Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Unrestrained retina too much of a good thing

18.05.2005


When primitive nerve cells begin forming an eye in the mouse embryo, they are programmed to build a retina. But the ability to see depends upon connecting the retina to the brain via the optic nerve. Unless these embryonic cells are given the right cue at the right time, they mistakenly form a huge eye that consists entirely of retina and lacks the optic nerve.



The discovery that the retina is the ’default’ setting for development in the embryonic eye comes from research by neurobiologist Greg Lemke and his colleagues at the Salk Institute for Biological Studies, published in the current issue of Genes & Development. The scientists carried out their work on the laboratory mouse as a model of human biology. "Our results suggest that the retina is effectively the default pathway for eye development in mammals," said Lemke. The Salk team showed that two chemical cues, or signalling proteins, must be present in the right place at the right time to shut down this default pathway and allow the optic nerve to develop.

The painstaking work of the Salk team has important consequences since controlling the fate of stem cells implanted into the brain is crucial if these cells are to be safely and effectively used in human therapy. "This study gives us a fascinating insight into how the parts of the brain are laid out because it is likely that the same model applies throughout the nervous system," said Lemke. "There are likely to be other brain areas whose development relies on blocking a tendency to turn into the same cell types as their neighbor."


Lemke and co-authors Stina H. Mui, Jin Woo Kim and Stefano Bertuzzi studied eye development in genetically engineered mouse embryos that lacked the two signalling proteins Vax1 and Vax2. The mice developed normally until approximately 10 days after conception, at which point they started to develop one large, folded sheet of retina, instead of a retina and an optic nerve. "We were fascinated by our results because they were so dramatic," said Lemke. "The layers of the retina were perfectly formed but the retina reached all the way to the brain and there was no optic nerve. In effect, without the restraining influence of Vax1 and Vax2 the brain had created one gigantic eye."

The Salk team then spent the next two years uncovering the mechanisms involved. "It’s fairly easy to describe the effect but it’s much tougher to explain what’s going on," said Mui.

Using complex gene expression techniques, the researchers painstakingly discovered that the fate of the eye is determined over the space of just a couple of days by a complex yet remarkably efficient system. The stem cells in the embryo destined to become the eye start out as identical. In response to external chemical messages, a gene called Pax6 is activated and becomes a powerful switch that tells these ’eye’ cells to start developing into the retina. If nothing happens to stop this process, all the ’eye’ cells will continue along this developmental path until one, huge retina is formed. However, this is normally prevented when the ’eye’ cells closest to the centre of the brain start to produce Vax1 and Vax2, which act as chemical brakes on Pax6. As a result, these cells turn into the optic nerve instead.

"Normally Pax6 is turned off in the ventral optic stalk to allow the optic nerve to develop," said Kim. "It’s an incredibly efficient way to control development because you don’t need a completely new pathway for a new structure."

"Pax 6 is a powerful and ancient gene for eye determination," noted Lemke. "It plays this role from fruit flies to humans. As a consequence, its expression must be highly regulated during development." Although the retina is obviously required for sight, Lemke points out that "it’s possible to have too much of a good thing."

Cathy Yarbrough | EurekAlert!
Further information:
http://www.salk.edu

More articles from Life Sciences:

nachricht The birth of a new protein
20.10.2017 | University of Arizona

nachricht Building New Moss Factories
20.10.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>