Using Per gene expression to search for photoperiodic oscillators in the hamster suprachiasmatic nucleus.
The circadian pacemaker in the suprachiasmatic nucleus (SCN) is also believed to underlie photoperiodic (seasonal) timekeeping in mammals. This clock has been modeled as a complex pacemaker composed of two coupled circadian oscillators; variability in their mutual phase relationship could account for the ability to measure daylength, with putative morning and evening oscillators synchronized to dawn and dusk, respectively. Recently, several genes have been identified that are believed to be part of the clock's core oscillatory mechanism. Here, we investigate how such molecular oscillations are altered as a function of photoperiod by analyzing Period (Per1, Per2, and Per3) gene expression at the mRNA level using SCN tissue sections and in situ hybridization. Golden hamsters were entrained to complete 24-h light-dark (LD) cycles with either a long (16 h) or a short (8 h) photophase, or they were entrained to the long complete photoperiod and then allowed to free-run in constant darkness. The results show large photoperiod-dependent changes in the duration of high daytime SCN Per1 and Per2 mRNA levels and small changes in the phase difference between their rhythms.
Department of Neurology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA.
Horacio O
HO
de la Iglesia
Jennifer
J
Meyer
William J
WJ
Schwartz
D000818:Animals; D001345:Autoradiography; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000502:physiology; D006224:Cricetinae; D015870:Gene Expression / Q000502:physiology* / Q000528:radiation effects; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D008647:Mesocricetus; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D056950:Period Circadian Proteins; D017440:Photoperiod; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*; D013997:Time Factors; D014157:Transcription Factors
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C513312:Per2 protein, mouse; C512645:Per3 protein, mouse; D056950:Period Circadian Proteins; D014157:Transcription Factors