title: Effects of Photoperiod Extension on Clock Gene and Neuropeptide RNA Expression in the SCN of the Soay Sheep.
abstract: In mammals, changing daylength (photoperiod) is the main synchronizer of seasonal functions. The photoperiodic information is transmitted through the retino-hypothalamic tract to the suprachiasmatic nuclei (SCN), site of the master circadian clock. To investigate effects of day length change on the sheep SCN, we used in-situ hybridization to assess the daily temporal organization of expression of circadian clock genes (Per1, Per2, Bmal1 and Fbxl21) and neuropeptides (Vip, Grp and Avp) in animals acclimated to a short photoperiod (SP; 8h of light) and at 3 or 15 days following transfer to a long photoperiod (LP3, LP15, respectively; 16h of light), achieved by an acute 8-h delay of lights off. We found that waveforms of SCN gene expression conformed to those previously seen in LP acclimated animals within 3 days of transfer to LP. Mean levels of expression for Per1-2 and Fbxl21 were nearly 2-fold higher in the LP15 than in the SP group. The expression of Vip was arrhythmic and unaffected by photoperiod, while, in contrast to rodents, Grp expression was not detectable within the sheep SCN. Expression of the circadian output gene Avp cycled robustly in all photoperiod groups with no detectable change in phasing. Overall these data suggest that synchronizing effects of light on SCN circadian organisation proceed similarly in ungulates and in rodents, despite differences in neuropeptide gene expression.
authors.affiliation: PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France.|Institute of Biological and Environmental Sciences, Zoology Building, Tillydrone Avenue, University of Aberdeen, Aberdeen, AB24 2TZ, United Kingdom.
authors.forename: Hugues
authors.initials: H
authors.lastname: Dardente
authors.affiliation: Institute of Biological and Environmental Sciences, Zoology Building, Tillydrone Avenue, University of Aberdeen, Aberdeen, AB24 2TZ, United Kingdom.|Veterinary school, Bearsden Road, Glasgow, G61 1QH, United Kingdom.
authors.forename: Cathy A
authors.initials: CA
authors.lastname: Wyse
authors.affiliation: Queen's Medical Research Institute, University of Edinburgh, Edinburgh, EH16 4SB, United Kingdom.
authors.forename: Gerald A
authors.initials: GA
authors.lastname: Lincoln
authors.affiliation: Institute of Biological and Environmental Sciences, Zoology Building, Tillydrone Avenue, University of Aberdeen, Aberdeen, AB24 2TZ, United Kingdom.|Department of Arctic and Marine Biology, Faculty of BioSciences, Fisheries and Economy, University of Tromsø, 9037, Tromsø, Norway.
authors.forename: Gabriela C
authors.initials: GC
authors.lastname: Wagner
authors.affiliation: Institute of Biological and Environmental Sciences, Zoology Building, Tillydrone Avenue, University of Aberdeen, Aberdeen, AB24 2TZ, United Kingdom.|Department of Arctic and Marine Biology, Faculty of BioSciences, Fisheries and Economy, University of Tromsø, 9037, Tromsø, Norway.
authors.forename: David G
authors.initials: DG
authors.lastname: Hazlerigg
mesh_terms: D000818:Animals; D057906:Circadian Clocks / Q000235:genetics*; D015870:Gene Expression; D009479:Neuropeptides / Q000235:genetics*; D017440:Photoperiod; D012333:RNA, Messenger / Q000235:genetics; D012756:Sheep; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*; D013997:Time Factors
chemical_list: D009479:Neuropeptides; D012333:RNA, Messenger