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Clone farm Billions of identical chickens could soon be rolling off production lines

FACTORY farming could soon enter a new era of mass production. Companies in the US are developing the technology needed to "clone" chickens on a massive scale.

Once a chicken with desirable traits has been bred or genetically engineered, tens of thousands of eggs, which will hatch into identical copies, could roll off the production lines every hour. Billions of clones could be produced each year to supply chicken farms with birds that all grow at the same rate, have the same amount of meat and taste the same.

This, at least, is the vision of the US's National Institute of Science and Technology, which has given Origen Therapeutics of Burlingame, California, and Embrex of North Carolina $4.7 million to help fund research. The prospect has alarmed animal welfare groups, who fear it could increase the suffering of farm birds. That's unlikely to put off the poultry industry, however, which wants diseaseresistant birds that grow faster on less food. "Producers would like the same meat quantity but to use reduced inputs to get there," says Mike Fitzgerald of Origen.

To meet this demand, Origen aims to "create an animal that is effectively a clone", he says. Normal cloning doesn't work in birds because eggs can't be removed and implanted. Instead, the company is trying to bulk-grow embryonic stem cells taken from fertilised eggs as soon as they're laid. 'The trick is to culture the cells without them starting to differentiate, so they remain pluripotent," says Fitzgerald.

Using a long-established technique, these donor cells will then be injected into the embryo of a freshly laid, fertilised recipient egg, forming a chick that is a "chimera" (see Diagram). Strictly speaking a chimera isn't a clone, because it contains cells from both donor and recipient. But Fitzgerald says it will be enough if, say, 95 per cent of a chicken's body develops from donor cells. 'In the poultry world, it doesn't matter if it's not 100 per cent," he says. With its patent still at application stage, Origen is unwilling to reveal if it can reliably obtain such chimeras. But it has occasionally created the ideal: chicks that are 100 per cent donor-derived, or pure clones.

Another challenge for Origen is to scale up production. To do this, it has teamed up with Embrex, which produces machines that can inject vaccines into up to 50,000 eggs an hour. Embrex is now trying to modify the machines to locate the embryo and inject the cells into precisely the right spot without killing it. Automating the process will be tricky, admits Nandini Mandu of Embrex. Even when it's done by hand, up to 75 per cent of the embryos die.

In future, Origen envisages freezing stem cells from different strains of chicken. If orders come in for a particular strain, millions of eggs could be produced in months or even weeks. At present, maintaining all the varieties the market might call for is too expensive for breeders, and it takes years to breed enough chickens to produce the billions of eggs that farmers need.

Fitzgerald insists that genetic modification isn't on Origen's menu. The stem cells will come from eggs laid by unmodified pedigree birds, he says. All the same, Origen's website says the company has licences for tools for genetically engineering birds, and it talks about engineering birds that lay eggs containing medical drugs.

Animal welfare groups say that it would be cruel if breeders used the technology to mass-produce the fastest-growing birds. Some birds already go lame when bone growth doesn't keep pace with muscle growth. 'The last thing they should be doing is increasing growth rates," says Abigail Hall of Britain's Royal Society for the Prevention of Cruelty to Animals.

There are other dangers. If one bird were vulnerable to a disease, all its clones would be too. But if one set of clones fell victim to a disease, the technology wbuld allow farmers to 'roll out" a resistant set rapidly.

There could also be benefits for consumers, as farmers could quickly adopt strains that don't carry food-poisoning bacteria such., as Salmonella, for instance. Whether shoppers will buy meat from a clone, even if it's not genetically engineered, remains to be seen. And the FDA has yet to decide whether meat and milk from cloned animals is fit for humans. Andrea Graves

Clone encounters When three would-be human cloners came face to face with scientists who regard their plans as irresponsible and dangerous, emotions ran high.
Philip Cohen describes an extraordinary meeting

WE WILL clone humans. That was the blunt message of three renegade scientists when they confronted top animal cloners and fertility experts in Washington last week.

The normally sedate atmosphere of the National Academy of Sciences changed dramatically when Italian fertility specialist Severino Antinori, his colleague Panayiotis Zavos of the Andrology Institute in Kentucky and Brigitte Boisselier of Clonaid took the stage. With the world's media in attendance-at one stage camera crews even pursued Antinori as far as the toilets-it was more like a Hollywood event than a staid scientific inquiry.

The trio had been invited to give evidence by the academy, an independent organisation that is preparing a report on possible uses of cloning technology, such as growing tissue for transplants. Antinori was an obvious choice, since his intention to clone humans is well known.

He is already notorious for pushing the ethical boundaries in reproduction. On one occasion, he helped a 62-year-old women conceive a child through IVF. On another, he claimed to have produced babies using human sperm matured in rodent testes.

Speaking in a thick accent that at times left his audience baffled, Antinori dismissed any worries about the safety of cloning. "Therapeutic cloning", he said, could be

used to treat infertility where no other treatment existed-for instance, in men who produce no sperm. Any defective embryos could be screened out by weekly genetic tests on the embryo and imaging techniques such as ultrasound on the fetus, he claimed.

Antinori's use of the term "therapeutic cloning" for fertility treatment angered other scientists like Jose Cibelli of Advanced Cell Technology in Massachusetts. As Cibelli later pointed out, the term is usually used to describe the creation of stem cells for transplant via cloning techniques, not reproductive cloning. In the US, researchers are fighting to stop this being banned along with reproductive cloning.

The human cloners' upbeat tone continued when Zavos took the mike. He cited animal cloning studies in which 30 per cent of implanted embryos produced live clones. He dwelt on one Japanese experiment in which eight live cows were cloned from 10 embryos. 'Like we say in Kentucky, this ain't hay, this is 80 per cent," he said. "In human IVF you get only 30 per cent success, and you are happy if you do that."

Strangely, after praising their work, Zavos then began berating the animal cloners. He singled out for personal attack the creator of Dolly the sheep, Ian Wilmut of the Roslin Institute, and Rudolf Jaenisch of the Massachusetts Institute of Technology, who have both spoken out about the perils of attempting to clone humans.

Many animal clones have life-threatening genetic and physiological problems, researchers like Wilmut have found. Often the defects only become apparent late in gestation or soon after birth. For that reason, nearly all experts in cloning believe it is too early to use the technology to produce a human being.

But Zavos insisted that any health problems in the clones created so far weren't caused by flaws in the technology. 'Those difficulties are due to poorly designed experiments, poorly approached experiments and poorly understood and interpreted experiments, and I have to say that some of them were done for fame and fortune," he said. His comments evoked a mixture of gasps and nervous laughter from the listeners, astounded that Zavos was not only making such criticisms-he has yet to clone anything himself-but also had the cheek to attack others for seeking fame and fortune.

Next on was Boisselier. Her company, Clonaid, was founded by a cult called the Raelian Revolution, which believes that humans were created by extraterrestrials and that cloning is the way to achieve immortality. She called for openness among scientists about cloning, but showed no slides, presented no data and said that since she worked for a private company she couldn't discuss the details of her work.

At one point, she even suggested Clonaid had already created human embryos through cloning techniques, but later declined to confirm it. She also claimed a major advance-a technique to screen individual cells for abnormalities in the "imprinting" of up to 10 human genes. Imprinting can affect gene expression, and faulty imprinting has been blamed for the abnormalities in clones. "Do I have any concern about harm that should be done to a child or to a mother [who] would carry a cloned child?" she concluded. "I do not have any concern."

Many of the participants wound up ftustrated that the would-be cloners revealed little other than their determination to go ahead, and their ability to attract the media spotlight. One of the panel's moderators, Irving Weissman of Stanford University, politely pushed them to be more forthcoming: 'I'm inviting Drs Antinori, Boisselier and Zavos, if you wish to supply us with some of the data ... that informs your judgement, please do so in the next week."

Even in the little that the three did reveal, there was plenty of grist for angry exchanges between participants. Jaenisch said the genetic defects in clones were too subtle and too widespread to be detected as Antinori described. 'To say you can prescreen embryos and determine whether a given clone is normal or abnormal I think is false. The methods don't exist," he said. Alan Colman of PPL Therapeutics, a Scottish cloning company attached to Wilmut's institute, said that Zavos had interpreted the animal data too optimistically. For example, Colman pointed out that four of the eight Japanese cows Zavos was so impressed by had died shortly after birth.

And Boisselier's implication that she could already screen out a lot of defects left many in the audience sceptical, while other, dismissed it outright. "I don't think that ;" it all possible," said Alan Troilnson of Monasb University in Australia.

But even in this surreal atmosphere, a few snippets of new science emerged For instance, there has alivays been some doubt as to whether cloning really reprograms the genome of specialised cells or whether the process simply selects for way ward primitive cells.

Colman told the meeting that his team has started to address this point by analysing the molecular properties of a single cell from skin before it was allowed to dixide and its progeny successfully used to make clones. "It was not an errant embryonic stem cell," said Colman.

Another insight came from jaenisch. Genetic errors that are introduced into cells as they are cultured in the lab have emerged as a major suspect in the hunt for the health problem of clones. But jaenisch revealed preliminary data that clones derived from cumulus cells, which are never cultured, also have these problems. So the sources of clone health defects must extend beyond so-called cell "culture shock". Indeed, one theme that emerged at the meeting was how mtich is still unknown about cloning. B'Llt to Mark Siegier, -i (ioctor and ethicist at the tjniversity of Chic,,igo, it was clear that Antinori, 7al,os -And Bo-elieT are not scared of the unknotvn. "It soiinds as if [they] are likely to proceed with cloning humans despite animal data that raises concerns and worries about it.

Two cheers Bush meets stem cell researchers half way

IN A reversal of fortune for biomedical researchers in the US, President Bush announced last week that he will allow federal funding for limited research oii stem cells taken from human embryos.

Embryonic stem cells (ESCS) have the ability to develop into any type of cell in the body, something scientists hope will allow them to grow replacement tissues for transplants, and treat diseases such as Alzheimer's, Parkinson's and diabetes. The US government will now support research on ESCS, but only ones from existing cultures.

In Britain, it is legal to extract ESCs from discarded IVF embryos and use thern for research into fertility or treatments for disease, or to take them from embryos made for therapeutic cloning research. The same work is legal in the US if it's privately funded. But critics find this kind of research morally repugnant because it involves destroying human embryos.

During his election campaign, Bush promised to ban government funding for ESC research. His hard-line attitude drew criticism from patierits suffering from diseases that ESCs may some day treat. Bush says he has tried to balance all these concerns in his decision. "I have concluded that we should allow federal furids to be used for research on these existing stem cell lines where the life-and-death decision has already been made," he said.

The move has met with a mixed response from researchers. 'The proposed compromise will slow the research," says Jaii-ies'f'homson of the Univefsity of Wisconsin in Madison, whose team pioneered the extraction of human ESCS. "But the compromise is better than halting the research entirely.11 Experts disagree over how many lines there af e and how long they will retain their ability to transform into other cell types. Some scientists argue that the 60 existing cell lines that Bush cited are insufficient.

Others say genetic differences could mean some embryos are more suitable sources of stem cells for research than others. Diane Krause, a stem cell researcher at Yale University, adds that limiting the genetic diversity of the stem cells available could hamper work on treatments for certain diseases. "We need to see a variety of these in order to fully understand the applications to niultiple different diseases," Krause says. "It will be good enough for some purposes, but it will be limited."

Despite all these reservations, some researchers welcomed Bush's change of heart. "I'm enormously relieved," says George Daley, a stem cell researcher at the Whitehead Institute in Cambridge, Massachusetts. "This will eneigise the scientific community. It's about as good an outcome as we could have anticipated."

Philip Cohen, San Francisco, and Emma Young

Light getting faster

THE cosmic speed limit-the speed of light-may have, Increased as the Universe matured. New research seems to confirm hints that one fundamental constant, and possibly the speed of light as well, has changed slightly over time.

The notion turns traditional physics on its head. -if it holds up, it surely has to be one of more important discoveries in fundamental physics,' says John Webb, an astrophysicist at the University of New South Wales in Sydney. Three years ago, Webb and his colleagues reported that they had measured what's called the 'finestructure constant at different points in the Universe's past using observations trom a telescope on Mauna Kea, Hawaii.

This constant , which depends on three other supposedly fixed quantities, including he speed of light can be deduced from the wavelengths of light absrbed by gas clouds between earth and distant quasars. Webb's results hinted that 6 billion years ago the fine-structure constant was smaller by about I part in 100,000 (New Scientist, 28 March 1998, p:12). Now his team has gathered twice as much data and has found that the change shows up even more strongly, and as far back as 12 billiony years ago.

The variable 'constant' contradicts the standard model of particle physics, says Brian Greene, a physicist at Columbia Univemity in New York. But it might fit into one unifying all the forces of nature he says.

Webb's team has done a very careful analysis says David Tytler but he would like to see it repeated with a different telescope and another analysius program to rule out any conceivable sources of error.

Cosmic night We're peering into the dark ages that shrouded the early Universe

ASTRONOMERS have at last seen the shadows of the first atoms that formed after the big bang. The finding should allow t hem to pin down when the "cosmic dark ages" ended and the first stars and galaxies began to light up space.

The cosmic dark ages stretched roughly from 300,000 to 900,000 years after the big bang. They began when the fledgling Universe cooled to 3000 kelvin, cold enough to allow electrons and protons to stick together to make light-absorbing hydrogen atoms. They ended when galaxies of stars formed from the hydrogen shone brightly enough to ionise the remaining hydrogen gas, turning it back into a thin, translucent plasma of electrons and protons.

No one has peered into the dark ages to see the first stars lighting up. But now astronomers have found the shadows of the primordial hydrogen in light from the most distant quasar known, which lies around 14 billion light years from Earth. This quasar appears to have burnt towards the end of the dark ages, says Robert Becker, an astrophysicist at the University of California, Davis.

The quasar's light that reaches Earth lacks wavelengths in a telltale range, Becker's team says in a report submitted to the Astronomical journal. The observation implies that 14 billion years ago, space contained hydrogen gas that soaked up this part of the quasar's radiation.

Astronomers have hunted for a quasar with this hallmark gap in its spectrum since it was predicted 35 years ago. But finding

one is difficult because these distant objects are extremely faint. 'It's really been a question of getting telescopes and databases big enough to see far enough back," Becker says.

Indeed, to bag their prize quasar, Becker and his colleagues had to use three different telescopes. They first spotted the quasar using the Sloan Digital Sky Survey's 2.5, metre telescope at the Apache Point Observatory in New Mexico. They then studied its spectrum with a second 3.5-metre telescope at Apache Point and with the 10-metre Keck 11 telescope at Mauna Kea in Hawaii.

The researchers would like to confirm their result by spotting other similar quasars. But ground-based observatories may struggle to see any farther into the dark ages. Because of the expansion of the Universe, light from more distant objects is stretched to nearinfrared wavelengths and beyond. Optical telescopes don't detect such radiation, and ground-based infrared telescopes can't see very faint objects through the warm glow of the Earth's atmosphere. So the task of finding the very first stars and galaxies will probably fall to the Next Generation Space Telescope (NGST), the mammoth space-based infrared [email protected] that NASA plans to launch in 2009. Mark Dickinson of the Space Telescope Science Institute in Baltimore, Maryland, says the observations of the distant quasar should help fine-tune the NGST's design. "It wail be very important for planning and designing the NGST," Dickinson says. "It gives us a better indication of what we should be looking for." Adrian Cho

The Weakest Link

SAVING the world used to be the job of superheroes. But now, with millions of plant and animal species facing extinction, it's down to us mere mortals. Where do we begin? We don't even know how many species are out there. And even if we did, the numbers are meaningless until we know how the different species interact. Collecting all this detail is a Herculean task. Yet without the detail, how can we know which human activities are most likely to have apocalyptic consequences, let alone work out ways to avoid them? What we need is a way to make predic tions based on the information we already have. But the fledgling science of ecology has struggled to describe the natural world, let alone understand it. Like early astronomers, ecologists are faced with a unique system that doesn't lend itself to scientific methods such as experimentation, e replication or manipulation. However, just as stargazers learnt to predict eclipses and alignments of planets, ecologists are now starting to build models that can explain patterns in nature and help predict how ecosystems will react to change. One pioneer of this approach to under standing biocomplexity is Neo Martinez from San Francisco State University in Cali- ~ fornia. He has made a career of studying e food webs-in other words, who eats who within any ecosystem. Charles Darwin once described such webs as intractable "tangled banks". But Martinez is starting to trace the strands that tie the beautiful mess together. He has come up with a way to discover how the animals and plants in a given community interact, without resorting to exhaustive observation and sampling. His computer models open the door to a better understanding of how specific extinctions affect biodiversity as a whole. Martinez's breakthrough came when he noticed curious patterns in the links between trophic species in food webs. When e it comes to understanding natural relation ships, trophic species-groups of organisms that share the same predators-are more rel evant than biological species. They also make up a much larger fraction of the bio diversity under scrutiny. Working at Little Rock Lake in Wisconsin, home to a notoriously co~nplex food web containing 92 such species, Martinez discovered that each species was either prey for or preyed upon by 10 per cent of all the other species. He describes this in terms of "connectance"-the fraction of predator links actually present out of all those possible within a food web.

What's more, this percentage of links between species-the connectance-did not change as Martinez added new species to build up a detailed picture of the system. "The constant-connectance hypothesis asserts that a particular balance of food-web complexity exists in nature," he says. "This balance is between everything eating everything and everything eating nothing." And his trawl of the literature confirmed the pattern in a variety of complex ecosystems, from deserts and islands to estuaries and lakes. Ten per cent wasn't a magic number, but whatever the connectance within a given ecosystem, it remained curiously constant no matter how many new species were added to the food web.

No single ecological or biological theory could predict or explain such a pattern. What was going on? Martinez suspected the answer lay in the way new links are created when a species enters the system, whether by migration or evolution. To investigate what happens when a new species lands in the web, he teamed up with Richard Williams from San Francisco State University's Romberg Tiburon Center for Environmental Studies. Their mathematical model started with the notion that complex food webs arise from a simple pecking order. Then they added two rules. First, that species higher up in a fixed pecking order tend to eat those lower down. And secondly, that if an organism eats two species in a web then it must also eat all the intervening species in the hierarchy. So, for example, a shark that preys on large fish such as tuna and small fish including mackerel will also eat cod and any other medium-sized fish.

By including just two parameters in the model-the number of species in a given web and the connectance between these-Martinez and Williams can accurately predict 12 ecological characteristics of that web. These include the lengffi of food chains, the number of omnivores and cannibals, the distribution of specialists-those with a restricted diet-and generalists-those that eat whatever's going-and perhaps most importantly from a conservation viewpoint, the vulnerability of various groups of species.

When it comes to predicting the way complex natural communities interact, this model is far superior to any other. "It was surprising to me, and I think most people, that a model with such a simple conceptual basis would do such a good job of predicting the properties of observed feeding networks," says Williams.

And a model that shows what's already there has obvious potential to forecast what might be. In any community of organisms, each species fits into its own niche. The niche model devised by Martinez and Williams is novel because it successfully predicts the niche any species will adopt in terms of its "connectedness' to other organisms in the system.

Using the niche model you can build virtual versions of real food webs and then see what happens when you simulate speciation or extinctions. 'We can play games in the computer and see if species at the bottom of the food web are more important to maintaining diversity than those at the top. We can play similar games comparing specialists and generalists,' says Martinez. The niche model could also show how pollutants such as DDT and PCBs accumulate in food webs of different sizes and complexities.

Martinez's approach has been well received. "He has made a huge effort in exploring the regularities displayed by ecological interactions, " says Ricafd Sole from the Santa Fe Institute in New Mexico. "His model with Williams will be a classic reference in ecology. " This could be the leap that ecology has been waiting for. But in some ways, Martinezs thinking is quite conservative because he has natural selection as the driving force behind ecological patterns. Other students of biocomplexity are much more radical. They talk about food webs in the language of the physical sciences, explaining the complexities of nature in terms of "emergent properties" rather than biological principles.

Sole is one such thinker. Working with Jose Montoya of the Complex Systems Research group at the Polytechnic University of Catalonia, Barcelona, he claims to have found the "small worlds' phenomenon in food webs. Small worlds are big news among mathematicians and modellers trying to understand all sorts of complex networks from the Intemet to the nervous system of worms. This is the science behind the folklore that there are no more than six degrees of separation between any two people, and that Kevin Bacon can be linked to any other movie actor in just a few moves (New Scientist, 4 December 1999, p 24).

In essence, a small world is any network containing many nodes that have a few links, together with a few nodes-or hubs-with many links. This arrangement, known as a power law distribution, greatly reduces the number of steps needed to link any two nodes compared with a completely regular network. The distribution of species in food webs fit the pattern, say Sole and Montoya, because most species are connected to a small proportion of others, while a few hub species have many connections. These "keystone species" have long been recognised by some ecologists as the linchpins of ecosystems, essential to the stability of the community. Seeing food webs in this way has advantages, because networks exhibiting small-world phenomena show predictable responses to change. "The very topology of these networks plays a crucial role in how these systems behave," says Albert-LAszl6 Barabdsi of the University of Notre Dame, Indiana. "Finding that food webs follow a power law distribution, just like we see for the cell, and the Internet, suggests that nature displays a high degree of economy when it spins its various networksit uses the same blueprint for most of them." Barabdsi's own work reveals that such complex systems have emergent properties-they are more than the sum of their parts, having properties that emerge ftom the network as a whole. He has found, for example, that the Intemet is inherently stable and well protected against random removal of sites, because most have very few links, and only a concentrated attack could remove the rarer hubs and bring down a large part of the structure. "We have shown that these networks are highly robust against random node removal but fragile against concentrated attacks," says Barabdsi.

In a new study, Sole and Montoya found that food webs can tolerate random removal of species, but that directed removal of keystone species could bring about the collapse of the entire ecosystem. 'Our analysis shows that removal of around 5 to 10 per cent, a small fraction of highly connected species, can lead to ecosystem collapse,' says Sole. The implications for conservation are obvious. A high level of close interconnection between organisms in a shared ecosystem means that biodiversity loss and species invasions may affect many more species than we had anticipated. "It might be the case that some human-driven perturbations could target some of the highly connected species, and thus eventually promote a cascade of extinctions through the system," says Sole.. "If true, then current estimates of biodiversity loss might be much lower than we expected."

But can such a theoretical approach really help at ground level? Stuart Pimm, an ecologist and complexity theorist at the University of Tennessee in Knoxville believes it can. "Finding these broad-scale patterns is a fascinating insight into the way nature works, helping us to rethink old ideas," he says. Pimm says that modelling extinctions has revealed some original insights. "Extinctions are caused by habitat destruction, introductions of new species and hunting. Secondary extinctionswhen a species goes extinct because of the

removal of a closely connected neighbour-we the last part of the deadly quartet." And, says Pimm, the modelling reveals that secondary extinctions are much more important than ecologists suspected. In the real world, this means that many more species might need to be protected. On a positive note, small-worlds modelling could help ecologists identify those organisms whose continued existence is crucial to entire ecosystems. That way, conservationists have their best chance of preventing the runaway collapse of ecosystems through secondary extinctions. But we are running out of time. "The speed of species loss is, sadly, very fast," says Sole. "Many species with low populations are simply going down slowly but inevitably to their extinction."

Barabdsi is more optimistic. He believes that in the next few decades, biocomplexity will take centre stage. "We will leam more and more about the structure, origin and evolution of these systems,' he says. 'Eventually, we all hope that this will culminate in largescale modelling, allowing us to develop the same mathematically rigorous framework for living systems that was so successful in the physical sciences."

Arran Frood is a science writer based in London

Further reading: Signs of Life by Ricard Sole and Brian Goodwin, Basic Books (2000) "Simpte Rules Yield Complex Food Webs' by Richard Wittiams and Neo Martinez, Nature, voi 404, p 180 (2000)

Pangea Revisited

Repeated formation of a pangea anddispersal through formation of a hot plume below from continental thermal insulation