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Photic induction of mPer1 and mPer2 in cry-deficient mice lacking a biological clock

H Okamura1, S Miyake, Y Sumi

  • 1Department of Anatomy and Brain Science, Kobe University School of Medicine, Kobe 650-0017, Japan. okamurah@kobe-u.ac.jp

Science (New York, N.Y.)
|January 5, 2000
PubMed

Insights

Mice lacking both mammalian cryptochromes (mCRY1 and mCRY2) lose their biological clock, leading to arrhythmic behavior. However, these cryptochromes are not essential for light-induced clock resetting.

Area of Science:

  • Chronobiology
  • Molecular Biology
  • Genetics

Background:

  • Circadian rhythms are regulated by molecular feedback loops involving clock genes.
  • Mammalian cryptochromes (mCRY1 and mCRY2) are key components of the circadian clock.
  • The precise role of mCRY1 and mCRY2 in the negative limb of the feedback loop requires further elucidation.

Purpose of the Study:

  • To investigate the function of mCRY1 and mCRY2 in maintaining circadian rhythmicity.
  • To determine the role of mCRY1 and mCRY2 in the negative limb of the circadian feedback loop.
  • To assess the necessity of mCRY1 and mCRY2 for light-induced phase shifting.

Main Methods:

  • Generation and behavioral analysis of mCry1 and mCry2 double-mutant mice.
  • Quantitative analysis of mPer1 and mPer2 mRNA expression in the suprachiasmatic nucleus and peripheral tissues.
  • Assessment of light-induced phase shifting response in mutant mice.

Main Results:

  • Mice lacking both mCRY1 and mCRY2 exhibited behavioral arrhythmicity.
  • Cyclic expression of mPer1 and mPer2 was abolished, with constitutively high mRNA levels.
  • mCRY1 and mCRY2 were found to be dispensable for light-induced phase shifting.

Conclusions:

  • Mammalian CRY proteins (mCRY1 and mCRY2) are essential for the operation of the biological clock.
  • mCRY1 and mCRY2 function in the negative limb of the circadian feedback loop.
  • Light-induced phase shifting of the circadian clock does not require mCRY1 and mCRY2.

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