American veterinary cardiologist Kathryn M. Meurs has discovered a mutant gene in the boxer breed of dogs which causes arrhythmogenic right ventricular cardiomyopathy or ARVC. Large breeds of dogs are often susceptible to either form of cardiomyopathy: Dilated cardiomyopathy (DCM) or ARVC, which can both be fatal.
DCM occurs when the heart muscle is enlarged, becoming thin, weak, and does not contract properly. It most commonly affects large or giant purebred dogs, but it also can be seen in smaller breeds such as cocker spaniels, and in mixed breed dogs.
The condition can lead to congestive heart failure, in which fluid accumulates in the lungs, the chest or abdominal cavities, or under the skin. Because of reduced blood flow to the rest of the body, DCM also can result in weakness, fainting, and exercise intolerance.
Sometimes DCM is complicated by an irregular heartbeat as in ARVC
Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)
A dog affected by ARVC has a rapid, irregular heart beat which does not pump blood efficiently. There may be insufficient circulation to the brain and other organs, leading to fainting episodes or even sudden cardiac death.
The heart chambers are not enlarged as in DCM; instead, the muscle tissue is infiltrated by lacy fatty tissue which weakens the muscle so it can’t pump properly.
This change in the heart tissues can spread to the wall between the heart chambers and even the left ventricle, and will be clearly seen if an autopsy is performed on the dog’s heart after death.
Boxers are particularly susceptible to this condition, which can be fatal and frequently occurs when the animals exercise or become excited. Occasionally, they die from ARVC even while resting.
Mutant Gene Pinpointed as Culprit in ARVC
Veterinary cardiologist Dr Kathryn M. Meurs suspected a gene was involved in ARVC in boxers after working on inherited heart disease in cats and dogs at Washington State University College of Veterinary Medicine.
She has also discovered mutant genes in breeds of cats that also suffer heart disease.
Using an extremely powerful gene screening mechanism at the Massachusetts Institute of Technology, Dr Meurs and fellow investigators looked at thousands of regions of boxer dogs’ DNA simultaneously. The DNA samples came from dogs with ARV and dogs with no evidence of the disease. They were collected by members of the American Boxer Club and the American Boxer Charitable Foundation.
After evaluating thousands of DNA sequences Dr Meurs identified a mutation in a gene that normally codes for a key cellular adhesive protein.
Follow up studies by another WSU veterinary cardiologist, Dr Sunshine Lahmers, showed that these cellular adhesive proteins were located at the junction between cells in the heart. This defect causes electrical impulse conduction problems in the heart, and is in some way responsible for the dog’s rapid, irregular heart beat.
Genetic Test For Boxer ARVC Soon on the Market
Dr Meurs is working on perfecting a genetic testing probe for the mutated gene to be used as a clinical screening device. She has already patented her discovery. The probe will allow vets to take a simple cheek swab from the dog and check whether or not it carries the mutant gene. The test kits should be available in the next few months.
Testing the dog will enable vets to treat affected animals before they become too weak.
“In many cases, after the disease is diagnosed it can be managed with medication for a long enough period in a dog’s life that other diseases such as cancer will actually be the cause of death,” Dr Meurs said.
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Sue Cartledge - I'm a science, health, nutrition and lifestyle journalist, fascinated by the way the physical world operates in all its forms, and how ...
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