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Congenital Myasthenic Syndrome (CMS) – Jack Russell Terrier Type
| Acronym: | CMS |
| Gene: | CHRNE |
| Mutation: | c.636_637insC |
| Inheritance: | Autosomal Recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Congenital Myasthenic Syndromes (CMS) is a large group of genetic disorders of the neuromuscular junction causing severe generalized skeletal muscle weakness and fatigue. CMSs have been firstly described in Jack Russell Terrier (JRT) dogs and the disease has the highest incidence in this dog breed. Affected dogs start to show symptoms early in life and they include decreased reflexes in all limbs and a short-stride gait that progressively worsens until they collapse. This type of neuromuscular disorder is caused by a specific mutation within the CHRNE gene. CHRNE encodes a component (subunit) of the acetylcholine receptor (AChR) protein with an important role in the signaling pathway. A deficiency of junctional AchRs causes a malfunction in the transmission of signals between the nerves and muscles.
Myasthenic Syndrome found in Jack Russell Terrier dogs is inherited as an autosomal recessive trait, requiring two copies of the mutated 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 detection by genetic testing can identify carriers and help breeders in selecting future mating pairs which can be used to avoid unintentional breeding of affected dogs.
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:
Rinz, C. J., Lennon, V. A., James, F., Thoreson, J. B., Tsai, K. L., Starr-Moss, A. N., Humphries, H. D., Guo, L. T., Palmer, A. C., Clark, L. A., Shelton, G. D. (2015). A CHRNE frameshift mutation causes congenital myasthenic syndrome in young Jack Russell Terriers. Neuromuscular disorders : NMD, 25(12), 921–927. https://doi.org/10.1016/j.nmd.2015.09.005
Wallace, M. E., Palmer, A. C. (1984). Recessive mode of inheritance in myasthenia gravis in the Jack Russell terrier. The Veterinary record, 114(14), 350. https://doi.org/10.1136/vr.114.14.350