Zsolt Ronai

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.

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.

Serotonin transporter polymorphism and borderline or antisocial traits among low-income young adults

Objectives The short allele of the serotonin transporter linked polymorphic region, 5HTTLPR has been associated with anxiety, major depressive disorder and suicidality. The impulsive self- and other-damaging behaviors seen in borderline personality disorder and antisocial personality disorder also have substantial comorbidity with depression but are associated with more severe environmental stressors. This study tested the hypothesis of an association between the short allele of the 5HTTLPR and borderline or antisocial traits in young adulthood. Methods The 5HTTLPR was genotyped among 96 young adults from low to moderate income families (62 adults without and 34 adults with borderline personality disorder or antisocial personality disorder traits). Traits of borderline and antisocial personality disorders were assessed with the Structured Clinical Interview for Diagnosis-Axis II. Results The number of short 5HTTLPR alleles were significantly related to incidence of borderline personality disorder or antisocial personality disorder traits and also to each set of traits independently. Male sex and quality of care in infancy were also associated with incidence of borderline personality disorder and antisocial personality disorder traits but did not account for the association with the short allele. Depressive disorders were not associated with the short allele in this sample. Conclusions Young adults of lower socioeconomic status who carry the short 5HTTLPR allele may be especially vulnerable to developing antisocial or borderline traits by young adulthood.

Dopaminergic candidate genes in tourette syndrome : Association between tic severity and 3' UTR polymorphism of the dopamine transporter gene

Multiple evidence suggests an involvement of the dopamine neurotransmitter system in Tourette syndrome (TS). Therefore, dopaminergic candidate genes are in the center of genetic association analyses of TS. In this study, 103 TS patients and their parents have been characterized for different dopamine‐related polymorphisms including the 48 bp variable number of tandem repeats (VNTR) of the dopamine D4 receptor (DRD4) gene, the 40 bp VNTR of the dopamine transporter (DAT1, SLC6A3) gene and the Val158Met polymorphism of the catechol‐O‐methyltransferase (COMT) gene. In addition, the 120 bp duplication and three single nucleotide polymorphisms (SNPs) were assessed in the promoter region of the DRD4 gene. The −616G allele and the 2‐G‐A‐C haplotype (i.e., the 2‐repeat form of the 120 bp sequence ∼ −616G ∼ −615A ∼ −521C combination) were preferentially transmitted, however, these results did not remain significant after correction for multiple testing. Case‐control analyses have also been carried out, resulting in negative findings. On the other hand, using a dimensional approach, the DAT1 40 bp VNTR showed an association with the peak tic‐severity as measured by the Yale Global Tic Severity Scale. Patients with at least one copy of the 9‐repeat allele had significantly more severe symptoms than individuals with the homozygous 10/10 genotype (P = 0.002). In summary, allele frequencies did not differ between cases and controls, but DAT1 genotype accounted for variations of tic severity within the TS group.

Molecular and behavioral analysis of the intron 2 repeat polymorphism in the canine dopamine D4 receptor gene

Genetic polymorphisms in the human dopamine D4 receptor (DRD4) gene, especially the exon 3 variable number of tandem repeats (VNTR), have been related to several psychiatric disorders and personality traits. A homologous exon 3 VNTR has been described in dogs, and we previously showed an association between the DRD4 exon 3 polymorphism and activity/impulsivity trait in German shepherds. In this study, we present a detailed analysis of the intron 2 VNTR of the DRD4 gene. A short and a long form of the intronic variation were identified in 678 unrelated dogs from five breeds and in 22 wolves. For molecular analysis, the intron 2 region was cloned into a promoterless luciferase reporter vector that led to an elevation in transcriptional activity. Moreover, an allelic difference in promoter activity was detected, and a repressive effect of the long allele was observed. Behavioral analysis of 96 unrelated German shepherds showed a significant association between the social impulsivity endophenotype of the Greeting Test and both the exonic (P = 0.002) and the intronic (P = 0.003) VNTRs of the DRD4 gene. Moreover, an additive effect of the two polymorphisms was also shown (Spearman’s rho = 0.356, P = 0.0004). In conclusion, these results give further support to our previous findings that the DRD4 gene is associated with dog behavior. We also present molecular evidence for the functional role of the intron 2 VNTR in the canine DRD4 gene.

Polymorphism in the tyrosine hydroxylase (TH) gene is associated with activity-impulsivity in German Shepherd Dogs

We investigated the association between repeat polymorphism in intron 4 of the tyrosine hydroxylase (TH) gene and two personality traits, activity-impulsivity and inattention, in German Shepherd Dogs. The behaviour of 104 dogs was characterized by two instruments: (1) the previously validated Dog-Attention Deficit Hyperactivity Disorder Rating Scale (Dog-ADHD RS) filled in by the dog owners and (2) the newly developed Activity-impulsivity Behavioural Scale (AIBS) containing four subtests, scored by the experimenters. Internal consistency, inter-observer reliability, test-retest reliability and convergent validity were demonstrated for AIBS. Dogs possessing at least one short allele were proved to be more active-impulsive by both instruments, compared to dogs carrying two copies of the long allele (activity-impulsivity scale of Dog-ADHD RS: p = 0.007; AIBS: p = 0.023). The results have some potential to support human studies; however, further research should reveal the molecular function of the TH gene variants, and look for the effect in more breeds.

DRD4 and TH gene polymorphisms are associated with activity, impulsivity and inattention in Siberian Husky dogs

Both dopamine receptor D4 (DRD4) exon 3 and tyrosine hydroxylase (TH) intron 4 repeat polymorphisms have been linked to activity and impulsivity in German Shepherd dogs (GSDs). However, the results in GSDs may not be generalisable to other breeds, as allelic frequencies vary markedly among breeds. We selected the Siberian Husky for further study, because it is highly divergent from most dog breeds, including the GSD. The study sample consisted of 145 racing Siberian Huskies from Europe and North America. We found that this breed possesses seven DRD4 length variants, two to five more variants than found in other breeds. Among them was the longest known allele, previously described only in wolves. Short alleles of the DRD4 and TH repeat polymorphisms were associated with higher levels of activity, impulsivity and inattention. Siberian Huskies possessing at least one short allele of the DRD4 polymorphism displayed greater activity in a behavioural test battery than did those with two long alleles. However, the behavioural test was brief and may not have registered variation in behaviour across time and situations. Owners also completed the Dog-Attention Deficit Hyperactivity Disorder Rating Scale (Dog-ADHD RS), a more general measure of activity and attention. Siberian Huskies from Europe with two short alleles of the TH polymorphism received higher ratings of inattention on the Dog-ADHD RS than did those with the long allele. Investigation of the joint effect of DRD4 and TH showed that dogs possessing long alleles at both sites were scored as less active-impulsive than were others. Our results are aligned with previous studies showing that DRD4 and TH polymorphisms are associated with activity-impulsivity related traits in dogs. However, the prevalence of variants of these genes differs across breeds, and the functional role of specific variants is unclear.