title: Functional and behavioral restoration of vision by gene therapy in the guanylate cyclase-1 (GC1) knockout mouse.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, Florida, United States of America. shaire@ufl.edu
authors.forename: Shannon E
authors.initials: SE
authors.lastname: Boye
authors.forename: Sanford L
authors.initials: SL
authors.lastname: Boye
authors.forename: Jijing
authors.initials: J
authors.lastname: Pang
authors.forename: Renee
authors.initials: R
authors.lastname: Ryals
authors.forename: Drew
authors.initials: D
authors.lastname: Everhart
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Umino
authors.forename: Andy W
authors.initials: AW
authors.lastname: Neeley
authors.forename: Joseph
authors.initials: J
authors.lastname: Besharse
authors.forename: Robert
authors.initials: R
authors.lastname: Barlow
authors.forename: William W
authors.initials: WW
authors.lastname: Hauswirth
mesh_terms: D000818:Animals; D001483:Base Sequence; D001522:Behavior, Animal; D017931:DNA Primers; D000229:Dependovirus / Q000235:genetics; D004596:Electroretinography; D015316:Genetic Therapy; D005822:Genetic Vectors; D006162:Guanylate Cyclase / Q000235:genetics*; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D016133:Polymerase Chain Reaction; D011956:Receptors, Cell Surface / Q000235:genetics*; D019076:Transgenes; D014786:Vision Disorders / Q000503:physiopathology / Q000628:therapy*; D014792:Visual Acuity
chemical_list: D017931:DNA Primers; D011956:Receptors, Cell Surface; C110715:guanylate cyclase 1; D006162:Guanylate Cyclase