title: Entrainment of circadian rhythm to a photoperiod reversal shows retinal dystrophy in RPE65(-/-) mice.
abstract: Light entrainment of circadian rhythms is mediated by classical "visual" photoreceptors (rods and cones) as well as "nonvisual" photoreceptive elements (light-detecting cells that do not contribute to classical "vision"). This paper aimed to assess whether light entrainment of locomotor circadian rhythms in mice with impaired rods and cones differs from normal controls and whether this technique, alongside existing techniques, could be used to assess visual function. The study was primarily interested in differences between the entrainment of circadian rhythms of normal-sighted C57Bl/6J mouse and the C57Bl/RPE65 knockout mouse (RPE65(-/-)), although C3H/HeJ (rd/rd) mice were included as a preexisting model of retinal degeneration. Circadian rhythms of motor activity before and after a 12-h light reversal were assessed in custom-built cages that continuously monitored movement. The controls showed a significantly higher mesor and amplitude when compared to the RPE65(-/-) and rd/rd mice. Despite the loss of rods and cones, the RPE65(-/-) and rd/rd maintained a 24-h circadian rhythm entrained to light similar to controls and were capable of circadian reentrainment to a 12-h light reversal. Importantly, this light reentrainment of the circadian phase occurred at a significantly slower rate in the retinal degenerate models than in the controls. The RPE65(-/-) model demonstrates a retinal degenerate reentrainment phenotype when compared to the rd/rd model. It is suggested that these retinal degenerate mice retain the ability to detect light for the purposes of circadian rhythm entrainment. However, alterations of specific parameters of the circadian rhythm with loss of rods and cones may provide measures of loss of visual function (sight).
authors.affiliation: Centre for Ophthalmology and Vision Science, Lions Eye Institute, University of Western Australia, 2 Verdun Street, Nedlands, WA 6009, Australia. drudaniels@hotmail.com
authors.forename: D M
authors.initials: DM
authors.lastname: Daniels
authors.forename: C W
authors.initials: CW
authors.lastname: Stoddart
authors.forename: M T
authors.initials: MT
authors.lastname: Martin-Iverson
authors.forename: C-M
authors.initials: CM
authors.lastname: Lai
authors.forename: T M
authors.initials: TM
authors.lastname: Redmond
authors.forename: P E
authors.initials: PE
authors.lastname: Rakoczy
mesh_terms: D000204:Activity Cycles / Q000528:radiation effects*; D000818:Animals; D002352:Carrier Proteins; D002940:Circadian Rhythm / Q000528:radiation effects*; D005136:Eye Proteins / Q000502:physiology / Q000528:radiation effects*; D008027:Light; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017440:Photoperiod; D010786:Photoreceptor Cells / Q000503:physiopathology* / Q000528:radiation effects; D010857:Pigment Epithelium of Eye / Q000502:physiology / Q000528:radiation effects; D011506:Proteins / Q000502:physiology / Q000528:radiation effects*; D012162:Retinal Degeneration / Q000503:physiopathology*; D013045:Species Specificity; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase
chemical_list: D002352:Carrier Proteins; D005136:Eye Proteins; D011506:Proteins; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase