Polymorphism analysis of tyrosine hydroxylase gene variable number of tandem repeats in various Korean dogs

Although humans and canines exhibit similar behavioral features, it is not easy to identify the corresponding behavioral phenotypes. The variable number of tandem repeats (VNTR) in intron 4 of the tyrosine hydroxylase ( TH ) gene is related to two characteristics, namely, impulsive activity and inattention. The TH genes are defined by three genotypes: type 1/1 comprises a single copy of TH VNTR; type 1/2 is heterozygote for both short allele and long allele; and type 2/2 is the doubled form of TH VNTR, which leads to inattention and impulsive actions. The 1/1 and 1/2 genotype have been identified as biomarkers for concentration and impulsive action. Therefore, we performed PCR amplification to detect the 1/2 genotypes in three canine breeds from Korea: Sapsaree (49), Poongsan (18), and Jindo (20). Our results indicate that the Sapsaree dog carries 27 % of the 2/2 genotype, 59 % of the 1/2 genotype, and 14 % of the 1/1 genotype; the Poongsan dog carries 11 % of the 2/2 genotype, 22 % of 1/2 genotype, and 67 % of 1/1 genotype; whereas the Jindo dog carries 10 % of the 2/2 genotype, 40 % of the 1/2 genotype, and 50 % of the 1/1 genotype. Taken together, our data indicate that the Jindo, Poongsan, and Sapsaree dogs harbor decreasing amounts of phenotypes responsible for inattention and impulsive behavior, in that order. Additionally, the Sapsaree genes harbor higher amounts of the 1/2 genotype than the Jindo and Poongsan genes, respectively.