No association between the −3081A/T polymorphism in the norepinephrine transporter gene promoter and personality traits in healthy subjects

Genetic risk scores associated with temperament clusters in Finnish depression patients

OBJECTIVE

Cloninger's temperament dimensions have been studied widely in relation to genetics. In this study, we examined Cloninger's temperament dimensions grouped with cluster analyses and their association with single nucleotide polymorphisms (SNPs). This study included 212 genotyped Finnish patients from the Ostrobothnia Depression Study.

METHODS

The temperament clusters were analysed at baseline and at six weeks from the beginning of the depression intervention study. We selected depression-related catecholamine and serotonin genes based on a literature search, and 59 SNPs from ten different genes were analysed. The associations of single SNPs with temperament clusters were studied. Using the selected genes, genetic risk score (GRS) analyses were conducted considering appropriate confounding factors.

RESULTS

No single SNP had a significant association with the temperament clusters. Associations between GRSs and temperament clusters were observed in multivariate models that were significant after permutation analyses. Two SNPs from the DRD3 gene, two SNPs from the SLC6A2 gene, one SNP from the SLC6A4 gene, and one SNP from the HTR2A gene associated with the HHA/LRD/LP (high harm avoidance, low reward dependence, low persistence) cluster at baseline. Two SNPs from the HTR2A gene were associated with the HHA/LRD/LP cluster at six weeks. Two SNPs from the HTR2A gene and two SNPs from the COMT gene were associated with the HP (high persistence) cluster at six weeks.

CONCLUSION

GRSs seem to associate with an individual's temperament profile, which can be observed in the clusters used. Further research needs to be conducted on these types of clusters and their clinical applicability.

Association of norepinephrine transporter gene polymorphisms in attention-deficit/hyperactivity disorder in Korean population

We investigated the association of three single nucleotide polymorphisms(SNP) of the norepinephrine transporter (NET) gene SLC6A2, T-182C (rs2242446), A-3081T (rs28386840), and G-1287A (rs5569) with the prevalence of attention-deficit/hyperactivity disorder (ADHD), its clinical severity, and other disease-related characteristics in a Korean population. The genotype, allele frequency and haplotype of 103 ADHD patients and 173 controls were analyzed for these three SNPs. All participants completed the Korean version of the ADHD Rating Scale (K-ARS). The ADHD group also completed the Korean Educational Development Institute-Wechsler Intelligence Scale for Children (KEDI-WISC) and the Continuous Performance Test (CPT) in a drug-naive state. The χ2 test and logistic regression analysis revealed no significant differences in the genotype distribution or allele frequencies of each SNP between the ADHD group and the control. In the haplotype analysis, the most common T-A-G haplotype was related to an increased risk of ADHD in females (P=0.002). There was no statistical significance between clinical features of ADHD and any specific allele of each SNP after multiple test correction except lower omission error in non-A girl carriers (GG type) of G-1287A (carrier 76.75±18.74, non-carrier 55.00±9.26, t=3.026, P=0.007, Bonferroni-corrected P=0.042). Some values related A-3081 and G-1287A showed a trend approaching the significance level when analyzed separately by gender. Even though it was not statistically meaningful after multiple test correction, G allele might have some protective effect against development of ADHD symptoms and this finding was consistent with previous studies.

Association Study between Norepinephrine Transporter Gene Polymorphism and Schizophrenia in a Korean Population

OBJECTIVE

We aimed to investigate possible associations between three norepinephrine transporter gene (SLC6A2) single nucleotide polymorphisms (T182C, A3081T, and G1287A) and schizophrenia. Also, we investigated the relationships of those polymorphisms with clinical severity and characteristics of schizophrenia.

METHODS

Participants were 220 schizophrenia patients in the acute phase and 167 healthy controls. The genotype, allele frequency, and haplotype of each group were analyzed for T182C, A3081T, and G1287A polymorphisms. Of the 220 schizophrenia patients, 163 patients were evaluated with the Positive and Negative Syndrome Scale (PANSS) and the Korean version of the Calgary depression scale for schizophrenia (K-CDSS) at baseline.

RESULTS

We found no significant differences between the schizophrenia patient group and the control group in genotype distribution or allele frequency of the three tested polymorphisms. Likewise, we could not find any significant differences in genotype or allele frequency by analyzing according to gender. In the haplotype study, no significant association emerged between specific haplotype combinations and schizophrenia. We also found no association between clinical scales (PANSS and K-CDSS) and the studied polymorphisms.

CONCLUSION

Our results suggest that the investigated polymorphisms of the NET gene are not associated with susceptibility to schizophrenia or its clinical features in a Korean population. However, this study remains significant because it is the first haplotype study to investigate associations between NET gene (SLC6A2) single nucleotide polymorphisms and schizophrenia in a Korean population. Future research with a larger sample size and more genetic markers is needed to replicate our results.

Analysis of Association between Norepinephrine Transporter Gene Polymorphisms and Personality Traits of NEO-FFI in a Japanese Population

OBJECTIVE

Norepinephrine is an important chemical messenger that is involved in mood and stress in humans, and is reabsorbed by the norepinephrine transporter (NET). According to Cloninger's theory, the noradrenergic system mediates the personality trait of reward dependence. Thus far, although association studies on NET gene polymorphisms and Cloninger's personality traits have been reported, they yielded inconsistent results. Therefore, in the present study we investigated whether or not the 1287G/A, -182T/C and -3081A/T polymorphisms of the NET gene (SLC6A2) are associated with reward dependence-related traits, as assessed by the five-factor model.

METHODS

After written informed consent was obtained from participants, the three NET gene polymorphisms were analyzed by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP), and personality was assessed by the Neuroticism Extraversion Openness-Five Factor Inventory (NEO-FFI) in 270 Japanese university students.

RESULTS

A significant relation was found between the -3081A/T functional promoter polymorphism and NEO-FFI scores: those with the T allele exhibited a lower extraversion (E) score than those without the T allele (Mann-Whitney U-test: z=-3.861, p<0.001). However, there was no correlation between the other NET gene polymorphisms and E score, and no association with other dimensions and these three polymorphisms.

CONCLUSION

We conclude that the -3081A/T functional polymorphism in the NET gene may affect the extraversion of reward dependence-related traits, as measured by NEO-FFI. However, we used only the shortened version of NEO-PI-R in this study. Further investigations are necessary using the full version of self-rating personality questionnaires.

Association between norepinephrine transporter gene (SLC6A2) polymorphisms and suicide in patients with major depressive disorder

BACKGROUND

Although several studies have investigated possible associations between norepinephrine neurotransmitter transporter gene (SLC6A2) polymorphisms and depression, few studies have examined associations between SLC6A2 polymorphisms and suicide.

METHODS

Three single-nucleotide polymorphisms (rs2242446, rs28386840, and rs5569) were measured in 550 patients: 201 with major depressive disorder (MDD) and suicide attempt/s, 160 with MDD without suicide attempts, and 189 healthy controls. Analysis of single-nucleotide polymorphisms (SNPs) and haplotype was conducted for the three groups. Subsequently, multivariate logistic regression analysis adjusting for age and gender was conducted to identify independent influences of each SNP. A possible association between suicide lethality and SLC6A2 polymorphisms was also investigated.

RESULTS

In the genotype and allele frequency analysis, there were significant differences in rs28386840 between suicidal MDD patients and healthy controls. In the haplotype analysis, TAA (rs2242446-rs28386840-rs5569, from left to right) was associated with suicide attempts in MDD, although the significance (p=0.043) disappeared after Bonferroni correction. There were no relationships between lethality scores and SLC6A2 polymorphisms in suicidal MDD.

LIMITATIONS

Modest sample size and a single type of neurotransmitter analyzed (norepinephrine) are the primary limitations.

CONCLUSION

Our results suggest that SLC6A2 polymorphisms were associated with suicide risk in patients with MDD. Future studies are warranted to elucidate possible mechanisms by which SLC6A2 polymorphisms influence suicide risk.