SPONTANEOUSLY ARISING DISEASE Degenerative Myelopathy in Hovawart Dogs: Molecular Characterization, Pathological Features and Accumulation of Mutant Superoxide Dismutase 1 Protein Luciana Mandrioli * , Gualtiero Gandini * , Fabio Gentilini * , Roberto Chiocchetti * , Maria E Turba † , Giancarlo Avallone * , Valeria Pellegrino * , Marika Menchetti * , Yui Kobatake ‡ , Hiroaki Kamishina # and Carlo Cantile x * Department of Veterinary Medical Sciences, University of Bologna, Bologna, † Laboratorio Genefast, Forlı, Italy, ‡ The United Graduate School of Veterinary Sciences, Gifu University, # The United Graduate School of Veterinary Sciences, Gifu University and Joint Department of Veterinary Medicine, Gifu Center for Highly Advanced Integration of Nanosciences and Life Sciences, Gifu, Japan and x Department of Veterinary Sciences, University of Pisa, Pisa, Italy Summary Degenerative myelopathy (DM) is an adult-onset, progressive neurological disease affecting several breeds of dog. Homozygosity or compound heterozygosity for the canine superoxide dismutase 1 (SOD1) gene muta- tions, possibly modulated by the modifier SP110 locus, are associated with a high risk for DM. Although the pathophysiological mechanisms are largely unknown, a role for mutant SOD1 in causing neuronal degenera- tion has been postulated. Three Hovawart dogs, 9e12 years of age, developed slowly progressive incoordina- tion and weakness of the pelvic limbs leading to non-ambulatory flaccid paraparesis and muscle atrophy. Neuropathological lesions comprised axonal degeneration and loss of ascending and descending spinal path- ways, which were most severe in the mid- to caudal thoracic segments. Accumulation of mutant SOD1 protein in neurons and reactive astrocytes was demonstrated by immunolabelling with the 16G9 antibody against the mutant SOD1 protein (p.E40K amino acid substitution). All three dogs were homozygous for the c.118A allele, but none had the SP110 ‘risk’ haplotype, suggesting a weak association of SP110 with the onset of DM in this breed. Our data suggest that the Hovawart breed is predisposed to the SOD1:c.118G>A mutation, which is associated with the development of DM. Prevention of DM could be achieved with the help of strategies based on epidemiological and genetic testing. Ó 2020 Elsevier Ltd. All rights reserved. Keywords: degenerative myelopathy; Hovawart; SP110; superoxide dismutase 1 Introduction Canine degenerative myelopathy (DM) is a neuro- degenerative disease that has been described in an increasing number of breeds (Pfhaler et al, 2014; Kohyama et al, 2017). DM is characterized by pro- gressive gait abnormalities of the pelvic limbs, con- sisting, in the early phase, of asymmetric upper motor neuron paraparesis, general proprioceptive ataxia and lack of panniculus response. The clinical signs develop progressively to non-ambulatory lower motor neuron paraparesis and paraplegia (Coates and Wininger, 2010). Spontaneous missense patho- genic variants of the superoxide dismutase 1 J. Comp. Path. 2021, Vol. 182, 37e42 Available online at www.sciencedirect.com ScienceDirect www.elsevier.com/locate/jcpa Correspondence to: C Cantile (e-mail: carlo.cantile@unipi.it). 0021-9975/$ - see front matter Ó 2020 Elsevier Ltd. All rights reserved. https://doi.org/10.1016/j.jcpa.2020.11.006