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Canine Degenerative Myelopathy (DM)
| Acronym: | DM |
| Gene: | SOD1 |
| Mutation: | c.118G>A |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Canine degenerative myelopathy (CDM) is an adult-onset, progressive neurodegenerative disease of the spinal cord. Most dogs are at least 8 years old before the onset of clinical signs. The initial signs of degenerative myelopathy typically include asymmetric general proprioceptive ataxia and spastic paresis in the pelvic limbs. At this stage, segmental spinal reflexes are indicative of upper motor neuron loss. The disease duration can exceed 3 years, however, its progression is relentless, and dog owners usually elect euthanasia within a year of diagnosis when their dogs become paraplegic. When euthanasia is delayed, weakness can ascend to the thoracic limbs with the emergence of lower motor neuron signs such as flaccid tetraplegia, widespread muscle atrophy, dysphagia, and inability to bark. Because a variety of common acquired compressive spinal cord diseases can mimic the early signs of canine degenerative myelopathy by compromising upper motor neuron pathways, a definitive diagnosis of canine degenerative myelopathy can only be made postmortem by the histopathologic observation of axonal and myelin degeneration along with astrogliosis in spinal cord funiculi. This disease occurs in all dog breeds, but some breeds including the Pembroke Welsh corgi, Boxer, Rhodesian ridgeback, Chesapeake Bay Retriever, and German Shepherd dogs are particularly susceptible, with 30 – 90% homozygous affected dogs, mostly differing relative to geographic positions.
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:
Awano, T., Johnson, G.S., Wade, C.M., Katz, M.L., Johnson, G.C., Taylor, J.F., Perloski, M., Biagi, T., Baranowska, I., Long, S., et al. (2009). Genome-wide association analysis reveals a SOD1 mutation in canine degenerative myelopathy that resembles amyotrophic lateral sclerosis. PNAS 106, 2794–2799.
Holder, A.L., Price, J.A., Adams, J.P., Volk, H.A., and Catchpole, B. (2014). A retrospective study of the prevalence of the canine degenerative myelopathy associated superoxide dismutase 1 mutation (SOD1:c.118G > A) in a referral population of German Shepherd dogs from the UK. Canine Genetics and Epidemiology 1, 10.
Zhang, Q., Acland, G.M., Wu, W.X., Johnson, J.L., Pearce-Kelling, S., Tulloch, B., Vervoort, R., Wright, A.F., and Aguirre, G.D. (2002). Different RPGR exon ORF15 mutations in Canids provide insights into photoreceptor cell degeneration. Hum. Mol. Genet. 11, 993–1003.