title: Comparison of ocular pathologies in vitamin A-deficient mice and RPE65 gene knockout mice.
abstract: OBJECTIVE
  RPE65 gene knockout (Rpe65⁻/⁻) mice showed abolished isomerohydrolase activity in the visual cycle and were considered a model for vitamin A deficiency in the retina. The purpose of this study was to compare the retinal phenotypes between vitamin A-deficient (VAD) mice and Rpe65⁻/⁻ mice under normal diet.
  
  
  METHODS
  The VAD mice were fed with a vitamin A-deprived diet after birth. The age-matched control mice and Rpe65⁻/⁻ mice were maintained under normal diet. The structure of photoreceptor outer segment was compared using electron microscopy. Photoreceptor-specific gene expression was determined using real-time RT-PCR. The isomerohydrolase and lecithin-retinol acyltransferase (LRAT) activities were measured using an in vitro enzymatic activity assay. Endogenous retinoid profiles were analyzed by HPLC in mouse eyecup homogenates.
  
  
  RESULTS
  Compared to wild-type mice under normal diet, scanning and transmission electron microscopy showed that the outer segments of photoreceptors were disorganized in VAD mice and were not disorganized in Rpe65⁻/⁻ mice, although they were shortened in the latter. VAD mice showed more prominent downregulation of middle wavelength cone opsin, whereas Rpe65⁻/⁻ mice displayed more suppressed expression of short wavelength cone opsin. In vitro enzymatic activity assay and Western blot analysis showed that vitamin A deprivation downregulated LRAT expression and activity in the eyecup, but Rpe65⁻/⁻ mice showed unchanged LRAT expression and activity. The depressed LRAT activity in VAD mice was partially rescued by the intraperitoneal injection of retinoic acid.
  
  
  CONCLUSIONS
  VAD and Rpe65⁻/⁻ mice are different in cone photoreceptor degeneration, photoreceptor-specific gene regulation, isomerohydrolase activity, endogenous retinoid profile, and LRAT activity.
authors.affiliation: Department of Physiology, Department of Medicine and Harold Hamm Oklahoma Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Hu
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.forename: Gennadiy
authors.initials: G
authors.lastname: Moiseyev
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Robert
authors.initials: R
authors.lastname: Mott
authors.forename: Jian-Xing
authors.initials: JX
authors.lastname: Ma
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics*; D002452:Cell Count; D002851:Chromatography, High Pressure Liquid; D005136:Eye Proteins / Q000235:genetics*; D015870:Gene Expression / Q000502:physiology; D007274:Injections, Intraperitoneal; D051379:Mice; D018345:Mice, Knockout; D008855:Microscopy, Electron, Scanning; D055355:Opsins / Q000378:metabolism; D010641:Phenotype; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism / Q000648:ultrastructure; D012162:Retinal Degeneration / Q000378:metabolism / Q000473:pathology*; D055214:Retinal Photoreceptor Cell Outer Segment / Q000648:ultrastructure; D055213:Retinal Pigment Epithelium / Q000378:metabolism / Q000473:pathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014212:Tretinoin / Q000008:administration & dosage; D014801:Vitamin A / Q000502:physiology*; D014802:Vitamin A Deficiency / Q000378:metabolism / Q000473:pathology*; D019745:cis-trans-Isomerases / Q000378:metabolism; D000099178:Retinoid Isomerohydrolase
chemical_list: D000217:Acyltransferases; D002352:Carrier Proteins; D005136:Eye Proteins; D055355:Opsins; D014212:Tretinoin; D014801:Vitamin A; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase; C056942:lecithin-retinol acyltransferase