From the Department of Dairy and Animal Science
This regular column from Penn State’s Department of Dairy and
Animal Science features the research findings, student opportunities, and
resports on other important topics generated in the Department. The
back issues of the column are archived on Lancaster Farming’s
Internet www.lancasterfarming.com home page. Look for them.
Genetic Engineering -
From Mice To Cows?
Cindy McKinney and
Cooduvalli ShashUcant
Department of Dairy and
Animal Science, Penn State
University
- Twenty-five years ago, genetic
engineering merely served as
fodder for science fiction writers.
However, as we now enter the 21“
century, genetic engineering is
poised to make a substantial
impact on our lives, food supply,
and medicines.
The roots of genetic
engineering can be traced to the
late 19705, when methods to
manipulate the genetic material,
DNA, became available.
Mutations (or changes) in DNA
sequences can cause the
formation of abnormal proteins,
which lack normal activities and
may lead to disease. Genetic
engineering techniques allow us
to identify the mutations
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responsible for human and animal
diseases. These methods provide
a powerful means of studying the
genetic makeup of animals.
Genetic Engineering of Mice:
It is now possible to
genetically engineer mice - that
is, add or remove fragments of
DNA by manipulating embryonic
stages of the mouse. These
techniques allow researchers to
use mice to develop models of
human and animal diseases.
Researchers already are using
genetically engineered mice to
study defects in human DNA
which might lead to cancer, Type-
II diabetes, or mental illness.
Since 1990, researchers have
produced literally hundreds of
mouse disease models to enhance
researchers’ abilities to
understand how inherited diseases
develop.
Genetic Engineering from
Mice to Livestock
For many years scientists have
been interested in the
phenomenon, double muscling.
This trait, observed in cattle, is
associated with a dramatic
increase m muscle mass.
Researchers at Johns Hopkins
University identified a DNA
mutation in the gene thought to be
responsible. When this mutated
gene was introduced into mice
they also displayed the "double
muscling" phenotype observed in
Piedmontese cattle. This suggests
that mice and livestock share
common biological functions, and
that mice can be used as models
for larger animals. As a result,
agricultural scientists are
exploring the feasibility of
genetically engineering livestock
species for specific purposes.
A number of studies already
conducted in sheep, goats, pigs
and cows have introduced
individual genes into these
species that lead to the production
of proteins not otherwise found in
milk. These proteins are isolated
from milk and used for a variety
of clinical uses in human
medicine. This emerging field of
gene "pharming,” in which the
regulatory fragments of genes that
direct the production of proteins
normally found in milk are tested
with hybrid genes in mice, pigs,
and cows. Pharmaceutical
companies are particularly
interested in these studies because
it may afford the opportunity to
produce therapeutic proteins like
erythropoietin for kidney dialysis
patients. If selected proteins can
be produced and subsequently
isolated from milk without
destroying then natural activity, a
variety of expensive drugs may
become more widely available by
using “engineered” livestock.
An advantage of genetically
engineered livestock is that they
are renewable'by breeding, can
provide large quantities of milk as
starting material, and can be
maintained on farms with the
same technology used for current
animals. Pilot studies using farm
animals as "bioreactors" are being
conducted at a few universities
and “biotech” companies; Penn
State is presently not conducting
any of these studies.
While the future of genetically
engineering in animal agriculture
is promising, further research is
needed. First, the technology
must advance significantly before
it will be cost effective to produce
genetically engineered livestock.
The first reports of cloning
(manipulating DNA outside the
animal and exchanging an
engineered nucleus for a non
engineered nucleus) may be a
significant step forward.
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However, the success ratio in
these experiments is very low and
requires further improvements.
Second, are engineered
products superior to naturally
produced products? Will they be
cost effective? Further, can the
byproducts of this manufacturing
process be utilized elsewhere?
This requires a good cost/benefit
ratio to be profitable.
Finally, are genetically
engineered products safe as well
as therapeutic? The evidence to
date indicates that biotechnology
and genetic engineering are safe,
however, any new product needs
to be rigorously evaluated.
The Department of Dairy and
Animal Science at Penn State’s
University Park campus has
created “The Mouse Farm,” a
genetic engineering program
involving mice. We believe that
genetic engineering studies of
prototype DNA molecules in mice
can be translated to larger animal
species. However, these advances
will depend on the availability of
more information from genome
databases for livestock, the
continued refinement of genetic
methods, and more cost-effective
production.
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