Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

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

31.03.2008
Treelike JAM-B cells are found responsible for detection of upward motion in mice

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."

... more about:
»Retina »Sanes »dendrite »identify »neurons »retinal »upward

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."

Steve Bradt | EurekAlert!
Further information:
http://www.harvard.edu

Further reports about: Retina Sanes dendrite identify neurons retinal upward

More articles from Life Sciences:

nachricht Two Group A Streptococcus genes linked to 'flesh-eating' bacterial infections
25.09.2017 | University of Maryland

nachricht Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Fraunhofer ISE Pushes World Record for Multicrystalline Silicon Solar Cells to 22.3 Percent

25.09.2017 | Power and Electrical Engineering

Usher syndrome: Gene therapy restores hearing and balance

25.09.2017 | Health and Medicine

An international team of physicists a coherent amplification effect in laser excited dielectrics

25.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>