Krisztina Lakatos

Dopamine D4 receptor (DRD4) gene polymorphism is associated with attachment disorganization in infants.

About 15% of one-year-old infants in non-clinical, low-risk and up to 80% in high-risk (eg maltreated) populations show extensive disorganized attachment behavior1, 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 impairment5 and neonatal behavioral organization6 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 (χ2 = 8.66, df = 1, P < 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.

Association between Novelty Seeking and the -521 C/T polymorphism in the promoter region of the DRD4 gene.

Association between the human personality trait ‘Novelty Seeking’ and the polymorphism of the DRD4 gene was first reported by Ebstein1 and Benjamin2 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 < 0.06). examination of this relation in male and female sex groups, however, strengthened the association for females (P < 0.01), but showed no genotypic effect for males.

Infant genotype may moderate sensitivity to maternal affective communications: attachment disorganization, quality of care, and the DRD4 polymorphism.

Abstract Disorganized attachment is an early predictor of the development of psychopathology in childhood and adolescence. Lyons-Ruth, Bronfman, and Parsons (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 (Gervai et al., 2005; Lakatos et al., 2000, 2002). The present collaborative work investigated the interplay between genetic and caregiving contributions to disorganized attachment. Mother–infant dyads (138), from a Hungarian low-social-risk sample (96) and a US high-social-risk sample (42), 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.

Catechol‐O‐methyltransferase Val158Met polymorphism is associated with methylphenidate response in ADHD children

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.

Transmission Disequilibrium Tests Confirm the Link Between DRD4 Gene Polymorphism and Infant Attachment

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  χ 2  = 3.27, df = 1, P = 0.071), and there was a significant non‐transmission of the same allele to securely attached infants (TDT  χ 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  χ 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.

Brain activity during emotion perception: The role of attachment representation

To examine emotional face processing in mothers of different attachment representations, event-related potentials were recorded from 16 mothers during presentation of infant emotion faces with positive, negative or neutral emotional expressions within a three-stimulus oddball paradigm, and frontal asymmetries were assessed. Insecure mothers, as compared to secure ones, showed a more pronounced negativity in the face-sensitive N170 component and a smaller N200 amplitude. Regarding the P300 component, secure mothers showed a stronger response to face stimuli than insecure mothers. No differences were found for frontal asymmetry scores. The results indicate that attachment differences may be related to neuropsychological functioning.

Genotyping the -521C/T functional polymorphism in the promoter region of dopamine D4 receptor (DRD4) gene.

The ‐521C/T single nucleotide polymorphism (SNP) in the promoter region of the dopamine D4 receptor gene (DRD4) has recently been detected in oriental (Japanese) individuals and related to novelty seeking and schizophrenia. Here, we report the analysis of the ‐521C/T polymorphism in a Caucasian (Hungarian) population using two independent genotyping methods. The polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) procedure utilized the FspI restriction site around the ‐521 position. An additional, nonpolymorphic cleavage site was also included into the amplified region to serve as an internal standard for verifying the completion of the digestion. As another independent method, a tetraprimer system for single‐tube allele‐specific PCR (SAS‐PCR) was developed to generate ‐521C and ‐521T specific PCR products with different fragment sizes. Consequently, genotyping with SAS‐PCR is based on the gel‐electrophoretic separation of the allele‐specific double‐stranded DNA (dsDNA) fragments. 119 healthy Hungarian individuals were genotyped for ‐521C/T polymorphism of the dopamine D4 promoter region, using both methods. Similar allele frequencies were found (‐521C allele: 0.43; ‐521T allele: 0.57) as reported earlier for the Japanese population.

Association between dopamine D4 receptor (DRD4) gene polymorphisms and novelty-elicited auditory event-related potentials in preschool children

We investigated associations of the exon III repeat and the -521 C/T polymorphisms of the DRD4 gene with novelty-elicited auditory ERP components and behavioral resistance to distraction in 57 healthy, typically developing 6-year-old children. Dopamine-related gene polymorphisms have previously been linked to processes directing focused attention. We did not find associations between the 7-repeat allele or the T.7 haplotype and the early ERP responses suggesting that DRD4 polymorphisms did not affect the detection of novelty. However, the same polymorphisms affected the late negative components (LN1 and LN2). Late negativities elicited by deviant and novel sounds have been regarded as reflecting reorientation after distraction or additional processing of new information. Children carrying the T.7 haplotype had significantly smaller LN1 and LN2 amplitudes. The presence of the T.7 haplotype also significantly enhanced behavioral resistance to distraction. We suggest that less distraction in T.7 carriers led to less reorienting activity (reflected by the LN components). We also speculate that activation of less sensitive and fewer D4 receptors (as with the T.7 haplotype) is less effective in modulating GABAergic inhibitory signaling, which in turn is reflected in smaller LN amplitudes.

Comment on "No association of dopamine D4 receptor (DRD4) and -?521 C/T promoter polymorphisms with infant attachment disorganization" by M.J. Bakermans-Kranenburg and M.H. van IJzendoorn

In the discussion section of their paper, Bakermans-Kranenburg and van IJzendoorn (2004, this issue) briefly refer to our recent manuscript accepted for publication (Gervai et al., 2004, this issue) by interpreting the results of our paper as lending some support to their non-replication finding. While we accept their finding as a genuine non-replication (within the limits of their study), we feel that it is important to raise concerns about the adequacy and appropriateness of their interpretations of our own data and analyses. We also would like to raise some further concerns about the authors’ interpretations of their own results. We offer several reasons why this failure to replicate, although offering valuable additional data, does not necessarily invalidate or refute the Gervai et al. results. Rather, the two sets of results must be seen together as pointing to specific further studies that need to be conducted to clarify the genetic and developmental mechanisms operating in this domain. The Gervai et al. paper describes two sets of further results from the Budapest study :

A pilot study of early onset obsessive-compulsive disorder: Symptom dimensions and association analysis with polymorphisms of the serotonin transporter gene

Our aim was to introduce more homogenous phenotypes for studying genetic variations in the clinically heterogeneous obsessive compulsive disorder (OCD) beside classical case-control analysis. Symptoms were assessed with Childrens Yale-Brown Obsessive Compulsive Scale (CY-BOCS), and principle component analysis of the lifetime symptom categories yielded four factors (Cleaning, Obsessive, Compulsive, Sexual). The comparison of serotonin transporter linked polymorphic region (5-HTTLPR) in 102 OCD patients and 223 controls showed an increased L-allele frequency but no difference was observed when rs25531 was included. Intronic variants of the serotonin transporter gene did not show association with either OCD, nor with the obtained factors.