Baton
Rouge, LA (4/29/99)- The successful cloning of transgenic goats from somatic
cells may soon clear the way for herds of cloned animals producing valuable
human proteins in their milk.
left- three
identical goat clones
A collaboration among researchers in industry and academia cloned three healthy
female transgenic goats. First, fetal fibroblast cells were obtained from
a 30-day old female goat fetus. Next, the researchers attached a bioengineered
human gene for the production of an anti-clotting protein to a promoter gene
and then injected this into the nucleus of the newly fertilized egg. In some
cases the human gene was incorporated into the DNA of the goat embryo.
After removing the nucleus of recipient egg cells, the researchers activated
and fused the donor eggs with the fetal fibroblast cells now containing the
human gene. The cloned embryo was then transferred into a recipient female
goat "mother" that carries the clone to term. Female progeny will
produce milk containing the human protein, which can be extracted from the
milk for use in medical treatments. Moreover, half of the female offspring
produced by subsequent generations of the clones will also produce the human
protein.
"The technology used to clone the three goats is one of the first applications
of the nuclear transfer cloning procedure to produce transgenic goats for
the pharmaceutical industry", said Richard Denniston, a researcher with
the Louisiana State University Agricultural Center.
The bioengineered goats carry a human gene called AT III. The gene produces
a protein that helps keep the blood from clotting. The protein is being investigated
as a potential treatment for victims of heart attack and stroke. In this study,
the three transgenic female goats did produce the AT III protein in their
milk. It is possible that this might be the first therapeutic agent derived
from transgenic animals to be approved by the FDA.
"The market for AT III is $200 million. That amount of protein can be produced
by fewer than 100 goats. Even with the cost being a half to $1 million per
animal, the potential earnings from the pharmaceutical product are enormous,"
Dr. Denniston said.
While researchers are also investigating the possibility of developing transgenic
cows to produce human proteins, goats offer some important advantages. First
of all, it is cheaper to produce transgenic goats than cows. Second, the goat's
gestation period is shorter (5 months to a cow's 9 months), he added.
"The results could revolutionize the biopharmaceutical industry. We now have
a method that is a faster, reliable and more cost-effective way to produce
complex pharmaceuticals for humans and animals," noted Eric Overstrom, a developmental
biologist at the Tufts University Veterinary School who collaborated in the
study.
The research appears in the May 1, 1999 issue of Nature Biotechnology.
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