Temporal-spatial characterization of chicken clock genes: circadian expression in retina, pineal gland, and peripheral tissues

J Neurochem. 2003 May;85(4):851-60. doi: 10.1046/j.1471-4159.2003.01723.x.


The molecular core of the vertebrate circadian clock is a set of clock genes, whose products interact to control circadian changes in physiology. These clock genes are expressed in all tissues known to possess an endogenous self-sustaining clock, and many are also found in peripheral tissues. In the present study, the expression patterns of two clock genes, cBmal1 and cMOP4, were examined in the chicken, a useful model for analysis of the avian circadian system. In two tissues which contain endogenous clocks--the pineal gland and retina--circadian fluctuations of both cBmal1 and cMOP4 mRNAs were observed to be synchronous; highest levels occurred at Zeitgeber time 12. Expression of these genes is also rhythmic in several peripheral tissues; however, the phases of these rhythms differ from those in the pineal gland and retina: in the liver the peaks of cMOP4 and cBmal1 mRNAs are delayed 4-8 h and in the heart they are advanced by 4 h, relative to those in the pineal gland and retina. These results provide the first temporal characterization of cBmal1 and cMOP4 mRNAs in avian tissues: their presence in avian peripheral tissues indicates they may influence temporal features of daily rhythms in biochemical, physiological, and behavioral functions at these sites.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ARNTL Transcription Factors
  • Alternative Splicing
  • Animals
  • Base Sequence
  • Basic Helix-Loop-Helix Transcription Factors
  • Biological Clocks / physiology
  • Blotting, Northern
  • Chickens
  • Circadian Rhythm / physiology*
  • Gene Expression Regulation / physiology*
  • Male
  • Molecular Sequence Data
  • Organ Specificity
  • Photoperiod
  • Pineal Gland / metabolism*
  • RNA, Messenger / metabolism
  • Retina / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Homology, Nucleic Acid
  • Transcription Factors / genetics*


  • ARNTL Transcription Factors
  • Basic Helix-Loop-Helix Transcription Factors
  • RNA, Messenger
  • Transcription Factors