title: Phenotype of Per1- and Per2-expressing neurons in the suprachiasmatic nucleus of a diurnal rodent (Arvicanthis ansorgei): comparison with a nocturnal species, the rat.
abstract: In mammals, the suprachiasmatic nuclei (SCN) are the site of the master circadian pacemaker whose molecular core mechanism is based on interlocking transcriptional/translational feedback loops involving clock genes. Among clock genes, Per1 and Per2 are important for both the maintenance of circadian rhythmicity and entrainment to light cues. Several circadian rhythms (e.g., locomotor activity) present opposite patterns in diurnal and nocturnal species. To test whether a differential cellular expression of clock genes in the SCN could constitute the neural substrate leading to diurnal or nocturnal behavior, we identified, by single or double non-radioactive hybridizations, the phenotype of neurons expressing Per1 and Per2 during the day in a diurnal species, Arvicanthis ansorgei, and in a nocturnal species, the rat (Rattus norvegicus). We show that in both species, expression of Per1 and Per2 is mostly restricted to the dorsomedial part of the SCN, often coexpressed with arginine vasopressin (AVP). A few vasoactive intestinal polypeptide (VIP) neurons were also shown to express Per1 and Per2. This differential expression of Per1 and Per2 in AVP and VIP neurons is more distinct in A. ansorgei than in the rat. Thus, our data suggest a major role for the dorsomedial part of the SCN in the maintenance of circadian rhythmicity. Furthermore, the similar diurnal pattern of Per1 and Per2 expression in diurnal and nocturnal rodents suggests that the circadian organization of locomotor activity rhythms probably relies on differential cellular integration mechanisms downstream of the clock.
authors.affiliation: Laboratory of Neurobiology of Rhythms, UMR 7518 CNRS/ULP, University of Strasbourg, 12, rue de l'université, 67000 Strasbourg, France.
authors.forename: Hugues
authors.initials: H
authors.lastname: Dardente
authors.forename: Paul
authors.initials: P
authors.lastname: Klosen
authors.forename: Ivette
authors.initials: I
authors.lastname: Caldelas
authors.forename: Paul
authors.initials: P
authors.lastname: Pévet
authors.forename: Mireille
authors.initials: M
authors.lastname: Masson-Pévet
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000235:genetics; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D005786:Gene Expression Regulation / Q000235:genetics; D008027:Light; D008297:Male; D009474:Neurons / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics*; D056950:Period Circadian Proteins; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar / Q000033:anatomy & histology / Q000378:metabolism*; D013045:Species Specificity; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000378:metabolism*; D014157:Transcription Factors
chemical_list: D018797:Cell Cycle Proteins; 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