title: Gene therapy rescues cone structure and function in the 3-month-old rd12 mouse: a model for midcourse RPE65 leber congenital amaurosis.
abstract: OBJECTIVE
  RPE65 function is necessary in the retinal pigment epithelium (RPE) to generate chromophore for all opsins. Its absence results in vision loss and rapid cone degeneration. Recent Leber congenital amaurosis type 2 (LCA with RPE65 mutations) phase I clinical trials demonstrated restoration of vision on RPE65 gene transfer into RPE cells overlying cones. In the rd12 mouse, a naturally occurring model of RPE65-LCA early cone degeneration was observed; however, some peripheral M-cones remained. A prior study showed that AAV-mediated RPE65 expression can prevent early cone degeneration. The present study was conducted to test whether the remaining cones in older rd12 mice can be rescued.
  
  
  METHODS
  Subretinal treatment with the scAAV5-smCBA-hRPE65 vector was initiated at postnatal day (P)14 and P90. After 2 months, electroretinograms were recorded, and cone morphology was analyzed by using cone-specific peanut agglutinin and cone opsin-specific antibodies.
  
  
  RESULTS
  Cone degeneration started centrally and spread ventrally, with cells losing cone-opsin staining before that for the PNA-lectin-positive cone sheath. Gene therapy starting at P14 resulted in almost wild-type M- and S-cone function and morphology. Delaying gene-replacement rescued the remaining M-cones, and most important, more M-cone opsin-positive cells were identified than were present at the onset of gene therapy, suggesting that opsin expression could be reinitiated in cells with cone sheaths.
  
  
  CONCLUSIONS
  The results support and extend those of the previous study that gene therapy can stop early cone degeneration, and, more important, they provide proof that delayed treatment can restore the function and morphology of the remaining cones. These results have important implications for the ongoing LCA2 clinical trials.
authors.affiliation: School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, People's Republic of China.
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.forename: Wensheng
authors.initials: W
authors.lastname: Li
authors.forename: Xufeng
authors.initials: X
authors.lastname: Dai
authors.forename: Fansheng
authors.initials: F
authors.lastname: Kong
authors.forename: Qinxiang
authors.initials: Q
authors.lastname: Zheng
authors.forename: Xiangtian
authors.initials: X
authors.lastname: Zhou
authors.forename: Fan
authors.initials: F
authors.lastname: Lü
authors.forename: Bo
authors.initials: B
authors.lastname: Chang
authors.forename: Bärbel
authors.initials: B
authors.lastname: Rohrer
authors.forename: William W
authors.initials: WW
authors.lastname: Hauswirth
authors.forename: Jia
authors.initials: J
authors.lastname: Qu
authors.forename: Ji-jing
authors.initials: JJ
authors.lastname: Pang
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D055358:Cone Opsins / Q000378:metabolism; D000229:Dependovirus / Q000235:genetics*; D004195:Disease Models, Animal; D004596:Electroretinography; D005136:Eye Proteins / Q000235:genetics*; D019084:Fluorescent Antibody Technique, Indirect; D015316:Genetic Therapy; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000235:genetics; D057130:Leber Congenital Amaurosis / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008856:Microscopy, Fluorescence; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase
chemical_list: D002352:Carrier Proteins; D055358:Cone Opsins; D005136:Eye Proteins; D049452:Green Fluorescent Proteins; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase