Thursday, November 15, 2007
Story of the Day - Scientists Clone First Monkey
Scientists clone monkey embryo
Scientists said on Wednesday that they had created the world's first cloned embryo from a monkey, in work that could spur cloning of human cells for use in medical research.
In a paper published online by the British journal Nature, a team in the US said they had created cloned embryos of rhesus macaques, using the same method that famously led to Dolly the Sheep and other genetically duplicated animals.
It is the first time that this technique has been successfully used to create cloned primate embryos.
The group generated two lines of embryonic stemcells from the embryos, according to the research headed by Shoukhrat Mitalipov of the Oregon Health and Science University in Beaverton, Oregon.
Dolly, the world's first cloned animal, was created in 1996, by using so-called somatic cell nuclear transfer (SCNT) in which the genetic core of an egg is removed and replaced with the nucleus of an adult cell.
The egg is then stimulated with chemicals or a jolt of electricity to prompt its division.
The list of other cloned creatures using SCNT includes mice, pigs, cats, cows and dogs.
Until now, though, there has been no cloned primate, for researchers have encountered obstacles that cause cell development to be catastrophically flawed.
Work on primate cloning has also stirred controversy among ethicists, who say it could open the door to cloning human beings, not just cells. In an exceptional move, Nature said it moved forward the release of the paper because of "continuing speculation."
Researchers distinguish between "reproductive cloning" of humans, in which a putative cloned baby would be born and "therapeutic cloning," in which only cloned cells would be used for medical reasons and no baby would result.
'A real worry'
Helen Wallace of Genewatch UK, a British group that monitors cloning and other activities in biotechnology, said the breakthrough announced on Wednesday would cause "a real worry" in some quarters that it would tempt a renegade scientist to create a cloned baby.
"The clear risk of an experiment (in human reproductive cloning) is of a deformed baby and maternal suffering," she told AFP in a phone interview.
"In Britain, we don't think that the technology is going to go that far because there are laws against reproductive cloning," she said. "However, in most countries around the world, there are no legal safeguards."
Stemcells are immature cells that develop into the specific tissues of the body. Embryonic stemcells have the highest capability of all, because they can differentiate into any tissue. Scientists hope to be able to coax these cells into one day becoming replacement tissue for organs that are damaged or diseased.
Transplanted cells from a donor, though, run the risk of being attacked as intruders by the patient's immune system. By creating stemcells that are programmed with the patient's own DNA the risk of rejection would be skirted.
Mitalipov's team said they collected 304 eggs, also known as oocytes, from 14 female rhesus macaques.
The donor nucleus came from skin cells taken from an adult male monkey housed at the Oregon National Primate Research Center.
The claim that the stemcells were an exact DNA copy of the donor monkey's genetic code was validated independently by a team led by David Cram of Monash University in Melbourne, Australia.
That confirmation comes on the heels of a scandal surrounding earlier claims on cloning. In 2004, South Korean scientist Hwang Woo-suk announced he had created 30 cloned human embryos from which he derived stemcells, but his data turned out to be fake.
In a commentary published in Nature, British scientist Ian Wilmut — Dolly's "father" — and colleague Jane Taylor of the Centre for Regenerative Medicine in Edinburgh, Scotland, said the new advance's brightest benefits may lie not in creating replacement tissue from stemcells but in unlocking basic knowledge about inherited disorders.
By making patient-specific cells, doctors could obtain cells whose genome would provide a telltale of a disease. These cells could be compared with healthy counterparts to see what is wrong, and a library of drugs could then be screened to see if a treatment is available.
"Ultimately, this approach might lead to treatments for neurodegenerative diseases, some cancers and psychiatric disorders," the pair said.
Scientists Clone First Monkey
US scientists have cloned a monkey, using the resulting embryos to grow valuable stem cells. The development is the first time a primate embryo has been created, leading experts to speculate that it's a matter of time before human embryos are cloned to treat disease. VOA's Jessica Berman reports.
Researchers at Oregon Health and Science University used the DNA of skin cells from rhesus maquaque monkeys to create embryos from which they extracted stem cells three days later.
In earlier research, the team successfully cloned mouse embryos.
Stem cells are master cells that scientists say can be coaxed to grow into any tissue in the body, making them valuable as a tool for potentially treating or curing human disease.
Robert Lanza is chief of Advanced Cell Technology, a biotechnology firm in Massachusetts.
Lanza says the achievement marks a major milestone in genetic research.
"It's enormously important and a giant step toward showing that human therapeutic cloning is indeed possible," he said. "And it proves once and for all that primate cloning is not impossible as everybody thought."
Observers say it's taken a long time to clone a primate embryo because researchers have had to overcome a variety of genetic challenges.
In a study published in the journal Nature, researchers describe how they used 304 eggs from 14 rhesus monkeys before they succeeded in creating two embryos from which they grew the two stem cell lines.
Supporters of therapeutic stem cell research say the goal is not to make identical copies of animals, but to create embryos so organs can be grown from scratch using the stem cells.
Experts say the tissue grown from embryonic stem cells could potentially provide desperately needed organs to people who need transplants. They say such organs could also be matched to the recipient so the transplanted organ is not rejected.
Lanza says the fact that a primate embryo has now been created means the cloning of a human embryo is a virtual certainty.
"I think the race indeed is on for cloning human embryos for generating patient specific cells. Of course, nobody in the field wants to clone an entire human being," he added. "So, it's only going to be a matter of time before you see a paper showing that this works in humans."
The field of embryonic stem cell research has been marked by controversy. South Korean scientist Hoo Suk Hwang claimed falsely in 2004 to have created the first cloned human embryos, setting back the field.
And in the United States, opponents, led by President George W. Bush, feel strongly that it is wrong to use human embryos in this way. The opposition has led Mr. Bush to block attempts to expand federal funding for embryonic stem cell research.
First cloning of monkey embryo raises hope of a great leap in medical science
Cloned embryos have been created from an adult monkey for the first time, leading scientists to speculate that cloning human embryos using stem-cell therapies is a significant possibility.
The success in the United States, which has been verified by independent scientists, provides the first proof that viable cloned embryos can be produced from primates, which many experts had feared would be so technically demanding that it would be impossible to achieve.
Though further work is required before the technique can be applied to human cells, it suggests that it will be feasible to clone embryos from the DNA of living patients, and to derive working stem cells from them. These embryonic stem (ES) cells could then be transplanted to treat diseases such as Parkinson’s and diabetes without fear of rejection by the body’s immune system. The cells could also be used to study these conditions in the laboratory and to develop new treatments.
Such therapeutic cloning has been a goal for medical research since the birth of Dolly the sheep was announced in 1997, but that initial hope has been tempered by the apparent complexity of primate cloning.
Although some monkey embryos have been cloned before, they have always died before reaching the stage at which stem cells can be extracted and attempts to implant them into the womb have also failed.
Claims by a South Korean team to have cloned human embryos and extracted stem cells generated widespread excitement in 2005, but these were later revealed to have been fraudulent. The only human embryo to have been cloned so far, by a British team, died almost immediately.
These problems had led many scientists to speculate that primate cloning was so difficult that therapeutic cloning would always remain impractical.
A group led by Professor Shoukhrat Mitalipov, of the Oregon National Primate Research Centre, has now created two colonies of ES cells from embryos cloned from the DNA of an adult male rhesus macaque monkey called Semos, named after the ape god in the film Planet of the Apes.
Nuclei from Semos’s skin cells were removed and placed into 304 eggs from 14 female monkeys. The scientists attribute their success to a new technique for handling the eggs during this nuclear transfer process.
Professor Mitalipov first announced his results at a conference in Cairns, Australia, in June. The research has now been peer-reviewed, and was published online yesterday in the journal Nature.
As claims about cloning have often met extreme scepticism, since the disgrace of Woo Suk Hwang, the Korean scientist who faked supposedly pioneering human research, Nature also took the rare step of commissioning an independent assessment of Professor Mitalipov’s results before agreeing to publish them.
The analysis by David Cram, Bi Song and Alan Trounson of Monash University, Melbourne, has confirmed beyond doubt that the two ES cell lines are true clones of Semos. “Proof of concept for creating somatic cell nuclear transfer primate stem cells is firmly established,” they concluded.
The low success rate of 0.7 per cent means that it is still too early to use the new technique to attempt to clone human embryos, especially given the shortage of human eggs available for such research, scientists say. It also means that the method would not yet be a practical way of cloning human embryos for reproductive purposes.
The achievement, however, does suggest that human therapeutic cloning is a possibility. It is also likely to strengthen calls for an international ban on reproductive cloning, as was recently made by an expert panel of the United Nations.
Professor Ian Wilmut, of the University of Edinburgh, who led the team that cloned Dolly the sheep, said: “The group in Oregon are to be congratulated on this achievement. The ability to produce embryo stem cells from cloned human embryos would create entirely new opportunities to study inherited diseases.”
Anna Krassowska, research manager of the UK Stem Cell Foundation, said: “This puts us one important step closer to developing patient-specific ES cell lines, not only for possible therapies in the future but for drug discovery and research into serious diseases. Publishing the independent verification simultaneously was a judicious move, which will put to rest the doubts that would otherwise exist postHwang.”
Professor Robin Lovell-Badge, of the National Institute for Medical Research, who described the work as “very exciting”, said: “The paper is not only the best but also by far the most useful work to date showing that it is possible to carry out the cloning procedure and to obtain ES cell lines in primates.”
From Dolly to Semos
1996 Birth of Dolly the sheep, above, the first mammal cloned with somatic cell nuclear transfer technique. The achievement was announced in 1997
2002 First cloned cat, Cc or Copy Cat, born. Other animals to be cloned include rats, mice and cows
2002 Raelian cult claims birth of first cloned human baby. Story discounted as fantasy
2004 South Korean team led by Woo Suk Hwang announces first cloned human embryo
2005 Hwang’s team announces further human clones, from which stem cells have been extracted
2005 Scientists at Newcastle University produce cloned human embryo, but it dies before stem cells can be removed
2005 Hwang’s human research shown to have been faked. His papers are withdrawn by the journals that published them
2007 Announcement that US scientists have cloned monkey embryos and extracted stem cells