AP News -- Single Gene May Deter Cloning.
May 19, 2002
Single Gene May Deter Cloning
By THE ASSOCIATED PRESS
Filed at 12:02 p.m. ET
Scientists say they've identified a single misbehaving gene that could explain most failures to clone
mammals. The work supports the popular theory that failures happen when genes aren't reprogrammed to
produce a new individual.
Cloning involves taking DNA from a cell of an adult animal and putting it into an unfertilized egg. So the
DNA must switch gears, from directing the activities of whatever adult cell it came from to telling the egg
how to divide and grow into a new individual. The switchover requires shutting some genes off and turning
others on; and the genes must go to work to the right degree at the right place at the right time.
Many scientists believe that such reprogramming often fails to occur adequately in cloning attempts, and
they blame that for the fact that only about 1 percent or so of manipulated eggs lead to a live animal.
The new work, done in mouse embryos, suggests that a particular gene crucial for early development is
usually not reprogrammed properly. That makes its level of activity inappropriate, dooming the cloning
attempt, researchers say.
The problem with this ``Oct4'' gene doesn't explain every failure, but it could account for about 90 percent,
said researcher Hans Schoeler of the University of Pennsylvania's veterinary school in Kennet Square, Pa.
Even if other genes in an affected embryo are misbehaving as well, due to faulty reprogramming, the Oct4
gene is so crucial that its misbehavior alone is enough to cause failure, he said.
In other embryos where Oct4 is working fine, the failure to reprogram some other gene might lead to
failure, he said.
Schoeler and colleagues present their work in the May 15 issue of the journal Genes and Development. Only
about 10 percent of the early mouse embryos they studied showed proper activity of Oct4. And aberrant
activity of Oct4 was correlated with an embryo's inability to develop normally.
Peter Mombaerts, who studies mouse cloning at The Rockefeller University in New York, was skeptical.
The results do show that a mouse embryo's fate is related to activity of its Oct4 gene, he said, but that
correlation doesn't prove the Oct4 gene caused failures.
Many genes are active in that early stage of development, he said, and it's not clear that Oct4 alone is the
key.
Copyright 2002 The Associated Press |
