Clinical and Molecular Genetics of Leber's Congenital Amaurosis: A Multicenter Study of Italian Patients

Simonelli, Francesca; Ziviello, Carmela; Testa, Francesco; Rossi, Silvia; Fazzi, Elisa; Bianchi, Paolo Emilio; Fossarello, Maurizio; Signorini, Sabrina; Bertone, Chiara; Galantuomo, Silvana; Brancati, Francesco; Valente, Enza Maria; Ciccodicola, Alfredo; Rinaldi, E; Auricchio, Alberto; Banfi, Sandro

doi:10.1167/iovs.07-0068

Cited by 131 publications

(122 citation statements)

References 40 publications

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“…Because each blade of the propeller structure contributes a residue to the iron ion coordination system, substitutions in any sheet could displace the respective critical residue leading to disruption of iron ion binding. Missense mutations that result in substitutions of either the first or second shell iron ion ligands have been found in LCA patients (37)(38)(39), consistent with biochemical studies that demonstrated both first and second shell iron ion ligands are essential for RPE65 isomerase activity (4,40).…”

Section: Rpe65 In Retinal Diseasessupporting

confidence: 77%

Crystal structure of native RPE65, the retinoid isomerase of the visual cycle

Kiser

Golczak²,

Lodowski³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

141

232

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Vertebrate vision is maintained by the retinoid (visual) cycle, a complex enzymatic pathway that operates in the retina to regenerate the visual chromophore, 11-cis-retinal. A key enzyme in this pathway is the microsomal membrane protein RPE65. This enzyme catalyzes the conversion of all-trans-retinyl esters to 11-cis-retinol in the retinal pigment epithelium (RPE). Mutations in RPE65 are known to be responsible for a subset of cases of the most common form of childhood blindness, Leber congenital amaurosis (LCA). Although retinoid isomerase activity has been attributed to RPE65, its catalytic mechanism remains a matter of debate. Also, the manner in which RPE65 binds to membranes and extracts retinoid substrates is unclear. To gain insight into these questions, we determined the crystal structure of native bovine RPE65 at 2.14-Å resolution. The structural, biophysical, and biochemical data presented here provide the framework needed for an in-depth understanding of the mechanism of catalytic isomerization and membrane association, in addition to the role mutations that cause LCA have in disrupting protein function.isomerization ͉ metalloprotein ͉ monotopic membrane protein V ision begins when the 11-cis-retinylidene chromophore of rhodopsin is photoisomerized to all-trans-retinylidene, a process resulting in receptor activation and transduction of the light signal (1). After rhodopsin is photoactivated, it is no longer responsive to light, so for vision to continue, a trans-to-cis isomerization mechanism must be present to regenerate lightsensitive visual pigments. In vertebrates, after photoisomerization, all-trans-retinylidene is hydrolyzed from rhodopsin, reduced to all-trans-retinol, and transported to a tissue adjacent to the photoreceptor layer known as the retinal pigment epithelium (RPE), where enzymatic isomerization occurs (2). An RPEspecific, microsomal membrane protein with an apparent molecular mass of 65 kDa, known as RPE65, was determined to be responsible for trans-to-cis retinoid isomerase activity in the RPE (3-5). The importance of this protein in visual function is also evident from the observation that certain RPE65 mutations cause a form of the hereditary childhood blinding disease known as Leber congenital amaurosis (LCA) or the less severe, lateronset disease, retinitis pigmentosa (RP) (6-8).Based on sequence homology, RPE65 belongs to a family of carotenoid cleavage oxygenase (CCO) enzymes that oxidatively cleave ␤-carotene or apocarotenoids (9-11). However, RPE65 is distinct from all other members of this family in that it simultaneously cleaves and isomerizes all-trans-retinyl esters to 11-cisretinol and a fatty acid rather than oxidatively cleaving carotenoids (3-5, 11, 12). Unlike the reactions catalyzed by other CCO family members, there is no obvious role for molecular oxygen in RPE65 enzymology. The only family member with a known crystal structure is an apocarotenoid oxygenase from Synechocystis that is 25% identical and 42% homologous to human RPE65 (13). All members of this fa...

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Section: Rpe65 In Retinal Diseasessupporting

confidence: 77%

Crystal structure of native RPE65, the retinoid isomerase of the visual cycle

Kiser

Golczak²,

Lodowski³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

141

232

View full text Add to dashboard Cite

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“…In agreement with previous imaging studies (Simonelli et al 2007;Pasadhika et al 2010), Jacobson et al (2013) report that LCA1 patients retain normal photoreceptor laminar architecture aside from foveal cone outer segment abnormalities and, in a few patients, foveal cone loss. Outer nuclear layer and photoreceptor outer segment thickness measurements in the rod-dominant retina (i.e., outside the fovea) were normal in all patients evaluated.…”

Section: Patient Characterizationsupporting

confidence: 92%

“…Histopathological analysis of two postmortem retinas (a 26-wk-old preterm abortus and a 12-yr-old donor) revealed signs of photoreceptor degeneration in both rods and cones Porto et al 2003). Later studies using state of the art, in-life imaging (i.e., optical coherence tomography) revealed no obvious degeneration in patients as old as 53 years of age (Simonelli et al 2007;Pasadhika et al 2010).…”

Section: Patient Characterizationmentioning

confidence: 95%

Leber Congenital Amaurosis Caused by Mutations in GUCY2D

Boye

2014

Cold Spring Harbor Perspectives in Medicine

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“…LCA1 patients present in infancy with severely impaired vision and extinguished ERG despite a normal fundus and retained photoreceptors in both their macular and peripheral retina for decades. [39][40][41][42] There is relatively better maintenance of retinal structure in LCA1 patients than that seen in other forms of the disease. 42 Taken together, this suggests an important role for the zebrafish as an animal model on which rapid visual screening and retinal histology may offer a unique advantage in the study of GC1 disease through both gene knockdown or future studies of dominant gene supplementation.…”

Section: Discussionmentioning

confidence: 99%

Gucy2f zebrafish knockdown – a model for Gucy2d-related leber congenital amaurosis

et al. 2012

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Mutations in retinal-specific guanylate cyclase (Gucy2d) are associated with Leber congenital amaurosis-1 (LCA1). Zebrafish offer unique advantages relative to rodents, including their excellent color vision, precocious retinal development, robust visual testing strategies, low cost, relatively easy transgenesis and shortened experimental times. In this study we will demonstrate the feasibility of using gene-targeting in the zebrafish as a model for the photoreceptor-specific GUCY2D-related LCA1, by reporting the visual phenotype and retinal histology resulting from Gucy2f knockdown. Gucy2f zebrafish LCA-orthologous cDNA was identified and isolated by PCR amplification. Its expression pattern was determined by whole-mount in-situ hybridization and its function was studied by gene knockdown using two different morpholino-modified oligos (MO), one that blocks translation of Gucy2f and one that blocks splicing of Gucy2f. Visual function was assessed with an optomotor assay on 6-days-postfertilization larvae, and by analyzing changes in retinal histology. Gucy2f knockdown resulted in significantly lower vision as measured by the optomotor response compared with uninjected and control MO-injected zebrafish larvae. Histological changes in the Gucy2f-knockdown larvae included loss and shortening of cone and rod outer segments. A zebrafish model of Gucy2f-related LCA1 displays early visual dysfunction and photoreceptor layer dystrophy. This study serves as proof of concept for the use of zebrafish as a simple, inexpensive model with excellent vision on which further study of LCA-related genes is possible. Keywords: leber congenital amaurosis; animal model; GUCY2D; optomotor assay INTRODUCTION Leber congenital amaurosis (LCA) is a family of severe, early-onset, autosomal-recessive forms of pediatric blindness. LCA has been linked to more than 16 genes, often exhibiting clinical heterogeneity. 1,2 LCA1 is caused by mutations in the gene GUCY2D, which encodes the retinal Gucy2d-1 (GC1) and accounts for B20% of all cases of LCA. 3 LCA2 is caused by mutations in the RPE65 gene, which is expressed in the retinal pigment epithelium. Breakthrough research has demonstrated visual improvement following gene therapy trials in humans with LCA2. 4,5 Human trials relied on a decade of proof-of-concept studies in canine and rodent models. 6-8 Unlike LCA2, in which gene therapy is aimed at correcting an RPE defect, searching for gene therapy for LCA1 will involve an attempt at treating the photoreceptors. European Journal of Human GeneticsResearch in inherited retinal disease relies heavily on animal models, commonly mammals such as mice and dogs. These animal models have significant advantages, including the availability of knockout technology. Two specific drawbacks slow the applicability of rodent or canine models for study of relatively rare genetic diseases such as LCA and other retinal dystrophies. The first difficulty is the high cost and length of time required to create a new knockout line; thus, it is applicable only for comm...

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Clinical and Molecular Genetics of Leber's Congenital Amaurosis: A Multicenter Study of Italian Patients

Cited by 131 publications

References 40 publications

Crystal structure of native RPE65, the retinoid isomerase of the visual cycle

Crystal structure of native RPE65, the retinoid isomerase of the visual cycle

Leber Congenital Amaurosis Caused by Mutations in GUCY2D

Gucy2f zebrafish knockdown – a model for Gucy2d-related leber congenital amaurosis

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