Canine Tyrosine Hydroxylase (TH) Gene and Dopamine .BETA.-Hydroxylase (DBH) Gene: Their Sequences, Genetic Polymorphisms, and Diversities among Five Different Dog Breeds

Abstract

ABSTRACT. Dopamine and noradrenaline are catecholamine neurotransmitters that are produced by biosynthetic enzymes such as tyrosine hydroxylase (TH) and dopamine β -hydroxylase (DBH). As a first step to elucidate the genetic background of canine behavioral traits, we selected these genes as targets and sequenced these canine genes, and found that both were highly homologous with those of human beings. Then brain cDNAs derived from ten unrelated Beagles were used to search for polymorphisms in these genes. Four single nucleotide polymorphisms (SNPs) (C97T, G168A, G180A and C264T), one of which (C97T) will cause amino acid substitution in the TH gene, and two SNPs (C789A and A1819G), both of which will cause amino acid substitutions in the DBH gene were identified. The allelic frequencies among five dog breeds (47 Golden Retrievers, 41 Labrador Retrievers, 40 Malteses, 26 Miniature Schnauzers, and 39 Shibas) were examined and found to have significant variation between them with regards to all these SNPs, except for C97T in the TH gene and A1819G in the DBH gene. The polymorphisms of C97T and A1819G were found only in the Shiba. The present results suggest that the polymorphisms of the genes encoding catecholamine biosynthetic enzymes may become important markers for examining the genetic background of behavioral characteristics in dogs. KEY WORDS: breed difference, DBH, dog, polymorphism, TH.J. Vet. Med. Sci. 67(9): 861-867, 2005 Since a genetic polymorphism related to the dopamine D4 receptor (DRD4) was postulated to be related to the "novelty seeking" behavior [2, 9], numerous genetic markers for such behavioral traits have been researched in the human psychiatric field [1,5,6,17,23,30]. Most of these markers are on genes coding for neurotransmitters, neuropeptides, neurotropic factors or transcription factors, as well as their receptors, synthetic enzymes and metabolic enzymes. Such research is based on the fundamental concept that one's personality is formed from the activity and/or turnover of such components of the hypothalamo-limbic system. Although this system is thought to be conserved in mammals, few polymorphic markers that could be responsible for the behavioral traits or temperament in the other mammals have been listed up. This situation is no exception in case of dogs even though we can now access various canine genome resources for linkage analysis, i.e. the 1 Mb resolution radiation hybrid map of the canine genome [10], the map of 4249 genetic markers featuring one marker every 900kb [3]. Therefore we have tried to search genetic markers that would be related to the behavioral traits in dogs and so far found some single nucleotide polymorphisms (SNPs) in neurotransmitter-related genes [12,19,20].In this study tyrosine hydroxylase (TH) and dopamine β -hydroxylase (DBH) genes were selected for their possible relation to canine behavioral traits. We sequenced these genes, and searched for genetic polymorphisms in these genes. The TH and DBH are biosynthetic enzymes for the synthesis of catecholam...

Sequences and Polymorphisms of the Canine Monoamine Transporter Genes SLC6A2, SLC6A3, and SLC6A4 among Five Dog Breeds

“…The full lengths of the coding regions of the canine SLC6A2, SLC6A3, and SLC6A4 genes were sequenced using consensus primers designed from registered sequences of other species [GenBank accession numbers SLC6A2: NM_001043 (human), NM_009209 (mouse), SLC6A3: NM_001044 (human), NM_010020 (mouse), SLC6A4: NM_001045 (human), NM_010484 (mouse)] and complementary DNA (cDNA) obtained by reverse-transcription of brain mRNA from a Beagle, as described previously [6,[14][15][16]22]. This resulted in the determination of nucleotide sequences with open reading frames of 1854 bp (SLC6A2), 1854 bp (SLC6A3), and 1893 bp (SLC6A4).…”

“…Based on this concept, we examined the genetic variation of the identified polymorphisms among dog breeds as follows. We used 190 samples of peripheral blood as our previous studies [6,[14][15][16]22]. These were obtained from five different dog breeds selected for their popularity in Japan and breed-specific temperament traits [24] (Golden Retriever, n=46; Labrador Retriever, n=41; Maltese, n=40; Miniature Schnauzer, n=25; and Shiba, n=38).…”

Identifying Novel Polymorphisms in the Canine Tryptophan Hydroxylase 2 Gene

“…The original tryptophan hydroxylase, TPH1, is involved in serotonin synthesis within the brain during some developmental stages, in addition to within the pineal gland and peripheral tissues [10]. In this study, we sought to identify genes that contribute to temperaments, although one report concerning this was published during the course of present study that suggests that the TPH1 gene has no polymorphisms based on a genomic DNA analysis [16].…”

“…To identify polymorphisms in the TPH1 and TPH2 genes, we first sequenced the coding regions using the brain cDNAs of ten unrelated beagles to be used as a template for PCR (these samples were prepared for our previous studies [3,8,9,11,16]). Consensus primers were designed by referring to the gene sequences of other mammals and were used for each PCR.…”

“…To assess the genotype variation of the five SNPs, peripheral blood samples were obtained from 192 dogs of the five different breeds used in the previous studies (Golden Retriever, n=47; Labrador Retriever, n= 41; Maltese, n= 39; Miniature Schnauzer, n= 26; and Shiba, n= 39) [3,8,9,11,16]. To genotype the five SNPs, PCR was performed in a volume of 50 µl of reaction mixtures using the following conditions and the primers summarized in Table 1 with 10 to 20 ng of canine genomic DNA as the template.…”