Way OT..Way Interesting
December 9, 1998
Japanese Scientists Clone a Cow, Making 8 Copies
By GINA KOLATA
cientists in Japan report that they have cloned eight calves from cells they gathered from a slaughterhouse, creating eight identical copies of a single cow. Though half of the calves died, some biologists say the results indicate that the cloning of cows may be at least as efficient as in vitro fertilization.
Cows are the third adult mammal to be cloned. The first was a lamb named Dolly, whose birth was announced in February 1997.
She had been cloned from an udder cell.
Then came mice, announced last July. And suddenly cloning, which just two years ago had been thought biologically impossible, is looking like it might be entirely feasible, if not easy, according to cloning experts.
It still seems surprising to some scientists. After all, an adult cell, like an udder cell, has reached its final destiny in the body and under normal circumstances, never changes into something else. But with cloning, an adult cell must reverse its development and become an early embryo cell, able to direct the development of an entirely new animal that is the identical twin of the adult that provided the original cell.
But now, "cloning is becoming routine," said Dr. R. Michael Roberts, a professor of animal physiology at the University of Missouri in Columbia and the chief scientist for the Department of Agriculture's competitive grants program in Washington.
A paper by the Japanese scientists, led by Dr. Yukio Tsunoda of Kinki University in Nara, Japan, describing their cloning of a cow, will be published on Friday in the journal Science. Science lifted its usual restrictions on announcing the results before publication of the paper after The Express in London went ahead and wrote about the results.
Dr. Tsunoda and the others say one reason for cloning cattle would be to reproduce exact copies of animals that are superb producers of meat or milk. In fact, Dr. Roberts said that on a recent visit to Japan he saw a calf that another group claimed it had cloned from cells taken from the ear of a prize bull. Those scientists have not yet published their results, he said.
Dr. Roberts said that several other groups, including some in Japan, say they are successfully cloning adult cows and bulls. Dr. Randall Prather, a cloning researcher at the University of Missouri, said that he and others are predicting that there will be more than 50 calves born in Japan by the end of the year that are clones of adult cows.
But what surprised many cloning experts was not just the fact that a cow was cloned but the ease with which Dr. Tsunoda's group accomplished its task.
"If this is true, it's startling," said Dr. Barry Zirkin, a reproductive biologist at Johns Hopkins University School of Hygiene and Public Health.
To begin the cloning process, the Japanese scientists gathered two types of cells from a Japanese beef cow whose entrails had been discarded in a slaughterhouse: cumulus cells, which cling to eggs and nurse them, and cells from the lining of the cow's Fallopian tube.
Then they used those cells to create embryos, slipping either a cumulus or Fallopian tube cell into another cow's egg from which the genetic material had been removed.
The researchers attempted to add cumulus cells to 99 cow's eggs, of which 47 took up the cumulus cells. Eighteen of the resulting embryos survived in the laboratory for eight to nine days until they were ready to be transferred to surrogate mothers. With the Fallopian tube cells, they used 150 eggs, got 94 of them to take up cells, and ended up with 20 embryos. Dr. Tsunoda's group transferred 10 of their 38 embryos to cows that could serve as surrogate mothers. Eight calves were born. Four of the calves died at or soon after birth; the others survived and appear perfectly normal, the scientists say.
In contrast, when Dolly was created, Dr. Ian Wilmut and his colleagues at the Roslin Institute in Scotland began with about 400 eggs, ended up with just 29 embryos that they could transfer to surrogate mothers and, from that, had just one live lamb, Dolly.
The Japanese investigators assert that although half of their calves died, their deaths appeared to have had nothing to do with the fact that they were clones. One died of pneumonia stemming from heat stroke, two others died from aspirating large amounts of amniotic fluid at birth, the fourth died from complications during delivery.
Other scientists say they are not convinced those four calves were entirely normal. Nonetheless, they say, they are impressed with the astonishing efficiency of the cow cloning -- 80 percent of the embryos transferred to surrogate mothers survived until birth. With in vitro fertilization, said Dr. George Seidel, an animal physiologist at Colorado State University in Fort Collins, about 50 percent of transferred embryos survive until birth.
Dr. Mark Westhusin, a reproductive physiologist at Texas A & M University in College Station who is working on the cloning of cattle and dogs, said, "They have great results, no doubt about it."
Of course, scientists say, there is much more work to be done to understand how cloning works, and why. But, some say, with cloning in three species, and getting exponentially more efficient, it is hard to doubt that humans will be cloned, sooner rather than later. Others urge caution, saying that before humans are cloned, scientists would have to know much more about the technique's safety and long-term consequences.
Some question the impact on society if, for example, a woman could give birth to her own identical twin.
"Is it possible with humans? Perhaps," Dr. Zirkin said. "But I'm not sure this speaks to that. Different species are just very very different. And the ethical issues on whether it should be tried remain exactly the same. Until those issues are appropriately debated and discussed, it would be a mistake to think in those terms."
But Dr. Lee Silver, a molecular biologist at Princeton University, said he already knows of two qualified fertility specialists who want to clone humans. And so, he says, "anyone who thinks that things will move slowly is being very naïve."
nytimes.com
Dave Clone1 |
