917: Genetic Determinants of Canine Epilepsy in the Border Collie and the Staffordshire Bull Terrier

Project Summary

Canine epilepsy is a recurrent neurological condition and is a growing problem in many breeds of dog with some breeds having a higher incidence of the condition than others. To date, only one genetic mutation has been identified in dogs; the Epm2b mutation as described by Lohi et al. in 2005. Staffordshire Bull Terriers suffer with an autosomal recessive disorder known as L2-hydroxyglutaric aciduria (L2-HGA) which presents and is treated in the same way as epilepsy, but is not true epilepsy. We genotyped a cohort of 'epileptic' Staffordshire Bull Terriers and found that only 1 dog was L2HGA positive and 8 were carriers out of 66 'epileptics', indicating that the current breeding strategy is working and that the condition is being reduced in the Staffordshire Bull Terrier population. All controls were found to be homozygous for the 'normal' alleles and screening of the entire epileptic cohort (1120 dogs) confirmed this condition to be specific to the Staffordshire Bull Terrier, as it was not found in any other breed in our cohort. Genome wide association studies (GWAS) conducted on 68 Border Collie cases and 68 controls and 24 Staffordshire Bull Terrier cases and 24 controls identified two and four potential regions of association, respectively. Some regions contain candidate genes which have been found to be associated with certain types of human epilepsy, and as such, require further investigation to determine whether the genes of interest could be used as markers for epilepsy in the future. In addition to GWAS, a candidate gene study has identified a number of allele, genotype and haplotype associations in multiple breeds, suggesting a common cause of epilepsy in multiple breeds of dog. We have identified that canine epilepsy has common causative genes in multiple breeds of dog, although further investigations are needed to determine the causative alleles. We have confirmed that strategic breeding programmes can reduce the number of carrier dogs for autosomal recessive conditions, as shown by the L2HGA screening, and that this condition is specific to Staffordshire Bull Terriers. We have also shown that it is possible to identify regions of chromosomal association with disease in small numbers of samples (24 cases and 24 controls) although for some breeds, larger numbers of samples are required for such associations to be made, as demonstrated by the Border Collie.

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