PUBLICATION

Light signaling to the zebrafish circadian clock by Cryptochrome 1a

Authors
Tamai, T.K., Young, L.C., and Whitmore, D.
ID
ZDB-PUB-070907-32
Date
2007
Source
Proceedings of the National Academy of Sciences of the United States of America   104(37): 14712-14717 (Journal)
Registered Authors
Tamai, Takako Katherine, Whitmore, David, Young, Lucy
Keywords
entrainment, oscillator, phase shift, photoperiod
MeSH Terms
  • Animals
  • Biological Clocks/physiology*
  • Cell Line
  • Circadian Rhythm/physiology*
  • Cryptochromes
  • Flavoproteins/metabolism*
  • Immunohistochemistry
  • Light*
  • Luciferases/metabolism
  • Luminescent Measurements
  • Models, Biological
  • Oscillometry
  • Retroviridae/genetics
  • Signal Transduction*
  • Transfection
  • Two-Hybrid System Techniques
  • Zebrafish
PubMed
17785416 Full text @ Proc. Natl. Acad. Sci. USA
Abstract
Zebrafish tissues and cells have the unusual feature of not only containing a circadian clock, but also being directly light-responsive. Several zebrafish genes are induced by light, but little is known about their role in clock resetting or the mechanism by which this might occur. Here we show that Cryptochrome 1a (Cry1a) plays a key role in light entrainment of the zebrafish clock. Intensity and phase response curves reveal a strong correlation between light induction of Cry1a and clock resetting. Overexpression studies show that Cry1a acts as a potent repressor of clock function and mimics the effect of constant light to "stop" the circadian oscillator. Yeast two-hybrid analysis demonstrates that the Cry1a protein interacts directly with specific regions of core clock components, CLOCK and BMAL, blocking their ability to fully dimerize and transactivate downstream targets, providing a likely mechanism for clock resetting. A comparison of entrainment of zebrafish cells to complete versus skeleton photoperiods reveals that clock phase is identical under these two conditions. However, the amplitude of the core clock oscillation is much higher on a complete photoperiod, as are the levels of light-induced Cry1a. We believe that Cry1a acts on the core clock machinery in both a continuous and discrete fashion, leading not only to entrainment, but also to the establishment of a high-amplitude rhythm and even stopping of the clock under long photoperiods.
Genes / Markers
Figures
Expression
Phenotype
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Fish
Antibodies
Orthology
Engineered Foreign Genes
Mapping