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Myotonia Congenita (MC) Miniature Schnauzer Type
| Acronym: | MC, CM |
| Gene: | CLCN1 |
| Mutation: | c.803C>T |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Canine myotonia congenita is an inherited condition characterized by delayed relaxation of skeletal muscle after voluntary contraction without associated symptoms of weakness or muscular dystrophy. Another symptom of canine myotonia congenita is skeletal muscular hypertrophy. Myotonia congenita results from genetic defects in the skeletal muscle chloride ion channel (CLCN-1) and the ensuing reduced chloride ion conductance across the sarcolemma.
Canine myotonia congenita has been characterized best in Miniature Schnauzers. In this breed, it is inherited as an autosomal recessive trait. Myotonic Miniature Schnauzers have hypertrophic skeletal muscles, difficulty in rising after a period of rest, a stiff and stilted gait when walking, and a bunnyhop-type movement when running. In addition, there are increased respiratory sounds, difficulty when swallowing, ptyalism, dental abnormalities, and superior prognathism, a unique feature of myotonia congenita in this breed.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Bhalerao, D.P., Rajpurohit, Y., Vite, C.H., and Giger, U. (2002). Detection of a genetic mutation for myotonia congenita among Miniature Schnauzers and identification of a common carrier ancestor. American Journal of Veterinary Research 63, 1443–1447.
Rhodes, T.H., Vite, C.H., Giger, U., Patterson, D.F., Fahlke, C., and George Jr., A.L. (1999). A missense mutation in canine ClC-1 causes recessive myotonia congenita in the dog1. FEBS Letters 456, 54–58.