Association Between COMT SNP Variation And Timidity In Golden And Labrador Retrievers

Objective:Timidity is reported to be one of the most common behavioral problems in dogs.Timidity and the relevant neurological processes have especially high heritability.However,the relevant genetic factors and markers associated to this condition are largely unknown.The function of the catechol-O-methyl transferase（COMT）gene has been found to be associated with human fearful or anxious emotions,and the COMT Val158Met polymorphism locus is significantly related to anxious behavior.In the present study,we select four critical single-nucleotide polymorphism（SNP）loci of the canine COMT gene to detect their variations,conjoining the Dog Courage Assessment（DCA）assay and a genotype and haplotype analysis,the correlation between timidity and four single-nucleotide polymorphism（SNP）variations of the COMT gene was investigated in Labrador retrievers（LR）and golden retrievers（GR）,in order to explore whether the COMT genetic variation related to human personality is also of predictive value for timidity in dogs and to provide another scientific reference for understanding the evolution of temperament.Methods:The subjects of this study were selected from 118 dogs in the China Guide Dog Training Centre of Dalian,including two breeds,Labrador Retriever（LR）and Golden Retriever（GR）.The phenotypic test is based on the Dog Courage Assessment（DCA）and genotyping by PCR-sequencing.Population genetic analysis,genotype and haplotype analysis were using Gen AlEx,SPSS,etc.software.Results:1.The principal component analysis（PCA）factor structure of the courage phenotype was invariant between LR and GR.Sex,breed,and age had no statistically significant effect on the timidity of the dogs(F_（1,114）<3.92,P>0.05).All SNP loci detected were in Hardy–Weinberg equilibrium.The COMT:c.482G>A and-1666bpC>G loci showed low levels of polymorphism（PIC<0.25）,and the COMT:c.39A>G and c.216G>A loci showed a medium level of polymorphism（0.25<PIC<0.50）.2.The c.39A>G locus was removed in the subsequent association analysis due to the significant difference between LR and GR in genotype distributions.3.The genotypes and haplotypes of the COMT gene were significantly and highly correlated with the timidity of LR and GR（P<0.05）.The A allele of the COMT:c.216G>A and c.482G>A loci appeared to play a dominant role in the timid behavior of the dogs.Conclusions:the present study demonstrated that COMT genetic variation related to human personality is also of predictive value for timidity in dogs.This result supports and broadens the WARRIOR/WORRIER hypothesis and will have important implications for the understanding of the evolution of temperament in dogs.Additionally,the findings also provide effective genetic markers for evaluating dog temperament at early stage to contribute to human-dog relationships and prevent behavioral problems,such as the suitability of working dogs and prediction of compatibility of pet dogs with their owners.