Abstract
The molecular clockwork in mammals involves various clock genes with specific temporal expression patterns. Synchronization of the master circadian clock located in the suprachiasmatic nucleus (SCN) is accomplished mainly via daily resetting of the phase of the clock by light stimuli. Phase shifting responses to light are correlated with induction of Per1, Per2 and Dec1 expression and a possible reduction of Cry2 expression within SCN cells. The timing of peripheral oscillators is controlled by the SCN when food is available ad libitum. Time of feeding, as modulated by temporal restricted feeding, is a potent 'Zeitgeber' (synchronizer) for peripheral oscillators with only weak synchronizing influence on the SCN clockwork. When restricted feeding is coupled with caloric restriction, however, timing of clock gene expression is altered within the SCN, indicating that the SCN function is sensitive to metabolic cues. The components of the circadian timing system can be differentially synchronized according to distinct, sometimes conflicting, temporal (time of light exposure and feeding) and homeostatic (metabolic) cues.
Publication types
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Research Support, Non-U.S. Gov't
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Review
MeSH terms
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ARNTL Transcription Factors
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Animals
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Basic Helix-Loop-Helix Transcription Factors
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Behavior, Animal / physiology
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Biological Clocks / genetics
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Biological Clocks / physiology*
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Cell Cycle Proteins
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Circadian Rhythm / physiology
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Cryptochromes
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Dark Adaptation / physiology
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Drosophila Proteins*
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Eye Proteins*
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Flavoproteins / genetics
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Flavoproteins / metabolism
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Food Deprivation / physiology*
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Gene Expression Regulation / physiology
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Homeodomain Proteins / genetics
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Homeodomain Proteins / metabolism
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Light
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Period Circadian Proteins
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Photoreceptor Cells, Invertebrate*
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Receptors, G-Protein-Coupled
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Suprachiasmatic Nucleus / physiology
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Transcription Factors / genetics
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Transcription Factors / metabolism
Substances
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ARNTL Transcription Factors
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Bmal1 protein, mouse
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Basic Helix-Loop-Helix Transcription Factors
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Cell Cycle Proteins
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Cry2 protein, mouse
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Cryptochromes
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Drosophila Proteins
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Eye Proteins
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Flavoproteins
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Homeodomain Proteins
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Nuclear Proteins
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Per2 protein, mouse
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Period Circadian Proteins
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Receptors, G-Protein-Coupled
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Transcription Factors
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cry protein, Drosophila