title: Expression and regulation of Icer mRNA in the Syrian hamster pineal gland.
abstract: Inducible-cAMP early repressor (ICER) is a potent inhibitor of CRE (cAMP-related element)-driven gene transcription. In the rat pineal gland, it has been proposed to be part of the mechanisms involved in the shutting down of the transcription of the gene coding for arylalkylamine N-acetyltransferase (AA-NAT, the melatonin rhythm-generating enzyme). In this study, we report that ICER is expressed in the pineal gland of the photoperiodic rodent Syrian hamster although with some difference compared to the rat. In the Syrian hamster pineal, Icer mRNA levels, low at daytime, displayed a 20-fold increase during the night. Nighttime administration of a beta-adrenergic antagonist, propranolol, significantly reduced Icer mRNA levels although daytime administration of a beta-adrenergic agonist, isoproterenol, was unable to raise the low amount of Icer mRNA. These observations indicate that Icer mRNA expression is induced by the clock-driven norepinephrine release and further suggest that this stimulation is restricted to nighttime, as already observed for Aa-nat gene transcription. Furthermore, we found that the daily profile of Icer mRNA displayed photoperiodic variation with a lengthening of the nocturnal peak in short versus long photoperiod. These data indicate that ICER may be involved in both daily and seasonal regulation of melatonin synthesis in the Syrian hamster.
authors.affiliation: Departamento de Biologi;a Funcional, Area Fisiologi;a, Facultad de Medicina, Universidad de Oviedo, 33006, Oviedo, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Diaz
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Garidou
authors.forename: Hugues
authors.initials: H
authors.lastname: Dardente
authors.forename: Anthony
authors.initials: A
authors.lastname: Salingre
authors.forename: Paul
authors.initials: P
authors.lastname: Pévet
authors.forename: Valérie
authors.initials: V
authors.lastname: Simonneaux
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics*; D006224:Cricetinae; D051786:Cyclic AMP Response Element Modulator; D004268:DNA-Binding Proteins / Q000235:genetics*; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics*; D008550:Melatonin / Q000096:biosynthesis*; D008647:Mesocricetus / Q000235:genetics / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D010775:Photic Stimulation; D017440:Photoperiod; D010870:Pineal Gland / Q000378:metabolism*; D012097:Repressor Proteins; D012621:Seasons
chemical_list: D000319:Adrenergic beta-Antagonists; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D051786:Cyclic AMP Response Element Modulator; D008550:Melatonin; D009638:Norepinephrine