A novel genomic region on chromosome 11 associated with fearfulness in dogs

Abstract

The complex phenotypic and genetic nature of anxieties hampers progress in unravelling their molecular etiologies. Dogs present extensive natural variation in fear and anxiety behaviour and could advance the understanding of the molecular background of behaviour due to their unique breeding history and genetic architecture. As dogs live as part of human families under constant care and monitoring, information from their behaviour and experiences are easily available. Here we have studied the genetic background of fearfulness in the Great Dane breed. Dogs were scored and categorised into cases and controls based on the results of the validated owner-completed behavioural survey. A genome-wide association study in a cohort of 124 dogs with and without socialisation as a covariate revealed a genome-wide significant locus on chromosome 11. Whole exome sequencing and whole genome sequencing revealed extensive regions of opposite homozygosity in the same locus on chromosome 11 between the cases and controls with interesting neuronal candidate genes such as MAPK9/JNK2, a known hippocampal regulator of anxiety. Further characterisation of the identified locus will pave the way for molecular understanding of fear in dogs and may provide a natural animal model for human anxieties.

Fig. 1. Distribution of the stranger fear and socialisation scores.

The stranger fear score (a) was available for a total of 124 dogs. The socialisation score (b) was available for 110 dogs included in the stranger fear cohort. Both scores were distributed from 0 to 30 and the dogs with a stranger fear score of 0 were used as controls in the analyses.

Fig. 2. GWAS for stranger fear.

a A Manhattan plot of a quantitative trait analysis (PLINK) illustrates best p-values on chromosome 11 in a genome-wide analysis with no included covariate. b A Manhattan plot of a mixed model association analysis (GenABEL) illustrates best p-values on chromosome 11 in a genome-wide analysis with no included covariate. c A Manhattan plot (PLINK) based on a linear regression association analysis illustrates best p-values on chromosome 11 in a genome-wide analysis with socialisation score as a covariate. d A Manhattan plot of a mixed model association analysis (GenABEL) illustrates best p-values on chromosome 11 in a genome-wide analysis with socialisation score as a covariate. The red intact line refers to a threshold of significance based on Bonferroni corrected values, while the red dashed line indicates a threshold of significance calculated with simpleM. e A genotype plot of a region on chromosome 11 from 0 to 4 Mb indicates a difference in the allelic distributions between cases and controls around the best SNP of the region at 430,548 Mb. f A genotype plot of a region on chromosome 11 from 12.4 to 13.1 Mb indicates a difference in the allelic distributions in the region between cases and controls around the best SNPs of the region at 12,792,149 and 12,810,167 Mb. Light grey and dark blue colours indicate the opposite homotsygote genotypes while the light blue colour indicates a heterotsygote genotype g The associated genomic region includes several candidate genes.

Fig. 3. Whole exome variants between cases and controls on chromosome 11.

Altogether 44 variants were left on chromosome 11 when filtering eight cases against eight controls and the controls against the cases under a dominant model and allowing a maximum of either two cases or two controls to have a deviant genotype. Light grey and dark blue colours indicate the opposite homozygote genotypes while the light blue colour indicates a heterozygote genotype. Extensive regions of opposite homozygosity are observed in the region.