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 balancing act: An enzyme that links endocytosis to membrane recycling
07.12.2016 | National Centre for Biological Sciences

nachricht Transforming plant cells from generalists to specialists
07.12.2016 | Duke University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

How to turn white fat brown

07.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>