By Sarah C. P. Williams
Development is typically thought to be a one-way street. Stem cells produce cells that mature into specific types, such as the neurons and glia that compose nervous systems, but the reverse isn’t supposed to happen. Yet researchers have now discovered nervous system cells transforming back into stem cells in a very surprising place: inside teeth. This unexpected source of stem cells potentially offers scientists a new starting point from which to grow human tissues for therapeutic or research purposes without using embryos.
“More than just applications within dentistry, this finding can have very broad implications,” says developmental biologist Igor Adameyko of the Karolinska Institute in Stockholm, who led the new work. “These stem cells could be used for regenerating cartilage and bone as well.”
Researchers knew that the soft “tooth pulp” in the center of teeth contained a small population of mesenchymal stem cells, the type of stem cell that can mature into teeth, bones, and cartilage. But no one had conclusively determined where these stem cells came from. Adameyko figured that if he could trace their development, he might be able to recreate the process in the lab, thereby offering a new way of growing stem cells for tissue regeneration.
He and his and colleagues were already studying glial cells, which support and surround neurons that wind through the mouth and gums and help transmit signals of pain from the teeth to the brain. When they added fluorescent labels to a set of glial cells in mice, they saw that over time, some of them migrated away from neurons in the gums toward the inside of teeth, where they transformed into mesenchymal stem cells. Eventually, the same cells matured into tooth cells, the team reported this week in Nature.
Before this experiment, it was generally believed that nervous system cells could not revert back to a flexible stem cell state, so it was a surprise to see that process in action, Adameyko says. “Many people in the community were convinced … that one cell type couldn’t switch to the other,” he says. “But what we found is that the glial cells still very much maintain the capacity” to become stem cells. If researchers can learn which chemical cues in the teeth pulp signal glial cells to transform into mesenchymal stem cells, they could have a new way to grow stem cells in the lab, he adds.
“This is really exciting because it contradicts what the field had thought in terms of the origin of mesenchymal stem cells,” says developmental biologist Ophir Klein of the University of California, San Francisco, who was not involved in the new work. But it’s also just the first step in understanding the interplay between the different cell populations in the body, he adds. “Before we really put the nail in the coffin in terms of where mesenchymal stem cells are from, it’s important to confirm these findings with other techniques.” If that confirmation comes, though, a new source of stem cells for researchers will be invaluable, he says.
Posted in Biology


        Opening Pandora's Box

            Caroline Ash   

         The first woman on Earth, Pandora, had a “box,” or rather a jar, that Zeus commanded her to safeguard and never open. Of course she opened it, and thus evil spread around the world. Recently, an extraordinarily distinctive group of giant viruses that parasitize amoebas were described and named Pandoravirus, not because they contain all evil but merely because they are jar-shaped. Le gendre et al. have added to this still-tiny pantheon with another jar-shaped viral particle 1.5 µm long, containing a rather diminutive 600-kb AT-rich genome (as compared to the up to 2.8-Mb genome seen in Pandoraviruses) and a cytoplasmic replication machinery resembling that of the original Megaviridae. The authors named the virus Pithovirus because Pandora's jar was called a “pithos” in ancient Greek. This virus was revived from a Siberian permafrost sample and infects amoebas. Although named for the jar and not its contents, given its origins, this discovery hints that viruses more evil than Pithovirus might be revived as the tundra melts. 

Science 7 March 2014 Editor Choice: Proc. Natl. Acad. Sci. U.S.A. 111, 10.1073/pnas.1320670111 (2014).


GM maize splits Mexico
Legal challenge to transgenic crops has created a rift in the country’s scientific community.

Laura Vargas-Parada

Maize is central to Mexican cuisine, culture and economy, but the formerly self-sufficient country now imports about one-third of its supply.

 The Mexican scientific community has been torn apart by a legal battle over transgenic maize (corn). Almost a year after activists challenged scientists’ right to plant experimental genetically modified (GM) varieties of the crop that is a staple and symbol of Mexico, maize research is still being stymied by a legal stalemate.

On 5 July 2013, a coalition of activist groups filed a class-action lawsuit to stop the Mexican government granting permits to plant GM maize. That September, a judge ordered a halt to experimental and commercial planting until a final verdict is reached — a resolution that could take months or years.

The lawsuit and ruling have thwarted the plans of multinational companies such as Monsanto, DuPont Pioneer and Dow AgroSciences, which have lobbied for more than a decade to sell their GM maize varieties to Mexican farmers. But they have also stalled public-sector biotechnology researchers who say they are close to producing GM maize strains tolerant to drought and frost, and other varieties with a reduced need for herbicides and fertilizers. These researchers complain that the lawsuit threatens to derail work that could boost maize yields, reduce imports and help to protect against threats such as climate change.

“We are very frustrated, and there is a general sense of despair,” says Beatriz Xoconostle, a plant biotechnologist at the Center for Research and Advanced Studies (Cinvestav) in Mexico City who leads a project to develop drought-tolerant GM maize. “We have been unable to accomplish our objectives.”

Mexico has neither embraced GM technology nor run from it. In 2010, the agriculture and environment ministries authorized commercial planting of GM cotton, and approval for transgenic soya beans followed two years later. By 2013, the country was growing 100,000 hectares of engineered crops — more than any European nation except Spain, although much less than Brazil and Argentina.

But in Mexico, the question of government approval — and public acceptance — of GM maize is much more sensitive. Fears were stoked in 2001, after researchers at the University of California, Berkeley, reported that genetic material from GM maize had flowed into local populations of native maize cultivars (D. Quist and I. H. Chapela Nature 414, 541–543; 2001). For years afterwards, even experimental plantings of GM maize were banned.
In 2009, Monsanto, Dow and DuPont Pioneer were granted approval to grow GM maize for research — as were some academic researchers (see ‘Transgenic tussle’). But those programmes were halted again by the 2013 lawsuit, which was spearheaded by agronomist Adelita San Vicente of the Seeds of Life Foundation, a non-profit organization in Mexico City that opposes GM crops. The suit claimed that transgenic maize threatens the biodiversity of traditional varieties grown by subsistence farmers and smallholders throughout Mexico.
Mexico’s caution over the introduction of GM maize reflects a deep desire to conserve genetic diversity in a crop that is central to the nation’s identity. In the United States, the vast majority of maize is grown to feed livestock and produce ethanol fuel. But in Mexico, 82% of white maize is grown for human consumption, often on small farms planted with traditional, rather than commercial, varieties.

“The richness of genetic diversity of maize in Mexico is invaluable,” says José Sarukhán, national coordinator of the National Commission for Knowledge and Use of Biodiversity (CONABIO), a government research council created in 1992. Sarukhán and other ecologists at CONABIO worry about gene flow from GM to native varieties, and that the wide adoption of GM maize could displace them. They are also concerned that GM seed producers might take legal action against small farmers whose seed ends up containing transgenic material.
“We are not against transgenic maize, but want to raise awareness of the implications of their use, and the consequences when they mix with local varieties,” says CONABIO plant geneticist Francisca Acevedo.
Once self-sufficient, Mexico now imports about a third of its maize, most of it from the United States. Scientists who oppose GM maize argue that domestic production could be boosted with irrigation and infrastructure projects, expanded agricultural-extension education programmes for farmers and careful selection of hybrid seeds and native varieties.

“We are very frustrated, and there is a general sense of despair.”

But government scientists, including Luis Herrera-Estrella, director of the National Laboratory of Genomics for Biodiversity at Cinvestav, see biotechnology as a crucial tool for restoring the country’s maize independence. Xoconostle’s project, for example, seeks to develop drought-tolerant GM maize that can also resist low temperatures. Using antisense RNA, she and her team have modified the plant’s metabolism by inhibiting an enzyme that destroys trehalose, a sugar involved in stress response. The result, a variety called CIEA-9, requires only two-thirds of the water needed by a normal plant. “This strategy is a way to save many of our local maize varieties,” says Xoconostle.
The next stage of this research, and the last step required by Mexican law before Xoconostle can apply for a permit for commercial planting, will be to cultivate 4-hectare experimental plots of CIEA-9 to test productivity. But the team will have to wait until a final decision has been made on the lawsuit before they can go ahead.
Other government crop scientists have kept their research going by moving their field trials to other countries. In November, Herrera-Estrella obtained a permit to plant experimental plots in Argentina. He leads a group developing transgenic maize and soya that require reduced amounts of fertilizer and compete well against weeds. The transgenic plants work by expressing a bacterial gene that codes for phosphite oxidoreductase, an enzyme that transforms the soil mineral phosphite into phosphate, which most plants need to grow and produce energy (D. L. López-Arredondo and L. Herrera-Estrella Nature Biotechnol. 30, 889–893; 2012).
In Argentina, Herrera-Estrella says, regulatory requirements are “more accessible, science-based and sensible”. In Mexico, more than 100 requirements must be fulfilled before a researcher can obtain a permit for experimental planting; some, he says, make the process unaffordable.
But despite her frustration with the current planting moratorium, Xoconostle does not see Mexico’s stringent policies as a problem. “I am happy we have a strict law that regulates very precisely what we will allow to be grown in Mexico,” she says.
Nature 511, 16–17 () doi:10.1038/511016a


Portraits and Their Parasites
Daguerreotypes may seem frozen in time, but their surfaces are living landscapes. Popular in the mid-19th century, daguerreotypes were a precursor to photography created by layering silver on a copper plate and exposing it to light and various chemicals, often including gold. Many have become fuzzy or faded with time, and now researchers have discovered one reason why: Their surfaces are teeming with life. Fungi and various unidentified life forms eat and digest the metals, then excrete gold and silver nanoparticles that disfigure the image. The good news is that the precise mixture of life forms on an unidentified daguerreotype may offer clues to where it was made. And the parasites may even suggest new ways to manufacture nanoparticles through biological processes. http://scim.ag/daguerr

Science 21 February 2014: Vol. 343 no. 6173 p. 824 DOI: 10.1126/science.343.6173.824


Van Gogh’s ‘Ear’ Is on Display
A replica of Vincent van Gogh’s ear is sitting on display at a German art museum, but it’s not made out of plastic. The body part was created from actual cells and DNA obtained from the great-great-grandson of the artist’s brother, the Los Angeles Times reports. Diemut Strebe, a biodesigner who often works on art pieces that cross over with science, grew the material at a hospital and then used a 3D printer to print the cells into an ear shape.
Science 5 Jun 2014



Cortex in Metallic Pastels

Greg Dunn and Brian Edwards, Greg Dunn Design, Philadelphia, Pennsylvania; Marty Saggese, Society for Neuroscience, Washington, D.C.; Tracy Bale, University of Pennsylvania, Philadelphia; Rick Huganir, Johns Hopkins University, Baltimore, Maryland
With a Ph.D. in neuroscience and a love of Asian art, it may have been inevitable that Greg Dunn would combine them to create sparse, striking illustrations of the brain. “It was a perfect synthesis of my interests,” Dunn says.
Cortex in Metallic Pastels represents a stylized section of the cerebral cortex, in which axons, dendrites, and other features create a scene reminiscent of a copse of silver birch at twilight. An accurate depiction of a slice of cerebral cortex would be a confusing mess, Dunn says, so he thins out the forest of cells, revealing the delicate branching structure of each neuron.
Dunn blows pigments across the canvas to create the neurons and highlights some of them in gold leaf and palladium, a technique he is keen to develop further.
"My eventual goal is to start an art-science lab," he says. It would bring students of art and science together to develop new artistic techniques. He is already using lithography to give each neuron in his paintings a different angle of reflectance. "As you walk around, different neurons appear and disappear, so you can pack it with information," he says.
The painting was commissioned for the Johns Hopkins University School of Medicine’s Brain Science Institute, but, Dunn says, “I want to be able to communicate with a wide swath of people.” He hopes that lay viewers will see how the branching structures of neurons mirror so many other natural structures, from river deltas to the roots of a tree. “I want to help people to appreciate the beauty of the brain.”
"It is just gorgeous," says judge Alisa Zapp Machalek. "The fact that science can be in an art museum is something we want to encourage."
Prints of Greg Dunn’s art, including this winning painting, are available at www.gregadunn.com.
Science 7 de Febrero 2014



James Lovelock reflects on Gaia’s legacy
Scientist who features in an exhibition opening today in London, talks about Gaia, climate change and whether peer review is necessary.

A new exhibition at the Science Museum in London features the personal archives of one of the most influential modern scientists; James Lovelock. ‘Unlocking Lovelock: Scientist, Inventor, Maverick’ tells the story of the British scientist’s work in medicine, environmental science and planetary science, and displays documents ranging from childhood stories, doodle-strewn lab notebooks and patents to letters from dignitaries such as former UK prime minister (and chemist) Margaret Thatcher. Also included are several of Lovelock’s inventions, such as the electron-capture detector that enabled the measuring of ozone-destroying chlorofluorocarbons in the atmosphere in the 1970s.
Lovelock, born in 1919, is best known for the ‘Gaia hypothesis’, which proposes that the Earth functions as a self-regulating system, similar to a living organism. The idea sparked controversy when Lovelock and microbiologist Lynn Margulis proposed it in the 1970s, but environmental and Earth scientists now accept many of its basic principles. In 2006, his book The Revenge of Gaia predicted disastrous effects from climate change within just a few decades, writing that  “only a handful of the teeming billions now alive will survive”.

This week Lovelock spoke to Nature about his career, his earlier predictions and his new book, A Rough Ride to the Future (reviewed last week in Nature).

Is climate change going to be less extreme than you previously thought?
The Revenge of Gaia was over the top, but we were all so taken in by the perfect correlation between temperature and CO2 in the ice-core analyses [from the ice-sheets of Greenland and Antarctica, studied since the 1980s]. You could draw a straight line relating temperature and CO2, and it was such a temptation for everyone to say, “Well, with CO2 rising we can say in such and such a year it will be this hot.” It was a mistake we all made.
We shouldn’t have forgotten that the system has a lot of inertia and we’re not going to shift it very quickly. The thing we’ve all forgotten is the heat storage of the ocean — it’s a thousand times greater than the atmosphere and the surface. You can’t change that very rapidly.
But being an independent scientist, it is much easier to say you made a mistake than if you are a government department or an employee or anything like that.

So what will the next 100 years look like?
That’s impossible to answer. All I can say is that it will be nowhere as near as bad as the worst-case scenario.

Are you still pessimistic about the prospect of finding a political solution to climate change?

In your latest book you advocate not trying to halt climate change but exercising what you call a sustainable retreat. Why is that?
I think it is the better approach. To rush ahead and advance is very much the Napoleonic approach to battle. It is far better to think about how we can protect ourselves. If we’re going to do any good, we should be making more effort to keep our own home a suitable place to live in for the future than desperately trying to save somewhere remote. This is particularly true of Britain. We nearly died in the Second World War for lack of food. Our agricultural production hasn’t gone up enough to supply today’s population with what we would need. This is something we should be looking at carefully, not just applying guesswork and hoping for the best.

Will nuclear energy be part of the future, despite the Fukushima nuclear disaster in Japan?
The business with Fukushima is a joke. Well, it’s not a joke, it is very serious — how could we have been misled by anything like that? Twenty-six thousand people were killed by the magnitude-9 earthquake and tsunami [that caused the nuclear meltdown], and how many are known to have been killed by the nuclear accident? None.
[On the Chernobyl nuclear disaster, Lovelock writes in A Rough Ride to the Future: “The most amazing lies were told, still are told and widely believed… Despite at least three investigations by reputable physicians, there has been no measurable increase in deaths across Eastern Europe.”]
A lot of investment in green technology has been a giant scam, if well intentioned.

Do you feel vindicated about the way many of the ideas in the Gaia hypothesis have now been accepted by Earth-systems scientists?
I think it is a matter of scientific politics. In practice, most of the senior biologists I encountered in later times had no problem with the notion at all. But they fought bitterly at first. It was very funny to talk with John Maynard Smith, Bill Hamilton and Robert May [eminent evolutionary and population biologists], and to discover that none of them had read any of my books or papers — they were judging the idea by what their students told them.

Was some of that criticism helpful?
In the early stages it wasn’t. And on the geology side it was something quite different — the tendency of some geologists to keep their heads in the sediments is very strong, and they won’t shift it. I’m very intrigued by the latest attempt to resuscitate the idea that all of climate regulation is done by rock weathering. The geologists keep on ignoring the bacteria.

A 1984 rejection letter from Nature of your paper outlining the Gaia hypothesis is displayed in the exhibition. What do you think of peer review — is it necessary?
Well, as far as I’m concerned, I don’t have any peer review. But I don’t think it is practical to get rid of it. For run-of-the-mill papers, say if somebody comes up with a really neat method for analysing some component of urine or that kind of thing, it is important to keep it. But not on larger topics.

Nature doi:10.1038/nature.2014.15017

09 April 2014



Flies Evade Looming Targets by Executing Rapid Visually Directed Banked Turns

  1. Michael H. Dickinson1,*
Avoiding predators is an essential behavior in which animals must quickly transform sensory cues into evasive actions. Sensory reflexes are particularly fast in flying insects such as flies, but the means by which they evade aerial predators is not known. Using high-speed videography and automated tracking of flies in combination with aerodynamic measurements on flapping robots, we show that flying flies react to looming stimuli with directed banked turns. The maneuver consists of a rapid body rotation followed immediately by an active counter-rotation and is enacted by remarkably subtle changes in wing motion. These evasive maneuvers of flies are substantially faster than steering maneuvers measured previously and indicate the existence of sensory-motor circuitry that can reorient the fly’s flight path within a few wingbeats.

Vol. 344 no. 6180 pp. 172-177 
DOI: 10.1126/science.1248955