title: Daily and seasonal expression of clock genes in the pituitary of the European sea bass (Dicentrarchus labrax).
abstract: The expression of select clock genes (clock, bmal, per1, per2, cry1, cry2) was investigated throughout the day and across the four seasons for two consecutive years in the pituitary of adult sea bass (Dicentrarchus labrax). A rhythmic pattern of daily expression was consistently observed in summer and autumn, while arrhythmicity was observed for some clock genes during spring and winter, concomitant with low water temperatures. The expression of clock and bmal showed highest values at the end of the day and during the night, while that of per and cry was mostly antiphasic, with high values during the day. Melatonin affects clock-gene expression in the pituitary of mammals. We therefore sought to test the effect of melatonin on clock-gene expression in the pituitary of sea bass both in vivo and in vitro. Melatonin modestly affected the expression of some clock genes (in particular cry genes) when added to the fish diet or the culture medium of pituitary glands. Our data show that clock genes display rhythmic daily expression in the pituitary of adult sea bass, which are profoundly modified according to the season. We suggest that the effect of photoperiod on clock gene expression may be mediated, at least in part, by melatonin, and that temperature may have a key role adjusting seasonal variations.
authors.affiliation: CNRS, UMR7232 BIOM, Laboratoire Arago, Banyuls-sur-Mer, France; Université Pierre et Marie Curie-Paris6, UMR7232, Laboratoire Arago, Banyuls-sur-Mer, France. Electronic address: mjhr@um.es.
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: Herrero
authors.affiliation: Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération, Université Paul Sabatier Toulouse III, Toulouse, France.
authors.forename: Julie M J
authors.initials: JM
authors.lastname: Lepesant
mesh_terms: D000818:Animals; D001492:Bass / Q000097:blood / Q000235:genetics*; D056926:CLOCK Proteins / Q000235:genetics* / Q000378:metabolism; D002940:Circadian Rhythm / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D003470:Culture Media; D019587:Dietary Supplements; D005060:Europe; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects; D008027:Light; D008550:Melatonin / Q000097:blood / Q000494:pharmacology; D017440:Photoperiod; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D012621:Seasons; D013696:Temperature
chemical_list: D003470:Culture Media; D056926:CLOCK Proteins; D008550:Melatonin
keywords: Clock genes; Daily rhythms; European sea bass; Melatonin; Pituitary; Seasonal rhythms