Methylation Sees the Light

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Science  07 Mar 2014:
Vol. 343, Issue 6175, pp. 1059
DOI: 10.1126/science.343.6175.1059-c

Animals, including humans, are sensitive to the length of cycles of light and darkness to which they are exposed. Disruptions of normal cycles by shift work or by exposure to bright lighting during normal periods of darkness can cause medical problems or disrupt learning and memory. Azzi et al. explored the mechanism by which mice responded to light/dark cycles that were shifted to be 22 hours long rather than 24 hours. This environmental change caused alterations in the expression of hundreds of genes in the superchiasmatic nuclei of the brain where the master circadian clock is located. Changes in DNA methylation in over 1000 regions of DNA that are associated with the change in light cycle were also observed. Affected genes included those encoding the clock components Per2 and Cry1, where the changes in methylation were correlated with changes in transcription. Treatment of animals with an inhibitor of DNA methylation reduced the effects of the altered light cycle on the behavior of the animals. Thus, changes in DNA methylation at promoters or within the body of genes may mediate some of the effects of changes in light cycle on physiological function.

Nat. Neurosci. 10.1038/nn.3651 (2014).

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