Navigation Links
Mouse vision has a rhythm all its own
Date:8/24/2007

In the eyes of mammals, visual information is processed on a daily schedule set within the eyes themselvesnot one dictated by the brain, according to a new report in the August 24 issue of the journal Cell, a publication of Cell Press. The researchers found in mice that the eyes normal rhythmic response to light requires only that a molecular "clock" inside the retina go on ticking. The retina is a layer of nerve tissue covering the back of the eyeball, which is often likened to the film in a camera; without it, images can't be captured.

The results offer the first glimpse into the physiological importance of circadian clocks found in organs throughout the body, said Charles Weitz of Harvard Medical School. The retina's apparent independence when it comes to keeping itself on time further challenges the notion that the circadian rhythms of the bodywhich drive regular patterns of physiology and behaviorstrictly follow orders handed down from a "master clock" in the brain, the researchers said.

"We're moving from a dictatorial model of the circadian system to a federal model," Weitz said. He added, however, that the brain's master clock isnt "completely off its pedestal" yet as it might still play a lead role in synchronizing the clocks found in other organs.

It has long been known that the roughly 24 hour circadian clock controlling behavior in mammals is located in the brains suprachiasmatic nucleus (SCN), Weitz explained. Even when animals are placed under conditions of constant darkness, that daily rhythm marches on.

More recently, researchers have discovered that circadian clocks are also distributed in other mammalian tissues, including the retina, multiple brain regions, and many peripheral tissues such as the liver and kidneys. But while scientists had suspected physiological functions for those many timepieces, few studies had addressed the issue.

In the new study, the researchers found that retinas of mice that completely lack a critical component of the clocka gene known as Bmal1showed abnormal gene activity in hundreds of retinal genes and defective electrical responses in inner retinal cells critical for image processing. The animals' photoreceptors still sensed light normally and, upon close examination, their eyes appeared normal.

Mice deficient for the Bmal1clock gene only in their retinas had defects of vision essentially identical to those of mice lacking the gene in all tissues, evidence that the clock's function in the eye itself is the key. By contrast, the retinas of mice with brain lesions that disabled the SCN maintained normal visual responses and the regular ebb and flow of retinal gene activity.

"Circadian clocks in mammals are widely distributed, but except for the SCN clock known to regulate behavior, their physiological functions in vivo have largely been mysterious," Weitz concluded. "The studies described here indicate that an intrinsic retinal circadian clock regulates visual processing in vivo and that it does so autonomously, with no detectable contribution from the SCN or other clocks."

Whether the retina's ability to keep time on its own is the exception, "we don't know," Weitz said. Unlike other tissues, the eye's role as a light sensor does provide its component structures a unique ability to track the environment on their own authority, he noted.

Nonetheless, he said, "our work provides evidence that circadian clocks outside the SCN contribute important physiological functions in mammals. Over evolutionary time, different cell types have likely recruited the circadian clock mechanism inherited from a single-celled ancestor for control of specialized tissue-specific processes," he suggested.


'/>"/>
Contact: Nancy Wampler
nwampler@cell.com
617-386-2121
Cell Press
Source:Eurekalert

Related medicine news :

1. Mouse Allergen Found In Homes Could Trigger Asthma In Kids
2. Researchers Develop Mouse Model Of Brain Tumor
3. German Scientists Create Stem Cells From Mouse Testes
4. Mouse Models To Determine The Cause Of Aggressive Leukemia
5. Mouse Model Beneficial to Study of Head and Neck Cancer
6. Scientists Discover New RNAs in Mouse Testicles
7. Scientists Isolate Leukemia Stem Cells in Mouse Model
8. Mouse Model Demonstrates Immune System Reaction In Chlamydia Infection
9. Mouse Gene With Gene Stutter Will Help Leukemia Research
10. Mouse Study Suggests Anxiety Disorders Take Root in Infancy
11. Rett Syndrome Reversed in Genetic Mouse Model
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:5/27/2016)... ... May 27, 2016 , ... In response ... many who are unaware of the plight of aphasia. In collaboration with the ... “Stroke Awareness” campaign. , The link between stroke and aphasia is relatively unknown, ...
(Date:5/27/2016)... ... 27, 2016 , ... Each year Standard Process Inc. ... is this year’s Life University winner of a $2,500 scholarship from ... Leadership Awards ceremony. , Outerbridge is approaching her last quarter at Life University ...
(Date:5/26/2016)... New Hampshire (PRWEB) , ... May 26, 2016 , ... ... skin care products, has been honored with a 2016 When Work Works Award for ... prestigious award, part of the national When Work Works project administered by the Families ...
(Date:5/26/2016)... ... 26, 2016 , ... Connor Sports, through its Connor Cares initiative, ... Tamika Catchings Legacy Tour that will commemorate the Indiana Fever legend’s hall-of-fame ... in all forms and levels of the game, Connor Sports has committed to a ...
(Date:5/26/2016)... ... , ... There are nearly 14.5 million people living with and beyond cancer ... June 5, 2016, communities around the world will gather to recognize these cancer survivors ... Survivors Day® is an annual worldwide Celebration of Life that is held on the ...
Breaking Medicine News(10 mins):
(Date:5/27/2016)... SAN FRANCISCO , May 27, 2016 ... biotechnology company focused on developing products for Regenerative Medicine, Neurology and ... Commissiong will be presenting at two upcoming investor conferences: ... Conference Center, 730 Third Avenue, New York City ... at 3:00pm Marcum MicroCap Conference   ...
(Date:5/26/2016)... May 26, 2016   Change Healthcare ... analytics, network solutions and technology-enabled services designed ... entered into a strategic channel partnership with ... software solutions and revenue cycle management services ... and rehabilitation clinics to optimize revenue, operational ...
(Date:5/25/2016)... and GERMANTOWN, Maryland , May ... QGEN ; Frankfurt Prime Standard: QIA) today announced that ... with Therawis Diagnostics GmbH to develop and commercialize predictive assays ... market PITX2 as a marker to predict effectiveness of anthracycline ... "We are pleased to partner with Therawis, which ...
Breaking Medicine Technology: