title: Differential regulation of Period 2 and Period 3 expression during development of the zebrafish circadian clock.
abstract: Circadian ( approximately 24h) clocks are endogenous time-keeping systems that drive the daily biological rhythms observed in most living organisms. The oscillation is generated by a transcriptional/translational autoregulatory feedback loop that is reset by external time cues such as the light/dark cycle and which in turn controls rhythms in physiology and behavior through downstream clock-controlled genes (Nature 417 (2002) 329). Genetic and biochemical analysis of Drosophila and mammalian clock genes has provided a comprehensive model for the molecular oscillator that generates these rhythms, but the ontogeny of this oscillator remains poorly understood. A circadian oscillator involving the clock genes Per3 and Rev-erb alpha was identified during early development in zebrafish (Science 289 (2000) 297). Here, we report the isolation of zebrafish Per2 and show the presence of a Per2 maternal mRNA in early embryos as for Per3. However, Per2 rhythmic expression occurs late during embryogenesis as compared to that of Per3. Furthermore, our data indicate that Per2 is not required during embryogenesis for the rhythmicity of physiological outputs such as melatonin synthesis. In addition, Per2 but not Per3 is constitutively expressed in the developing olfactory bulb and pituitary. This differential spatio-temporal expression patterns suggest specific roles for Per2 and Per3 in the establishment of the embryonic circadian system.
authors.affiliation: Université de Nice-Sophia Antipolis, CNRS UMR 6078, 284 chemin du Lazaret, 06230 cedex, Villefranche/mer, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Delaunay
authors.forename: Christine
authors.initials: C
authors.lastname: Thisse
authors.forename: Bernard
authors.initials: B
authors.lastname: Thisse
authors.forename: Vincent
authors.initials: V
authors.lastname: Laudet
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics* / Q000502:physiology; D017124:Conserved Sequence; D005136:Eye Proteins / Q000096:biosynthesis / Q000235:genetics*; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics*; D056950:Period Circadian Proteins; D010802:Phylogeny; D014157:Transcription Factors; D015027:Zebrafish / Q000196:embryology / Q000235:genetics* / Q000502:physiology; D029961:Zebrafish Proteins
chemical_list: D005136:Eye Proteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; C498846:per2 protein, zebrafish; C512647:per3 protein, zebrafish