About 15% of one-year-old infants in non-clinical, lowrisk and up to 80% in high-risk (eg maltreated) populations show extensive disorganized attachment behavior 1,2 in the Strange Situation Test. 3 It has also been reported that disorganization of early attachment is a major risk factor for the development of childhood behavior problems. 4 The collapse of organized attachment strategy has been explained primarily by inappropriate caregiving, but recently, the contribution of child factors such as neurological impairment 5 and neonatal behavioral organization 6 has also been suggested. Here we report an association between the DRD4 III exon 48-bp repeat polymorphism and attachment disorganization. Attachment behavior of 90 infants was tested in the Strange Situation and they were independently genotyped for the number of the 48-bp repeats by polymerase chain reaction (PCR). The 7-repeat allele was represented with a significantly higher frequency in infants classified as disorganized compared to non-disorganized infants: 12 of 17 (71%) vs 21 of 73 (29%) had at least one 7-repeat allele ( 2 = 8.66, df = 1, P Ͻ 0.005). The estimated relative risk for disorganized attachment among children carrying the 7-repeat allele was 4.15. We suggest that, in non-clinical, low-social-risk populations, having a 7-repeat allele predisposes infants to attachment disorganization. Molecular Psychiatry (2000) 5, 633-637.The first publications on association between DRD4 receptor III exon polymorphism and the adult personality trait, Novelty Seeking, 7,8 were soon followed by reports demonstrating associations of the same polymorphism with pathological impulsive, compulsive behavior and substance abuse in adults 9-11 and attention deficit hyperactivity disorder (ADHD) in children. 12,13 There is a growing body of evidence linking maladaptive behavioral problems in children (and extending into adulthood) with the 7-repeat allele of the DRD4 gene.Early attachment between infant and caregiver has been considered essential for survival in the human species. 14 Attachment theory provided a widely used framework for explaining influences of early social experiences on normal and problematic development of personality. 15 Ainsworth and colleagues 3 devised an experimental procedure, the Strange Situation, and described marked individual differences in infants' coping with the stress elicited by the two brief separations from the caregiver. The three basic, coherently organized patterns of infant behavior after reunion (secure, insecure-avoidant, insecure-resistant, see Methods) have been regarded as adaptations to the experienced differences in caregiving. 16 About 15% of infants in non-clinical, low-risk and up to 80% in highsocial-risk (eg maltreated) populations were difficult to fit in the three established categories. These 'atypical' infants showed incoherent, contradictory behavior in the presence of the caregiver as if their behavioral strategy collapsed under the stress of the Strange Situation. A new organizational dimension of at...

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.

Knowledge about the functional status of the frontal cortex in infancy is limited. This study investigated the effects of polymorphisms in four dopamine system genes on performance in a task developed to assess such functioning, the Freeze-Frame task, at 9 months of age. Polymorphisms in the catechol-O-methyltransferase (COMT) and the dopamine D4 receptor (DRD4) genes are likely to impact directly on the functioning of the frontal cortex, whereas polymorphisms in the dopamine D2 receptor (DRD2) and dopamine transporter (DAT1) genes might influence frontal cortex functioning indirectly via strong frontostriatal connections. A significant effect of the COMT valine(1)methionine (Val 158 Met) polymorphism was found. Infants with the Met/Met genotype were significantly less distractible than infants with the Val/Val genotype in Freeze-Frame trials presenting an engaging central stimulus. In addition, there was an interaction with the DAT1 3; variable number of tandem repeats polymorphism; the COMT effect was present only in infants who did not have two copies of the DAT1 10-repeat allele. These findings indicate that dopaminergic polymorphisms affect selective aspects of attention as early as infancy and further validate the Freeze-Frame task as a frontal cortex task.

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.

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...

Methylphenidate is the most frequently prescribed drug in the treatment of attention deficit hyperactivity disorder (ADHD) but it is not effective in every case. Therefore, identifying genetic and/or biological markers predicting drug-response is increasingly important. Here we present a case-control study and pharmacogenetic association analyses in ADHD investigating three dopaminergic polymorphisms. Previous studies suggested variable number of tandem repeats (VNTR) in the dopamine D4 receptor (DRD4) and the dopamine transporter (DAT1) genes as genetic risk factors for ADHD and as possible markers of methylphenidate response. Our results did not indicate substantial involvement of these two VNTRs in ADHD, however, both the case-control and the pharmacogenetic analyses showed significant role of the high activity Val-allele of cathecol-O-methyltransferase (COMT) Val158Met polymorphism in our ADHD population. The Val-allele was more frequent in the ADHD group (n = 173) compared to the healthy population (P = 0.016). The categorical analysis of 90 responders versus 32 non-responders showed an association between the Val-allele or Val/Val genotype and good methylphenidate response (P = 0.009 and P = 0.034, respectively). Analyzing symptom severity as a continuous trait, significant interaction of COMT genotype and methylphenidate was found on the Hyperactivity-Impulsivity scale (P = 0.044). Symptom severity scores of all three genotype groups decreased following methylphenidate administration (P < 0.001), however Val/Val homozygote children had significantly less severe symptoms than those with Met/Met genotype after treatment (P = 0.015). This interaction might reflect the regulatory effect of COMT dominated prefrontal dopamine transmission on subcortical dopamine systems, which are the actual site of methylphenidate action.