Breeds Affected: Rottweiler
Samples Accepted: Blood, Buccal Swabs
Disease Information: The first symptoms of X-linked Myotubular Myopathy (XLMTM) in the Rottweiler are usually seen between 6 – 8 weeks of age. These include weakness and poor muscle development. The disease progresses quickly. When standing pups stand in a hunched position; they have trouble raising their heads. They die or are humanely euthanized usually before 4 months of age.
Inheritance Information: XLMTM is X-linked recessive, because the MTM1 gene is located on the X-chromosome. Male animals with the mutation (which have only one X chromosome) are affected. Females may have one normal and one mutated version and be asymptomatic carriers.
The possible genotypes are:
XX This dog is a normal female.
XXXLMTM This dog is a carrier female. She is clinically normal, but will pass the mutation (XXLMTM) to 50% of her offspring. When bred to a normal male, she can have pups of all four genotypes: normal female (XX), carrier female (XXXLMTM), normal male (XY), and affected male (XXLMTMY).
XY This dog is a normal male.
XXLMTMY This dog is an affected male.
– Female offspring of a carrier female should be genetically tested to determine if they are normal or carriers (XX or XXXLMTM).
– Carrier females (XXXLMTM) should not be bred, because affected males can be produced.
Test Information: This mutation test identifies a single base change in exon 11 of the MTM1 gene.
Shelton, G.D., Rider, B.E., Child, G., Tzannes, S., Guo, L.T., Moghadaszadeh, B., Troiano, E.C., Haase, B., Wade, C.M., Beggs, A.H.: X-linked myotubular myopathy in Rottweiler dogs is caused by a missense mutation in Exon 11 of the MTM1 gene. Skelet Muscle 5:1, 2015. Pubmed reference: 25664165. DOI: 10.1186/s13395-014-0025-3
Further information is available at the Online Mendelian Inheritance in Animals website.