Institute for Research in Ophthalmology IRO

Sion, Switzerland

Institute for Research in Ophthalmology IRO

Sion, Switzerland
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Gillespie R.L.,University of Manchester | Urquhart J.,University of Manchester | Lovell S.C.,University of Manchester | Biswas S.,University of Manchester | And 7 more authors.
Investigative Ophthalmology and Visual Science | Year: 2015

PURPOSE. To define the phenotypic manifestation, confirm the genetic basis, and delineate the pathogenic mechanisms underlying an oculoauricular syndrome (OAS). METHODS. Two individuals from a consanguineous family underwent comprehensive clinical phenotyping and electrodiagnostic testing (EDT). Genome-wide microarray analysis and Sanger sequencing of the candidate gene were used to identify the likely causal variant. Protein modelling, Western blotting, and dual luciferase assays were used to assess the pathogenic effect of the variant in vitro. RESULTS. Complex developmental ocular abnormalities of congenital cataract, anterior segment dysgenesis, iris coloboma, early-onset retinal dystrophy, and abnormal external ear cartilage presented in the affected family members. Genetic analyses identified a homozygous c.650A>C; p.(Gln217Pro) missense mutation within the highly conserved homeodomain of the H6 family homeobox 1 (HMX1) gene. Protein modelling predicts that the variant may have a detrimental effect on protein folding and/or stability. In vitro analyses were able to demonstrate that the mutation has no effect on protein expression but adversely alters function. CONCLUSIONS. Oculoauricular syndrome is an autosomal recessive condition that has a profound effect on the development of the external ear, anterior segment, and retina, leading to significant visual loss at an early age. This study has delineated the phenotype and confirmed HMX1 as the gene causative of OAS, enabling the description of only the second family with the condition. HMX1 is a key player in ocular development, possibly in both the pathway responsible for lens and retina development, and via the gene network integral to optic fissure closure. © 2015 The Association for Research in Vision and Ophthalmology, Inc.

Munier F.L.,University of Lausanne | Munier F.L.,Institute for Research in Ophthalmology IRO | Gaillard M.-C.,University of Lausanne | Balmer A.,University of Lausanne | Beck-Popovic M.,University of Lausanne
Saudi Journal of Ophthalmology | Year: 2013

For decades intravitreal chemotherapy (IViC) remained virtually banished from the therapeutic armamentarium against retinoblastoma, except as a heroic attempt of salvage before enucleation in only eyes with refractory vitreous seeding. Very recently, we have initiated a reappraisal of this route of administration by (1) profiling eligibility criteria, (2) describing a safety-enhanced injection procedure, (3) adjusting the tumoricidal dose of melphalan, and (4) reporting an unprecedented efficacy in terms of tumor control of vitreous seeding. Since then, intravitreal chemotherapy is being progressively implemented worldwide with great success, but still awaits formal validation by the ongoing prospective phase II clinical trial. As far as preliminary results are concerned, IViC appears to achieve complete vitreous response in 100% of the 35 newly recruited patients irrespective of the previous treatment regimen, including external beam radiotherapy and/or intra-arterial melphalan. In other words, vitreous seeding, still considered as the major cause of primary and secondary enucleation, can now be controlled by IViC. However, sterilization of vitreous seeding does not necessarily translate into eye survival, unless the retinal source of the seeds receives concomitant therapy. In conclusion, IViC, an unsophisticated and cost-effective treatment, is about to revolutionize the eye survival prognosis of vitreous disease in advanced retinoblastoma. © 2013 Production and hosting by Elsevier B.V.

Schorderet D.F.,Institute for Research in Ophthalmology IRO | Schorderet D.F.,University of Lausanne | Schorderet D.F.,Ecole Polytechnique Federale de Lausanne | Iouranova A.,Ecole Polytechnique Federale de Lausanne | And 4 more authors.
BioMed Research International | Year: 2013

The molecular diagnosis of retinal dystrophies is difficult because of the very important number of genes implicated and is rarely helped by genotype-phenotype correlations. This prompted us to develop IROme, a custom designed in solution-based targeted exon capture assay (SeqCap EZ Choice library, Roche NimbleGen) for 60 retinitis pigmentosa-linked genes and three candidate genes (942 exons). Pyrosequencing was performed on a Roche 454 GS Junior benchtop high-throughput sequencing platform. In total, 23 patients affected by retinitis pigmentosa were analyzed. Per patient, 39.6 Mb were generated, and 1111 sequence variants were detected on average, at a median coverage of 17-fold. After data filtering and sequence variant prioritization, disease-causing mutations were identified in ABCA4, CNGB1, GUCY2D, PROM1, PRPF8, PRPF31, PRPH2, RHO, RP2, and TULP1 for twelve patients (55%), ten mutations having never been reported previously. Potential mutations were identified in 5 additional patients, and in only 6 patients no molecular diagnosis could be established (26%). In conclusion, targeted exon capture and next-generation sequencing are a valuable and efficient approach to identify disease-causing sequence variants in retinal dystrophies. © 2013 Daniel F. Schorderet et al.

Emery M.,Institute for Research in Ophthalmology IRO | Emery M.,University of Lausanne | Schorderet D.F.,Institute for Research in Ophthalmology IRO | Schorderet D.F.,University of Lausanne | And 3 more authors.
PLoS ONE | Year: 2011

Background: Glucose is the most important metabolic substrate of the retina and maintenance of normoglycemia is an essential challenge for diabetic patients. Glycemic excursions could lead to cardiovascular disease, nephropathy, neuropathy and retinopathy. A vast body of literature exists on hyperglycemia namely in the field of diabetic retinopathy, but very little is known about the deleterious effect of hypoglycemia. Therefore, we decided to study the role of acute hypoglycemia in mouse retina. Methodology/Principal Findings: To test effects of hypoglycemia, we performed a 5-hour hyperinsulinemic/hypoglycemic clamp; to exclude an effect of insulin, we made a hyperinsulinemic/euglycemic clamp as control. We then isolated retinas from each group at different time-points after the clamp to analyze cells apoptosis and genes regulation. In parallel, we used 661W photoreceptor cells to confirm in vivo results. We showed herein that hypoglycemia induced retinal cell death in mouse via caspase 3 activation. We then tested the mRNA expression of glutathione transferase omega 1 (Gsto1) and glutathione peroxidase 3 (Gpx3), two genes involved in glutathione (GSH) homeostasis. The expression of both genes was up-regulated by low glucose, leading to a decrease of reduced glutathione (GSH). In vitro experiments confirmed the low-glucose induction of 661W cell death via superoxide production and activation of caspase 3, which was concomitant with a decrease of GSH content. Moreover, decrease of GSH content by inhibition with buthionine sulphoximine (BSO) at high glucose induced apoptosis, while complementation with extracellular glutathione ethyl ester (GSHee) at low glucose restored GSH level and reduced apoptosis. Conclusions/Significance: We showed, for the first time, that acute insulin-induced hypoglycemia leads to caspase 3-dependant retinal cell death with a predominant role of GSH content. © 2011 Emery et al.

Tiab L.,Institute for Research in Ophthalmology IRO | Largueche L.,Hedi Rais Institute of Ophthalmology | Largueche L.,Tunis el Manar University | Chouchane I.,Hedi Rais Institute of Ophthalmology | And 8 more authors.
Molecular Vision | Year: 2013

Purpose: Retinitis pigmentosa (RP; MIM 268000) is a hereditary disease characterized by poor night vision and progressive loss of photoreceptors, eventually leading to blindness. This degenerative process primarily affects peripheral vision due to the loss of rods. Autosomal recessive RP (arRP) is clinically and genetically heterogeneous. It has been associated with mutations in different genes, including CRB1 (crumbs homolog 1). The aim of this study was to determine the causative gene in a Tunisian patient with arRP born to non-consanguineous parents. Methods: Four accessible family members were included. They underwent full ophthalmic examination with best-corrected Snellen visual acuity, fundus photography and fluorescein angiography. Haplotype analysis was used to evaluate homozygosity in the family to 20 arRP loci. All exons and intron-exon junctions of candidate genes not excluded by haplotype analysis were PCR amplified and directly sequenced. Results: The proband was a 43-year-old female patient. Best-corrected visual acuity was 20/63 (right eye) and 20/80 (left eye). Visual loss began during the third decade. Funduscopic examination and fluorescein angiography revealed typical advanced RP changes with bone spicule-like pigment deposits in the posterior pole and the midperiphery along with retinal atrophy, narrowing of the vessels, and waxy optic discs. Haplotype analysis revealed homozygosity with microsatellite markers D1S412 and D1S413 on chromosome 1q31.3. These markers flanked CRB1. Our results excluded linkage of all the other arRP loci/genes tested. Sequencing of the 12 coding exons and splice sites of CRB1 disclosed a homozygous missense mutation in exon 7 at nucleotide c. 2291G>A, resulting in an arginine to histidine substitution (p.R764H). Conclusions: R764H is a novel mutation associated with CRB1-related arRP. Previously, an R764C mutation was reported. Extending the mutation spectrum of CRB1 with additional families is important for genotype-phenotype correlations and characterization of the scope of mutation. © 2013 Molecular Vision.

PubMed | Hedi Rais Institute of Ophthalmology and Institute for Research in Ophthalmology IRO
Type: | Journal: Scientific reports | Year: 2016

Retinal dystrophies (RD) are a rare genetic disorder with high genetic heterogeneity. This study aimed at identifying disease-causing variants in fifteen consanguineous Tunisian families. Full ophthalmic examination was performed. Index patients were subjected to IROme analysis or whole exome sequencing followed by homozygosity mapping. All detected variations were confirmed by direct Sanger sequencing. Mutation analysis in our patients revealed two compound heterozygous mutations p.(R91W);(V172D) in RPE65, and five novel homozygous mutations: p.R765C in CNGB1, p.H337R in PDE6B, splice site variant c.1129-2A>G and c.678_681delGAAG in FAM161A and c.1133+3_1133+6delAAGT in CERKL. The latter mutation impacts pre-mRNA splicing of CERKL. The other changes detected were six previously reported mutations in CNGB3 (p.R203*), ABCA4 (p.W782*), NR2E3 (p.R311Q), RPE65 (p.H182Y), PROM1 (c.1354dupT) and EYS (c.5928-2A>G). Segregation analysis in each family showed that all affected individuals were homozygotes and unaffected individuals were either heterozygote carriers or homozygous wild type allele. These results confirm the involvement of a large number of genes in RD in the Tunisian population.

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