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Scientists Find Problems with Cloning Process - 2002-02-19

The latest study of cloning shows that genetically copied mice appear to be less healthy than normal mice.

In a paper published in the March issue of Nature Genetics, Japanese researchers describe how they cloned 12 mice and compared their health to that of six mice that were normally conceived. The researchers also included in the comparison group seven mice that were created by having sperm DNA injected into eggs.

The average life span of mice is 800 days, but the cloned mice started dying around 311 days. When investigators examined the cloned mice, they found that most had died of pneumonia and liver disease. One had died of lung cancer and another leukemia.

Only three of the 13 comparison mice died prematurely.

Tony Perry is a molecular embryologist with Advanced Cell Technology in Worchester, Massachusetts and says the study's results are exciting.

"It gives us great insight into some of the anomalies that are associated with cloning," he said. "And so far, there has been only one of these anomalies that have been identified in the mouse; and that is that they tend to get fat. And people are studying this effect and it is a very interesting effect. And now this group from Japan, who are an extremely technically accomplished group, have shown that there might be something wrong with the immunity and the liver function of these cloned mice as well."

Rudolph Jaenisch also thinks the Japanese study is good, but for a different reason. Dr. Jaenish, who heads the Whitehead Institute for Biomedical Research in Boston, Massachusetts, has been a vocal critic of researchers who want to clone humans

"I think we can predict with great certainty that cloned humans will have the same problems as cloned animals. There is no reason to assume otherwise," Mr. Jaenisch says. "So, this has just again confirmed my conviction that such an experiment should not be done with humans, not at all. And if people attempt to do this, they are ignoring all the scientific evidence."

Most scientists and politicians, including Professor Jaenisch, support so-called therapeutic cloning, with an eye toward creating stem cells that can be used to help cure disease. Stem cells are master cells that can be trained to grow into any cell in the body.

Advanced Cell Technology's Tony Perry believes one reason clones may develop abnormalities is because of the way they are made.

To create clones, scientists use extremely fine needles to insert the genetic material of a donor cell into a hollowed out egg. They also add to the mixture chemicals to start the egg developing, and about one or two percent result in cloned animals.

"Well, all of this jiggery-pokery that goes on with the egg at the beginning of this process probably generates a certain amount of trauma to it," Dr. Perry said. "Well, it certainly does because on a cellular scale, while the needles we using are very, very fine and very small, on a cellular scale they are relatively enormous. And they probably do cause some damage."

Dr. Perry believes in time, researchers will uncover and work out problems with cloning, and it will become a therapeutic as well as reproductive option.