title: Gene replacement therapy rescues photoreceptor degeneration in a murine model of Leber congenital amaurosis lacking RPGRIP.
abstract: OBJECTIVE
  Retinitis pigmentosa GTPase regulator (RPGR) is a photoreceptor protein anchored in the connecting cilia by an RPGR-interacting protein (RPGRIP). Loss of RPGRIP causes Leber congenital amaurosis (LCA), a severe form of photoreceptor degeneration. The current study was an investigation of whether somatic gene replacement could rescue degenerating photoreceptors in a murine model of LCA due to a defect in RPGRIP.
  
  
  METHODS
  An RPGRIP expression cassette, driven by a mouse opsin promoter, was packaged into recombinant adeno-associated virus (AAV). The AAV vector was delivered into the right eyes of RPGRIP(-/-) mice by a single subretinal injection into the superior hemisphere. The left eyes received a saline injection as a control. Full-field electroretinograms (ERGs) were recorded from both eyes at 2, 3, 4, and 5 months after injection. After the final follow-up, retinas were analyzed by immunostaining or by light and electron microscopy.
  
  
  RESULTS
  Delivery of the AAV vector led to RPGRIP expression and restoration of normal RPGR localization at the connecting cilia. Photoreceptor preservation was evident by a thicker cell layer and well-developed outer segments in the treated eyes. Rescue was more pronounced in the superior hemisphere coincident with the site of delivery. Functional preservation was demonstrated by ERG.
  
  
  CONCLUSIONS
  AAV-mediated RPGRIP gene replacement preserves photoreceptor structure and function in a mouse model of LCA, despite ongoing cell loss at the time of intervention. These results indicate that gene replacement therapy may be effective in patients with LCA due to a defect in RPGRIP and suggest that further preclinical development of gene therapy for this disorder is warranted.
authors.affiliation: Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA.
authors.forename: Basil S
authors.initials: BS
authors.lastname: Pawlyk
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Smith
authors.forename: Prateek K
authors.initials: PK
authors.lastname: Buch
authors.forename: Michael
authors.initials: M
authors.lastname: Adamian
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Hong
authors.forename: Michael A
authors.initials: MA
authors.lastname: Sandberg
authors.forename: Robin R
authors.initials: RR
authors.lastname: Ali
authors.forename: Tiansen
authors.initials: T
authors.lastname: Li
mesh_terms: D000818:Animals; D001766:Blindness / Q000151:congenital / Q000378:metabolism / Q000628:therapy*; D003598:Cytoskeletal Proteins; D000229:Dependovirus / Q000235:genetics; D004195:Disease Models, Animal; D004596:Electroretinography; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000502:physiology*; D015316:Genetic Therapy; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism* / Q000648:ultrastructure; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012162:Retinal Degeneration / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D017299:Rod Opsins / Q000235:genetics; D014162:Transfection
chemical_list: D003598:Cytoskeletal Proteins; D005136:Eye Proteins; D011506:Proteins; C099929:RPGR protein, human; C415903:RPGRIP1 protein, human; D017299:Rod Opsins; D049452:Green Fluorescent Proteins