Humans 'nearly impossible' to clone: study
 
Margaret Munro
National Post
Friday, April 11, 2003

It may be impossible to clone human beings with existing technology
because of insurmountable molecular obstacles, a group of U.S.
researchers said yesterday.

"The chromosomes do not split properly," said Dr. Gerald Schatten,
head of the research team at the University of Pittsburgh School of
Medicine. "From the very first cell division, development is
inappropriate in vital ways."

Current techniques, which have been used to create a barnyard of
cloned animals including Dolly the sheep, cows and goats, do not seem
to work in primates, the team reports in the journal Science today.

Dr. Schatten said it is almost as if someone drew a sharp line
between primates and other animals, saying: "I'll let you clone
cattle, mice, sheep, even rabbits and cats, but monkeys and people
require something more."

Still, Dr. Schatten and other researchers are unwilling to write off
primate cloning forever. "Given enough time and materials, we may
discover how to make it work," Dr. Schatten said. "It just doesn't
work now."

In December, Clonaid, a company founded by the Raelian religious
sect, which believes space aliens created life on Earth, claimed to
have produced the first human clone -- a 3.2-kilogram baby girl. The
sect claims to have cloned several more babies, but has yet to
provide proof.

Scientists and ethicists around the world reacted to the Raelian
announcement with disbelief and horror. Even when cloning works, the
animals are often plagued with medical problems. Dolly the sheep, the
first cloned animal created in 1996, developed arthritis and died
prematurely in February. For every cloned animal that is born, many
more are stillborn or have severe defects.

The experiments in Pittsburgh show the obstacles to human cloning are
huge. Not one of the 716 eggs from rhesus macaques, which the
scientists tried to clone using state-of-the-art technology, produced
a baby monkey. Few of the clones even developed to the 16-cell stage.

"Our study suggests that reproductive cloning in primates -- human
and non-human alike -- is going to be nearly impossible with current
technologies," the Pittsburgh team said. The failure "demonstrates
that neither the cloning process used to produce Dolly nor cloned
mice work with a primate."

The monkey failure is also seen as a setback for so-called
"therapeutic" cloning, which many researchers dream of using to grow
replacement parts and cells to treat diseases such as diabetes and
Parkinson's disease. Therapeutic cloning would involve transferring
new genetic material into human eggs. The resulting cloned embryo
would not be used to produce a child but rather to produce cells and
tissues that could be harvested.

For therapeutic cloning to work, the cloned embryos must get through
several cell divisions before the desired cells can be harvested -- a
feat the monkey work indicates is going to be more difficult than
expected.

"This is complex biology, and just moving nuclei [which contain a
cell's genetic material] around is not as simple as some people might
suggest," said Dr. Alan Bernstein, president of the Canadian
Institutes of Health Research.

One cloning technique was reported to have produced a healthy cloned
monkey a few years ago. No one has ever been able to repeat the
experiment.

The Pittsburgh team attempted to clone the monkeys using somatic cell
nuclear transfer -- the technique used to clone sheep, goats, cows,
pigs, mice, rabbits and Cc the cloned cat. The scientists harvested
an unfertilized egg, pulled out its DNA genetic material and replaced
it with new DNA from an adult cell of the animal to be cloned. The
egg was then coaxed to grow using various stimulants.

Although 33 embryos were transferred into surrogate mothers after
initial cell division, no pregnancies were established. Although cell
division continued in a superficially normal manner, the scientists
found there were chromosomal problems within each individual cell.

The Pittsburgh work indicates the hurdles to cloning primates begin
the moment the cloned egg cell tries to divide and multiply. Dr.
Christopher Navara, a member of the Pittsburgh team, said motor
proteins that organize and move chromosomes around during cell
division seem to be compromised or damaged when the DNA is pulled
from the monkey eggs. "Sometimes they [the eggs] didn't even make it
out of the first cell cycle; they'd just stop right there," Dr.
Navara said. A few clones got to the 16-cell stage. "But we didn't
see any past that," he said, all of which indicates that no one will
be cloning humans any time soon.

"Reproductive cloning is nowhere near as simple as the Raelians would
have you believe," said Dr. Alan Leshner, chief executive officer of
the American Association for the Advancement of Science.

The association, and most scientists and ethicists, would like to see
a ban on cloning of humans, or so-called reproductive cloning. As Dr.
Navara puts it: "Everything we know about cloning in other animals
suggests that human cloning is not safe, is not ethical and probably
should be illegal."

But many scientists believe human therapeutic cloning could have huge
medical benefit and should not be ruled out completely.

"There are clinical reasons for wanting to do it," Dr. Bernstein
said. In order for researchers to be able to explore the potential of
therapeutic cloning, they must be allowed to work with cells taken
from human embryos. "There are some important experiments that we
could and should be doing," Dr. Bernstein said.

His agency, a main funder of Canadian university medical research, is
keen to start funding work in the area but has been waiting more than
a year for the federal government to pass legislation to spell out
how human embryos can be used.

Bill C-13, which was introduced last May, would make both human
reproductive and therapeutic cloning illegal, along with attempted
human-animal hybrids. The bill would also ban the creation of embryos
for the purpose of research. It would, however, permit the use of
surplus embryos for medical research until 14 days after conception.
Canadian researchers have expressed interest in producing cells for
research from the embryos.

"It is important to get clarity," said Dr. Bernstein, who had hoped
the legislation would pass before April 1.

"There are a number of people at the starting line waiting to get
going and patient groups who are very anxious to see that the work
move forward," he said.

Meanwhile, in Pittsburgh, the monkey cloners, though frustrated, are
exploring ways to get around the hurdles nature seems to have placed
in their way.

Dr. Navara said they still hope to clone monkeys that could be used
to test new disease treatments -- among them, therapeutic cloning.

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SOURCE: The National Post, Canada
http://www.canada.com/technology/story.html?id=15682AB5-F50E-4018-
B3CD-CCEB5D76FE35

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