Networking around the clock

Apr 05, 2007

A Brandeis University study published in Cell this week shows for the first time experimentally that the circadian cells in fruit flies function as a network that enables the insects to adapt their behavior according to seasonal changes. This discovery leads the way to understanding how mammals, and presumably humans, adjust physiology and behavior to environmental changes such as short winter days and long summer ones.

For years, behavioral geneticists have known that specific brain cells in Drosophila fruit flies regulate the daily rhythmic behavior according to 24-hour endogenous clock machinery. But until now, scientists had offered only mathematical models to explain how fruit flies and other animals, including humans, adapt to seasonal changes such as fluctuating day length and temperature.

"In this study we show how the 24-hour intrinsic molecular clock can produce a variable output, so that it fits any seasonal condition," said lead author Dan Stoleru. "This is especially exciting because it gives us an understanding of how animals extract vital information from the environment to drive innate behavior such as reproduction, migration or hibernation."

Stoleru, a researcher in the pioneering National Center for Behavioral Genomics lab led by Michael Rosbash, explained that this property is provided by an adaptable brain circuit of oscillating neurons, capable of responding specifically to different environmental cues. Previous research by the same team in the lab of Michael Rosbash had already demonstrated that two groups of neurons, called morning cells and evening cells, keep circadian time, regulating what fruit flies do morning and evening, day in and day out.

By genetically manipulating these groups of cells in this study, Stoleru and his colleagues discovered that the network is dominated by either one group, acting as the master clock, or the other, depending on day length and season. In the summer, the evening cells run the show; when the days become shorter, the morning cells take over.

"Both kinds of clock cells can be masters at different times," said Stoleru, likening the network to an alternating master-slave relationship. "The morning cells like darkness and they become the master clocks in winter, and the evening cells process light information, so they become the masters in the summer, though it all may happen gradually. We don't know how the switch from slave to master actually happens, but at some point, one type of cell appears to take full control."

The study also sheds light on a poorly understood relationship between depression and circadian rhythm. The authors concluded that shaggy, the Drosophila homologue of the human gene GSK-3, is a key part of the biochemical pathway that signals the light changes in the environment to the core clock. GSK-3 is also the target of lithium, a common medication used in a number of mood disorders, including seasonal affective disorder, or winter depression. Interestingly, phototherapy, which involves subjecting the patient to intense pulses of light, has been shown as another effective treatment for various forms of depression.

"The indication that GSK-3 is at the same time a mediator of light effect and a clock molecule in Drosophila raises interesting prospects for understanding the etiology of various mood disorders as well as the mechanisms underlying some of the therapies employed to compensate them," explained Stoleru.

Source: Brandeis University

Explore further: Rare new species of plant: Stachys caroliniana

add to favorites email to friend print save as pdf

Related Stories

New oscillator for low-power implantable transcievers

Oct 24, 2014

Arash Moradi and Mohamad Sawan from Polytechnique Montreal in Canada discuss their new low-power VCO design for medical implants. This oscillator was implemented to provide the frequency deviation of frequency-shift-keying ...

Reading a biological clock in the dark

Oct 21, 2014

Our species' waking and sleeping cycles – shaped in millions of years of evolution – have been turned upside down within a single century with the advent of electric lighting and airplanes. As a result, ...

Study sheds light on genetic 'clock' in embryonic cells

Nov 13, 2012

As they develop, vertebrate embryos form vertebrae in a sequential, time-controlled way. Scientists have determined previously that this process of body segmentation is controlled by a kind of "clock," regulated by the oscillating ...

Recommended for you

Rare new species of plant: Stachys caroliniana

20 hours ago

The exclusive club of explorers who have discovered a rare new species of life isn't restricted to globetrotters traveling to remote locations like the Amazon rainforests, Madagascar or the woodlands of the ...

Mysterious glowworm found in Peruvian rainforest

23 hours ago

(Phys.org) —Wildlife photographer Jeff Cremer has discovered what appears to be a new type of bioluminescent larvae. He told members of the press recently that he was walking near a camp in the Peruvian ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.