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The coupling of central and peripheral circadian oscillators in the mammalian circadian system by scope of Period1 expression profile Rika NUMANO 1 , Hajime TEI 1 1Laboratory Structural Genomics, Human Genome Center, Institute of Medical Science, The University of Tokyo Keyword: 哺乳類概日リズム , 時計遺伝子勘Reriod1 , 視交叉上核SCNと末梢組織 , カップリング pp.734-743
Published Date 2001/10/10
DOI https://doi.org/10.11477/mf.1431901465
  • Abstract
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The biochemical, physiological and behavioral processes are under the control of internal clocks with the period of approximately 24 hr. Circadian rhythms persist under a constant condition and can be entrained by environ-mental cues, such as light. Many physiological and behavioral studies have revealed that the central circadian pace-maker is located at the suprachiasmatic nucleus (SCN) of the hypothalamus in mammals.

Many clock gene, from Period1 (Per1) down, Per2 and Per3, clock, Bmall, Cryptochromel (Cry1) , Cry2 open the way to uncover the molecular mechanism of mammalian circadian rhythms. The exquisite balance of rhythmic ex-pression between these clock genes keeps the mammalian circadian system by some mutant animal reports with abnormal rhythms. The expression of Per1 oscillates autonomously in the SCN under light and dark (LD) and con-stant dark (DD) conditions and is induced immediately after a light pulse. These facts indicate the circadian oscil-lation and the induction of Per1 expression by light in the SCN have important roles in the mammalian circadian systems. In addition, the rhythmic expression of mPer1 is shown also in some peripheral tissues. We can consider Per1 expression as a good indicator of mammalian circadian rhythms in both SCN and peripheral tissues.

In mammals, the SCN contains autonomous circadian oscillators that act as a pacemaker at the top of the hier-archical circadian system. Some external stimulation like light conditions give firstly to the SCN and effect to pe-ripheral tissues by coupling with the SCN. In order to understand the relationship between the circadian oscilla-tior of the central and peripheral rhythms, we have constructed Per1 :: luc transgenic rats, and a realtime morning system of Per1 expression. It suggests that the daily rhythm of luciferase emission in the SCN is autonomously maintained and independent of other structures and that daily oscillations in peripheral tissues are maintained by some signals from the SCN. In addition, we compared resynchronized abilities in response to 6 hour advance phase shift and delay phase shift of the environmental light cycle among emission rhythms from the SCN, and from peripheral tissues and locomotor behavior in Tg rats. The circadian rhythm in the SCN shifted most rapidly within one day, while the circadian rhythms in peripheral tissues and locomotor rhythms took more than two days until synchronizing to a new light cycle. These data suggest that a self-sustained circadian pacemaker in the SCN entrains circadian oscillators in the periphery to maintain each adaptive phase control.

Moreover, the restricted feeding entrained the phase of Per1 expression rhythm in the liver independently of the SCN and the light cycle. It suggests that the peripheral tissues have the circadian oscillators coupled with SCN central oscillator thought specific rhythmic behavior.

I think it very effective to research the reference and independence between central and peripheral tissues in circadian clock system. It is because that we can understand the advance of efficient system by the specialization and integration of some tissues. It has been very convenient if we could control our circadian rhythms freely. The development of this field is also put social hopes not only academic.


Copyright © 2001, Igaku-Shoin Ltd. All rights reserved.

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電子版ISSN 1882-1243 印刷版ISSN 0001-8724 医学書院

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