Nemaline myopathy in American Bulldogs

Nemaline myopathy is a congenital muscle disease caused by a structural disorder of muscle fibres. Affected dogs suffer from generalized muscle atrophy, especially in the neck area and thoracic limb muscles. The disease impairs physical strength and endurance, but dogs can move independently.

The disease is caused by a nonsense mutation g.52734272G>T in the NEB gene, which codes for nebulin, a sarcomeric protein in skeletal muscles.

The mutation is inherited in an autosomal recessive manner. It only manifests itself in individuals who have inherited the mutated allele from both parents (recessive homozygotes). Heterozygotes are individuals who have inherited the mutated allele from only one parent, show no symptoms of the disease, and are clinically healthy. However, they can pass the mutated allele on to their offspring. If two heterozygous individuals mate, theoretically 25% of their offspring will be completely healthy, 50% will be carriers, and 25% will inherit the mutated allele from both parents and will therefore be affected by this disease.

Genetic testing can clearly reveal an animal's genotype and is a useful tool for breeders to prevent the unintentional breeding of affected puppies.

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References:

Evans, J.M., Cox, M.L., Huska, J., Li, F., Gaitero, L., Guo, L.T., Casal, M.L., Granzier, H.L., Shelton, G.D., Clark, L.A. : Exome sequencing reveals a nebulin nonsense mutation in a dog model of nemaline myopathy. Mamm Genome 27:495-502, 2016. Pubmed reference: 27215641