title: Monitoring circadian time in rat plasma using a secreted Cypridina luciferase reporter.
abstract: A firefly luciferase reporter enabled us to monitor promoter activity in vivo as well as ex vivo; however, this requires a sufficient supply of the substrate luciferin and specific monitoring devices. To overcome these disadvantages, we developed transgenic rats carrying a secreted enzyme Cypridina luciferase (CLuc) reporter under the promoter of clock gene Per2 (Per2-CLuc). Per2-CLuc activity in serially sampled blood from freely moving rats exhibited robust circadian rhythms with a peak at early morning. The Per2-CLuc bioluminescence could be quantified even with approximately 100pl of plasma. Plasma Per2-CLuc rhythms were phase reversed, and the level was reduced by restricting food access for 2h during the light phase, suggesting that the plasma Per2-CLuc rhythms reflect the phase of peripheral clocks entrained to feeding cues as well as fuel metabolism. Fasting for 2days did not alter the circadian Per2-CLuc rhythms in rats, suggesting that feeding per se did not affect the circadian Per2-CLuc rhythms. Tissue-specific Per2-CLuc rhythms were observed in culture medium of peripheral tissues. The Per2-CLuc reporter is a powerful tool to access gene expression in vivo as well as ex vivo with ordinary laboratory equipment.
authors.affiliation: Photonic Bioimaging Section, Research Center for Cooperative Projects, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan.
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Yamada
authors.forename: Shin-Ya
authors.initials: SY
authors.lastname: Nishide
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Watanabe
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Ohmiya
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Honma
authors.forename: Sato
authors.initials: S
authors.lastname: Honma
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D003445:Crustacea / Q000201:enzymology*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D008156:Luciferases / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D041681:NIH 3T3 Cells; D030781:Organisms, Genetically Modified; D051381:Rats
chemical_list: D008156:Luciferases
keywords: Circadian rhythm; Clock gene; In vivo recording; Secreted luciferase reporter; Transgenic rats