title: Embryonic and post-embryonic expression of arylalkylamine N-acetyltransferase and melatonin receptor genes in the eye and brain of chum salmon (Oncorhynchus keta).
abstract: Melatonin and arylalkylamine N-acetyltransferase (AANAT), the rate-limiting enzyme in melatonin synthesis, have taken on special importance in vertebrate circadian biology. Recent identification of genes encoding two AANAT (AANAT(1) and AANAT(2)) and two subtypes of melatonin receptor (Mel-R; Mel(1a) and Mel(1b)) in several fish species has led to rapid advances in characterizing the physiological roles of melatonin. In the present study, partial cDNAs encoding these four genes were cloned from the eye and brain of chum salmon (Oncorhynchus keta). Based on the nucleotide sequences, we developed highly sensitive real-time PCR systems for these four mRNAs. The development of daily rhythmicity in AANAT(1), AANAT(2), Mel(1a), and Mel(1b) transcript levels was examined in the eye and brain of chum salmon during embryonic and post-embryonic stages (from day -9 to day +180). In a parallel experiment, ocular and brain melatonin levels were measured by radioimmunoassay. Parallelism in developmental changes and in circadian rhythms of AANAT mRNAs and melatonin levels in the eye and the brain supports a hypothesis that the developmental increases of nocturnal melatonin levels results partly from the elevated transcription of AANAT genes. Moreover, abundant expression of AANAT and Mel-R mRNAs in the optic tectum, thalamus, hypothalamus, cerebellum, and eye indicates possible roles of melatonin in visual processing and neuroendocrine regulation, through which melatonin might be involved in migratory behavior of chum salmon.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Shi
authors.forename: Hironori
authors.initials: H
authors.lastname: Ando
authors.forename: Steven L
authors.initials: SL
authors.lastname: Coon
authors.forename: Shunpei
authors.initials: S
authors.lastname: Sato
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Ban
authors.forename: Akihisa
authors.initials: A
authors.lastname: Urano
mesh_terms: D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000096:biosynthesis* / Q000235:genetics; D001483:Base Sequence; D001921:Brain / Q000201:enzymology / Q000378:metabolism; D002940:Circadian Rhythm / Q000235:genetics; D003001:Cloning, Molecular; D005123:Eye / Q000201:enzymology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D008550:Melatonin / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D017685:Oncorhynchus keta / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D044094:Receptors, Melatonin / Q000096:biosynthesis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary
chemical_list: D012333:RNA, Messenger; D044094:Receptors, Melatonin; D001191:Arylamine N-Acetyltransferase; D008550:Melatonin