title: Early development of circadian rhythmicity in the suprachiamatic nuclei and pineal gland of teleost, flounder (Paralichthys olivaeus), embryos.
abstract: Circadian rhythms enable organisms to coordinate multiple physiological processes and behaviors with the earth's rotation. In mammals, the suprachiasmatic nuclei (SCN), the sole master circadian pacemaker, has entrainment mechanisms that set the circadian rhythm to a 24-h cycle with photic signals from retina. In contrast, the zebrafish SCN is not a circadian pacemaker, instead the pineal gland (PG) houses the major circadian oscillator. The SCN of flounder larvae, unlike that of zebrafish, however, expresses per2 with a rhythmicity of daytime/ON and nighttime/OFF. Here, we examined whether the rhythm of per2 expression in the flounder SCN represents the molecular clock. We also examined early development of the circadian rhythmicity in the SCN and PG. Our three major findings were as follows. First, rhythmic per2 expression in the SCN was maintained under 24 h dark (DD) conditions, indicating that a molecular clock exists in the flounder SCN. Second, onset of circadian rhythmicity in the SCN preceded that in the PG. Third, both 24 h light (LL) and DD conditions deeply affected the development of circadian rhythmicity in the SCN and PG. This is the first report dealing with the early development of circadian rhythmicity in the SCN in fish.
authors.affiliation: Laboratory of Marine Life Science and Genetics, Graduate School of Agricultural Science, Tohoku University, Sendai, 981-8555, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Mogi
authors.affiliation: National Research Institute of Aquaculture, Farming Biology Division, Fisheries Research Agency, 422-1 Minamiise, Watarai, Mie, 516-0193, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Uji
authors.affiliation: Laboratory of Marine Life Science and Genetics, Graduate School of Agricultural Science, Tohoku University, Sendai, 981-8555, Japan.
authors.forename: Hayato
authors.initials: H
authors.lastname: Yokoi
authors.affiliation: Laboratory of Marine Life Science and Genetics, Graduate School of Agricultural Science, Tohoku University, Sendai, 981-8555, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D047068:Arylalkylamine N-Acetyltransferase / Q000235:genetics; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D004625:Embryo, Nonmammalian; D005432:Flounder / Q000196:embryology* / Q000235:genetics / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D056950:Period Circadian Proteins / Q000235:genetics; D010870:Pineal Gland / Q000196:embryology* / Q000502:physiology; D013493:Suprachiasmatic Nucleus / Q000196:embryology* / Q000502:physiology; D014365:Tryptophan Hydroxylase / Q000235:genetics; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics
chemical_list: D056950:Period Circadian Proteins; D014446:Tyrosine 3-Monooxygenase; D014365:Tryptophan Hydroxylase; D047068:Arylalkylamine N-Acetyltransferase
keywords: circadian rhythm; early development; flounder; pineal gland; suprachiasmatic nucleus