Muscular Dystrophy (DMD gene, Golden Retriever)

Muscular dystrophy is an X-linked inherited disease characterized by progressive muscle degeneration and muscle weakness. This disorder mainly affects males and results from mutations in the dystrophin gene.

Symptoms

The initial clinical signs of muscular dystrophy usually manifest at around 8 weeks of age. At this stage, dogs show muscle weakness, difficulty tolerating exercise and a stiff gait. As the weeks pass, the muscle atrophy worsens and symptoms such as generalized weakness, enlargement of the tongue and difficulties in swallowing and eating are added. In addition, affected dogs suffer from respiratory problems, brief episodes of neck muscle spasms and are at risk of developing muscular heart disease, which can trigger a fatal outcome.

Disease Management

Unfortunately, there is currently no specific therapy that cures muscular dystrophy. However, approaches such as anabolic supplements, growth factors and stem cell therapy have been investigated and may provide benefits by delaying or ameliorating the clinical signs of the disease. It is important to note that the efficacy of these approaches is not guaranteed and they still require further research to understand their true potential.

Genetic basis

This disease follows an X-linked recessive mode of inheritance. Recessive X-linked inheritance means that female dogs must receive two copies of the mutation or pathogenic variant (one from each parent) to develop the disease, whereas males need only one copy of the mutated gene or variant from the dam to develop the disease. Male dogs usually show symptoms of the disease. Each male puppy born to a mother carrying the mutation has a 50% chance of inheriting the mutation and thus the risk of developing the disease. Bitches that do not carry the mutation are not at increased risk of having affected puppies. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

Muscular dystrophy is a disorder characterized by progressive degeneration of muscle fibers, caused by mutations in the DMD gene, responsible for the production of dystrophin. Dystrophin is an essential protein that has a dual function: it acts as a structural component of muscles and also connects the contractile apparatus to the sarcolemma. Thus, dystrophin is considered to provide mechanical stability during muscle contraction. This disease is also known as Golden Retriever muscular dystrophy, since it was in this breed that the condition was first discovered in 1992. The mutation identified in the Golden Retriever (c.531-2A>G) causes a change in the reading frame, resulting in the premature termination of the translation of the dystrophin protein. It is important to note that over the years different variants of the disease have been described in different breeds. However, not all mutations identified to date are analyzed in our test.

Most affected breeds

Golden Retriever

Bibliography

Sharp NJ, Kornegay JN, Van Camp SD,et al. An error in dystrophin mRNA processing in golden retriever muscular dystrophy, an animal homologue of Duchenne muscular dystrophy. Genomics. 1992 May;13(1):115-21.