Musladin-Lueke Syndrome (MLS) is a genetic disease of the Beagle that affects the development and structure of connective tissue. It is multi-systemic, with involvement of multiple organs, including bone, heart, skin, and muscle. MLS is inherited as a recessive trait. Current evidence suggests that dogs that have two copies of the mutant gene are affected with MLS, though the severity of clinical signs can be variable. Dogs inheriting only one copy of the mutant gene can show subtle signs but do not appear to have health-related defects. To the best available knowledge, carriers cannot be identified based on their appearance.
The disorder stems from a single mutation that has been inherited through common descent, such that all affected Beagles share the gene from a common ancestor, perhaps dating back to the foundation stock of the breed. This mutation was identified by Dr. Mark Neff at the Veterinary Genetics Laboratory, School of Veterinary Medicine, UC Davis.
Research is ongoing and there are still aspects of this disease that are continuing to be investigated such as the geographic distribution of the mutation among purebred Beagle bloodlines, and the variable nature of the disease.
This DNA test for the mutation causing MLS in Beagles determines whether dogs are normal (clear of the mutation), carrier (have one mutant copy), and affected (have two mutant copies). Dogs that carry two copies of the mutation are susceptible to several health-related consequences. The DNA test can provide a definitive diagnosis for these dogs, but there currently is no established therapeutic intervention.
If a carrier dog (with a single mutant copy of the gene) is used in a mating, an offspring from the cross has a 50% chance of inheriting the mutation from this parent. If two carriers are mated, 25% of the offspring in the litter are expected to have MLS and another 50% of the puppies are expected to be carriers. Mating two clear dogs will only produce clear puppies, which need not be tested by DNA.
Genetic Knowledge of Beagle MLS
The DNA test for Musladin-Lueke Syndrome status is meant to equip owners, breeders, and clinicians with useful information that can be applied in several ways to improve the health of their dogs. It allows owners to establish the MLS-status of their pet and veterinarians to positively diagnose the disease in patients that show MLS-like signs. Test results can be used by breeders to assess potential breeding stock and make fully informed decisions in the choice of mating pairs. The genetic knowledge gained from the test holds promise for eliminating the production of affected dogs in the near-term, and for eliminating the gene defect from the gene pool over time.