The characterization of retinal phenotype in a family with C1QTNF5-related late-onset retinal degeneration

Treatment Strategy With Gene Editing for Late-Onset Retinal Degeneration Caused by a Founder Variant in C1QTNF5

Purpose

Genome editing is an emerging group of technologies with the potential to ameliorate dominant, monogenic human diseases such as late-onset retinal degeneration (L-ORD). The goal of this study was to identify disease stages and retinal locations optimal for evaluating the efficacy of a future genome editing trial.

Methods

Twenty five L-ORD patients (age range, 33-77 years; median age, 59 years) harboring the founder variant S163R in C1QTNF5 were enrolled from three centers in the United Kingdom and United States. Patients were examined with widefield optical coherence tomography (OCT) and chromatic perimetry under dark-adapted and light-adapted conditions to derive phenomaps of retinal disease. Results were analyzed with a model of a shared natural history of a single delayed exponential across all subjects and all retinal locations.

Results

Critical age for the initiation of photoreceptor loss ranged from 48 years at the temporal paramacular retina to 74 years at the inferior midperipheral retina. Subretinal deposits (sRET-Ds) became more prevalent as critical age was approached. Subretinal pigment epithelial deposits (sRPE-Ds) were detectable in the youngest patients showing no other structural or functional abnormalities at the retina. The sRPE-D thickness continuously increased, reaching 25 µm in the extrafoveal retina and 19 µm in the fovea at critical age. Loss of light sensitivity preceded shortening of outer segments and loss of photoreceptors by more than a decade.

Conclusions

Retinal regions providing an ideal treatment window exist across all severity stages of L-ORD.

Longitudinal Changes of Retinal Structure in Molecularly Confirmed C1QTNF5 Patients With Late-Onset Retinal Degeneration

Purpose

The purpose of this study was to present our findings on the natural history of late-onset retinal degeneration (LORD) in patients with molecularly confirmed C1QTNF5 heterozygous pathogenic variants and assess suitability of retinal structure parameters for disease monitoring.

Methods

Sixteen patients with C1QTNF5-LORD were retrospectively identified from Moorfields Eye Hospital, UK. Fundus autofluorescence (FAF), optical coherence tomography (OCT) scans, and best-corrected visual acuity (BCVA) were collected. Area of atrophy (AA) was manually drawn in FAF images. Ellipsoid zone (EZ) width and foveal retinal thickness of the whole retina and outer retina were extracted from OCT scans. Age-related changes were tested with linear-mixed models.

Results

Patients had median age of 62.3 years (interquartile range [IQR] = 58.8-65.4 years) at baseline, and median follow-up of 5.1 years (IQR = 2.6-7.6 years). AA, EZ width, and retinal thickness parameters remained unchanged until age 50 years, but showed significant change with age thereafter (all P < 0.0001). AA and EZ width progressed rapidly (dynamic range normalized rates = 4.3-4.5%/year) from age 53.9 and 50.8 years (estimated inflection points), respectively. Retinal thickness parameters showed slower progression rates (range = 1.6-2.5%/year) from age 60 to 62.3. BCVA (median = 0.3 LogMAR, IQR = 0.0-1.0 at baseline) showed a rapid decline (3.3%) from age 70 years. Findings from patients with earlier disease showed FAF atrophy manifests in the temporal retina initially, and then progresses nasally.

Conclusions

Patients with LORD remained asymptomatic until age 50 years, before suffering rapid outer retinal degeneration. EZ width and AA showed rapid progression and high interocular correlation, representing promising outcome metrics. Clinical measures also capturing the temporal retina may be preferable, enabling earlier detection and better disease monitoring.

Translational Relevance

Area of atrophy in FAF images and OCT-measured EZ width represent promising outcome metrics for disease monitoring in patients with C1QTNF5-LORD.

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.

Distinct Phenotypic Consequences of Pathogenic Mutants Associated with Late-Onset Retinal Degeneration

A pathologic feature of late-onset retinal degeneration caused by the S163R mutation in C1q-tumor necrosis factor-5 (C1QTNF5) is the presence of unusually thick deposits between the retinal pigmented epithelium (RPE) and the vascular choroid, considered a hallmark of this disease. Following its specific expression in mouse RPE, the S163R mutant exhibits a reversed polarized distribution relative to the apically secreted wild-type C1QTNF5, and forms widespread, prominent deposits that gradually increase in size with aging. The current study shows that S163R deposits expand to a considerable thickness through a progressive increase in the basolateral RPE membrane, substantially raising the total RPE height, and enabling their clear imaging as a distinct hyporeflective layer by noninvasive optical coherence tomography in advanced age animals. This phenotype bears a striking resemblance to ocular pathology previously documented in patients harboring the S163R mutation. Therefore, a similar viral vector-based gene delivery approach was used to also investigate the behavior of P188T and G216C, two novel pathogenic C1QTNF5 mutants recently reported in patients for which histopathologic data are lacking. Both mutants primarily impacted the RPE/photoreceptor interface and did not generate basal laminar deposits. Distinct distribution patterns and phenotypic consequences of C1QTNF5 mutants were observed in vivo, which suggested that multiple pathobiological mechanisms contribute to RPE dysfunction and vision loss in this disorder.

Outer retinal corrugations in late-onset retinal degeneration: a diagnostic finding demonstrated with multimodal imaging

OBJECTIVE

Late-onset retinal degeneration (L-ORD) is a rare autosomal dominant retinal degeneration that presents in the sixth decade and leads to severe visual loss. The objective of this paper is to describe outer retinal corrugations as a diagnostic feature of L-ORD.

METHODS

This retrospective study reviewed consecutive patients diagnosed with L-ORD, confirmed through complete ophthalmic examination, multimodal imaging and genetic tests. Multimodal imaging investigations included spectral domain-optical coherence tomography (SD-OCT) and ultra-wide-field colour and autofluorescence fundus photographs.

RESULTS

A total of 13 eyes of 9 patients with L-ORD had outer retinal corrugations identified on OCT scans.

CONCLUSION

Outer retinal corrugations may be a diagnostic finding for L-ORD. The detection of this sign may aid diagnosis and characterisation of this disease and help in the differential diagnosis with other acquired pathologies.

Extracellular vesicles from retinal pigment epithelial cells expressing R345W-Fibulin-3 induce epithelial-mesenchymal transition in recipient cells

We have shown previously that expression of R345W-Fibulin-3 induces epithelial-mesenchymal transition (EMT) in retinal pigment epithelial (RPE) cells. The purpose of the current study was to determine if extracellular vesicles (EVs) derived from RPE cells expressing R345W-Fibulin-3 mutation are sufficient to induce EMT in recipient cells. ARPE-19 cells were infected with luciferase-tagged wild-type (WT)- Fibulin-3 or luciferase-tagged R345W-Fibulin-3 (R345W) using lentiviruses. EVs were isolated from the media by ultracentrifugation or density gradient ultracentrifugation. Transmission electron microscopy and cryogenic electron microscopy were performed to study the morphology of the EVs. The size distribution of EVs were determined by nanoparticle tracking analysis (NTA). EV cargo was analysed using LC-MS/MS based proteomics. EV-associated transforming growth factor beta 1 (TGFβ1) protein was measured by enzyme-linked immunosorbent assay. The capacity of EVs to stimulate RPE migration was evaluated by treating recipient cells with WT- or R345W-EVs. The role of EV-bound TGFβ was determined by pre-incubation of EVs with a pan-TGFβ blocking antibody or IgG control. EM imaging revealed spherical vesicles with two subpopulations of EVs: a group with diameters around 30 nm and a group with diameters over 100 nm, confirmed by NTA analysis. Pathway analysis revealed that members of the sonic hedgehog pathway were less abundant in R345W- EVs, while EMT drivers were enriched. Additionally, R345W-EVs had higher concentrations of TGFβ1 compared to control. Critically, treatment with R345W-EVs was sufficient to increase EMT marker expression, as well as cell migration in recipient cells. This EV-increased cell migration was significantly inhibited by pre-incubation of EVs with pan-TGFβ-neutralising antibody. In conclusion, the expression of R345W-Fibulin-3 alters the size and cargo of EVs, which are sufficient to enhance the rate of cell migration in a TGFβ dependent manner. These results suggest that EV-bound TGFβ plays a critical role in the induction of EMT in RPE cells.

MICROPERIMETRY IN FOVEAL-SPARING ATROPHIC LATE-ONSET RETINAL DEGENERATION

PURPOSE

To understand the baseline and longitudinal microperimetry characteristics in foveal-sparing atrophic late-onset retinal degeneration.

METHOD

Prospective, cross-sectional, longitudinal study in which patients from the retina clinics of two academic teaching hospitals were included. Mesopic microperimetry was performed using a Nidek MP-1 micro-perimeter. Mean total, foveal, inner ring, and outer ring sensitivities were analyzed.

RESULTS

A total of 20 eyes from 10 patients had baseline data. The subset of 10 eyes from five patients had follow-up data. The mean baseline macular sensitivity was 10.02 dB (± 5.26) with findings showing symmetry between both eyes. In the follow-up cohort, there was a significant loss of outer ring (0.83 dB per year; P = 0.0001), inner ring (0.67 dB per year; P = 0.034), and foveal sensitivity (0.92 dB loss per year; P = 0.015), whereas the mean sensitivity decreased significantly (0.66 dB per year; P = 0.0008) at 4-year follow-up. The drop in mean sensitivity was associated with significant increases in the number of deep scotoma points (6.20, P = 0.037) and a decrease in the number of normal points (-6.30, P = 0.022).

CONCLUSION

Microperimetry is a useful tool for macular function follow-up to measure disease progression in late-onset retinal degeneration.

Anterior segment phenotypic changes in late-onset retinal degeneration with Ser163Arg mutation in CTRP5/C1QTNF5

PURPOSE

Late-onset retinal degeneration (L-ORD) is a rare retinal dystrophy with anterior segment (AS) abnormalities, including long anterior zonules (LAZ) and iris atrophy. This investigation evaluates AS changes in a L-ORD cohort.

METHODS

Prospective, longitudinal study including L-ORD individuals (Ser163Arg) with ocular exam and standard slit-lamp photographs between 2011 and 2022. AS images were merged and assessed for LAZ number and zonule-free zone (ZFZ) radius. Further clinical findings such as iris atrophy patterns were reported descriptively.

RESULTS

Twelve eyes of 6 patients (4 males, median age = 60.5 years) were included, showing a median of 160 (11-372) LAZs, mainly localized superiorly (39%) and inferiorly (24%). There was a high inter-ocular correlation (rs = 0.94, p < 0.01), no difference in LAZ count between eyes (p = 0.82), and an inverse relationship between LAZ and age (r =  - 0.82; p < 0.05). The ZFZ had median 2.1 mm (1.3-5.4), with no inter-ocular difference (p = 0.31). Iris transillumination defects occurred in 11/12 eyes, with 4 major patterns identified: pupillary ruff rarefaction (10/12), patchy atrophy (6/12), notched defects (6/12), and radial streaks (2/12). In a short-term follow-up of 5.9 years, 4 eyes showed a reduction in LAZ count to median 139.5 (67-169) (p = 0.50) and a concomitant increase in ZFZ measurement to median 2.2 (1.7-2.6) (p = 0.17).

CONCLUSION

This study confirms symmetric LAZs count and ZFZ in L-ORD, with ZFZ measurements smaller than in previous cohorts. A reduction in LAZs count and an increase in ZFZ with age were suggested longitudinally, yet findings need further evaluation as follow-up was limited to two cases.

IFI44L and C1QTNF5 as promising biomarkers of proliferative diabetic retinopathy

Proliferative diabetic retinopathy (PDR) is a world-wide leading cause of blindness among adults and may be associated with the influence of genetic factors. It is significant to search for genetic biomarkers of PDR. In our study, we collected genomic data about PDR from gene expression omnibus (GEO) database. Differentially expressed gene (DEG) analysis and weighted gene co-expression network analysis (WGCNA) were carried out. The gene module with the highest gene significance (GS) was defined as the key module. Hub genes were identified by Venn diagram. Then we verified the expression of hub genes in validation data sets and built a diagnostic model by least absolute shrinkage and selection operator (LASSO) regression. Enrichment analysis, including gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), gene set enrichment analysis (GSEA) and construction of a protein-protein interaction (PPI) network were conducted. In GSE60436, we identified 466 DEGs. WGCNA established 14 gene modules, and the blue module (GS = 0.64), was the key module. Interferon (IFN)-induced protein 44-like (IFI44L) and complement C1q tumor necrosis factor-related protein 5 (C1QTNF5) were identified as hub genes. The expression of hub genes in GEO datasets was verified and a diagnostic model was constructed by LASSO as follows: index = IFI44L * 0.0432 + C1QTNF5 * 0.11246. IFI44L and C1QTNF5 might affect the disease progression of PDR by regulating metabolism-related and inflammatory pathways. IFI44L and C1QTNF5 may play important roles in the disease process of PDR, and a LASSO regression model suggested that the 2 genes could serve as promising biomarkers of PDR.

Late-Onset Retinal Degeneration: Clinical Perspectives

Late-onset retinal degeneration (L-ORD) is a type of retinal dystrophy marked by nyctalopia and subretinal pigment epithelium deposits, which eventually promote retinal atrophy with final visual compromise. L-ORD may also present with changes in the anterior segment, notably long anterior zonules and iris atrophy, distinguishing it from other inherited eye conditions. Although it can clinically simulate age-related macular degeneration, L-ORD has a different course of progression and prognosis, requiring adequate diagnosis for patient counseling. This review summarizes the main clinical, genetic, pathophysiological, diagnostic, and therapeutic aspects of L-ORD to help ophthalmologists identify and manage this rare ocular disease.

Long anterior lens zonules with retinal stripes: a case report

Background

Long anterior lens zonules   (LAZs) is a rare disease that was mostly conducted among African Americans. Through the observation of a Chinese patient, we discoverd that the disease may show different characteristics in Asians.

Case presentation

A patient with vision loss due to a macular hole was found to have several special clinical signs during vitrectomy combined with phacoemulsification and intraocular lens implantation surgery in our hospital, including radially oriented lines on the anterior capsule with pigment, a shallow anterior chamber, slightly high intraocular pressure, and radial retinal stripes in the peripheral retina. Finally, he was diagnosed with long anterior lens zonule syndrome.

Conclusion

Clinicians need to pay more attention to the rare disease LAZs. It is important to tear the appropriate size of the anterior capsule so as to avoid radial capsular tearing and intraocular lens dislocation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02496-7.

Evolving Patterns of Hyperfluorescent Fundus Autofluorescence Accompany Retinal Atrophy in the Rat and Mimic Atrophic Age-Related Macular Degeneration

Purpose

Complex two-dimensional (2D) patterns of hyperfluorescent short-wave fundus autofluorescence (FAF) at the border of geographic atrophy (GA) can predict its expansion in patients with late non-exudative “dry” AMD. However, preclinical models do not phenocopy this important feature of disease. We sought to describe the spatiotemporal changes in hyperfluorescent FAF patterns that occur following acute oxidative stress, potentially in association with GA expansion.

Methods

Sprague Dawley rats (n = 54) received systemic sodium iodate (25–45 mg/kg, n = 90 eyes) or saline (n = 18 eyes) and underwent serial full fundus imaging by confocal scanning laser ophthalmoscopy, including blue FAF and delayed near-infrared analysis. Composite images of the fundus were assembled, and the 2D patterns were described qualitatively and quantitatively. A subset of eyes underwent tissue analysis, and four underwent optical coherence tomography (OCT) imaging.

Results

Reproducibly changing, complex patterns of hyperfluorescent FAF emerge at the borders of toxin-induced damage; however, in the absence of GA expansion, they percolate inward within the region of retinal pigment epithelium loss, evolving, maturing, and senescing in situ over time. Unexpectedly, the late FAF patterns most closely resemble the diffuse tricking form of clinical disease. A five-stage classification system is presented.

Conclusions

Longitudinal, full-fundus imaging of outer retinal atrophy in the rat eye identifies evolving, complex patterns of hyperfluorescent FAF that phenocopy aspects of disease.

Translational Relevance

This work provides a novel tool to assess hyperfluorescent FAF in association with progressive retinal atrophy, a therapeutic target in late AMD.

Reticular Pseudodrusen in Late-Onset Retinal Degeneration

PURPOSE

To characterize the association of reticular pseudodrusen (RPD) with late-onset retinal degeneration (L-ORD) using multimodal imaging.

DESIGN

Prospective, 2-center, longitudinal case series.

PARTICIPANTS

Twenty-nine patients with L-ORD.

METHODS

All patients were evaluated within a 3-year interval with near-infrared reflectance, fundus autofluorescence, and spectral-domain OCT. In addition, a subset of patients also underwent indocyanine green angiography, fundus fluorescein angiography, mesopic microperimetry, and multifocal electroretinography.

MAIN OUTCOME MEASURES

Prevalence, topographic distribution, and temporal phenotypic changes of RPD in L-ORD.

RESULTS

A total of 29 patients with molecularly confirmed L-ORD were included in this prospective study. Reticular pseudodrusen was detected in 18 patients (62%) at baseline, 10 of whom were men. The prevalence of RPD varied with age. The mean age of RPD patients was 57.3 ± 7.2 years. Reticular pseudodrusen was not seen in patients younger than the fifth decade of life (n = 3 patients) or in the eighth decade of life (n = 5 patients). Reticular pseudodrusen were found commonly in the macula with relative sparing of the fovea and also were identified in the peripheral retina. The morphologic features of RPD changed with follow-up. Two patients (3 eyes) demonstrated RPD regression.

CONCLUSIONS

Reticular pseudodrusen is found frequently in patients with L-ORD and at a younger age than in individuals with age-related macular degeneration (AMD). Reticular pseudodrusen exhibits quick formation and collapse, change in type and morphologic features with time, and relative foveal sparing and also has a peripheral retinal location in L-ORD.

QUANTITATIVE ANALYSIS OF LONGITUDINAL CHANGES IN MULTIMODAL IMAGING OF LATE-ONSET RETINAL DEGENERATION

PURPOSE

To quantitatively analyze clinically relevant features on longitudinal multimodal imaging of late-onset retinal degeneration to characterize disease progression.

METHODS

Fundus autofluorescence (FAF), infrared reflectance, and optical coherence tomography imaging of 4 patients with late-onset retinal degeneration were acquired over 3 to 15 years (20 visits total). Corresponding regions of interest were analyzed on FAF (reticular pseudodrusen [RPD], "speckled FAF," and chorioretinal atrophy) and infrared reflectance (hyporeflective RPD and target RPD) using quantitative measurements, including contour area, distance to fovea, contour overlap, retinal thickness, and texture features.

RESULTS

Cross-sectional analysis revealed a moderate correlation (RPD FAF ∩ RPD infrared reflectance = 63%) between contour area across modalities. Quantification of retinal thickness and texture analysis of areas contoured on FAF objectively differentiated the contour types. A longitudinal analysis of aligned images demonstrates that the contoured region of atrophy both encroaches toward the fovea and grows monotonically with a rate of 0.531 mm/year to 1.969 mm/year (square root of area, n = 5 eyes). A retrospective analysis of precursor lesions of atrophy reveals quantifiable progression from RPD to speckled FAF to atrophy.

CONCLUSION

Image analysis of time points before the development of atrophy reveals consistent patterns over time and space in late-onset retinal degeneration that may provide useful outcomes for this and other degenerative retinal diseases.

CHARACTERIZING THE NATURAL HISTORY OF FOVEAL-SPARING ATROPHIC LATE-ONSET RETINAL DEGENERATION

PURPOSE

To identify quantifiable markers of disease progression in patients with foveal-sparing atrophic late-onset retinal degeneration using fundus autofluorescence and spectral-domain optical coherence tomography imaging.

METHODS

Natural history study evaluating patients within a 3-year interval. Disease progression was assessed based on the area of retinal atrophy, macular topographic distribution of lesions, retinal and choroidal thickness and volume, and choroidal vascularity index.

RESULTS

Twenty-four eyes (12 individuals) were included for fundus autofluorescence, and 31 eyes (16 individuals) for spectral-domain optical coherence tomography studies. Measurements were symmetrical between eyes of the same patient. The area of atrophy significantly enlarged (P = 0.002), with a growth rate of 2.67 mm2/year (SD: 2.13; square rooted: 0.57 mm/year, SD = 0.34). Baseline area of atrophy and progression both correlated with age. Most atrophic lesions were found in the temporal macula and progressed nasally at follow-up. Central choroidal and retinal thicknesses and volume in late-onset retinal degeneration cases were significantly reduced compared with controls, but only central retinal thickness decreased significantly at follow-up.

CONCLUSION

This study identifies the area of atrophy and central retinal thickness, but not chorioretinal volume or choroidal thickness, as markers of short-term progression in late-onset retinal degeneration. These findings may be useful for disease monitoring and late-onset retinal degeneration interventional studies.

Longitudinal phenotypic study of late-onset retinal degeneration due to a founder variant c.562C>A p.(Pro188Thr) in the C1QTNF5 gene

Background: Late-onset retinal degeneration (L-ORD) is a rare autosomal dominant retinal dystrophy related to C1QTNF5 gene variants.Materials and methods: Twenty-six patients (21-81 years) with L-ORD due to c.562C>A p.(Pro188Thr) with a mean follow-up time of 8 years (range 1-37 years) underwent an extensive ophthalmic work-up.Results: Best-corrected visual acuity (BCVA) and visual fields were maintained up to 50 to 55 years (n = 8), with a gradual decline, but conservation of functional central vision between 55 to 65 years (n = 15), followed by a steep decrease in overall visual function beyond 65 years (n = 9). Classic anterior segment findings in L-ORD of abnormally long, anteriorly inserted lens zonules were absent in most patients (n = 24/26). In contrast, findings of iris transillumination and sphincter pupillae atrophy with poor dilation were novel. Patients presented with three completely different initial fundus phenotypes: adjoining pavingstone-like atrophic patches (type 1) (n = 6/20); tiny yellow-white subretinal dots (type 2) (n = 8/20); or larger yellow, thick, round sub-RPE drusenoid deposits (type 3) (n = 4/20). Two patients had a mixed phenotype. Although different in presentation phenotype, patients eventually all progressed to a common panretinal atrophy with diffuse intraretinal pigment migration beyond the age of 65. Progression pace, and thus visual prognosis, differed depending on presentation phenotype. Specifically, type 2 appears to have a more benign course.Conclusions: Phenotypic analysis showed three distinct presenting phenotypes with a considerable intrafamilial variability both in age of onset of clinical signs and in disease progression, with a fair visual potential (>20/40) until the seventh decade.Abbreviations: L-ORD: Late-onset retinal degeneration; C1QTNF5: complement 1Q tumor necrosis factor 5; OCT: Ocular coherence tomography; BCVA: Best-corrected visual acuity; RPE: Retinal pigment epithelium; ffERG: Full-field electroretinography; IRD: Inherited retinal dystrophy; CNV: Choroidal neovascularization; LAZ: Long anteriorly inserted zonules; AMPK: AMP-activated protein kinase; IOP: Intraocular pressure; cSLO: confocal scanning laser ophthalmoscopy; BAF: Blue light autofluorescence; NIR-AF: Near-infrared autofluorescence; NIR-R: Near-infrared reflectance; RF: Red-free; SD-OCT: Spectral domain ocular coherence tomography; HRR: Hardy-Rand-Rittler pseudo-isochromatic plates; AS: anterior segment; UBM: ultrasound biomicroscopy; PCR: Polymerase chain reaction; SNP: Single nucleotide polymorphism; VEGF: Vascular endothelial growth factor; IZ: Interdigitation zone; EZ: Ellipsoid zone; ELM: External limiting membrane; LP: Light perception; AMD: Age-related macular degeneration; SFD: Sorsby fundus dystrophy.

Autosomal Dominant Gyrate Atrophy-Like Choroidal Dystrophy Revisited: 45 Years Follow-Up and Association with a Novel C1QTNF5 Missense Variant

We present a long-term follow-up in autosomal dominant gyrate atrophy-like choroidal dystrophy (adGALCD) and propose a possible genotype/phenotype correlation. Ophthalmic examination of six patients from two families revealed confluent areas of choroidal atrophy resembling gyrate atrophy, starting in the second decade of life. Progression continued centrally, reaching the fovea at about 60 years of age. Subretinal deposits, retinal pigmentation or choroidal neovascularization as seen in late-onset retinal degeneration (LORD) were not observed. Whole genome sequencing revealed a novel missense variant in the C1QTNF5 gene (p.(Q180E)) which was found in heterozygous state in all affected subjects. Haplotype analysis showed that this variant found in both families is identical by descent. Three-dimensional modeling of the possible supramolecular assemblies of C1QTNF5 revealed that the p.(Q180E) variant led to the destabilization of protein tertiary and quaternary structures, affecting both the stability of the single protomer and the entire globular head, thus exerting detrimental effects on the formation of C1QTNF5 trimeric globular domains and their interaction. In conclusion, we propose that the p.(Q180E) variant causes a specific phenotype, adGALCD, that differs in multiple clinical aspects from LORD. Disruption of optimal cell-adhesion mechanisms is expected when analyzing the effects of the point mutation at the protein level.

Whole genome sequencing reveals novel mutations causing autosomal dominant inherited macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is a common sight threatening condition. However, there are a number of monogenic macular dystrophies that are clinically similar to AMD, which can potentially provide pathogenetic insights.

METHODS

Three siblings from a non-consanguineous Greek-Cypriot family reported central visual disturbance and nyctalopia. The patients had full ophthalmic examinations and color fundus photography, spectral-domain ocular coherence tomography and scanning laser ophthalmoscopy. Targeted polymerase chain reaction (PCR) was performed as a first step to attempt to identify suspected mutations in C1QTNF5 and TIMP3 followed by whole genome sequencing.

RESULTS

The three patients were noted to have symptoms of nyctalopia, early paracentral visual field loss and, in older patients, central vision loss. Imaging identified pseudodrusen, retinal atrophy and RPE-Bruch's membrane separation. Whole genome sequencing of the proband revealed two novel heterozygous variants in C1QTNF5, c.556C>T, and c.569C>G. The mutation segregated with disease in this family, occurred in cis, and resulted in missense amino acid changes P186S and S190W in C1QTNF5. In silico modeling of the variants revealed that the S190W mutations was likely to have the greatest pathologic effect and that the combination of the mutations was likely to have an additive effect.

CONCLUSIONS

The novel mutations in C1QTNF5 identified here expand the genotypic spectrum of mutations causing late-onset retinal dystrophy.

IMPROVING THE AGE-RELATED MACULAR DEGENERATION CONSTRUCT: A New Classification System

Previous models of disease in age-related macular degeneration (AMD) were incomplete in that they did not encompass subretinal drusenoid deposits (pseudodrusen), subtypes of neovascularization, and polypoidal choroidal vasculopathy. In addition, Type 3 neovascularization starts in the retina and may not necessarily involve the choroid. As such, the term choroidal neovascularization is not appropriate for these eyes. The new aspects in the AMD construct are to include specific lipoprotein extracellular accumulations, namely drusen and subretinal drusenoid deposits, as early AMD. The deposition of specific types of deposit seems to be highly correlated with choroidal thickness and topographical location in the macula. Late AMD includes macular neovascularization or atrophy. The particular type of extracellular deposit is predictive of the future course of the patient. For example, eyes with subretinal drusenoid deposits have a propensity to develop outer retinal atrophy, complete outer retinal and retinal pigment epithelial atrophy, or Type 3 neovascularization as specific forms of late AMD. Given Type 3 neovascularization may never involve the choroid, the term macular neovascularization is suggested for the entire spectrum of neovascular disease in AMD. In contrast to older classification systems, the proposed system encompasses the relevant presentations of disease and more precisely predicts the future course of the patient. In doing so, the concept was developed that there may be genetic risk alleles, which are not necessarily the same alleles that influence disease expression.

LONGITUDINAL STRUCTURAL CHANGES IN LATE-ONSET RETINAL DEGENERATION

PURPOSE

To characterize longitudinal structural changes in early stages of late-onset retinal degeneration to investigate pathogenic mechanisms.

METHODS

Two affected siblings, both with a S163R missense mutation in the causative gene C1QTNF5, were followed for 8+ years. Color fundus photos, fundus autofluorescence images, near-infrared reflectance fundus images, and spectral domain optical coherence tomography scans were acquired during follow-up.

RESULTS

Both patients, aged 45 and 50 years, had good visual acuities (>20/20) in the context of prolonged dark adaptation. Baseline color fundus photography demonstrated yellow-white, punctate lesions in the temporal macula that correlated with a reticular pattern on fundus autofluorescence and near-infrared reflectance imaging. Baseline spectral domain optical coherence tomography imaging revealed subretinal deposits that resemble reticular pseudodrusen described in age-related macular degeneration. During follow-up, these affected areas developed confluent thickening of the retinal pigment epithelial layer and disruption of the ellipsoid zone of photoreceptors before progressing to overt retinal pigment epithelium and outer retinal atrophy.

CONCLUSION

Structural changes in early stages of late-onset retinal degeneration, revealed by multimodal imaging, resemble those of reticular pseudodrusen observed in age-related macular degeneration and other retinal diseases. Longitudinal follow-up of these lesions helps elucidate their progression to frank atrophy and may lend insight into the pathogenic mechanisms underlying diverse retinal degenerations.

Choriocapillaris Nonperfusion is Associated With Poor Visual Acuity in Eyes With Reticular Pseudodrusen

PURPOSE

To study choriocapillaris blood flow in age-related macular degeneration (AMD) using optical coherence tomography angiography (OCTA) and study its correlation to visual acuity (VA) in eyes with reticular pseudodrusen (RPD) vs those with drusen without RPD (drusen).

DESIGN

Cross-sectional study.

METHODS

Patients with either drusen or RPD in early AMD underwent OCTA imaging of the superior, inferior, and/or nasal macula. We quantified "percent choriocapillaris area of nonperfusion" (PCAN) in eyes with RPD vs those with drusen. We assessed the repeatability of PCAN and its correlations with VA.

RESULTS

Twenty-nine eyes of 26 patients with RPD and 21 eyes of 16 age-matched AMD patients with drusen were included. Qualitatively, the choriocapillaris in areas with RPD showed focal dark regions without flow signal on OCTA (nonperfusion). The repeatability coefficient of PCAN was 0.49%. Eyes with RPD had significantly greater PCAN compared with eyes with drusen (7.31% and 3.88%, respectively; P < .001). We found a significant correlation between PCAN and VA for the entire dataset (r = 0.394, P = .005). When considering eyes with RPD separately, this correlation was stronger (r = 0.474, P = .009) but lost significance when considering eyes with drusen separately (r = 0.175, P = .45).

CONCLUSIONS

Eyes with RPD have significantly larger areas of choriocapillaris nonperfusion compared with eyes with drusen and no RPD. The correlation between PCAN and VA in this RPD population provides a potential mechanistic explanation for vision compromise in RPD compared with other forms of drusen in AMD.

Loss of CTRP5 improves insulin action and hepatic steatosis

The gene that encodes C1q/TNF-related protein 5 (CTRP5), a secreted protein of the C1q family, is mutated in individuals with late-onset retinal degeneration. CTRP5 is widely expressed outside the eye and also circulates in plasma. Its physiological role in peripheral tissues, however, has yet to be elucidated. Here, we show that Ctrp5 expression is modulated by fasting and refeeding, and by different diets, in mice. Adipose expression of CTRP5 was markedly upregulated in obese and diabetic humans and in genetic and dietary models of obesity in rodents. Furthermore, human CTRP5 expression in the subcutaneous fat depot positively correlated with BMI. A genetic loss-of-function mouse model was used to address the metabolic function of CTRP5 in vivo. On a standard chow diet, CTRP5-deficient mice had reduced fasting insulin but were otherwise comparable with wild-type littermate controls in body weight and adiposity. However, when fed a high-fat diet, CTRP5-deficient animals had attenuated hepatic steatosis and improved insulin action. Loss of CTRP5 also improved the capacity of chow-fed aged mice to respond to subsequent high-fat feeding, as evidenced by decreased insulin resistance. In cultured adipocytes and myotubes, recombinant CTRP5 treatment attenuated insulin-stimulated Akt phosphorylation. Our results provide the first genetic and physiological evidence for CTRP5 as a negative regulator of glucose metabolism and insulin sensitivity. Inhibition of CTRP5 action may result in the alleviation of insulin resistance associated with obesity and diabetes.

Detailed functional and structural phenotype of Bietti crystalline dystrophy associated with mutations in CYP4V2 complicated by choroidal neovascularization

PURPOSE

To describe in detail the phenotype of a patient with Bietti crystalline dystrophy (BCD) complicated by choroidal neovascularization (CNV) and the response to intravitreal Bevacizumab (Avastin^®; Genentech/Roche).

METHODS

A 34-year-old woman with BCD and mutations in CYP4V2 (c.802-8_806del13/p.H331P:c992A>C) underwent a complete ophthalmic examination, full-field flash electroretinography (ERG), kinetic and two-color dark-adapted perimetry, and dark-adaptometry. Imaging was performed with spectral domain optical coherence tomography (SD-OCT), near infrared (NIR) and short wavelength (SW) fundus autofluorescence (FAF), and fluorescein angiography (FA).

RESULTS

Best-corrected visual acuity (BCVA) was 20/20 and 20/60 for the right and left eye, respectively. There were corneal paralimbal crystal-like deposits. Kinetic fields were normal in the peripheral extent. Retinal crystals were most obvious on NIR-reflectance and corresponded with hyperreflectivities within the RPE on SD-OCT. There was parafoveal/perifoveal hypofluorescence on SW-FAF and NIR-FAF. Rod > cone sensitivity loss surrounded fixation and extended to ~10° of eccentricity corresponding to regions of photoreceptor outer segment-retinal pigmented epithelium (RPE) interdigitation abnormalities. The outer nuclear layer was normal in thickness. Recovery of sensitivity following a ~76% rhodopsin bleach was normal. ERGs were normal. A subretinal hemorrhage in the left eye co-localized with elevation of the RPE on SD-OCT and leakage on FA, suggestive of CNV. Three monthly intravitreal injections of Bevacizumab led to restoration of BCVA to baseline (20/25).

CONCLUSION

crystals in BCD were predominantly located within the RPE. Photoreceptor outer segment and apical RPE abnormalities underlie the relatively extensive retinal dysfunction observed in relatively early-stage BCD. Intravitreal Bevacizumab was effective in treating CNV in this setting.

Pathological Effects of Mutant C1QTNF5 (S163R) Expression in Murine Retinal Pigment Epithelium

PURPOSE

The mutation S163R in complement C1q tumor necrosis factor-related protein-5 (C1QTNF5) causes an autosomal dominant disorder known as late-onset retinal degeneration (L-ORD). In this study, our goal is to evaluate the consequences of mutant S163R C1QTNF5 expression in mouse RPE following its delivery using an adeno-associated viral (AAV) vector.

METHODS

We generated AAV vectors containing either human wild-type C1QTNF5 or mutant S163R C1QTNF5 driven by an RPE-specific BEST1 promoter, and delivered them subretinally into one eye of adult C57BL/6 mice. Transgene expression was detected by immunohistochemistry. Retinal function was assessed by full-field ERG. Pathological changes were further examined by digital fundus imaging and spectral-domain optical coherence tomography (SD-OCT).

RESULTS

We show that the AAV-expressed mutant S163R leads to pathological effects similar to some of those found in patients with advanced L-ORD, including RPE thinning, RPE cell loss, and retinal degeneration. In addition, we provide in vivo evidence that mutant S163R C1QTNF5 can form large, transparent, spherical intracellular aggregates throughout the RPE, which are detectable by light microscopy. In contrast to AAV-expressed wild-type C1QTNF5, which is secreted apically from the RPE toward the photoreceptor cells and the outer limiting membrane, the S163R mutant is primarily routed toward the basal side of RPE, where it forms thick, extracellular deposits over time.

CONCLUSIONS

Adeno-associated viral-targeted expression of mutant S163R in the RPE represents a useful approach for quickly generating animal models that mimic pathological features of L-ORD and offers the potential to understand disease mechanisms and develop therapeutic strategies.

Improvement of retinal function in L-ORD after prolonged dark adaptation

OBJECTIVE

To describe the changes in dark-adapted (DA) retinal electrophysiological function after prolonged dark adaptation in a cohort of patients with late-onset retinal degeneration (L-ORD).

DESIGN

Prospective case series.

PARTICIPANTS

Nine patients with either stage 2 or 3 L-ORD.

METHODS

International Society for Clinical Electrophysiology of Vision standard DA electroretinograms (ERGs) were performed before and after a period of extended dark adaptation (16 hours) in a cohort of patients heterozygous for the Ser163Arg mutation in C1QTNF5.

RESULTS

Rod function was abnormal in 8 of 9 patients after standard (20 min) of dark adaptation. After extended dark adaptation, rod function normalized in 4 patients and there was a mean improvement in the DA 0.01 rod-specific ERG b-wave amplitude of 310% (p = 0.004). A significant improvement in DA 3.0 a-wave ERG amplitude localized the improvement in rod function at the level of the photoreceptor.

CONCLUSIONS

This study demonstrates that a significant proportion of rod dysfunction in L-ORD can be reversed by extended dark adaptation and suggests that an abnormality of the visual cycle contributes to the pathogenesis of the disease. These findings would suggest that some retinal function could be restored, even in advanced cases of the disease if a suitable treatment is found.

Application of Whole Exome Sequencing in Six Families with an Initial Diagnosis of Autosomal Dominant Retinitis Pigmentosa: Lessons Learned

This study aimed to identify the genetics underlying dominant forms of inherited retinal dystrophies using whole exome sequencing (WES) in six families extensively screened for known mutations or genes. Thirty-eight individuals were subjected to WES. Causative variants were searched among single nucleotide variants (SNVs) and insertion/deletion variants (indels) and whenever no potential candidate emerged, copy number variant (CNV) analysis was performed. Variants or regions harboring a candidate variant were prioritized and segregation of the variant with the disease was further assessed using Sanger sequencing in case of SNVs and indels, and quantitative PCR (qPCR) for CNVs. SNV and indel analysis led to the identification of a previously reported mutation in PRPH2. Two additional mutations linked to different forms of retinal dystrophies were identified in two families: a known frameshift deletion in RPGR, a gene responsible for X-linked retinitis pigmentosa and p.Ser163Arg in C1QTNF5 associated with Late-Onset Retinal Degeneration. A novel heterozygous deletion spanning the entire region of PRPF31 was also identified in the affected members of a fourth family, which was confirmed with qPCR. This study allowed the identification of the genetic cause of the retinal dystrophy and the establishment of a correct diagnosis in four families, including a large heterozygous deletion in PRPF31, typically considered one of the pitfalls of this method. Since all findings in this study are restricted to known genes, we propose that targeted sequencing using gene-panel is an optimal first approach for the genetic screening and that once known genetic causes are ruled out, WES might be used to uncover new genes involved in inherited retinal dystrophies.

Phenotypic findings in C1QTNF5 retinopathy (late-onset retinal degeneration)

PURPOSE

To describe the ocular and electrophysiological phenotype of four patients with late-onset retinal degeneration (LORD).

METHODS

Clinical examination, fundus and anterior segment photography, fundus autofluorescence imaging and spectral domain optical coherence tomography (SD-OCT) were performed. Three patients underwent pattern and full-field electroretinography (ERG). Patient DNA was screened for the c.686C>G, p.Ser163Arg mutation in C1QTNF5.

RESULTS

All affected individuals had a family history suggestive of autosomal dominant inheritance with full penetrance. Molecular analysis identified a heterozygous c.686C>G, p.Ser163Arg mutation in C1QTNF5 in DNA from all four affected probands. All four patients presented in their 50s with nyctalopia and developed central visual loss in their 60s. Peripupillary iris atrophy and long anterior zonular insertions were present in three of four patients. Dilated fundus examination revealed scalloped areas of retinal pigment epithelium (RPE) atrophy in the mid-periphery and widespread atrophy in the posterior pole. Full-field ERGs were consistent with rod-cone dystrophy with pattern ERG evidence of severe macular involvement. SD-OCT revealed widespread loss of the photoreceptors with absence of the inner/outer segment junction line and concurrent thinning of the outer nuclear layer. Diffuse choroidal thinning, mainly affecting the inner choroid with loss of the choriocapillaris, was observed.

CONCLUSION

C1QTNF5 retinopathy is an autosomal dominant LORD resulting in a complex ocular phenotype involving the RPE and ciliary epithelium. SD-OCT findings revealed widespread photoreceptor loss and diffuse choroidal thinning.