Unlike genomic DNA, there are thousands of mitochondria in each cell of the body. Mitochondria are the ‘powerhouses’ of the cell, and each holds its own mtDNA. For a dog to be at risk for a mitochondrial disorder, it must inherit a certain ratio of mtDNA with the disease variant compared to normal mtDNA. mtDNA is inherited only from the mother.
At risk dogs have a small chance of showing signs of this disease in their lifetime, but many will never develop the condition due to absence of additional risk factors.
Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.
Dogs with SAN begin to show evidence of the condition between 2 to 8 months of age. However, many dogs with the genetic disease variant will never go on to develop clinical signs of the disease. In dogs with the disease variant that do develop clinical disease, the clinical signs appear insidiously, with affected dogs exhibiting ataxia and dysmetria. Decreased spinal reflexes and abnormal postural reactions are also seen, though they are not accompanied by muscle atrophy. Disease progression is slow but euthanasia is often elected while the dog is still a juvenile. SAN has only been found to cause disease in Golden Retrievers and when inherited through the maternal lines, and it should also be noted that the variant is a risk factor meaning that not all Golden Retrievers with copies of the variant will go on to exhibit clinical signs. Akitas have been found to have an alternative genetic variant in the exact same location as the mutation identified in Golden Retrievers. While the two mutations cannot be distinguished by the technology used in this test, the Akita variant is neutral and does not cause the condition, so dogs inheriting this neutral variant are not affected. Therefore, the clinical significance of this disease variant in dogs where it has not been inherited through maternal lines of Golden Retriever ancestry is not yet clear.
The wellbeing of dogs clinically affected with Sensory Ataxic Neuropathy should be monitored closely as the disease progresses. Euthanasia is usually elected on welfare grounds when clinical signs become severe as there is no cure for affected dogs.
There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.
This disease mutation is found in the mitochondrial DNA, which is inherited through the maternal lines. Females with the mutation should not be bred with, as resulting litters would contain puppies with mutated mitochondrial DNA, which could be clinically affected. Male dogs with the mutation could theoretically be bred without producing affected offspring. Please note: It is possible that disease signs similar to the ones caused by the SAN mutation could develop due to a different genetic or clinical cause.
All coordinates reference CanFam3.1
Hultin Jäderlund, K., Örvind, E., Johnsson, E., Matiasek, K., Hahn, C. N., Malm, S., & Hedhammar, Å. (2007). A neurologic syndrome in golden retrievers presenting as a sensory ataxic neuropathy. Journal of Veterinary Internal Medicine. View the article
Baranowska, I., Jäderlund, K. H., Nennesmo, I., Holmqvist, E., Heidrich, N., Larsson, N. G., … Andersson, L. (2009). Sensory ataxic neuropathy in golden retriever dogs is caused by a deletion in the mitochondrial tRNATyr gene. PLoS Genetics, 5(5). View the article