title: Photoperiod differentially regulates clock genes' expression in the suprachiasmatic nucleus of Syrian hamster.
abstract: The suprachiasmatic nuclei (SCN) contain the master circadian pacemaker in mammals. Generation and maintenance of circadian oscillations involve clock genes which interact to form transcriptional/translational loops and constitute the molecular basis of the clock. There is some evidence that the SCN clock can integrate variations in day length, i.e. photoperiod. However, the effects of photoperiod on clock-gene expression remain largely unknown. We here report the expression pattern of Period (Per) 1, Per2, Per3, Cryptochrome (Cry) 1, Cry2, Bmal1 and Clock genes in the SCN of Syrian hamsters when kept under long (LP) and short (SP) photoperiods. Our data show that photoperiod differentially affects the expression of all clock genes studied. Among the components of the negative limb of the feedback loop, Per1, Per2, Per3, Cry2 but not Cry1 genes show a shortened duration of their peak expression under SP compared with LP. Moreover, mRNA expression of Per1, Per3 and Cry1 are phase advanced in SP compared with LP. Per3 shows an mRNA peak of higher amplitude under SP conditions whereas Per1 and Per2 peak amplitudes are unaffected by photoperiod changes. Bmal1 expression is phase advanced without a change of duration in SP compared with LP. Furthermore, the expression of Clock is rhythmic under SP whereas no rhythm is observed under LP. These results, which provide further evidence that the core clock mechanisms of the SCN integrate photoperiod, are discussed in the context of the existing molecular model.
authors.affiliation: Neurobiologie des Rythmes, UMR 7518 CNRS/ULP, IFR Neurosciences 37, 12 rue de l'Université, 67000 Strasbourg, France.
authors.forename: B B
authors.initials: BB
authors.lastname: Tournier
authors.forename: J S
authors.initials: JS
authors.lastname: Menet
authors.forename: H
authors.initials: H
authors.lastname: Dardente
authors.forename: V J
authors.initials: VJ
authors.lastname: Poirel
authors.forename: A
authors.initials: A
authors.lastname: Malan
authors.forename: M
authors.initials: M
authors.lastname: Masson-Pévet
authors.forename: P
authors.initials: P
authors.lastname: Pévet
authors.forename: P
authors.initials: P
authors.lastname: Vuillez
mesh_terms: D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000235:genetics*; D006224:Cricetinae; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D056950:Period Circadian Proteins; D017440:Photoperiod; D017956:Photoreceptor Cells, Invertebrate; D012333:RNA, Messenger / Q000096:biosynthesis; D043562:Receptors, G-Protein-Coupled; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*; D013997:Time Factors; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D015534:Trans-Activators; D014157:Transcription Factors; C538961:Bmal1 protein, mouse; C538964:Cry1 protein, mouse; C538967:Cry2 protein, mouse; C513312:Per2 protein, mouse; C512645:Per3 protein, mouse; C119828:cry protein, Drosophila; C538944:Clock protein, mouse