Science News & Science Current Events
 
Email a Friend Send to a friend
Printer Friendly Print Scientists learn what's 'up' with a class of retinal cells in mice

Scientists learn what's 'up' with a class of retinal cells in mice

March 28, 2008

Harvard University researchers have discovered a new type of retinal cell that plays an exclusive and unusual role in mice: detecting upward motion. The cells reflect their function in the physical arrangement of their dendrites, branch-like structures on neuronal cells that form a communicative network with other dendrites and neurons in the brain.

The work, led by neuroscientists Joshua R. Sanes and Markus Meister, is described this week in the journal Nature.




"The structure of these cells resembles the photos you see in the aftermath of a hurricane, where all the trees have fallen down in the same direction," says Meister, the Jeff C. Tarr Professor of Molecular and Cellular Biology in Harvard's Faculty of Arts and Sciences. "When you look at these neurons in the microscope, they all point the same way. There's no other cell type in the retina that has that degree of directionality."

The cells, like other retinal neurons, are composed of a round cell body surrounded by a tangle of dendrites. Most retinal neurons distribute their dendrites evenly around the cell body, but the upward motion-detecting cells arrange almost 90 percent of their dendrite tangle exclusively on one side of the cell body.

"This lopsided arrangement literally directs the cell's function, orienting the dendrites downward like roots of great trees," says Sanes, professor of molecular and cellular biology and Paul J. Finnegan Family Director of Harvard's Center for Brain Science. "Because the eye's lens acts as a camera, reversing incoming light rays as they strike the retinal tissue, an object moving up will result in a downward-moving image at the back of the eye -- the exact orientation of the cells' dendrites."

The research builds on efforts by Meister to understand neural processing in the retina, as well as work in Sanes's laboratory to identify and mark neurons in the retina using molecular tags. Recently, they tracked down a family of molecules expressed exclusively by small subsets of retinal cells in mice. One in particular, called JAM-B, was present in cells that had a peculiar distribution and orientation.

According to Sanes, developmental neurologists have long tried to identify different types of neural cells based on their function and anatomy -- how they appeared on the outside.

"But it's a huge limitation because it's essentially a qualitative assessment," he says. "We really need some way to reliably identify and track these cells if we ever hope to study their development. So the emergence of cell-specific molecular markers is a very big deal, because it will do just that. Already we've seen that it helps us identify new kinds of cells we didn't know existed before. Once we have a promising molecule, we can track down the cells that it corresponds to."

"The other important result," continues Sanes, "is that we're actually mimicking how the brain itself identifies its cells. The brain has to be able to reliably recognize and tell apart different kinds of cells, and that's going to happen on a molecular basis. In fact, it's possible that some of the molecules we've identified are, in fact, the same molecules the brain uses to distinguish cell types."

By identifying molecules that are solely expressed by specific types of neurons, scientists hope to gain insights into how nerve cells form synapses, or connections, with other nerve cells -- in short, how the brain controls its development on a molecular basis.

For the moment, however, researchers are busy puzzling over the results of the JAM-B mouse retinal cells.

"Why in the world would mice need to develop cells to detect upward motion"" Sanes wonders. "It's a great mystery."

Harvard University



Related Retinal Cells Current Events and Retinal Cells News Articles Retinal Cells Current Events and Retinal Cells News RSS Retinal Cells Current Events and Retinal Cells News RSS
Retina transplants show promise in patients with retinal degeneration
Preliminary research shows encouraging results with transplantation of retinal cells in patients with blindness caused by retinitis pigmentosa (RP) and age-related macular degeneration (AMD).

Scientists successfully awaken sleeping stem cells
Scientists at Schepens Eye Research Institute have discovered what chemical in the eye triggers the dormant capacity of certain non-neuronal cells to transform into progenitor cells, a stem-like cell that can generate new retinal cells.

Iowa State University researcher identifies eye disease in canines
Sinisa Grozdanic, assistant professor of veterinary medicine at Iowa State University, has identified and named an eye disease not previously known. The disease, Immune-Mediated Retinopathy, or IMR, causes loss of function in retinal cells and, in some cases, blindness in canines.

'Fluorescent' cells give early warning for eye disease
Scientists at the University of Michigan have shown that their new metabolic imaging instrument can accurately detect eye disease at a very early stage.

St. Jude defines eye cancer gene's role in retinal development
A genetic discovery led by scientists at St. Jude Children's Research Hospital helps answer a long-standing mystery about the eyes of vertebrates, and may translate into a deeper understanding of how genes coordinate the complex process of eye formation and how a rare pediatric eye cancer progresses.

Mouse vision has a rhythm all its own
In the eyes of mammals, visual information is processed on a daily schedule set within the eyes themselves-not one dictated by the brain, according to a new report in the August 24 issue of the journal Cell, a publication of Cell Press.

Fish eyes could hold clue to repairing damaged retinas in humans
A special type of cell found in the eye has been found to be very important in regenerating the retina in zebrafish and restoring vision even after extensive damage.

High arterial pulse pressure associated with high-tension open-angle glaucoma
Individuals with a high pulse pressure (the difference between the systolic [top number] and diastolic [bottom number] blood pressure), appear to have an increased risk for high-tension open-angle glaucoma.

UK scientists set their sights on cure for AMD
A groundbreaking surgical therapy capable of stabilising and restoring vision in the vast majority of patients who currently suffer blindness through Age-Related Macular Degeneration (AMD) is to be taken to clinical trial by scientists and clinicians at the UCL Institute of Ophthalmology, Moorfields Eye Hospital and the University of Sheffield.

Stem cell therapy shows promise for rescuing deteriorating vision
For the millions of Americans whose vision is slowly ebbing due to degenerative diseases of the eye, the lowly neural progenitor cell may be riding to the rescue.
More Retinal Cells Current Events and Retinal Cells News Articles
Neurophysiological Aspects of Color Vision in Primates: Comparative Studies in Simiarn Retinal Ganglion Cells and Human Visual System : Studies in Br (Studies of Brain Function)
by Eberhart Zrenner

Central retinal vein occlusion in sickle cell disease.(Case Report): An article from: Southern Medical Journal
by Syed Hasan, Mamoon Elbedawi, Oswaldo Castro, Mark Gladwin, Alan Palestine

This digital document is an article from Southern Medical Journal, published by Southern Medical Association on February 1, 2004. The length of the article is 1952 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web...

Attenuated superoxide dismutase induction in retinal cells in response to intermittent high versus continuous high glucose.(Report): An article from: American Journal of Biochemistry and Biotechnology
by Michael A. Ihnat, Ronald C. Kaltreider, Jessica E. Thorpe, Dixy E. Green, Chandrashekhar D. Kamat, Melissa Leeper, Amanda C. Shanner, Linda A. Warnke, Ludovica Piconi, Antonio Ceriello

This digital document is an article from American Journal of Biochemistry and Biotechnology, published by Thomson Gale on January 1, 2007. The length of the article is 5127 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web...



The Retinal Muller Cell: Structure & Function (Perspectives in Vision Research)
by Vijay Sarthy, Harris Ripps

This monograph examines the role of the Müller cell, the main glial element of the retina, in the development, organization, and function of the vertebrate retina. These cells may also play a role in the control of eye growth and in determining the processing of information by surrounding...

Levodopa-producing retinal cell implants show Parkinson's benefit.(Clinical Rounds): An article from: Family Practice News
by Mary Ann Moon

This digital document is an article from Family Practice News, published by Thomson Gale on January 15, 2006. The length of the article is 484 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.Citation DetailsTitle:...

Parallel Processing in the Visual System: The Classification of Retinal Ganglion Cells and Its Impact on the Neurobiology of Vision (Perspectives in Vision Research)
by Jonathan Stone

THE RETINAL GANGLION CELL LAYER.
by J. M. van. Buren



Photoreceptor Cell Biology and INherited Retinal Degenerations (Recent Ad Ances in Human Biology)

This important book presents review articles on the cell biology of photoreceptor and RPE cells, as well as the relationship between this cell biology and inherited photoreceptor degeneration. The chapters have been written by leaders in the field. The vision scientist will see this book as a review of photoreceptor and RPE cell biology, and known molecular bases of many forms of retinitis...

A nonlinear model of spatiotemporal retinal processing: Simulations of X and Y retinal ganglion cell behavior (Technical report CAS/CNS)
by Paolo Gaudiano

The movements in the visual cells and retinal pigment of the lower vertebrates (Contributions from the Zoological Laboratory of the Museum of Comparative Zoology at Harvard College)
by Leslie Brainerd Arey

© 2008 BrightSurf.com