title: Circadian regulation of the PERIOD 2::LUCIFERASE bioluminescence rhythm in the mouse retinal pigment epithelium-choroid.
abstract: OBJECTIVE
  The retinal pigment epithelium (RPE) plays an important role in the maintenance of the health and function of photoreceptors. Previous studies have shown that the RPE is also involved in the regulation of disc shedding, a process that is vital for photoreceptor health. This process has been shown to be under circadian control, although the mechanisms that control it are poorly understood. The aim of the present study was to investigate Period 2 (Per2) mRNA levels in the mouse RPE in vivo, and to determine whether the cultured RPE-choroid from PERIOD 2::LUCIFERASE (PER2::LUC) knockin mice expresses a circadian rhythm in bioluminescence.
  
  
  METHODS
  Per2 mRNA levels were measured using real-time quantitative RT-PCR, and bioluminescence was measured in PER2::LUC knockin mice using a Lumicycle®.
  
  
  RESULTS
  Per2 mRNA levels in the RPE-choroid show a clear circadian rhythm in vivo. A circadian rhythm in PER2::LUC bioluminescence was recorded from cultured RPE-choroid explants. Light exposure during the subjective night did not cause a circadian rhythm phase-shift of PER2::LUC bioluminescence. Finally, removal of the suprachiasmatic nuclei of the hypothalamus did not affect the bioluminescence circadian rhythm in the RPE-choroid.
  
  
  CONCLUSIONS
  Our results demonstrate that the RPE-choroid contains a circadian clock, and the regulation of this circadian rhythm resides within the eye. These new data indicate that it may be useful to design studies with the aim of elucidating the molecular mechanisms responsible for the regulation of the rhythmic event in the RPE.
authors.affiliation: Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30130, USA.
authors.forename: Kenkichi
authors.initials: K
authors.lastname: Baba
authors.forename: Anamika
authors.initials: A
authors.lastname: Sengupta
authors.forename: Manfredi
authors.initials: M
authors.lastname: Tosini
authors.forename: Susana
authors.initials: S
authors.lastname: Contreras-Alcantara
authors.forename: Gianluca
authors.initials: G
authors.lastname: Tosini
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002829:Choroid / Q000378:metabolism* / Q000528:radiation effects; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D005786:Gene Expression Regulation / Q000528:radiation effects; D008027:Light; D008156:Luciferases / Q000378:metabolism*; D008164:Luminescent Proteins / Q000378:metabolism*; D051379:Mice; D009043:Motor Activity / Q000502:physiology / Q000528:radiation effects; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000378:metabolism* / Q000528:radiation effects; D013493:Suprachiasmatic Nucleus / Q000473:pathology / Q000503:physiopathology / Q000528:radiation effects
chemical_list: D008164:Luminescent Proteins; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D008156:Luciferases