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


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 Leave the subject line blank and in the text box, type SUB UTSWNEWS.

Wayne Carter | ErekAlert!

More articles from Life Sciences:

nachricht North and South Cooperation to Combat Tuberculosis
22.03.2018 | Universität Zürich

nachricht Researchers Discover New Anti-Cancer Protein
22.03.2018 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

Modular safety concept increases flexibility in plant conversion

22.03.2018 | Trade Fair News

New interactive map shows climate change everywhere in world

22.03.2018 | Earth Sciences

New technologies and computing power to help strengthen population data

22.03.2018 | Earth Sciences

Science & Research
Overview of more VideoLinks >>>