# News this Week

Science  04 Sep 2009:
Vol. 325, Issue 5945, pp. 1188
1. Medicine

# Disrupting Hedgehog May Reverse Advanced Cancer, If Only Temporarily

1. Sam Kean

In the first clinical proof of its kind, a drug has dramatically shrunk cancerous tumors by disrupting a key genetic pathway. But a study targeting one deadly brain cancer, medulloblastoma, ended in disappointment as the patient's once-tamed tumor quickly developed resistance to the drug and killed him.

The drug, GDC-0449, was developed at Genentech in San Francisco, California. It locks onto and deactivates a protein, Smoothened, that activates the Hedgehog signaling pathway, which in turn orchestrates how embryonic stem cells develop. In adults, the Hedgehog pathway is dormant, but it awakens in many cancers.

In a paper published 2 September in The New England Journal of Medicine (NEJM), scientists treated 33 people with one such cancer, basal cell carcinoma, a common skin cancer. The carcinoma had advanced so far that conventional treatments were useless. Nevertheless, after a median treatment of 10 months, 18 patients improved substantially on the drug, and it arrested the spread of cancer in 11 others. Scientists had long suspected that disrupting the Smoothened-Hedgehog link would shrink tumors without messy radiation or chemotherapy. Now they have proof.

Still more dramatic was the response of a 26-year-old man with aggressive medulloblastoma, reported in a second paper in NEJM. Hedgehog signals have been implicated in one-third of human medulloblastoma cases. Tumors had colonized the man's entire body. “He came in very sick, thinned, in a lot of pain, not very active, needing frequent blood transfusions,” says Charles Rudin, associate director of clinical research at Johns Hopkins University in Baltimore, Maryland, who treated the patient. “His prognosis was terrible.”

Other treatment options, including radiation, had failed, so in late April 2008, Rudin began giving the man 540 mg of GDC-0449 daily. By 23 June, he had gained 7 kilograms and reported that he was in far less pain than before. He even began exercising again. The numerous blotches on his positron emission tomography (PET) scans had been reduced to a few isolated islands of cancer. But on 23 July, a PET scan revealed that the cancer had returned in a resistant form and was almost as widespread as before. The young man died 23 September.

Despite the ultimate failure of the treatment regimen, Rudin said that “a dramatic reduction, even if transient, seemed worthy of reporting” because no effective treatments for medulloblastoma exist.

GDC-0449 seems promising for skin cancer, say several experts, and Genentech has already moved into phase II clinical trials. It remains unclear how well the drug will work for medulloblastoma, however. This brain cancer usually targets children, and because the Hedgehog pathway controls aspects of skeletal development, shutting it off might not be safe.

In a separate study published online 2 September in Science (www.sciencemag.org/cgi/content/abstract/1179386), a team at Genentech led by biologist Frederic de Sauvage described the mechanism by which the man's brain tumor developed resistance. The team found that a point mutation in Smoothened, a G-to-C substitution at position 1697, prevented GDC-0449 from binding but did not alter the ability of Smoothened to switch on the Hedgehog pathway.

Further research showed that a similar resistance had developed in mice with medulloblastoma. The point substitution was different but occurred in the exact same spot and interfered with the drug in the same way. That correspondence between humans and mice hints that preventing drugs like GDC-0449 from locking onto Smoothened could be a common way to develop resistance. However, scientists can now study this mechanism, and they hope to devise ways around it. Resistance could develop in skin cancers but is less likely because they are rarely treated with mutation-inducing radiation.

Some scientists question the Genentech team's decision to report the medulloblastoma findings in two separate papers in two different journals—especially because many of the authors overlap. Tom Curran of Children's Hospital of Philadelphia in Pennsylvania praised the papers. But he added: “It really should have been one paper. The molecular biology was built on the back of the clinical observation. Having just a single patient case study [as in the NEJM paper], it's hard to read much into that.” De Sauvage said the work was done separately and that the papers' appearance at the same time was a coincidence.

The class of compounds that includes GDC-0449 could also help contain other cancers, such as ovarian and colorectal cancers, that are not triggered in the same way as medulloblastoma or basal cell carcinoma but that are still partly driven by aberrant Hedgehog signaling. Genentech is already testing drugs along these lines.

2. Archaeology

# Ancient DNA Says Europe's First Farmers Came From Afar

1. Michael Balter

About 11,000 years ago, farming began to replace the hunting-and-gathering lifestyle in the Near East. At first, agriculture spread slowly into Europe via modern-day Turkey, Greece, and Bulgaria. But about 7500 years ago, farming suddenly took off in central Europe, spreading in just a handful of centuries from an epicenter in Hungary and Slovakia to as far east as Ukraine and as far west as France. Rectangular houses sprang up, surrounded by cow pastures and fields of wheat and barley. Researchers have long debated whether this agricultural explosion was sparked by massive migrations of farmers themselves, so-called demic diffusion, or by the spread of farming ideas, known as cultural diffusion.

In a paper published online this week in Science (www.sciencemag.org/cgi/content/abstract/1176869), European researchers present important new data on this question, for the first time directly comparing ancient DNA from European hunter-gatherers and early farmers. They conclude that outside colonizers brought farming to central Europe in “a major migration event that I never would have believed in before,” says team co-leader Joachim Burger of Johannes Gutenberg University, Mainz, in Germany.

Others are impressed but cautious. “It is an important paper” with “very convincing results,” says archaeologist Ron Pinhasi of University College Cork in Ireland, who last week reported similar conclusions from a study of skulls from the two groups. Martin Richards, an archaeogeneticist at the University of Leeds in the United Kingdom, says, “I couldn't help but become quite excited,” despite his own earlier work supporting cultural diffusion. But Richards and others warn that the findings might be due in part to contamination, long the Achilles' heel of ancient DNA studies.

In the study, researchers led by Burger's Johannes Gutenberg University colleague Barbara Bramanti build on a paper they published 4 years ago in Science (11 November 2005, p. 1016). That paper found differences between ancient mitochondrial DNA from early farmers and mtDNA from living Europeans and was interpreted by many as supporting cultural diffusion.

The new study goes much further by fully sequencing ancient mtDNA from the skeletons of 25 early farmers as well as from 20 hunter-gatherers, thus allowing for direct comparison of the two ancient groups. The bones were previously unearthed at sites in Lithuania, Poland, Russia, and Germany and are dated from about 15,000 years ago to 4300 years ago.

The team found that the mtDNA sequences of the farmers were so genetically distinct from those of the hunter-gatherers that they could not be related. For example, hunter-gatherer skeletons featured a high incidence of two genetic markers, called U4 and U5, which were not found in the farmers, and farmers harbored markers N1a and H, which were not found in the hunter-gatherers. Thus, the first farmers were immigrants who did not immediately mate with the locals.

The team also compared the ancient mtDNA from these two groups with mtDNA from 484 living Europeans. There was little genetic similarity between the hunter-gatherers and modern Europeans, suggesting that most living Europeans descend from the incoming farmers, not the indigenous population. Yet the team also found that the genetic differences between the early farmers and living people were greater than would be expected from genetic drift alone, suggesting that intervening events—such as additional waves of migration and later admixture with lingering hunter-gatherers—have also shaped the modern European gene pool.

If so, Pinhasi says, the new findings caution against using modern people's DNA to draw conclusions about ancient populations, an approach that has only recently begun to be supplemented by ancient DNA studies. “Much of the genetic signature of early farmers has perhaps been wiped out by subsequent [migrations],” he says.

But Richards points out that the sample sizes of hunter-gatherers—although impressive for ancient DNA—are too small to make sweeping conclusions. If the hunter-gatherers varied regionally, direct comparisons with the farmers might be less reliable. Ancient DNA expert Eva-Maria Geigl of the Jacques Monod Institute in Paris adds that the team's results were not replicated in an independent lab, so contamination cannot be entirely ruled out. “This is a major problem,” she says. Bramanti counters that “it is impossible to completely exclude human contamination” but adds that the team was “very scrupulous” in trying to minimize it.

The next step, the researchers say, is to find where those immigrant farmers came from. Burger and Pinhasi are already looking for freshly dug skeletons in western Turkey and southeastern Europe.

3. Venezuela

# Dismissal of Senior Scientist for ‘Nonattendance’ Shakes Community

1. Phil Gunson*

CARACAS—The dismissal of a top Venezuelan scientist from a government research institute and threats to dismantle one of its most successful programs have revived accusations that the government of President Hugo Chávez is engaging in political persecution. Reinaldo Di Polo, a physiologist with more than 40 years' experience and over 4000 bibliographic citations, learned at the end of July that he was to be removed from his post at the Venezuelan Institute for Scientific Research (IVIC), the country's premier science agency, on the grounds of “nonattendance” on unspecified dates between January and June of this year.

In statements to the press, IVIC Director Ángel Viloria described the matter as “purely administrative” and accused the press of politicizing it. “It's not a dismissal,” Viloria said. “The man retired on 1 July 1997. He spent all the budget and didn't show up for work. We don't know if all those scientific articles he says he published were done elsewhere.” (Viloria did not return telephone calls from Science seeking further comment.)

Di Polo, along with two dozen other IVIC researchers, belonged to a program known as the PLI (Permanencia en Labores de Investigación), which allows retired scientists to continue working. PLI was introduced because Venezuelan law allows academics to retire after 25 to 30 years' service, precisely when a research scientist is at his or her most productive. PLI members represent about 20% of IVIC's research staff, but on average, PLI members are responsible for 50% more articles published in peer-reviewed journals than other IVIC staff, according to PLI member Gioconda San-Blas, head of the mycology laboratory.

Since retiring, Di Polo—who won Venezuela's national science prize in 2000 for his work in neurophysiology—has produced 38 research papers in international journals. More than half of the research, he says, was done at IVIC. “Nowhere in the world,” Di Polo says, “do research scientists have to punch a card.” Viloria, however, is not impressed with academic credentials. “We can't give preponderance to indices of citations created by commercial consortia. We'll have to evaluate how much sense it makes, for the future of the country, to continue counting publications and prizes,” he said to the press.

In May, President Chávez called on science minister Jesse Chacón, a retired army lieutenant, to “turn the screws” on unproductive scientists and demanded that research projects have direct, practical applications (Science, 29 May, p. 1126). Viloria, whose own research specialty is butterfly taxonomy, said, “We can't keep giving investment priority to issues that are of no interest to the state.” PLI is under review, and “it is likely that this special regime will disappear.”

When Chacón visited IVIC on 25 August, he was handed a letter from its Association of Researchers (AsoInIVIC), pointing out that, far from being an ivory tower, IVIC addresses issues vital to the country's development. “Just to cite a few examples,” the association says, “in the IVIC, research is carried out into many diseases, including dengue, malaria, AIDS, and tuberculosis.”

PLI, says Flor Pujol, who is on the board of AsoInIVIC, “is not just good, it is vital, because there is no new generation [to take over].” IVIC researchers are deeply concerned over budget cuts and what they say is a brain drain stimulated by the authorities' dismissive attitude toward them.

Scientists' greatest fear, however, is that the government is intent on eliminating “bourgeois science” altogether. Claudio Bifano, president of the Venezuelan Academy of Physical, Mathematical, and Natural Sciences, says the country's scientists are “trying to defend internationally accepted principles and values of science and education.” The government, he says, “wants to transform this country into Cuba—and that is the real danger.”

• * Phil Gunson is a writer in Caracas.

4. Education

# Science Needs Kids With Vision

1. Constance Holden

Albert Einstein, who was famously able to conduct physics experiments in his head, once said his “elements of thought are not words but certain signs and more or less clear images.” Einstein would probably make the cut in most modern-day science talent searches. But many of those with exceptional spatial abilities are being missed, claims psychologist David Lubinski of Vanderbilt University in Nashville.

Lubinski, who put his case last week to the National Science Foundation's National Science Board at a workshop on innovation, says that despite their importance in science, particularly in fields such as engineering, robotics, or astronomy, spatial abilities are getting short shrift both in school curricula and in programs trying to spot precocious youths. He estimates that such programs overlook more than half of those with exceptional spatial abilities. “How many Edisons and Fords are we missing?” he asks.

According to educational psychologist David Lohman of the University of Iowa in Iowa City, spatial ability is “the ability to generate, retain, retrieve, and transform well-structured visual images.” Tests cover areas such as visualization (figuring out what happens when a piece of paper is folded, for example), mentally rotating an object, and mechanical reasoning (see illustration). Many talent hunts for gifted elementary and high school students rely on the results of the SAT, which assess verbal and math—but not spatial—skills.

Lubinski and Camilla Benbow of Vanderbilt have found from their analyses of data from the Study of Mathematically Precocious Youth, begun in 1971 at Johns Hopkins University in Baltimore, Maryland, that there is wide variability in spatial abilities even among the one in 1000 children who score over 700 on the math SAT before age 13. Their latest paper, scheduled for publication in the November issue of the Journal of Educational Psychology, shows that spatial abilities “behave in the same way in an average sample” as they do in the hyper-precocious, says Lubinski. Spatial ability roughly correlates with math and verbal ability, but many spatially gifted people are not in the top tier of math or verbal ability. Using data from Project TALENT, a 1960 survey of 400,000 U.S. high school students, they found that among those who scored in the top 1% of spatial ability, 70% did not make it into the top 1% of math or verbal ability. That means they would have been overlooked by most talent searches. But an 11-year Project TALENT follow-up showed that spatial abilities tend to correlate with scientific achievement. For example, 45% of those with science and engineering Ph.D.s were in the top 4% of the spatial ability range, compared with 25% of the bachelor of science degree holders. Fewer than 10% of the Ph.D.s were below the top quartile in spatial ability.

Such data are news even to people in the field. “I was really amazed at the numbers,” says psychologist Nora Newcombe of Temple University in Philadelphia, Pennsylvania, principal investigator for the Spatial Intelligence and Learning Center, a consortium that does research on spatial skills and how to improve them. Newcombe agrees that people with such skills are not getting the attention they deserve in school. As Lubinski says, the typical “highly verbal” high school curriculum “turns them off; they love classes with a big lab component.”

The Belin-Blank International Center for Gifted Education and Talent Development at the University of Iowa, where Lohman is the research director, is interested in developing and validating a new spatial test to add to those it uses for its talent search and has applied for a foundation grant. A nationally normed test in which results can be reliably compared with math and verbal test scores will offer “a new dimension to help us understand why some are more [scientifically] creative than others,” says center director Nicholas Colangelo.

Everyone agrees that spatial tests will disproportionately select boys. Larry Hedges, a statistician at Northwestern University in Evanston, Illinois, has estimated that the ratio of boys to girls in the top 5% of spatial ability is more than 2.3 to 1. For mechanical reasoning, it's about 11 to 1. But Hedges also points out that spatial ability is highly malleable: “You can change it much more than IQ or verbal or math abilities.”

“It's of concern that you would over-identify males if you just make a decision on the basis of this,” notes Newcombe. But, she says, more focus on spatial ability is long overdue: “It's an orphan skill.”

5. ScienceNOW.org

# From Science's Online Daily News Site

A Breathalyzer for Cancer A team of researchers may have come up with a golden idea for diagnosing lung cancer. By coating tiny nuggets of gold with a thin layer of organic material, they've developed an “electronic nose” that, with some additional work, could spot lung cancer instantly by analyzing someone's breath.

Don't Stand So Close to Me In a famous episode of the TV show Seinfeld, a “close talker” makes others uncomfortable by standing mere centimeters from their faces while speaking. What makes this invasion of our personal space so uncomfortable? A new study fingers the amygdala, a region of the brain that acts like a warning bell when someone gets too close for comfort.

Glyptodonts Were Savvy Batters What do ancient armored mammals have in common with Babe Ruth? They both took advantage of the “sweet spot.” New research suggests that some species of giant mammals called glyptodonts swung their hefty tails like baseball bats, landing powerful blows with the spot on their tails that minimizes potentially harmful vibrations for the slugger.

Global Warming Warps Marine Food Webs Teasing apart the complex ways in which global warming will affect ocean life has been tough. But new research suggests that a simple ecological theory may explain at least one piece of the puzzle: the effect on marine food webs. And the news may not be all bad.

6. Ecology

# Last Chance to Save the 'Panda of Indochina'

1. Richard Stone

Is it possible to throw a lifeline to a creature no scientist has ever glimpsed in the wild? “Some days it feels like trying to strategize conservation of unicorns,” says William Robichaud, a zoologist based in Laos. But that's exactly the challenge confronting experts who have kicked off an 11th hour effort to prevent the saola, a rare ungulate, from slipping into oblivion.

At an emergency meeting in Vientiane last month, Robichaud and colleagues hammered out a set of measures that, if implemented within the next year, could give the saola a shot at survival. These include intensified removal of poachers' snares and efforts to shed light on the mysterious beast's biology. A central challenge is to elevate saola in the public consciousness—both on the animal's home turf in Laos and Vietnam and in the minds of donors, as funding for saola conservation is almost nil. “We need to sell the saola as the panda of Indochina,” says Barney Long, a conservation biologist with the World Wide Fund for Nature (WWF). The animal, which resembles an African desert antelope, “is incredibly charismatic and stunningly beautiful,” says Robichaud. “People just don't know it yet.”

To wildlife biologists, the saola is the stuff of legend (Science, 1 December 2006, p. 1380). It was the first large mammal discovered in a half-century when researchers described the species (Pseudoryx nghetinhensis) in 1992 based on pairs of chestnut-brown, tapering horns hanging in homes in Vietnam's Annamite Mountains. The expansion of settlements and roads have allowed poachers to press deeper into remote Annamite habitat, where they set snares for all manner of wildlife. Villagers have been reporting fewer and fewer saola sightings, suggesting that the species is fading from the scene. The total population is at most a few hundred individuals—and may be as low as a few dozen, says Robichaud. The few saola kept in captivity all perished within weeks.

With the doomsday clock ticking, the Saola Working Group (www.asianwildcattle.org/awc_s.shtml) of the International Union for Conservation of Nature's Species Survival Commission met to figure out how to prevent the species from sliding quietly into extinction. The group, headed by Robichaud, concluded that saola “cannot be saved” without stepping up the pace of snare removal and curtailing hunting with dogs.

Experts say there are some grounds for optimism. WWF and Vietnam's Forest Protection Department recently launched a snare-removal campaign in newly protected saola habitat in the Thua Thien Hue and Quang Nam provinces. But the limited effort is “far from perfect,” says Long, who is hoping a donor will materialize to fund intensive snare removal. In the meantime, he says, “snares remain a huge problem across Vietnam.” In Laos, the Nakai-Nam Theun National Protected Area established an enforcement division this year—“a great ray of hope for the species,” says Robichaud. But much of the saola's presumed range in Laos lies outside of national protected areas. How to safeguard those saola, Robichaud says, is “a tough nut to crack.”

The working group also called for improved methods of detecting saola. “The dearth of knowledge of saola ecology, behavior, and current distribution is a significant constraint to planning conservation action,” says Robichaud. One approach is to set out more camera traps—an expensive proposition. Another is to train dogs to sniff out saola dung, which could be identified by DNA analysis. But with only one or two certain samples of saola dung on hand from past captives, that's iffy.

The best hope for rescuing one of the world's most critically endangered mammals may be the most direct: Bring poachers to heel. “Unlike so many other endangered species in Asia, the saola has no high price on its head,” says Robichaud, primarily because it has no value in traditional medicine and is not an important source of bush meat. “This should make conservation of saola relatively straightforward,” he says.

“Donors like winnable causes,” Robichaud says. And what could be more enticing than saving a real-life unicorn?

7. Ecology

# Dam Project Reveals Secret Sanctuary of Vanishing Deer

1. Richard Stone

When Ulrike Streicher set out last year to rescue wildlife on the Nakai Plateau of northern Laos, nearly half of which was flooding as the reservoir behind the Nam Theun 2 Hydroelectric Project's dam filled, she expected to encounter the occasional curiosity. But in just 4 months, her team captured an astounding 38 large-antlered muntjacs—a rare deer that was discovered only in 1994 and was photographed for the first time by a camera trap in the dam area in 2007. “We had our hands on more large-antlered muntjacs than anyone had ever even seen,” says Streicher.

The hands-on experience could be a boon for efforts to study and protect Indochina's more exotic denizens. Streicher's mostly Lao team attached radio collars to several large-antlered muntjacs (Muntiacus vuquangensis) before releasing them in habitat away from the reservoir. Although the animals aren't presently being monitored—that was beyond the Nam Theun 2 Power Company's mission—“it was a great dress rehearsal for learning how to track animals like the saola,” says Streicher, a wildlife veterinarian based in Da Nang, Vietnam, who headed the NTPC wildlife-rescue program.

From June 2008 to February 2009, Streicher's group rescued 294 animals in Nakai's Thousand Island area, including some pygmy loris and unexpected critters such as the colugo, only the second field record of this gliding mammal in Laos. In a July review, the World Bank commended the rescue program as “impressive.” “Uli and her team did a fantastic job, under often difficult conditions,” says Laos-based zoologist William Robichaud.

The fate of the large-antlered muntjac—those Streicher released and the population in general—is not rosy. Unlike the saola (see main text), this heaviest of muntjac species—adult males weigh up to 60 kilograms—is a favorite of hunters. “We tried to be secretive about where we brought captive animals,” Streicher says. “But when you run into a bunch of locals and you are carrying a couple cages, it doesn't take much imagination to figure out what you're up to.” Streicher hopes outside experts will pick up where NTPC left off and join the quest to save the large-antlered muntjac. Otherwise, she warns, “it could be a big scientific loss.”

8. Japan

# How Will Science Fare?

1. Dennis Normile

TOKYO—In an annual rite of summer, the education ministry's budget requests are trimmed by advisory bodies, politicians, and the powerful finance ministry. This year, there is a new twist: The newly elected Democratic Party now has responsibility for finalizing the budget—and no one knows how R&D will fare.

The Democratic Party's platform keys in on the importance of research. But the party also promised to cut wasteful governmental spending, without being specific, and party politicians have called for reining in bureaucracy. “It's very difficult to say at this stage what to expect,” says Reiko Kuroda, a biochemist at the University of Tokyo and a former member of the Council for Science and Technology Policy, the nation's top science advisory body.

The budget request, released on 28 August, includes a new $110 million program to hire graduate students as teaching assistants; a 17% increase, to$2.4 billion, for grants-in-aid for scientific research that supports individuals and small groups; a 29% increase, to $98 million, in funding for regenerative medicine; and a 35% jump, to$2.8 billion, for the space program. The Democratic Party, which has called for more green-energy schemes, might back the ministry's plan to expand R&D into making Japan a low-carbon society by 75%, to $506 million. Hidefumi Kobatake, president of the Tokyo University of Agriculture and Technology, points out that the ousted Liberal Democratic Party squeezed support for national universities by about 1% in each of the past several years; the Democratic Party has pledged to put a stop to the cuts. “We'll be extremely thankful if that happens,” Kobatake says. The ministry has not yet totaled up science-related spending, and at best the over-all science budget will increase “by a few percent,” says Shuichi Sakamoto, director for budget planning for the ministry. The budget will likely be finalized by December; it takes effect next April. 9. ScienceInsider # From the Science Policy Blog The much-ballyhooed report on the future of the U.S. human space program was submitted to the White House on 1 September, or so rumor has it. The so-called Augustine report is the latest in a series of analyses of pressing issues affecting the research community—scientific integrity and biosecurity being the others—that the Obama Administration has chosen to keep under wraps. In the most comprehensive report yet on geoengineering, Britain's Royal Society calls for more research but cautions that the many impacts of global warming won't be solved by any single technology. Many approaches could have substantial side effects, such as worsening drought. India's moon mission, Chandrayaan-1, has come to a shuddering and unexpected halt. The Indian Space Research Organisation lost all contact with the$100 million spacecraft on 29 August after a catastrophic failure of its electronics.

The U.S. Coast Guard wants feedback on a draft regulation designed to prevent invasive species from entering U.S. waters in the ballast water of ships. The Coast Guard says it “will work to elevate the priority” of research to figure out how effective the measure will be.

Citing new test results, Geron Corp. expects to resume its phase I clinical trial using embryonic stem cells to treat spinal cord injury. The U.S. Food and Drug Administration halted the trial after some animals developed small cysts. Spinal cord patients routinely develop much larger cysts.

The Department of Veterans Affairs (VA) announced on 27 August it would opt out of a controversial research project on Gulf War illness, citing “persistent noncompliance and numerous performance deficiencies.” UT Southwestern officials “strongly disagree with the VA's characterization of the facts.”

For more science policy news, visit blogs.sciencemag.org/scienceinsider.

10. History of Science

# The Case of the Midwife Toad: Fraud or Epigenetics?

1. Elizabeth Pennisi

Paul Kammerer has been called the perpetrator of one of the most celebrated scientific frauds of the early 20th century. He has also been defended as the victim of forgery by a lab assistant; some even say he was framed by political or scientific opponents. Now, a new analysis published this week suggests that his infamous experiments may have been the first demonstrations of a recently recognized phenomenon: epigenetics.

The story starts in the early 1900s. Kammerer, an Austrian biologist, argued strongly in favor of the Lamarckian view that traits acquired during an organism's lifetime could be passed on to future generations. He claimed to have observed Lamarckian inheritance in various organisms, including salamanders and tunicates, but his most publicized evidence came from the midwife toad, Alytes obstetricans.

Most frogs and toads mate in water and lay their eggs in aquatic environments. But midwife toads are landlubbers. Males and females copulate on dry land, and males subsequently wrap the strings of eggs around their legs, carrying them around until the embryos are ready to emerge as tadpoles.

Toads that mate underwater have special colored calluses on their forelimbs, called nuptial pads, that enable them to grasp a wet, slippery female. Given their terrestrial preferences, midwife toads lack nuptial pads—at least they did when Kammerer started his experiment.

He confined the toads to a dry, overheated environment, driving them to mate and lay their eggs in water. Most of the eggs died, but the 3% to 5% of offspring that survived had lost the terrestrial habits of their parents. Even in cool, moist environments, they opted to mate and deposit their eggs in water, a preference that Kammerer said persisted for at least six generations, the amount of time Kammerer studied them.

Moreover, by the third generation, Kammerer reported a thickening on the forelegs that, two generations later, was a bona fide nuptial pad. Other traits useful for an aqueous existence appeared and became more pronounced: Eggs developed thicker jelly coats and reduced quantities of yolk; tadpole gills expanded in size.

Finally, when Kammerer bred the “water” toads with untreated toads, he saw these “water” traits appear in the proportions one would expect for Mendelian inheritance. According to science historian Sander Gliboff of Indiana University, Bloomington, Kammerer thought new genes were forming to pass on these traits.

Some of Kammerer's colleagues were aghast, and he came under attack from giants of the scientific establishment. The final blow came in 1926 when herpetologist G. Kingsley Noble of the American Museum of Natural History in New York City examined the last remaining specimen of Kammerer's “water” toads and noticed that India ink had been injected into the toad's forelimbs. “We have proved conclusively that no pads are present,” Noble wrote in the 7 August 1926 issue of Nature. “Whether or not the specimen ever possessed them is a matter for conjecture.” Noble and his colleagues also discounted Kammerer's photos of pads and stained sections, arguing that they could not be verified as belonging to midwife toads.

Less than 2 months later, Kammerer killed himself in the Austrian mountains. Some say he committed suicide because he was discredited; others blame unrequited love. Whatever the cause, Kammerer continued to spark controversy long after he was gone. A book about the case by Arthur Koestler, a TV documentary, and a Soviet movie all portrayed him as a victim. Kammerer is “either cited as one of the paradigms of scientific fraud, how a brilliant person can go astray, or by others as a hero for any form of antiestablishment cases in the sciences,” says Günter Wagner of Yale University.

Now comes Alexander Vargas, an evolutionary developmental biologist at the University of Chile in Santiago, who has taken a close look at the case from a 21st century perspective. In the Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, released on 3 September, he argues that Kammerer's experiments show signs of what are now well-known epigenetic effects. “There are potential mechanisms that can explain these observations that weren't available at that time,” says Azim Surani, a developmental biologist at the University of Cambridge in the United Kingdom. Adds Vargas: It suggests “a tragic case of scientific incomprehension.”

Acquired traits can seem to be inherited because they result from chemical modification of DNA that can be passed on—even enhanced—in subsequent generations. The sequence stays the same, but the addition or removal of methyl groups silences certain genes. These changes are the guts of epigenetics.

Vargas points out that Kammerer also noticed a “parent of origin” effect in which a trait tends to appear only if it's passed on by the right parent. In Kammerer's experiments, if the father was a “water” toad, then 100% of the first generation and three-quarters of the next generation were “water” toads as well. But if the father retained the toad's terrestrial habits, then the reverse was true. This odd observation “only complicated the scenario for Kammerer, increasing suspicions about his data,” Vargas writes. Similar effects have been noted in the inheritance of coat colors in mice, which have been ascribed to epigenetic changes in a gene variant called Agouti variable yellow, Vargas notes.

Vargas suggests that alterations in the jelly coat around the eggs of Kammerer's toads could lead to abnormal methylation of some genes. All vertebrates have such a coating, and its removal just after fertilization can lead to a reduction in DNA methylation in very early embryos, Vargas points out.

Altered methylation patterns affect body size in mammals, particularly hybrids, and parent-of-origin effects influence egg size in birds and may likewise have led to the large water toads and small eggs. “Kammerer could be the true discoverer of non-Mendelian, epigenetic inheritance,” Vargas concludes. And the intensification of these traits over subsequent generations could be a reflection of ever-increased amounts of methylation—akin to the increased darkening of mice carrying a more heavily methylated Agouti variable yellow gene.

Vargas suspects that epigenetics brought out the water traits and that the nuptial pads were a rare recessive trait connected with traits that enabled that small percentage of midwife toads to survive a water gestation. Eventually, two survivors, each with a recessive gene for nuptial pads, mated, causing the pads to appear.

Vargas doesn't explain the India ink that ultimately led to Kammerer's undoing. Koestler and others have ascribed it to an overzealous lab assistant or even Kammerer's scientific or political opponents.

Gliboff is not completely swayed by Vargas's arguments. “It's still hard to see Kammerer as anything but a failure as a scientist,” he says. But Surani's curiosity is piqued. “It would be extremely interesting if someone did really try to repeat [Kammerer's] experiment,” he notes. “I wouldn't be surprised if he turned out to be right.”

11. HIV/AIDS Research

# Potent HIV Antibodies Spark Vaccine Hopes

1. Jon Cohen

If HIV/AIDS researchers had a wish list, at the very top would sit a vaccine that could teach the body to make potent antibodies against the many strains of the virus. Despite 25 years of effort, no such vaccine is in sight, but now they are a step closer. A large team of researchers has identified the most powerful, broad-acting antibodies yet against multiple strains of the virus.

Finding good antibodies is a far cry from developing a vaccine that prods the immune system to produce them. But “broadly neutralizing antibodies” (bNAbs) are rare: Researchers have identified only a half-dozen to date. Now an international group funded mainly by the International AIDS Vaccine Initiative (IAVI) has discovered two new ones that have an unusual potency. “This has actually made me quite optimistic—for once,” says Dennis Burton, an immunologist at the Scripps Research Institute in San Diego, California, who led the research effort.

For many years, Burton says, he thought that if an antibody had a broader reach, it inevitably would be weaker. “I wondered whether there would be any antibody better than the ones we had,” he says. “Well, these are.”

Burton, his graduate student Laura Walker, and 33 other researchers report online 3 September in Science (www.sciencemag.org/cgi/content/abstract/1178746) that the two new antibodies have unusual characteristics that open new avenues of AIDS vaccine research. “It's a great paper that describes very novel antibodies,” says immunologist John Mascola of the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland.

The researchers first collected blood from some 1800 HIV-infected people in Africa, Asia, Europe, and North America. Using novel techniques, they identified 10% who had antibodies that could derail more than a dozen different strains of the virus. This paper focuses on one sub-Saharan African donor; the person did not benefit appreciably from the antibodies, which are no match for HIV once an infection is established.

The researchers sifted through a staggering 30,000 antibody-producing B cells from the donor and isolated two monoclonal antibodies, dubbed PG9 and PG16, that could prevent infection in more than 70% of 162 viral strains tested in cell culture. Not only were they broad acting, but the antibodies worked at minute levels—a magnitude lower than the four best characterized bNAbs so far. “It's an enormous amount of work—a tour de force,” says AIDS vaccine researcher Ronald Desrosiers, head of the New England Primate Research Center in Southborough, Massachusetts.

On a more sobering note, many researchers have tried to make vaccines that elicit previously identified bNAbs. “In the last 5 years, there have been intensive efforts, and no one has succeeded,” Burton says.

Still, Burton and others hope that understanding the unusual way that PG9 and PG16 stop the virus will provide new leads for AIDS vaccine designers. Specifically, HIV's surface proteins attach to immune cells to establish infections. The surface proteins naturally occur in clusters of three, or trimers, and PG9 and PG16 work only against the trimer. Other bNAbs bind to trimers as well as single surface proteins, or monomers. So this suggests that if a vaccine can present the surface proteins to the immune system in the trimeric form, it may have extra punch. It might also help explain why several AIDS vaccines that contain monomeric surface proteins have performed poorly.

Wayne Koff, who heads research and development at IAVI, says PG9 and PG16 are the first of several new bNAbs that he predicts will help guide the field. In particular, researchers hope the antibodies might help crystallographers finally elucidate the structure of a trimer, which occupies another slot on the wish list. “The machine is built and ready to crank out a lot more—and it's very likely to,” says Koff.

12. Origins

# On the Origin of Cooperation

1. Elizabeth Pennisi

How did cooperation evolve when cheaters—those who benefit without making sacrifices—can threaten its stability? In the ninth essay in Science's series in honor of the Year of Darwin, Elizabeth Pennisi discusses the genetic nuts and bolts of cooperation in systems from microbes to humans.

Cooperation has created a conundrum for generations of evolutionary scientists. If natural selection among individuals favors the survival of the fittest, why would one individual help another at a cost to itself? Charles Darwin himself noted the difficulty of explaining why a worker bee would labor for the good of the colony, because its efforts do not lead to its own reproduction. The social insects are “one special difficulty, which first appeared to me insuperable, and actually fatal to my theory,” he wrote in On the Origin of Species.

And yet cooperation and sacrifice are rampant in nature. Humans working together have transformed the planet to meet the needs of billions of people. Countless examples of cooperation exist between species: Cleaner fish pick parasites off larger fish, and nitrogen-fixing bacteria team up with plants, to name just a few.

In some cases, cooperation has fueled key evolutionary transitions, helping to create integrated systems. Worker ants have no offspring of their own and instead feed their queen's offspring in colonies often considered “superorganisms” many thousands of individuals strong. Cells managed to specialize and stay together, giving rise to multicellular organisms. “At each of those levels, formerly independent reproductive units and targets of selection become integrated into a single reproductive unit and target of selection,” notes biologist James Hunt of North Carolina State University (NCSU) in Raleigh.

So pervasive is cooperation that Martin Nowak of Harvard University ranks it as the third pillar of evolution, alongside of mutation and natural selection. “Natural selection and mutation describe how things change at the same level of organization,” he explains. “But natural selection and mutation alone wouldn't explain how you get from the world of bacteria 3 billion years ago to what you have now.” Cooperation leads to integration, and integration to the complexity we see in modern life.

The challenge of cooperation is to explain how self-interest is overcome given the way natural selection works. Darwin suggested that selection might favor families whose members were cooperative, and researchers today agree that kinship helps explain cooperation. But cheaters—those who benefit without making sacrifices—are likely to evolve because they will have an edge over individuals who spend energy on helping others, thus threatening the stability of any cooperative venture. That puzzle has inspired biologists, mathematicians, even economists to come up with ways to explain how cooperation can arise and thrive. Researchers have spent countless hours observing social organisms from man to microbes, finding that even single-celled organisms have sophisticated means of working together. As genomics has come of age, researchers are getting down to the genetic nuts and bolts of cooperation in a variety of systems for the first time.

## All in the family

To help explain the puzzle of how cooperation evolved, Darwin suggested that it might benefit members of a family to help each other. The British biologist William Hamilton took this idea to heart in the 1960s. He formalized modern thinking about cooperation with the proposal that the offspring of relatives counted toward one's individual fitness. Relatives' progeny share some of your genes, so helping them furthers the spread of the shared genes. The more offspring relatives produce, the more those genes will spread. Helpers will therefore evolve if their overall reproductive output rises enough to make up for any loss of direct reproductive output.

Hamilton worked out a formula for predicting “inclusive fitness”—your offspring plus some proportion of your relatives' offspring—and used that as a guide to determining whether cooperation should evolve in various circumstances. He concluded that inclusive fitness could indeed explain the evolution of highly social insects, whose colonies are composed of related individuals, thus solving Darwin's problem.

This concept implies that individuals will behave differently depending on the degree of relatedness. As another Brit, J. B. S. Haldane, was reported to have put it 30 years earlier, “Would I lay down my life to save my brother? No, but I would to save two brothers or eight cousins.”

The idea that kinship helps drive cooperative behavior has proved a powerful one, but it cannot explain all of cooperation. Humans, for example, often cooperate with nonrelatives. “No other species seems to have succeeded in establishing large-scale cooperation among genetically unrelated strangers,” wrote economist Ernst Fehr of the University of Zurich, Switzerland, in the 25 November 2004 issue of Nature.

To help explain our cooperative nature, in the 1970s, Robert Trivers, now at Rutgers University in New Brunswick, New Jersey, came up with the idea of reciprocal altruism—“You scratch my back, and I'll scratch yours,” as he put it. Researchers inspired by his work used computer simulations to approximate what might happen in real life over many generations. Programmers created games in which two players had the option to cooperate and found that cooperation could evolve and be maintained between two people if they did “tit for tat,” following each other's lead in deciding whether to cooperate.

But this progress can't explain how large cooperative groups—in which the chances of re-encountering a helper or a helped person were small—could evolve. Also, researchers had to consider the prospect of cheating: When multiple individuals work together to find food, make a home, or defend their communities, if a few people fail to contribute and became freeloaders, others may follow, destabilizing cooperation altogether.

In 1998, Nowak and Karl Sigmund of the University of Vienna proposed a way around these issues, at least in the case of humans. They developed a mathematical model suggesting that people decide what to do based not only on whether others have helped them but also on whether others have helped others. “Reputations were also important,” Nowak explains. A person with a reputation for helping gets help, even from someone who has not benefited directly from that person in the past. This could allow cooperative strategies in games to be successful and, by extension, cooperative societies to evolve, Nowak argued.

Other game-playing experiments bore this out. In 2004, Robert Boyd of the University of California, Los Angeles, showed through simulations that this strategy worked particularly well if those who did not help or had a reputation for being slackards were shunned and were refused help.

But Fehr thought even this didn't fully explain humans' extremely cooperative nature. In his labor market studies, he found that people tend to be more cooperative than economic theory would predict: Fairly paid employees voluntarily worked harder than predicted based solely on self-interest, for example. He also noticed that people tended to cooperate with strangers, even though there is little chance these interactions would affect their reputations. He wondered what motivational and social forces might drive and sustain this behavior.

After working with many game-playing experiments, Fehr suggested that punishment also plays a key role in making cooperation successful. In 2002, he reported an experiment in which participants decided whether to keep money they were given or contribute some or all of it to a group project. Participants also had the option to punish non-contributors. Punishment was rampant, and about 75% of the time, it was the above-average contributors—“cooperators”—who penalized freeloaders. When punishment was not part of the game, average contributions dropped. Other work has pointed out that over the long term, the mere threat of punishment—rather than punishment itself—is enough to inhibit cheating. So the cost to punish decreases, but the benefit remains.

Nowak thinks altruistic leanings may in part be instinctive, having evolved because for most of human history, small, related groups were the norm, and reputations were always at stake. But he downplays the importance of punishment, as it may have long-term negative effects such as escalating interpersonal conflicts. When individuals encounter each other repeatedly, “rewards work much better” in perpetuating cooperation, he insists. In the 1 January issue of Nature, he and his colleagues concluded, based on modeling experiments, that punishment rarely pays and that refusing to help noncooperators is much more effective. And on page 1272, they report that in repeated games involving 192 subjects interacting in groups of four via a computer, reward led to increased contributions from individuals and a greater payoff for the group. Punishment can work to keep cooperation going, he says, but in those experiments, punitive actions led to a lower payoff and did not change how much people contributed to the group. Given that Fehr's experiments show the opposite, the role of punishment is still a matter of debate.

## Group selection

Others have applied a different focus when thinking about the evolution of cooperation. They have become convinced that competition among groups can foster cooperation within them. In other words, evolutionary forces can act on several levels, with natural selection's push to make individuals less cooperative being countered by competition at the level of the group, because groups with greater cooperation among members tend to survive better. Darwin noted in The Descent of Man that this seemed to be true of human groups. If two tribes were competing, and “the one tribe included a great number of courageous, sympathetic and faithful members, who were always ready to warn each other of danger, to aid and defend each other, this tribe would succeed better and conquer the other,” he wrote.

That is true for more modern warring groups, says Samuel Bowles, an economist at the Santa Fe Institute in New Mexico. “From military history, it's [known] that groups that are more likely to cooperate are more likely to be successful,” he says. Frequent violent encounters with other human groups made such cooperation essential in our past, Bowles and his colleagues have argued.

Their most recent study backs up that contention. In the 5 June issue of Science (p. 1293), Bowles evaluated archaeological evidence from about 50,000 years ago, as well as ethnographic and historical reports on certain hunter-gatherer populations—those whose lifestyles, he argued, came the closest to resembling ancient human societies.

Bowles found that the percent of adult deaths due to warfare ranged from 0% to 46% at the different sites, averaging out to about 14%—significantly higher than the death toll rates in 20th century Europe with its two world wars. Such frequent warfare made altruistic cooperation among group members essential to survival, says Bowles.

Using game theory, he has simulated what happens in war and concluded that humans could have easily evolved what he calls parochial altruism—wherein you help others in the group, independent of familial relationship, and harm outsiders. “It could have promoted a predisposition to cooperate in groups even at considerable cost to the actor,” says Bowles.

## From man to microbe

A lot of effort has gone into understanding how humans got to the point at which they could get along, and a lot of cooperative theory has been developed with Homo sapiens in mind. But it doesn't take a large brain and a winning smile to cooperate. Even bacterial viruses called phages have prospered by working together. In 2005, Joel Sachs and James Bull, both then at the University of Texas, Austin, demonstrated that traits that reduce competing self-interest evolved in two different types of phages. The two phages were introduced into a bacterial strain at the same time. Over many generations, the two began to package their genomes within a single protein coat, ensuring that both would be transmitted to the next host bacterium. One phage eventually lost the genes needed to make its own coat, they reported.

The more researchers look, the more cooperation they find among microbes. Even better, “the same core theories that are used to understand cooperation in humans and other animals can also be applied to microbes,” says Kevin Foster of Harvard. By working with yeast, bacteria, and amoebas, several teams have been able to discern fundamental principles about the evolution of cooperation. “Microbes are experimentally tractable, … and evolutionary dynamics occur over laboratory time scales,” says Jeffrey Gore of the Massachusetts Institute of Technology in Cambridge. Relatedness, cheaters, and other factors all come into play to determine the success of these microscopic cooperative ventures.

For example, Stuart West, an evolutionary biologist at the University of Edinburgh in the United Kingdom, studies a group phenomenon called quorum sensing in the opportunistic pathogen Pseudomonas aeruginosa. Like other bacteria, this pathogen secretes chemical signals that fellow Pseudomonas bacteria in turn respond to by releasing a variety of products, including virulence factors, nutrient-scavenging molecules, and compounds that become the scaffolding for aggregates of microbial cells called biofilms. In the lab, West and his colleagues helped to demonstrate that when Pseudomonas individuals sense the accumulation of other Pseudomonas nearby, thanks to the increasing concentration of certain biochemicals, they increase their secretion of these helpful substances, providing a benefit to all Pseudomonas present.

Two years ago, West's team also showed that this system, like those of humans playing evolutionary games, was vulnerable to cheaters, bacteria that secreted no helpful substances but reaped the benefits of those that did. In one experiment, after 48 hours and seven generations, the population of one type of cheater increased from 1% to 45% of the colony, raising the question of how the cooperative wild type could possibly persist. West thinks that relatedness may be the answer: Wild-type bacteria tend to cluster in high densities, crowding out the mutant cheaters, which have a different genetic makeup.

In the 24 February issue of Current Biology, West's team extended these findings by exploring cooperation and cheating in Pseudomonas when it was growing in high densities on burn wounds in mice. The proportion of cheaters affected the well-being of both microbes and mice, they reported. When more cheaters were present, the mice did better—possibly because fewer virulence factors were being produced—suggesting that one might treat infections of quorum-sensing microbes by introducing cheaters into their midst, says West.

Perhaps the most celebrated social microbe is the slime mold, Dictyostelium, an organism long studied by developmental and cell biologists as a model. More than a century ago, researchers showed that these single-cell amoebae sometimes merge to form stalked fruiting bodies, which produce spores that disperse to more food-rich environments. In the 1980s, researchers recognized that the amoebae forming the stalks were altruistic, giving up their chance at reproduction to help position other amoebae to produce spores. Studies by David Queller and Joan Strassmann of Rice University in Houston, Texas, show that, as with other organisms, cooperation among slime mold amoebae involves tradeoffs and that relatedness matters.

Cheaters are a constant threat: In 2000, Richard Kessin of Columbia University screened for and found such cheating cells, mutants that manage to avoid becoming part of the nonreproductive stalk and instead infiltrate only the fruiting body. If cheaters make up half the population of aggregating amoebae, they can make up about two-thirds the spores in the fruiting body. Working with Baylor College of Medicine and Rice colleagues Gad Shaulsky and Adam Kuspa, Queller and Strassmann have now found more than 100 slime mold genes that confer the ability to cheat. These genes cover the gamut of functions and are involved at different points in the development of the fruiting stalk. “The large number of genes and pathways involved suggest that it may be easy to evolve cheating and difficult to control it fully,” the authors wrote in the 28 February 2008 issue of Nature.

But their work has also shown that amoebae can keep cheating in check, in large part because the mutations that make cheating possible also tend to keep cheaters from getting into the aggregations at all. In laboratory tests, where it's easier to move about, amoebae lacking the cell-adhesion gene called csaA tend to bypass the stalk and settle in as part of the fruiting body, acting as cheaters. But on soil in the wild, the lack of this adhesion protein keeps them from getting into the fruiting-body formation in the first place, says Queller.

The csaA gene is an example of a so-called green-beard gene, a gene that enables an individual to recognize—as one could recognize a green beard—and cooperate with others who carry that same gene. Those with green-beard genes help perpetuate copies of the gene in others, regardless of the degree of relatedness among individuals. In the case of slime mold amoebae, the csaA proteins bind to each other, preferentially linking cells that share this green beard, so that they can produce a stalk and fruiting body.

Few real-world green-beard genes are known. But yeast have one, too—another cell-adhesion protein called FLO1 that leads to clumps, or “flocs,” of individual yeast cells, as shown in 2008 by Harvard's Foster, Kevin J. Verstrepen of the Catholic University of Leuven in Belgium, and colleagues. As in the slime mold amoebae, only yeast with the gene can come together. When the yeast are in a floc, outer cells inadvertently become altruistic, as they shield inner cells from toxins and other environmental stresses, often at a cost to their own well-being.

That yeast and slime molds have been shown to possess green-beard genes speaks to the power of microbial systems to help pin down how cooperation works: Hamilton had predicted the existence of such genes long before they were discovered. Countless other organisms, from termites to meerkats, provide additional opportunities for the study of cooperation. “The origin of sociality is unlikely to be encompassed by a single explanation,” says NCSU's Hunt. “Sociality, like multicellularity, has appeared numerous times, in diverse taxa, and reached many different levels of integration.”

## References

S. Bowles, "Did Warfare Among Ancestral Hunter-Gatherers Affect the Evolution of Human Social Behaviors?" Science 324, 1293 (2009).

E. Fehr and S. Gächter, "Altruistic punishment in humans." Nature 415, 137 (2002).

N. Mehdiabadi et al., "Social evolution: Kin preference in a social microbe." Nature 442, 881 (2006).

M. Nowak, "Five Rules for the Evolution of Cooperation." Science 314, 1560 (2006).

H. Ohtsuki et al., "Indirect reciprocity provides only a narrow margin of efficiency for costly punishment." Nature 457, 79 (2009).

D. Queller et al., "Single-Gene Greenbeard Effects in the Social Amoeba Dictyostelium discoideum." Science 299, 105 (2003).

K. Rumbaugh et al., "Quorum Sensing and the Social Evolution of Bacterial Virulence." Current Biology 19, 341 (2009).

J. Sachs and J. Bull, "Experimental evolution of conflict mediation between genomes." Proceedings of the National Academy of Sciences 102, 390 (2005).

L. Santorelli et al., "Facultative cheater mutants reveal the genetic complexity of cooperation in social amoebae." Nature 451, 1107 (2008).

S. Smukalla et al., "FLO1 Is a Variable Green Beard Gene that Drives Biofilm-like Cooperation in Budding Yeast." Cell, 135, 726 (2008).

S. West et al., "Evolutionary Explanations for Cooperation." Current Biology 17, R661 (2007).

13. American Chemical Society Fall Meeting, 16–20 August, Washington, D.C.

# Sugary Achilles' Heel Raises Hope For Broad-Acting Antiviral Drugs

1. Robert F. Service

At the fall meeting of the American Chemical Society, researchers reported that a protein that binds sugar groups on the outermost proteins of HIV, gumming up the virus's machinery for entering cells, does nearly as well against the SARS and Ebola viruses, showing promise as a broad-spectrum antiviral.

For drug developers, viruses make difficult targets. Their ability to co-opt our cells' own machinery makes them hard to attack without inflicting collateral damage, and their outermost proteins are often covered by sugar groups that shield them from human immune surveillance. But now researchers may have found a way to turn viruses' sugary camouflage into a vulnerability.

Over the past several years, researchers at the U.S. National Cancer Institute (NCI) have discovered three antiviral proteins that bind to sugar groups that commonly decorate viral proteins but are less common on human proteins. Once attached, the antiviral proteins can gum up a virus's machinery for entering cells. The most potent of these, known as griffithsin (GRFT), was first isolated in 2005 and proved to be a potent inhibitor of HIV. At the ACS meeting, Barry O'Keefe, a protein chemist with NCI's Molecular Targets Development Program, reported that GRFT does nearly as well against the SARS and Ebola viruses as it does against HIV. GRFT increasingly appears to be a powerful broad-spectrum antiviral.

“It seems to be very promising,” says Daron Freedberg, a carbohydrate protein specialist with the U.S. Food and Drug Administration's Center for Biologics Evaluation and Research in Bethesda, Maryland. So far, GRFT has been tested only in animals and in cell cultures. But if it works in humans without unacceptable side effects, O'Keefe says, its stability and cheapness to manufacture could make it particularly useful in developing countries.

After discovering GRFT and its kin in standard screenings of natural-product extracts from marine organisms, O'Keefe and his colleagues quickly found that all of the proteins had an affinity for binding to a sugar group called mannose when it is at the end of a chain of sugars. Many newly minted human proteins also sport mannose, but the sugar group is usually later modified in an intercellular compartment called the Golgi apparatus. That means viral proteins, not human proteins, are vulnerable to compounds targeting mannose-rich sugar complexes on proteins.

GRFT does that with gusto. Each GRFT binds to three mannose groups, O'Keefe said at the meeting. Because GRFT molecules typically team up to work in pairs, or dimers, each dimer binds to six mannose groups. When GRFT finds a mannose-rich target, the six mannose binding sites lock it up and don't let go.

For nearly all HIV strains, it takes less than 0.23 billionths of a mole, or nanomoles, of GRFT to inhibit half the viruses in vitro—a standard measure of drug effectiveness known as the compound's IC50, in which the lower the number the more potent the compound. For SARS, GRFT's IC50 is about 50 nanomoles, and for Ebola it is 380 nanomoles. That makes all three mannose binders some of the most powerful antivirals around.

The animal studies are equally compelling. In mice infected with SARS, 70% of the animals that received no antivirals died. By contrast, among those that received an intranasal dose of 5 milligrams per kilogram per day of GRFT for 4 days, 100% lived. With mice exposed to Ebola, one of nature's most lethal viruses, all of the 10 control animals that didn't receive GRFT died within 12 days. In the five groups of 10 animals that each received different injected doses of GRFT, up to 90% survived. Even when they were injected with the antiviral 2 days after being exposed to Ebola, 30% still lived.

O'Keefe says the NCI team plans to test GRFT on flu viruses, including novel H1N1. Meanwhile, one drug company is gearing up for human trials of an anti-HIV formulation, and others may soon be on the way.

14. American Chemical Society Fall Meeting, 16–20 August, Washington, D.C.

# New Trick for Splitting Water With Sunlight

1. Robert F. Service

At the American Chemical Society fall meeting, a team reported incorporating a mimic of the natural catalyst of photosynthesis into a solar cell to create what amounts to artificial photosynthesis: a device that turns sunlight into fuel.

For solar power to become our foremost energy source, researchers will need to find a way to store and move it—preferably in the form of chemical fuel. Plants do that through photosynthesis, with the help of a manganese-based catalyst. At the ACS meeting, a team reported incorporating a mimic of this natural catalyst into a solar cell to create what amounts to artificial photosynthesis: a device that turns sunlight into fuel.

“This is a very nice observation. It's a real step forward,” says Michael Graetzel, a chemist and solar energy expert at the Swiss Federal Institute of Technology in Lausanne. Gerhard Swiegers, a chemist at the University of Wollongong in Australia and a member of the team that reported the new work at the meeting, cautions that the new cells are still too inefficient to make hydrogen at a commercially viable price. But he adds that the team has ideas for boosting the efficiency sharply. “If we can do that, it would be a big deal,” Swiegers says.

In photosynthesis, plants use chlorophyll and other molecules to capture sunlight. The energy excites electrons, which a cube-shaped calcium-manganese-oxide catalyst uses to split water into molecular oxygen, which it releases, and hydrogen ions (protons) that are used to generate chemical energy for the plant.

For several years, researchers led by Charles Dismukes, a chemist at Rutgers University in Piscataway, New Jersey, have toiled to make a synthetic version of the natural manganese catalyst. That has been a challenge because the version in plants uses a complex protein to stabilize the manganese atoms in their cubical shape. Dismukes's team reported making similarly structured mimics several years back and incorporated them into a proton-conducting membrane 2 years ago.

In their current work, the researchers integrated their catalyst-impregnated membrane into a dye-sensitized solar cell (DSSC). In such cells, sunlight captured by an organic dye excites an electron that is injected into neighboring titanium dioxide nanoparticles and ultimately generates an electric current. Earlier this year, researchers led by chemist Thomas Mallouk of Pennsylvania State University, University Park, took this setup one step further by adding an iridium oxide catalyst, which used the excited electrons in DSSC to split water. But iridium is rare and expensive, and the catalyst needs an added electric current to carry out its water-splitting task.

Swiegers, who teamed up with Dismukes and researchers led by Leone Spiccia of Monash University, Clayton, in Australia, reported at the meeting that the manganese catalyst in DSSC splits water without any added juice. Manganese is also abundant and nontoxic. The setup has two electrodes in water, separated by a plastic membrane that allows protons to pass in one direction. At the anode, sunlight is absorbed by a ruthenium dye, which injects excited electrons into neighboring particles of titanium dioxide; the electrons then flow into an external circuit. The manganese catalyst also absorbs sunlight, in this case grabbing electrons from water molecules and passing them to the dye molecules to restore their light-harvesting ability. When stripped of electrons, the water molecules dissociate into molecular oxygen and protons. The protons pass through the plastic membrane to the cathode, where they combine with electrons from the external circuit, generating molecular hydrogen.

Swiegers says the setup must turn out about 15 times more hydrogen to compete with conventional fuels. But he adds that Dismukes's team thinks a key to achieving that boost is to pack more catalyst clusters around the anode while bringing them into contact with the dye molecules. If the researchers pull off that trick, plants may be in for a bit of competition in the sunlight-to-fuels business.

15. American Chemical Society Fall Meeting, 16–20 August, Washington, D.C.

# Altered Microbes Make Dark-Horse Biofuels

1. Robert F. Service

At the American Chemical Society fall meeting, bioengineers reported equipping photosynthetic algae with the metabolic machinery needed to make isobutanol, a potential alcohol biofuel, and tweaking a reluctant microbe to make large quantities of n-butanol, another commercially important chemical.

If researchers can't get the sun to generate fuel directly, some hope microorganisms can finish the job. Two results at the meeting pushed that hope forward. In one, bioengineers equipped photosynthetic algae with the metabolic equipment needed to make isobutanol, a potential alcohol biofuel. In the other, researchers tweaked a reluctant microbe to make large quantities of n-butanol, another commercially important chemical.

Most biofuel efforts have focused on using microorganisms to convert the plentiful sugars in corn and sugar cane into ethanol. Ethanol, however, is far from an ideal fuel. It contains only about 70% as much energy by volume as gasoline does. It requires extensive energy to separate it from water in the reactors in which it's made, and it corrodes engines. Isobutanol and n-butanol, by contrast, carry more energy than ethanol does, separate naturally from water, and are noncorrosive.

Last year, researchers led by chemical engineer James Liao of the University of California, Los Angeles (UCLA), transferred a suite of genes into Escherichia coli, enabling the bacterium to convert sugars into isobutanol. The remodeled E. coli happily churned out isobutanol. But to do the job, it needed to continuously munch sugar, which would add an additional cost to any future commercial version of the technology.

At the meeting, Liao reported that he and his colleagues have now transferred similar isobutanol-making genes into cyanobacteria, blue-green algae capable of photosynthesis. For now, Liao's cyanobacteria produce only tiny traces of isobutanol. But the UCLA team has a proven record of boosting the output of desired molecules from other microbes, and it is already exploring ways to increase the isobutanol output in cyanobacteria. “It's definitely worth pursuing,” says chemical engineer Shang-Tian Yang of Ohio State University in Columbus. “If someone can make it happen, it will be a big breakthrough.”

Yang's team reported progress of its own. Microbes don't naturally make isobutanol. But one, a strain of Clostridium, makes n-butanol, a close chemical relative that is widely used in industry and is being considered as a biofuel. Clostridium has proven difficult to engineer and is a slow grower. But at the meeting, a member of Yang's team reported that by growing the bugs in a specially designed bioreactor, they had evolved a strain able to produce 30 grams per liter of n-butanol, roughly twice the output of the organisms currently used to make the compound commercially.

“That's impressive,” says Huimin Zhao, a bioengineer at the University of Illinois, Urbana-Champaign. Yang says he hopes that by comparing the new Clostridium strain with the previous one, his team will learn what makes the new strain so much better at producing n-butanol and then use that information to further engineer the microbe. But Zhao notes that few metabolic-engineering tools have been developed to work with Clostridium. So Zhao's group and others are now working to reengineer yeast to make n-butanol instead of ethanol, which it readily produces. If researchers succeed in turning yeast or cyanobacteria into second-generation fuel producers, ethanol's days atop the biofuel heap may be waning.