Dog breed genetic tests put to the test!
Dog breed genetic tests put to the test - VIN
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July 10, 2012
By: Edie Lau
For The VIN News Service
What’s my breed?
To gauge the accuracy and consistency of canine DNA breed identification laboratory analyses marketed to curious dog owners, we ran these six dogs through a series of tests. They are (1) Tag, (2) Finn, (3) Salem, (4) Solara,
(5) Annie, (6) and Laika. See the results.
Divining the breeds that make up a mutt is amusing sport for most dog lovers, and veterinarians are no exception. So when the first DNA test for dog breeds hit the market in 2007, interest and curiosity were keen. Soon, so was skepticism.
On a message board of the Veterinary Information Network (VIN), an online community for the profession, veterinarians reported a variety of results in friends, clients’ and their own dogs. Some were plausible and some were wacky.
On the wacky side was an 80-pound dog whose mother was known to be a Labrador retriever that tested as mostly miniature poodle plus Yorkshire terrier.
There was a pedigreed dachshund who turned up as predominantly Siberian husky, with a dash of dachshund and Ibizan hound.
There was a dog that looked classically Chihuahua that came back as “an extremely complex mixed-breed dog ... (with) distant traces of Afghan hound, Cavalier King Charles spaniel and toy fox terrier.”
And so on.
Five years since companies introduced commercial dog breed identification genetic tests, veterinarians continue to wonder if the tests are valid. Hoping to find the answer, the VIN News Service put the tests to the test.
We submitted DNA samples on six dogs to compare the results and check for consistency. We knew the breed backgrounds of four of the dogs, so were able to determine whether the tests gave correct answers.
When we started the project, five tests were available. Four were variations of Wisdom Panel, which is owned by Mars Veterinary. The fifth test was Canine Heritage by Scidera, LLC.
What we found: Wisdom Panel was the superior competitor. Though not flawless, the test tended to give reasonable and usually consistent, if not necessarily enlightening, results. Veterinary geneticists we consulted also pointed to Wisdom Panel as the most scientifically reputable.
“Mars, I know, is constantly reviewing and analyzing and upgrading what they’re doing,” said Dr. Jerold Bell, a clinical associate professor of genetics at Tufts University Cummings School of Veterinary Medicine. “They’re one of the few that have done the research and continue to do the research to make it as scientifically valid as possible.”
In its early days, the test was nicknamed “Witless” by some skeptical veterinarians. Wisdom Panel’s more dependable results today may be a product of improvements developed over the years, chiefly expansion of the company’s breed database.
Breed genetics concept scientifically credible
The concept of determining a dog’s breed background by analyzing its DNA is grounded in science. In a paper published in the journal Science in 2004, canine geneticist Elaine Ostrander and colleagues described a technique they developed for identifying dog breeds based on genetic markers. Ostrander, who currently works at the National Human Genome Research Institute, part of the National Institutes of Health, described the approach, along with her broader work on the canine genome, in an article published in 2007 by American Scientist.
The markers the researchers used are not genes themselves, but repeating sequences of DNA known as microsatellites. The commercial tests use a different kind of marker known as single-nucleotide polymorphisms — abbreviated SNPs and pronounced like "snips” — that are small mutations within the genome. Whether using microsatellites or SNPs, the markers, taken together, form signatures particular to each breed.
Because the identification technique is not based on genes, it does not specifically relate to physical or behavioral traits that characterize particular breeds. In other words, the technique doesn’t recognize a bulldog by finding the genes that give it a snub nose, beefy head and squat stature.
Consequently, breeds that are vastly different in appearance might, by chance, have similar genetic signatures, which helps explain some head-scratching results. For example, portions of the signatures of Chihuahuas and some mastiff breeds are maddeningly similar, according to Dr. Angela Hughes, a veterinarian and geneticist at Mars Veterinary.
On the other hand, some breed combinations truly result in dogs that resemble other breeds entirely. Hughes recalled a case of a dog that looked like a black Labrador retriever that tested as a golden retriever mix, which made sense to her as a geneticist.
“You can lose that longer coat in one generation,” she explained. “Goldens carry a black gene. They don’t express it in their coat because the yellow gene blocks all black. They do express it in their nose, eye rims and the pads of their feet. But the golden is recessive. So if you breed a golden retriever to a dog that doesn’t have the genes for yellow and long hair, you’re likely to have a black dog with a short coat.”
In a similar vein, test results suggesting pairings of large with small dogs may raise doubts but such combinations aren’t impossible, Hughes said. She explained: “The larger female will lie down” for the mating.
Breeds have distinctive genetic signatures owing to the fact their members are genetic isolates — that is, bred from a limited population of dogs. The more unique the breed characteristics, the easier to identify a breed's members via their DNA. Explained Dr. Urs Giger, a veterinarian who heads the clinical program in medical genetics and pediatrics at the University of Pennsylvania (UPenn) School of Veterinary Medicine: “The more you’re inbreeding ... that will clearly make the genes among the dogs more similar.”
A mixed-breed dog whose parents or grandparents are purebred generally is easier to identify than a dog descended from generations of mixes.
Giger said improvements in DNA-based breed identification may contribute to the development of genetic tests for medical conditions. “The mixed-breed test is the first complex-trait test and thereby is showing the way (for) testing for other complex traits, like hip dysplasia, in the future,” he said.
The science of dog-breed detection may be solid, but that doesn’t mean any given DNA test is reliable. Its accuracy depends upon the quality of information upon which the analysis is based.
For example, when the Canine Heritage test debuted in early 2007 as the first such test on the consumer market, it detected 38 breeds. Results for any dog with a background outside of those 38 breeds would have been inconclusive.
Wisdom Panel launched in fall 2007 with 134 breeds. Now Canine Heritage is up to 120 breeds, while Wisdom Panel lists 203.
In setting out to test the tests, the VIN News Service surveyed the market to determine how many competing tests were available in the United States. Looking at website domain names, there appeared to be multiple options. On closer examination, we discovered the websites led to only two test brands. They have sites under their own names — Canine Heritage® Breed Test
and Dog DNA Test, Dog Breed Test - Wisdom Panel Canine DNA Testing | Wisdom Panel
— plus others. For example, Dog DNA Test Doggie DNA Testing and Mixed Breed Canine DNA Testing For Dogs - Dog-DNA.com
peddles the Canine Heritage test. The site Mixed Breed Dog Game ? Guess Your Canine?s Genetic Heritage
and Wisdom Panel Insights - Canine Heritage - Proof of Parentage Dog DNA Test
promote Wisdom Panel.
A third laboratory, BioPet, whose dog breed DNA tests were sold under the brand names BioPet and PetSafe, left the market last year in the face of a patent infringement suit pressed by Mars and the patent owners.
At the outset, Mars obtained an exclusive license from Fred Hutchinson Cancer Research Center and Argus Genetics, LLC, on their patent-pending process of discerning the breeds in a mixed-breed dog through DNA analysis. (Ostrander and team worked at Fred Hutchinson at the time they invented the process.) After the U.S. patent was granted in 2010, Mars took BioPet, PetSafe and the owner of Canine Heritage to court.
Soon, Mars' dominance will be complete: Canine Heritage is leaving the market. Mars is acquiring the test, according to Canine Heritage spokeswoman Anna Rogatkin. The Canine Heritage website states that the laboratory will coordinate with Mars to continue processing samples submitted within 90 days, starting June 19.
At the time our project began, we still had two different laboratories to compare. We looked at Canine Heritage’s single test aimed at mixed-breed dogs and Wisdom Panel’s four tests.
The original Wisdom Panel test is a “professional” version that must be purchased through a veterinarian and requires a veterinarian’s services in taking and submitting a blood sample. The resulting report is more detailed and includes information for the veterinarian about medical conditions to which the identified breeds are prone.
In 2009, Wisdom Panel introduced a mixed-breed test like Canine Heritage’s. Both are do-it-yourself tests in that the dog owner or handler collects the DNA via a “cheek swab” using a small brush run along the inside of the dog’s cheek. Test kits come with brushes and return envelopes.
In 2011, Wisdom Panel introduced two new variations. One is for purebred dogs, the other for designer dogs, which are deliberate crosses of two purebred dogs along the lines of Labradoodles (Labrador retriever-poodle mix) and puggles (pug-beagle mix). The purebred and designer dog tests use cheek swab samples.
In terms of the quality of DNA extracted from cheek swabs versus blood, there is no difference, according to Bell, the veterinary geneticist at Tufts.
“We do cheek-swabbing all the time. I think the validity of cheek swabs is pretty high,” Bell said. “It’s pretty hard to mess up a cheek swab. At most, they don’t get DNA. It’s not that they get the wrong DNA or DNA from what the dog just ate.”