The DNA GM2 test is available for Japanese Chin
What is Gangliosidosis?
Brain cells have a surface membrane that acts like the skin of the cell. Within that membrane, there are complex molecules called gangliosides which are important for the ability of brain cells to communicate with each other. That communication between brain cells is what allows us to move, feel, and think. Nothing lasts forever, and the gangliosides in the brain cell membrane eventually wear out and have to be replaced. Worn out molecules in any cell are sent to the lysosome, the cell’s recycling center, where enzymes break down the old molecules. The building blocks can then be reused to make new complex molecules.
If a dog is lacking one of these enzymes, then the recycling process may hit a road block. Unable to breakdown the worn out molecule, it accumulates or is “stored” in the recycling center; hence diseases of this type are called lysosomal storage diseases. The disease is named for the “stuff” that builds up in the cell, and in Gangliosidosis, the stuff that builds up is the gangliosides. Before we knew what was building up, the diseases were named after the physicians who discovered them. Gangliosidosis was called either Tay-Sachs disease or Sandhoff’s disease.
Since the problem is with the recycling of molecules, the brain cell can function fine for a while. It is as if you were still able to go the store, shop, and cook dinner, but you were not able to take out the garbage. You could continue to make dinner for a while, but eventually the garbage would build up in the kitchen until you couldn’t get to the stove or the refrigerator and couldn’t cook anymore. The cell doesn’t have the option of ordering in a pizza, so when this happens the result is a progressive brain disease.
What are the symptoms of Gangliosidosis?
Because it takes time for the storage material to build up enough to interfere with the cell’s function, dogs with Gangliosidosis are normal at first. Somewhere around a 1-1½ years of age, they become mentally dull, may not come when called or ask to go out to potty. They may develop a goose-stepping gait and have problems with their balance. Their head may shake especially when they try to eat. As the disease progresses, their coordination worsens and they become weak. Eventually, they become totally unaware of their surroundings and their quality of life deteriorates until euthanasia must be considered.
What else can look like Gangliosidosis?
Many diseases can cause loss of coordination and altered consciousness in a dog. This would include infections of the brain such as canine distemper, metabolic diseases such as liver shunts or low blood sugar, or toxicities such as lead poisoning. Dogs with Gangliosidosis show atrophy of the brain on MRI scans, but this is a non-specific finding seen in many diseases. If necessary, your veterinarian can refer you to a board certified neurologist who can aid in diagnosing Gangliosidosis. A directory to locate a neurologist near you can be found at www.acvim.org.
Is this a hereditary disease?
Yes, Gangliosidosis is a recessive hereditary disease. In recessive diseases, both parents are usually perfectly normal all their lives. That’s because all genes come in pairs and the normal parents have one normal gene that allows them to produce the enzyme they need. The other gene, however, is the bad gene that cannot produce the enzyme. Each parent passes on one of their genes to their offspring. If a pup is unlucky enough to get the bad gene from each parent, then it cannot produce any enzyme and develops Gangliosidosis.
A DNA test is now available and we believe it would be prudent for Japanese Chin breeders to test dogs that they intend to breed. (Puppies can be tested as early as about 4 weeks of age.) Wise consideration of the DNA test results will allow Chin owners to make informed choices when choosing which dogs to breed, and avoid producing puppies destined to become affected with this disease. Carriers of the mutant gene can be used for breeding, but should be bred to a dog that is tested clear of this mutation. By doing this, no affected dogs will be born, and the desirable traits and genetic diversity that these dogs offer the breed will be maintained.
By using this DNA test wisely, Japanese Chin fanciers can work toward eliminating this devastating disease from the breed while maintaining the genetic diversity and many positive traits that endear these dogs to their devoted owners.
Information supplied by the University of Missouri-Columbia College of Veterinary Medicine, used by permission.
Research Available:
Tests are ordered online through the secure area of the OFA website. Payment is accepted by credit card (MasterCard and VISA). The OFA administers all order handling. Upon receipt of an order, the OFA will send out the test kit which will include a Foam-Tipped Applicator card for DNA sample collection, along with sample collection instructions. Using the FTA card technology, owners can safely collect DNA samples at home. The collection process is non-invasive, and no veterinary appointment is necessary.
Samples are then sent to the University of Missouri College of Veterinary Medicine where the samples will be processed by the Small Animal Molecular Genetics Lab. Results will be forwarded to the OFA, and the OFA will issue the resulting report to the owner.
The fee for each test includes the test kit, laboratory processing, and subsequent registration in the OFA databases.