Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists shed new light on the body’s internal clock

13.12.2002


As mammals, our internal (circadian) clock is regulated by the patterns of light and dark we experience. But how that information is transmitted from the eye to the biological clock in the brain has been a matter of scientific debate. Scientists had suspected that a molecule called melanopsin, which is found in the retina, plays an important role.



Now researchers at Stanford University and Deltagen Inc. have confirmed that melanopsin does indeed transmit light information from the eye to the part of the brain that controls the internal clock. According to the researchers, melanopsin may be one of several photosensitive receptors that work redundantly to regulate the circadian system.

"This study clarifies the role of melanopsin in setting and maintaining the circadian clock," said Bruce O’Hara, senior research scientist at Stanford and co-author of the study published in the Dec. 13 issue of the journal Science.


O’Hara noted that without a circadian clock many behavioral and physiological traits of mammals would be disturbed - including body temperature, activity levels and sleep.

"Instead of being able to sleep for extended periods of time, we would be at the mercy of unpredictable bursts of sleep and activity," added Stanford senior research scientist Norman Ruby, lead author of the study.

Photoreceptors

For a circadian clock to function, it must be able to detect and respond to light. In mammals, the only cells specialized to do this are in the eyes, which means that our eyes not only allow us to see the world but also synchronize our body’s internal rhythms.

Photoreceptors are specialized cells that can detect light and send signals to the brain, which then processes and interprets the information - allowing us to see. Rods and cones, which are located in the retina, are the primary photoreceptors for vision. Researchers first thought that these molecules had dual roles in vision and setting the circadian clock. But experiments showed that animals lacking rods or cones could still modify their internal clocks in response to changing light conditions. This led scientists to hunt for an alternate photoreceptor that could regulate the circadian system.

Melanopsin, a molecule originally found in frog skin, was the most likely suspect. Scientists discovered that melanopsin molecules in frog skin cells sense and respond to light. The molecule later was found in frog and mouse retinas, and complementary studies determined that cells containing melanopsin send signals to different parts of the brain - further evidence of the molecule’s potential role in setting the circadian clock.

The only test that remained was to determine if the circadian clock could function without melanopsin. To accomplish that, Ruby and O’Hara teamed up with Deltagen Inc., a company based in Redwood City, Calif., that specializes in deleting specific genes from mice. Deltagen deleted (or "knocked out") the melanopsin gene in mice. The Stanford group then used the knockout mice to determine the relative role of melanopsin in transmitting light information to the circadian system.

Lowered response

In their Science study, the researchers found that the circadian system in melanopsin-depleted knockout mice had a 40 percent decrease in their ability to respond to changes in light intensity compared with normal mice. This result led the scientists to conclude that, although melanopsin is important, it is not the only molecule involved in setting the circadian clock.

"Melanopsin is one of the key players, but it is not the only player," Ruby and O’Hara explained, noting that the knockout mice, which lacked melanopsin, continued to respond to new light patterns, albeit less efficiently. The researchers concluded that the eye and the brain probably have redundant systems that contribute to regulating and resetting the circadian clock. Such redundancy would be evolutionarily advantageous, they added.

"Deltagen is very pleased with the work flowing from our collaboration with Stanford, and we commend the scientists involved in this study on their work to further elucidate the role of melanopsin in the sleep cycle," said Mark Moore, chief scientific officer of Deltagen Inc. "We believe that our company’s high throughput gene knockout approach, coupled with our comprehensive systems biology analysis program, will continue to be instrumental in leading researchers to gene function - and ultimately to new pharmaceutical targets and drug candidates."

While the Science study confirms that melanopsin can transmit information to the circadian clock, future studies will focus on identifying the relative contributions of other molecules to circadian clock maintenance, Ruby and O’Hara noted.



Other co-authors of the Science study are Thomas J. Brennan and Ximmin Xie of Deltagen, and Vinh Cao, Paul Franken and H. Craig Heller of the Department of Biological Sciences at Stanford. This project was funded by the National Institutes of Health and Deltagen.

Caroline Uhlik is a science-writing intern at the Stanford News Service.

By Caroline Uhlik

CONTACT: Mark Shwartz, News Service: 650-723-9296, mshwartz@stanford.edu

COMMENT: Bruce F O’Hara, Biological Sciences: (650) 725-6510, bfo@stanford.edu
Norman F. ("Bud") Ruby, Biological Sciences: 650-725-6510, ruby@stanford.edu
Nina Ferrari, Deltagen: 650-569-5154, nferrari@deltagen.com

EDITORS: The study, "Role of Melanopsin in Circadian Responses to Light," will be published in the Dec. 13 issue of Science. A copy of the study can be obtained by contacting the AAAS Office of Public Programs at 202-326-6440 or scipak@aaas.org.

Mark Shwartz | EurekAlert!
Further information:
http://www.stanford.edu/dept/biology/indexfac4.html
http://www.deltagen.com
http://www.stanford.edu/news/

More articles from Life Sciences:

nachricht Closing in on advanced prostate cancer
13.12.2017 | Institute for Research in Biomedicine (IRB Barcelona)

nachricht Visualizing single molecules in whole cells with a new spin
13.12.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

A whole-body approach to understanding chemosensory cells

13.12.2017 | Health and Medicine

Water without windows: Capturing water vapor inside an electron microscope

13.12.2017 | Physics and Astronomy

Cellular Self-Digestion Process Triggers Autoimmune Disease

13.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>