Cloned Mice Show No Premature Aging

Wednesday, September 20th 2000, 12:00 am
By: News On 6

The cells of cloned mice show no signs of premature aging despite being copied through six generations, according to a new study. In fact, some of the cells showed signs of getting younger.

The study published in Thursday's issue of the journal Nature contradicts a 1999 study of Dolly the cloned sheep that showed the protective tips of her chromosomes, known as telomeres, were showing signs of early wear and tear because they were copied from genetic material that was 6 years old.

Many questions surround how telomeres behave in the cells of cloned animals. Not only might cloned animals die prematurely, but healthy cloned cells created as medical treatments might die off before they can fight disease.

Cells can divide a certain number of times before they die — about 70 times for humans and fewer for other mammals. Every time a cell divides, the telomere is whittled down, but the genetic material remains intact. Eventually the telomere is too short to protect the genes and the cell soon dies.

The mouse study conducted at the University of Hawaii and Rockefeller University in New York cloned six successive generations of mice in a row. Researchers said the telomeres of some mice were longer than expected, even in mice that lived for more than one year.

``Our results verify that telomere shortening is not a necessary outcome of the cloning process,'' said the study's lead researcher, Teruhiko Wakayama.

Wakayama said he could not explain why the cloned mice had long telomeres.