Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mexican salamander helps uncover mysteries of stem cells and evolution

12.07.2010
Dr Andrew Johnson is speaking today (12 July) at the UK National Stem Cell Network annual conference. He and his team from the University of Nottingham have been using a Mexican aquatic salamander called an axolotl to study the evolution and genetics of stem cells - research that supports the development of regenerative medicine to treat the consequences of disease and injury using stem cell therapies.

This team has found that there are extraordinary similarities in the development of axolotls and mammals that provide unique opportunities to study the properties of embryonic stem cells and germ cells. These findings are underpinned by a novel theory of evolution that unifies the diversity of mechanisms in animal developmental into a single conceptual framework.

Dr Johnson said "We've produced evidence that pluripotency – the ability of an embryonic stem cell to become absolutely any kind of cell – is actually very ancient in evolutionary terms. Even though received wisdom is that it evolved with mammals, our research suggests that it was there all along, just not in many of the species that people use in the lab. In fact, pluripotent cells probably exist in the embryos of the simple animals from which amphibians evolved.

"Axolotls, unlike many of the frogs, fish, flies and worms that are used in the lab, have pluripotent cells in their embryos that are the equivalent to those found in embryos from mammals, in that they can produce germ cells, in addition to somatic cells, a property known as ground-state pluripotency. And from a practical perspective, axolotl embryos will provide a very useful tool for understanding how to manipulate embryonic stem cells for modern regenerative medicine."

Axolotls are salamanders that retained primitive characteristics of the first amphibians, the animals descended from fish that moved onto land about 385 million years ago. These early amphibians were the ancestors of every land dwelling vertebrate, including humans. This places axolotls in a perfect position to understand how vertebrates evolved on land.

Dr Johnson continued "We've found that the genetic mechanisms controlling the development of salamander embryos were not changed as amphibian embryos evolved into those of reptiles and then, later, mammals. This explains why newts (salamanders) look so much like lizards (reptiles), and since mammals evolved directly from reptiles it makes sense that the genetic mechanisms controlling embryo development remain largely unchanged from axolotls to humans. Axolotl embryos are therefore far more similar to those of humans than the more commonly studied embryos of frogs and fish that most development researchers use.

"We recently found out that pluripotency in axolotls and mammals depends on a gene called Nanog, which frogs do not have. Therefore we think that the Nanog gene was lost from the frog genome after frogs and salamanders evolved separately from their common amphibian ancestor. This is contrary to a long-held opinion that ground-state pluripotency evolved with mammals and suggests that pluripotency could actually be one of the most ancient features of embryos. But since evolution depends on generating advantageous changes, and pluripotency seems to be a good thing – we had to ask ourselves why would frogs have lost the Nanog gene, and with it pluripotency?""

Through work to explore why frogs might have lost pluripotency Dr Johnson and colleagues developed a new theory of evolution in 2003. This theory says that a key driver of vertebrate evolution is the relationship of the germ cells, which become sperm and egg, and the rest of the body, called the soma.

Dr Johnson said "The reason that losing pluripotency would have been an advantage to frogs, for example, is that it has actually made it possible for them to diverge into numerous closely related species – it is possible for them to make far more frequent fairly subtle changes in the evolution of their body shape and physiology. In axolotls and humans it has been necessary to keep a far more rigid arrangement of the soma and therefore they have not diverged into multiple closely related species. And the reason for this is that there are two quite different ways of producing germ cells."

The embryos of most lab animals, including frogs but not mice, contain material called germ plasm, and germ plasm has the role of instructing cells to become the primordial germ cells which go on to become sperm and egg. But axolotls are different; Dr Johnson's team found that their embryos actually don't contain germ plasm and instead they use a system very similar to mice and humans. Axolotls produce their primordial germs cells from pluripotent cells – similar to embryonic stem cells – by a process called induction.

Dr Johnson said "Within our new theory of evolution pluripotency came first and so germ plasm would have to have evolved independently several times in species within the branches of the tree, for example in frogs and many fish. This is a process called convergent evolution – where a common advantage leads to several species developing features that make them appear more similar, rather than less.

"What is the advantage of germ plasm such that it would have evolved several times? We had to resolve the argument that germ plasm wasn't necessary because pluripotency did the job just fine. We knew that with germ plasm pluripotency is not necessary, because the embryos contain primordial germ cells anyway. This explains why the Nanog gene became dispensable, and was lost from the DNA but it doesn't explain what is the advantage to having germ plasm."

Dr. Johnson and his colleagues suggest that the evolution of germ plasm liberates the soma of an organism to evolve more rapidly, simply because the embryo doesn't need to induce germ cells – they are already there because of germ plasm. As a result of this, the genetic mechanisms that control the soma are free to evolve, because they are no longer occupied with producing the signals that induce primordial germ cells from pluripotent embryonic cells.

Dr Johnson concluded "Organisms with germ plasm evolve more rapidly, and produce more species than those without it because there is a great deal more genetic flexibility. So, in the case of frogs, the selective advantage to having lost pluripotency in favour of germ plasm is the freedom to evolve many more species of frogs, which can inhabit many different environments. The down side is that once frogs evolved they never gave rise to anything but other frogs. On the other hand, because salamander embryos contain pluripotent cells they had the raw material to evolve completely new structures such as extraembryonic membranes, which are fundamental to the development of reptiles and mammals.

"We think that ultimately, the germ line-soma relationship is likely to be a major contributor to the astonishing diversity of species that inhabit the earth."

CONTACT

UKNSCN Media Office email: ukpo@uknscn.org or nancy.mendoza@bbsrc.ac.uk, Tel: 01793 413 355, Mob: 07785 710 536

NOTES TO EDITORS

IMAGES AVAILABLE TO DOWNLOAD HERE: http://workspace.meltwaterdrive.com/share/9CB9395001

About UKNSCN

The UK National Stem Cell Network acts as a network for stem cell researchers and all stakeholders. It aims to bring coordination and coherence to a range of national and regional activities in the field of stem cell research. Its overall mission is to promote and enhance the coordination of research across the sub-disciplines of stem cell science, thereby helping to speed to translation basic research into therapeutic applications.

2010 will be the third UKNSCN Annual Conference, following on from successful events in Edinburgh (2008) and Oxford (2009).

The UKNSCN currently receives financial support from four of the UK Research Councils:

Biotechnology and Biological Sciences Research Council (BBSRC)
Economic and Social Research Council (ESRC)
Engineering and Physical Sciences Research Council (EPSRC)
Medical Research Council (MRC)
The Network operates for all stakeholders in UK stem cell research. The secretariat is operated through BBSRC on behalf of all the Government sponsors of stem cell research, including the Research Councils, the Department of Health, the Department for Business, Innovation and Skills and the Technology Strategy Board. Its work is governed by a sponsors' Management Board, supported by an expert Advisory Committee.

Nancy Mendoza | EurekAlert!
Further information:
http://www.uknscn.org

More articles from Life Sciences:

nachricht Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz

nachricht Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>