Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New insight into how eyes become wired to the brain discovered by Salk, UT Southwestern scientists

01.08.2002


A crucial piece of the puzzle into how the eye becomes wired to the brain has been revealed by scientists at the Salk Institute for Biological Studies in La Jolla, Calif., and UT Southwestern Medical Center at Dallas.



In findings published in today’s edition of Neuron, the researchers report that a certain class of Eph receptors and ephrin ligands - proteins that cause cells to either repel or attract each other - control how nerve connections from the developing eye form maps that present what we see to visual centers in the brain.

Neurobiologists had long sought to answer how neural maps are established.


"We knew that a certain class of Ephs, the A-class Ephs, were important in mapping the axons on the left-right, or horizontal, axis of the eye into the brain," said Dr. Dennis O’Leary, professor of molecular neurobiology at the Salk Institute and the study’s senior author. "Our new research now identifies how optic axons map the top-bottom, or vertical, axis of the retina into the brain and also defines the biochemical signals used to control this mapping through the analyses of a variety of important mutant mice generated by our colleagues at UT Southwestern."

Earlier work by O’Leary had implicated the B-class Ephs and ephrins, leading to collaboration with Dr. Mark Henkemeyer, assistant professor in the Center for Developmental Biology at UT Southwestern and a co-author of the study. Henkemeyer, whose work focuses on the role of Ephs and ephrins, particularly B-class, in a variety of developmental processes, provided mice that carried mutations in the genes for the EphB receptors.

Today’s published findings don’t have immediate clinical application, Henkemeyer said, but are another important step in understanding how the human nervous system develops and in particular how the retinal axons of the eye form their connections with the brain.

"In my lab, we’re working to understand from a basic molecular level how the nervous system becomes wired," the UT Southwestern researcher said. "If someone gave you a broken Maserati and said, ’Fix it,’ you’d probably like to have a manual that shows how it was put together in the first place. We’re trying to develop that manual for the wiring of the nervous system."

The new research builds on a hypothesis, first suggested in 1963 by Nobel laureate Dr. Roger Sperry, that unidentified molecules guide the mapping of optic axons into the brain. Axons can be likened to electrical wires that grow from nerve cells and carry signals from the nerve cells, much like a cord carries electricity to a lamp.

During eye development, axons grow from different parts of the retina and out the back of the eye, forming the optic nerve. The optic axons grow from four distinct parts of the retina – left-right and top-bottom – and terminate into corresponding specific parts of visual centers in the brain. The wiring scheme allows the brain to properly process the horizontal and vertical dimensions that compose images that are projected onto the retina.

Using the Eph mutant mice provided by Henkemeyer, the Salk Institute researchers, including O’Leary and two of his postdoctoral fellows, Drs. Robert Hindges and Todd McLaughlin, who were co-principal investigators, showed that the interactions of retinal axons expressing B-class Eph receptors with their corresponding ephrins in the brain help guide the axons from the top-bottom or vertical axis of the retina to their proper termination points within the brain. Research from the Salk group had recently shown that A-class Eph receptors and ephrins are the molecules that guide axons from the left-right or horizontal axis of the retina to their proper destinations within the brain.

The Salk group analyzed normal and Eph mutant mice by injecting a fluorescent dye into nerve cells of the retinas. The dye filled the axons and highlighted their paths and terminations in the brain, allowing the researchers to see the wires when the retina and brain were examined under a confocal microscope.

The researchers found that some vertical axis axons in mice lacking proteins EphB2 and EphB3 mapped to incorrect areas of the brain. The study also showed that the vertical axons in normal mice were attracted to their correct destinations by EphB/ephrin-B interaction. In contrast, axons that map along the horizontal axis are directed to their termination points when the A-class Ephs and ephrins involved repel the axons from areas where they don’t belong.

"This work not only helps us to understand how axons normally pathfind during development to reach their intended targets, but it also provides invaluable insights into attractive and repulsive mechanisms that need to be recapitulated following neural injury to rewire the nervous system," Henkemeyer said. "We plan to continue our collaborative effort and investigate these molecules and the mapping process further and hopefully come closer to completing the puzzle."


###
The research was supported by the National Institutes of Health, the March of Dimes Birth Defects Foundation, the Muscular Dystrophy Association and the Swiss National Science Foundation.

To automatically receive news releases from UT Southwestern via e-mail, send a message to UTSWNEWS-REQUEST@listserv.swmed.edu. Leave the subject line blank and in the text box, type SUB UTSWNEWS.


Wayne Carter | ErekAlert!

More articles from Life Sciences:

nachricht Transport of molecular motors into cilia
28.03.2017 | Aarhus University

nachricht Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Transport of molecular motors into cilia

28.03.2017 | Life Sciences

A novel hybrid UAV that may change the way people operate drones

28.03.2017 | Information Technology

NASA spacecraft investigate clues in radiation belts

28.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>