Muscular dystrophy in Landseer breed

Muscular dystrophy is an inherited disease causing progressive muscle weakness. This disease is caused by mutation c.289G>T in subunit of COL6A1-gene encoding collagen type VI that has been identified only in Landseer breed. The signs accompanying this disease are similar to Duchenne muscular dystrophy affecting Golden Retriever dogs. The affected dogs have severe problems with gait; they usually are able to do several steps before lying down. While standing, the back is arched and the pelvic limbs are placed under the abdomen. On palpation, the muscles of the limbs seem to be atrophied and the articulations of elbow, carpus, hip and tartus had a decreased range of motion. The affected dogs suffer from joint pain. The affected puppies are euthanized at 5 to 15 months of age.

Muscular dystrophy in Landseer is a recessively inherited disease. The disease develops in dogs which inherit the mutated gene from each parent.  These dogs are designated as P/P (positive/positive). The carriers of the mutated gene are designated as N/P (negative/positive). The carriers inherited the mutated gene from one parent only and are without clinical signs. However, they pass the disease on to their offspring.  When mating two heterozygotes (N/P), there will be theoretically 25% of the offspring healthy, 50% of the offspring will be carriers and 25% of the offspring will inherit the mutated gene from both parents and will be affected by Muscular dystrophy.  Mating one healthy dog (N/N) with a carrier of this mutation (N/P) will theoretically produce 50% carriers and 50% healthy offspring.  If a carrier (N/P) is mated with an affected dog (P/P), there will be theoretically 50% affected dogs and 50% carriers.

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Reference:

Steffen, F., Bilzer, T., Brands, J., Golini, L., Jagannathan, V., Wiedmer, M., Drögemüller, C., Drögemüller, M. & Leeb, T. (2015). A nonsense variant in COL6A1 in Landseer dogs with muscular dystrophy. G3: Genes| Genomes| Genetics, 5(12), 2611-2617.