Identification and characterisation of a mutation associated with cerebellar ataxia in the Norwegian Buhund dog breed

Presenter Christopher Jenkins
Authors Jenkins CA (1), Kalmar L (3), Mari L (2), Schofield EC (1), Mellersh CS (1), De Risio L (2, 4), Ricketts SL (1, 4)
Affiliations 1. Kennel Club Genetics Centre, Animal Health Trust, 2. Neurology/ Neurosurgery Service, Centre for Small Animal Studies, Animal Health Trust, 3. Department of Veterinary Medicine, University of Cambridge, 4. Authors contributed equally
Presentation Type Talk


Inherited ataxias are typically incurable and lack disease-modifying treatments. Four Norwegian Buhunds were diagnosed with cerebellar ataxia at the Animal Health Trust. Pedigree analysis was suggestive of an autosomal recessive mode of inheritance, which is typical of inherited canine ataxias. The causal variant for ataxia in these dogs was hypothesised to be private to the breed. Whole genome sequence (WGS) was obtained for two sibling cases, which were compared to WGS from 405 dogs of other breeds. The WGS used included 44 which were generated for the study of other diseases in our laboratory, and 361 additional WGS which are part of the Dog Biomedical Variant Database Consortium. Filtering out benign variants left nine that were present only in the cases and predicted to directly affect a protein coding sequence or alter a transcript. These were assessed in 14 related and unrelated Buhunds, leaving one variant that fully segregated with the disease. Its association with ataxia was confirmed by typing in an extended set of 148 Buhunds containing two additional cases, and its absence in 359 dogs of 122 other breeds. This research has resulted in the development of a DNA test enabling breeders to avoid producing affected dogs. Importantly, the causal mutation is within a gene not previously reported to be associated with ataxia in any species. A combination of approaches was used to characterise this gene in the dog, as the current CanFam 3.1 annotation is incorrect. The gene is highly conserved and, in humans and mice, encodes multiple transcripts with alternative first exons. Expression of multiple transcripts in the canine cerebellum was confirmed through RNA sequencing, and through RT-PCR of samples from two Norwegian Buhund cases and five unaffected dogs of other breeds. RT-qPCR analysis and in-silico protein modelling have been used to further investigate the mutation’s effect on RNA expression and protein stability.