title: Circadian and ultradian rhythms of clock gene expression in the suprachiasmatic nucleus of freely moving mice.
abstract: In mammals, the temporal order of physiology and behavior is primarily regulated by the circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). Rhythms are generated in cells by an auto-regulatory transcription/translation feedback loop, composed of several clock genes and their protein products. Taking advantage of bioluminescence reporters, we have succeeded in continuously monitoring the expression of clock gene reporters Per1-luc, PER2::LUC and Bmal1-ELuc in the SCN of freely moving mice for up to 3 weeks in constant darkness. Bioluminescence emitted from the SCN was collected with an implanted plastic optical fiber which was connected to a cooled photomultiplier tube. We found robust circadian rhythms in the clock gene expression, the phase-relation of which were the same as those observed ex vivo. The circadian rhythms were superimposed by episodic bursts which had ultradian periods of approximately 3.0 h. Episodic bursts often accompanied activity bouts, but stoichiometric as well as temporal analyses revealed no causality between them. Clock gene expression in the SCN in vivo is regulated by the circadian pacemaker and ultradian rhythms of unknown origin.
authors.affiliation: Photonic Bioimaging Section, Research Center for Cooperative Projects, Hokkaido University Graduate School of Medicine, Sapporo, 060-8638, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ono
authors.affiliation: Department of Chronomedicine, Hokkaido University Graduate School of Medicine, Sapporo, 060-8638, Japan.
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Honma
authors.affiliation: Department of Chronomedicine, Hokkaido University Graduate School of Medicine, Sapporo, 060-8638, Japan.
authors.forename: Sato
authors.initials: S
authors.lastname: Honma
mesh_terms: D056930:ARNTL Transcription Factors / Q000235:genetics / Q000378:metabolism; D000818:Animals; D056926:CLOCK Proteins / Q000235:genetics* / Q000378:metabolism; D002940:Circadian Rhythm / Q000235:genetics*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D049449:Luminescence; D051379:Mice; D009068:Movement; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*
chemical_list: D056930:ARNTL Transcription Factors; C538961:Bmal1 protein, mouse; D056950:Period Circadian Proteins; D056926:CLOCK Proteins; C538944:Clock protein, mouse