Myotubular Myopathy 1 (MTM1 Dog)

• Progressive muscle wasting
• Difficulty getting up and walking
• Breathing difficulties
• Difficulty swallowing
• Hoarse bark

• Myotubular myopathy 1 (MTM1) is a degenerative muscle disease
• The first symptoms become apparent at the age of 10 weeks.
• The weakening of the respiratory muscles leads to death, or affected animals are euthanised.

Labrador Retriever

This mutation test detects a change of a single base pair (c.465C>A) in exon 7 of the MTM1 gene.

Inheritance: X-linked recessive

The affected gene is located on the X chromosome. Males with this mutation are affected (X-mtm1/Y). Females are affected if both X chromosomes are affected (X-mtm1/X-mtm1). They can also have one normal and one mutated chromosome and thus be asymptomatic carriers (X/X-mtm1).

Genotypes:

X/X

→ The dog is a healthy female.

X/X-mtm1

→ The dog is a carrier female. She is healthy, but can pass the mutation (X-mtm1) on to 50% of the offspring.

X-mtm1/X-mtm1

→ The dog is an affected female and dies at an early puppy age.

X/Y

→ The dog is a healthy male.

X-mtm1/Y

→ The dog is an affected male and dies at an early puppy age.

• Carrier females (X/X-mtm1) should not be used for breeding.
• Female offspring of a carrier female should be tested for their genotype (X/X or X/X-mtm1).
• Affected animals do not reach breeding age.

Beggs, A.H., Böhm, J., Snead, E., Kozlowski, M., Maurer, M., Minor, K., Childers, M.K., Taylor, S.M., Hitte, C., Mickelson, J.R., Guo, L.T., Mizisin, A.P., Buj-Bello, A., Tiret, L., Laporte, J., Shelton, G.D.: MTM1 mutation associated with X-linked myotubular myopathy in Labrador Retrievers. Proc Natl Acad Sci USA 107:14697-702, 2010. Pubmed reference: 20682747. Doi: 10.1073/pnas.1003677107.

Further information is available at Online Mendelian Inheritance in Animals.