The circadian clock stops ticking during deep hibernation in the European hamster.
Hibernation is a fascinating, yet enigmatic, physiological phenomenon during which body temperature and metabolism are reduced to save energy. During the harsh season, this strategy allows substantial energy saving by reducing body temperature and metabolism. Accordingly, biological processes are considerably slowed down and reduced to a minimum. However, the persistence of a temperature-compensated, functional biological clock in hibernating mammals has long been debated. Here, we show that the master circadian clock no longer displays 24-h molecular oscillations in hibernating European hamsters. The clock genes Per1, Per2, and Bmal1 and the clock-controlled gene arginine vasopressin were constantly expressed in the suprachiasmatic nucleus during deep torpor, as assessed by radioactive in situ hybridization. Finally, the melatonin rhythm-generating enzyme, arylalkylamine N-acetyltransferase, whose rhythmic expression in the pineal gland is controlled by the master circadian clock, no longer exhibits day/night changes of expression but constantly elevated mRNA levels over 24 h. Overall, these data provide strong evidence that in the European hamster the molecular circadian clock is arrested during hibernation and stops delivering rhythmic output signals.
Revel
Florent G
FG
Département de Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, Unité Mixte de Recherche 7168/LC2, Centre National de la Recherche Scientifique, Université Louis Pasteur, Strasbourg Cedex, France.
Herwig
Annika
A
Garidou
Marie-Laure
ML
Dardente
Hugues
H
Menet
Jérôme S
JS
Masson-Pévet
Mireille
M
Simonneaux
Valérie
V
Saboureau
Michel
M
Pévet
Paul
P
D000818:Animals; D056926:CLOCK Proteins; D002940:Circadian Rhythm / Q000502:physiology*; D006224:Cricetinae; D005060:Europe; D005786:Gene Expression Regulation; D006605:Hibernation / Q000502:physiology*; D013997:Time Factors; D015534:Trans-Activators / Q000235:genetics
D015534:Trans-Activators; D056926:CLOCK Proteins
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