Cloned Animals Meet Early Deaths
by
Philip Cohen

February 10, 2002 (New Scientist) - Cloned animals may indeed die young suggests the first direct study of their lifespan, carried out by Japanese researchers on mice. Cloning involves removing the nucleus from an egg and replacing it with the nucleus of a donor cell. Many of these "nuclear transfer" embryos never develop or miscarry. Even after birth some clones die. But many cloning scientists argue that the few survivors can be perfectly normal.

Atsuo Ogura of the National Institute of Infectious Diseases in Tokyo says his team's work suggests that some effects of cloning are not apparent in the days, weeks, or even years after birth. "It is very probable that, at least for some populations of clones, some unpredictable defects will appear in the long run," he says.

The debate over the health of clones and how they age has swung one way and then the other. In November 2001, US biotech company Advanced Cell Technology reported the cloning of two dozen apparently healthy cloned cows. But in January, the first mammal cloned from an adult cell, Dolly the sheep, was reported to have prematurely developed arthritis.

Dr. Rudolf Jaenisch, a mouse cloner at MIT says the new work "shows that to look at animals at one point in time and say they are healthy and normal is really wishful thinking."

Immune System Defect

Ogura's team cloned 12 male mice and these were compared with seven males from natural matings and six others produced using In Vitro Fertilization. The clones appeared active and healthy, gained weight normally and matched the control animals in 14 of 16 physiological measurements.

But the first cloned animal died after only 311 days and, by day 800, 10 (83%) of the animals were dead. In contrast, only three (23%) of the controls died during the same period. The dead clones showed high rates of pneumonia, liver disease, cancer, and a lower level of antibody production, suggesting they had an immune system defect. Ogura's team is now trying to pinpoint the precise cause of death and repeat the experiment with more animals.

ACT's Tony Perry points out that it remains unclear if clones from other species such as cows or pigs die early. And even if clones in general do prove to have a shortened lifespan, he does not think that undermines data from ACT and others that clones can be healthy. All the researchers agree that "the work should be an additional warning to would-be human cloners."

Nature Genetics 1038/ng841 (February 10, 2002).