Coordination of circadian timing in mammals

  title={Coordination of circadian timing in mammals},
  author={Steven M. Reppert and David R. Weaver},
Time in the biological sense is measured by cycles that range from milliseconds to years. Circadian rhythms, which measure time on a scale of 24 h, are generated by one of the most ubiquitous and well-studied timing systems. At the core of this timing mechanism is an intricate molecular mechanism that ticks away in many different tissues throughout the body. However, these independent rhythms are tamed by a master clock in the brain, which coordinates tissue-specific rhythms according to light… 

The genetic basis of circadian behavior

  • H. Oster
  • Biology
    Genes, brain, and behavior
  • 2006
In most species, an endogenous timing system synchronizes physiology and behavior to the rhythmic succession of day and night through a set of interwoven transcriptional/translational feedback loops.

Circadian rhythms in stem cell biology and function

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The mammalian circadian clock.

Minutes, days and years: molecular interactions among different scales of biological timing

This review summarizes current findings on the neurobiological basis of the circadian system, both at the genetic and behavioural level, and also focuses on its interactions with interval timing and seasonal rhythms, in order to construct a multi-level biological clock.

Avian Circadian Organization

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Circadian Rhythms in Health and Disease

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Orchestration of gene expression and physiology by the circadian clock

A Web of Circadian Pacemakers




Molecular analysis of mammalian circadian rhythms.

Greater understanding of the cellular and molecular mechanisms of the SCN clockwork provides opportunities for pharmacological manipulation of circadian timing.

Entrainment of the circadian clock in the liver by feeding.

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It is shown that mice lacking the Cry1 or Cry2 protein display accelerated and delayed free-running periodicity of locomotor activity, respectively, which suggests that, in addition to a possible photoreceptor and antagonistic clock-adjusting function, both proteins are essential for the maintenance of circadian rhythmicity.

Resetting central and peripheral circadian oscillators in transgenic rats.

It is hypothesize that a self-sustained circadian pacemaker in the SCN entrains circadian oscillators in the periphery to maintain adaptive phase control, which is temporarily lost following large, abrupt shifts in the environmental light cycle.

Morning and evening circadian oscillations in the suprachiasmatic nucleus in vitro

It is demonstrated that the circadian rhythm of SCN electrophysiological activity, recorded as a single daytime peak in hamster hypothalamic coronal slices, shows two distinct peaks when slices are cut in the horizontal plane, which indicate functional organization ofSCN tissue as a clock with two oscillating components.

Diurnal modulation of pacemaker potentials and calcium current in the mammalian circadian clock

Day–night modulation of Ca2+ current is a central step in transducing the intracellular cycling of molecular clocks to the rhythm in spontaneous firing rate.

Resetting of circadian time in peripheral tissues by glucocorticoid signaling.

It is shown that the glucocorticoid hormone analog dexamethasone induces circadian gene expression in cultured rat-1 fibroblasts and transiently changes the phase of circadian gene Expression in liver, kidney, and heart, however, dexamETHasone does not affect cyclic geneexpression in neurons of the suprachiasmatic nucleus.

Interacting molecular loops in the mammalian circadian clock.

Analysis of Clock/Clock mutant mice, homozygous Period2(Brdm1) mutants, and Cryptochrome-deficient mice reveals substantially altered Bmal1 rhythms, consistent with a dominant role of PERIOD2 in the positive regulation of the Bmal 1 loop.

Absence of Circadian Phase Resetting in Response to Bright Light Behind the Knees

Bright, narrow-spectrum blue light exposure to the back of the knees was reported to reset the human circadian pacemaker in 1998 and was recognized as among the top discoveries that year to Science.