Vicki
Croke, The Boston Globe
BOSTON -- Three unnamed dairy goats born last year on a farm in
Charlton, Mass., became the latest symbol Monday in the worldwide
scramble to produce better, cheaper pharmaceuticals by cloning
animals.
The
goats are exact genetic copies of a goat whose DNA was altered
to produce milk laced with an anti-clotting protein that could
be used to treat heart attack and stroke victims, scientists said.
Researchers
from Tufts University School of Veterinary Medicine and Genzyme
Transgenics Corporation, who announced the cloning Monday, said
their experiment also proved that more efficient methods of cloning
could be achieved, significantly reducing the number of eggs needed
to successfully produce one cloned animal. The method could mean
that complex biopharmaceutical drugs can be produced less expensively
and at a much faster rate than traditional manufacturing methods.
The
work is being reported in the May 1 issue of the journal Nature
Biotechnology.
``The
technology is here,'' says Mark Westhusin, an animal scientist
at Texas A&M University. ``Every one of these breakthroughs brings
the goals closer to reality. It may not be all that efficient,
but it's getting closer.''
The
world's first cloned goats are part of a growing menagerie of
genetically created animals that began when Scottish scientists
announced they had cloned the first sheep in 1996, named Dolly.
Since then the methods and practical benefits of cloning animals
has progressed at sonic speeds.
Last year, three calves were born with genetically engineered
traits, a breakthrough for scientists from the University of Massachusetts.
In that case, researchers inserted two genes into the donor cell's
nucleus, and then inserted the material into the cow egg. The
genes were markers, which scientists could detect after birth
to show the experiment was successful.
In this latest Tufts/Genzyme work, the marker was the gene for
producing Antithrombin III (ATIII), a protein found naturally
in human plasma which regulates blood clotting. The substance
is currently undergoing government clinical trials as a treatment
for strokes and heart attacks.
One
of the three goats was produced using earlier-developed methods
that required 140 eggs to produce one cloned goat.animal. But
the Massachusetts scientists said using new techniques they developed
92 eggs yielded two live offspring.
Dr.
Eric W. Overstrom, a developmental biologist at Tufts, says one
of the benefits of cloning is that the results are known immediately
in the lab. Using standard non-cloning methods to produce transgenic
farm animals, there's less control, and scientists don't see the
results of their labor, until after the mother animal has given
birth. And if the point of all this engineering is to quickly
and efficiently produce a special protein in milk, it's the females
you're after. With cloning, you can get all females.
James
Serpell, a professor at the School of Veterinary Medicine at the
University of Pennsylvania, sees no problem from an animal welfare
prospective. Because they are so valuable, the research animals
are typically well cared for and the environmental impact in this
case, he said, is minimal.
``Might
it unleash something nasty on the world?'' he said. ``In the case
of these goats, the product is taken in a relatively noninvasive
way -- the animals are milked.''
And
they may be milked for quite a lot. Sandra Nusinoff Lehrman, president
and CEO of Genzyme Transgenics estimates that the annual European
market for ATIII, which uses the protein in wider applications
currently than the United States, is worth $200 million.
Beyond
that, the cloning of transgenic animals could lead to the production
of a variety of protein therapies for a wide array of illnesses,
including arthritis and cancer. And, as may be the case of ATIII,
the farm produced version could be safer from viruses than that
harvested from human plasma.
Many complex proteins, Lehrman says, simply cannot be produced
synthetically.
``Layering
the cloning on top of the transgenics work is important in getting
the therapeutic proteins to the patients in the most efficient
manner possible,''' she said.
Westhusin
agrees. He said being able to use cloning techniques in transgenics
is infinitely more precise and therefore efficient.
``Whenever people in the field are successful,'' hesaid, ``it
makes it easier for the rest of us to get funding.''
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