Human cloning will never be safe

By Steve Connor, Science Editor, Independent, UK
06 July 2001

Scientists have found potentially definitive evidence that cloning is
far too unsafe to be used in human reproduction, should it ever be
viewed as ethically acceptable in the future.

Hidden genetic defects were found in otherwise healthy cloned animals in
a study that could fatally undermine the arguments for loosening
controls on the most controversial area of reproductive technology.

The research could explain why a huge proportion of cloned animals are
either stillborn or suffer from congenital defects, and points to the
presence of an underlying genetic flaw in all clones. Professor Ian
Wilmut, the British scientist who cloned Dolly the sheep, said last
night that the research represented a serious blow to people such as
Sevorino Antinori, the Italian doctor who has said that he wants to
clone a baby.

"It surely adds yet more evidence that there should be a moratorium
against copying people. How can anybody take the risk of cloning a baby
when the outcome is unpredictable?" Professor Wilmut said.

The study was done by scientists drawn from two leading laboratories in
America. They found that cloned mice that were healthy in all outward
respects carried a high "burden" of genetic abnormalities, which could
shorten their lives.

The cloning process has also been shown to cause a higher-than-normal
incidence of birth defects. Other lambs cloned with Dolly, for example,
either died in the womb or were born with serious imperfections.

Now, a team led by Rudolf Jaenisch of the Whitehead Institute for
Biomedical Research in Cambridge, Massachusetts, has found that healthy,
cloned mice possess a hidden "instability" of their genes, which is not
present in normal mice. The instability causes some genes to work, or to
be "expressed", at abnormal levels, probably as a result of the cloning
process bypassing the normal way that chromosomes from two parents work
together when a sexually produced embryo is created by the fusion of
sperm and egg.

Despite this instability, many of the cloned embryos survived to
adulthood suggesting that mice and other mammals - including humans -
are surprisingly tolerant of such genetic aberrations.

"This suggests that even apparently normal clones may have subtle
aberrations of gene expression that are not easily detected in the
cloned animal," Professor Jaenisch said.

The study, published in the journal Science, suggests that reproductive
cloning causes unavoidable fundamental flaws, a finding that has
surprised the researchers themselves, who included Ryuzo Yanagimachi of
the University of Hawaii, the first person to clone adult mice.

David Humpherys, a member of the research team, said that by tagging
certain genes, the scientists found that cloning appeared to upset a
phenomenon known as "genomic imprinting", where the genes on the
chromosomes from one of the parents are switched on or off.

"The big concern is that there would be some underlying problem that you
can't see at birth or that there are other problems you can't even
assess in mice, such as cognitive problems," Mr Humpherys said. "It
seems very unwise to attempt this sort of cloning on humans."

Dr Yanagimachi was hailed in 1998 when he led a team of American,
Japanese, Italian and British scientists who succeeded in producing a
colony of 22 cloned mice.

The achievement, which some scientists believed was a biological
impossibility, was expected to lead to new cancer therapies,
improvements in agriculture and in the production of pharmaceutical
drugs.