News this Week

Science  03 Sep 2004:
Vol. 305, Issue 5689, pp. 57
1. EXTRASOLAR PLANETS

Planet Hunting Gets Rocky As Teams Clash Over Small Worlds

1. Robert Irion

Three teams of astronomers have found the first Neptune-size planets orbiting stars beyond our solar system, a milestone for the elite community of extrasolar-planet hunters. But the joyful glow over the new worlds—which may be the first rocky bodies known to circle other ordinary stars like the sun—was dimmed by a preemptive announcement that stunned U.S. observers.

Astronomers with the European Southern Observatory (ESO) trumpeted their unreviewed discovery on 25 August, just 5 days after their last observations. In an odd twist, several of the European scientists also are co- authors of one of the two U.S. papers on similar planets, both refereed and originally scheduled for public release in mid-September. “I was shocked,” says astronomer Barbara McArthur of the University of Texas, Austin, of the decision by her European co-authors. Privately, a colleague was less kind: “It's outrageous, and everyone sees it that way.”

Of about 130 known exoplanets, astronomers think nearly all are vast spheres of gas like Jupiter, which is 318 times as massive as Earth. As a gas giant orbits, its gravity tugs its parent star to and fro. That periodic motion creates wobbles in the starlight, which sensitive telescopes on Earth can detect.

Eager to find smaller, solid bodies that could potentially support water and alien slime, planet hunters have refined their techniques to spot ever-tinier stellar motions. For now, their quarries are planets like Neptune and Uranus, which have 17 times and 14.5 times Earth's mass, respectively. Neptune and Uranus hide major cores of ice and some rock beneath their gaseous mantles. But models show that planets of similar size consisting mostly of rock could coalesce in the warm portions of iron-rich dusty disks.

This summer, a group led by astronomers Paul Butler of the Carnegie Institution of Washington, D.C., and Geoffrey Marcy of the University of California, Berkeley, found a planet with at least 21 Earth masses orbiting the red dwarf star GJ 436. The paper was reviewed and accepted at Astrophysical Journal. NASA, which partially funds the search program, scheduled a press conference on 13 September to tout the results.

Marcy soon learned that McArthur's team had evidence for a body of at least 14.2 Earth masses orbiting the star ρ Cancri. He invited McArthur to join NASA's press conference. As the teams talked to theorists, their excitement grew. “For the first time, it's plausible that these are mostly rocky iron balls, with surfaces enabling liquid water to puddle on them,” Marcy says. “This is putting us on the doorstep of detecting other Earths.”

McArthur originally prepared a submission to Nature but later switched to Astrophysical Journal Letters out of concern that the Nature embargo would delay the reports. Among her co-authors, she included four European astronomers who supplied some data on ρ Cancri's motions. The journal quickly vetted and accepted the paper.

The European team—including veteran planet hunters Michel Mayor and Didier Queloz of the University of Geneva in Switzerland—was seeing tantalizing things as well. The scientists used a new spectrograph on ESO's 3.6-meter telescope at La Silla, Chile, to expose stellar velocities with a striking precision of less than 1 meter per second. In June, colleagues monitoring seismological pulsations of a star called μ Ara realized that the signals oscillated gently on a 9.5-day cycle. Further data in July and August nailed the presence of a planet of at least 14 Earth masses, Mayor says.

The astronomers issued an ESO news release on 25 August—the day Queloz was to deliver a long-scheduled talk at the EuroScience Open Forum 2004 in Stockholm, Sweden (see p. 1387). On the same day, the team submitted a short manuscript to Astronomy & Astrophysics. The Europeans refrained from noting that the McArthur team's discovery—on which Mayor and Queloz are co-authors—came first, because they believed the paper was under embargo at Nature, Mayor says.

“This is a … story of convenience,” retorts Marcy. “They clearly went immediately to the presses with a quick and dirty analysis, and with one purpose in mind: to lead the world to believe that they found the first [Neptune].” The upset Americans moved their NASA briefing to 31 August to salvage some media attention.

Amid the rancor, theorists are excitedly interpreting the discoveries. “This is a very encouraging sign that we will find a lot of lower-mass rocky planets in the next 10 years or so,” says Alan Boss of the Carnegie Institution. But theorist Jack Lissauer of NASA's Ames Research Center in Mountain View, California, cautions that such bodies would require “a huge amount of rock” to coalesce in the young stellar disks. “It's possible that an ice-rock planet like Neptune, with some gas, would migrate close to the star and not evaporate,” he says.

Both Boss and Lissauer note that astronomers must find an exo-Neptune that crosses in front of its star to verify its diameter and thus its density. Planet hunters hope this next race will have a more collegial outcome.

2. DEVELOPMENTAL BIOLOGY

Bonemaking Protein Shapes Beaks of Darwin's Finches

1. Elizabeth Pennisi

Darwin's finches are to evolutionary biology what Newton's apple is to physics. After exploring the Galápagos Islands in 1835, Charles Darwin later became intrigued by the varying shapes and sizes of the closely related birds' beaks. Each beak appeared to be specialized for a task, such as cracking seeds or drinking nectar. Once Darwin formulated his ideas about evolution, he realized that these birds exemplified the principles he was proposing. Today, these songbirds are often cited as a perfect example of how new species arise by exploiting ecological niches.

Now developmental biologists have added a new twist to this classic story. Two research teams have discovered that a protein normally associated with the development of the skull and other bones is one of the molecules that tailors the shapes of beaks. Different shapes arise depending on where and when this signaling molecule, called bone morphogenic protein 4 (BMP4), is turned on during development, says Cheng-Ming Chuong, a evolutionary developmental biologist at the University of Southern California (USC) in Los Angeles.

On page 1465, Chuong's team describes BMP4's role in building beaks in chickens and ducks. And on page 1462, developmental biologist Clifford Tabin of Harvard Medical School in Boston and his colleagues show that the expression of BMP4's gene varies, just as the beaks do, in six species of Darwin's finches. Both groups also demonstrated that they can cause birds to develop misshaped beaks by altering BMP4 levels during development.

The two groups' results provide a window into the molecular basis of diversity, says Dolph Schluter, an evolutionary biologist at the University of British Columbia in Vancouver, Canada. He was particularly taken with Tabin's work. “This paper represents a step in answering [how diversity arises] in the most celebrated example of adaptive evolution, the radiation of the Darwin's finches,” he notes.

An outgrowth of the jaw, a beak forms as six processes extend from jawbones in a coordinated manner. Chuong's USC research associate Ping Wu followed one of the processes, the frontonasal mass, in developing ducks and chicks and discovered that the growth patterns differ in the two species. Moreover, the actively growing areas contained BMP4. To test the protein's role in shaping beaks, the researchers increased the amount of BMP4 by injecting it or its gene into the tissue that helps form them. The excess BMP4 resulted in longer, wider, and deeper beaks, Wu and his colleagues report. When they did the reverse experiment, adding a gene whose protein counteracts BMP4, the beaks ended up smaller than normal.

The work “is an experimental test that the molecule could be manipulated in a way to [recapitulate] beak shape,” says Jeff Podos, a behavioral ecologist at the University of Massachusetts, Amherst. Adds Jill Helms, a developmental biologist at Stanford University, “This work underscores that [morphological] changes do not take much [genetic change].”

Working independently, Tabin and his colleagues actually studied Darwin's famous birds. Aided by Princeton University field biologists Rosemary and Peter Grant—renowned for their studies of these Galápagos birds—Tabin's team collected eggs of six Geospiza species. Three species, the ground finches, had stout bills for cracking seeds; the other three, the cactus finches, had the slender, pointed bills needed for retrieving nectar. As such, these beaks are “a wonderful model for understanding the interaction between environment and evolution on speciation,” says Chuong.

Tabin's postdoctoral fellow Arhat Abzhanov looked at finch embryos at different points in development, documenting when and where the genes for 10 different growth factors were expressed among the six species. BMP4 was the only growth factor to distinguish ground finches from cactus finches. The two groups of birds differed in both the amount of BMP4 and the timing of BMP4 activity. The ground finches, with larger beaks, make more BMP4 protein at an earlier stage, Tabin explains.

Each ground finch species had its own distinct pattern of BMP4 expression. G. magnirostris begins making its BMP4 much earlier than the other ground finches examined, for example. “To see the beaks of the different ground finch species light up with different patterns of BMP4 expression was a thrill,” says Schluter.

Tabin's results, coupled with Chuong's, offer convincing evidence that BMP4 shapes beaks, says Podos. Other genes and molecules will also be involved, cautions evolutionary biologist R. Craig Albertson of the Forsyth Institute in Boston, Massachusetts. Indeed, neither group knows what makes the BMP4 gene more active in birds with bigger bills.

Whatever the underlying molecular cause of beak diversification, Podos hopes that further investigations of BMP4 in other bird species will lead to insights into why some birds, such as the finches, rapidly form new species—with the different lifestyles that are possible because of changes in their shapes—while others living in the same place, for example, warblers, do not.

That's the beauty of this work, Podos says: “It translates genetic variation into something we can sink our teeth into. Maybe we are beginning to understand something about [morphological] plasticity.”

3. VIROLOGY

Avian Flu Finds New Mammal Hosts

1. Martin Enserink,
2. Jocelyn Kaiser

Worries about the avian influenza strain, H5N1, that's circulating in Asia have ratcheted up another notch. A paper published online by Science this week (www.sciencemag.org/cgi/content/abstract/1102287) confirms that the virus can infect cats, and that felines can transmit the virus to other cats as well—and perhaps to humans, according to one of the study's authors, Albert Osterhaus of Erasmus University in Rotterdam, the Netherlands.

Although there's no evidence yet that cats have helped spread the flu anywhere, their vulnerability to H5N1—which comes on the heels of similar findings in pigs—increases concerns that the virus may evolve into a more dangerous strain that could set off an influenza pandemic, says virologist Richard Webby of St. Jude Children's Research Hospital in Memphis, Tennessee.

H5N1 has ravaged poultry farms in nine Asian nations—Malaysia officially joined the list 2 weeks ago—and has claimed the lives of at least 26 people. The virus was first reported in cats in January, when a clouded leopard at a zoo near Bangkok died from an infection. A month later, a sick white tiger at the same zoo tested positive for H5N1. Three domestic cats that died near a Thai farm were also found to harbor the virus. In each case, eating raw, infected poultry was the likely infection route.

To further investigate cats' susceptibility, Thijs Kuiken, a veterinary pathologist in Osterhaus's lab, inoculated H5N1 isolated from a fatal human case into the tracheas of three young domestic cats. All developed flu symptoms, such as fever and labored breathing, and one died after 6 days. (In contrast, cats inoculated with H3N2, a human flu virus, did not become infected.) Necropsy of the sick cats revealed lung tissue damage similar to that caused by H5N1 in humans. Further experiments showed that two cats living in close contact with an infected animal also became sick, as did three others that each ate an H5N1-infected chick.

The study underscores H5N1's ability to infect multiple mammal species, which is unusual for strains that circulate in birds. That prowess may help the virus acquire the genes necessary to become easily transmissible among humans, a prerequisite for triggering a pandemic. “The more hosts it gets into, the more possibility it has to change,” says Webby.

Just 2 weeks ago, director Chen Hualan of China's National Avian Influenza Reference Laboratory in Harbin announced at a meeting in Beijing that H5N1 had also been found to infect pigs as early as last year. The finding was reported in January in a Chinese journal and mentioned in one sentence in a July paper in the Proceedings of the National Academy of Sciences, but it went largely unnoticed among Western flu scientists. Those results are especially worrisome, flu experts say, because pigs are believed to be mixing vessels in which avian and human flu viruses can combine into new strains.

Klaus Stöhr, a virologist at the World Health Organization in Geneva, says there's no indication so far that H5N1 has become established in pig populations. The “strongest evidence,” he says, comes from Hong Kong, which imports 5000 pigs a day, mostly from south China. Each month since 1999, Hong Kong agriculture ministry officials have tested a couple of hundred nasal swabs from pigs. They have found human flu viruses, but “never, ever was H5N1 isolated,” Stöhr says. That's no cause for complacency, however, adds Stöhr, who urges countries where H5N1 has been found to step up surveillance of pigs.

Colleagues also note that there's no reason for the public at large to worry about their pet cats—let alone to dispose of them—but that some precautions would be wise. For example, the practice of feeding dead carcasses to carnivores in zoos and on farms “is clearly a bad idea,” warns Malik Peiris, a flu expert at the University of Hong Kong. And cats with access to poultry should be watched for signs of illness, says Stöhr.

4. PALEONTOLOGY

400-Million-Year-Old Wounds Reveal a Time When Predators Romped

Just as swords inspired the invention of chain mail, the history of life hints at many arms races between predators and prey. But with the remnants of the carnage long turned to stone, it can be difficult to prove that the evolution of bigger teeth, for instance, actually did encourage the evolution of defenses like thicker armor.

On page 1453, two paleontologists establish a key part of the argument in a new way. Forest Gahn of the Smithsonian Institution's National Museum of Natural History in Washington, D.C., and Tomasz Baumiller of the University of Michigan, Ann Arbor, show that stalked filter-feeders called crinoids suffered ever fiercer attacks during a period when fish and other major predators were diversifying. Paleontologist Christopher Maples of the Desert Research Institute in Reno and Las Vegas, Nevada, says the case study is “really cool” and could help explain a subsequent explosion in crinoid diversity.

Most studies of predation intensity have focused either on holes that marine snails, which drill into bivalves and brachiopods or on broken fossil shells that show signs of repair. Regrowth indicates the prey survived an attack and could have passed on genes for a thicker shell or other defense, thus ratcheting up the arms race.

Gahn and Baumiller looked at another set of predators and prey during what's called the Middle Paleozoic Marine Revolution. At that time—about 380 million years ago—sharks and fishes were diversifying wildly. Invertebrates in shallow waters were changing, too; crinoids, for example, were evolving thicker armor and spines.

Like their starfish cousins, crinoids excel at regenerating lost body parts. So when a fish chomps off several of the tentacle-like appendages, crinoids grow new ones. Looking at slabs with beautifully preserved crinoids, primarily from eastern North America, Gahn and Baumiller could spot new arms growing from stumps. By counting the stumps, they calculated the rate of predation.

For approximately 100 million years before the Middle Paleozoic Marine Revolution, the researchers found that fewer than 5% of crinoids sported regenerating arms. By the time the predator revolution was in full swing, however, more than 10% were growing replacement arms. The evidence increasing predation is “straightforward and convincing,” says paleobiologist Geerat Vermeij of the University of California, Davis, who showed that a later burst of predator evolution called the Mesozoic Marine Revolution spurred prey to respond.

Crinoid arm regeneration could be a useful way to look at predation intensity in other time periods as well, says paleontologist Tatsuo Oji of the University of Tokyo, although he and Vermeij caution that comparing regeneration rates between species and environments can be tricky. Baumiller and Gahn are planning to measure predation intensity throughout the fossil record, including Vermeij's Mesozoic revolution, when a group of crinoids called comatulids hit on a particularly effective defense tactic: the ability to flee.

5. SCIENTIFIC PUBLISHING

Zerhouni Plans a Nudge Toward Open Access

1. Jocelyn Kaiser

Hoping to resolve an escalating debate about public access to biomedical research reports, National Institutes of Health (NIH) Director Elias Zerhouni consulted with scientists this week and said that he is leaning toward a delay of 6 months after publication before posting grantees' papers on NIH's free Web archive. This plan won't satisfy everyone, he acknowledged, but it is “reasonable.”

A war of words broke out this summer after Zerhouni responded to a House report urging NIH to come up with a plan to give free access to published papers. In a stern seven-page letter last week, the Association of American Publishers and other groups called NIH's plans a “radical new policy” and an “inappropriate intrusion” on free enterprise; they contend that it could force journals to adopt an “unproven” model in which authors pay publication costs. Lobbying for the plan, 25 Nobel laureates—led by Richard Roberts and including former NIH director Harold Varmus and James Watson—wrote Congress on 26 August expressing “strong support” for posting NIH grantees' papers in PubMedCentral—NIH's free, full-text archive—as soon as they are published. A new coalition of patient and library groups called the Alliance for Taxpayer Access, meanwhile, is backing a 6-month release plan.

On Monday, Zerhouni invited about two dozen grantees and intramural scientists to describe “rank-and-file” views. Some expressed concern about pushing journals toward an author-pays model, saying they feared that young scientists might not be able to pay the charges of journals, which could run to $6000 per paper or more. A major shakeup of journals could also harm the peer-review system, others noted. “One of the losers could easily be the scientists,” said Gary Westbrook of Oregon Health & Science University, editor-in-chief of the Journal of Neuroscience. Participants seemed comfortable, however, with a 6-month delay; many of journals already meet that standard, said Zerhouni, who also planned to meet with patient advocacy groups this week. Meanwhile, a staffer for Representative Ernest Istook (R-OK), who inserted the open-access language in the House report, said he plans to hold a colloquy to clarify that NIH should take all views into account. 6. MEETINGS Europe Clones U.S. Science Festival 1. Martin Enserink STOCKHOLM—Scientists and science groupies gathered here from all quarters last week to mingle and share views at the first pan-European jam session of its kind. In the high-ceilinged classrooms of a beautifully restored 1880 grammar school, they discussed the European baby bust, the commercialization of science, and how to make sense of math for a lay audience. Former President Bill Clinton's science adviser Neal Lane gave an in-depth radio interview about nanotechnology policy, young scientists sat down for one-on-one chats with a career counselor, and a horde of noisy teenagers scoured exhibition stands for free goodies. It all took place under the umbrella of the EuroScience Open Forum (ESOF), a new general meeting that drew 1800 people—among them more than 300 reporters—from dozens of countries to the Swedish capital, many more than the organization had hoped for. The 4-day event is the brainchild of Carl Johan Sundberg, a physiologist at the Karolinska Institute in Stockholm with a longtime interest in sharing science with the public. He first proposed the idea in 1999 and served as chair of the steering committee. It's no secret, Sundberg says, that the smorgasbord program was not a Swedish invention but a faithful copy of the format of the annual meeting of AAAS, Science's publisher. Like that meeting, ESOF had multiple goals, from scientific debate to discussing the role of pure science in society and piquing the public's interest in research. Although ESOF's model may be American, participants stressed that the theme of the gathering was distinctly European, and its multinational audience evidence that a science system long fractured along national lines is beginning to coalesce. Many sessions addressed Europe-wide issues, such as the new European Centre for Disease Prevention and Control, slated to open next May in Stockholm; obstacles to career mobility; and the movement to establish a European Research Council for basic research. Indeed, the backdrop of European integration gave the meeting “tremendous symbolism,” says Frank Gannon, an Irish biologist who directs the European Molecular Biology Organization in Heidelberg, Germany. ESOF also included a few innovations to the AAAS model, such as a daily wrap-up of events during spirited (at times hilarious) cocktail-hour debates led by BBC reporter Quentin Cooper. To get the public involved in events scattered throughout downtown Stockholm, some surprises were deployed. The most eye-catching was a German contraption, the “Amazing Profmobil,” a bicycle with a small podium and a computer screen mounted on the back that scientists could wheel into parks and squares to explain their work to the public. (The public appeared mostly dumbfounded.) Despite the festive atmosphere, some journalists grumbled about the meeting's heavy slant toward policy issues and a dearth of breaking science news. Apart from the announcement of the detection of the smallest known exoplanet (see p. 1382), few research results were presented. “You don't go home with a lot of news stories,” says Bruno van Wayenburg, a freelance reporter from the Netherlands. Reporter Angela Grosse of the Hamburger Abendblatt says that didn't bother her, because she came—like some other media representatives—primarily to find contacts and inspiration for future stories. Sundberg counters that it's hard to persuade researchers to announce their findings at a general meeting like ESOF or the AAAS annual meeting; they prefer to inform their colleagues first. But he says the organizers will try harder next time. Unlike the AAAS meeting, ESOF will be a biennial event; Munich will play host in 2006, and Barcelona has indicated its desire to be next after that. As other cities learn of ESOF's potential to boost their image as a science hub, Sundberg predicts, there may well be an Olympic-style bidding war for the 2008 edition. 7. PRESIDENTIAL APPOINTMENTS NSF's Acting Chief Facing Legal Limit on Tenure 1. Jeffrey Mervis Time is running out for Arden Bement, the acting director of the U.S. National Science Foundation (NSF). Unless the White House acts promptly—which it promises to do—Bement could be sent packing later this month because of an obscure law designed to encourage timely presidential appointments. Bement was already serving as the presidentially chosen director of the National Institute of Standards and Technology (NIST) when he was tapped earlier this year as a temporary successor to Rita Colwell, who left NSF before the end of her 6-year term (Science, 20 February, p. 1116). The 72-year-old materials engineer took office on 21 February, and that's when the clock started ticking. Under the 1998 Federal Vacancies Reform Act, a presidentially appointed stand-in cannot serve for more than 210 days. For Bement, time runs out on 18 September. Acting officials can't be reappointed or have their terms extended, according to the law, and any official duties performed after the deadline are null and void. There is one relevant exception. If the president formally nominates someone, the clock is suspended until the Senate acts on the nomination. A rejection or withdrawal of the nominee restarts the 210-day clock. Bement said in February that he expected to return to NIST quickly, and presidential science adviser John Marburger said in April that a nomination was imminent. Although no name has surfaced, last week Office of Science and Technology Policy spokesperson Robert Hopkins said that “the Administration intends to nominate a permanent NSF director prior to the end of Bement's temporary appointment.” That silence is making the scientific community increasingly anxious. “We are very concerned,” says Warren Washington, chair of the National Science Board, which oversees NSF. He says that Bement “has done an excellent job. Arden is due to leave on the 19th, and it's not clear what will happen after that. You'd think [the White House] would be able to find someone during that [210-day] time.” Federal agencies are occasionally run by acting officers, of course. But the 1998 law is intended to prevent a president from sidestepping the U.S. Constitution with acting officials who don't have to be approved by the Senate. So far, however, the little-known law is struggling to gain the respect of the Executive Branch. A 2001 study by the Government Accountability Office (GAO), which is responsible for enforcing the law, found that agencies hadn't even reported a quarter of their acting officials. Once GAO detects a violation, its authority is limited to notifying both the agency and Congress that the law has been broken. GAO's database, for example, shows that Ruth Kirschstein twice exceeded her 210-day authority as acting National Institutes of Health (NIH) director after succeeding Harold Varmus in January 2000. In the first instance, NIH's parent agency, the Department of Health and Human Services, changed Kirschstein's title but said she could continue to act as NIH's boss. The second time, after a new 210-day stint triggered by a change in administration also ran out, Congress added language to an NIH spending bill that gave Kirschstein the right to remain acting director until her successor was in place. Her interim reign finally ended in July 2002, when the Senate confirmed her successor, Elias Zerhouni. A senior congressional aide says there are no plans to address the situation at NSF when Congress returns next week from its summer recess, and NSF General Counsel Lawrence Rudolph speculated that it would be difficult for legislators to act by the 18th. In the meanwhile, Bement continues to shuttle between NIST and NSF, doing both jobs and waiting for his political bosses to clarify his status. 8. ACADEMIC LEADERS Neuroscientist Named MIT President 1. Andrew Lawler A neurobiologist from Yale University has been named president of the Massachusetts Institute of Technology (MIT). The appointment of Susan Hockfield to succeed Charles Vest in December reflects the growing importance of the life sciences at MIT, which for the first time in its 142-year history will be led by a woman. “I think they are slightly redefining MIT” by choosing Hockfield, says James Watson, a Nobel laureate who hired her as a junior investigator at New York's Cold Spring Harbor Laboratory in 1980. “They haven't chosen someone from the military-academic-industrial complex.” Her selection, he adds, “is great for neuroscience at MIT.” This year, for example, MIT for the first time will receive more research dollars from the National Institutes of Health than from the Pentagon. Hockfield is currently provost at Yale, which she joined as a faculty member in 1985. She has also served as dean of the graduate school of arts and sciences. She possesses “a rare combination of scientific achievement, outstanding managerial talent, and an extremely engaging personal style,” says James Champy, who chaired the presidential search committee. All of MIT's previous 15 presidents have been male engineers or physicists, and the institution's prominence has made them national spokespersons for the science and engineering communities. Vest, a mechanical engineer, certainly played that role during his 14 years at the helm. Although Hockfield lacks that experience, her boss, Yale president Richard Levin, predicts that she “will take a leading role in shaping national science policy.” Hockfield's research has focused on brain tumors, and her work using monoclonal antibody technology led to the discovery of a protein that regulates changes in neuron structure. She also found a gene and proteins that may help researchers battle the spread of particularly deadly brain cancers. Yale colleagues cite her efforts to increase the number of women faculty members, a contentious issue at MIT since a 1999 report that was harshly critical of its treatment of women. 9. NEUROBIOLOGY Making Sense of Tourette's 1. Steve Olson* 1. Steve Olson's most recent book is Count Down: Six Kids Vie for Glory at the World's Toughest Math Competition. The causes of this syndrome have long been controversial. Now research is unearthing both genetic and environmental triggers and pointing the way to better treatments When Purdue University neurobiologist Peter Hollenbeck lectures in front of his 400-student cell biology class, the symptoms of his Tourette syndrome—the up-and-down movements of one arm, the twists of his head, the barely audible sounds—virtually disappear. But, by the time the lecture is finished, the urge to move is unbearable. He quickly retreats to his office to “tic, tic, tic,” he says, “until the need subsides.” Hollenbeck has a mild case of Tourette syndrome, whose effects he chooses to endure rather than experience the slight sedation he feels when medicated. Other people are more harshly affected. A small minority exhibits complex behaviors such as imitating others or blurting out profanities. Some are tormented by obsessive thoughts, such as the scientist who had to give up high-energy physics because every time he saw a “Danger—High Voltage” sign, he felt compelled to touch the equipment. Many cases of Tourette's are socially inconspicuous, and people with the syndrome deride the stereotyped depictions that occasionally appear in the media. But severe cases can still provoke, as James Boswell said of Samuel Johnson's Tourette's, “surprise and ridicule.” The cause of Tourette syndrome has been controversial ever since Georges Gilles de la Tourette, a neurologist who shared a mentor with Sigmund Freud at the Salpêtrière Hospital in Paris, first described the condition in 1885. Is the syndrome the result of hysteria (Tourette's hypothesis), repressed sexual conflicts, or oppressive mothers, which were the favored explanations for much of the 20th century? Or is it an organic defect of the brain, as many neuroscientists and physicians now hold? The ability of neuroleptic drugs, beginning with haloperidol in the 1960s, to reduce tics supported the neurologic position. But why then are people with severe cases sometimes drawn toward socially proscribed behaviors? New findings are beginning to resolve old controversies. Researchers are identifying parts of the brain affected by the syndrome. They are teasing out the genetic and environmental factors that help produce it. New behavioral and pharmacological treatments are improving the quality of life for Tourette's sufferers. Although many features of the syndrome remain baffling, researchers say that the intensified research of recent years has begun to pay off. Defining the phenotype The wide range of Tourette's symptoms makes it tough to figure out how many people have the syndrome. Many children exhibit tics such as blinking or shrugging. When researchers observed first- through sixth-grade classrooms in Montgomery County, Maryland, in 1999–2000, they saw single or occasional tics in 18% of children and persistent tics in 6%. But just a fraction of these children would be diagnosed as having Tourette syndrome. Current diagnostic criteria require the presence of multiple motor tics and one or more vocal tics that persist for more than 1 year. Typically, the tics wax and wane over the course of weeks and months, with old tics disappearing and new ones taking their place. Children often show the initial signs of tics at ages 6 or 7, and in many cases the tics diminish significantly in the mid- to late teen years. “When I'm asked how many people have it,” says John Walkup, a child and adolescent psychiatrist at Johns Hopkins University (JHU) School of Medicine in Baltimore, “my response is, ‘Have what: mild tics or a severe case?’” According to Lawrence Scahill, who studies neuropsychiatric disorders at the Yale Child Study Center, a plausible lower bound for the syndrome is 1 in 1000 people and a plausible upper bound is 1 in 100. But because many people who would meet the diagnostic criteria for Tourette syndrome never seek treatment, better estimates are elusive. Comorbid conditions complicate many diagnoses. As many as half of the patients who come to clinics with the symptoms of Tourette syndrome also have other disorders. Obsessive-compulsive disorder (OCD) and attention deficit-hyperactivity disorder (ADHD) are the most common, but Tourette's patients also have elevated rates of depression, anxiety disorders, and social and emotional difficulties. A clinician might have to decide, for example, whether repeatedly lining up a finger with a corner of a room constitutes a tic or a compulsion. Some researchers see Tourette syndrome as a single discrete disorder that may be accompanied by other syndromes such as OCD or ADHD. Others see Tourette's as part of a spectrum of disorders with common causes and varying manifestations. The distinction is critical when designing studies of Tourette's, says Mary Robertson, a neuropsychiatrist at Royal Free and University College London Medical School. If patients with Tourette's symptoms alone have a different disorder from that of patients with Tourette's and OCD, researchers need to distinguish between the two groups to search for causes. “Unless you define what the phenotype is, studies of Tourette syndrome are nonsense,” Robertson says. Investigators who image the brain have made some progress in detecting patterns of neural activity that might help in making diagnoses. For example, imaging studies show that when ticcing or suppressing tics, people with Tourette syndrome differ from controls in localized brain activity. But the patterns of activity vary from person to person, so observing and describing tics remains the best way to arrive at a diagnosis. From phenotypes to causes Brain imaging has also helped focus attention on the parts of the brain that seem to give rise to the symptoms of Tourette syndrome: the basal ganglia. These are a set of interconnected brain structures positioned beneath the cerebral cortex. Neural circuits run from the cerebrum through the basal ganglia and then back to the cerebral cortex, providing a feedback loop that helps integrate brain functioning. In some ways, the basal ganglia act as an operating system, linking volitional acts initiated in the cerebrum with the nerves and muscles that carry out our wishes. In Tourette syndrome, that operating system appears to be somewhat buggy, says Jonathan Mink, a neuroscientist at the University of Rochester Medical Center in New York. One function of the basal ganglia is to learn and regulate the expression of discrete chunks of behavior, such as particular movements or thoughts. In this way, says Mink, the basal ganglia help the other parts of the brain perform, combine, and suppress behaviors. “A lot of learning involves enabling the behaviors you want and inhibiting the ones you don't,” he says. Mink suspects that, in Tourette syndrome, groups of neurons in the basal ganglia fail to inhibit particular movements or other unwanted behaviors. As a result, these behaviors surface as tics. Furthermore, circuits from all parts of the cerebral cortex—including those involved in motion, sensation, and emotion—pass through the basal ganglia. Disinhibiting specific parts of the basal ganglia may trigger different manifestations of Tourette's and related disorders. Also, although circuits largely run in parallel through the basal ganglia, some neurons spread across circuits, allowing for crosstalk. This might explain, for example, why tics get stronger when someone is stressed or tired. Researchers don't know why parts of the basal ganglia may be malfunctioning. But the neurotransmitter dopamine appears to be involved, because many of the drugs that are effective against Tourette syndrome block dopamine receptors. Researchers have looked at dopamine release, dopamine reception, and secondary pathways within postsynaptic neurons, but no obvious culprit has emerged. However, a recent imaging study has revealed an elevated number of dopamine-containing neurons in one part of the basal ganglia of Tourette's patients, and another has shown that abnormal brain function during a memory test can be restored to normal by manipulating dopamine. Genetic origins? Several lines of evidence point toward a genetic cause of Tourette syndrome. The disorder tends to run in families and is several times more common in boys than girls. In some families, parents pass the syndrome on to their children as if it were a dominant trait. Even when Tourette's arises anew in a generation, relatives are often more likely to suffer from associated conditions such as OCD or ADHD. Because of the seemingly simple transmission of the disorder in some families, researchers in the 1990s expected to find a single, relatively rare genetic variant, as in Huntington's disease, that caused at least some cases. But that model proved to be too simple, says David Pauls, a geneticist at the Harvard School of Public Health and Massachusetts General Hospital in Boston. Instead, genetic studies suggested that several chromosomal regions were involved, with the genes in these regions having contrasting effects. According to Matthew State, a geneticist at the Yale Child Study Center and the Center for Genomics and Proteomics, “Studies have pointed to genes with dominant, recessive, and intermediate inheritance, which makes our lives very difficult.” Researchers are eagerly awaiting the fall release of results from an ongoing genetic study of 256 families being conducted by an international consortium. Meanwhile, other studies that can be done with far fewer research subjects are sharpening the focus on suspicious chromosomal regions and identifying new ones. Many geneticists now suspect that Tourette syndrome results from several genetic variants acting in concert. They also believe that, if enough research subjects can be recruited, future genetic studies will uncover the specific variants responsible for the absence or presence of comorbidities with Tourette's. Environmental complications But genes are only part of the story: As with other complex diseases, environmental factors influence the syndrome. Although identical twins tend to share Tourette syndrome, in about 20% of cases one has the syndrome and the other does not. And even when both have Tourette's, their experiences with the syndrome can differ markedly, with the lighter-weight twin at birth often having more severe symptoms. Possible environmental factors range from complications during pregnancy, to stressful early-life experiences, to random events during development. But suspicion has focused on an infectious agent. Since the 18th century, physicians have known that rheumatic fever can lead to movement disorders in a subset of those afflicted. This observation led researchers to wonder whether streptococcal infections—the cause of rheumatic fever—might be behind some cases of Tourette syndrome. Some children first show signs of Tourette's after a strep infection, and subsequent infections often seem to exacerbate their tics. In addition, immunologic studies have suggested that in some children the antibodies generated to combat strep misidentify and damage neurons in the basal ganglia. “Parallel lines of research were coming together and showing the same thing: that strep is a factor,” says Susan Swedo of the National Institute of Mental Health, who categorizes such cases of Tourette's and related conditions as pediatric autoimmune neuropsychiatric disorders associated with Streptococcus (PANDAS). Swedo and her colleagues have conducted double-blind trials of penicillin and azithromycin prophylaxis to prevent exacerbations of tics in children with Tourette syndrome. They also have experimented with the more invasive process of using plasmaphoresis to remove anti-basal ganglia antibodies from the blood. Although the waxing and waning of the syndrome complicates the interpretation of results, Swedo is convinced that both approaches can significantly reduce the impairment caused by Tourette's and related disorders. Many researchers are skeptical of the association and of pharmacological efforts to prevent strep infections in children with Tourette syndrome. “It's an intellectually compelling hypothesis that deserves further study, but the data are not all there,” says Harvey Singer, a pediatric neurologist at JHU. Singer points out that most children contract multiple strep infections, so an association with tic exacerbations could be coincidental. Many researchers and physicians also worry about prescribing long-term use of antibiotics for children with neuropsychiatric disorders, because such widespread use would likely increase levels of drug resistance. An ongoing large-scale study of penicillin prophylaxis may provide some answers, but the strep connection is likely to remain controversial. Treating the symptoms For now, the most common treatment for Tourette syndrome remains what it has been for the past 4 decades: using drugs to alter the activity of dopamine and related neurotransmitters in the basal ganglia. Newer kinds of drugs, known as atypical neuroleptics, are thought to produce fewer unwanted side effects than did earlier treatments. Many physicians practice the “art of medicine,” prescribing different drugs until they find one that works for a patient. Earlier this year, a man suffering from a severe case of Tourette syndrome underwent an experimental procedure in which battery-powered electrodes were placed in his thalamus, which forms part of the circuit connecting the basal ganglia and the cerebral cortex. The electrical stimulation from the electrodes produced an almost complete cessation of his tics. Although the success has generated great excitement among patients, many researchers and physicians are cautious. “This is an experimental procedure that has significant risks,” says JHU's Walkup. “We may not like all of the medications all of the time, but many patients find a way to get control of their tics with them.” Other nonpharmaceutical interventions hold greater promise. Buoyed by the success of behavioral modification therapy in treating OCD, researchers have been examining similar approaches to Tourette syndrome. One problem with Tourette's, says John Piacentini, a specialist on childhood and teen neuropsychiatric disorders at the University of California, Los Angeles, is that it sets up a positive feedback loop. Patients feel the need to tic and then experience relief when they do, thus reinforcing the neural circuits involved in that behavior. To break the loop, Piacentini and his colleagues have been experimenting with behavioral techniques. People with Tourette syndrome are helped to be made aware of their tics—for example, by watching themselves in a mirror. They then are taught to replace the tic with a competing response. They might replace the tic with a movement that is less apparent, tense the muscle involved in the tic, or strengthen an antagonistic muscle. Such an approach “tries to disrupt the automatic chain of events underlying the expression of a tic,” says Piacentini. In a study conducted with his own patients, Piacentini has seen habit-reversal training produce a 30% reduction in tic severity. Now he is participating in a multicenter study to investigate the therapy more thoroughly. Unifying mind and brain The renewed emphasis on behavioral approaches is producing a broader view of Tourette syndrome. According to Neal Swerdlow, a psychiatrist at the University of California, San Diego, Tourette's reveals the artificiality of viewing a neuropsychiatric disorder as either purely psychological or purely neurological: “If you go to a meeting, single-cell neurophysiologists and people studying theories of the mind both have something to contribute to the discussion.” This unified view of Tourette syndrome has important implications in both the clinic and the lab, say physicians and researchers. The goal of treatment is not necessarily to eliminate tics, say clinicians; it is to enable someone with Tourette's to function effectively in society. The Tourette Syndrome Association Inc. (http://www.tsa-usa.org/), an advocacy group founded in 1972 by some of the first patients to benefit from pharmacologic treatments, has worked hard to educate the public and the media about the syndrome. Especially for cases of Tourette's unaccompanied by severe comorbidities, understanding and accommodation can be as important as medications. Similarly for the research community, an emphasis on the experiences and adaptations of individuals can suggest areas to explore that a narrow biomedical focus might overlook. For example, determining which patients could benefit most from behavioral approaches could provide physicians and their patients with badly needed guidance. Tourette syndrome has biological, psychological, and social dimensions, says Swerdlow, “and you can't separate out one of those without losing the disorder.” 10. HIGH-ENERGY ASTROPHYSICS Telescopes Break New Ground in Quest for Cosmic Rays 1. Daniel Clery To trace the origins of mysterious particles from space, researchers are building instruments that reap novel benefits from being planted on terra firma In 1912, Austrian physicist Victor Hess set out to find the source of a mysterious radiation that was plaguing electrical experiments of the day. Most scientists thought it came from radioactive minerals in the ground. But in a series of daring balloon flights that reached heights of several kilometers, Hess showed that the radiation increased with altitude and did not wane even during the night or a near-total eclipse of the sun. He concluded, controversially, that the radiation came from deep space. The discovery of “cosmic rays” later netted Hess the Nobel Prize in physics. Yet, nearly a century after Hess's experiments, astrophysicists still do not know where in space they come from. That may be about to change, thanks to powerful new telescopes designed to detect light with the very highest energies: gamma ray photons with energies in the range of 1012 electron volts, or tera-electron volts (TeV). Unlike ordinary astronomical telescopes, which try to peer through Earth's distorting blanket of air to view objects beyond, the new instruments—known as imaging air Cerenkov telescopes—use an indirect method: They look for flashes of visible light created high in the atmosphere when the gamma rays hit. Theorists believe that many of these gamma rays share a common origin with cosmic rays and that they should be easier to trace back to their sources. First-generation Cerenkov telescopes have been scanning the skies for 2 decades. But although they have turned up several promising sources of TeV gamma rays, they cannot yet prove that cosmic rays come from the same place. Researchers expect that the new, more powerful generation of these telescopes, which came on line this year, will cement the connection. At the vanguard is a four-scope array based in Namibia and named the High Energy Spectroscopic System (HESS), in honor of the cosmic ray pioneer. HESS began observing last January and will be officially inaugurated on 28 September. A second array in Australia started up in March; a single scope in the Canary Islands will join the hunt this autumn; and a U.S.-based array is scheduled for completion in 2006. TeV gamma ray astronomy has always been an oddball in the astronomy world, says Karl Mannheim of the University of Würzburg, Germany: “We use particle physics techniques. The whole culture is different.” But thanks to some recent successes with both the old and new Cerenkov telescopes, astronomers are now beginning to “take us seriously,” says HESS spokesperson Werner Hofmann of the Max Planck Institute for Nuclear Physics in Heidelberg. That's particularly true because, even though the original motivation for studying TeV gamma rays was to track down the source of cosmic rays, this part of the spectrum shows promise for studying traditional astronomical objects, such as pulsars, blazars, and active galactic nuclei, and perhaps even enigmatic gamma ray bursts and dark matter. Cosmic rays are small atomic nuclei—mostly hydrogen nuclei, or protons—that whiz through space at close to the speed of light. No ordinary star could boost matter to such unimaginably high speeds; some other high-energy process in deep space must be at work. Researchers suspect supernovas but don't yet have conclusive evidence. The problem is that cosmic rays themselves don't tell you where they've come from. Because the particles carry electric charge, interstellar magnetic fields scramble their trajectories, making it impossible to identify their source. But if theorists are right that the cosmic rays get their initial kick from supernova remnants, then this boost has a byproduct: TeV gamma rays, which, being chargeless, zip through space as straight as an arrow. Find where those gamma rays come from, the theory goes, and you might just find a source of cosmic rays. Gamma rays don't give up their secrets easily, however, because they cannot penetrate Earth's atmosphere. Astronomers first got a good look at them with the help of orbiting detectors, culminating, between 1991 and 2000, in NASA's enormous Compton Gamma Ray Observatory. But CGRO was not sensitive to TeV photons. To study them, astrophysicists hit on a counterintuitive trick: making the atmosphere part of the detector. When a gamma ray or a cosmic ray hits the upper atmosphere, it shatters an atom. The fast-moving debris shatters other atoms, and debris from them shatters more. Soon a shower of millions of particles rains down toward Earth's surface. Initially, these particles are traveling faster than the speed of light in air, so to slow down they shed photons of blue light known as Cerenkov radiation. Researchers first detected the Cerenkov light from cosmic rays in the 1950s, but it was not until the 1980s that they figured out how to distinguish the more informative gamma ray air showers from cosmic ray air showers: The two types of showers have slightly different shapes. The Whipple telescope, a 10-meter-wide optical dish on Arizona's Kitt Peak, was the first instrument to capture the Cerenkov light from an air shower and form it into an image. Such Cerenkov telescopes do not need to be made to the optical perfection of normal astronomical telescopes because they are observing something only 10 kilometers away in the upper atmosphere. But the light from air showers is very faint—just 100 photons per square meter reach the ground—so the telescopes preferably need to be somewhere high, dry, and very dark. The telescope dish focuses this faint signal onto an array of photomultiplier tubes—which can detect single photons—that forms a rough image of the shower. The image is key. The shape not only distinguishes gamma rays from cosmic rays but also helps researchers calculate the direction the gamma ray came from. And the intensity of the image—the number of photons—tells them its energy. In 1989, the Whipple telescope for the first time traced TeV gamma rays back to a recognizable source: the Crab nebula, the remnant of a supernova thought to have exploded in 1054. The next breakthrough came in the mid-1990s from a European collaborative experiment called HEGRA, for High-Energy Gamma Ray Astronomy, based on the island of La Palma in the Canary Islands. HEGRA had a variety of different detectors for TeV gamma rays, but the most successful, says Mannheim, was an array of five imaging Cerenkov telescopes arranged in a square 100 meters across with one scope in the middle. The benefit of having an array of telescopes is that the different views of the air shower can produce a three-dimensional image, giving better discrimination between gamma rays and cosmic rays and a better fix on the direction of the original gamma ray (see figure). “The stereoimaging technique is incredibly powerful,” says Rene Ong of the University of California, Los Angeles. The success of the HEGRA telescopes spawned proposals for several more arrays, with bigger dishes and better electronics. Part of the HEGRA collaboration joined with others and began building HESS in Gamsberg, Namibia. The Whipple team embarked on VERITAS (the Very Energetic Radiation Imaging Telescope Array System), initially to have four scopes, on Kitt Peak. And a Japanese- Australian team that built a first-generation Cerenkov instrument in Woomera, Australia, set about building four new ones, dubbed CANGAROO III, short for Collaboration of Australia and Nippon for a Gamma Ray Observatory in the Outback. Other HEGRA members formed a new team, including Mannheim, to try a different route: building a single, much larger telescope, the 17-meter-wide MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov [sic] telescope) on La Palma, which can detect lower-energy gamma rays from the ground. HESS began routine operations last January, and CANGAROO III followed suit in March. Both teams announced some of their first results at a meeting on high-energy gamma ray astronomy in Heidelberg in July (Science, 6 August, p. 763). VERITAS, which took longer to secure funding, has one prototype scope working and should be up and running in 2006. “We've demonstrated the technology works. Now we just have to replicate it,” says VERITAS's spokesperson, Trevor Weekes of the Whipple Observatory. MAGIC hopes to begin routine observing this October. Researchers are bracing themselves for a flood of new data. “In the past, the main problem was that you were only looking at 18 or 19 [TeV gamma ray] sources,” says Hofmann. The new scopes, with their superior ability to pick out gamma rays from the background, should rapidly expand that catalog to 100 or more TeV sources, including both supernova remnants and other more exotic objects in distant galaxies, Hoffman says. That will be “the beginning of ‘real’ astronomy,” says CANGAROO III spokesperson Masaki Mori of the University of Tokyo. Their first big project, researchers say, is to nail down whether supernovas do produce cosmic rays. When material speeding out from the supernova hits interstellar gas, it creates a shock wave, and particles, usually protons, “ride the shock like a surfer on a wave,” says Hofmann. Most of these light-speed surfers glide off into space as cosmic rays, but a few slam into atoms of interstellar gas and are annihilated, each creating a neutral pion that quickly decays into two TeV gamma rays. But that is not the only process that can produce TeV gamma rays. Accelerated electrons colliding with low-energy photons can also produce them. To discover whether at least some of the gamma rays are produced by protons rather than electrons, researchers will have to try to map out where the gamma rays originate around the supernova remnant, because the two processes would have different distributions. Resolving the cosmic ray mystery “won't happen overnight,” says Weekes. “No single observation will solve it.” And researchers caution that the result is not a foregone conclusion. “If supernovae are not confirmed as the source [of cosmic rays],” says Hofmann, “we'll really have to rethink our models.” Even if that revolution never comes, Cerenkov telescopes are already unleashing surprises. When the first instruments were built, researchers were focused on the cosmic ray problem. “I wouldn't have been surprised if we'd just seen supernova remnants,” says Weekes. But a large chunk of the sources they found were in fact far more distant objects in other galaxies. When researchers managed to identify these extragalactic sources by looking for them at other wavelengths, they were staggered by the sheer variety. The menagerie includes active galactic nuclei, which are believed to have huge accreting black holes at their centers. These black holes often send out jets of particles at relativistic speeds that can produce gamma rays. There are also tight-knit groups of very massive and hot stars, known as OB stars, that produce such an outflow of stellar wind that they create a shock wave when they hit the interstellar medium. Perhaps the “most fascinating,” says Mannheim, is the possibility of identifying dark matter. We know from the way galaxies behave that there must be more matter in them than we can see in the shining stars and glowing dust. Theorists believe that some dark-matter particles cluster around the centers of galaxies or in their haloes. If dark- matter particles and antiparticles are annihilating each other, they will produce TeV gamma rays visible to Cerenkov telescopes. At the Heidelberg meeting, the HESS team reported seeing gamma rays from the center of our galaxy. Hofmann says the energy was wrong for dark matter but adds that they “cannot exclude” that explanation. Pioneers at this high-energy frontier don't yet know what they will learn from these exotic objects by studying their TeV gamma rays, but they're looking forward to finding out. “We have to be prepared to find something new,” says Mannheim. Adds Ong: “The HESS results are just the beginning” 11. 7TH INTERNATIONAL CONGRESS ON VERTEBRATE MORPHOLOGY MEETING Newly Hatched Dinosaur Babies Hit the Ground Running 1. Elizabeth Pennisi BOCA RATON, FLORIDA— From 27 July to 1 August, animals with a backbone drew the attention of morphologists, evolutionary biologists, and other researchers. Therizinosauroid dinosaurs grew up fast. When they chipped their way out of an egg, the animals emerged strong-legged, ready to fend for themselves and find food, according to an analysis of 80-million-year-old fossil dinosaur eggs conducted by a team of paleontologists and developmental biologists. For the past 6 years, Arthur Cruickshank of the University of Leicester, U.K., Martin Kundrát of Charles University in Prague, Czech Republic, and their colleagues have studied the jumbles of bones and teeth packed into a dozen fossil eggs found in Henan Province, in east-central China. The teeth and bones allowed them to identify the fossils as theizinosauroid, Kundrát reported. Now, by comparing the dinosaur embryos with embryos of birds and alligators, Kundrát has determined how far along in development each embryo was and has begun to piece together how therizinosauroid young grew to be independent. To do this, Kundrát's team enlisted the help of Terry Manning of Rock Art in Leicester, who spent several years removing the eggshells, etching out the rock inside, and exposing the fossils. The results of Manning's efforts are impressive and provide unprecedented details about dinosaur embryos, says Eric Snively, a paleontologist at the University of Calgary, Canada. Manning and Cruickshank first documented the amount of yolk in each egg and the position of each dinosaur embryo. Because the amount of yolk packed around an embryo decreases over time, the degree to which the embryo is squished inside the eggshell is a rough indicator of the embryo's age. Kundrát got an even better sense of each embryo's developmental age by using the porosity of the fossilized dinosaur skulls, limb bones, and backbones as a guide. A skeleton starts out soft and porous and gradually hardens into bone, so the degree of ossification typically reflects the age of an embryo. Using the known morphology and hardness of alligator bones at different points in embryogenesis, Kundrát was able to sharpen his age estimate for each dinosaur embryo. Kundrát determined that all the dinosaur embryos were at least two-thirds of the way through their development, and parts of their skeletons were much further along than those of comparably aged alligator embryos. For example, the dinosaur vertebrae were less porous than expected. “They had well-ossified limb bones, so they can walk immediately after hatching,” says Kundrát. As part of their study, Kundrát and his colleagues also gathered the fossilized teeth of the embryos. Those from the youngest embryos resemble the teeth of the other theropods and were well suited for eating meat. In the more mature embryos, although the teeth retained some meat-eating potential, they were more like those seen in adult therizinosauroids, which are presumed to be herbivores. “We could see the transition of the tooth crown and cusp,” Kundrát said. These data suggest that the hatchlings came out of the egg able to chase down prey and consume suitable plants, Kundrát reported. He suggests that these stages of tooth development reflect the evolutionary steps that allowed therizinosauroids to arise from carnivorous ancestors. “I'm glad to see this [embryo work] done,” says Zhe-Xi Luo, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. In addition to their embryos, he notes, the eggs are important in their own right, because they hint at another aspect of the dinosaurs' lives. Until recently, the only adult remains of therizinosauroids in the Far East have been found near Mongolia, about 1,000 kilometers from the site where the eggs were found. This suggests to Luo that these dinosaurs migrated great distances or that they were much more widespread than paleontologists had thought. 12. 7TH INTERNATIONAL CONGRESS ON VERTEBRATE MORPHOLOGY MEETING Tiny Salamanders Show Their Teeth 1. Elizabeth Pennisi BOCA RATON, FLORIDA— From 27 July to 1 August, animals with a backbone drew the attention of morphologists, evolutionary biologists, and other researchers. For such small animals, salamanders belonging to the Thorius genus have posed a big problem: Biodiversity experts can't easily tell different species apart, because many of them look identical. That makes it difficult to count species or understand the animals' evolutionary history. Now, James Hanken of Harvard University has used genetics to classify the animals and place them on a family tree that illuminates the morphological history of the genus. As Hanken reported at the meeting, the tree suggests that a few Thorius species have turned back the evolutionary clock, reacquiring traits—including teeth—that their earliest ancestors had lost. The miniature salamanders, which are native to Mexico, live on moss and inside bromeliads and fallen logs. Hanken, who began studying the animals 30 years ago, has always been fascinated by their size. Although some are much larger, certain Thorius species have bodies just 13 mm long, making them the tiniest tailed tetrapods. Packing all the necessary organs into a body that size poses a challenge. “[They] are right up against the edge of vertebrate design,” says Hanken. They can't be much smaller, agrees Johan van Leeuwen of Wageningen University in the Netherlands. Hanken originally thought there were fewer than a dozen Thorius species, but by looking for slight genetic differences that readily distinguish one species from another, he and his colleagues quickly identified 14 new species. His group recently added eight more to the list. “Every trip we take, we find one or two new species,” says Hanken. Those results answered one long- standing question: In part because there's little room in those tiny bodies to move parts around, researchers have wondered whether the small size of Thorius salamanders would limit the animals to splitting into just a few species instead of radiating into many. “Hanken's results show that … these salamanders have been radiating just fine,” says Jukka Jernvall, an evolutionary biologist at the University of Helsinki, Finland. That radiation took some surprising turns, however. The skull bones of the tiniest Thorius species are mere slivers compared to those of other salamanders, and they no longer interlock to make a solid skull. Their 3-mm-long heads have just enough room for a brain, eyes, nose, and ears—the majority of muscles and connective tissue is missing or greatly reduced. In most species, the upper teeth are even gone. Yet four of the salamander species have their upper teeth. Hanken had assumed that these species all descended from a common ancestor that had kept those teeth while other branches of the Thorius tree lost them. Yet the family tree he and his colleagues constructed revealed that the four species are not closely enough related to have shared such an ancestor. Instead, each species with upper teeth came from toothless stock. These upper teeth “have been reacquired four times,” Hanken reported at the meeting. Three of the upper-toothed species break the miniaturization trend among Thorius salamanders. They're larger and have bigger skulls than other extant species. “The presence of teeth seems to be fluid over time and suggests miniaturization and loss of elements might not always be final,” says Jernvall. Some of Hanken's colleagues question his interpretation, noting that the common wisdom holds that once a trait disappears from a group of organisms, it rarely resurfaces. Hanken's conclusion is “something that's hard to defend,” says Ann Huysseune of Ghent University in Belgium. But Hanken argues that these small vertebrates must have had a lot of evolutionary tricks up their sleeves in order to survive tough times. He points to the success that small animals in general have had after mass extinctions and attributes that to their ability to rapidly change and adapt. Thorius species, he thinks, may have retained the capability of making upper teeth, even if their tooth-building program became short-circuited. The reappearance of upper teeth in the four salamander species, says Hanken, “offers an example of latent developmental potentialities that reside within living species but which may not be manifest or expressed until far into the future.” 13. 7TH INTERNATIONAL CONGRESS ON VERTEBRATE MORPHOLOGY MEETING Snake Tartare--Quite a Bodyful 1. Elizabeth Pennisi BOCA RATON, FLORIDA— From 27 July to 1 August, animals with a backbone drew the attention of morphologists, evolutionary biologists, and other researchers. Feasting on everything from ant larvae to mammals seemingly too big to swallow, snakes have eclectic tastes. Some even like to eat other snakes. Such slithering snacks present particular challenges if the snake being consumed is longer than the snake doing the eating. “It's a little like me swallowing you,” says Margaret Rubega, a functional morphologist at the University of Connecticut, Storrs. At the meeting, Kate Jackson, a herpetologist now at the University of Toronto, Canada, described how x-ray scans and old-fashioned dissection revealed that a surprisingly stretchy stomach holds the key to successful snake consumption. The study, says Rubega, is “a wonderful, creative use of a variety of tools.” While at Harvard University, Jackson bought juvenile king snakes, reputed snake eaters, and corn snakes from a pet store. When she and her colleagues put the two species into a cage, the snakes would immediately turn into a writhing ball of whipping heads and tails. After just a few minutes, however, the king snake would typically sink its teeth into the corn snake. The king snake, which is not venomous, would then spend the next 8 hours squeezing its prey to death. Once it had subdued its meal, the king snake would start with the head of the corn snake.* Swallowing required two motions, Jackson reported. As is typical for some snakes, the left and right sides of the jaw can move independently, and each side alternated between grabbing the prey and pulling it back—a “jaw walk,” says Jackson's colleague Elizabeth Brainerd, a functional morphologist at the University of Massachusetts, Amherst. The king snake eventually switched to a different swallowing technique. It would grab hold of its prey, then kink up its vertebrae, and finally, let go and straighten out. “It slides the body over the prey,” says Jackson. Within 2 hours, a corn snake would disappear down a king snake's gullet. Jackson expected ingestion to come to an abrupt halt once the king snake had swallowed the equivalent of two-thirds of its length; that's the end of its stomach. But the king snake managed to cram in the whole corn snake. A dissection of the newly satiated snake revealed how it achieved this gluttonous feat: “The stomach was stretched to 91% of its body cavity,” Jackson reported. All the other organs were squished out of the way. “I am amazed at the way they do it,” comments David Wake, a herpetologist at the University of California, Berkeley. The stomach's stretchiness could only partly explain how the king snake swallowed prey bigger than itself. Telltale bulges down the length of the king snake suggested another trick. When Jackson and her colleagues x-rayed a king snake with its ingested prey, they discovered that the corn snake was, in the words of Brainerd, “compressed like an accordion.” Jackson found that even after a king snake had finished taking a corn snake down its throat, it sometimes spit the whole snake back up, particularly if startled. “That's a big risk,” says Wake, because it takes so much energy to procure such a meal in the first place. On the other hand, a yen for snakes has its advantages. For its size, the king snake gets the richest meals of all the nonvenomous snakes. “The king snakes are able to get the energy input of a very large meal without having the large mouth-gape specializations and venom of vipers,” says Brainerd. Thus, Jackson proposes, even if a dinner is sometimes wasted, it's worth the effort. 14. Coming to Grips With Bone Loss 1. Jean Marx A better understanding of osteoporosis is leading to new therapies for preventing and treating the bone-weakening disease Slowly and insidiously, the bones deteriorate, losing minerals and structure. A surprise fracture, usually of the hip, wrist, or one of the vertebra of the spinal column, is often the first indication that osteoporosis has been weakening a patient's bones for years. The consequences can be dire. One-fifth of people older than 50 die within a year of a hip fracture, and many others end up in nursing homes—a fate some consider even worse than death. Researchers have long known that estrogen deficiency, such as that occurring at menopause, leads to fragile bones. That's why women account for about 80% of the estimated 10 million osteoporosis patients in the United States. Yet the most obvious preventive strategy, hormone replacement therapy (HRT), has fallen out of favor since the Women's Health Initiative found that extended HRT increases the risk of both breast cancer and cardiovascular disease (Science, 14 November 2003, p. 1136). Fortunately, other drugs have come on the market in the last decade to take up the slack. Most of these, such as the bisphosphonates, which include alendronate (Fosamax) and risedronate (Actonel), primarily act to prevent bone loss. “They are working extremely well,” says osteoporosis researcher B. Lawrence Riggs of the Mayo Clinic in Rochester, Minnesota. “They decrease the fracture rate by about 50%.” Such developments are bringing new patients into the clinic. Randall Stafford and his colleagues at Stanford University in Palo Alto, California, reported in the 26 July issue of the Archives of Internal Medicine that the number of physician visits for osteoporosis increased from 1.3 million in 1994, which was just before alendronate came on the market, to 6.3 million in 2003. Even so, Stafford notes, osteoporosis still goes undiagnosed in millions of people. And current treatments aren't perfect. “The problem is 50% [of patients taking the drugs] still have fractures,” Riggs says. “What you would really like to do is put the bone back to the point where fractures won't occur at all.” So an intense hunt is on for drugs that can reverse the dangerous handiwork of osteoporosis. A new drug that came on the market about 2 years ago is a step in that direction. Called teriparatide (Fortéo), it's a 34-amino-acid fragment of parathyroid hormone (PTH) that has been shown to increase bone mass. Teriparatide has its drawbacks, however: It has to be injected daily, much like insulin for diabetes, and there are other limitations on its use. Additional bone-building treatments, however, are showing promise in early stages of testing. Researchers are also making headway in the search for new ways to prevent bone loss from occurring in the first place, a hunt that is fueled by new insights into both normal and osteoporotic bone. In particular, they've gotten a much better picture of how estrogen acts to preserve bone, information that may lead to new compounds that share the hormone's protective skills but not its dangers. Dynamic bone People tend to think of bone as a rigid, inert material that holds up their bodies. But bone is far more dynamic. It continuously dissolves and re-forms. Indeed, adults replace their entire skeletons roughly every 10 years. “Bone is like skin. You're constantly remodeling it,” says Susan Greenspan of the University of Pittsburgh School of Medicine in Pennsylvania. This remodeling is carried out by two types of bone cells: the bone-building osteoblasts and the bone-dissolving osteoclasts. The two cooperate like “teams of workers repairing potholes,” says Stavros Manolagas of the University of Arkansas for Medical Sciences in Little Rock. “The osteoclasts dig a hole, and the osteoblasts fill it in and repair it.” The bisphosphonates help preserve bone by binding to its surface and inhibiting osteoclast activity. To maintain strong bones, both types of cells have to work equally hard. But with age, and the resulting loss of the sex hormones, particularly estrogen, osteoclasts gain the upper hand. The cells gradually rob bones of their minerals, weakening the skeleton over time. Recent findings indicate that estrogen is key in men as well as in women. Riggs notes that the critical estrogen concentration is about 30 nanograms per milliliter of blood. “Below that,” he says, “men begin to lose bone.” By age 70, he adds, about 50% of men and 100% of women have such estrogen deficiencies. Although osteoporosis diagnosis currently depends on scans showing diminished bone density, other less readily detectable changes in bone structure also contribute to bone-fracture risk. “Osteoporosis is not just a reduction in bone density. There are also dramatic changes in bone microarchitecture,” says David Dempster of Helen Hayes Hospital in West Haverstraw, New York. For one, the pits left when the bone's potholes go unrepaired are points of weakness—stress risers in mechanical engineering terms—that make bones more prone to fracture. In addition, certain areas inside bone have a lacelike structure of interconnected plates and rods with the bone marrow in between. In the early stages of osteoporosis, Dempster says, the rods deteriorate, destroying the connectivity in the internal bone superstructure. A few years ago, Erick Legrand, Maurice Audran, and their colleagues at the Centre Hospitalier Universitaire d'Angers, France, reported that this loss of connectivity is a risk factor, independent of bone density, for fractures in men with osteoporosis. Such findings indicate that there is room for improvement in identifying persons at risk of developing osteoporosis. “We don't have a good test to use in the clinic to assess other aspects of bone strength” besides density, says Nelson Watts of the University of Cincinnati Bone Health and Osteoporosis Center. Researchers are investigating a number of molecular markers of bone turnover, such as breakdown products of the bone protein collagen that can be detected in the blood or urine. There is a problem, though, with using such markers for diagnosing osteoporosis or assessing the effects of therapy: Bone turnover fluctuates from day to day. This “variability is a big issue,” says Markus Seibel of the University of Sydney at Concord Repatriation General Hospital in Australia. View this table: The parathyroid connection When a physician does identify a person with osteoporosis, or one who is at risk of the condition, prescribing bisphosphonates to stop further bone loss is a relatively easy call. But building new bone remains a challenge, which is why there's a lot of excitement about the recent approval of the PTH derivative teriparatide. In clinical trials, it decreased fractures by as much as 75% and also increased bone mineral density by roughly 10%. At first glance, PTH would seem to be a poor choice for a bone-building drug. People whose parathyroid glands are overactive suffer bone loss, not gain. But several decades ago, researchers found that intermittent PTH administration, as opposed to the continuous overexposure to the hormone that occurs in hyperparathyroidism, fosters bone formation. “The same agent can produce either bone gain or bone loss, depending on how long it's present,” says Robert Neer of Harvard's Massachusetts General Hospital in Boston, an early pioneer of PTH research. Why that happens remains unclear, but researchers have some clues. Riggs, Sundeep Khosla, also of Mayo, and their colleagues have evidence that intermittent PTH treatment increases osteoblast formation by stimulating production of insulin growth factor 1, whereas continuous PTH increases osteoclast formation. Intermittent PTH administration may also help osteoblasts live longer. Manolagas and his colleagues found that in osteoblasts, PTH suppresses a form of cell death called apoptosis by increasing production of proteins needed for cell survival, such as Bcl2, while triggering other changes that inactivate proteins needed for apoptosis. But if the cells are exposed to the hormone for long periods, changes are set off that lead to the degradation of the survival factors and trigger apoptosis. Thus, repeated brief exposures to PTH promote osteoblast accumulation, but continued exposure tips the balance the other way and osteoclasts gain the upper hand. Although there's no doubt that teriparatide works well, a glitch turned up during its testing that has resulted in its use being limited to a maximum of 24 months. The drug caused osteogenic sarcomas, a form of cancer, in rodents. No cancers have been detected in other species, including nonhuman primates, nor has hyperparathyroidism been linked to increased cancer incidence. But because teriparatide can't be taken indefinitely, researchers have begun testing whether following it with other drugs preserves the hormone's benefits. In June, John Bilezikian and his colleagues at Columbia University College of Physicians and Surgeons in New York City reported that osteoporotic men who took a bisphosphonate after teriparatide not only maintained their bone density but showed an additional 5% gain by 1 year after they ceased taking the hormone. In contrast, men who opted not to take the second drug showed a bone density decline of nearly 4%. A PTH relative that has not yet reached the market is also showing promise in early testing. Andrew Stewart, Mara Horwitz, and their colleagues at the University of Pittsburgh have been studying a protein called PTHrP, originally identified as a product of cancer cells, which causes extreme increases in blood calcium concentrations in some patients. Further work showed that all cells make the protein, although in much smaller quantities, and that its structure resembles that of PTH. Follow-up experiments established that the protein stimulates bone formation in ways that are not yet understood. In a pilot study published last year, Stewart's team found that PTHrP boosted bone density in postmenopausal women by 4% to 5% in 3 months, apparently without stimulating bone resorption. As important, PTHrP didn't increase blood calcium levels or cause other side effects. “It sounds like the Holy Grail that people have been looking for,” says Neer. PTHrP, like PTH, has to be injected, however. How estrogen helps bones Although estrogen can't build bone the way PTH can, it can protect against bone loss. Scientists have known for some time that estrogen safeguards bones by keeping osteoclasts in check. Now they are learning just how the hormone does that—information that is pointing to potential new ways to prevent and treat osteoporosis. The development of osteoclasts is triggered by a signal sent by their partners in bone remodeling, the osteoblasts. About 6 years ago, William Boyle, David Lacey, and their colleagues at Amgen Inc., a biotech firm in Thousand Oaks, California, identified that signal. It's a protein called RANK ligand (RANKL), which osteoblasts and their immature precursors secrete. As its name implies, RANKL binds to a protein called RANK (receptor activator of NF-κB), which sits on the cell surface of immature osteoclasts. This binding both promotes the cells' differentiation and prolongs their survival by suppressing apoptosis. RANKL triggers “the final pathway by which osteoclasts are formed and leads to bone resorption,” says Khosla, whose team at Mayo studies this pathway. A variety of evidence points to estrogen as a key regulator of osteoblast signaling. For example, animal studies have shown that estrogen deprivation leads to increased production of a variety of regulatory cytokines, such as interleukin-1βinterleukin-6, and macrophage colony-stimulating factor, which boost RANKL production and thus osteoclast formation. And last year, the Mayo group, working in collaboration with Boyle and Lacey, implicated RANKL changes in postmenopausal osteoporosis. The researchers used fluorescent-activated cell sorting to isolate osteoblast precursor cells from 12 premenopausal women, 12 women in early menopause, and another 12 menopausal women who were taking HRT. They found that the cells from the untreated menopausal women carried much higher levels of RANKL than did those from the women in the other two groups. The RANKL concentrations also correlated with the concentrations of certain collagen breakdown products in the women's blood and urine, an indication that the high RANKL levels contribute to bone loss. Given such data, blocking the function of RANKL is an obvious strategy for preventing and treating osteoporosis. Osteoblasts make their own RANKL inhibitor, a protein called osteoprotegerin (OPG) that was previously identified by the Amgen team. It's a truncated form of RANK that is not bound to a cell membrane. When present, OPG effectively vacuums up RANKL molecules, taking them out of action before they can bind to the functional receptor on osteoclast precursors and stimulate their development. The estrogen β-estradiol turns up OPG production, providing another way in which the hormone can counter osteoclast action. Although Amgen has done some early testing of OPG itself as a way to block RANKL action, the company is now concentrating on an antibody called AMG 162 that also takes RANKL out of commission. In the July Journal of Bone and Mineral Research, the company reported that a single dose of AMG 162 given to postmenopausal women produced a sustained decrease—lasting up to 6 months—in bone resorption, as indicated by a marked drop in the production of a collagen degradation product called NTx. Advanced clinical trials to more fully assess the effectiveness of the antibody are getting under way. An antibody such as the Amgen product may be one way to replicate estrogen's effects on bone without affecting other tissues, but researchers are investigating others as well. Take the selective estrogen-receptor modulators (SERMs), which are designed to mimic the hormone's actions on some of its receptors, say those on bone, but not those on other tissues such as the breast or uterus. One SERM, the drug raloxifene (Evista), is already on the market as an osteoporosis therapy. Raloxifene, like the bisphosphonates, is generally thought to block bone dissolution without actually building new bone. One new type of estrogen mimic may have bone-restoring potential, however. Many of estrogen's effects on reproductive tissues are initiated when the hormone binds to its receptor, which then migrates to the cell nucleus, where the duo triggers various changes in gene expression. Calling on ANGELS But about 3 years ago, Manolagas and his Arkansas colleagues found that the estrogen receptors on bone cells have a second mode of action that does not require their transport to the nucleus. It works instead through a cytoplasmic signaling path. The researchers also showed that estrogen uses this alternate path to block osteoblast apoptosis. This suggested that a drug that mimics this action could boost osteoblast activity without having the harmful side effects associated with estrogen itself. Since then, the Manolagas group has identified a compound that they call estren (4-estren-3α,17β-diol) that triggers this same receptor action. It inhibits osteoblast apoptosis and also promotes the death of osteoclasts, thus increasing bone formation—all without apparent effects on the animals' reproductive organs. Manolagas has dubbed estren and similar drugs ANGELS—for activation of nongenotropic estrogen-like signaling—to indicate that their specificity is based on their mechanism of action rather than on receptor selectivity, as is the case with the SERMs. Although new drug therapies for osteoporosis are on the horizon, some note that it would be unwise to forget the tried and true. In his survey, Stanford University's Stafford found that while prescriptions for the new drugs were increasing, recommendations for taking calcium and vitamin D supplements and performing weight-bearing exercise—all known to help build stronger bones—were decreasing. “With the reliance on these new medications, physicians may be neglecting some of the simpler interventions,” he says. Not to mention cheaper: A year's treatment with teriparatide costs about$7000, compared with a few dollars a month for the supplements.

The role of vitamin D in particular may be underrated, says Michael McClung of the Oregon Osteoporosis Center in Portland. A meta-analysis published in the 28 April Journal of the American Medical Association by Heike Bischoff-Ferrari and her colleagues at Harvard Medical School in Boston reveals that supplementation with the vitamin decreases fall rates—and therefore a number of the fractures—apparently because it helps improve muscle strength in addition to boosting bone mineralization. “From a clinical viewpoint, that's as important as new drugs,” McClung says.

All in all, osteoporosis researchers are highly encouraged by the progress they are making. “Ten to 15 years ago, there were no decent treatments for osteoporosis and not much on the horizon,” Stewart says. “We've gone from nothing to a set of very effective drugs.”