Maria Sasvari-Szekely

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.

Real-time PCR quantification of human complement C4A and C4B genes

BackgroundThe fourth component of human complement (C4), an essential factor of the innate immunity, is represented as two isoforms (C4A and C4B) in the genome. Although these genes differ only in 5 nucleotides, the encoded C4A and C4B proteins are functionally different. Based on phenotypic determination, unbalanced production of C4A and C4B is associated with several diseases, such as systemic lupus erythematosus, type 1 diabetes, several autoimmune diseases, moreover with higher morbidity and mortality of myocardial infarction and increased susceptibility for bacterial infections. Despite of this major clinical relevance, only low throughput, time and labor intensive methods have been used so far for the quantification of C4A and C4B genes.ResultsA novel quantitative real-time PCR (qPCR) technique was developed for rapid and accurate quantification of the C4A and C4B genes applying a duplex, TaqMan based methodology. The reliable, single-step analysis provides the determination of the copy number of the C4A and C4B genes applying a wide range of DNA template concentration (0.3–300 ng genomic DNA). The developed qPCR was applied to determine C4A and C4B gene dosages in a healthy Hungarian population (N = 118). The obtained data were compared to the results of an earlier study of the same population. Moreover a set of 33 samples were analyzed by two independent methods. No significant difference was observed between the gene dosages determined by the employed techniques demonstrating the reliability of the novel qPCR methodology. A Microsoft Excel worksheet and a DOS executable are also provided for simple and automated evaluation of the measured data.ConclusionThis report describes a novel real-time PCR method for single-step quantification of C4A and C4B genes. The developed technique could facilitate studies investigating disease association of different C4 isotypes.

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.

Association between depression and the Gln460Arg polymorphism of P2RX7 gene: a dimensional approach.

The P2RX7 gene (coding for P2X7 purinergic receptor) has been suggested as a novel candidate gene for major depressive disorder (MDD) and bipolar disorder (BPD). The proposed risk allele (G‐allele) of the rs2230912 polymorphism results in an amino acid change at the 460th position, marking this genetic variation a possibly functional one. Here we present a case–control analysis of 171 patients diagnosed with MDD or BPD and 178 controls, as well as a dimensional approach using the Hospital Anxiety and Depression Scale (HADS) for studying the Gln460Arg polymorphism of the P2RX7 gene as a genetic risk factor in depression. While case–control analysis did not show significant difference between the groups, a significant association was found between the P2RX7 polymorphism and the HADS scales in the clinical group (MANOVA P = 0.001). Both anxiety and depression scores increased as the number of G‐allele increased in the genotype groups (ANOVA for HADS‐anxiety: P = 0.01, HADS‐depression: P < 0.001). A significant interaction of clinical status and the P2RX7 polymorphism was also found for the depression scale (MANOVA P = 0.025, subsequent ANOVA for anxiety: P = 0.252; depression: P = 0.002). Whereas patients with G‐allele‐present genotypes showed more elevated depression scores, level of depression in the control group was not affected by the P2RX7 genotype. In conclusion, case–control analysis did not reveal significant results, but using a symptom severity scale we could support the association between depressive disorder and the G‐allele of the Gln460Arg polymorphism in the P2RX7 gene.

Human personality dimensions of persistence and harm avoidance associated with DRD4 and 5-HTTLPR polymorphisms.

The associations of human personality traits as measured by the Temperament and Character Inventory (TCI) with two genetic polymorphisms, the dopamine D4 receptor (DRD4) gene exon III repeat polymorphism (VNTR) and the serotonin transporter‐linked functional polymorphism (5‐HTTLPR) are presented in a population of 157 ethnically homogeneous Caucasians. No association was found between Novelty Seeking and the DRD4 VNTR, but male individuals with a 7‐repeat allele exhibited significantly lower Persistence scores. The 5‐HTTLPR polymorphism itself had no significant effect on any of the temperament dimensions, but a significant DRD4 VNTR × 5‐HTTLPR interaction was observed for Harm Avoidance, the subgroup with a s/s 5‐HTTLPR, 7‐repeat DRD4 genotype showed a higher mean Harm Avoidance score than the other groups. These results are discussed in relation to the recent findings on infant temperament. Association between the DRD4 7‐repeat allele and Persistence can be theoretically linked to the 7‐repeat allele as a risk factor for attention deficit hyperactivity disorder.

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.

PSYCHOPATHOLOGICAL ASPECTS OF DOPAMINERGIC GENE POLYMORPHISMS IN ADOLESCENCE AND YOUNG ADULTHOOD

Dopamine hypotheses of several psychiatric disorders are based upon the clinical benefits of drugs affecting dopamine transporter or receptors, and have prompted intensive candidate gene research within the dopaminergic system during the last two decades. The aim of this review is to survey the most important findings concerning dopaminergic gene polymorphisms in attention deficit hyperactivity disorder (ADHD), Tourette syndrome (TS), obsessive compulsive disorder, and substance abuse. Also, genetic findings of related phenotypes, such as inattention, impulsivity, aggressive behavior, and novelty seeking personality trait are presented, because recent studies have applied quantitative trait measures using questionnaires, symptom scales, or other objective endophenotypes. Unfortunately, genetic variants with minor effects are problematic to detect in these complex inheritance disorders, often leading to contradictory results. The most consistent association findings relate to ADHD and the dopamine transporter and the dopamine D4 receptor genes. Meta-analyses also support the association between substance abuse and the D2 receptor gene. The dopamine catabolizing enzyme genes, such as monoamine oxidase (MAO) A and catechol-O-methyltransferase (COMT) genes, have been linked to aggressive behaviors.

Carboxylesterase 1 gene polymorphism and methylphenidate response in ADHD

Methylphenidate (MPH) is the most frequently prescribed drug in the treatment of attention deficit hyperactivity disorder (ADHD). Several pharmacogenetic studies suggested that catecholamine candidate genes influence individual MPH-responses, but these results are mostly contradictory. Genetic analyses of MPH metabolizing carboxylesterase 1 enzyme (CES1) have not been carried out, whereas, meta-analysis of CYP2D6 genetic variants has been already indicated significant pharmacogenetic differences in atomoxetine treatment. Here we present an association analysis of the CES1 Gly143Glu functional polymorphism in a Hungarian ADHD group (n = 173). The genotype frequencies were similar to that of the general population (5.8% vs 4.1% of Gly/Glu heterozygote). Pharmacogenetic analysis was conducted among 122 ADHD children treated with MPH. Neither the categorical analysis comparing 90 responders vs 32 non-responders, nor the dimensional analysis of Inattention and Hyperactivity-Impulsivity score reduction showed a significant main genotype effect. However, analyzing the daily dose, we observed an association with the rare 143Glu-variant: 5 patients in the responder group carrying the Glu-allele required lower doses of MPH for symptom reduction (0.410 +/- 0.127 vs 0.572 +/- 0.153 mg/kg, t(1,88) = 2.33, p = 0.022). This result warrants for further investigations of the CES1 gene in larger ADHD samples.