[COMPLETED] Genotype and Allele Frequencies of Canine Degenerative Myelopathy-Associated SOD1 Gene Variant in Irish Wolfhound Dogs

Canine degenerative myelopathy (DM) is a slowly progressive, late-onset neurodegenerative disorder presenting with thoracolumbar myelopathy, which may eventually progress to various impairments, such as respiratory dysfunctions, leading to death (Coates and Wininger 2010; Kobatake et al. 2021). Dogs homozygous for a single nucleotide variant in SOD1 (NM_001003035.1:c.118G>A [p.E40K]; NC_006613.4:g.26532306G>A) are considered to be at high risk for DM, and this variant has been reported to be prevalent in many canine breeds (Awano et al. 2009; Zeng et al. 2014). Heterozygous dogs rarely develop the disease (Zeng et al. 2014). The definitive diagnosis is only made by histopathology; therefore, antemortem presumptive diagnosis is made based on the combination of clinical findings, including lack of clinically relevant neuroimaging findings, and detection of the homozygous SOD1 variant (Coates and Wininger 2010). Several diseases may mimic DM or coexist with it, including degenerative lumbosacral syndrome, intervertebral disc disease, spinal cord neoplasia, and some orthopedic disorders (Kneller et al. 1975). Thus, genetic testing is important for antemortem diagnosis (Bouché et al. 2023).

The Irish Wolfhound (IW) is a large breed in which hindlimb dysfunction markedly impacts the quality of life for both dogs and their owners and may ultimately lead to euthanasia. No histopathologically confirmed DM cases have been reported in this breed; however, some owners and veterinarians have expressed anecdotal concern about DM in IW dogs, despite the lack of evidence.

It remains uncertain whether the SOD1 variant is prevalent in IW dogs and whether DM should be routinely considered in the differential diagnosis of aged IW dogs with thoracolumbar myelopathy. A previous study identified three heterozygous and 40 wild-type dogs out of 43 genotyped (Zeng et al. 2014); however, further studies involving a larger number of dogs are needed to accurately determine genotype and allele frequencies. Therefore, this study aimed to determine the frequencies of the SOD1 c.118G>A genotype and allele in a larger population of IW dogs born in North America during the recent decade (2014–2023).

Study Results

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