Clinicopathologic Effects of Mutant GUCY2D in Leber Congenital Amaurosis

William Penn University, Filadelfia, Pennsylvania, United States
Ophthalmology (Impact Factor: 6.14). 04/2003; 110(3):549-58. DOI: 10.1016/S0161-6420(02)01757-8
Source: PubMed


To study the retinal degeneration in an 11 -year-old patient with Leber congenital amaurosis (LCA) caused by mutation in GUCY2D.
Comparative human tissue study.
Two subjects with LCA; postmortem eye from one LCA patient and three normal donors.
Clinical and visual function studies were performed between the ages of 6 and 10 years in the LCA eye donor and at age 6 in an affected sibling. Genomic DNA was screened for mutations in known LCA genes. The retina of the 11 -year-old subject with LCA was compared with normal retinas from donors age 3 days, 18 years, and 53 years. The tissues were processed for histopathologic studies and immunofluorescence with retinal cell-specific antibodies.
Vision in both siblings at the ages examined was limited to severely impaired cone function. Mutation in the GUCY2D gene was identified in both siblings. Histopathologic study revealed rods and cones without outer segments in the macula and far periphery. The cones formed a monolayer of cell bodies, but the rods were clustered and had sprouted neurites in the periphery. Rods and cones were not identified in the midperipheral retina. The inner nuclear layer appeared normal in thickness throughout the retina, but ganglion cells were reduced in number.
An 11-year-old subject with LCA caused by mutant GUCY2D had only light perception but retained substantial numbers of cones and rods in the macula and far periphery. The finding of numerous photoreceptors at this age may portend well for therapies designed to restore vision at the photoreceptor level.

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Available from: Artur Cideciyan, Oct 04, 2015
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    • "While there is general consensus that LCA1 is associated with severely attenuated or ablated ERG (Perrault et al., 1999b, 2000; Hanein et al., 2004; Yzer et al., 2006; den Hollander et al., 2008), reports on the extent of photoreceptor degeneration associated with this form of LCA have been conflicting (Milam et al., 2003; Porto et al., 2003; Simonelli et al., 2007; Pasadhika et al., 2010). The most thorough clinical characterization of LCA1 performed to date focused on a cohort of patients ranging in age from 6 months to 37 years with different mutations in GUCY2D and has provided new insight on the effects of retGC1 deficiency on retinal structure and function (Jacobson et al., 2013). "
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    ABSTRACT: Vertebrate species possess two retinal guanylate cyclases (retGC1 and retGC2) and at least two guanylate cyclase activating proteins (GCAPs), GCAP1 and GCAP2. GCAPs function as Ca(2+) sensors that regulate the activity of guanylate cyclases. Together, these proteins regulate cGMP and Ca(2+) levels within the outer segments of rod and cone photoreceptors. Mutations in GUCY2D, the gene that encodes retGC1, are a leading cause of the most severe form of early onset retinal dystrophy, Leber congenital amaurosis (LCA1). These mutations, which reduce or abolish the ability of retGC1 to replenish cGMP in photoreceptors, are thought to lead to the biochemical equivalent of chronic light exposure in these cells. In spite of this, the majority of LCA1 patients retain normal photoreceptor laminar architecture aside from foveal cone outer segment abnormalities, suggesting they may be good candidates for gene replacement therapy. Work began in the 1980s to characterize multiple animal models of retGC1 deficiency. 34 years later, all models have been used in proof of concept gene replacement studies toward the goal of developing a therapy to treat GUCY2D-LCA1. Here we use the results of these studies as well as those of recent clinical studies to address specific questions relating to clinical application of a gene therapy for treatment of LCA1.
    Frontiers in Molecular Neuroscience 05/2014; 7:43. DOI:10.3389/fnmol.2014.00043 · 4.08 Impact Factor
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    • "Mutations in Gucy2d account for as many as 20% of all cases of LCA making it one of the leading causes of this disease [1],[6],[7] The number of patients affected by LCA1 is approximately double that affected by the well known RPE65 version of LCA (LCA2) [8],[9]. Diagnosis of LCA1 is typically made within the first few months of life and is characterized by severely impaired vision, extinguished electroretinogram (ERG) and pendular nystagmus [8], [10]. "
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    ABSTRACT: Recessive mutations in guanylate cyclase-1 (Gucy2d) are associated with severe, early onset Leber congenital amaurosis-1(LCA1). Gucy2d encodes guanylate cyclase (GC1) is expressed in photoreceptor outer segment membranes and produces cGMP in these cells. LCA1 patients present in infancy with severely impaired vision and extinguished electroretinogram (ERG) but retain some photoreceptors in both their macular and peripheral retina for years. Like LCA1 patients, loss of cone function in the GC1 knockout (GC1KO) mouse precedes cone degeneration. The purpose of this study was to test whether delivery of functional GC1 to cone cells of the postnatal GC1KO mouse could restore function to these cells. Serotype 5 AAV vectors containing either a photoreceptor-specific, rhodopsin kinase (hGRK1) or ubiquitous (smCBA) promoter driving expression of wild type murine GC1 were subretinally delivered to one eye of P14 GC1KO mice. Visual function (ERG) was analyzed in treated and untreated eyes until 3 months post injection. AAV-treated, isogenic wild type and uninjected control mice were evaluated for restoration of visual behavior using optomotor testing. At 3 months post injection, all animals were sacrificed, and their treated and untreated retinas assayed for expression of GC1 and localization of cone arrestin. Cone-mediated function was restored to treated eyes of GC1KO mice (ERG amplitudes were approximately 45% of normal). Treatment effect was stable for at least 3 months. Robust improvements in cone-mediated visual behavior were also observed, with responses of treated mice being similar or identical to that of wild type mice. AAV-vectored GC1 expression was found in photoreceptors and cone cells were preserved in treated retinas. This is the first demonstration of gene-based restoration of both visual function/vision-elicited behavior and cone preservation in a mammalian model of GC1 deficiency. Importantly, results were obtained using a well characterized, clinically relevant AAV vector. These results lay the ground work for the development of an AAV-based gene therapy vector for the treatment of LCA1.
    PLoS ONE 06/2010; 5(6):e11306. DOI:10.1371/journal.pone.0011306 · 3.23 Impact Factor
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    • "Other procedures like fundus autofluorescence and OCT provide highly variable findings further supporting the fact that LCA shelters a wide range of genespecific pathologic changes. Additionally, OCT studies suggest that in most cases, and despite retinal remodeling, photoreceptors remain viable even in late disease stages (Milam et al. 2003, Cideciyan et al. 2007, Jacobson et al. 2007). "
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