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Scientists Achieve Cloning Success

Hello, Dolly (AP)

Researchers for the first time have cloned an adult mammal, a controversial feat that could presage the ability to clone human beings.

The startling achievement, long thought to be biologically impossible, was accomplished with sheep, the first of which, named Dolly, was born in July in Edinburgh, Scotland.

A total of nine cloned lambs have been born so far using the new technique, each an identical genetic "twin" of the parent from which it was cloned. In theory, the same technique could be used to make unlimited copies of any single adult animal, the researchers said.

The Scottish scientists who conducted the work said their goal was not to clone humans, but to create large herds of specially engineered farm animals -- including some that would produce human medicines in their milk and others that would contain "humanized" organs suitable for transplantation into people.

Herds of cloned animals custom-made to have human diseases could also prove useful in the search for cures for those human ills, they said. Eventually, for example, barns filled with identical sheep all suffering from cystic fibrosis could replace the cages full of mice that are now the workhorses of such research, allowing testing of new drugs on animals whose lungs resemble human lungs much more than mouse lungs do.

The researchers acknowledged, however, that there was no reason in principle why the surprisingly simple technique they used could not be applied to human cells. That could allow virgin women to give birth to identical copies of themselves and might even allow the "resurrection" of genetic duplicates of the recently deceased.

Medical ethicists and others said they could not think of a justification for using the technology on people.

"Most people who have thought about this believe it is not a reasonable use and should not be allowed," said George Annas, a bioethicist and professor of health law at Boston University. "The real question is: How can it be prevented? You can't very well stop a rich person from setting up a lab on some tropical island. You can imagine a wealthy eccentric who thinks there's no one worthy of his inheritance except himself."

Annas said even some of the more compassionate applications, such as using the technique to make a duplicate of child who has died in a tragic accident, were beyond the pale of what most Americans -- including scientists -- believe to be ethical.

"This is not a case of scientific freedom versus the regulators," he said. "I don't think even the Army wants a clone of a special commando unit."

The Scottish researchers denied any interest in making copies of people. "We're simply not interested in working with human material, and we think it would be ethically irresponsible to do so," said Ian Wilmut, who with Keith H.S. Campbell of the Roslin Institute in Edinburgh led the research.

Such research is prohibited in Britain and some other countries, Wilmut said. In the United States, federal funds cannot be used to conduct human embryo research, but there are no legal restrictions on such work done with private funds -- a loophole that some ethicists say should be closed by new laws.

Controversial human applications aside, scientists in this country said they were astounded by the success and overwhelmed by the potential for agricultural and medical advances made possible by the new method. Researchers have tried to clone adult mammals for many years with no hints of success, and most had all but given up.

"It flies in the face of biological dogma," said Neal First, an animal biotechnologist and chairman of reproductive biology at the University of Wisconsin in Madison. "Work in mice and other animals had convinced us all it couldn't be done."

In 1994, First was the first to clone cattle, but he did so by using cells from cattle embryos -- a method that others have used to clone other animals including mice. That technique can be used to create multiple identical animals. But scientists using that method do not know exactly what traits their clones will have because the clones are made not from the genetic material of a single known, existing adult but from undeveloped embryos that are made from a mix of genes from a father and mother.

By contrast, the new work creates identical copies of an adult animal, whose characteristics are known and deemed desirable, using only its genes.

To do so, the Edinburgh team and researchers at Roslin-based PPL Therapeutics took unfertilized eggs from sheep and removed all of the eggs' DNA, leaving behind just the gutted cell with the nutrients and cellular machinery needed to foster embryo growth.

Under normal circumstances, the maternal genes that the scientists removed would have been joined by genes from a sperm, providing a full set of DNA necessary to trigger embryo growth. Instead, the researchers added a full dose of genes from a single mature cell removed from the udder of an adult sheep.

With the egg thus endowed with a full complement of genes, a mere spark of electricity from a lab technician was sufficient to start the egg dividing into an embryo, the researchers found. After a few days in a culture dish, the resulting embryos were transplanted into the wombs of surrogate mother sheep. Each resulting ewe, born a few months later, was genetically identical to the animal that had donated the DNA.

Although scientists have tried similar techniques in the past, they failed to recognize one key requirement, Wilmut said: The donor cell must first be treated with chemicals that "reset" that cell's biological clock in a way that leaves its DNA poised to divide anew.

There is no reason why the same approach couldn't be done with human eggs and cells, inserting the genes of any living -- or perhaps dead -- man or woman into unfertilized eggs and implanting them into a surrogate mother to allow them to develop normally.

Details of the work will appear in Thursday's issue of the journal Nature, but were reported over the weekend by the Observer of London, immediately sending shock waves through scientific and bioethics communities worldwide.

In the United States in particular, where human embryo research has become a political football in recent years, scientists' excitement over the unexpected success was surpassed only by their fears that the feat could lead to overly restrictive limits on related but less controversial areas of research.

"I think some embryo research should be allowed," because it could lead to new treatments for infertility and an understanding of certain inherited diseases, said James Thomsen, a researcher at the University of Wisconsin. "But because emotions are so strong on the subject, this could end up harming good research."

In December 1994, a panel convened by the National Institutes of Health determined that the cloning of humans raised overwhelming ethical concerns and should not be allowed, but that certain kinds of human embryo research were ethical and scientifically valid and ought to be permitted with federal funding.

President Clinton disagreed and immediately directed the NIH not to fund any human embryo research. That move created a regulatory vacuum for privately funded embryo researchers at fertility clinics and universities, who often voluntarily follow whatever guidelines the NIH promulgates. Unwilling to kill their research programs altogether, private research institutes in this country now pursue embryo research without answering to anyone.

Biotechnology industry representatives yesterday tried to assure the public of the industry's high ethical standards.

"We've been opposed to human cloning since the days that it was still a theory, and now that there's an indication it may be possible, we urge it not be done," said Carl Feldbaum, president of the Biotechnology Industry Organization.

"For now, we ought to do what researchers did in the '70s when they weren't sure of the consequences of genetic engineering: They called for a voluntary moratorium on that kind of work. If voluntary restrictions are not sufficient, then perhaps it ought to be prohibited by law," Feldbaum said.

Wilmut of the Roslin Institute said it was still too soon to envision the possibility of generations of identical human clones. "Right now it's a thing for fiction, for films and books. We simply don't know if it's possible," he said.