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Myotonia Congenita (MC) Labrador Retriever Type
| Acronym: | MC, CM |
| Gene: | CLCN1 |
| Mutation: | c.2275A>T |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Myotonia Congenita (MC) is a genetic muscle disorder that has been detected in several animals, including humans and dogs. MC is caused by a mutation in the sarcolemmal voltage-gated chloride channel gene (CLCN1) and it is characterized by slow relaxation of skeletal muscles due to disturbance making muscle cells of affected dogs over-excitable. This skeletal muscle disorder has been detected in several dog breeds and all the affected dogs usually show signs such as skeletal muscle stiffness and muscle hypertrophy. The disease does not affect life expectancy and it can be improved with prolonged continued activity, the so-called „warm-up phenomenon“. The type of Myotonia Congenita (MC) that has been detected in Labrador Retriever dogs is caused by a single base change within the CLCN1 coding sequence resulting in compromised chloride conduction in the skeletal muscles of the affected animal.
This type of skeletal muscle ion-channel disorder found in Labrador Retriever dogs is inherited as an autosomal recessive trait, requiring two copies of the mutated CLCN1 gene for the disease to develop. Dogs with only one copy of the mutated gene will not develop the disease but may act as carriers and pass the mutation to their offspring. Early genetic testing can help identify affected dogs that carry the mutation and prevent their further breeding by proper selection of mating pairs.
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:
Quitt, P. R., Hytönen, M. K., Matiasek, K., Rosati, M., Fischer, A., Lohi, H. (2018). Myotonia congenita in a Labrador Retriever with truncated CLCN1. Neuromuscular disorders : NMD, 28(7), 597–605. https://doi.org/10.1016/j.nmd.2018.05.002
Rhodes, T. H., Vite, C. H., Giger, U., Patterson, D. F., Fahlke, C., George, A. L., Jr (1999). A missense mutation in canine C1C-1 causes recessive myotonia congenita in the dog. FEBS letters, 456(1), 54–58. https://doi.org/10.1016/s0014-5793(99)00926-6