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

CAMBRIDGE, Mass., March 27, 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. Theres 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, its 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."


Contact: Steve Bradt
Harvard University

Related medicine news :

1. Scientists Isolate Organism That Causes Disfiguring Tropical Disease
2. Scientists uncover how superbug Staph aureus resists our natural defenses
3. Signaling protein helps limit damage in heart attack, Jefferson scientists show
4. Scripps Florida scientists develop a process to disrupt hepatitis C virion production
5. Scientists see Norwalk virus Achilles heel
6. 52 minority scientists receive travel fellowships to Experimental Biology 2008
7. IUPUI scientists report first 3-D view of anti-cancer agent
8. Scientists successfully awaken sleeping stem cells
9. Bonn scientists discover new hemoglobin type
10. Scientists shine new light on inflammatory diseases
11. Scientists identify new leads for treating parasitic worm disease
Post Your Comments:
(Date:11/27/2015)... ... November 27, 2015 , ... The print component ... Today in Atlanta, Dallas, New York, Minneapolis, South Florida, with a circulation of ... distributed nationally, through a vast social media strategy and across a network of ...
(Date:11/27/2015)... , ... November 27, 2015 , ... ... the well-respected Microsoft Dynamics SL User Group (MSDSLUG). Recognized as Microsoft’s official group ... group of Microsoft Dynamics SL software users, partners, industry experts and representatives. Intellitec ...
(Date:11/27/2015)... ... ... CBD College is proud to announce that on November 20th, ... its Diagnostic Medical Sonography program. CBD College is honored to join this very short ... universities in the state of California make the cut. CBD College is officially the ...
(Date:11/27/2015)... ... November 27, 2015 , ... Indosoft Inc., ... the incorporation of Asterisk 11 LTS (Long Term Support) into its Q-Suite 5.10 ... brings Q-Suite 5.10 up-to-date with a version of Asterisk that will receive not ...
(Date:11/26/2015)... ... November 26, 2015 , ... ... Representative. As a franchise owner, Somu now offers travelers, value and care based ... packages, private cruise sales, as well as, cabin upgrades and special amenities such ...
Breaking Medicine News(10 mins):
(Date:11/26/2015)... 26, 2015 ... aanpak combineert immunotherapie met Bremachlorin-photodynamische therapie voor ... ) --> ... ) Uit ... Centrum (LUMC) blijkt ...
(Date:11/26/2015)... 26, 2015 Research and Markets ( ) ... Pacemaker Market Outlook to 2019 - Rise in Cardiac Disorders ... report to their offering. Boston ... Boston scientific and others. --> ... Biotronik, Boston scientific and others. ...
(Date:11/26/2015)... Nov. 26, 2015 Research and Markets ... the "2016 Future Horizons and Growth Strategies ... Supplier Shares, Country Segment Forecasts, Competitive Intelligence, Emerging ... --> --> This ... the Japanese therapeutic drug monitoring market, including emerging ...
Breaking Medicine Technology: