title: Expression of the melatonin receptor Mel(1c) in neural tissues of the reef fish Siganus guttatus.
abstract: The golden rabbitfish, Siganus guttatus, is a reef fish exhibiting a restricted lunar-related rhythm in behavior and reproduction. Here, to understand the circadian rhythm of this lunar-synchronized spawner, a melatonin receptor subtype-Mel(1c)-was cloned. The full-length Mel(1c) melatonin receptor cDNA comprised 1747 bp with a single open reading frame (1062 bp) that encodes a 353-amino acid protein, which included 7 presumed transmembrane domains. Real-time PCR revealed high Mel(1c) mRNA expression in the retina and brain but not in the peripheral tissues. When the fish were reared under light/dark (LD 12:12) conditions, Mel(1c) mRNA in the retina and brain was expressed with daily variations and increased during nighttime. Similar variations were noted under constant conditions, suggesting that Mel(1c) mRNA expression is regulated by the circadian clock system. Daily variations of Mel(1c) mRNA expression with a peak at zeitgeber time (ZT) 12 were observed in the cultured pineal gland under LD 12:12. Exposure of the cultured pineal gland to light at ZT17 resulted in a decrease in Mel(1c) mRNA expression. When light was obstructed at ZT5, the opposite effect was obtained. These results suggest that light exerts certain effects on Mel(1c) mRNA expression directly or indirectly through melatonin actions.
authors.affiliation: Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, 3422 Sesoko, Motobu, Okinawa 905-0227, Japan.
authors.forename: Yong-Ju
authors.initials: YJ
authors.lastname: Park
authors.forename: Ji-Gweon
authors.initials: JG
authors.lastname: Park
authors.forename: Hyung-Bok
authors.initials: HB
authors.lastname: Jeong
authors.forename: Yuki
authors.initials: Y
authors.lastname: Takeuchi
authors.forename: Se-Jae
authors.initials: SJ
authors.lastname: Kim
authors.forename: Young-Don
authors.initials: YD
authors.lastname: Lee
authors.forename: Akihiro
authors.initials: A
authors.lastname: Takemura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002940:Circadian Rhythm / Q000528:radiation effects; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000528:radiation effects; D008027:Light; D008969:Molecular Sequence Data; D009417:Nerve Tissue / Q000378:metabolism* / Q000528:radiation effects; D010473:Perciformes / Q000378:metabolism*; D010802:Phylogeny; D010870:Pineal Gland / Q000378:metabolism / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044094:Receptors, Melatonin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D012160:Retina / Q000378:metabolism / Q000528:radiation effects; D017386:Sequence Homology, Amino Acid
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D044094:Receptors, Melatonin