Genetic Testing for Inherited Polyneuropathy in Leonbergers Now Available

Sample submission information below

Leonbergers may suffer from a hereditary neurological disease, which has frequently been termed “inherited polyneuropathy (IPN)” or “Leonberger polyneuropathy (LPN)” by veterinarians and breeders. Affected dogs suffer from slowly worsening exercise intolerance and may develop gait abnormalities, such as an exaggerated hitched step, especially in the hind limbs. There is often wasting of the hind limb muscles as well.  Additionally, these dogs may have noisy breathing, a change in their bark, or even difficulty breathing due to involvement of the larynx and laryngeal folds in the throat. Eventually the disease may progress to the point where the dog can no longer support its own weight.

IPN can manifest in a variety of ways, some very mild and some very severe.  Mild IPN can affect dogs that are older and have relatively little impact on the quality of life of the dog.  Some older dogs might tire more easily or breath a little deeper but have no serious symptoms.  However, the early onset IPN is known to cause severe symptoms and can cause significant difficulty in the dog. Genetic research carried out at the University of Minnesota, the University of Bern, and the University of California San Diego, indicates that polyneuropathy is likely a group of several genetically distinct, but clinically similar diseases. Researchers have mapped two major genetic risk loci and identified the causative mutation in one of these loci that we now term LPN1.

Dogs being homozygous mutant (having two copies of the mutation gene) for this mutation will typically develop neuropathy before they reach 3 years of age. At this time researchers do not know whether dogs heterozygous for this mutation (carriers of one copy of the mutation gene) might also develop mild clinical signs late in life, but they will most likely not develop severe disease.

The identified mutation is responsible for approximately one third of the cases of polyneuropathy in Leonbergers. The other two thirds of cases are apparently caused by different genetic mutations.  However, the other two thirds of cases are typically those that manifest in dogs over three years of age with milder symptoms.

The University of Minnesota and the University of Bern will offer genetic testing for the identified LPN1 mutation starting July 1st, 2010. At this time we recommend that all breeding dogs should be tested. Researchers also recommend avoiding breeding homozygous mutant dogs as well as matings that could produce homozygous mutant dogs. Researchers do not recommend excluding heterozygous mutant dogs from breeding as this would significantly constrict the gene pool of the Leonberger population and might lead to an increase in the other forms of disease. However, dogs heterozygous for the LPN1 mutation should only be mated to tested dogs which are free of the mutation. This will ensure that no homozygous mutant offspring affected with the severe form of the disease will be born.  All dogs that are going to be bred should be tested for LPN1 and carefully bred to ensure that the offspring will not produce this one form of neuropathy.

At this time the implementation of genetic testing cannot completely eliminate polyneuropathy from the Leonberger population. This LPN1 test diagnoses only one of possibly several genetic risk factors. Thus, it is still possible that affected offspring with a different genetic form of polyneuropathy will result even from a mating of two dogs that both have been tested free for this mutation.  However, the current LPN1 test can reliably eliminate one severe early-onset form of disease and significantly reduce the overall frequency of neurological disease in Leonbergers.

Instructions for ordering the LPN1 test:

North America.  Genetic testing will be performed at the University of Minnesota Veterinary Diagnostic Laboratory.  The preferred sample is 2-3 ml of fresh blood collected in EDTA tubes.

Further information on sample submission, as well as the required submission forms is available at: http://www.cvm.umn.edu/vdl/ourservices/canineneuromuscular/home.html

The samples, packaged in a padded, leak-proof container, accompanied by a submission form for each dog, should be sent by regular mail, without cooling, to the Veterinary Diagnostic Laboratory:

Veterinary Diagnostic Laboratory
College of Veterinary Medicine
University of Minnesota
1333 Gortner Avenue
St Paul, MN  55108-1098
Phone: (612) 625-8787 or (800) 624-8787
Website: www.vdl.umn.edu
LPN-specific questions email: lpninfo@umn.edu

The price per test is $85 and the expected turnaround time is 3 – 4 weeks.

We encourage all breeders to test their breeding stock prior to the mating, which should completely eliminate one form of the early onset LPN1 from our wonderful Leonbergers.  Great news and congratulations to the researchers for their dedication and commitment to this project!  Hopefully further genetic testing for the other forms of LPN will be available soon.