Characterisation of canine KCNIP4: a novel gene for cerebellar ataxia identified by whole-genome sequencing of two affected Norwegian Buhund dogs

A form of hereditary cerebellar ataxia has recently been described in the Norwegian Buhund dog breed. This study aimed to find the genetic cause of the disease. Whole-genome sequencing of two Norwegian Buhund siblings diagnosed with progressive cerebellar ataxia was carried out, and sequences compared with whole genome sequences of dogs of other breeds to filter benign common variants. Nine variants predicted to be deleterious segregated among the genomes in concordance with an autosomal recessive mode of inheritance, one of which segregated within the breed when genotyped in additional Norwegian Buhunds. The variant identified, a T to C single nucleotide polymorphism (SNP), is predicted to cause a tryptophan to arginine substitution in a highly conserved region of the potassium voltage-gated channel interacting protein KCNIP4. Evaluation of protein expression through western blot and immunohistochemical analysis using cerebellum tissue of affected and control dogs demonstrated that the mutation causes a dramatic reduction of KCNIP4 protein expression. The voltage-gated potassium channel protein KCND3 has previously been implicated in spinocerebellar ataxia, and our findings suggest that the Kv4 channel complex KCNIP accessory subunits also have an essential role in voltage-gated potassium channel function in the cerebellum and should be investigated as potential candidate genes for cerebellar ataxia in future canine and human studies.