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Peripheral Circadian Clocks-A Conserved Phenotype?
MedLine Citation:
PMID:  23425359     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The circadian system of mammals regulates the timing of occurrence of behavioral and physiological events, thereby optimizing adaptation to their surroundings. This system is composed of a single master pacemaker located in the suprachiasmatic nucleus (SCN) and a population of peripheral clocks. The SCN integrates time information from exogenous sources and, in turn, synchronizes the downstream peripheral clocks. It is assumed that under normal conditions, the circadian phenotype of different peripheral clocks would be conserved with respect to its period and robustness. To study this idea, we measured the daily wheel-running activity (WRA; a marker of the SCN output) in 84 male inbred LEW/Crl rats housed under a 12 h:12 h light-dark cycle. In addition, we assessed the mRNA expression of two clock genes, rPer2 and rBmal1, and one clock-controlled gene, rDbp, in four tissues that have the access to time cues other than those emanating from the SCN: olfactory bulbs (OBs), liver, tail skin, and white blood cells (WBCs). In contrast with the assumption stated above, we found that circadian clocks in peripheral tissues differ in the temporal pattern of the expression of circadian clock genes, in the robustness of the rhythms, and possibly in the number of functional ∼24-h-clock cells. Based on the tissue diversity in the robustness of the clock output, the hepatic clock is likely to house the highest number of functional ∼24-h-clock cells, and the OBs, the fewest number. Thus, the phenotype of the circadian clock in the periphery is tissue specific and may depend not only on the SCN but also on the sensitivity of the tissue to non-SCN-derived time cues. In the OBs and liver, the circadian clock phenotypes seem to be dominantly shaped by the SCN output. However, in the tail skin and WBC, other time cues participate in the phenotype design. Finally, our study suggests that the basic phenotype of the circadian clock is constructed at the transcript level of the core clock genes. Yet, additional posttranscriptional and translational events can contribute to the robustness and periodicity of the clock output. (Author correspondence: shimon.amir@concordia.ca ).
Authors:
Yuval Weigl; Valerie L Harbour; Barry Robinson; Line Dufresne; Shimon Amir
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-2-20
Journal Detail:
Title:  Chronobiology international     Volume:  -     ISSN:  1525-6073     ISO Abbreviation:  Chronobiol. Int.     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-2-21     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8501362     Medline TA:  Chronobiol Int     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Center for Studies in Behavioral Neurobiology/Centre de Recherche en Neurobiologie Comportementale , Concordia University , Montreal, Quebec , Canada.
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