Serotonin transporter promoter polymorphism, peripheral indexes of serotonin function, and personality measures in families with alcoholism

Emotional dysregulation, alexithymia and neuroticism: a systematic review on the genetic basis of a subset of psychological traits

Neuroticism, alexithymia and emotion dysregulation are key traits and known risk factors for several psychiatric conditions. In this systematic review, the aim is to evaluate the genetic contribution to these psychological phenotypes. A systematic review of articles found in PubMed was conducted. Search terms included 'genetic', 'GWAS', 'neuroticism', 'alexithymia' and 'emotion dysregulation'. Risk of bias was assessed utilizing the STREGA checklist. Two hundred two papers were selected from existing literature based on the inclusion and exclusion criteria. Among these, 27 were genome-wide studies and 175 were genetic association studies. Single gene association studies focused on selected groups of genes, mostly involved in neurotransmission, with conflicting results. GWAS studies on neuroticism, on the other hand, found several relevant and replicated intergenic and intronic loci affecting the expression and regulation of crucial and well-known genes (such as DRD2 and CRHR1). Mutations in genes coding for trascriptional factors were also found to be associated with neuroticism (DCC, XKR6, TCF4, RBFOX1), as well as a noncoding regulatory RNA (LINC00461). On the other hand, little GWAS data are available on alexythima and emotional dysregulation.

Genetic association of nucleus accumbens 5-hydroxyindoleacetic acid level and alcohol preference drinking in a quasi-congenic male mice: Potential modulation by Grm7 gene polymorphism

OBJECTIVE

To test the hypothesis that predisposition to high alcohol drinking behavior is genetically associated with hypoactive serotonergic function in the Nucleus Accumbens (NAc).

METHOD

Alcohol avoiding C5A3 and alcohol preferring I5B25A mice of the Quasi-congenic Recombinant QTL Introgression (RQI) mouse strains were subjected to in vivo microdialysis in the NAc. Neurotransmitter and metabolite contents were analyzed by HPLC and samples were collected in three phases: Baseline, Control, and Alcohol. Samples were collected with 20 min intervals.

RESULTS

Between-strain differences restricted to small chromosome segments significantly affected both alcohol preference drinking and NAc 5-HIAA levels [F_{1, 13} = 5.569 p=.035 (General Linear Model Repeated Measures ANOVA and Tests of Between-Subjects Effects)]. Whole genome biallelic DNA marker genotyping allowed the identification of 16 differential microsatellite markers associated with low 5-HIAA levels and excessive alcohol drinking. Chromosome 6 markers were linked to Grm7 (51.19 centimorgan), a reported candidate gene for modulation of addiction. The results are consistent with earlier reports of association of low 5-HIAA and high alcohol consumption in rats and primates, including Homo sapiens.

CONCLUSION

Low NAc 5-HIAA and high alcohol consumption are genetically associated in a quasi-congenic mouse model carrying variants of the Grm7 gene. We propose that constitutional polymorphism in Grm7 may modulate CRF neuron activity via altered mGluR7 expression thus targeting CRF pathways to substance use circuits. This raises the possibility of modulation of DRN 5-HT neurons leading to hypo- or hyper-serotonergic condition in NAc and higher or lower alcohol preference drinking.

Association of Serotonin Transporter Gene (5-HTTLPR/rs25531) Polymorphism with Comorbidities of Panic Disorder

INTRODUCTION

Panic disorder (PD) has many comorbidities such as depression, bipolar disorder (BPD), and agoraphobia (AG). PD is a moderately heritable anxiety disorder whose pathogenesis is not well understood. Recently, a tri-allelic serotonin transporter (5-HTTLPR/rs25531) polymorphism was reported to be more sensitive to personality traits compared to the bi-allelic 5-HTTLPR polymorphism. We hypothesized that the 5-HTTLPR/rs25531 polymorphism may lead to a pathological anxious state depending on the presence or absence of a comorbidity in PD.

METHODS

In this study, we investigated the relationship between comorbidities in PD and tri-allelic 5-HTTLPR polymorphisms. A total of 515 patients with PD (148 males, 367 females) were genotyped, and the Revised NEO Personality Inventory as well as anxiety-related psychological tests were administered. Depression, BPD, and AG were diagnosed as comorbidities.

RESULTS

For the tri-allele 5-HTTLPR genotype, a significant interaction effect was found between openness to experience and comorbid depression. Examination of the interaction between AG and the tri-allelic 5-HTTLPR genotype revealed that L' allele carriers are associated with higher trait anxiety than the S'S' genotype group in PD without AG.

CONCLUSION

Some anxiety and personality traits can be characterized by the tri-allelic gene effect of 5-HTTLPR. These results suggest that tri-allelic 5-HTTLPR genotypes have genetic effects on the presence of comorbidities of PD.

Alcohol use disorders among adult children of alcoholics (ACOAs): Gene-environment resilience factors

Both genetic and early environmental factors contribute to the pathogenesis of Alcohol Use Disorder (AUD). Gender and psychopathology symptoms might further moderate this association, resulting in an impairment of both the dopaminergic and serotoninergic pathways that sustain the binge, withdrawal and craving cycle. In a sample of of adult children of alcoholic parents (ACOAs) (n = 107) we compared those with and without an AUD, on socio-demographic variables, adverse childhood experiences, psychopathology symptoms and two polymorphisms associated with an impaired serotoninergic and dopaminergic neurotransmission (5HTTLPR and Taq1A/DRD2). A logistic regression revealed that an early caring environment might lower the risk of developing an AUD. When controlling for the actual psychopathology symptoms, being male and having the genotype associated with an impaired dopaminergic neurotransmission were still associated with AUD. Results were confirmed by an unsupervised approach that showed how the clusters characterised by being male and having the high risk genotypes were still associated with AUD compared to being female without the unfavourable dopamine genotype.Our results point to the need for implementing prevention strategies aimed at creating a caring environment especially in those families with an alcoholic parent. We further suggest that psycho-education as a symptom recognition and avoiding self-medication could improve the outcome in those subjects at higher risk, especially males.

Association of serotonin system-related genes with homicidal behavior and criminal aggression in a prison population of Pakistani Origin

The serotonin transporter (SLC6A4), 5-HT_2A (HTR2A) and 5-HT_2B (HTR2B) recepter genes, express proteins that are important regulators of serotonin reuptake and signaling, and thereby may contribute to the pathogenesis of aggressive criminal behavior. 370 sentenced murderers in Pakistani prisons and 359 men without any history of violence or criminal delinquency were genotyped for six candidate polymorphisms in SLC6A4, HTR2A and HTR2B genes. An association of higher expressing L/L and L_A/L_A variants of the 5-HTTLPR polymorphism was observed with homicidal behavior (bi-allelic: OR = 1.29, p = 0.016, tri-allelic: OR = 1.32, p = 0.015) and in the murderer group only with response to verbal abuse (OR = 2.11, p = 0.015), but not with other measures of self-reported aggression. L/L and L_A/L_A genotypes of the 5-HTTLPR polymorphism were associated with higher aggression scores on STAX1 scale of aggression compared to lower expressing genotypes (S/S, S/L_G, L_G/L_G) in prison inmates. No associations were apparent for other serotonergic gene polymorphisms analyzed. Using the Braineac and GTEx databases, we demonstrated significant eQTL based functional effects for rs25531 in HTTLPR and other serotonergic polymorphisms analyzed in different brain regions and peripheral tissues. In conclusion, these findings implicate SLC6A4* HTTLPR as a major genetic determinant associated with criminal aggression. Future studies are needed to replicate this finding and establish the biologic intermediate phenotypes mediating this relationship.

The NEO-FFI domain of openness to experience moderates ketamine response in treatment resistant depression

BACKGROUND

There are many putative mechanisms by which ketamine has its effect and many unanswered questions about risks and benefits of long-term ketamine therapy. A research imperative is the identification of predictors of response to intravenous ketamine, especially a sustained response to maintenance ketamine. Temperament is an inherited aspect of personality and is a predictive factor for outcome in treatment resistant depressed (TRD) patients.

METHODS

We analyzed which domains of personality impacted initial and sustained ketamine response. Utilizing the Neuroticism Extraversion Openness Five Factor Inventory (NEO-FFI) on 125 participants with TRD, we tested (1) whether the degree of neuroticism predicted initial and/or sustained response to ketamine; and (2) whether extraversion, agreeableness, openness to experience, and conscientiousness had an impact on response.

RESULTS

Our findings confirmed previous literature that elevated neuroticism, low conscientiousness, and low extraversion was the pattern of our TRD population regardless of response. Openness was the only factor to significantly predict sustained treatment outcome.

LIMITATIONS

Our findings are limited by the lack of placebo control, small sample size, non- standardized infusion intervals, polypharmacy rather than ketamine monotherapy, a select TRD population in that they had all failed ECT, and a primarily Caucasian population.

CONCLUSIONS

Our registry adds to the literature that factors making up temperament may have predictive value in regard to treatment response, specifically the outcome for TRD patients receiving long-term ketamine infusion therapy. If confirmed, assessing for Openness could reduce inappropriate exposure to ketamine with its attendant unknown long-term risks.

Functional polymorphism of the serotonin reuptake transporter SLC6A4 gene in various clinical variants of irritable bowel syndrome

Rationale:Irritable bowel syndrome (IBS) is a multifactorial disease, the genetic aspect of which is being actively studied.

Aim:To investigate functional polymorphism of the serotonin reuptake transporter (SERT)SLC6A4gene of various clinical variants of IBS.

Materials and methods:We performed a cross-sectional single center study in 79 Caucasian patients with IBS (according to the Rome criteria IV). The patients were divided into two groups: group 1, IBS with diarrhea (IBS-D, n = 45) and group 2, IBS with constipation (IBS-C, n = 34). The control group included 59 Caucasian patients with gastrointestinal disorders without IBS. Polymorphism5-HTTLPRof theSLC6A4gene was assessed in all subjects. In group 1 patients, blood serotonin levels were measured and psychological tests were performed, including Spielberger's State / Trait Anxiety Inventory, quality of life by SF36 and GSRS, Asthenia scale, VAS scores for pain intensity.

Results:Thirty-five of 45 (77.8%) patients with IBS-D carried the mutantSallele, which was significantly more frequent than in the IBS-C group (p = 0.002) and in the control group (p = 0.005). There were no statistically significant differences (p = 0.54) in the frequency of detection of the homozygousLLgenotype (normal allele) and the heteroand homozygous mutant alleles (SLandSS) genotype between the IBS-C and control patients. In the IBS-D group, a gender difference for the mutantSSallele of5-HTTLPRwas found, with significantly higher frequency in female patients (p = 0.0147). No significant gender differences in the genotype distribution between the patients with IBS-C and the control group were found. There were also no differences in blood serotonin levels in the IBS patients with various5-HTTLPRtypes (p = 0.086); they were all in the reference range. However, there was a trend towards lower serotonin levels in theLLgenotype carriers compared to those with theSS/SLpolymorphisms. The Gastroenterological inventoryGSRSdemonstrated significantly higher total score for the constipation syndrome in the patients with homozygousLL 5-HTTLPRpolymorphism, compared to that in the patients with theSS/SLgenotype (p = 0.013).

Conclusion:The results may be related to lower expression of theSLC6A4gene in the carriers of the mutant allele in the5-HTTLPRpromoter and subsequent decreased rate of serotonin uptake, with resulting stimulation of the gastrointestinal tract. TheSERTpolymorphism of theSLC6A4gene is worth further investigation as a potential candidate gene in the IBS pathophysiology.

Serotonin transporter gene linked polymorphism (5-HTTLPR) determines progredience of alcohol dependence in Belarusian young males

PURPOSE

Allelic duality and functional impact of degenerate repeat at 5'- flanking promoter region in SLC6A4 gene of the serotonin transporter (5-HTTLPR), have been in the focus of investigations over the years. Various outcomes regarding an association of its polymorphism with risks of alcohol dependence syndrome (ADS) were presented. Such studies have not been conducted in the Eastern European population e.g. Belarus. We therefore checked: the association of 5-HTTLPR polymorphism with ADS, and functional impact of the polymorphism on progredience of ADS in Belarusian population.

MATERIAL AND METHODS

The study involved 499 Belarusian males: 377 subjects with ADS (AG), and a control group (CG) with 122 subjects without alcohol-related problems. The ADS group was further divided into two groups of individuals with rapid (AG (R)) and delayed (AG (D)) progression of ADS. Clinical diagnosis was carried-out using ICD-10 criteria, Belarusian Addiction Severity Index, "B-ASI" and Alcohol-Use-Disorders-Identification-Test (AUDIT). PCR-RFLP analysis was performed.

RESULTS

There were no significant differences in the distribution of frequencies of either the 5-HTTLPR genotype or the short and long allele among AG and CG. However, the ADS 5-HTTLPR genotype and allele distribution frequencies differ significantly by the variation in progression of ADS.

CONCLUSIONS

There is no significant association between polymorphism of serotonin transporter gene and risk of ADS. However, the polymorphism significantly determines progredience of ASD in subjects with pathological patterns of alcohol consumption. Findings from this study carry preliminary significance as a facility to effective alcohol addiction treatment, rehabilitation and preventive services in the Eastern Europe.

Failure to Replicate the Association Between Fractional Anisotropy and the Serotonin Transporter Gene (5-HTTLPR, rs25531)

Recent work underlines the importance of alterations in white matter (e.g., measured by fractional anisotropy (FA)) as a neural vulnerability marker for psychiatric disorders. In this context, the uncinate fasciculus (UF), which connects the limbic system with prefrontal areas, has repeatedly been linked to psychiatric disorders, fear processing, and anxiety-related traits. Individual differences in FA may partly be genetically determined. Variation in the promoter region of the serotonin transporter gene (serotonin transporter-linked polymorphic region [5-HTTLPR]) is a particularly promising candidate in this context, which has been linked to psychiatric disorders as well as to limbic and prefrontal reactivity. However, findings on the association between the 5-HTTLPR and FA within the UF-tract have been heterogeneous. The present study investigated this relationship and extended previous work by considering different genetic classification approaches as well as sex effects in a human sample (n = 114). All participants were genotyped for the 5-HTTLPR and the rs25531 polymorphism. As a main result, we did not find any significant relationship between the 5-HTTLPR and FA in the UF-tract although power analyses showed an adequate power. In addition, genotype effects were neither found when different classification approaches were used nor when analyses were carried out in males or females only. The present findings suggest that the association of the 5-HTTLPR and FA seems to be a more labile phenomenon than previously assumed. Possible explanations and limitations are discussed.

Personality as an intermediate phenotype for genetic dissection of alcohol use disorder

Genetic and environmental interactive influences on predisposition to develop alcohol use disorder (AUD) account for the high heterogeneity among AUD patients and make research on the risk and resiliency factors complicated. Several attempts have been made to identify the genetic basis of AUD; however, only few genetic polymorphisms have consistently been associated with AUD. Intermediate phenotypes are expected to be in-between proxies of basic neuronal biological processes and nosological symptoms of AUD. Personality is likely to be a top candidate intermediate phenotype for the dissection of the genetic underpinnings of different subtypes of AUD. To date, 38 studies have investigated personality traits, commonly assessed by the Cloninger's Tridimensional Personality Questionnaire (TPQ) or Temperament and Character Inventory (TCI), in relation to polymorphisms of candidate genes of neurotransmitter systems in alcohol-dependent patients. Particular attention has been given to the functional polymorphism of the serotonin transporter gene (5-HTTLPR), however, leading to contradictory results, whereas results with polymorphisms in other candidate monoaminergic genes (e.g., tryptophan hydroxylase, serotonin receptors, monoamine oxidases, dopamine receptors and transporter) are sparse. Only one genome-wide association study has been performed so far and identified the ABLIM1 gene of relevance for novelty seeking, harm avoidance and reward dependence in alcohol-dependent patients. Studies investigating genetic factors together with personality could help to define more homogenous subgroups of AUD patients and facilitate treatment strategies. This review also urges the scientific community to combine genetic data with psychobiological and environmental data to further dissect the link between personality and AUD.

The Serotonin Transporter and Early Life Stress: Translational Perspectives

The interaction between the serotonin transporter (SERT) linked polymorphic region (5-HTTLPR) and adverse early life stressing (ELS) events is associated with enhanced stress susceptibility and risk to develop mental disorders like major depression, anxiety, and aggressiveness. In particular, human short allele carriers are at increased risk. This 5-HTTLPR polymorphism is absent in the rodent SERT gene, but heterozygous SERT knockout rodents (SERT^+/−) show several similarities to the human S-allele carrier, therefore creating an animal model of the human situation. Many rodent studies investigated ELS interactions in SERT knockout rodents combined with ELS. However, underlying neuromolecular mechanisms of the (mal)adaptive responses to adversity displayed by SERT rodents remain to be elucidated. Here, we provide a comprehensive review including studies describing mechanisms underlying SERT variation × ELS interactions in rodents. Alterations at the level of translation and transcription but also epigenetic alterations considerably contribute to underlying mechanisms of SERT variation × ELS interactions. In particular, SERT^+/− rodents exposed to adverse early rearing environment may be of high translational and predictive value to the more stress sensitive human short-allele carrier, considering the similarity in neurochemical alterations. Therefore, SERT^+/− rodents are highly relevant in research that aims to unravel the complex psychopathology of mental disorders. So far, most studies fail to show solid evidence for increased vulnerability to develop affective-like behavior after ELS in SERT^+/− rodents. Several reasons may underlie these failures, e.g., (1) stressors used might not be optimal or severe enough to induce maladaptations, (2) effects in females are not sufficiently studied, and (3) few studies include both behavioral manifestations and molecular correlates of ELS-induced effects in SERT^+/− rodents. Of course, one should not exclude the (although unlikely) possibility of SERT^+/− rodents not being sensitive to ELS. In conclusion, future studies addressing ELS-induced effects in the SERT^+/− rodents should extensively study both long-term behavioral and (epi)genetic aspects in both sexes. Finally, further research is warranted using more severe stressors in animal models. From there on, we should be able to draw solid conclusions whether the SERT^+/− exposed to ELS is a suitable translational animal model for studying 5-HTTLPR polymorphism and stress interactions.

Personality traits as an endophenotype in genetic studies on suicidality in bipolar disorder

Introduction The influence of personality traits on suicidal behaviour risk has been well documented. Personality traits and suicidal behaviour are partially genetically determined and personality has been described as an endophenotype of suicidal behaviour. The aim of this study was to investigate a possible association between personality traits with suicidal behaviour and selected serotonergic gene polymorphisms.

METHODS

In the study we included 156 patients meeting DSM-IV criteria for bipolar disorder (BP) and 93 healthy controls. The personality dimensions were assessed using the Temperament and Character Inventory (TCI). We genotyped two selected polymorphisms of the tryptophan hydroxylase 1 (TPH1) gene (rs1800532 218A>C and rs1799913 779A>C) and polymorphism in the promoter region of serotonin transporter gene (5-HTTLPR, rs25531) related to serotoninergic neurotransmission. Multiple poisson regression, logistic regression and Kruskal-Wallis tests were applied.

RESULTS

We found numerous differences between the BP patients and the control group in terms of their TCI dimensions/subdimensions. Significant differences were found between patients with, and without, suicidal attempts in fatigability and asthenia (Ha4), as well as in harm avoidance (Ha). We also found that the interactions between TCI subdimensions (the interaction of disordiness (Ns4) and spiritual acceptance (St3), disordiness (Ns4) and integrated conscience (C5), extravagance (Ns3) and resourcefulness (Sd3)) were significantly contributing for suicidal behaviour risk. We found association between all studied genetic polymorphisms and several TCI dimensions and subdimensions.

CONCLUSION

Our results confirm that personality traits are partially determined by genes. Both personality traits and the interactions between temperament and character traits, may be helpful in predicting suicidal behaviour.

Effects of the serotonin transporter gene, sensitivity of response to alcohol, and parental monitoring on risk for problem alcohol use

The serotonin transporter-linked polymorphic region (5-HTTLPR) of the serotonin transporter gene (SLC6A4) has been previously associated with alcohol-related risk. Most findings point to short (S) allele carriers being at increased risk for negative alcohol outcomes relative to long allele homozygotes, although some work indicates a more complex relationship. The current prospective study aimed to clarify how and under what circumstances variations in 5-HTTLPR transmit risk for various alcohol-related outcomes. Participants were 218 adolescents and young adults (29% female) enrolled in the Michigan Longitudinal Study. We tested a moderated mediation model with 5-HTTLPR as the predictor, Self-Rating of the Effects of Alcohol (SRE) score as the mediator, alcohol-related outcomes as the dependent variables, parental monitoring as the moderator of the SRE to alcohol outcomes path, and prior drinks, sex, age, and body mass index as covariates. Four alcohol-related outcomes were tested. The S allele was associated with higher SRE scores (i.e., lower response to alcohol). Parental monitoring was a significant moderator: At low levels of parental monitoring, higher SRE scores predicted more drinks consumed and binge drinking episodes. At high levels of monitoring, higher SRE scores were significantly related to fewer alcohol-related problems. Findings suggest that one mechanism by which 5-HTTLPR variation transmits alcohol-related risk is through level of response to alcohol. Furthermore, the strength and direction of this effect varied by level of parental monitoring, indicating that even in the presence of genetic and physiological vulnerability, parents can influence the likelihood of offspring developing problematic alcohol-related behaviors.

Suicide behavior as a quantitative trait and its genetic background

INTRODUCTION

Studies have not given yet a clear answer what is the genetic background of suicidal predisposition. The associations between polymorphisms of the TPH1 and 5-HTTLPR genes and violent suicidal behavior was revealed with the least inconsistencies.

METHOD

We selected 10 "strong candidate genes" and 35 SNPs, SLC6A4 and ACP1 for replication study. We searched associations between precisely described suicidal phenotype in 825 affective patients and polymorphisms of selected neurobiological pathways genes as well as their interactions that constitute suicidal risk.

RESULTS

The results confirm the role of TPH1, TPH2, 5HT2A, CRHR1 and ACP1 variants in the risk of suicidal behavior.

LIMITATIONS

In our study we analyzed limited number of candidate genes and only one of them is linked to lithium mechanism of action. We had no data on pharmacological treatment of investigated patients and its relation to the time of suicide attempt.

CONCLUSION

Our results indicate that polymorphisms of various signaling pathways are involved in the pathogenesis of suicidal behavior. Non-genetic factors are also involved in the risk of suicidal attempts.

Alcohol Dependence and Genetic Variability in the Serotonin Pathway among Currently and Formerly Alcohol-Dependent Males

BACKGROUND

Genes involved in the serotonin pathway may determine the susceptibility to alcohol dependence and its severity. The present study explored whether specific polymorphisms in the serotonin pathway could be associated with alcohol dependence or alcohol-related psychopathological symptoms.

METHODS

The cohort comprised 101 currently and 100 formerly alcohol-dependent males, as well as 97 male healthy blood donors. The following questionnaires were employed: the Alcohol Use Disorders Identification Test, the Zung Depression and Anxiety Scale, the Brief Social Phobia Scale, the Yale-Brown Obsessive Compulsive Scale and Obsessive Compulsive Drinking Scale, and the Buss-Durkee Hostility Inventory. Subjects were genotyped for bi- and triallelic SLC6A4 5-HTTLPR,HTR1A rs6295, and HTR1B rs13212041.

RESULTS

Statistical differences in bi- and triallelic SLC6A4 5-HTTLPR genotype distribution were observed between the 3 groups investigated (p = 0.008 and p = 0.023, respectively); however, no gene-dose effect was observed. The severity of the alcohol problems was higher in currently alcohol-dependent subjects with the 5-HTTLPR LL (p = 0.039) and L′L′ genotypes (p = 0.027). Formerly dependent subjects with the 5-HTTLPR S′S′ genotype showed more social anxiety, depressive, and anxiety traits (p = 0.009, p = 0.006, and p = 0.036, respectively). Healthy controls with the 5-HTTLPR SS genotype showed more traits of social anxiety (p = 0.020).

CONCLUSIONS

Our findings suggest that bi- and triallelic SLC6A4 5-HTTLPR has some effects on the severity of alcohol dependence. Triallelic 5-HTTLPR was associated with social anxiety, anxiety, and depressive traits in alcohol-dependent subjects.

5-HTTLPR and gender differences in affective disorders: A systematic review

BACKGROUND

Serotonin transporter-linked polymorphic region (5-HTTLPR) variants have been extensively studied in psychiatric disorders. Although gender effects have been reported, they have not been comprehensively reviewed. The aim of our study was to summarize literature findings on 5-HTTLPR and gender differences in affective disorders.

METHODS

A systematic search of PubMed, ISI Web of Knowledge, and PsycINFO databases was performed for dates until January 2015. The included articles (n=78) analyzed the association between 5-HTTLPR and affective spectrum disorders, taking into account gender. The quality of each study was assessed through STROBE and CONSORT.

RESULTS

5-HTTLPR modulation of affective disorders varied by gender. The S allele (or SS genotype) seemed to be differently associated with an increased risk of depression, depressive symptoms, anxiety traits and symptoms, and symptoms of internalizing behavior among women and an increased risk of aggressiveness, conduct disorder and symptom counts of externalizing behavior among men. Moreover, the presence of stressful life events reinforced the association. Interestingly, these differences seemed to begin with adolescence and were not consistent among the elderly, suggesting a plausible role of hormonal fluctuations.

LIMITATIONS

The review is limited by the small number of included papers, due to the paucity of information in the literature regarding 5-HTTLPR and gender.

CONCLUSIONS

5-HTTLPR variants may exert a differential modulation on a number of features depending on gender. Further studies are needed to more deeply investigate the effect of 5-HTTLPR×gender on the modulation of affective disorders.

A review of 5-HT transporter linked promoter region (5-HTTLPR) polymorphism and associations with alcohol use problems and sexual risk behaviors

Alcohol use and sexual risk behaviors are multidimensional phenomena involving many genetic and environmental factors. 5-HT transporter linked promoter region (5-HTTLPR) polymorphism constitutes an important factor affecting alcohol use problems and risky sexual behaviors. This paper narratively reviews studies on 5-HTTLPR polymorphism and its associations with alcohol use problems and sexual risk behaviors. We searched the electronic databases, PubMed, Ovid, and Google Scholar for articles using MeSH terms. Relevant articles were reviewed and eligible articles were selected for the study. Many studies have reported a significant but moderate association between 5-HTTLPR polymorphism and alcohol use problems. These studies have implicated the presence of at least one S allele to be associated with significant increases in alcohol use problems. Similarly, some studies associate the S allele with increased sexual risk behaviors. Effective alcohol cessation initiatives and STI/HIV prevention programs should be modified to account for 5-HTTLPR polymorphism before planning interventions; genetic effects could moderate the intervention effect.

A meta-analysis of the associations between the SLC6A4 promoter polymorphism (5HTTLPR) and the risk for alcohol dependence

Serotonin reuptake variation is linked to a functional polymorphism in the promoter region of the SLC6A4 gene on chromosome 17. It is plausible that variations in genetically determined SLC6A4 activity may modify the risk for alcohol dependence. To determine whether this allele is associated with alcohol dependence, the authors conducted a systematic review and meta-analysis. Twenty-five studies including 8885 participants were reviewed and analyzed. The meta-analysis was carried out using a random-effects model. Overall, the results did not support an association between alcohol dependence and the SLC6A4 promoter polymorphism for the dominant, recessive, and additive genetic risk models, respectively [odds ratio (OR)=0.99 (95% confidence interval (CI): 0.83, 1.18), OR=0.86 (95% CI: 0.71, 1.03), and OR=0.88 (95% CI: 0.69, 1.13)]. When effect modification was tested for sex, race/ethnicity, presence/absence of a psychiatric disorder, year of publication, and diagnostic criteria, none of the factors were found to be significantly associated with alcohol dependence. The findings in this meta-analysis suggest that the SLC6A4 promoter polymorphism is not associated with alcohol dependence.

The association between the 5-HTTLPR and neural correlates of fear conditioning and connectivity

Strong evidence links the 5-HTTLPR genotype to the modulation of amygdala reactivity during fear conditioning, which is considered to convey the increased vulnerability for anxiety disorders in s-allele carriers. In addition to amygdala reactivity, the 5-HTTLPR has been shown to be related to alterations in structural and effective connectivity. The aim of this study was to investigate the effects of 5-HTTLPR genotype on amygdala reactivity and effective connectivity during fear conditioning, as well as structural connectivity [as measured by diffusion tensor imaging (DTI)]. To integrate different classification strategies, we used the bi-allelic (s-allele vs l/l-allele group) as well as the tri-allelic (low-functioning vs high-functioning) classification approach. S-allele carriers showed exaggerated amygdala reactivity and elevated amygdala-insula coupling during fear conditioning (CS + > CS-) compared with the l/l-allele group. In addition, DTI analysis showed increased fractional anisotropy values in s-allele carriers within the uncinate fasciculus. Using the tri-allelic classification approach, increased amygdala reactivity and amygdala insula coupling were observed in the low-functioning compared with the high-functioning group. No significant differences between the two groups were found in structural connectivity. The present results add to the current debate on the influence of the 5-HTTLPR on brain functioning. These differences between s-allele and l/l-allele carriers may contribute to altered vulnerability for psychiatric disorders.

Serotonin transporter gene polymorphisms: Relation with platelet serotonin level in patients with primary Sjogren's syndrome

Significantly lower platelet serotonin level (PSL) in patients with primary Sjogren's syndrome (pSS) than in healthy controls has been reported in our prior studies. In the present report, we demonstrated effect of functional polymorphisms in the serotonin transporter gene (5-HTT) on PSL. We describe a group of 61 pSS patients and 100 healthy individuals subjects, who received PSL measurement in our prior study. All subjects were genotyped for the promoter 5-HTTLPR (L/S), rs25531 (A/G) and intronic 5-HTTVNTRin2 (l/s) polymorphisms. Overall, the presence of 5-HTTVNTRin2 ss genotype was associated with significantly lower PSL in pSS patients, not in healthy controls. Reduced PSL in pSS patients is in line with hypothesis of association between chronic immunoinflammation and 5-HT system dysregulation, identifying additional mechanisms such as altered 5-HT transport as potential genetic factor contributing to PSL depletion.

Gender-specific association between the COMT Val158Met polymorphism and openness to experience in panic disorder patients

BACKGROUND

Because major depression and panic disorder are both more prevalent among females and since several lines of evidence suggest that genetic factors might influence an individual's vulnerability to panic disorder, gene-gender interactions are being examined in such psychiatric disorders and mental traits. A number of studies have suggested that specific genes, e.g. catechol-O-methyltransferase (COMT), might lead to distinct clinical characteristics of panic disorder.

METHOD

We compared gender-specific personality-related psychological factors of 470 individuals with panic disorder and 458 healthy controls in terms of their COMT Val158Met polymorphism and their scores on the Revised NEO Personality Inventory (NEO PI-R) and State-Trait Anxiety Inventory (STAI) with a 1-way analysis of covariance.

RESULTS

In the male panic disorder patients, the NEO PI-R score for openness to experience was significantly lower in the Met/Met carrier group, whereas there was no such association among the female panic disorder patients or the male or female control groups.

CONCLUSION

The gender-specific effect of the COMT genotype suggests that the COMT Val/Met genotype may influence a personality trait, openness to experience, in males with panic disorder.

Monoamine-sensitive developmental periods impacting adult emotional and cognitive behaviors

Development passes through sensitive periods, during which plasticity allows for genetic and environmental factors to exert indelible influence on the maturation of the organism. In the context of central nervous system development, such sensitive periods shape the formation of neurocircuits that mediate, regulate, and control behavior. This general mechanism allows for development to be guided by both the genetic blueprint as well as the environmental context. While allowing for adaptation, such sensitive periods are also vulnerability windows during which external and internal factors can confer risk to disorders by derailing otherwise resilient developmental programs. Here we review developmental periods that are sensitive to monoamine signaling and impact adult behaviors of relevance to psychiatry. Specifically, we review (1) a serotonin-sensitive period that impacts sensory system development, (2) a serotonin-sensitive period that impacts cognition, anxiety- and depression-related behaviors, and (3) a dopamine- and serotonin-sensitive period affecting aggression, impulsivity and behavioral response to psychostimulants. We discuss preclinical data to provide mechanistic insight, as well as epidemiological and clinical data to point out translational relevance. The field of translational developmental neuroscience has progressed exponentially providing solid conceptual advances and unprecedented mechanistic insight. With such knowledge at hand and important methodological innovation ongoing, the field is poised for breakthroughs elucidating the developmental origins of neuropsychiatric disorders, and thus understanding pathophysiology. Such knowledge of sensitive periods that determine the developmental trajectory of complex behaviors is a necessary step towards improving prevention and treatment approaches for neuropsychiatric disorders.

Effects of genetic and early environmental risk factors for depression on serotonin transporter expression and methylation profiles

The serotonin transporter (SERT) gene-linked polymorphic region (5-HTTLPR) has been implicated in moderating the link between life stress and depression. However, respective molecular pathways of gene-environment (GxE) interaction are largely unknown. Sustained alterations in SERT gene expression profiles, possibly mediated by epigenetic modifications, are a frequent correlate of depression and may thus constitute a putative mediator of GxE interaction. Here, we aimed to investigate joint effects of 5-HTTLPR and self-reported environmental adversity throughout the lifespan (prenatal, early and recent stress/trauma) on in vivo SERT mRNA expression in peripheral blood cells. To further evaluate whether environmentally induced changes in SERT expression are mediated by epigenetic modifications, we analyzed 83 CpG sites within a 799-bp promoter-associated CpG island of the SERT gene using the highly sensitive method of bisulfite pyrosequencing. Participants were 133 healthy young adults. Our findings show that both the 5-HTTLPR S allele and maternal prenatal stress/child maltreatment are associated with reduced in vivo SERT mRNA expression in an additive manner. Remarkably, individuals carrying both the genetic and the environmental risk factors exhibited 32.8% (prenatal stress) and 56.3% (child maltreatment) lower SERT mRNA levels compared with those without any risk factor. Our data further indicated that changes in SERT mRNA levels were unlikely to be mediated by DNA methylation profiles within the SERT CpG island. It is thus conceivable that the persistent changes in SERT expression may in turn relate to altered serotonergic functioning and possibly convey differential disease vulnerability associated with 5-HTTLPR and early adversity.

Analysis of circulating cholesterol levels as a mediator of an association between ABO blood group and coronary heart disease

BACKGROUND

Non-O type of ABO blood group has been associated with a predisposition to coronary heart disease. It is thought that this association is partly mediated by increased cholesterol levels in non-O-type individuals. In this study, we sought to estimate the mediation effect size.

METHODS AND RESULTS

In a group of individuals (n=6476) undergoing coronary angiography, we detected associations of non-O type with significant coronary artery disease with >50% stenosis in ≥1 coronary arteries (odds ratio, 1.24; 95% confidence interval, 1.10-1.39; P=2.6×10(-4)) and with prevalent or incident myocardial infarction (odds ratio, 1.22; 95% confidence interval, 1.09-1.37; P=1.2×10(-3)). Subjects of non-O type had higher levels of total cholesterol, low-density lipoprotein cholesterol, and non-high-density lipoprotein cholesterol (mean [SEM] in mmol/L: 4.931[0.021], 3.041 [0.018], and 3.805 [0.020] in non-O type compared with 4.778 [0.026], 2.906 [0.021], and 3.669 [0.024] in O type; P=3.8×10(-7), P=1.5×10(-7), and P=3.1×10(-7), respectively). Mediation analyses indicated that 10% of the effect of non-O type on coronary artery disease susceptibility was mediated by increased low-density lipoprotein cholesterol level (P=7.8×10(-4)) and that 11% of the effect of non-O type on myocardial infarction risk was mediated by raised low-density lipoprotein cholesterol level (P=2.0×10(-3)).

CONCLUSIONS

In a model in which it is presumed that cholesterol is a mediator of the associations of ABO group with coronary artery disease and myocardial infarction, around 10% of the effect of non-O type on coronary artery disease and myocardial infarction susceptibility was mediated by its influence on low-density lipoprotein cholesterol level.

Tests of Mediation: Paradoxical Decline in Statistical Power as a Function of Mediator Collinearity

Increasing the correlation between the independent variable and the mediator (a coefficient) increases the effect size (ab) for mediation analysis; however, increasing a by definition increases collinearity in mediation models. As a result, the standard error of product tests increase. The variance inflation due to increases in a at some point outweighs the increase of the effect size (ab) and results in a loss of statistical power. This phenomenon also occurs with nonparametric bootstrapping approaches because the variance of the bootstrap distribution of ab approximates the variance expected from normal theory. Both variances increase dramatically when a exceeds the b coefficient, thus explaining the power decline with increases in a. Implications for statistical analysis and applied researchers are discussed.

Multi-cultural association of the serotonin transporter gene (SLC6A4) with substance use disorder

A number of studies have reported associations between the serotonin transporter gene (SLC6A4) and alcohol, heroin, cocaine, or methamphetamine abuse. Other studies have yielded contrary results. There are a number of reasons for non-replication, including inadequate statistical power, population stratification, and poor phenotype definition. This study was to test the association using a meta-analytic approach across a variety of racial and ethnic populations. Using the genotype data of 55 studies (7999 cases, 8264 controls, and 676 families or parent-offspring trios) published in the past 15 years, we have conducted comprehensive meta-analyses to examine the associations of the 5-HTTLPR and STin2 polymorphisms with substance use disorder. The meta-analyses support the associations of 5-HTTLPR with alcohol, heroin, cocaine, and methamphetamine dependence and abuse (eg, the smallest P-values were 0.0058 with odds ratio (OR)=0.54 (0.35, 0.84); 0.0024 with OR=0.77 (0.66, 0.91); 0.018 with OR=1.38 (1.06, 1.81); and 0.028 with OR=0.46 (0.23, 0.92) for alcohol, heroin, cocaine, and methamphetamine dependence/abuse, respectively). When all the phenotypes are combined, the P-value was 0.0006 with OR=0.86 (0.78, 0.94) in the combined European, Asian, and Mexican populations and P-value was 0.0028 with OR=1.41 (1.13, 1.78) in the African populations. Evidence of significant associations was also identified in other subgroup analyses regarding differently combined substance and populations. The effect sizes of 5-HTTLPR were comparable among the European, Asian, and Mexican populations, however, the risk allele was more frequent in Asians than in Europeans and Mexicans. The opposite directions of risk allele in African population might be driven by the opposite directions of risk allele in cocaine dependence. This meta-analysis supports that the association of the SLC6A4 gene with substance use disorder varies depending on substances with different risk allele frequencies in the multi-cultural populations. Further studies using larger sample size are warranted.

Depression in systemic lupus erythematosus patients is associated with link-polymorphism but not methylation status of the 5HTT promoter region

A higher prevalence of depression in systemic lupus erythematosus (SLE) patients has been reported, though the mechanism underlying this phenomenon remains unclear. The present study was conducted to explore whether the polymorphism and methylation status of the serotonin transporter gene (5HTT) promoter region (PR-5HTT) contribute to depression in SLE patients from both genetic and epigenetic perspectives. In this study, 96 SLE patients and 96 healthy controls (HCs) were recruited. Depression levels of all subjects were evaluated using the Hamilton Depression Rating Scale (HDRS). The serotonin transporter-linked polymorphism (5HTTLPR) and the DNA methylation status of PR-5HTT were detected in peripheral lymphocytes of SLE patients and HCs. The differences in 5HTTLPR and DNA methylation of PR-5HTT between SLEs and HCs were compared. In SLE patients, the frequencies of short allele (S) and SS genotype of 5HTTLPR were higher in depressive SLE (SLE-D) patients than in non-depressive SLE (SLE-ND) patients. The mean HDRS score of SS homozygote patients was higher than that of patients with SL/LL genotypes. Conversely, PR-5HTT was hypomethylated in HCs as well as SLE patients. There was no difference in the methylation status between HCs and SLEs. Thus, the functional expression of PR-5HTT may be primarily regulated by gene polymorphism and not by DNA methylation. The risk allele of 5HTTLPR appears to be a major contributor to depression in SLE patients.

A serotonin transporter gene (SLC6A4) polymorphism is associated with reduced risk of irritable bowel syndrome in American and Asian population: a meta-analysis

AIM

Association studies of serotonin transporter gene SLC6A4 I/S polymorphism and irritable bowel syndrome (IBS) have shown inconsistent and contradictory results among different populations. In the present study, meta-analysis was performed to evaluate the association between SLC6A4 I/S polymorphism and IBS susceptibility.

METHODOLOGY

Systemic assessment was performed for the published studies based on the association of SLC6A4 I/S polymorphism and IBS risk from PubMed (Medline), EMBASE search. A meta-analysis was done to appraise the said association. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for allele contrast, homozygous, heterozygous, dominant and recessive genetic model.

RESULTS

A total of twelve studies comprising 2068 IBS cases and 2076 controls were included in this meta-analysis. Overall, no significant results were obtained for S allele carrier (S vs. I: p=0.488; OR=1.073, 95% CI=0.879 to 1.311) Co-dominant (SS vs. II; p=0.587; OR=1.112, 95% CI=0.758 to 1.631), (IS vs. II; p=0.361; OR=0.878, 95% CI=0.665 to 1.160). Similarly, dominant (SS+IS vs. II: p=0.853; OR=0.974, 95% CI=0.736 to 1.288) and recessive (SS vs. II+IS: p=0.267; OR=1.172, 95% CI=0.886 to 1.522) genetic models did not demonstrate risk. In the subgroup population based analysis, reduced risks were found in American (IS vs. II: p=0.009; OR=0.685, 95% CI=0.516 to 0.908) and Asian (SS+IS vs. II; p=0.001; OR=0.116, 95% CI=0.068 to 0.197) population. However, no risk was observed in European population.

CONCLUSIONS

This investigation clearly demonstrates that SLC6A4 (Ins/Del) polymorphism is associated with reduced risk of IBS in American and Asian population. However, future well-designed studies with stratified case control and biological characterization will be needed to validate this finding.

Interaction of the serotonin transporter-linked polymorphic region and environmental adversity: increased amygdala-hypothalamus connectivity as a potential mechanism linking neural and endocrine hyperreactivity

BACKGROUND

Gene by environment (G×E) interaction between genetic variation in the promoter region of the serotonin transporter gene (serotonin transporter-linked polymorphic region [5-HTTLPR]) and stressful life events (SLEs) has been extensively studied in the context of depression. Recent findings suggest increased neural and endocrine stress sensitivity as a possible mechanism conveying elevated vulnerability to psychopathology. Furthermore, these G×E mediated alterations very likely reflect interrelated biological processes.

METHODS

In the present functional magnetic resonance imaging study, amygdala reactivity to fearful stimuli was assessed in healthy male adults (n = 44), who were previously found to differ with regard to endocrine stress reactivity as a function of 5-HTTLPR × SLEs. Furthermore, functional connectivity between the amygdala and the hypothalamus was measured as a potential mechanism linking elevated neural and endocrine responses during stressful/threatening situations. The study sample was carefully preselected regarding 5-HTTLPR genotype and SLEs.

RESULTS

We report significant G×E interaction on neural response patterns and functional amygdala-hypothalamus connectivity. Specifically, homozygous carriers of the 5-HTTLPR S' allele with a history of SLEs (S'S'/high SLEs group) displayed elevated bilateral amygdala activation in response to fearful faces. Within the same sample, a comparable G×E interaction effect has previously been demonstrated regarding increased cortisol reactivity, indicating a cross-validation of heightened biological stress sensitivity. Furthermore, S'S'/high SLEs subjects were characterized by an increased functional coupling between the right amygdala and the hypothalamus, thus indicating a potential link between neural and endocrine hyperreactivity.

CONCLUSIONS

The present findings contribute to the ongoing debate on 5-HTTLPR × SLEs interaction and are discussed with respect to clinical implications.

The 5-HTTLPR polymorphism is associated with altered hemodynamic responses during appetitive conditioning

BACKGROUND

Current models suggest that a variation in the promoter region of the serotonin transporter gene (5-HTTLPR) is associated with altered amygdala reactivity not only towards negative but also towards positive stimuli, which has been neglected in the past. This association may possibly convey an elevated vulnerability for psychopathology like abuse, craving, and relapses. Since appetitive conditioning is a crucial mechanism in the pathogenesis of these psychiatric disorders, the identification of specific factors contributing to interindividual variation is important.

METHODS

In the present study (N = 86), an appetitive conditioning paradigm was conducted, in which a neutral stimulus (CS+) was associated with appetitive stimuli, while a second stimulus (CS-) predicted their absence. Subjects were genotyped according to the 5-HTTLPR genotype.

RESULTS

As the main result, we report a significant association between the 5-HTTLPR genotype and hemodynamic responses. Individuals with the s-allele displayed elevated conditioned bilateral amygdala activity in contrast to l/l-allele carriers. Further, increased hemodynamic responses in s-allele carriers were also found in the extended emotional network including the orbitofrontal cortex, the thalamus, and the ventral striatum.

CONCLUSION

The present findings indicate an association of the 5-HTTLPR and altered conditioned responses in appetitive conditioning. Further, the findings contribute to the ongoing debate on 5-HTTLPR dependent hemodynamic response patterns by emphasizing that s-allele carriers are not exclusively biased towards fearful, but also towards positive stimuli. In conclusion, our results imply that s-allele carriers might be better described as hyper-reactive towards salient stimuli, which may convey vulnerability for the development of psychiatric disorders.

Clinical and pathogenic aspects of candidate genes for lithium prophylactic efficacy

A number of candidate genes for lithium prophylactic efficacy have been proposed, some of them being also associated with a predisposition to bipolar illness. The aim of the present study was to investigate a possible association between polymorphisms of 14 common genes with the quality of prophylactic lithium response in patients with bipolar mood disorder, in relation to the putative role of these genes in the pathogenesis of this disorder. Some association with lithium prophylactic efficacy was found for the polymorphisms of 5HTT, DRD1, COMT, BDNF and FYN genes, but not for 5HT2A, 5HT2C, DRD2, DRD3, DRD4, GSK-3, NTRK2, GRIN2B and MMP-9. Possible aspects of these genes with regard to the mechanism of lithium activity and pathogenesis of bipolar mood disorder are discussed.

Individual differences in neural correlates of fear conditioning as a function of 5-HTTLPR and stressful life events

Fear learning is a crucial process in the pathogeneses of psychiatric disorders, which highlights the need to identify specific factors contributing to interindividual variation. We hypothesized variation in the serotonin transporter gene (5-HTTLPR) and stressful life events (SLEs) to be associated with neural correlates of fear conditioning in a sample of healthy male adults (n = 47). Subjects were exposed to a differential fear conditioning paradigm after being preselected regarding 5-HTTLPR genotype and SLEs. Individual differences in brain activity as measured by functional magnetic resonance imaging (fMRI), skin conductance responses and preference ratings were assessed. We report significant variation in neural correlates of fear conditioning as a function of 5-HTTLPR genotype. Specifically, the conditioned stimulus (CS(+)) elicited elevated activity within the fear-network (amygdala, insula, thalamus, occipital cortex) in subjects carrying two copies of the 5-HTTLPR S' allele. Moreover, our results revealed preliminary evidence for a significant gene-by-environment interaction, such as homozygous carriers of the 5-HTTLPR S' allele with a history of SLEs demonstrated elevated reactivity to the CS(+) in the occipital cortex and the insula. Our findings contribute to the current debate on 5-HTTLPR x SLEs interaction by investigating crucial alterations on an intermediate phenotype level which may convey an elevated vulnerability for the development of psychopathology.

Validity and power of missing data imputation for extreme sampling and terminal measures designs in mediation analysis

Several authors have acknowledged that testing mediational hypotheses between treatments, genes, physiological measures, and behaviors may substantially advance our understanding of how these associations operate. In psychiatric research, the costs of measuring the putative mediator or the outcome can be prohibitive. Extreme sampling designs have been validated as methods for reducing study costs by increasing power per subject measured on the more expensive variable when assessing bivariate relationships. However, there exist concerns about how missing data can potentially bias the results. Additionally, most mediation analysis techniques presuppose the joint measurement of mediators and outcomes for all subjects. There have been limited methodological developments for techniques that can evaluate putative mediators in studies that have employed extreme sampling, resulting in missing data. We demonstrate that extreme (selective) sampling strategies can be beneficial in the context of mediation analyses. Handling the missing data with maximum likelihood (ML) resulted in minimal power loss and unbiased parameter estimates. We must be cautious, though, in recommending the ML approach for extreme sampling designs because it yielded inflated Type 1 error rates under some null conditions. Yet, the use of extreme sampling designs and methods to handle the resultant missing data presents a viable research strategy.

Serotonin transporter gene polymorphism and psychiatric disorders: is there a link?

Though still in infancy, the field of psychiatric genetics holds great potential to contribute to the development of new diagnostic and therapeutic options to treat these disorders. Among a large number of existing neurotransmitter systems, the serotonin system dysfunction has been implicated in many psychiatric disorders and therapeutic efficacy of many drugs is also thought to be based on modulation of serotonin. Serotonin transporter gene polymorphism is one of the most extensively studied polymorphisms in psychiatric behavioral genetics. In this article, we review the status of evidence for association between the serotonin gene polymorphism and some common mental disorders like affective disorders, post-traumatic stress disorder, obsessive-compulsive disorder, suicide, autism, and other anxiety and personality disorders. Going beyond traditional association studies, gene-environment interaction, currently gaining momentum, is also discussed in the review. While the existing information of psychiatric genetics is inadequate for putting into practice genetic testing in the diagnostic work-up of the psychiatric patient, if consistent in future research attempts, such results can be of great help to improve the clinical care of a vast majority of patients suffering from such disorders.

Ontogeny and regulation of the serotonin transporter: providing insights into human disorders

Serotonin (5-hydroxytryptamine, 5-HT) was one of the first neurotransmitters for which a role in development was identified. Pharmacological and gene knockout studies have revealed a critical role for 5-HT in numerous processes, including cell division, neuronal migration, differentiation and synaptogenesis. An excess in brain 5-HT appears to be mechanistically linked to abnormal brain development, which in turn is associated with neurological disorders. Ambient levels of 5-HT are controlled by a vast orchestra of proteins, including a multiplicity of pre- and post-synaptic 5-HT receptors, heteroreceptors, enzymes and transporters. The 5-HT transporter (SERT, 5-HTT) is arguably the most powerful regulator of ambient extracellular 5-HT. SERT is the high-affinity uptake mechanism for 5-HT and exerts tight control over the strength and duration of serotonergic neurotransmission. Perturbation of its expression level or function has been implicated in many diseases, prominent among them are psychiatric disorders. This review synthesizes existing information on the ontogeny of SERT during embryonic and early postnatal development though adolescence, along with factors that influence its expression and function during these critical developmental windows. We integrate this knowledge to emphasize how inappropriate SERT expression or its dysregulation may be linked to the pathophysiology of psychiatric, cardiovascular and gastrointestinal diseases.

Creativity and psychopathology: a shared vulnerability model

Creativity is considered a positive personal trait. However, highly creative people have demonstrated elevated risk for certain forms of psychopathology, including mood disorders, schizophrenia spectrum disorders, and alcoholism. A model of shared vulnerability explains the relation between creativity and psychopathology. This model, supported by recent findings from neuroscience and molecular genetics, suggests that the biological determinants conferring risk for psychopathology interact with protective cognitive factors to enhance creative ideation. Elements of shared vulnerability include cognitive disinhibition (which allows more stimuli into conscious awareness), an attentional style driven by novelty salience, and neural hyperconnectivity that may increase associations among disparate stimuli. These vulnerabilities interact with superior meta-cognitive protective factors, such as high IQ, increased working memory capacity, and enhanced cognitive flexibility, to enlarge the range and depth of stimuli available in conscious awareness to be manipulated and combined to form novel and original ideas.

Adverse childhood experiences (ACEs), genetic polymorphisms and neurochemical correlates in experimentation with psychotropic drugs among adolescents

Epidemiological and clinical data show frequent associations between adverse childhood experiences (ACEs) and substance abuse susceptibility particularly in adolescents. A large body of evidences suggests that the possible dysregulation of neuroendocrine responses as well as neurotransmitters function induced by childhood traumatic experiences and emotional neglect could constitute one of the essential biological changes implementing substance abuse vulnerability. Moreover, genotype variables and its environment interactions have been associated with an increased risk for early onset substance abuse. In this paper we present several data that support the hypothesis of the involvement of hypothalamus-pituitary-adrenal (HPA) axis in mediating the combined effect of early adverse experiences and gene variants affecting neurotransmission. The presented data also confirm the relationship between basal plasma levels of cortisol and ACTH, on the one hand, and retrospective measures of neglect during childhood on the other hand: the higher the mother and father neglect (CECA-Q) scores are, the higher the plasma levels of the two HPA hormones are. Furthermore, such positive relationship has been proved to be particularly effective and important when associated with the "S" promoter polymorphism of the gene encoding the 5-HTT transporter, both in homozygote and heterozygote individuals.

Methylation matters: interaction between methylation density and serotonin transporter genotype predicts unresolved loss or trauma

BACKGROUND

Do genetic or epigenetic factors play a role in making some individuals more vulnerable than others to loss of attachment figures or other traumatic experiences?

METHODS

DNA was obtained from growth phase entrained Epstein-Barr Virus (EBV) transformed lymphoblast cell lines from 143 adopted participants. Genotype of the serotonin transporter linked polymorphic region (5HTTLPR) was determined, and methylation ratios for each of the C-phosphate-G (CpG) residues were assessed using quantitative mass spectroscopy. Unresolved loss or trauma was established using the Berkeley Adult Attachment Interview.

RESULTS

Higher levels of methylation of the 5HTT promoter associated CpG island were associated with increased risk of unresolved responses to loss or other trauma in carriers of the usually protective 5HTTLPR//variant. The ss variant of 5HTTLPR predicted more unresolved loss or trauma, but only in case of lower levels of methylation. Higher levels of methylation of the ss variant were associated with less unresolved loss or other trauma.

CONCLUSIONS

Associations between 5HTTLPR polymorphisms and psychological problems are significantly altered by environmentally induced methylation patterns. Methylation may serve as the interface between adverse environment and the developing organism.

Decreased recognition of negative affect after selective serotonin reuptake inhibition is dependent on genotype

Selective serotonin reuptake inhibitors (SSRIs) are known to influence the information processing of emotional material in depressed patients and healthy controls. The functional polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) has been shown to interact with the effectiveness of serotonin reuptake inhibitors. It is not known whether 5-HTTLPR has an influence on emotional processing in healthy controls. We report first data with long-term SSRI administration after genetic characterization of 5-HTTLPR in a randomized, double-blind, placebo-controlled, crossover design. In 30 healthy controls, 15 homozygous for the long and 15 for the short allele of 5-HTTLPR, emotionally valent images were used to elicit positive or negative emotions. We found a diminished perception of sad and fearful information under SSRI which was significant in the long allele group. These findings emphasize the importance of genetic variance in emotion processing research.

The serotonin transporter gene and risk for alcohol dependence: a meta-analytic review

Previous studies have implicated a relationship between particular allelic variations of the serotonin transporter gene (5HTTLPR) and alcohol dependence. To provide a current estimate of the strength of this association, particularly in light of inconsistent results for 5HTTLPR, we conducted a meta-analytic review of the association between 5HTTLPR and a clinical diagnosis of alcohol dependence. Of 145 studies initially identified, 22 (including 8050 participants) met inclusion criteria. Results indicated that there was a significant albeit modest association between alcohol dependence diagnosis and the presence of at least 1 short allele (OR=1.15, 95% CI=1.01, 1.30, p<.05). Slightly more robust results were observed for participants who were homogeneous for the short allele (OR=1.21, 95% CI=1.02, 1.44, p<.05). These results were unrelated to sex and race/ethnicity of participants; however, the effect size was moderated by study sample size and publication year. Additionally, the fail-safe N analysis indicated potential publication bias. Therefore, although our review indicates that there is a significant association between 5HTTLPR and alcohol dependence diagnosis, this result should be interpreted with caution.

Inverse relationship between numbers of 5-HT transporter binding sites and life history of aggression and intermittent explosive disorder

The objective of this study was to determine if platelet 5-HT transporter (5-HTT) sites vary as a function of aggression, and/or impulsiveness, and differ as a function of Intermittent Explosive Disorder (IED). Accordingly, the number of platelet 5-HTT sites was assessed in 100 personality disordered (PD) individuals with varying degrees of aggressiveness. The number of platelet 5-HTT sites was assessed by examining the Bmax of H(3)-Paroxetine Binding to the blood platelet. Life history of aggression was assessed by Life History of Aggression. Impulsivity was assessed by the Barratt Impulsiveness Scale. Diagnoses of IED were made by both DSM-IV and Research Criteria. Examination of the data revealed that Bmax, but not Kd, values of Platelet H(3)-Paroxetine Binding correlated inversely with the LHA Aggression score (r=-.42 n=87, p<.001) but not with the BIS-11 Impulsivity score (r=.03, n=77, p=.777). PD subjects meeting Research Criteria for IED demonstrated a significant reduction in Bmax values for Platelet H(3)-Paroxetine Binding. These results were similar after accounting for the effect of lifetime history of depressive mood disorder on Bmax values for Platelet H(3)-Paroxetine Binding. These data indicate a significant inverse relationship between platelet 5-HTT and aggression, though not impulsivity, as a dimensional variable in personality disordered individuals. Results from the examination of IED as a categorical aggression variable suggest that Research, rather than DSM-IV, criteria better identify individuals with reduced numbers of platelet 5-HTT sites.

Alcohol response and consumption in adolescent rhesus macaques: life history and genetic influences

The use of alcohol by adolescents is a growing problem and has become an important research topic in the etiology of the alcohol use disorders. A key component of this research has been the development of animal models of adolescent alcohol consumption and alcohol response. Because of their extended period of adolescence, rhesus macaques are especially well suited for modeling alcohol-related phenotypes that contribute to the adolescent propensity for alcohol consumption. In this review, we discuss studies from our laboratory that have investigated both the initial response to acute alcohol administration and the consumption of alcohol in voluntary self-administration paradigms in adolescent rhesus macaques. These studies confirm that adolescence is a time of dynamic change both behaviorally and physiologically, and that alcohol response and alcohol consumption are influenced by life history variables, such as age, sex, and adverse early experience in the form of peer-rearing. Furthermore, genetic variants that alter functioning of the serotonin, endogenous opioid, and corticotropin-releasing hormone systems are shown to influence both physiological and behavioral outcomes, in some cases interacting with early experience to indicate gene by environment interactions. These findings highlight several of the pathways involved in alcohol response and consumption, namely reward, behavioral dyscontrol, and vulnerability to stress, and demonstrate a role for these pathways during the early stages of alcohol exposure in adolescence.

Boron-Doped Diamond Microelectrodes Reveal Reduced Serotonin Uptake Rates in Lymphocytes from Adult Rhesus Monkeys Carrying the Short Allele of the 5-HTTLPR

Uptake resolved by high-speed chronoamperometry on a second-by-second basis has revealed important differences in brain serotonin transporter function associated with genetic variability. Here, we use chronoamperometry to investigate variations in serotonin transport in primary lymphocytes associated with the rhesus serotonin transporter gene-linked polymorphism (rh5-HTTLPR), a promoter polymorphism whose orthologs occur only in higher order primates including humans. Serotonin clearance by lymphocytes is Na(+)-dependent and inhibited by the serotonin-selective reuptake inhibitor paroxetine (Paxil®), indicative of active uptake by serotonin transporters. Moreover, reductions in serotonin uptake rates are evident in lymphocytes from monkeys with one or two copies of the short 's' allele of the rh5-HTTLPR (s/s<s/l<l/l). These findings illustrate that rh5-HTTLPR-related alterations in serotonin uptake are present during adulthood in peripheral blood cells natively expressing serotonin transporters. Moreover, they suggest that lymphocytes can be used as peripheral biomarkers for investigating genetic or pharmacologic alterations in serotonin transporter function. Use of boron-doped diamond microelectrodes for measuring serotonin uptake, in contrast to carbon fiber microelectrodes used previously in the brain, enabled these high-sensitivity and high-resolution measurements. Boron-doped diamond microelectrodes show excellent signal-to-noise and signal-to-background ratios due mainly to low background currents and are highly resistant to fouling when exposed to lymphocytes or high concentrations of serotonin.

Recent developments in longitudinal studies of aging in the United States

We review recent developments in longitudinal studies of aging, focusing on the Wisconsin Longitudinal Study (WLS) and the Health and Retirement Study (HRS). Both studies are part of a trend toward biosocial surveys in which biological measurement is joined with traditional survey techniques, and a related trend toward greater harmonization across studies. Both studies have collected DNA samples and are working toward genotyping that would allow broadly based association studies. Increased attention to psychological measurement of personality and of cognitive ability using adaptive testing structures has also been shared across the studies. The HRS has expanded its economic measurement to longitudinal studies of consumption and to broader-based measurement of pension and Social Security wealth. It has added biomarkers of cardiovascular risk. The WLS has developed an integrated approach to the study of death and bereavement and an innovative use of high school yearbook photographs to capture information about health in early life of its participants.

Gene-environment interactions predict cortisol responses after acute stress: implications for the etiology of depression

BACKGROUND

Growing evidence suggests that the serotonin transporter polymorphism (5-HTTLPR) interacts with adverse environmental influences to produce an increased risk for the development of depression while the underlying mechanisms of this association remain largely unexplored. As one potential intermediate phenotype, we investigated alterations of hypothalamic-pituitary-adrenal (HPA) axis responses to stress in individuals with no history of psychopathology depending on both 5-HTTLPR and stressful life events.

METHODS

Healthy male adults (N=100) were genotyped and completed a questionnaire on severe stressful life events (Life Events Checklist). To test for gene-by-environment interactions on endocrine stress reactivity, subjects were exposed to a standardized laboratory stress task (Public Speaking). Saliva cortisol levels were obtained at 6 time points prior to the stressor and during an extended recovery period.

RESULTS

Subjects homozygous for the s-allele with a significant history of stressful life events exhibited markedly elevated cortisol secretions in response to the stressor compared to all other groups, indicating a significant gene-by-environment interaction on endocrine stress reactivity. No main effect of either 5-HTTLPR (biallelic and triallelic) or stressful life events on cortisol secretion patterns appeared.

CONCLUSION

This is the first study reporting that 5-HTTLPR and stressful life events interact to predict endocrine stress reactivity in a non-clinical sample. Our results underpin the potential moderating role of HPA-axis hyper-reactivity as a premorbid risk factor to increase the vulnerability for depression in subjects with low serotonin transporter efficiency and a history of severe life events.