Dog breeders often talk about genetic screening or DNA tests on their dogs. The field of canine genetic research has grown over the last few decades, and exponentially since the entire canine genome was mapped in July 2004, based on the DNA of a Boxer named Tasha. Still, a lot of confusion surrounds these tests, and many Boxer owners -- and even some Boxer breeders -- don't really understand what the tests find and what they tell you about your Boxer.
DNA Profile and Parentage Evaluation
For many years, the only "DNA test" available for Boxers was the profile, a unique genetic code similar to a fingerprint for dogs. The American Kennel Club instituted their Frequently Used Sires program in July, 2000, which required any dog siring more than three litters in a year, or seven or more litters in his lifetime, to have a DNA profile on record with the AKC. The DNA profile is also used if there was a question about the sire of the litter, much like a human paternity test.
DNA Test for Degenerative Myeloopathy
In 2008, researchers at the University of Missouri and the Broad Institute announced they had discovered a genetic mutation that carried a high risk for degenerative myelopathy, a progressive neurological disorder of the spine that affects multiple breeds, including Boxers. Dogs with two copies of the mutation are at risk of developing DM, while dogs with one or no copies of the mutation are considered highly unlikely to be affected by the disease. An at-risk dog may never develop DM, however; research is ongoing to determine what other factors play a role in the condition. Owners of at-risk dogs should study the history of DM in the dogs' relatives to determine an estimated risk. DM is considered an old-age disease, typically developing when the dog is 10 years or older.
DNA Test for Arrhythmogenic Right Ventricular Cardiomyopathy
Dr. Kathryn Meurs, who has been studying Boxer heart diseases since the 1990s, announced in 2009 that she had found a genetic mutation associated with arrhythmogenic right ventricular cardiomyopathy, also called Boxer cardiomyopathy. A DNA test was developed shortly thereafter. The DNA test for ARVC is not as clear-cut as the test for DM; a Boxer may develop ARVC regardless of his DNA test results. Dogs that are affected by ARVC and have two copies of the mutation will generally have a more severe form of the disease than dogs wtih one or no copies. In humans, eight gene locations have been identified as playing a role in cardiomyopathy; it is likely that more than one gene is involved in the condition in Boxers, as well. Additionally, other genes and even environmental factors may modify the expression of the disease.
DNA Test for Juvenile Renal Dysplasia
Renal dysplasia is a serious but relatively uncommon condition in Boxers. The kidneys do not develop normally, and the dog generally does not thrive and dies at a young age. The Broad Institute has been researching the disease in Boxers, but the lack of adequate DNA samples from affected dogs has hindered their progress. A DNA test is available for JRD in other breeds; at least one company claims the test will screen Boxers as well. The accuracy of the test has been questioned, however, especially since at least two breeds have different genetics involved with JRD.
DNA Test for Breed Identification
In recent years, breed ID testing has gained in popularity. The tests appeal not only to owners of mixed-breed dogs, but to owners of short-haired, medium-sized dogs of unknown breeds who want to avoid breed bans and prove their dogs are not one of the "pit bull" type breeds. Only a few breeds can be detected by the tests, however, so the validity of the results is compromised. In some cases, dogs with generations of know pedigrees have come back as an entirely different breed.
Currently, DNA tests for Boxers are used for information rather than diagnosing disease. Family history and other testing, such as holter monitoring for ARVC, remain an important factor in determining a dog's risk. Breeders should avoid making breeding decisions based on any one test, regardless of the results, and instead consider the information as part of the dog's whole package.
The DM DNA test is available through the Orthopedic Foundation for Animals; the ARVC DNA test is available from Washington State University's Veterinary Cardiac Genetics Lab. Both tests are simple cheek swabs and easy for an owner to do at home.
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