Although the brain holds a central timekeeper, peripheral tissues run their own 24-hour clocks - known as circadian clocks.
These generate daily cycles of activity, which regulate processes such as liver metabolism and blood pressure.
Charles Weitz of Harvard Medical School in Boston, USA, and colleagues carried out a large-scale comparison of gene activity between mouse liver and heart.
The activity of 8-10% of genes in each tissue oscillate with a 24-hour rhythm, they found using gene chip analysis.
|8-10% of genes in liver and heart oscillate with a 24-hour rhythm.
| Nature |
However, few of these genes are the same between tissues, and each organ's genes show peaks and troughs at different times.
Liver and heart are using their peripheral clocks to regulate different physiological processes, says Weitz.
Like a night-shift worker gets used to different mealtimes, this may allow the body to adapt to changes in the 24-hour routine when necessary.
Meanwhile, the brain's central circadian clock helps peripheral clocks reset when conditions return to normal.