The oxytocin system has a crucial role in human sociality; several results prove that polymorphisms of the oxytocin receptor gene are related to complex social behaviors in humans. Dogs' parallel evolution with humans and their adaptation to the human environment has made them a useful species to model human social interactions. Previous research indicates that dogs are eligible models for behavioral genetic research, as well. Based on these previous findings, our research investigated associations between human directed social behaviors and two newly described (−212AG, 19131AG) and one known (rs8679684) single nucleotide polymorphisms (SNPs) in the regulatory regions (5′ and 3′ UTR) of the oxytocin receptor gene in German Shepherd (N = 104) and Border Collie (N = 103) dogs. Dogs' behavior traits have been estimated in a newly developed test series consisting of five episodes: Greeting by a stranger, Separation from the owner, Problem solving, Threatening approach, Hiding of the owner. Buccal samples were collected and DNA was isolated using standard protocols. SNPs in the 3′ and 5′ UTR regions were analyzed by polymerase chain reaction based techniques followed by subsequent electrophoresis analysis. The gene–behavior association analysis suggests that oxytocin receptor gene polymorphisms have an impact in both breeds on (i) proximity seeking towards an unfamiliar person, as well as their owner, and on (ii) how friendly dogs behave towards strangers, although the mediating molecular regulatory mechanisms are yet unknown. Based on these results, we conclude that similarly to humans, the social behavior of dogs towards humans is influenced by the oxytocin system.

Effects of DRD4 and 5-HTTLPR length polymorphisms have been reported on neonatal and infant temperament as well as adult personality traits. The 7-repeat form of the DRD4 III exon VNTR polymorphism has been associated with childhood ADHD, and recently we have reported its link with attachment disorganization in a nonclinical population of infants. Here, we report associations of these polymorphisms with infant temperament at 12 months of age. Maternal accounts of temperament and observed response to novelty were investigated for 90 infants, who were independently genotyped for the DRD4 III exon, and for 5-HTT-linked promoter region length polymorphisms. Maternal rating of temperament was not affected by these polymorphisms, but we found combined genotype effects for infants' observed responses to a novel, anxiety-provoking stimulus: the appearance of, and approach by, a stranger. Infants with at least one copy of both the 7-repeat DRD4 allele and the long variant of 5-HTTLPR (7 + , l/l&l/s) responded with significantly less anxiety than infants with other genotypes. However, infants with the 7-repeat DRD4 allele and homozygous for the short form of 5-HTTLPR (7 + , s/s) showed more anxiety and resistance to the stranger's initiation of interaction. These genotype effects were not redundant with the previously reported association between the 7-repeat DRD4 allele and disorganized attachment behavior. Although both temperament and attachment behavior were affected by the DRD4 repeat polymorphism, the effect on temperament measures was modified by the infants' 5-HTTLPR genotype. Molecular Psychiatry (2003) 8, 90-97.

A variable number of tandem repeats (VNTR) polymorphism in exon 3 of the human dopamine D4 receptor gene (DRD4) has been associated with attention deficit hyperactivity disorder (ADHD). Rodents possess no analogous repeat sequence, whereas a similar tandem repeat polymorphism of the DRD4 gene was identified in dogs, horses and chimpanzees. Here, we present a genetic association study of the DRD4 VNTR and the activity-impulsivity dimension of the recently validated dog-ADHD Rating Scale. To avoid false positives arising from population stratification, a single breed of dogs (German shepherd) was studied. Two DRD4 alleles (referred to as 2 and 3a) were detected in this breed, and genotype frequencies were in Hardy-Weinberg equilibrium. For modelling distinct environmental conditions, 'pet' and 'police' German shepherds were characterized. Police German shepherds possessing at least one 3a allele showed significantly higher scores in the activity-impulsivity dimension of the dog-ADHD Rating Scale than dogs without this allele (P = 0.0180). This difference was not significant in pet German shepherds. To the best of our knowledge, this is the first report of an association between a candidate gene and a behaviour trait in dogs, and it reinforces the functional role of DRD4 exon 3 polymorphism.

The study suggests a gene-environment interaction whereby biological determinants of attachment disorganization are moderated by social experiences. Different pathways of the development of attachment disorganization are discussed based on a bio-behavioral model of development.

Disorganized attachment is an early predictor of the development of psychopathology in childhood and adolescence. Lyons-Ruth et al. (1999) developed the AMBIANCE coding scheme to assess disrupted communication between mother and infant, and reported the link between maternal behavior and disorganized attachment. The Hungarian group found an association between a polymorphism of the DRD4 gene and disorganized attachment (Lakatos et al., 2000;Gervai et al., 2005). The present collaborative work investigated the interplay between genetic and caregiving contributions to disorganized attachment. 138 mother-infant dyads, 96 from a Hungarian low-social-risk sample and 42 from a US high-social-risk sample, were assessed for infant disorganized attachment behavior, for DRD4 gene polymorphisms, and for disrupted forms of maternal affective communication with the infant. In accord with literature reports, we found a robust main effect of maternal AMBIANCE scores on infant disorganization. However, this relation held only for the majority of infants who carried the short form of the DRD4 allele. Among carriers of the 7-repeat DRD4 allele, there was no relation between quality of maternal communication and infant disorganization. This interaction effect was independent of degree of social risk and maternal DRD4 genotype.

Keywords: DRD4 exon III VNTR polymorphism; −521 C/T promoter polymorphism; attachment disorganization; dopamineIn non-clinical low-risk populations 15% of infants show disorganized attachment behavior 1,2 with their caregivers in the Strange Situation, 3 a mildly stressful laboratory procedure testing infants' ability to cope with separation anxiety. Disorganization of early attachment has been primarily ascribed to inadequate parenting, 2,4,5 and has been associated with childhood behavior problems 6,7 and adolescent psychopathological tendencies. 5We have recently reported an association between the DRD4 exon III 48 basepair repeat polymorphism and disorganization of infants' attachment behavior towards their mother in a low-social-risk group of 1-year-old infants: 8 the risk for disorganized attachment among infants carrying the 7-repeat allele was fourfold. Here we report further evidence for the involvement of the dopamine D4 receptor gene in attachment disorganization. The same group of infants was genotyped for the functional −521 C/T single nucleotide polymorphism (SNP) in the upstream regulatory region of the DRD4 gene 9 in order to test the association with attachment disorganization both alone and in interaction with the DRD4 exon III 7-repeat allele. While the −521 C/T genotype itself had no effect on attachment status ( 2 = 0.41, df = 2, P = 0.82), there was an interaction between the structural 48-bp repeat polymorphism and the −521 C/T promoter polymorphism: the association between disorganized attachment and the 7-repeat allele was enhanced in the presence of the −521 T allele ( 2 = 6.61 and 6.67, df = 1, P Ͻ 0.025 for CT and TT genotypes, respectively). In the presence of both risk alleles the odds ratio for disorganized attachment increased tenfold. This result supports our previous postulation that the DRD4 gene plays a role in the development of attachment behavior in low-risk, non-clinical populations. Molecular Psychiatry (2002) 7, 27-31. DOI: 10.1038/ sj/mp/4000986The role of dopamine receptor and transporter genes in both normal traits and psychopathology has been intensively studied in the past decade.10,11 One of the most frequently targeted candidate genes is the highly polymorphic dopamine D4 receptor (DRD4) gene. 12,13A 48-bp VNTR polymorphism has been identified in exon III with the 4-repeat allele being the most common, followed by the 7-repeat form 14 which is 2-3 times less potent in dopamine-mediated coupling to adenylyl cyclase than the 4-repeat form.15 Evidence linking the 7-repeat allele of the DRD4 gene with infant temperament traits of negative emotionality [16][17][18] and maladaptive behavioral problems, especially attention deficit hyperactivity disorder (ADHD) in children, is being accumulated. 19-21Recently, we found that the 7-repeat DRD4 allele was 2.5 times more frequent among one-year-old infants who showed disorganized attachment behavior, ie were unable to cope with the stress elicited by the two brief separations from the caregiver in the Strange Situation exper...

Association between the human personality trait 'Novelty Seeking' and the polymorphism of the DRD4 gene was first reported by Ebstein 1 and Benjamin 2 in 1996. This was soon followed by replication studies in various ethnic groups and by studying the role of other neurotransmitter receptor and transporter genes in the genetic determination of human temperament. More recently, several polymorphic sites of the upstream regulatory region of the DRD4 gene have been described.3 Among these the −521 C/T single nucleotide polymorphism (SNP) was shown to be associated with the Novelty Seeking (NS) scores of the Temperament and Character Inventory (TCI) in a Japanese male population. 4 We have investigated the −521 C/T SNP polymorphism in a Caucasian (Hungarian) population, 5 and here we report a replication of the Japanese findings, in an association study involving 109 healthy Hungarian volunteers. We found a weak association between NS and CC vs CT or TT genotypes (P Ͻ 0.06). Examination of this relation in male and female sex groups, however, strengthened the association for females (P Ͻ 0.01), but showed no genotypic effect for males. Molecular Psychiatry (2001) 6, 35-38. Human temperament, as measured by various selfreport questionnaires including TPQ (or a new version known as TCI) 6 and NEO-PI-R, 7 was shown to have considerable inherited components.8 Novelty Seeking (NS) is one of the four dimensions in the psychobiological model of temperament, which are thought to be independently heritable, and manifested from an early age. 9 The NS scale was designed to measure exploratory, impulsive and extravagant behavior, and has been related to the dopamine system by Cloninger. Searching for association between common genetic polymorphisms and specific personality traits, recent studies have concentrated on distinct candidate genes. First, the variable number of 48-bp repeats (VNTR) in the third exon of the human dopamine D4 receptor gene (DRD4) was shown to be correlated with the personality trait of Novelty Seeking, as measured by the TPQ 1 or the NEO-PI-R, 2 although the replications of the initial findings have been controversial. [10][11][12][13] Further studies concerning the regulatory region of the genes encoding receptors and transporters involved in neurotransmission revealed associations between a novel polymorphism of the DRD4 promoter region and NS in Japanese subjects. 4 This polymorphism is a CϾT substitution in a CpG island at one end of a cell-type specific regulatory element, between −591 and −123 bp relative to the first nucleotide of the DRD4 gene.14 Using a transient expression system, the −521 T allele was shown to be approximately 40% less active than the −521 C variant in a human retinoblastoma cell line, 4,15 suggesting the relevance of this polymorphism to the dopaminergic system. Moreover, a significantly higher frequency of the CC genotype was found among schizophrenic patients. 15Previously we have described the distribution of −521 C and −521 T alleles in a nonclinical Hungarian populati...

Following up the results of a previous population association study (Lakatos et al. [2000: Mol Psychiatry 5:633-637; Lakatos et al. [2002: Mol Psychiatry 7:27-31]) by analyses based on parental genetic data confirmed the link between infant attachment and the dopamine D4 receptor (DRD4) gene. Extended transmission disequilibrium tests (ETDT) were performed to determine whether biased transmission of exon III 48 basepair repeat alleles occurred to infants displaying disorganized and secure attachment behavior with their mothers. The overall allele-wise TDTs were significant for both groups (P = 0.038 and 0.020, respectively): a trend for preferential transmission of the seven-repeat allele to disorganized infants was observed (TDT(chi)(2) = 3.27, df = 1, P = 0.071), and there was a significant non-transmission of the same allele to securely attached infants (TDT(chi)(2) = 6.00, df = 1, P = 0.014). Analysis of haplotypes of the exon III repeat and the -521 C/T promoter polymorphisms in family trios showed that the transmission bias in the larger secure group was due to the low-rate transmission of the T.7 haplotype containing both the seven-repeat and the -521 T alleles (TDT(chi)(2) = 4.46, df = 1, P = 0.035). This suggests that not carrying the T.7 haplotype of the DRD4 gene may act as a resilience factor in the optimal development of early attachment.