Comparison of structural progression between ciliopathy and non-ciliopathy associated with autosomal recessive retinitis pigmentosa

Pathogenic Variants in CEP290 or IQCB1 Cause Earlier-Onset Retinopathy in Senior-Loken Syndrome Compared to Those in INVS, NPHP3, or NPHP4

PURPOSE

Senior-Loken syndrome (SLSN) is an autosomal recessive disorder characterized by retinopathy and nephronophthisis. This study aimed to evaluate whether different phenotypes are associated with different variants or subsets of 10 SLSN-associated genes based on an in-house data set and a literature review.

DESIGN

Retrospective case series.

METHODS

Patients with biallelic variants in SLSN-associated genes, including NPHP1, INVS, NPHP3, NPHP4, IQCB1, CEP290, SDCCAG8, WDR19, CEP164, and TRAF3IP1, were recruited. Ocular phenotypes and nephrology medical records were collected for comprehensive analysis.

RESULTS

Variants in 5 genes were identified in 74 patients from 70 unrelated families, including CEP290 (61.4%), IQCB1 (28.6%), NPHP1 (4.2%), NPHP4 (2.9%), and WDR19 (2.9%). The median age at the onset of retinopathy was approximately 1 month (since birth). Nystagmus was the most common initial sign in patients with CEP290 (28 of 44, 63.6%) or IQCB1 (19 of 22, 86.4%) variants. Cone and rod responses were extinguished in 53 of 55 patients (96.4%). Characteristic fundus changes were observed in CEP290- and IQCB1-associated patients. During follow-up, 70 of the 74 patients were referred to nephrology, among whom nephronophthisis was not detected in 62 patients (88.6%) at a median age of 6 years but presented in 8 patients (11.4%) aged approximately 9 years.

CONCLUSIONS

Patients with pathogenic variants in CEP290 or IQCB1 presented early with retinopathy, whereas other patients with INVS, NPHP3, or NPHP4 variants first developed nephropathy. Therefore, awareness of the genetic and clinical features may facilitate the clinical management of SLSN, especially early intervention of kidney problems for patients with eyes affected first.

Clinical and Molecular Aspects of C2orf71/PCARE in Retinal Diseases

Mutations in the photoreceptor-specific C2orf71 gene (also known as photoreceptor cilium actin regulator protein PCARE) cause autosomal recessive retinitis pigmentosa type 54 and cone-rod dystrophy. No treatments are available for patients with C2orf71 retinal ciliopathies exhibiting a severe clinical phenotype. Our understanding of the disease process and the role of PCARE in the healthy retina significantly limits our capacity to transfer recent technical developments into viable therapy choices. This study summarizes the current understanding of C2orf71-related retinal diseases, including their clinical manifestations and an unclear genotype-phenotype correlation. It discusses molecular and functional studies on the photoreceptor-specific ciliary PCARE, focusing on the photoreceptor cell and its ciliary axoneme. It is proposed that PCARE is an actin-associated protein that interacts with WASF3 to regulate the actin-driven expansion of the ciliary membrane during the development of a new outer segment disk in photoreceptor cells. This review also introduces various cellular and animal models used to model these diseases and provides an overview of potential treatments.

Nuclear Receptor Subfamily 2 Group E Member 3 (NR2E3): Role in Retinal Development and Disease

NR2E3 is a nuclear hormone receptor gene required for the correct development of the retinal rod photoreceptors. Expression of NR2E3 protein in rod cell precursors suppresses cone-specific gene expression and, in concert with other transcription factors including NRL, activates the expression of rod-specific genes. Pathogenic variants involving NR2E3 cause a spectrum of retinopathies, including enhanced S-cone syndrome, Goldmann-Favre syndrome, retinitis pigmentosa, and clumped pigmentary retinal degeneration, with limited evidence of genotype-phenotype correlations. A common feature of NR2E3-related disease is an abnormally high number of cone photoreceptors that are sensitive to short wavelength light, the S-cones. This characteristic has been supported by mouse studies, which have also revealed that loss of Nr2e3 function causes photoreceptors to develop as cells that are intermediate between rods and cones. While there is currently no available cure for NR2E3-related retinopathies, there are a number of emerging therapeutic strategies under investigation, including the use of viral gene therapy and gene editing, that have shown promise for the future treatment of patients with NR2E3 variants and other inherited retinal diseases. This review provides a detailed overview of the current understanding of the role of NR2E3 in normal development and disease, and the associated clinical phenotypes, animal models, and therapeutic studies.

Clinical and Molecular Features of a Chinese Cohort With Syndromic and Nonsyndromic Retinal Dystrophies Related to the CEP290 Gene

PURPOSE

To reveal the clinical and genetic features of 54 Chinese pedigrees with syndromic or nonsyndromic retinal dystrophies related to CEP290 and to explore the genotype-phenotype correlation.

DESIGN

Retrospective cohort study.

METHODS

Patients diagnosed with nonsyndromic inherited retinal dystrophy (IRD) or syndromic ciliopathy (SCP) were enrolled. We identified 61 patients from 54 families carrying biallelic pathogenic CEP290 variants using next-generation sequencing, Sanger sequencing, and co-segregation validation. Genotype-phenotype correlation was evaluated.

RESULTS

This study included 37 IRD patients from 32 families and 24 patients with SCP from 22 pedigrees. Four retinal dystrophy phenotypes were confirmed: Leber congenital amaurosis (LCA, 46/61), early-onset severe retinal dystrophy (EOSRD, 4/61), retinitis pigmentosa (RP, 10/61), and cone-rod dystrophy (CORD, 1/61). The SCP phenotypes included Joubert syndrome (JS) (23/24) and Bardet-Biedl syndrome (BBS) (1/24). We detected 73 different CEP290 variants, of which 33 (45.2%) were not previously reported. Two novel copy number variations (CNVs) and 1 novel pathogenic synonymous change were identified. The most recurrent alterations in the IRD and SCP were p.Q123* (6/64, 9.4%) and p.I556Ffs*17 (10/44, 22.7%), respectively. IRD patients carried more stop-gain alleles (25/64, 39.1%), whereas SCP patients carried more frameshift alleles (23/44, 52.3%).

CONCLUSIONS

LCA was the most common retinal dystrophy phenotype, and JS was the most prevalent syndrome in CEP290 patients; RP/CORD and BBS may be present in early adulthood. The hot spot variants and distribution of genotypes were distinct between IRD and SCP. Our study expands the CEP290 variant spectrum and enhances the current knowledge of CEP290 heterogeneity.

MERTK missense variants in three patients with retinitis pigmentosa

BACKGROUND

MERTK (MER proto-oncogene, tyrosine kinase) is a transmembrane protein essential in regulating photoreceptor outer segment phagocytosis. Biallelic mutations in MERTK cause retinal degeneration. Here we present the retinal phenotype of three patients with missense variants in MERTK.

MATERIALS AND METHODS

All patients underwent a full clinical examination, fundus photography, short-wavelength fundus autofluorescence and optical coherence tomography imaging. Two patients also underwent Goldmann visual field testing and electroretinography was undertaken for the third patient. Molecular genetic testing was undertaken using next generation or whole-exome sequencing with all variants confirmed by Sanger sequencing.

RESULTS

The first patient was a 29-year-old female heterozygous for a missense variant (c.1133C>T, p.Thr378 Met) and a nonsense variant (c.1744_1751delinsT, p.Ile582Ter) in MERTK. The second patient was a 26-year-old male homozygous for a c.2163T>A, p.His721Gln variant in MERTK. The third patient was an 11-year-old female heterozygous for a deletion of exons 5-19 and a missense variant (c.1866 G>C, p.Lys622Asn) in MERTK. Reduced night vision was the initial symptom in all patients. Fundoscopy revealed typical signs of retinitis pigmentosa (RP) with early-onset macular atrophy. All three MERTK missense variants affect highly conserved residues within functional domains, have low population frequencies and are predicted to be pathogenic in silico.

CONCLUSIONS

We report three missense variants in MERTK and present the associated phenotypic data, which are supportive of non-syndromic RP. MERTK is a promising candidate for viral-mediated gene replacement therapy. Moreover, one variant represents a single nucleotide transition, which is theoretically targetable with CRISPR-Cas9 base-editing.

ASSESSMENTS OF MACULAR FUNCTION BY FOCAL MACULAR ELECTRORETINOGRAPHY AND STATIC PERIMETRY IN EYES WITH RETINITIS PIGMENTOSA

PURPOSE

To assess the macular function by focal macular electroretinography and static perimetry in eyes with retinitis pigmentosa.

METHODS

Eighty-eight eyes of 88 retinitis pigmentosa patients were analyzed. The relationships between the focal macular electroretinography components and the mean deviations (MDs) of the Humphrey Field Analyzer 10-2 were determined. Spectral-domain optical coherence tomography was used to determine the integrity of the ellipsoid zone (EZ) and the interdigitation zone.

RESULTS

Forward-backward stepwise regression analyses showed that the amplitudes (r = 0.45, P < 0.01) and implicit times (r = -0.29, P < 0.01) of the b-waves were significantly correlated with the MDs. Some of the eyes had reduced b-wave amplitudes (<1.0 µ V) and disrupted interdigitation zone, despite having a better MD (≥ -10.0 dB) and intact EZ. Subgroup analyses of eyes with better MD (≥ -10.0 dB) showed that the EZ width was correlated with the MDs but not with the b-wave amplitude. The thickness of the EZ-retinal pigment epithelium as an alternative indicator of interdigitation zone was correlated with the b-wave amplitude (r = 0.32, P = 0.04) but not with the MDs (r = -0.10, P = 0.53).

CONCLUSION

The fact that the focal macular electroretinography amplitudes are reduced before the shortening of the EZ in the early stage of retinitis pigmentosa indicates that the focal macular electroretinography amplitudes are an earlier indicator of macular dysfunction than the Humphrey Field Analyzer 10-2 findings.

Unilateral Retinitis Pigmentosa Associated with Possible Ciliopathy and a Novel Mutation

Unilateral retinitis pigmentosa (URP) is a rare retinal dystrophy. We describe the clinical course of two patients with (URP) unilateral retinitis pigmentosa confirmed by genetic testing, indicating ciliary dysfunction. Methods: The methods used in this study included a detailed ophthalmic examination, multimodal retinal imaging, Goldmann visual fields, full-field electroretinography (ffERG) and targeted next-generation sequencing. Results: A 32-year-old female (patient 1) and 65-year-old male (patient 2) were found to have URP. ffERG showed a non-recordable response in the affected eye and a response within normal limits in the fellow eye of patient 1, while patient 2 showed non-recordable responses in the apparently unaffected eye and a profound reduction in the photopic and scotopic responses in the affected eye. Next-generation sequencing revealed novel compound heterozygous c.373 C>T (p.Arg125Trp) and c.730-22_730-19dup variants in AGBL5 in patient 1, and a novel hemizygous c.1286 C>T (p.Pro429Leu) in patient 2; both gene mutations were 0%. Segregation analysis was not possible for either of the mutations. Conclusion: This report expands the clinical and molecular genetic spectrum of URP.

A homozygous in-frame duplication within the LRRCT consensus sequence of CFAP410 causes cone-rod dystrophy, macular staphyloma and short stature

Ciliopathies are a group of genetic dystrophies causing syndromic and non-syndromic retinal degeneration. We identified CFAP410 as the causative gene in a patient with childhood-onset retinal dystrophy without other systemic symptoms at the age of 20. This 20-year-old man presented with cone-rod dystrophy and CFAP410 homozygous in-frame duplication variants (c.340_351dup). His clinical features included early subnormal vision, posterior pole staphyloma, and short stature. Unlike the previously reported features of retinal ciliopathy, our patient showed no obvious retinal pigmentation and only a slight hyper-autofluorescent parafoveal ring at the 16-year follow up. This case report aims to characterize the clinical features in a patient with novel, homozygous and likely pathogenic in-frame duplication variants in the CFAP410 gene. Ultimately, this report will help contribute to the understanding of CFAP410-associated ciliopathies.

Relationship Between Macular Curvature and Common Causative Genes of Retinitis Pigmentosa in Japanese Patients

Purpose

To determine the relationship between the macular curvature and the causative genes of retinitis pigmentosa (RP).

Methods

We examined the medical records of the right eyes of 65 cases with RP (31 men and 34 women; average age, 47.6 years). There were 31 cases with the EYS variants, 11 cases with the USH2A variants, six cases with the RPGR variants, 13 cases with the RP1 variants, and four cases with the RP1L1 variants. The mean curvature of Bruch's membrane was calculated within 6 mm of the fovea as the mean macular curvature index (MMCI, 1/µm). We used multiple linear regression analysis to determine the independence of the causative genes contributing to the MMCIs after adjustments for age, sex, axial length, and width of the ellipsoid zone.

Results

The median MMCI was −31.2 × 10⁻⁵/µm for the RPGR eyes, −16.5 × 10⁻⁵/µm for the RP1L1 eyes, −13.0 × 10⁻⁵/µm for the RP1 eyes, −9.8 × 10⁻⁵/µm for the EYS eyes, and −9.0 × 10⁻⁵/µm for the USH2A eyes. Compared with the EYS gene as the reference gene, the RPGR gene was significantly related to the MMCI values after adjusting for the other parameters (P = 5.30 × 10⁻⁶). In contrast, the effects of the other genes, USH2A, RP1, and RP1L1, were not significantly different from that of the EYS gene (P = 0.26, P = 0.49, and P = 0.92, respectively).

Conclusions

The RPGR gene had a stronger effect on the steep macular curvature than the other ciliopathy-related genes.

Differences in Intraretinal Pigment Migration Across Inherited Retinal Dystrophies

PURPOSE

To determine whether there are differences in the prevalence of intraretinal pigment migration (IPM) across ages and genetic causes of inherited retinal dystrophies (IRDs).

DESIGN

Retrospective cohort study.

METHODS

Patients were evaluated at a single tertiary referral center. All patients with a clinical diagnosis of IRD and confirmatory genetic testing were included in these analyses. A total of 392 patients fit inclusion criteria, and 151 patients were excluded based on inconclusive genetic testing. Patients were placed into 3 groups, ciliary and ciliary-related photoreceptor, nonciliary photoreceptor, and retinal pigment epithelium (RPE), based on the cellular expression of the gene and the primary affected cell type. The presence of IPM was evaluated by using slit lamp biomicroscopy, indirect ophthalmoscopy, and wide-field color fundus photography.

RESULTS

IPM was seen in 257 of 339 patients (75.8%) with mutations in photoreceptor-specific genes and in 18 of 53 patients (34.0%) with mutations in RPE-specific genes (P < .0001). Pairwise analysis following stratification by age and gene category suggested significant differences at all age groups between patients with mutations in photoreceptor-specific genes and patients with mutations in RPE-specific genes (P < .05). A fitted multivariate logistic regression model was produced and demonstrated that the incidence of IPM increases as a function of both age and gene category.

CONCLUSIONS

IPM is a finding more commonly observed in IRDs caused by mutations in photoreceptor-specific genes than RPE-specific genes. The absence of IPM does not always rule out IRD and should raise suspicion for disease mutations in RPE-specific genes.

Management of retinitis pigmentosa by Wharton's jelly-derived mesenchymal stem cells: prospective analysis of 1-year results

PURPOSE

The aim of the study was to investigate annual structural and functional results, and their correlation with inheritance pattern of retinitis pigmentosa (RP) patients who were treated with Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs).

MATERIAL AND METHODS

This prospective, sequential, open-label phase-3 clinical study was conducted at Ankara University Faculty of Medicine, Department of Ophthalmology, between April 2019 and May 2020. The study included 34 eyes from 32 retinitis pigmentosa patients of various genotypes who were enrolled in the stem cells clinical trial. The patients were followed for 12 months after the WJ-MSCs transplantation into subtenon space and evaluated with consecutive examinations. Genetic mutations were investigated using a retinitis pigmentosa panel sequencing method consisting of 90 genes. All patients underwent a complete routine ophthalmic examination with best corrected visual acuity, optical coherence tomography angiography, visual field, and full-field electroretinography. Quantitative data obtained from baseline (T0), 6th month (T1), and 12th month (T2) examinations were compared.

RESULTS

According to timepoints at T0, T1, and T2: The mean outer retinal thickness was 100.3 μm, 119.1 μm, and 118.0 μm, respectively (p = 0.01; T0 < T1, T2). The mean horizontal ellipsoid zone width were 2.65 mm, 2.70 mm, and 2.69 mm respectively (p = 0.01; T0 < T1, T2). The mean best corrected visual acuity (BCVA) were 70.5 letters, 80.6 letters, and 79.9 letters, respectively (p = 0.01; T0 < T1, T2). The mean fundus perimetry deviation index (FPDI) was 8.0%, 11.4%, and 11.6%, respectively (p = 0.01; T0 < T1, T2). The mean full-field flicker ERG parameters at T0, T1, and T2: amplitudes were 2.4 mV, 5.0 mV, and 4.6 mV, respectively (p = 0.01; T0 < T1, T2). Implicit time were 43.3 ms, 37.9 ms, and 38.6 ms, respectively (p = 0.01; T0 > T1, T2). According to inheritance pattern, BCVA, FPDI, ERG amplitude, and implicit time data improved significantly in autosomal dominant (AD) and in autosomal recessive (AR) RP at 1 year follow-up (pAD = 0.01, pAR = 0.01; pAD = pAR > pX-linked). No ocular or systemic adverse events related to the surgical methods and/or WJ-MSCs were observed during the 1 year follow-up period.

CONCLUSION

Subtenon transplantation of WJ-MSCs was found to be effective and safe in the treatment of RP during the first year, similar to the sixth month's results. In autosomal dominant and autosomal recessive inheritance of RP, regardless of the genetic mutations, subtenon administration of WJ-MSCs can be considered an effective and safe option without any adverse effect for slowing or stopping the disease progression.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04224207 . Registered 8 January 2020.

Optical coherence tomography in the evaluation of retinitis pigmentosa

BACKGROUND

Optical coherence tomography (OCT) is a non-invasive imaging test that provides easily obtainable and highly reproducible cross-sectional images of the retina. Improved modalities of the OCT that are capable of providing high quality images of not only the retina, but also the deeper structures and vasculature have been developed, including swept-source OCTs and OCT angiography.

MATERIALS AND METHODS

Review.

RESULTS

The use of OCT in the monitoring of retinitis pigmentosa has been well described and numerous signs of disease progression have been studied. Notably among them are the detection of changes to retinal thickness, the ellipsoid zone, the vasculature on OCT angiography, and cystoid macular edema.

CONCLUSION

In this review, we discuss the multiple applications of OCT as a tool in the monitoring of retinitis pigmentosa and its potential use as an outcome measurement in current and future therapeutic endeavors.

Management of Retinitis Pigmentosa via Platelet-Rich Plasma or Combination with Electromagnetic Stimulation: Retrospective Analysis of 1-Year Results

PURPOSE

To investigate whether the natural progression rate of retinitis pigmentosa can be decreased by subtenon autologous platelet-rich plasma application alone or combination with retinal electromagnetic stimulation.

METHODS

The study includes retrospective analysis of 60 patients with retinitis pigmentosa. Patients constitute three groups with similar demographic characteristics: the combined management group (group 1) consists of 20 patients with retinitis pigmentosa (40 eyes) who received combined retinal electromagnetic stimulation and subtenon platelet-rich plasma; the subtenon platelet-rich plasma-only group (group 2) consisted of 20 patients with retinitis pigmentosa (40 eyes); the natural course (control) group (group 3) consists of 20 patients with retinitis pigmentosa (40 eyes) who did not receive any treatment. Horizontal and vertical ellipsoid zone width, fundus perimetry deviation index, and best corrected visual acuity changes were compared within and between groups after a 1-year follow-up period.

RESULTS

Detected horizontal ellipsoid zone percentage changes were + 1% in group 1, - 2.85% in group 2, and - 9.36% in group 3 (Δp 1 > 2 > 3). Detected vertical ellipsoid zone percentage changes were + 0.34% in group 1, - 3.05% in group 2, and - 9.09% in group 3 (Δp 1 > 2 > 3). Detected fundus perimetry deviation index percentage changes were + 0.05% in group 1, - 2.68% in group 2, and - 8.78% in group 3 (Δp 1 > 2 > 3).

CONCLUSION

Platelet-rich plasma is a good source of growth factors, but its half-life is 4-6 months. Subtenon autologous platelet-rich plasma might more effectively slow down photoreceptor loss when repeated as booster injections and combined with retinal electromagnetic stimulation.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT04252534.

Progressive RPE atrophy and photoreceptor death in KIZ-associated autosomal recessive retinitis pigmentosa

Background: To evaluate the long-term progression of autosomal recessive retinitis pigmentosa (RP) due to mutations in KIZ using multimodal imaging and a quantitative analytical approach.Methods: Whole exome sequencing (WES) and targeted capture sequencing were used to identify mutation. Fundus photography, short-wavelength autofluorescence (SW-AF), spectral-domain optical coherence tomography (SD-OCT) imaging, and electroretinography (ERG) were analyzed. Serial measurements of peripheral retinal pigment epithelium (RPE) atrophy area with SW-AF, as well as the ellipsoid zone (EZ) width using SD-OCT were performed.Results: Two homozygous variants in KIZ-a c.226C>T mutation as well as a previously unreported c.119_122delAACT mutation-were identified in four unrelated patients. Fundus examination and ERG revealed classic rod-cone dysfunction, and SD-OCT demonstrated outer retinal atrophy with centrally preserved EZ line. SW-AF imaging revealed hyperautofluorescent rings with surrounding parafoveal, mid-peripheral and widespread loss of autofluorescence. The RPE atrophy area increased annually by 4.9%. Mean annual exponential rates of decline for KIZ patients were 8.5% for visual acuity and 15.9% for 30 Hz Flicker amplitude. The average annual reduction distance of the EZ distance was 66.5 μm per year.Conclusions: RPE atrophy progresses along with a loss of photoreceptors, and parafoveal RPE hypoautofluorescence is commonly seen in KIZ-associated RP patients. KIZ-associated RP is an early-onset severe rod-cone dystrophy.