Pascal Escher

Inherited retinal dystrophies (IRDs) are characterized by their high clinical and genetic heterogeneity. Despite significant advances in the identification of genes associated with IRDs, many individuals and families still have not received a definite molecular diagnosis. Here, we performed clinical examinations and conducted genetic testing in five families with IRD. Whole exome sequencing in the five index cases revealed a heterozygous missense variant, c.209G > A, p.(Gly70Glu) in the ARL3 gene (NM_004311.4). A de novo occurrence was demonstrated in one affected individual and autosomal dominant inheritance in nine affected individuals from four families. Their phenotypes displayed variable expressivity, and ranged from rod-cone to cone-rod dystrophy with photophobia. Human induced pluripotent stem cells (hiPSCs) were generated from dermal fibroblasts from the individual with the de novo ARL3 variant and were differentiated to retinal pigment epithelium cells (RPE) and retinal organoids. Immunofluorescence analyses in these models showed decreased INPP5E localization within the cilia of RPE and connecting cilia of retinal organoids, as well as reduced PDE6⍺ in the organoid outer segments, suggesting that the p.(Gly70Glu) variant causes IRD by defective lipidated protein transport in photoreceptors and/or RPE. This is the first study of ARL3 dysfunction in human retinal cells, highlighting its importance for retinal homeostasis, as well as a variability in the clinical presentation of ARL3-associated IRD.

Chromosomal abnormalities on the short arm of chromosome 2 in the region p11.2 have been associated with developmental delay, intellectual disability, facial anomalies, abnormal ears, skeletal and genital malformations. Here we describe a patient with a de novo interstitial heterozygous microdeletion on the short arm of chromosome 2 in the region p11.2-p12. He presents with facial dysmorphism characterized by a broad and low root of the nose and low-set protruding ears. Clinical examinations during follow-up visits revealed congenital pendular nystagmus, decreased visual acuity and psychomotor development disorder including intellectual disability. The heterozygous 5 Mb-microdeletion was characterized by an array CGH (Comparative Genomic Hybridization) analysis. In the past two decades, nine patients with microdeletions in this region have been identified by array CGH analysis and were reported in the literature. All these patients show psychomotor development disorder and outer and/or inner ear anomalies. In addition, most of the patients have mild to severe intellectual disability and show facial malformations. We reviewed the literature on PubMed and OMIM using the gene/loci names as search terms in an attempt to identify correlations between genes located within the heterozygous microdeletion and the clinical phenotype of the patient, in order to define a recognizable phenotype for the 2p11.2p12 microdeletion syndrome. We discuss additional symptoms that are not systematically present in all patients and contribute to a heterogeneous clinical presentation of this microdeletion syndrome.

The photoreceptor-specific nuclear receptor Nr2e3 is not expressed in Nr2e3^rd7/rd7 mice, a mouse model of the recessively inherited retinal degeneration enhanced S-cone sensitivity syndrome (ESCS). We characterized in detail C57BL/6J Nr2e3^rd7/rd7 mice in vivo by fundus photography, optical coherence tomography and fluorescein angiography and, post mortem, by histology and immunohistochemistry. White retinal spots and so-called ‘rosettes’ first appear at postnatal day (P) 12 in the dorsal retina and reach maximal expansion at P21. The highest density in ‘rosettes’ is observed within a region located between 100 and 350 µM from the optic nerve head. ‘Rosettes’ disappear between 9 to 12 months. Non-apoptotic cell death markers are detected during the slow photoreceptor degeneration, at a rate of an approximately 3% reduction of outer nuclear layer thickness per month, as observed from 7 to 31 months of age. In vivo analysis of Nr2e3^rd7/rd7 Cx3cr1^gfp/+ retinas identified microglial cells within ‘rosettes’ from P21 on. Subretinal macrophages were observed in vivo and by confocal microscopy earliest in 12-months-old Nr2e3^rd7/rd7 retinas. At P21, S-opsin expression and the number of S-opsin expressing dorsal cones was increased. The dorso-ventral M-cone gradient was present in Nr2e3^rd7/rd7 retinas, but M-opsin expression and M-opsin expressing cones were decreased. Retinal vasculature was normal.

Purpose: The purpose of this study was to investigate the clinical and genetic features of a man and his daughter with posterior polymorphous corneal dystrophy (PPCD), referred to our clinic for Descemet membrane endothelial keratoplasty. No other known relatives were affected. Methods: Ophthalmic examination and histology, including electron microscopy, were performed. Genetic testing was conducted by means of whole exome sequencing, and variant analysis was achieved by using an internal in silico pipeline. Molecular tests included a dual-luciferase assay. Results: Slowly progressive blurred vision was reported from childhood by the daughter. The father's symptoms started at age 55. Best-corrected visual acuity was reduced in both patients (0.2–0.4). Slit-lamp examination in both patients revealed bilateral corneal clouding with gray endothelial lesions; other family members had no ophthalmological signs. Descemet membrane endothelial keratoplasty was performed uneventfully in both patients. Histology showed thickened Descemet membrane and abnormal endothelium resembling epithelial-like cells. Both patients carried the OVOL2 5′ untranslated region NM_021220.4.c.-61G>A variant in the heterozygous state. This change was associated with increased promoter activity and was not present in the unaffected members of the family. Conclusions: The 5′ untranslated region mutation c.-61G>A in OVOL2 has been previously found in 1 individual with PPCD1 and reported as a variant of unknown significance because of insufficient evidence supporting its pathogenicity. Identification of the second family with 2 individuals affected by PPCD1 carrying this change, together with functional data, provides further proofs that it is disease-causing.

We genetically characterized 22 Swiss patients who had been diagnosed with Stargardt disease after clinical examination. We identified in 11 patients (50%) pathogenic bi-allelic ABCA4 variants, c.1760+2T>C and c.4496T>C being novel. The dominantly inherited pathogenic ELOVL4 c.810C>G p.(Tyr270*) and PRPH2-c.422A>G p.(Tyr141Cys) variants were identified in eight (36%) and three patients (14%), respectively. All patients harboring the ELOVL4 c.810C>G p.(Tyr270*) variant originated from the same small Swiss area, identifying a founder mutation. In the ABCA4 and ELOVL4 cohorts, the clinical phenotypes of “flecks”, “atrophy”, and “bull’s eye like” were observed by fundus examination. In the small number of patients harboring the pathogenic PRPH2 variant, we could observe both “flecks” and “atrophy” clinical phenotypes. The onset of disease, progression of visual acuity and clinical symptoms, inheritance patterns, fundus autofluorescence, and optical coherence tomography did not allow discrimination between the genetically heterogeneous Stargardt patients. The genetic heterogeneity observed in the relatively small Swiss population should prompt systematic genetic testing of clinically diagnosed Stargardt patients. The resulting molecular diagnostic is required to prevent potentially harmful vitamin A supplementation, to provide genetic counseling with respect to inheritance, and to schedule appropriate follow-up visits in the presence of increased risk of choroidal neovascularization.

Purpose: To investigate the clinical and genetic features of a man and his daughter with Posterior polymorphous corneal dystrophy 1 (PPCD1), referred to our clinic for Descemet's Membrane Endothelial Keratoplasty (DMEK). No other known relatives were affected, including the index patient's spouse and their son.Methods: Clinical examination was performed by best‐corrected visual acuity (BCVA) testing, slit‐lamp examination (SLE), anterior‐segment optical coherency tomography (OCT) and specular microscopy. Histologic testing and electron microscopy were done. Genetic testing was carried out by means of Whole‐Exome Sequencing (WES), and variant analysis was achieved by an internal in silico pipeline.Results: Slowly progressive blurred vision was reported from childhood by the daughter. The father's symptoms started approximately ten years prior to consultation. BCVA was 0.2 in both eyes in the father and 0.2/0.4 in the right/left eye in the daughter. SLE in both patients revealed bilateral corneal clouding with focal grey endothelial spots. Corneal edema with Descemet's folds was present. DMEK was performed uneventfully. Histology and electron microscopy showed layered Descemet's membrane and pleomorphic endothelial cells with vacuoles but no microvilli. Genetic analysis revealed the c. ‐61G>A variant in the 5′UTR region of the OVOL2 gene heterozygously, in both patients. This change was not present in the unaffected members of the family.Conclusions: PPCD1 has been linked to mutations in the promoter and the 5′UTR region of OVOL2. The NM_021220.4:c.‐61G>A DNA change was previously reported as a variant of unknown pathogenicity, despite having been identified in another patient with PPCD1. Based on perfect familial co‐segregation, complete absence of this change in all public databases of normal controls, and its identification in two additional individuals with PPCD1, we conclude that c.‐61G>A is a truly pathogenic mutation for this condition.

(2019). Comment: Novel mutations in the OPN1LW and NR2R3 genes in a patient with blue cone monochromacy. Ophthalmic Genetics. Ahead of Print.

Microglia-associated inflammation is closely related to the pathogenesis of various retinal diseases such as uveitis and diabetic retinopathy, which are associated with increased vascular permeability. In this study, we investigated the effect of systemic lipopolysaccharide (LPS) exposure to activation and proliferation of retinal microglia /macrophages. Balb/c and Cx3cr1gfp/+ mice were challenged with LPS (1 mg/kg) daily for four consecutive days. For microglia depletion, mice were treated with colony-stimulating factor 1 receptor (CSF-1R) inhibitor PLX5622 1 week before the first LPS challenge and until the end of the experiment. In vivo imaging of the retina was performed on days 4 and 7 after the first LPS challenge, using optical coherence tomography and fluorescein angiography. Flow cytometry analysis, retinal whole mount, and retinal sections were used to investigate microglia and macrophage infiltration and proliferation after LPS challenge. Cytokines were analyzed in the blood as well as in the retina. Data analysis was performed using unpaired t tests, repeated measures one-way ANOVA, or ordinary one-way ANOVA followed by Tukey’s post hoc analysis. Kruskal-Wallis test followed by Dunn’s multiple comparison tests was used for the analysis of non-normally distributed data. Repeated LPS challenge led to activation and proliferation of retinal microglia, infiltration of monocyte-derived macrophages into the retina, and breakdown of the blood-retina barrier (BRB) accompanied by accumulation of sub-retinal fluid. Using in vivo imaging, we show that the breakdown of the BRB is highly reproducible but transitory. Acute but not chronic systemic exposure to LPS triggered a robust release of inflammatory mediators in the retina with minimal effects in the blood plasma. Inhibition of the CSF-1R by PLX5622 resulted in depletion of retinal microglia, suppression of cytokine production in the retina, and prevention of BRB breakdown. These findings suggest that microglia/macrophages play an important role in the pathology of retinal disorders characterized by breakdown of the BRB, and suppression of their activation may be a potential therapeutic target for such retinopathies.