Researchers clone genetically engineered cows
January 20, 1998
In this story: PARKINSON'S, ALZHEIMER'S TREATMENT?
'Pharming' -- drugs from farm animals
Variation on sheep-cloning method
Drug potential of cloned sheep milk to be tested
BOSTON (AP) -- Researchers said Tuesday they have successfully created two
identical, genetically engineered calves, a step that could lead to the mass
production of drugs for humans in cows' milk.
Named George and Charlie, the calves were created through a combination of
cloning and genetic engineering by Dr. James Robl at the University of
Massachusetts and Dr. Steven Stice of Advanced Cell Technology Inc.
The two scientists reported their findings at the International Embryo
Transfer Society meeting in Boston.
PARKINSON'S, ALZHEIMER'S TREATMENT? -
The calves were born last week at a ranch in Texas. They contain two genetic
alterations -- a "marker" gene and one that made cells resistant to an
antibiotic. Those markers have shown up everywhere, from the blood to the spleen
to the bones.
Another researcher on the project, Jose Bernardo Cibelli, said the team's
technique takes cells that have already differentiated to produce a specific
type of tissue -- muscle, for example -- and brings them back to the state
where they can divide and form every type of cell in the body.
Robl and Stice say that process could lead to the ability to produce cells
that can be transferred into humans to treat such diseases at Parkinson's
and Alzheimer's.
"The cells that we use are very easy to program, very easy to genetically
alter," Robl said. Molly and Polly differ from Dolly in that they were
cloned from the cell of a sheep fetus, not an adult animal.
'Pharming' -- drugs from farm animals -
The calves aren't the first animal clones with altered genes -- lambs Molly
and Polly have a human gene expected to make them produce a protein helpful
in blood clotting.
But even Dr. Ian Wilmut, the Scottish researcher who genetically engineered
the lambs and the now-famous Dolly, acknowledged that drug-making cows could
be more valuable because they produce much more milk than sheep.
Researchers said the cows mark the most viable step so far toward pharming"
-- developing pharmaceuticals using farm animals.
"It's a big deal," said Mark Westhusin, a researcher at Texas A&M
University. "This technology has the potential to be a lot more efficient
than the technology that we have now."
Variation on sheep-cloning method -
Robl said the technique his team used to clone the cows was a variation on
the nuclear transfer process Wilmut used last year to clone Dolly the sheep,
the first mammal cloned from an adult cell.
But Stice said unlike the method used with sheep, cloning the cows did not
require surgery and it was relatively quick.
In nuclear transfer, scientists remove the nucleus from an egg and replace
it with the nucleus from another cell. The egg is then placed into the
uterus of a surrogate mother that gives birth to an offspring that has only
the genes of the original cell. But the process can require at least two
surgeries. The University of Massachusetts researchers said the genetically
altered egg was grown in a laboratory, then inserted into the uterus without
major surgery.
Drug potential of milk to be tested -
The sheep were born in July and will be tested this spring to see if their
milk produces useful quantities of factor IX, a protein that helps blood
clot. It is hoped that the factor IX could be extracted from the milk and
used to treat patients with hemophilia, an inherited bleeding disorder in
which the blood lacks the ability to clot.
"Obviously I'm delighted that the nuclear transfer technology is very
robust," Wilmut said upon learning of the cloned calves.
The University of Massachusetts researchers haven't produced a cow that can
produce a drug. But they said they have pregnant cows carrying fetuses that
have been altered to produce milk with the human serum albumin, a protein
essential to the blood that is widely used by hospitals.
Advanced Cell Technology, the company founded by the researchers, already
has a deal with Genzyme Transgenics Corp. of Framingham, Massachusetts, to
produce albumin. "We've taken a significant step toward making this
commercially viable," Robl said. Neither the lambs nor the calves are
absolute pioneers.
Other techniques have been used to reap drugs for the treatment of cystic
fibrosis and heart attacks from the milk of genetically engineered sheep or
goats. These animals, however, were produced by injecting genes into a
fertilized egg and then implanting the egg in a surrogate mother, a
technique less efficient than cloning.
Only about 2 percent of such eggs grow to live animals and only a small
percentage of the survivors actually contain the target genes.
Scientists at the conference, many of whom are researching animal cloning,
said the arrival of George and Charlie has been much anticipated.
"It's not Dolly but it's a substantial contribution," said Dr. Caird
Rexroad, the society president. "We've all been awaiting more information on
what you can do with cattle. A cow can make a tremendous amount of protein."
Copyright 1998 The Associated Press. All rights reserved.
Judith Richards
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