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Acute light exposure suppresses circadian rhythms in clock gene expression
Brian P Grone1, Doris Chang, Patrice Bourgin
1Department of Biology, Stanford University, Stanford, CA, USA.
Journal of Biological Rhythms
|January 22, 2011
Summary
Novel light treatments can disrupt circadian rhythms by causing arrhythmia in Siberian hamsters. This study found that light exposure altered clock gene expression in the suprachiasmatic nucleus (SCN), leading to behavioral rhythm loss.
Area of Science:
- Chronobiology
- Neuroscience
- Molecular Biology
Background:
- Circadian rhythms are endogenous biological processes influenced by light.
- Light can disrupt circadian systems, leading to behavioral and molecular arrhythmicity.
- The suprachiasmatic nucleus (SCN) is the master circadian pacemaker in mammals.
Purpose of the Study:
- To investigate the effects of a novel light treatment on circadian rhythmicity in Siberian hamsters.
- To determine if induced behavioral arrhythmia is associated with molecular changes in the SCN.
- To examine the expression of core clock genes (per1, per2, bmal1, cry1) in the SCN of arrhythmic hamsters.
Main Methods:
- Siberian hamsters (Phodopus sungorus) were subjected to a novel light treatment involving phase advance and delay stimuli over two nights.
- Following light treatment, hamsters were kept in constant darkness.
- SCN tissue was collected at six time points over 24 hours.
- Quantitative RT-PCR was used to measure mRNA levels of per1, per2, bmal1, and cry1.
Main Results:
- The novel light treatment successfully induced circadian arrhythmia in Siberian hamsters.
- Circadian expression of clock genes (per1, per2, bmal1, cry1) in the SCN was eliminated or significantly reduced.
- Overall clock gene expression decreased by 18% to 40% compared to entrained controls.
- Arrhythmia in per1, per2, and bmal1 was characterized by reduced oscillation amplitudes.
Conclusions:
- The novel light treatment effectively disrupts the molecular circadian pacemaker within the SCN.
- Light-induced arrhythmia in behavior is linked to significant alterations in SCN clock gene expression.
- The findings support an amplitude suppression model for light-induced circadian disruption.
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