Study reveals little-known cell networks vital to circadian rhythm

May 03, 2007

Circadian rhythm is the basic 24-hour cycle that involves various behaviors, including sleeping and eating, in all living organisms. In mammals, the circadian clock is organized hierarchically in a series of multiple oscillators. At the top of this hierarchy, the suprachiasmatic nucleus (SCN), a region of the brain that is the body"s main rhythmic regulator, integrates light information from the eyes and coordinates peripheral oscillators throughout the body.

By examining effects of genetic mutations at the level of single cells and tissues, the study showed that intercellular mechanisms are in fact essential to the operation of cellular circadian clocks.

"Our study reveals some previously overlooked mechanisms for sustaining cellular circadian rhythm," said Steve A. Kay, whose laboratory spearheaded the research. "Essentially, when cells communicate en masse through these highly networked electrical or neurochemical interactions, the system responds far more effectively."

The SCN intercellular network, Kay said, is necessary not only to stabilize oscillators in the peripheral tissues but also to provide a robust response to various genetic mutations. In fact, the network interactions unique to the SCN can compensate for some genetic defects in the Period (Per) and Cryptochrome (Cry) genes-the clock genes-to preserve circadian rhythm.
In fact, the circadian defects observed in mutant oscillators were clearly more extreme when measured at the tissue and cell levels than demonstrated by behavioral observations.

"Because single cells are ordinarily capable of functioning as autonomous oscillators," Kay noted, "our previous understanding of clock mechanisms has rested precariously on the idea that if we studied behavior, we could assume that same thing was happening at the single cell level. Our study shows that's not the case."

The lack of networked interactions in peripheral tissues may actually be an adaptive feature in most circumstances. SCN cells in vivo must synchronize not only to light-dark cycles but also to one another to coordinate circadian behavior. Lack of coupling may allow peripheral oscillators to anticipate and respond rapidly not only to the synchronizing cues emanating from the SCN but also to physiological signals related to feeding and behavior.

"Future studies should focus on addressing the system impact of these cellular networks," Kay said. "Our results validate clock model predictions previously overlooked or sometimes regarded as model flaws. Newer models are needed to accommodate the novel cell-autonomous phenotypes we uncovered."

Source: Scripps Research Institute

Explore further: Stem cells faulty in Duchenne muscular dystrophy

add to favorites email to friend print save as pdf

Related Stories

LA mayor plans 7,000 police body cameras in 2015

58 minutes ago

Mayor Eric Garcetti announced Tuesday a plan to equip 7,000 officers on the Los Angeles police force with on-body cameras by next summer, making the law enforcement agency the nation's largest to make the ...

Microbiome may have shaped early human populations

2 hours ago

We humans have an exceptional age structure compared to other animals: Our children remain dependent on their parents for an unusually long period and our elderly live an extremely long time after they have ...

Recommended for you

Stem cells faulty in Duchenne muscular dystrophy

10 hours ago

Like human patients, mice with a form of Duchenne muscular dystrophy undergo progressive muscle degeneration and accumulate connective tissue as they age. Now, researchers at the Stanford University School of Medicine have ...

Here's how the prion protein protects us

15 hours ago

The cellular prion protein (PrPC) has the ability to protect the brain's neurons. Although scientists have known about this protective physiological function for some time, they were lacking detailed knowledge ...

Regulation of maternal miRNAs in early embryos revealed

16 hours ago

The Center for RNA Research at the Institute for Basic Science (IBS) has succeeded in revealing, for the first time, the mechanism of how miRNAs, which control gene expression, are regulated in the early embryonic stage.

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.