Page 119 - Aussie Magazine - 2023 Issue 2

But there are several very important DNA tests –
one of them is a mutation in the superoxide
dismutase 1 gene (SOD1) mostly causing the
fatal disease DEGENERATIVE MYELOPATHY
(DM).

DM is an autoimmune disease that arises late
in life and attacks the myelin, the “insulation”
on the nerves. Dogs with DM may exhibit
progressive but non-painful weakness and lack
of coordination in the hind limbs, muscle atrophy,
Photographs provided by: Denise Rädisch, Nikola Smrckova
ataxia and leading ultimately to paralyses, being
incontinent. Euthanasia is required once the
Text written by: Martina Svecova & Denise Rädisch
disease begins to impact breathing, mostly 1-2
years after diagnosis.

Presently, there are known 124 canine breeds
which can suffer from the degenerative
myelopathy. The widespread distribution of the signs appeared or by existence of modifying genes
mutation among the breeds suggests that it affecting the symptoms, environmental factors or
originated before diversification of the breeds. an incomplete penetrance of the disease among
the positive homozygotes.
This fatal disease is in most cases caused by a • Healthy/normal dog (N/N) = Tested Genetically
mutation in the superoxide dismutase 1 gene Normal = a dog without mutations
(SOD1), This mutation replaces nucletiode G • Carrier or a dog at risk for DM (N/P) = Tested
with nucletiode A (c.118G>A; SOD1A) within Genetically Carrier = a dog heterozygous for
the coding region of the SOD1 gene. The SOD1A mutation
replacement G with A in the gene sequence • Affected dog (P/P) = Tested Genetically
results in nonsense codon due to which the Affected = recessive homozygote carrying
gene is not correctly transcribed and the protein two mutations in SOD1A gene
superoxide dismutase 1 encoded by SOD1 gene
is not produced. Only in Bernese mountain dog,
this degenerative myelopathy can be caused by
other mutation in the SOD1 gene, which replaces
the nucleotide A with the nucletiode T(c.52A>T;
SOD1B). This mutation is however much more
rarely than the mutation c.118G>A.

DM is a genetic disease inherited in an autosomal There is no effective
recessive manner meaning that the dog must
receive the mutated gene from both parents treatment for DM at present.
to develop the disease. Rarely, this disease Treatment of other concurrent
may develop in heterozygotes, although the
frequency of occurrence is lower. A certain problems such as arthritis or
percentage of dogs positive for DM did hip dysplasia may provide
not exhibit clinical signs in their lifetime.
This can be explained either by the some relief from pain or
death of the dogs before the clinical
discomfort.

A Worldwide Magazine for the Aussie • Issue 2/2023 | 119