Our circadian clock sets the rhythm for our cells’ powerhouses -- ScienceDailyCountless genetically controlled clocks tick inside different parts of our bodies, such as the liver, kidneys and heart. Among other things, they initiate many metabolic processes, ensuring that these occur at the optimal time of day. Mitochondria -- small organelles that exist in almost all our cells and supply them with energy -- play an important role in these cellular processes. Until now, it was unclear how exactly the 24-hour circadian rhythm regulated energy metabolism. Fission protein sets the rhythm In most cells, mitochondria connect in a constantly changing network that can adapt to various conditions. Mitochondria can thus fuse together and then divide again. Disruption of this fission-fusion dynamic can lead to health problems. Researchers have now investigated exactly how the mitochondrial network interacts with our internal biological clock by using a combination of in vitro models and clock-deficient mice or mice with impaired mitochondrial fission. Their results show that the mitochondrial fission-fusion cycle is controlled by the fission protein Drp1, which is in turn synchronized by an internal biological clock. This rhythm is integral to determining when and how much energy the mitochondria can supply. "The time of day determines the design of the mitochondrial network, and this, in turn, influences the cells' energy capacity," explains study leader Professor Anne Eckert from the University of Basel's Transfaculty Research Platform Molecular and Cognitive Neurosciences MCN.