Clones face uncertain future. (Biology).

For every step forward cloning makes, two steps backward seem to follow.

In the Feb. 21 Nature, researchers at Texas A&M University in College Station announced that they had cloned a cat, producing a seemingly healthy kitten they named Cc for Carbon copy. This first cloning of a common domestic pet was funded primarily by a man who wants the researchers to clone his dead pet dog, Missy.

Two new studies raise questions about Cc's future, however. In the March Nature Medicine, investigators from the University of Cincinnati College of Medicine report that their cloned mice regularly develop obesity. Even more disturbing, scientists at the National Institute for Infectious Diseases in Tokyo report in the March Nature Genetics that cloned animals may have a shorter-than-normal lifespan. In one of the experiments, 10 of 12 cloned mice died within 800 days of birth, whereas only 1 of 7 mice produced through natural mating died within that span.

The researchers conducted autopsies on six of the cloned mice and found that four had liver damage. All six had severe pneumonia, suggesting that their immune systems were weaker than those of normal mice.

It's unclear whether these problems are facts of life for cloned creatures, side effects of the procedures used to do cloning, or downsides specific to rodent clones, say the researchers. Nevertheless, the studies add to the debate about whether any cloned animal can be normal and healthy, an argument with great relevance to the issue of human cloning (SN: 10/20/01, p. 250).--J.T.