 of retinitis pigmentosa GTPase regulator (RPGR).

METHODS

Systematic next-generation sequencing data analysis, Sanger sequencing validation and segregation analysis were utilised to identify the pathogenic variants. Detailed ophthalmic examinations, including electroretinograms, fundus photography, fundus autofluorescence and optical coherence tomography were performed. Statistical analysis, including age adjustment and comparison, were performed based on cross-sectional level to compare disease severity between variants in the two RPGR variant groups.

RESULTS

Sixty-two variants were identified in RPGR in 86 patients from 77 unrelated families. Twenty-nine (37.7%) had variants in RPGR-exons 1-14 (group 1) and 48 (62.3%) in RPGR-ORF15 (group 2). Eighty-four patients were diagnosed with X-linked retinitis pigmentosa and only two patients with cone-rod dystrophy. LogMAR visual acuity increased 0.035 and 0.022 each year on average in group 1 and group 2, respectively. Group 2 patients had better visual acuity with a mean logMAR difference of 0.4378, which is significant after age adjustment (P < 0.01). Neither the value of log (ellipsoid zone width) nor central retinal thickness was significantly correlated with variant grouping after considering the effect of the age variable (P = 0.56 and 0.40, respectively). Spherical refractive error did not differ significantly between the two variant groups (P = 0.17). Patterns of autofluorescence included a hyperfluorescent ring at the posterior pole, diffuse hyperfluorescence in the macular area, and dark macular autofluorescence with or without fovea hyperfluorescence. The age and proportion of fundus autofluorescence patterns between the two variant groups were significantly different (P < 0.01).

CONCLUSIONS

Patients with variants in exons 1-14 retained less visual acuity than patients with ORF15 variants and deteriorated faster. However, the ellipsoid zone widths, central retinal thickness and refractions were comparable between the two groups. Autofluorescence pattern relates to the age and the variant grouping.

CoPP-Induced-Induced HO-1 Overexpression Alleviates Photoreceptor Degeneration With Rapid Dynamics: A Therapeutic Molecular Against Retinopathy

Purpose

Retinitis pigmentosa (RP) causes progressive photoreceptor degeneration in the retina. The N-methyl-N-nitrosourea (MNU)-administered mouse is used as a chemically induced RP model with rapid progression rate. This study was designed to study heme oxygenase-1 (HO-1) expression in the MNU-administered mice, and to explore the therapeutic effects of cobalt protoporphyrin (CoPP).

Methods

The HO-1 expression in the retina of MNU-administered mice was analyzed. CoPP was injected intravenously into the MNU-administered mice. Subsequently, the CoPP-treated mice were subjected to functional and morphologic examinations.

Results

HO-1 was involved in the MNU-induced photoreceptor degeneration. CoPP treatment enhanced retinal HO-1 expression in the MNU-administered mice. Electroretinogram (ERG) examination and behavioral tests showed that CoPP treatment improved the retinal responsiveness of MNU-administered mice. Histologic analysis and optical coherence tomography (OCT) examination showed that retinal architecture of the CoPP-treated mice was more intact than that of the MNU+vehicle group. Cone photoreceptors in the MNU-administered mice were rescued efficiently by CoPP treatment. Furthermore, multielectrode array (MEA) recording showed that CoPP treatment mitigated the spontaneous firing response, enhanced the light-induced firing response, and preserved the basic configurations of visual signal pathway in the MNU-administered mice. Mechanism studies suggested that CoPP afforded these therapeutic effects by modulating the apoptosis cascades and alleviating the oxidative stress in degenerative retinas.

Conclusions

CoPP alleviated photoreceptor degeneration and rectified the signaling abnormities in MNU-administered mice. CoPP may serve as a potential medication against degenerative retinopathy.

Novel mutations of RPGR in Chinese families with X-linked retinitis pigmentosa

Background

RP (retinitis pigmentosa) is a group of hereditary retinal degenerative diseases. XLRP is a relatively severe subtype of RP. Thus, it is necessary to identify genes and mutations in patients who present with X-linked retinitis pigmentosa.

Methods

Genomic DNA was extracted from peripheral blood. The coding regions and intron-exon boundaries of the retinitis pigmentosa GTPase regulator (RPGR) and RP2 genes were amplified by PCR and then sequenced directly. Ophthalmic examinations were performed to identify affected individuals from two families and to characterize the phenotype of the disease.

Results

Mutation screening demonstrated two novel nonsense mutations (c.1541C > G; p.S514X and c.2833G > T; p.E945X) in the RPGR gene. The clinical manifestation of family 1 with mutations in exon 13 was mild. Genotype-phenotype correlation analysis suggested that patients with mutations close to the downstream region of ORF15 in family 2 manifested an early loss of cone function. Family 2 carried a nonsense mutation in ORF15 that appeared to have a semi-dominant pattern of inheritance. All male patients and two female carriers in family 2 manifested pathological myopia (PM), indicating that there may be a distinctive X-linked genotype-phenotype correlation between RP and PM.

Conclusions

We identified two novel mutations of the RPGR gene, which broadens the spectrum of RPGR mutations and the phenotypic spectrum of the disease in Chinese families.

Retinal Phenotype in the rd9 Mutant Mouse, a Model of X-Linked RP

Retinal degeneration 9 (rd9) mice carry a mutation in the retina specific “Retinitis Pigmentosa GTPase Regulator (RPGR)” Open Reading Frame (ORF) 15 gene, located on the X chromosome and represent a rare model of X-linked Retinitis Pigmentosa (XLRP), a common and severe form of retinal degeneration (Wright et al., 2010; Tsang and Sharma, 2018). The rd9 RPGR-ORF15 mutation in mice causes lack of the protein in photoreceptors and a slow degeneration of these cells with consequent decrease in Outer Nuclear Layer (ONL) thickness and amplitude of ERG responses, as previously described (Thompson et al., 2012). However, relative rates of rod and cone photoreceptor loss, as well as secondary alterations occurring in neuronal and non-neuronal retinal cell types of rd9 mutants remain to be assessed. Aim of this study is to extend phenotype analysis of the rd9 mouse retina focusing on changes occurring in cells directly interacting with photoreceptors. To this purpose, first we estimated rod and cone survival and its degree of intraretinal variation over time; then, we studied the morphology of horizontal and bipolar cells and of the retinal pigment epithelium (RPE), extending our observations to glial cell reactivity. We found that in rd9 retinas rod (but not cone) death is the main cause of decrease in ONL thickness and that degeneration shows a high degree of intraretinal variation. Rod loss drives remodeling in the outer retina, with sprouting of second-order neurons of the rod-pathway and relative sparing of cone pathway elements. Remarkably, despite cone survival, functional defects can be clearly detected in ERG recordings in both scotopic and photopic conditions. Moderate levels of Muller cells and microglial reactivity are sided by striking attenuation of staining for RPE tight junctions, suggesting altered integrity of the outer Blood Retina Barrier (BRB). Because of many features resembling slowly progressing photoreceptor degeneration paradigms or early stages of more aggressive forms of RP, the rd9 mouse model can be considered a rare and useful tool to investigate retinal changes associated to a process of photoreceptor death sustained throughout life and to reveal disease biomarkers (e.g., BRB alterations) of human XLRP.

Clinical and genetic characteristics of 14 patients from 13 Japanese families with RPGR-associated retinal disorder: report of eight novel variants

Variants in the retinitis pigmentosa GTPase regulator (RPGR) gene are a major cause of X-linked inherited retinal disorder (IRD). We herein describe the clinical and genetic features of 14 patients from 13 Japanese families harboring RPGR variants in a nationwide cohort. Comprehensive ophthalmological examinations were performed to classify the patients into one of the phenotype subgroups: retinitis pigmentosa (RP) and cone rod dystrophy (CORD). The mean age of onset/at examination was 13.8/38.1 years (range, 0-50/11-72), respectively. The mean visual acuity in the right/left eye was 0.43/0.43 (range, 0.1-1.7/-0.08-1.52) LogMAR unit. Eight patients had RP, and six had CORD. Whole-exome sequencing with target analyses identified 13 RPGR variants in 730 families with IRD, including 8 novel variants. An association between the phenotype subgroup and the position of variants (cutoff of amino acid 950) was revealed. To conclude, the clinical and genetic spectrum of RPGR-associated retinal disorder was first illustrated in a Japanese population, with a high proportion of novel variants. These results suggest the distinct genetic background of RPGR in the Japanese population, in which the genotype-phenotype association was affirmed. This evidence should be helpful monitoring and counseling patients and in selecting patients for future therapeutic trials.

Chaperones and retinal disorders

Defects in protein folding and trafficking are a common cause of photoreceptor degeneration, causing blindness. Photoreceptor cells present an unusual challenge to the protein folding and transport machinery due to the high rate of protein synthesis, trafficking and the renewal of the outer segment, a primary cilium that has been modified into a specialized light-sensing compartment. Phototransduction components, such as rhodopsin and cGMP-phosphodiesterase, and multimeric ciliary transport complexes, such as the BBSome, are hotspots for mutations that disrupt proteostasis and lead to the death of photoreceptors. In this chapter, we review recent studies that advance our understanding of the chaperone and transport machinery of phototransduction proteins.

Photoreceptor actin dysregulation in syndromic and non-syndromic retinitis pigmentosa

Retinitis pigmentosa (RP) is the leading cause of inherited blindness. RP is a genetically heterogeneous disorder, with more than 100 different causal genes identified in patients. Central to disease pathogenesis is the progressive loss of retinal photoreceptors. Photoreceptors are specialised sensory neurons that exhibit a complex and highly dynamic morphology. The highly polarised and elaborated architecture of photoreceptors requires precise regulation of numerous cytoskeletal elements. In recent years, significant work has been placed on investigating the role of microtubules (specifically, the acetylated microtubular axoneme of the photoreceptor connecting cilium) and their role in normal photoreceptor function. This has been driven by the emerging field of ciliopathies, human diseases arising from mutations in genes required for cilia formation or function, of which RP is a frequently reported phenotype. Recent studies have highlighted an intimate relationship between cilia and the actin cystoskeleton. This review will focus on the role of actin in photoreceptors, examining the connection between actin dysregulation in RP.

CRISPR/Cas9 genome surgery for retinal diseases

Retinal diseases that impair vision can impose heavy physical and emotional burdens on patients' lives. Currently, clustered regularly interspaced short palindromic repeats (CRISPR) is a prevalent gene-editing tool that can be harnessed to generate disease model organisms for specific retinal diseases, which are useful for elucidating pathophysiology and revealing important links between genetic mutations and phenotypic defects. These retinal disease models are fundamental for testing various therapies and are indispensible for potential future clinical trials. CRISPR-mediated procedures involving CRISPR-associated protein 9 (Cas9) may also be used to edit genome sequences and correct mutations. Thus, if used for future therapies, CRISPR/Cas9 genome surgery could eliminate the need for patients with retinal diseases to undergo repetitive procedures such as drug injections. In this review, we will provide an overview of CRISPR/Cas9, discuss the different types of Cas9, and compare Cas9 to other endonucleases. Furthermore, we will explore the many ways in which researchers are currently utilizing this versatile tool, as CRISPR/Cas9 may have far-reaching effects in the treatment of retinal diseases.

Caring for Hereditary Childhood Retinal Blindness

Inherited retinal diseases (IRDs) are a major cause of incurable familial blindness in the Western world. In the pediatric population, IRDs are a major contributor to the 19 million children worldwide with visual impairment. Unfortunately, the road to the correct diagnosis is often complicated in the pediatric population, as typical diagnostic tools such as fundus examination, electrodiagnostic studies, and other imaging modalities may be difficult to perform in the pediatric patient. In this review, we describe the most significant IRDs with onset during the pediatric years (ie, before the age of 18). We describe the pathogenesis, clinical presentation, and potential treatment of these diseases. In addition, we advocate the use of a pedigree (family medical history), electroretinography, and genetic testing as the 3 most crucial tools for the correct diagnosis of IRDs in the pediatric population.

Identification of a Novel Mutation in the ABCA4 Gene in a Chinese Family with Retinitis Pigmentosa Using Exome Sequencing

Retinitis pigmentosa (RP) is a group of hereditary, degenerative retinal disorders characterized by progressive retinal dysfunction, outer retina cell loss, and retinal tissue atrophy. It eventually leads to tunnel vision and legal or total blindness. Here, we aimed to reveal the causal gene and mutation contributing to the development of autosomal recessive RP (arRP) in a consanguineous family. A novel homozygous mutation, c.4845delT (p.K1616Rfs*46), in the ATP-binding cassette subfamily A member 4 gene (ABCA4) was identified. It may reduce ABCA4 protein activity, leading to progressive degeneration of both rod and cone photoreceptors. The study extends the arRP genotypic spectrum and confirms a genotype–phenotype relationship. The present study may also disclose some new clues for RP genetic causes and pathogenesis, as well as clinical and genetic diagnosis. The research findings may contribute to improvement in clinical care, therapy, genetic screening, and counseling.

Characterization of a novel RP2-OSTF1 interaction and its implication for actin remodelling

Retinitis pigmentosa 2 (RP2) is the causative gene for a form of X-linked retinal degeneration. RP2 was previously shown to have GTPase-activating protein (GAP) activity towards the small GTPase ARL3 via its N-terminus, but the function of the C-terminus remains elusive. Here, we report a novel interaction between RP2 and osteoclast-stimulating factor 1 (OSTF1), an intracellular protein that indirectly enhances osteoclast formation and activity and is a negative regulator of cell motility. Moreover, this interaction is abolished by a human pathogenic mutation in RP2. We utilized a structure-based approach to pinpoint the binding interface to a strictly conserved cluster of residues on the surface of RP2 that spans both the C- and N-terminal domains of the protein, and which is structurally distinct from the ARL3-binding site. In addition, we show that RP2 is a positive regulator of cell motility in vitro, recruiting OSTF1 to the cell membrane and preventing its interaction with the migration regulator Myo1E.

X-linked Retinitis Pigmentosa

X-linked retinitis pigmentosa (XLRP) is considered to be one of the most severe forms of retinitis pigmentosa (RP). It accounts for about 6-20% of all RP cases, including about 10% in the United States and 25% in England.

Applications of CRISPR/Cas9 in retinal degenerative diseases

Gene therapy is a potentially effective treatment for retinal degenerative diseases. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system has been developed as a new genome-editing tool in ophthalmic studies. Recent advances in researches showed that CRISPR/Cas9 has been applied in generating animal models as well as gene therapy in vivo of retinitis pigmentosa (RP) and leber congenital amaurosis (LCA). It has also been shown as a potential attempt for clinic by combining with other technologies such as adeno-associated virus (AAV) and induced pluripotent stem cells (iPSCs). In this review, we highlight the main points of further prospect of using CRISPR/Cas9 in targeting retinal degeneration. We also emphasize the potential applications of this technique in treating retinal degenerative diseases.