[monkeywire] Scientists create first cloned embryo from primate
ugarte at rickblaine.com
ugarte at rickblaine.com
Wed Nov 14 10:52:23 EST 2007
Scientists create first cloned embryo from primate
http://news.yahoo.com/s/afp/20071114/sc_afp/healthbiotechcloningprimates
PARIS, Nov 14, 2007 (AFP) - Scientists said Wednesday they had created
the world's first cloned embryo from a monkey, in work that could spur
cloning of human cells for use in medical research.
In a paper published online by the British journal Nature, a team in
the US said they had created cloned embryos of rhesus macaques, using
the same method that famously led to Dolly the Sheep and other
genetically duplicated animals.
It is the first time that this technique has been successfully used to
create cloned primate embryos.
The group generated two lines of embryonic stemcells from the embryos,
according to the research headed by Shoukhrat Mitalipov of the Oregon
Health and Science University in Beaverton, Oregon.
Dolly, the world's first cloned animal, was created in 1996, by using
so-called somatic cell nuclear transfer (SCNT) in which the genetic
core of an egg is removed and replaced with the nucleus of an adult
cell.
The egg is then stimulated with chemicals or a jolt of electricity to
prompt its division.
The list of other cloned creatures using SCNT includes mice, pigs,
cats, cows and dogs.
Until now, though, there has been no cloned primate, for researchers
encountered obstacles that caused cell development to be
catastrophically flawed.
Work on primate cloning has also stirred controversy among ethicists,
who say it could open the door to cloning human beings, not just
cells. In an exceptional move, Nature said it moved forward the
release of the paper because of "continuing speculation" about the
research.
Researchers distinguish between "reproductive cloning" of humans, in
which a cloned baby would be born and "therapeutic cloning" in which
only cloned cells would be used for medical reasons and no baby would
result.
Helen Wallace of Genewatch UK, a British group that monitors cloning
and other activities in biotechnology, said the breakthrough announced
on Wednesday would cause "a real worry" in some quarters that it would
tempt a renegade scientist to create a cloned baby.
"The clear risk of an experiment [in human reproductive cloning] is of
a deformed baby and maternal suffering," she told AFP in a phone
interview.
"In Britain, we don't think that the technology is going to go that
far because there are laws against reproductive cloning," she said.
"However, in most countries around the world, there are no legal
safeguards."
Stemcells are immature cells that develop into the specific tissues of
the body.
Embryonic stemcells have the highest capability of all, because they
can differentiate into any tissue. Scientists hope to be able to coax
these cells into one day becoming replacement tissue for organs that
are damaged or diseased.
Transplanted cells from a donor, however, run the risk of being
attacked as intruders by the patient's immune system. By creating
stemcells that are programmed with the patient's own DNA the risk of
rejection would be skirted.
Mitalipov's team said they collected 304 eggs, also known as oocytes,
from 14 female rhesus macaques.
The donor nucleus came from skin cells taken from an adult male monkey
housed at the Oregon National Primate Research Center.
Thirty-five blastocysts, or early-stage embryos, resulted from the
SCNT operation. They in turn led to two lines of self-dividing
embryonic stemcells -- a success rate of 0.7 percent when compared to
the number of eggs used.
"Our results represent successful nuclear reprogramming of adult
somatic cells into pluripotent ES (embryonic stem) cells and
demonstrate proof-of-concept for therapeutic cloning in primates," the
paper said.
Wallace criticised what she said was the "very high failure rate" of
SCNT.
The technique has always needed large numbers of eggs to be harvested
in order to result in just a small number of cloned embryos. In
addition, many cloned animals are born with genetic defects and die
prematurely.
"We have concerns about the implications of using this technology
because the failure rate raises questions as to whether the suffering
in animals is justified," said Wallace.
The claim that the stemcells were an exact DNA copy of the donor
monkey's genetic code was validated independently by a team led by
David Cram of Monash University in Melbourne, Australia.
That confirmation comes on the heels of a scandal surrounding earlier
claims on cloning.
In 2004, South Korean scientist Hwang Woo-suk announced he had created
30 cloned human embryos from which he derived stemcells, but his data
turned out to be fake.
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