X-linked myotubular myopathy / XLMTM (MTM1-related) - Boykin Spaniel

What does this test analyse?

This DNA test analyses the MTM1 c.1467C>T variant in the Boykin Spaniel. The condition is known as X-linked myotubular myopathy, XLMTM, myotubular myopathy type 1, centronuclear myopathy and MTM1-related myopathy.

What does this condition mean?

MTM1 encodes myotubularin, a protein important for normal muscle fibre development, T-tubule organisation and muscle contraction. The nonsense variant p.(R512*) disrupts this function and causes a severe progressive muscle disease, especially in male puppies.

Affected puppies typically show muscle weakness early in life. Typical signs include tetraparesis, general weakness, difficulty holding the head up, difficulty closing the mouth, abnormal muscle biopsy and rapid progression. The course is severe and progressive, so affected puppies often cannot grow, move or eat normally.

Inheritance and result

This trait is inherited as X-linked recessive. A dog without the variant has C/C / C/Y. A female with C/T is a carrier. A male with T/Y is genetically affected; a female with two variant copies also falls in the affected genotype category.

Practical value of this test

This test is important for breeding selection because carrier females can look healthy, while male offspring that inherit the variant allele develop the severe muscle disease. The result makes risk matings visible before breeding decisions are made.

• Helps identify carrier females in Boykin Spaniel lines.
• Helps prevent matings that can produce affected males.
• Supports family screening after muscle weakness, abnormal gait or early puppy loss.
• Gives breeders clear information for mating plans without unnecessarily losing valuable lines.
• Improves transparency with puppy buyers by documenting the hereditary status of breeding dogs.