title: In Vivo Visualization of Endoplasmic Reticulum Stress in the Retina Using the ERAI Reporter Mouse.
abstract: OBJECTIVE
  Endoplasmic reticulum (ER) stress activates inositol requiring enzyme 1 (IRE1), a key regulator of the unfolded protein response. The ER stress activated indicator (ERAI) transgenic mouse expresses a yellow fluorescent GFP variant (Venus) when IRE1 is activated by ER stress. We tested whether ERAI mice would allow for real-time longitudinal studies of ER stress in living mouse eyes.
  
  
  METHODS
  We chemically and genetically induced ER stress, and qualitatively and quantitatively studied the Venus signal by fluorescence ophthalmoscopy. We determined retinal cell types that contribute to the signal by immunohistology, and we performed molecular and biochemical assays using whole retinal lysates to assess activity of the IRE1 pathway.
  
  
  RESULTS
  We found qualitative increase in vivo in fluorescence signal at sites of intravitreal tunicamycin injection in ERAI eyes, and quantitative increase in ERAI mice mated to RhoP23H mice expressing ER stress-inducing misfolded rhodopsin protein. As expected, we found that increased Venus signal arose primarily from photoreceptors in RhoP23H/+;ERAI mice. We found increased Xbp1S and XBP1s transcriptional target mRNA levels in RhoP23H/+;ERAI retinas compared to Rho+/+;ERAI retinas, and that Venus signal increased in ERAI retinas as a function of age.
  
  
  CONCLUSIONS
  Fluorescence ophthalmoscopy of ERAI mice enables in vivo visualization of retinas undergoing ER stress. ER stress activated indicator mice enable identification of individual retinal cells undergoing ER stress by immunohistochemistry. ER stress activated indicator mice show higher Venus signal at older ages, likely arising from amplification of basal retinal ER stress levels by GFP's inherent stability.
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States.
authors.forename: Marcel V
authors.initials: MV
authors.lastname: Alavi
authors.affiliation: Department of Pathology, University of California, San Diego, La Jolla, California, United States.
authors.forename: Wei-Chieh
authors.initials: WC
authors.lastname: Chiang
authors.affiliation: Department of Pathology, University of California, San Diego, La Jolla, California, United States.
authors.forename: Heike
authors.initials: H
authors.lastname: Kroeger
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States.
authors.forename: Douglas
authors.initials: D
authors.lastname: Yasumura
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Matthes
authors.affiliation: Advanced Scientific Research Leaders Development Unit, Gunma University, Gunma, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Iwawaki
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States.
authors.forename: Matthew M
authors.initials: MM
authors.lastname: LaVail
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States 4Department of Anatomy and Institute for Human Genetics, University of California, San Francisco, San Francisco, California, United States.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Gould
authors.affiliation: Department of Pathology, University of California, San Diego, La Jolla, California, United States 5VA San Diego Healthcare System, San Diego, California, United States.
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Lin
mesh_terms: D000818:Animals; D004721:Endoplasmic Reticulum / Q000000981:diagnostic imaging / Q000473:pathology / Q000502:physiology; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000502:physiology*; D008137:Longitudinal Studies; D008565:Membrane Proteins / Q000032:analysis / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D009887:Ophthalmoscopy; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000502:physiology; D012160:Retina / Q000737:chemistry / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D041623:Tomography, Optical Coherence; D014415:Tunicamycin / Q000494:pharmacology; D014463:Ultrasonography
chemical_list: D008565:Membrane Proteins; D014415:Tunicamycin; C486556:Ern2 protein, mouse; D017346:Protein Serine-Threonine Kinases