Epsilon Open Archive

Abstract

A novel neurological syndrome, mitochondrially inherited sensory ataxic neuropathy (SAN), was discovered in Golden Retriever dogs in Sweden. The purpose of the work described in the present thesis was to investigate the phenotype, clinical course and genotype of this syndrome by clinical, neurological and pathological examination of affected dogs, as well as to determine the mode of inheritance and identify the causative mutation. Mitochondrially inherited SAN in Golden Retriever dogs has an insidious onset during puppyhood. Affected dogs develop ataxia and dysmetria, with abnormal postural reactions and depressed spinal reflexes. The disease has a chronic, slowly progressive clinical course. Of the affected dogs investigated within the scope of this thesis, none became non-ambulatory or died spontaneously during the study period. However, about half of the affected dogs were euthanized because of neurological impairment before attaining 4 years of age. Post mortem examinations of affected dogs revealed degenerative changes in both the central and the peripheral nervous system. A chronic active central–peripheral axonopathy, neuroaxonal dystrophy-like alterations in spinal cord and brainstem, and a neuron-sparing encephalopathy with spongiosis in the basal nuclei were the most prominent findings. A maternal mode of inheritance was concluded from pedigree analysis, indicating a causative mutation in the mitochondrial DNA. Laboratory data confirmed that affected dogs had malfunctioning mitochondria. A single base-pair deletion in the mitochondrial tRNATyr gene was found and proven to be pathogenic. In summary, canine SAN is a slowly progressive neurodegenerative disease with onset in puppyhood. The disease is maternally inherited and is caused by a mutation in the mitochondrial tRNATyr gene.