Gene Linked to Strange Labrador Retriever Ailment

The findings published this week in Nature Genetics are expected to help dog breeders gradually reduce the number of Labradors with the trait in future generations.

After intense hunting or retrieving exercise, EIC-affected Labradors start to lose control of their hind limbs. In most cases, their legs get wobbly and their limbs give out. In rare cases, the dogs may die. Labradors are the most common dog breed in the world and an estimated three to five per cent of Labradors have this condition.

“After 13 years of working on this problem, we now have the definitive answer about the syndrome’s true cause for Labrador breeders and owners. This discovery will have a huge impact on the Labrador breed worldwide.” says Susan Taylor, a professor of small animal internal medicine at the WCVM.

“This is very exciting because it is the first naturally occurring mutation of this gene identified in any mammal,” adds James Mickelson, professor of veterinary sciences and a genetic researcher at the University of Minnesota. “Its discovery could offer insight into normal as well as abnormal neurobiology in both animals and humans.”

The research team identified a mutant form of the dynamin 1 gene as highly associated with EIC. The dynamin 1 protein normally maintains proper chemical communication between adjacent nerves, also known as synaptic transmission.

The mutated form of the dynamin protein in dogs with EIC appears to have diminished function. As a result, synaptic transmission is interrupted during intense exercise and excitement, causing collapse.

The researchers have also developed a genetic test for the mutated gene and determined that up to 30 per cent of Labrador retrievers are carriers of the mutation. EIC is inherited as an autosomal recessive trait, with affected dogs inheriting one copy of the mutation from each parent. Owners can have their dogs tested through their veterinarian by submitting a blood sample to the University of Minnesota Veterinary Diagnostic Laboratory.

Taylor and her WCVM colleague, small animal surgeon Cindy Shmon, initiated a comprehensive clinical investigation of EIC in 1995 after examining an affected dog that was referred to the WCVM Veterinary Teaching Hospital. Suspecting that the syndrome had a novel genetic basis, Taylor contacted Mickelson and Edward Patterson at the University of Minnesota in 2001.

“The genetic research was based on more than 300 blood samples and pedigrees that we collected from affected and unaffected Labradors throughout North America,” says Taylor, who breeds Labradors and competes with them in retriever field trials.

The EIC research received financial support from the Morris Animal Foundation, the American Kennel Club Canine Health Foundation and the WCVM's Companion Animal Health Fund.

About WCVM: (http://www.wcvm.com) is a Canadian centre of expertise for veterinary education, clinical services and research that’s located on the U of S campus. More than 400 undergraduate and graduate students are enrolled at the regional veterinary college that annually attracts more than $10 million in research funding from public and private sources.

About U of S: (http://www.usask.ca) is one of the leading medical doctoral universities in Canada. With 58 degrees, diplomas and certificates in over 100 areas of study, the university is uniquely positioned in the areas of human, animal and plant studies. World-class research facilities, renowned faculty and award-winning students make the U of S a leader in post-secondary education.