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A Sheep As
Trailblazer: On Ten Years Of Adult Somatic Cell Cloning
By Anette Breindl
BioWorld Today Science Editor
Dolly the Sheep turns ten this month. Or she would
anyway, if she hadn't been euthanized in 2003.
Dolly was many things. She was the first mammal cloned
from an adult somatic cell; she was the first celebrity
sheep — though certainly not the first celebrity —
with weight problems. Named after Dolly Parton because
she was cloned from an udder cell, she was probably also
the first indication to the general public that an
advanced degree is no protection against a juvenile
sense of humor.
Dolly was a mother many times over. None of her six
biological children was a clone — but her scientific
offspring are everywhere. In the ten years since Dolly
was born, cats and mice, cows and horses are just some
of the species who have joined the adult somatic cell
clone club.
Dolly received a lot of attention because as the first
mammal cloned from an adult somatic cell, she was proof
of principle that therapeutic cloning of human adult
somatic cells was possible. But human therapeutic
cloning has not advanced to anywhere near a practical
level. So for now, her most direct legacy is in animal
reproductive cloning — which is itself still a very
inefficient process, but is in practical use today.
Those practical uses are mainly in farm animal cloning,
though at least one company tried to make a living
cloning bereaved pet owners' loved ones.
It's hard to claim that Dolly, or cloning, represents a
fundamentally new philosophy of animal breeding. Humans
have been selecting animals for desired characteristics
since the iron age — witness the biblical accounts of
making flocks of spotted sheep and goats for the Hebrew
patriarch Jacob. And anyone who is concerned about
animal welfare can find plenty of purebred (read:
inbred) dogs whose health is poor enough to make you
weep.
Still, the recent decision by the FDA that animal clones
pose no health risk to consumers seems to miss the
health of the forest for looking at the health of the
trees.
For one thing, whether clones are on average healthy is
still a matter of debate. Whether Dolly was healthy is
not in question; she wasn't. Claims by some cloning
advocates that Dolly lived longer than most sheep are
true, but only because most sheep, like most farm
animals, don't live out their natural lifespan. At any
rate, she developed severe lung disease and was
euthanized at the age of six, which is about half the
maximal lifespan for a sheep. At that time she already
had a bad case of arthritis.
Dolly's health problems were not unique, and might have
been more related to her sedentary lifestyle than to her
being a clone. But cloned mice have a shorter average
lifespan than those made the old-fashioned way. No good
numbers exist on larger animals to date — they are
simply not old enough yet. It will be years before we
truly know.
Because farm animals do not live out their natural
lifespans, such problems in old age do not directly
affect the consumer — who would not be eating clones,
as opposed to their offspring or their dairy products,
anyway. But they do have implications for the general
quality of the animals who are one pillar of our food
supply.
Along the same lines, modern farm breeding is not a
love-in on the pasture, whether there's cloning involved
or not. But the diversity that breeding represents, even
as reduced as it is in modern agriculture, might well be
important for the overall health of the animal food
supply. Further reducing the genetic diversity of our
agricultural livestock through cloning carries potential
risks to the food supply.
The editors of The Economist, who are certainly not
anti-market granola types, pointed out last year that
some people make a rational decision to eat organic meat
or eggs without believing that they will derive personal
health benefits. They do so because it is literally hard
to stomach the way that animals are treated on factory
farms, and it is also hard to find non-organic meat or
eggs from animals raised humanely. Whether consumers
think the risk to the food supply that cloning may bring
is worth the benefits is an individual decision, and it
is something reasonable people can disagree on.
There is no new technology without risks, and especially
for an industry that touts the benefits of "educating"
the consumer via DTC drug advertising, here's an
information campaign waiting to happen. Cloning has
obvious benefits in terms of helping breed good
livestock, and perhaps even saving endangered species.
Spread the word! And who knows, perhaps such a campaign
would even have spillover benefits in terms of teaching
consumers about therapeutic and reproductive cloning,
genetics and epigenetics, or risk-benefit analysis.
Happy Birthday, Dolly! We hardly knew ye, but one thing
seems sure: we will have a long and interesting
relationship with your scientific progeny.
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