title: Per and neuropeptide expression in the rat suprachiasmatic nuclei: compartmentalization and differential cellular induction by light.
abstract: Per1 and Per2, two clock genes rhythmically expressed in the suprachiasmatic nucleus (SCN), are implicated in the molecular mechanism of the circadian pacemaker and play a major role in its entrainment by light. To date, it is not known if every cell of the SCN, a heterogeneous structure in respect of neuropeptide content, expresses clock genes equally. The aim of this study was to identify, by single and double non-radioactive and/or radioactive hybridizations, the cell types (AVP, VIP and GRP) expressing Per1 or Per2 in the SCN of rats, (1) when Per are highly expressed during the daytime, and (2) after induction of Per expression by a light pulse at night. Our results indicate that, during the daytime, Per1 and Per2 genes are both mainly expressed in the AVP cells of the dorso-median part of the SCN, whereas only a few VIP cells in the ventral part of the SCN exhibit Per gene expression. In contrast, following a light pulse at night, there is differential induction of the two Per genes. Per1 expression essentially occurs in the ventro-lateral GRP cells, while Per2 expression is not restricted to the retinorecipient part of the SCN as it also occurs in AVP cells. Altogether, our results suggest that Per1 and Per2 are mainly expressed in AVP cells during the daytime and suggest that GRP cells play an important role in resetting of the clock by light.
authors.affiliation: Neurobiologie des Rythmes, UMR 7518 CNRS/ULP, IFR 37, 12 Rue de l'Université, 67000 Strasbourg, France.
authors.forename: Hugues
authors.initials: H
authors.lastname: Dardente
authors.forename: Vincent-Joseph
authors.initials: VJ
authors.lastname: Poirel
authors.forename: Paul
authors.initials: P
authors.lastname: Klosen
authors.forename: Paul
authors.initials: P
authors.lastname: Pévet
authors.forename: Mireille
authors.initials: M
authors.lastname: Masson-Pévet
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology*; D008027:Light; D008297:Male; D009479:Neuropeptides / Q000096:biosynthesis*; D009687:Nuclear Proteins / Q000096:biosynthesis*; D056950:Period Circadian Proteins; D017440:Photoperiod; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000378:metabolism*; D014157:Transcription Factors
chemical_list: D018797:Cell Cycle Proteins; D009479:Neuropeptides; D009687:Nuclear Proteins; C539023:Per1 protein, mouse; C539024:Per1 protein, rat; C513312:Per2 protein, mouse; C513311:Per2 protein, rat; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D014157:Transcription Factors