Is Cloning Here to Stay?
By Deb Ottier
Iron Horse Equine
Printed Canadian Horse Journal Mar/Apr 2007
Introduction
Somatic-cell nuclear transfer or genetic cloning seems like a sci-fi adventure, yet,
there are several clones now on the ground from some of the horse industries
top horses. The first cloning experiment involved a tadpole in 1952, with 1997
marking the birth of Dolly, the world renowned sheep clone. There is growing
demand for this technology by the horse industry, but should we be dwelling on
the past, or be preparing for the future?
The Technique and its Success
The actual technique, called somatic cell
nuclear transfer, involves the microinjection of a
DNA construct obtained from donor animals
into an oocyte and transferred into recipients.
Sounds like a mouthful, so put into simpler
terms a piece of DNA from the donor animal is
injected into an egg and transferred into
carriers or hosts to carry the embryo to birth.
This technology would produce a baby, not an
adult that we see in some sci-fi movies.
Figure 1 – Schematic representation of
somatic cell nuclear transfer adapted
from Vanderwall et al., 2004
This technology is expensive, inefficient and
impractical at this time, but some are willing to
pay the price to produce another “Big Ben”.
The estimated cost to produce one clone is
$150,000, with a second clone costing
approximately $90,000.
Looking at the success in clones currently in
research news we have Dolly, the sheep that was the first clone, ever, well she
was 1 out of 258 tries; the first mule that was cloned by the combined research
teams from the Northwest Equine Reproduction Laboratory (University of Idaho)
and Utah State University, was 1 out of 334 tries. In May of 2003, Researchers
from the Laboratory of Reproductive Technology, a nonprofit research
organization in Cremona, Italy, have produced a live foal cloned from skin cells
from its own dam – which would mean the mare gave birth to herself. This was 1
out of 800 tries.
What is Mitochondrial DNA?
The mitochondria is the powerhouse of the cell responsible for supplying energy
at the cellular level. Mitochondrial DNA is genetic information stored in the
mitochondria. When the genetic information is removed from the egg during
nuclear transfer, the mitochondrial DNA is left intact in the egg and hence, the
final clone embryo. How does this impact the clones? This has not been eluded
to in any of the research thus far, yet cloning utilizes eggs from a donor female.
Could this potentially alter something in our clones?
The Racing Mules
The production of the first equid to be cloned, a mule, involved the nuclear
transfer of DNA from a 45 day old mule fetus into an egg from a quarter horse
mare. This first mule was born in May of 2003, with a second to follow that same
year. While the technology is still relatively new, there are 2 mules that are now
of racing age. Both mules raced against one another in June of 2006, and one
would have expected there to be a dead heat, but that was not the case. Both
mules were trained by different trainers with the outcome of the race being one
mule coming in third, while the second clone came in seventh.
Nature Vs. Nuture?
While this technology would produce an identical individual genetically, we do
have to consider that environment also has a strong influence of how the foal will
develop. Such factors as nutrition, upbringing and training will influence if that
individual will have the same performance rating. At a lecture by Dr. Ian Wilmut,
the Scottish researcher responsible for the cloning of Dolly, he was put to the
question of cloning a human, which is illegal, to obtain a child that had died in a
tragic accident. He stated the environment would be very much different, so
while you would have a genetically identical individual, you are older and have
the experience of the first child and would do things differently in the upbringing
of the child. Will this come into play in the horse world? Well, many European
breeders will not utilize the technique of embryo transfer as they believe the
mother plays a significant role in producing a champion based upon how she will
raise the foal. It will be the all mighty dollar that will dictate the horses that are
cloned, as with most technology.
Geldings to Breed
Ever wished you had not gelded that awesome performance gelding? Now the
technology is available to produce the same gelding, only this time keep him
intact. The primary obstacle will be in breed registry restrictions, as there will be
genetically identical animals in the breeding books, which will make DNA marking
very difficult.
A gelding named “Gills Bay Boy” or Scamper won the hearts of many in years
following 1985, as he and his rider, Charmayne James, rode into World
Championship success for 8 consecutive years, making Scamper a world
renowned barrel racer in his time. This quarter horse gelding obviously
possesses superior genetics, but being a gelding, how could he pass on these
remarkable qualities? Well, this gelding was cloned and has produced a colt
which was introduced to the public as Clayton in November of 2006. This raises
a couple of questions. Why was Scamper gelded in the first place? Would he
have been the champion he was had he not been gelded?
The colt is now coming up to breeding age, and the next step, how to handle the
registration of foals from the clone.
The American Quarter Horse Association rule 227 specifically states:
“227. HORSES NOT ELIGIBLE FOR REGISTRATION
(a)Horses produced by any cloning process are not eligible for
registration. Cloning is defined as any method by which the genetic
material of an unfertilized egg or an embryo is removed, replaced by
genetic material taken from another organism, added to with genetic
material from another organism, or otherwise modified by any means
in order to produce a live foal.”
So the big question, will this clone be able to provide its genetics to the gene pool
of the Quarter Horse? That will be decided by the association and whether or not
it intends to be a pro-active force in labeling cloned animals. Once they begin
breeding, it will be very difficult to identify which came first, the chicken or the egg
or in this case the clone or its 2nd clone…
What the Future Holds
With the current status on disease control, we are still seeing the emergence of
new viruses and new problems, West Nile Virus, Avian Bird Flu, to name a few.
By narrowing the gene pool with producing offspring that are genetically identical,
how are we producing animals that will be able to resist these biological threats?
Will the strong really survive?
If breed registries take a pro-active role in the application of this technology by
incorporating cloned animals in their registry, we will see more clones in the
years to come. Although the equine industry is behind in applying the
tremendous advances in reproduction already made in other species, the time
will eventually come when a catalogue of banked genetic material will be
available for breeders to choose their next crop of potential equine athletes. But
is this the direction the horse industry should be taking or should the horse
industry be trying to improve on the genetics we already have.
References
Ball BA. (2000) What Can we Expect for the Future in Stallion Reproduction? In:
Recent Advances in Equine Reproduction, B. A. Ball, Ed.
Ball BA. (2000) Reduced Reproductive Efficiency in the Aged Mare: Role of
Early Embryonic Loss. In: Recent Advances in Equine Reproduction, B. A. Ball,
Ed
Vanderwall DK. (2000) Current Equine Embryo Transfer Techniques.
In: Recent Advances in Equine Reproduction, Ball B.A. (Ed.) International
Veterinary Information Service, Ithaca NY, 2000
Vanderwall DK, Woods GL, Sellon DC, Tester DF, Schlafer DH, White KL.
(2004) Present status of equine cloning and clinical characterization of
embryonic, fetal, and neonatal development of three cloned mules.
J Am Vet Med Assoc. Dec 1;225(11):1694-9.
Woods GL, White KL, Vanderwall DK, Li GP, Aston KI, Bunch TD, Meerdo LN,
Pate BJ. A mule cloned from fetal cells by nuclear transfer.
Science. 2003 Aug 22;301(5636):1063. Epub 2003 May 29