BACKGROUND Period circadian protein homolog 2 (PER2), or Circadian clock protein PERIOD2, is a component of the circadian clock mechanism which is essential for generating circadian rhythms. PER2 contains glucocorticoid response elements (GREs) and a GRE within the core clock gene PER2 is continuously occupied during rhythmic expression and essential for glucocorticoid regulation of PER2 in vivo. Mice with a genomic deletion spanning this GRE expressed elevated leptin levels and were protected from glucose intolerance and insulin resistance on glucocorticoid treatment but not from muscle wasting. PER2 is an integral component of a particular glucocorticoid regulatory pathway and that glucocorticoid regulation of the peripheral clock is selectively required for some actions of glucocorticoids (1).This gene is a member of the Period family of genes and is expressed in a circadian pattern in the suprachiasmatic nucleus, the primary circadian pacemaker in the mammalian brain. Genes in this family encode components of thecircadian rhythms of locomotor activity, metabolism, and behavior. Circadian expression in the suprachiasmatic nucleus continues in constant darkness, and a shift in the light/dark cycle evokes a proportional shift of gene expression in the suprachiasmatic nucleus. The specific function of this gene is not yet known.A genetic test from a cheek swab can use PER2 expression levels to tell whether a person is an early morning person or a "night owl" (2).PER2 in mice is stabilized by exposure to strong light. PER2 in turn enhances oxygen-efficient glycolysis and hence provides cardioprotection from ischemia. Therefore it is speculated that strong light may reduce the risk of heart attacks and decrease the damage after experiencing one(3).
1. So AY et al. (2009).Proc. Natl. Acad. Sci. U.S.A. 106 (41): 17582–7.
2. Roger Highfield (2008). Telegraph. Retrieved 2008-06-07.
3. Eckle T et al. (2012). Nat Med 18 (5): 774–82.
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