DNA sequence in hand, dog geneticists aim to build a better
By Emily Anthes
September 7, 2004
The ancient relationship between people and dogs can be characterized
as one long genetic experiment, one that began as soon as humans
started breeding dogs for their ability to herd, hunt, or protect.
But in another sense, the great canine experiment is just beginning.
This summer researchers at the Broad Institute in Cambridge unveiled
the map of the dog genome, sequencing the genes of a female boxer
named Tasha. About the same length as the human genome, the dog's DNA
adds to the growing library of organisms that have been sequenced --
the dog is the fourth mammal to have had its genome sequenced,
joining the human, mouse, and rat.
But for the small but growing community of dog geneticists, from
breeders to veterinary researchers, it marks a more significant
"This has been the biggest step forward for us in research," said Dr.
Gustavo Aguirre, a professor in the department of animal health at
Cornell University, who is working to develop genetic tests for
inherited eye diseases in dogs. "Having available the sequence will
shorten the search for genes and mutations incredibly."
The field of dog genetics has grown into a multimillion-dollar
research enterprise, using the new tools of genomics technology and
fueled by donations from the American Kennel Club and guide-dog
breeders. A $30 million grant funded the sequencing of the dog genome
-- and the real work, locating the genes that code for diseases, is
It took approximately $5 million to identify the gene for a common
blood clotting disorder in dogs, said John Duffendack, the president
of VetGen, a veterinary genetics company. Multiply that figure by the
approximately 400 inherited canine diseases researchers have
identified, and canine genetics looks like a potentially formidable
industry -- especially if researchers succeed in finding the genetic
roots of common health problems such as hip dysplasia, blindness, and
Breeders today have developed some technological screening techniques
to help them breed dogs with desirable health profiles, but breeding
still remains largely a trial-and-error system that would be familiar
to dog owners decades ago. If a breeder wants to eliminate a certain
trait, like epilepsy, from future litters of dogs, he or she must
remove the affected dog from the breeding population -- and then, to
be safe, remove its parents and littermates as well.
But once researchers can pinpoint which genes are connected to
epilepsy, breeders will be able to test their dogs for the genes, and
avoid breeding only the ones with the troublesome DNA.
The way selective breeding is done now narrows the gene pool,
potentially making other genetic diseases more common. Genetic
screening could help minimize this problem by keeping more dogs in
the breeding population.
"You don't have to eliminate the disease, you just have to breed dogs
selectively so that the disease just doesn't crop up," Aguirre said.
"You can maintain genetic diversity."
Schools that train guide dogs for the blind are particularly
interested in the implications of canine genomics. They hope the
sequencing of the genome and the identification of disease genes will
allow them to breed healthier dogs and more effectively screen out
those who may fall ill during their service lives. It takes two
years, $35,000, and lots of effort to train a guide dog, said Jane
Russenberger, the director of breeding for Guiding Eyes for the
Blind. Only half the puppies finish training -- the rest are
dismissed for medical or temperamental reasons.
"We are so anxious to hit it on the mark more often," Russenberger
Guide dog schools have been a driving force in genetic research,
donating funds and dog DNA samples to Aguirre's lab, among others.
The Seeing Eye, a guide dog school in New Jersey, has made donations
to Aguirre's research on the genetics of progressive retinal atrophy,
a serious disease that causes blindness in dogs.
Canine genetics also holds more superficial promise. VetGen can read
Labrador retrievers' hidden color genes, at a cost of $85 per test,
enabling breeders to yield litters with the desired combination of
black, yellow, and brown puppies.
Breeders are also looking at the possibility of using genetics to
fine-tune a dog's temperament. They can already mix a Labrador and a
poodle to create a labradoodle, which is reputed to have the
intelligence and hypoallergenic hair of a poodle and the friendliness
of a lab. Essentially just a carefully planned mutt, the labradoodle
has caught on, suggesting an American public eager for
design-your-own dogs. Soon, genetic research may make it possible to
more effectively engineer dog populations with other desirable
traits. For instance, it may be possible to breed dogs that are more
confident, less distractible, and less anxious.
"We do have to fight some of the natural traits," Russenberger said.
The danger is that, even armed with new genetic knowledge, breeders
trying to accentuate certain desirable traits may unwittingly
concentrate genes for some negative traits, said Patricia Olson, the
executive director of the Morris Animal Foundation.
"You might be trying to create an introvert and the dog could become
really anxious," she said. "I think we've got to be really, really
careful, but the potential is there."
And whatever breeders do, sometimes a dog will just be a dog.
"You're not going to get a dog to not be interested in food," said
Ken Rosenthal, president of The Seeing Eye and chairman of the
International Guide Dog Federation. "That's a matter of discipline,