Download files
Abstract
The Australian Kelpie was generated from three pairs of working Scottish Collie dogs in 1870. The new breed was developed in an effort to ease the growing working demand faced by sheep farming. Like most dog breeds, inbreeding has been common within the Kelpie breed and persistent breeding of champion dogs (popular sire effect) has resulted in the spread of autosomal recessive conditions. One of these, Cerebellar Abiotrophy (CA) results in ataxia, characterized by a head tremor, poor body coordination and high stepping gait. Whole genome association and homozygosity analysis have mapped the CA locus to a 5 Mb region on chromosome 3 and identified a common SNP haplotype shared between all affecteds and some unaffected controls. This region was sequenced on a 454 platform in two affected and one control dogs. A total of 2019 differences were identified homozygous in the two affecteds compared to the control, 17 of which were synonymous substitutions in coding exons and substitutions in the untranslated regions of mRNA. On top of this, a total of 22 differences in introns and intergenic regions with high sequence conservation between other mammals and dogs were identified and investigated as possible causative mutations for CA in Kelpies. PCR and Sanger sequencing were employed to fill in 454 sequencing gaps for a total of 40 coding, non-coding exons and upstream regions of different genes within the candidate region. One intergenic (31674050) deletion conserved between other mammals and dogs was homozygous in the affecteds compared to controls and was predicted to disrupt a HSF2 transcription factor binding site for regulation of neighbouring genes. In addition, sequencing of the DMGDH gene in affected and unaffected control dogs identified a 223 bp insertion upstream of the last exon. This insertion may produce aberrant mRNA splicing and protein truncation, and may be a causative factor in the CA phenotype.