Circadian surprise: A heat sensor for body-clock synchronization

Although much is known about how light affects the body clock - also known at the circadian clock - it is not well understood which cells or organs sense daily temperature changes or how temperature signals reach the part of the brain that contains the circadian clock.

A variety of organisms, including insects and humans, have evolved an internal circadian clock to regulate patterns of behaviour throughout the day - for example sleep, appetite, alertness and concentration.

Senior study author Dr Ralf Stanewsky, from Queen Mary's School of Biological and Chemical Sciences, explains: "Given the substantial similarity between the fly and mammalian clock, our studies might also help to understand the human circadian clock and in the future perhaps contribute to developing treatments against the negative effects of sleep-disorders and shift-work."

Specially evolved "clock cells" in the brain contain the circadian clock, which needs to be synchronised with the natural environmental cycles every day to prevent them running too fast or too slow.

Dr Stanewsky and colleagues have shown that fly brains were unable to synchronize to temperature cycles when separated from the rest of the body. This is in contrast with the ability to synchronize to light-dark cycles, which can take place with or without a connection to the fly body.

This study, reported today in the journal Neuron, identified a gene called nocte that, when altered, interferes with the fly's ability to synchronize its body clock using temperature signals. Importantly, disabling the nocte gene in nerve cells in the body also prevented the brain's ability to synchronize with temperature.

Dr Stanewsky's group wants to continue their studies on the fruit fly Drosophila and ultimately learn how the fly ensures perfect synchronisation of the circadian clock with the environment.