Serotonin transporter gene (5-HTTLPR) and major psychoses

Associations of the serotonin transporter promoter polymorphism (5-HTTLPR) with bipolar disorder and treatment response: A systematic review and meta-analysis

BACKGROUND

Associations of the serotonin transporter promoter polymorphism (5-HTTLPR) with bipolar disorder (BPD) and treatment response in bipolar patients were not conclusive. This study not only assessed the association between the 5-HTTLPR and BPD with accumulating relevant studies, but also in the first time evaluated the effect of the 5-HTTLPR on both anti-depressive and anti-manic treatment responses in bipolar patients.

METHODS

PubMed, Embase, PsycINFO, Cochrane Library and Cochrane Control Trials databases were systematically searched before February 2017. This meta-analysis followed the PRISMA guidelines.

RESULTS

A total of 32 population-based studies (5567 cases and 6993 controls) and 9 family-based studies (837 trios) were finally screened out and statistically joined into a single meta-analysis that revealed an association between S allele and an increased risk of BPD (OR = 1.06, p = .038). Pooled analysis of the 32 population-based studies indicated an association of S-carrier genotypes with an increased risk of BPD (OR = 1.10, p = .029). Meanwhile, the association remained significant in Caucasians (OR = 1.15, p = .004), which could provide an enough power (88%) to detect a significant association. Regarding the treatment response studies, 6 studies reporting the relationship of the 5-HTTLPR in anti-depressive remission rate (1034 patients) and 7 studies reporting in response rate (1098 patients) were included for pooled analyses. We observed a significant association of S-carrier genotypes with a reduced anti-depressive remission rate (OR = 0.64, p = .006) but not with anti-depressive response rate. The association between the 5-HTTLPR with anti-manic response rate was not observed in the included 6 studies (676 patients).

CONCLUSIONS

The present study supported the presence of a marginal but detectable effect of the 5-HTTLPR on susceptibility to BPD. Moreover, the detected association in Caucasian was statistically reliable. Besides, the 5-HTTLPR was identified as a useful predictor for anti-depressive remission but not for anti-depressive or anti-manic response.

Association between the SLC6A4 gene and schizophrenia: an updated meta-analysis

BACKGROUND

In order to explore the association between the SLC6A4 gene and the risk of schizophrenia, an updated meta-analysis was conducted using a total of 46 scientific articles.

METHODS

Through a literature search, papers studied included 35 articles on serotonin-transporter-linked polymorphic region (5-HTTLPR) with 8,752 cases and 10,610 controls, 17 articles on second intron variable number of tandem repeats with 7,284 cases and 8,544 controls, four studies on rs1042173 with 1,351 cases and 2,101 controls, and four studies on rs140700 with 1,770 cases and 2,386 controls. Pooled, subgroup, and sensitivity analyses were performed, and the results were visualized by forest and funnel plots.

RESULTS

An association between 5-HTTLPR and the risk of schizophrenia was not found, except for an Indian subgroup analysis (P_z =0.014, OR =1.749, 95% CI =1.120-2.731). A 10 repeats/12 repeats (10R/12R) genotype was a protective factor against schizophrenia (P_z =0.020, OR =0.789, 95% CI =0.646-0.963), but a 12R/12R genotype was a risk factor for schizophrenia (P_z =0.004, OR =1.936, 95% CI =1.238-3.029) in the pooled analyses. In Caucasians, a GG genotype of rs1042173 may be a risk factor for schizophrenia (P_z =0.006, OR =1.299, 95% CI =1.079-1.565). No association was found between rs140700 and the risk for schizophrenia.

CONCLUSION

Through meta-analysis, we were able to gain insight into previously reported associations between SLC6A4 polymorphism and schizophrenia.

5-HTT mRNA level as a potential biomarker of treatment response in patients with major depression in a clinical trial

OBJECTIVES

To investigate whether the serotonin transporter (5-HTT or SERT or SLC6A4) mRNA level could be used as a biomarker of treatment response in patients with major depression treated with different antidepressants while controlling related factors.

METHODS

One hundred and nineteen patients with major depression were recruited; all genotyped for the 5-HTT polymorphism concerning 5-HTTLPR, rs25531, and STin2 VNTR, provided demographic data and completed relevant questionnaires. Duloxetine and paroxetine were administered over 32 weeks to these patients. The Hamilton depression rating scale (HDRS) and 5-HTT mRNA level were evaluated at baseline (Week 0), and at 8, 16, 24 and 32 weeks.

RESULTS

Improvement in depressive symptoms (HDRS score declined) and increasing in 5-HTT mRNA level were found with longer duration of antidepressant treatment in patients with major depression. Patients with more 5-HTTPR long-form alleles and STin2.12 alleles had poor antidepressant treatment response. Duloxetine may give a better treatment response than paroxetine. Using structural equation modeling (SEM), the 5-HTTLPR long-form had a direct positive association with the 5-HTT mRNA level and an indirect adverse relationship with the 5-HTT mRNA level through neuroticism and previous suicide attempts.

CONCLUSION

The 5-HTT mRNA level increased and correlated with the treatment response (HDRS score improvement) under 32-weeks antidepressants treatment clinical trial. We speculate that the 5-HTT mRNA level may be used as a potential biomarker of antidepressant treatment response.

A gene co-expression module implicating the mitochondrial electron transport chain is associated with long-term response to lithium treatment in bipolar affective disorder

Lithium is the first-line treatment for bipolar affective disorder (BPAD) but two-thirds of patients respond only partially or not at all. The reasons for this high variability in lithium response are not well understood. Transcriptome-wide profiling, which tests the interface between genes and the environment, represents a viable means of exploring the molecular mechanisms underlying lithium response variability. Thus, in the present study we performed co-expression network analyses of whole-blood-derived RNA-seq data from n = 50 lithium-treated BPAD patients. Lithium response was assessed using the well-validated ALDA scale, which we used to define both a continuous and a dichotomous measure. We identified a nominally significant correlation between a co-expression module comprising 46 genes and lithium response represented as a continuous (i.e., scale ranging 0-10) phenotype (cor = -0.299, p = 0.035). Forty-three of these 46 genes had reduced mRNA expression levels in better lithium responders relative to poorer responders, and the central regulators of this module were all mitochondrially-encoded (MT-ND1, MT-ATP6, MT-CYB). Accordingly, enrichment analyses indicated that genes involved in mitochondrial functioning were heavily over-represented in this module, specifically highlighting the electron transport chain (ETC) and oxidative phosphorylation (OXPHOS) as affected processes. Disrupted ETC and OXPHOS activity have previously been implicated in the pathophysiology of BPAD. Our data adds to previous evidence suggesting that a normalisation of these processes could be central to lithium's mode of action, and could underlie a favourable therapeutic response.

Depressive symptoms in schizophrenia and dopamine and serotonin gene polymorphisms

Although depressive symptoms seem to be frequent in schizophrenia they have received significantly less attention than other symptom domains. As impaired serotonergic and dopaminergic neurotransmission is implicated in the pathogenesis of depression and schizophrenia this study sought to investigate the putative association between several functional gene polymorphisms (SERT 5-HTTLPR, MAO-A VNTR, COMT Val158Met and DAT VNTR) and schizophrenia. Other objectives of this study were to closely examine schizophrenia symptom domains by performing factor analysis of the two most used instruments in this setting (Positive and negative syndrome scale - PANSS and Calgary depression rating scale - CDSS) and to examine the influence of investigated gene polymorphisms on the schizophrenia symptom domains, focusing on depressive scores. A total of 591 participants were included in the study (300 schizophrenic patients and 291 healthy volunteers). 192 (64%) of schizophrenic patients had significant depressive symptoms. Genotype distribution revealed no significant differences regarding all investigated polymorphisms except the separate gender analysis for MAO-A gene polymorphism which revealed significantly more allele 3 carriers in schizophrenic males. Factor analysis of the PANSS scale revealed the existence of five separate factors (symptom domains), while the CDSS scale revealed two distinct factors. Several investigated gene polymorphisms (mostly SERT and MAO-A, but also COMT) significantly influenced two factors from the PANSS (aggressive/impulsive and negative symptoms) and one from the CDSS scale (suicidality), respectively. Depressive symptoms in schizophrenic patients may be influenced by functional gene polymorphisms, especially those implicated in serotonergic neurotransmission.

An integrative review of methylation at the serotonin transporter gene and its dialogue with environmental risk factors, psychopathology and 5-HTTLPR

Gene-environment (G×E) interactions have largely been regarded as the root of many complex disorders, including several psychiatric disorders. In this regard, it has been hypothesized that epigenetic mechanisms may be the main mediators of such interactions. Of particular interest is the previously described interaction between psychosocial stress and genetic variability of the serotonin transporter gene (SLC6A4) in its polymorphic region 5-HTTLPR. Here we review the literature concerning SLC6A4 methylation in association with environmental, clinical or genetic variables. While SLC6A4 hypermethylation has typically been described to be independently associated with both early life stress and depressive disorders, only a few papers address whether methylation could mediate the interaction between stress and 5-HTTLPR in predicting psychopathological risk. Nevertheless, research preliminarily indicates a methylation-driven increased vulnerability of carriers of the short allele of 5-HTTLPR to psychiatric disorders when exposed to early stress or soon after exposure to stress.

Associations of 5HTTLPR polymorphism with major depressive disorder and alcohol dependence: A systematic review and meta-analysis

OBJECTIVE

The neurotransmitter serotonin is understood to control mood and drug response. Carrying a genetic variant in the serotonin transporter gene (5HTT) may increase the risk of major depressive disorder and alcohol dependence. Previous estimates of the association of the S allele of 5HTTLPR polymorphism with major depressive disorder and alcohol dependence have been inconsistent.

METHODS

For the systematic review, we used PubMed MEDLINE and Discovery of The University of Melbourne to search for all relevant case-control studies investigating the associations of 5HTTLPR polymorphism with major depressive disorder and alcohol dependence. Summary odds ratios (OR) and their 95% confidence intervals (CI) were estimated. To investigate whether year of publication, study population or diagnostic criteria used were potential sources of heterogeneity, we performed meta-regression analyses. Publication bias was assessed using Funnel plots and Egger's statistical tests.

RESULTS

We included 23 studies of major depressive disorder without alcohol dependence containing 3392 cases and 5093 controls, and 11 studies of alcohol dependence without major depressive disorder containing 2079 cases and 2273 controls. The summary OR for homozygote carriers of the S allele of 5HTTLPR polymorphism compared with heterozygote and non-carriers combined (SS vs SL+LL genotype) was 1.33 (95% CI = [1.19, 1.48]) for major depressive disorder and 1.18 (95% CI = [1.01, 1.38]) for alcohol dependence. The summary OR per S allele of 5HTTLPR polymorphism was 1.16 (95% CI = [1.08, 1.23]) for major depressive disorder and 1.12 (95% CI = [1.01, 1.23]) for alcohol dependence. Meta-regression models showed that the associations did not substantially change after adjusting for year of publication, study population and diagnostic criteria used. There was no evidence for publication bias of the studies included in our meta-analysis.

CONCLUSIONS

Our meta-analysis confirms that individuals with the homozygous S allele of 5HTTLPR polymorphism are at increased risks of major depressive disorder as well as alcohol dependence. Further studies are required to investigate the association between 5HTTLPR polymorphism and the comorbidity of major depressive disorder and alcohol dependence as well as gene × environmental interactions.

A review of genetic alterations in the serotonin pathway and their correlation with psychotic diseases and response to atypical antipsychotics

Serotonin is a neurotransmitter that plays a predominant role in mood regulation. The importance of the serotonin pathway in controlling behavior and mental status is well recognized. All the serotonin elements - serotonin receptors, serotonin transporter, tryptophan hydroxylase and monoamine oxidase proteins - can show alterations in terms of mRNA or protein levels and protein sequence, in schizophrenia and bipolar disorder. Additionally, when examining the genes sequences of all serotonin elements, several single nucleotide polymorphisms (SNPs) have been found to be more prevalent in schizophrenic or bipolar patients than in healthy individuals. Several of these alterations have been associated either with different phenotypes between patients and healthy individuals or with the response of psychiatric patients to the treatment with atypical antipsychotics. The complex pattern of genetic diversity within the serotonin pathway hampers efforts to identify the key variations contributing to an individual's susceptibility to the disease. In this review article, we summarize all genetic alterations found across the serotonin pathway, we provide information on whether and how they affect schizophrenia or bipolar disorder phenotypes, and, on the contribution of familial relationships on their detection frequencies. Furthermore, we provide evidence on whether and how specific gene polymorphisms affect the outcome of schizophrenic or bipolar patients of different ethnic groups, in response to treatment with atypical antipsychotics. All data are discussed thoroughly, providing prospective for future studies.

Depression with psychotic features is influenced by the polymorphism of the serotonin transporter gene

INTRODUCTION

Current diagnostic classifications regard psychotic symptoms during depressive episodes as indicators of depression severity. However, growing evidence suggests that depression with psychotic symptoms (MDP) may represent a distinct subtype of depression. In the course of the search for discriminating factors we tested the hypothesis that the serotonin transporter gene (5-HTTLPR) may interact with the manifestation of psychotic symptoms in acute depression.

METHODS

112 inpatients (61 female) with a depressive episode (16 bipolar, 86 unipolar) at admission were genotyped for 5-HTTLPR variants. Psychotic symptoms und general psychopathology were evaluated comprehensively using the Manual of the Association for Methodology and Documentation in Psychiatry (Arbeitsgemeinschaft für Methodik und Dokumentation in der Psychiatrie, 1981). For statistical analysis a chi-square test and a logistic regression model was used.

RESULTS

16 (14.3%) out of 112 patients were currently presenting with psychotic symptoms. The primary finding of our study was the higher prevalence of the s-allele of the 5-HTTLPR within the group of MDP patients (Pearson χ²=7.87; df=2; p<0.03). Secondly, in a logistic regression model, 5-HTTLPR was found to significantly contribute to the diagnosis of MDP (χ²=6.5; df=1; p=0.01). This effect was even more pronounced upon comparing only severely depressed patients with MDP patients. From a psychopathological perspective, MDP patients showed higher AMDP hostility and apathy scores but equal AMDP depression scores.

DISCUSSION

This is the first study to show an influence of 5-HTTLPR on psychotic symptoms in acutely depressed patients.

LIMITATIONS

The lack of a control group and the relatively small sample size limits the present study's findings, thus replication in a larger sample is necessary.

Meta-analysis confirms a functional polymorphism (5-HTTLPR) in the serotonin transporter gene conferring risk of bipolar disorder in European populations

The serotonin transporter (5-HTT) is a candidate risk gene for bipolar disorder, and a functional polymorphism of 44-bp insertion/deletion (5-HTTLPR) located in the promoter region of this gene has been investigated for the association with the illness extensively among worldwide populations, but overall results were inconsistent and its role in the disorder remains unclear. The present study attempts to find its potential association with bipolar disorder using meta-analyzes that maximize the statistical power. We applied meta-analysis techniques by combining all available case-control studies of 5-HTTLPR and bipolar disorder in samples of European ancestry (with a total of 3778 cases and 4997 controls), and we assessed the evidence for allelic associations, heterogeneity among different studies, influence of each single study, and potential publication bias. The short allele (S allele) of 5-HTTLPR showed a significant association with bipolar disorder in our meta-analysis (odds ratio=1.10, p-value=0.005), suggesting it is likely a risk polymorphism for the illness, and the observed OR is consistent with other susceptibility loci identified through recent large-scale genetic association studies on bipolar disorder, which could be regarded simply as a small but detectable effects.

Meta-analysis of genetic association studies on bipolar disorder

Numerous candidate gene association studies of bipolar disorder (BP) have been carried out, but the results have been inconsistent. Individual studies are typically underpowered to detect associations with genes of small effect sizes. We conducted a meta-analysis of published candidate gene studies to evaluate the cumulative evidence. We systematically searched for all published candidate gene association studies of BP. We then carried out a random-effects meta-analysis on all polymorphisms that were reported on by three or more case-control studies. The results from meta-analyses of these genes were compared with the findings from a recent mega-analysis of eleven genome-wide association studies (GWAS) in BP performed by the Psychiatric GWAS Consortium (PGC). A total of 487 articles were included in our review. Among these, 33 polymorphisms in 18 genes were reported on by three or more case-control studies and included in the random-effects meta-analysis. Polymorphisms in BDNF, DRD4, DAOA, and TPH1, were found to be nominally significant with a P-value < 0.05. However, none of the findings were significant after correction for multiple testing. Moreover, none of these polymorphisms were nominally significant in the PGC-BP GWAS. A number of plausible candidate genes have been previously associated with BP. However, the lack of robust findings in our review of these candidate genes highlights the need for more atheoretical approaches to study the genetics of BP afforded by GWAS. The results of this meta-analysis and from other on-going genomic experiments in BP are available online at Metamoodics (http://metamoodics.igm.jhmi.edu).

Behavioural genetics of the serotonin transporter

The serotonin transporter is a key regulator of the bioavailability of serotonin and therefore any modulation in the expression or action of the transporter would be expected to have consequences on behaviour. The transporter has therefore become a target for pharmaceutical intervention in behavioural and mood disorders. The search for polymorphic variants in the transporter that would associate with neurological disorders has been extensive but has become focused on two domains which are both termed variable number tandem repeat (VNTR)polymorphisms. Both of these VNTRs are in non-coding DNA and therefore proposed to be mechanistically involved in a disorder through their ability to modulate transcriptional or post-transcriptional regulation of the transporter. The most extensively studied is in the promoter and is a bi-allelic insertion/deletion found in the 50 promoter region of the gene 1.2 kb upstream of the transcriptional start site. This VNTR, termed, 5-HTTLPR was initially identified as two variants containing either, 14 (short/deletion) or 16 (long/insertion) copies of a 22 bp repeat. A second widely studied VNTR found in the non-coding region of the transporter is located within intron 2 and comprises 9, 10 or 12 copies of a16–17 bp repeat termed, STin2.9, STin2.10 and STin2.12, respectively. These VNTR polymorphisms have been associated with a range of behavioural and psychiatric disorders including depression, OCD, anxiety and schizophrenia, however often the lack of reproducibility in different cohorts has led to debate on the actual association of the polymorphisms with this extensive range of neurological conditions. Here we review these two polymorphic VNTRs in depth and relate that to pharmaceutical response, their ability to regulate differential transporter expression, their core involvement in gene-environment interaction and their genetic association with specific disorders.

Response to treatment in bipolar disorder

PURPOSE OF REVIEW

Bipolar disorder is a complex psychiatric condition that has been shown to carry a great degree of genetic loading. This review addresses current research in the genetics of treatment response in bipolar disorder, with a focus on findings that have shaped our understanding of the changing direction of this field in light of recent technological advancements.

RECENT FINDINGS

The recent publications in bipolar disorder treatment response have helped consolidate or improve upon knowledge of susceptibility loci and genes in the field. There seems to be an increasing trend toward functionally assessing the role played by putative candidate genes and molecular factors modulating expression in bipolar disorder, as well as a movement toward more global, pathway and genome-wide-oriented research.

SUMMARY

Genetic and molecular research to date in bipolar disorder treatment response has not completely answered all the lingering questions in the field, but has contributed to the development of a more patient-based understanding of treatment. In order to apply these findings at a clinical level, more comprehensive treatment response studies are imperative, combining recent advances in high-throughput genomics with functional molecular research.

Association of the 5- HTTLPR genotype and unipolar depression: a meta-analysis

BACKGROUND

We sought to ascertain the strength of evidence for association between the 5-HTTLPR polymorphism and unipolar depression.

METHOD

We applied meta-analytic techniques to data from relevant published studies, and obtained an estimate of the likely magnitude of effect of any association. We also tested for possible publication bias, and explored the impact of various study design characteristics on the magnitude of the observed effect size.

RESULTS

Meta-analysis indicated evidence of a small but statistically significant association between the 5-HTTLPR polymorphism and unipolar depression [odds ratio (OR) 1.08, 95% confidence interval (CI) 1.03-1.12]. This remained significant when data from samples of European and East Asian ancestry were analyzed separately. In all cases there was evidence of significant between-study heterogeneity, although the observed associations were robust to the application of a random-effects framework.

CONCLUSIONS

Our results support the presence of a small effect of a polymorphism in the serotonin transporter promoter on susceptibility to depression. However, we caution that it is possible that the effect has an artifactual basis, rather than a biological origin.

Analysis of the serotonin transporter promoter rs25531 polymorphism in premenstrual dysphoric disorder

OBJECTIVE

The objective of this study was to investigate whether the functional rs25531 promoter polymorphism in the serotonin transporter gene is associated with premenstrual dysphoric disorder.

STUDY DESIGN

The study sample comprised 53 women with clinically diagnosed premenstrual dysphoric disorder (age range, 27-46 years; mean, 37.7 years) and 52 healthy control subjects (age range, 22-48 years; mean, 36.2 years). The rs25531 polymorphism was genotyped in both groups. Because of its close proximity to rs25531, the 5-HTTLPR promoter polymorphism was also genotyped. Genotype and allele frequencies for rs25531 and for the composite 5-HTTLPR/rs25531 marker were analyzed by chi(2) test.

RESULTS

There was no significant association between any genotype and clinical category and no significant allele distribution profiles for rs25531 or 5-HTTLPR/rs25531 in either the premenstrual dysphoric disorder or the control groups.

CONCLUSION

These findings do not support a major role for rs25531, either in isolation or combined with 5-HTTLPR, in contributing to susceptibility to premenstrual dysphoria.

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.

The combined effects of the 5-HTTLPR and 5-HTR1A genes modulates the relationship between negative life events and major depressive disorder in a Chinese population

BACKGROUND

Serotonin transporter (5-HTT) and 5-HT receptor (5-HTR) involved in the neurotransmission of 5-HT may play an important role in the development of major depression disorder (MDD). Several lines of evidence suggested that the gene-environment interaction may confer susceptibility to depression. The aim of this study is to analyze the combined effect of four serotonin-related genes and two environmental factors on MDD in a Chinese population.

METHODS

This study recruited a total of 401 patients with MDD and 391 age- and gender-matched control subjects. They were all Chinese Han origin. Negative life events and objective social supports were assessed using standard rating scales. Six polymorphisms in the four serotonin-related genes (5-HTT, 5-HTR1A, 5-HTR1B and 5-HTR2A) were selected to detect. The analyses of the gene-environment interactions were performed by the Multifactor Dimensionality Reduction (MDR).

RESULTS

Allelic associations between patients with MDD and controls were observed for the polymorphism of 5-HTTLPR and for rs6295 at the 5-HTR1A locus. The 5-HTTLPR polymorphism was associated with negative life events on MDD. A three-way interaction between the 5-HTTLPR polymorphism, rs6295 and negative life events on MDD was found in the individuals aged from 20 years to 29 years. In addition, the individuals carrying the L/L genotype of 5-HTTLPR could be susceptible to MDD when exposed to negative life events.

CONCLUSIONS

The 5-HTTLPR polymorphism may modify the interaction between negative life events and MDD in the Chinese population. To our knowledge, this is the first report on the combined effect for the 5-HTTLPR polymorphism and 5-HTR1A genes on modifying the response to negative life events conferring susceptibility to MDD in the 20-29 year group.

No association of serotonin transporter polymorphism (5-HTTVNTR and 5-HTTLPR) with characteristics and treatment response to atypical antipsychotic agents in schizophrenic patients

BACKGROUND

Serotonin transporter is a candidate gene for the pathogenesis of some psychiatric disorders. The aim of this study was to examine the role of the serotonin transporter gene polymorphism in the clinical aspects of schizophrenia including symptomatology and therapeutic response.

METHODS

This study comprised 141 unrelated patients who strictly met the DSM-IV criteria for schizophrenia and 115 control subjects. All subjects were of Korean ethnicity. Serotonin transporter intron 2 VNTR polymorphism (5-HTTVNTR) and serotonin transporter linked polymorphic region polymorphism (5-HTTLPR) were analyzed in schizophrenia patients and control subjects. The Positive and Negative Symptom Scale (PANSS) was used at baseline and 6 weeks after atypical antipsychotic treatment to evaluate the clinical symptoms. Body mass index (BMI), the Barnes Akathisia Rating Scale (BARS), the Simpson-Angus Rating Scale (EPS) for adverse effect and the Calgary Depression rating Scale for Schizophrenia (CDSS) were measured.

RESULTS

There were no significant differences in the frequency of genotypes between schizophrenia patients and control subjects. There were no significant differences in PANSS scores before treatment according to the serotonin transporter genotypes. Treatment response after atypical antipsychotics did not differ among the genotypes. No difference was shown among the genotypes for the scales in adverse effects and depression (BMI, BARS, EPS, CDSS).

CONCLUSIONS

Our results suggest that the serotonin transporter polymorphism does not seem to be a susceptibility factor for schizophrenia. Similarly, the serotonin transporter polymorphism might not affect the therapeutic response and adverse effect to atypical antipsychotics in Korean patients with schizophrenia. Further studies with a larger number of subjects are required to better understand the role of the serotonin transporter polymorphism in schizophrenia.

Haplotype analysis confirms association of the serotonin transporter (5-HTT) gene with schizophrenia in the Han Chinese population

Serotonin transmission has long been suspected as being involved in the pathogenesis of schizophrenia. 5-HTT is a promising candidate gene for schizophrenia due to its critical role in regulating serotonin transmission and role in the mechanism of the atypical antipsychotic drugs. A common polymorphism STin2 VNTR in the 5-HTT gene has been extensively investigated in the genetic association studies, but the results are conflicting. Meanwhile, the SNPs of the 5-HTT gene have been much less explored. We therefore conducted a case-control study of the association between STin2 VNTR and three tagging SNPs in 5-HTT and schizophrenia in the Han Chinese population based on a cohort of 329 schizophrenic patients and 288 control subjects. No association was found in the single locus, but haplotype-based analyses revealed significant association between two haplotypes with schizophrenia even after Bonferroni correction (P=0.00000538 and 0.011).

Serotonin receptor HTR1A and HTR2C variants and personality traits in suicide attempters and controls

INTRODUCTION

Serotonin has been extensively studied in relation to both personality features and suicidal behaviours.

OBJECTIVE

In this study, we considered the association between the serotonin receptor 1A (HTR1A) and 2C (HTR2C) SNPs and personality traits, as measured by the Temperament and Character Inventory (TCI), in a sample of suicide patients and healthy volunteers.

METHODS

The SNPs considered were, for HTR1A rs1423691, rs878567 and rs6295, and for HTR2C rs547536, rs2192372, rs6318, rs2428707, rs4272555 and rs1801412. The sample was composed of three groups: two German samples, consisting of a healthy control group of 289 subjects (42.6% males, mean age: 45.2+/-14.9) and a psychiatric patient group of 111 suicide attempters (38.7% males, mean age: 39.2+/-13.6), and an Italian sample, composed of 64 mood disorder patients (35.9% males, mean age: 43.0+/-14.8). In the German samples all the SNPs were investigated, while in the Italian sample only the HTR1A rs6295 and the HTR2C rs6318 SNPs were considered.

RESULTS

Controlling for sex, age and educational level, single markers and haplotypes were not or only marginally associated with personality dimensions.

CONCLUSIONS

Our study does not support the role of HTR1A and HTR2C gene variants on personality traits in both healthy volunteers and mood disorder patients.

The serotonin transporter 5-HTTPR polymorphism is associated with current and lifetime depression in persons with chronic psychotic disorders

OBJECTIVE

Variation in the serotonin transporter gene (SLC6A4) promoter region has been shown to influence depression in persons who have been exposed to a number of stressful life events.

METHOD

We evaluated whether genetic variation in 5-HTTLPR, influences current depression, lifetime history of depression and quantitative measures of depression in persons with chronic psychotic disorders. This is an association study of a genetic variant with quantitative and categorical definitions of depression conducted in the southwest US, Mexico and Costa Rica. We analyzed 260 subjects with a history of psychosis, from a sample of 129 families.

RESULTS

We found that persons carrying at least one short allele had a statistically significant increased lifetime risk for depressive syndromes (P < 0.02, odds ratio 2.18, 95% CI 1.10-4.20).

CONCLUSION

The 'ss' or 'sl' genotype at the 5-HTTLPR promoter polymorphic locus increases the risk of psychotic individuals to develop major depression during the course of their illness.

Molecular epidemiology of major depressive disorder

Major depressive disorder causes significant morbidity, affecting people's ability to work, function in relationships, and engage in social activities. Moreover, major depressive disorder increases the risk of suicidal ideation, attempted suicide and death by completed suicide. There is evidence that chronic stress can cause major depressive disorder. As for genetic factors, only minor susceptibility genes have been reliably identified. The serotonin system provides a logical source of susceptibility genes for depression, because this system is the target of selective serotonin reuptake-inhibitor drugs that are effective in treating depression. The 5-hydroxytryptamine (serotonin) transporter (5-HTT) has received particular attention because it is involved in the reuptake of serotonin at brain synapses. One common polymorphic variant of the 5-HTT-linked polymorphic region (5-HTTLPR), which affects the promoter of the 5-HTT gene, causes reduced uptake of the neurotransmitter serotonin into the presynaptic cells in the brain. The authors discussed the relationship between genetic polymorphisms and major depressive disorder, with special emphasis on the 5-HTTTLPR polymorphism. As the 5-HTTLPR polymorphism was significantly associated with an increased risk of major depressive disorder, the 5-HTT gene may be a candidate for a major depressive disorder susceptibility gene. As major depressive disorder is a multifactorial disease, an improved understanding of the interplay of environmental and genetic polymorphisms at multiple loci may help identify individuals who are at increased risk for major depressive disorder. Hopefully, in the future we will be able to screen for major depressive disorder susceptibility by using specific biomarkers.

Interaction between SERTPR and stressful life events on response to antidepressant treatment

A polymorphism within the serotonin transporter gene (SERTPR) has been repeatedly associated to mood disorders and response to SSRIs treatment. Recent evidence suggested that influence of genetic effect of SERTPR might be modulated by stress, particularly as regard the development of anxious-depressive symptoms. Nevertheless, there is no information about the role of stressors as potential modulator of SERTPR effects on depressive outcome during pharmacological treatment. In a sample of 159 mood disorder patients treated with fluvoxamine, we found stressors preceding the onset of the illness significantly influencing the genetic effect exerted by SERTPR on response after 6 weeks of treatment. This preliminary finding supports the idea of complex interaction between biological and environmental factors underlying the efficacy of biological treatments, other than liability for mood disorders. Nevertheless, many limitations characterize the present investigation and well-funded studies on larger samples are required.

A controlled pharmacogenetic trial of sibutramine on weight loss and body composition in obese or overweight adults

BACKGROUND & AIMS

Weight loss in response to sibutramine is highly variable. We assessed the association of specific markers of polymorphisms of candidate alpha2A adrenoreceptor, 5-HT transporter, and GNbeta3 genes and weight loss with sibutramine.

METHODS

We conducted a randomized, double-blind, pharmacogenetic study of behavioral therapy and sibutramine (10 or 15 mg daily) or placebo for 12 weeks in 181 overweight or obese participants. We measured body weight, body mass index, body composition, gastric emptying, and genetic variation (alpha2A C1291G, 5-HTTLPR, and GNbeta3 C825T genotypes). Analysis of covariance was used to assess treatment effects on and associations of the specific markers of candidate genes with weight loss and body composition.

RESULTS

Sibutramine, 10 and 15 mg, caused weight loss (P = .009); there was a statistically significant gene by dose interaction for GNbeta3 genotype. For each candidate gene, significant treatment effects at 12 weeks were observed (P < .017) for all specific genotype variants (Delta weight loss in the 2 sibutramine doses vs placebo): alpha2A CC (Delta, approximately 5 kg), GNbeta3 TC/TT (Delta, approximately 6 kg), and 5-HTTLPR LS/SS (Delta, approximately 4.5 kg). Gene pairs resulted in significantly greater sibutramine treatment effects on weight (both P < .002): in participants with 5-HTTLPR LS/SS with GNbeta3 TC/TT; Delta, approximately 6 kg and those with alpha2A CC with GNbeta3 TC/TT; Delta, approximately 8 kg; however, effects were not synergistic. Treatment with sibutramine also resulted in significantly greater reduction of body fat for specific alpha2A CC and GNbeta3 TC/TT genotype variants individually (both P < .02).

CONCLUSIONS

Patient selection based on candidate genes may enhance response to multidimensional sibutramine and behavioral therapy for obesity.

Serotonin transporter genotype and depressive phenotype determination by discriminant analysis of glucose metabolism under acute tryptophan depletion

Acute tryptophan depletion (ATD) putatively results in a transient reduction in central serotonin transmission, and induces depressed mood in some un-medicated subjects with remitted major depressive disorder (MDD). The 5-HT transporter promoter region length polymorphism (5-HTTLPR) has been shown to influence behavioral and metabolic responses to ATD, as well as the risk for developing MDD within the context of stress. The current study investigates the relationships between 5-HTTLPR genotype, neurophysiologic response to ATD, and diagnostic phenotype (healthy control subjects versus MDD subjects differentiated by their depressive response to ATD) using (18)FDG-PET. Un-medicated subjects with remitted MDD and healthy controls were genotyped for the long (l) and short (s) alleles of the 5-HTTLPR polymorphism and categorized into one of three genotypes. On two separate occasions, subjects received either a placebo or an amino acid mixture designed to deplete plasma tryptophan, followed by (18)FDG-PET scanning. Depressive symptoms were rated to determine the diagnostic phenotype. Descriptive and predictive discriminant analyses were performed using brain regional metabolic data to classify according to phenotype and genotype. Overall, 79% of the cases were classified correctly by genotype, and 85% were classified correctly by phenotype. In a leave-one-out cross-validation, 72% of the subjects were classified correctly as carrying an s-allele, and 79% of the subjects were classified correctly by primary diagnosis. The robust nature of the classification results indicates that much of the variance in metabolic response to ATD is accounted for by genotypic and phenotypic category.

Association of unipolar depression with gene polymorphisms in the serotonergic pathways in Han Chinese

OBJECTIVE

The present study aims to investigate the association of unipolar depression (UPD) with six serotonergic gene polymorphisms in Han Chinese.

METHODS

One hundred and thirty-two UPD patients and 180 healthy controls were genotyped for polymorphisms of six serotonergic genes, including tryptophan hydroxylase (TPH1 A218C), serotonin transporter promoter region (5-HTTLPR), serotonin receptor 2A (5-HT2AR -1438G/A), serotonin receptor 2C (5-HT2CR Cys23Ser), serotonin receptor 6 (5-HT6R C267T) and serotonin receptor 1Dβ (5-HT1DβR T371G). Symptomatic clusters were evaluated by the 24-item Hamilton Rating Scale for Depression (HAMD).

RESULTS

The frequencies of S/S genotype and S allele in 5-HTTLPR polymorphism were significantly higher in UPD patients than in healthy controls. There was a significant difference in distributions of genotypes in 5-HT2CR Cys23Ser polymorphism between UPD patients and control subjects, but the difference became no significant when the data were further stratified by gender. The patients with genotypes G/G and T/G of 5-HT1DβR T371G polymorphism had significantly lower scores of diurnal variation evaluated by HAMD than those with genotype T/T, while the patients with genotype T/G had significantly higher scores of hopelessness than those with genotypes G/G and T/T. There were no significant differences in genotypic and allelic distributions of TPH1 A218C, 5-HT2AR -1438G/A or 5-HT6R C267T polymorphisms between the case and control groups.

CONCLUSION

The study demonstrates that 5-HTTLPR and 5-HT2CR Cys23Ser polymorphisms might contribute to susceptibility of UPD, and the genotype T/T in 5-HT1DβR T371G polymorphism might be a risk factor for diurnal variation, while T/G might be a protective factor against hopelessness in Han Chinese populations.

Monoamine metabolites level in CSF is related to the 5-HTT gene polymorphism in treatment-resistant depression

The serotonin (5-hydroxytryptamine) transporter (5-HTT) is considered to affect the pathogenesis of mood disorders. Large number of genetic association studies between 5-HTT functional polymorphisms and vulnerability of mood disorders and therapeutic response to antidepressants has been carried out. We investigated the influence of 5-HTT-linked polymorphic region (5-HTTLPR) and 5-HTT 17 bp variable number of tandem repeat polymorphism (5-HTTVNTR) polymorphisms on concentrations of monoamine metabolites in cerebrospinal fluid (CSF) among treatment-resistant patients with mood disorders. Subjects were 119 Swedish patients with persistent mood disorders and 141 healthy subjects. In 112 of these patients, we measured 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol in CSF. Genotyping for 5-HTT polymorphisms from genomic DNA was carried out by PCR. There was no significant difference in allele/genotype frequency between patients and healthy subjects. In patients with mood disorders, we found significant difference in mean 5-HIAA concentration between 5-HTTLPR genotypes (p=0.03). Although the 5-HIAA concentration showed a tendency to be higher in short (S) carriers than in non-S carriers of the 5-HTTLPR in patients (p=0.06), when considering patients with major depressive disorder (MDD), the 5-HIAA concentration was significantly higher among S carriers than among non-S carriers (p=0.02). Moreover, the 5-HIAA concentration was higher in S/S subjects compared to long (L)/L (p=0.0001) and L/S (p=0.002) subjects in patients with MDD. Similarly, there was higher HVA concentration in S/S subjects compared to L/L (p=0.002) and L/S subjects (p=0.002). There was no effect of 5-HTTVNTR. Our findings show that the 5-HTTLPR polymorphism affects 5-HIAA and HVA concentrations among treatment-resistant patients with mood disorders.

Tryptophan breakdown pathway in bipolar mania

The upregulation of the initiating step of the kynurenine pathway was demonstrated in postmortem anterior cingulated cortex from individuals with schizophrenia and bipolar disorder. However, the tryptophan and kynurenine metabolism in bipolar mania patients especially in drug naïve state has not been clearly explored. This study explored the plasma tryptophan and its competing amino acids, kynurenine, kynurenic acid and 3-hydroxyanthranillic acid and their association with psychopathological scores in 39 drug naïve and drug-free bipolar manic patients in comparison with 80 healthy controls. When age and gender were controlled in multivariate analysis, bipolar manic patients have significantly lower tryptophan index than normal controls (f=9.779, p=0.004). The mean plasma tryptophan concentration and mean tryptophan index were reduced and mean tryptophan breakdown index was increased significantly after a 6-week treatment. The reduction in plasma tryptophan and reduction in tryptophan index showed significant negative correlation with reduction in YMRS score (r=-0.577, p=0.019 and r=-0.520, p=0.039 respectively). The reduction in YMRS also showed positive correlation with both plasma tryptophan concentration and tryptophan index both at the time of admission (r=0.464, p=0.019 and r=0.4, p=0.047 respectively) and discharged (r=0.529, p=0.035 and r=0.607, p=0.013 respectively). The reduction in BPRS score also showed positive correlation with tryptophan index at the time of discharge (r=0.406, p=0.044). These findings indicated the involvement of bi-directional tryptophan metabolism and kynurenine pathway in pathophysiology and response to medication in bipolar mania.

5-HT2A SNPs and the Temperament and Character Inventory

Temperamental traits, the most basic part of personality, have been largely correlated with neurotransmitter systems and are under genetic control. Among serotonin candidates, the 2A receptor (5-HT(2A)) received considerable attention. We analyzed four SNPs (rs643627, rs594242, rs6311 and rs6313) in the 5-HT(2A) gene and their association with personality traits, as measured with the Temperament and Character Inventory (TCI). The sample was composed of three sub-groups: two German sub-samples, consisting of a healthy group of 289 subjects (42.6% males, mean age: 45.2+/-14.9) and a psychiatric patient group of 111 suicide attempters (38.7% males, mean age: 39.2+/-13.6), and an Italian sub-sample, composed of 60 mood disorder patients (35.0% males, mean age: 44.0+/-14.8). Controlling for sex, age and educational level, the SNPs were not strongly associated with personality dimensions. Only the rs594242 showed an association with Self-Directedness (p=0.003) in the German sample, while rs6313 was marginally associated with Novelty Seeking (p=0.01) in the Italian sample. We conclude that 5-HT(2A) SNPs may marginally modulate personality traits but further studies are required.

Pharmacogenetics and pharmacogenomics of schizophrenia: a review of last decade of research

The last decade of research into the pharmacogenetics of antipsychotics has seen the development of genetic tests to determine the patients' metabolic status and the first attempts at personalization of antipsychotic treatment. The most significant results are the association between drug metabolic polymorphisms, mainly in cytochrome P450 genes, with variations in drug metabolic rates and side effects. Patients with genetically determined CYP2D6 poor metabolizer (PMs) status may require lower doses of antipsychotic. Alternatively, CYP2D6 ultrarapid matabolizers (UMs) will need increased drug dosage to obtain therapeutic response. Additionally, polymorphisms in dopamine and serotonin receptor genes are repeatedly found associated with response phenotypes, probably reflecting the strong affinities that most antipsychotics display for these receptors. In particular, there is important evidence suggesting association between dopamine 2 receptor (D2) polymorphisms (Taq I and -141-C Ins/Del) and a dopamine 3 receptor (D3) polymorphism (Ser9Gly) with antipsychotic response and drug-induced tardive dyskinesia. Additionally, there is accumulating evidence indicating the influence of a 5-HT2C polymorphism (-759-T/C) in antipsychotic-induced weight gain. Application of this knowledge to clinical practice is slowly gathering pace, with pretreatment determination of individual's drug metabolic rates, via CYP genotyping, leading the field. Genetic determination of patients' metabolic status is expected to bring clinical benefits by helping to adjust therapeutic doses and reduce adverse reactions. Genetic tests for the pretreatment prediction of antipsychotic response, although still in its infancy, have obvious implications for the selection and improvement of antipsychotic treatment. These developments can be considered as successes, but the objectives of bringing pharmacogenetic and pharmacogenomic research in psychiatric clinical practice are far from being realized. Further development of genetic tests is required before the concept of tailored treatment can be applied to psychopharmatherapy. This review aims to summarize the key findings from the last decade of research in the field. Current knowledge on genetic prediction of drug metabolic status, general response and drug-induced side effects will be reviewed and future pharmacogenomic and epigenetic research will be discussed.

Association study of serotonin 2A receptor (5-HT2A) and serotonin transporter (5-HTT) gene polymorphisms with schizophrenia

OBJECTIVE

To investigate (i) the association between four serotonergic polymorphisms (A-1438G and T102C of the 5-HT2A receptor gene, and 5-HTT VNTR and 5-HTTLPR of the 5-HT transporter gene) and schizophrenia and (ii) the potential interaction of those polymorphisms in the development of schizophrenia.

SUBJECTS AND METHODS

227 outpatients with schizophrenia (DSM-IV criteria) and 420 unrelated healthy controls from Asturias (Northern Spain) were genotyped using standard methods.

RESULTS

Both groups showed Hardy-Weinberg equilibrium for the analyzed genetic variability. A-1438G and T102C polymorphisms are in complete linkage disequilibrium in our population. There was an apparent difference in the distribution of genotypes for the A-1438G (or T102C) polymorphisms (p=0.018, not significant after a Bonferroni correction). The 5-HT2A -1438A (or 102T) allele was significantly more frequent in patients than controls (0.53 and 0.45, respectively; corrected p=0.028, OR=1.39 (95% CI=1.11-1.75)). Genotype and allele distributions for 5-HTT polymorphisms were similar in both groups. However, assessment of the combined influence of 5-HT2A A-1438G and 5-HTTLPR polymorphisms demonstrated a significant effect (chi(2) (3)=11.51, p=0.009), whereby the combination of -1438A and 5-HTTLPR S alleles was associated with schizophrenia.

CONCLUSIONS

Our findings support a possible synergistic effect of genetic factors influencing serotonergic neurotransmission on susceptibility to schizophrenia.

HTR2C and HTR1A gene variants in German and Italian suicide attempters and completers

The serotonin 2C (HTR2C) and 1A (HTR1A) receptors have been involved in suicide-related behaviors. We studied gene variants of both receptors in suicide attempters and completers. The sample was composed of 167 German suicide attempters (affective spectrum n = 107, schizophrenia spectrum n = 35, borderline personality disorder n = 25), 92 Caucasian individuals who committed suicide, 312 German healthy subjects, 152 Italian suicide attempters (major depression n = 68 and bipolar disorder n = 84), and 131 Italian healthy volunteers. HTR2C (SNP: rs547536, rs2192372, rs6318, rs2428707, rs4272555, rs1801412) and HTR1A (SNP: rs1423691, rs878567, and rs6295) variants were analyzed in the German sample. HTR2C rs6318 and HTR1A rs6295 were analyzed in the Italian sample. Haplotype analysis in relation to suicidal behaviors did not reveal any significant association. Single markers and haplotypes were not or only marginally associated with other related features, such as violence of suicide attempt, family history for suicide attempt or State-Trait Anger Expression Inventory (STAXI) and Questionnaire for Measuring Factors of Aggression (FAF) scores. In conclusion, our study does not support the notion that HTR2C and HTR1A gene variants are major contributors to suicide-, anger-, or aggression-related behaviors in our sample.

Candidate gene polymorphisms in the serotonergic pathway: influence on depression symptomatology in an elderly population

BACKGROUND

Depressed mood is a major concern in the elderly, with consequences for morbidity and mortality. Previous studies have demonstrated that genetic factors in depression and subsyndromal depressive symptoms are no less important in the elderly than during other life stages. Variations in genes included in the serotonin system have been suggested as risk factors for various psychiatric disorders but may also serve as candidates for normal variations in mood.

METHODS

This study included 684 elderly Danish twins to investigate the influence of 11 polymorphisms in 7 serotonin system genes on the mean level of depression symptomatology assessed over several years, reflecting individuals' underlying mood level.

RESULTS

A suggestive association of sequence variations in genes responsible for the synthesis (TPH), recognition (5-HTR2A), and degradation (MAOA) of serotonin with depression symptomatology was found, although the effect was generally restricted to men. We also found that a specific haplotype in VMAT2, the gene encoding the vesicular monoamine transporter, was significantly associated with depression symptoms in men (p= .007).

CONCLUSIONS

These results suggest that variations in genes encoding the components of serotonin metabolism may influence the basic mood level and that different genetic factors may apply in men and women.

Family Based Association Analyses between the Serotonin Transporter Gene Polymorphism (5-HTTLPR) and Neuroticism, Anxiety and Depression

We studied the association between the short/long promotor-based length polymorphism of the serotonin transporter gene (5-HTTLPR) and neuroticism, anxiety and depression. Subjects included twins, their siblings and parents from the Netherlands Twin Register (559 parents and 1,245 offspring). Subjects had participated between one and five times in a survey study measuring neuroticism, anxiety and depression. Offspring of these families were also approached to participate in a psychiatric interview diagnosing DSM-IV major depression. Within-family and total association between 5-HTTLPR and these traits were tested. Only three of the 36 tests showed a significant effect of 5-HTTLPR (P<0.05). These effects were in opposite directions, i.e. both negative and positive regression coefficients were found for the s allele. No additive effect of the s allele was found for DSM-IV depression. Our results strongly suggest that there is no straightforward association between 5-HTTLPR and neuroticism, anxiety and depression.

No allelic association or interaction of three known functional polymorphisms with bipolar disorder in a northern Swedish isolated population

Most genetic association studies in bipolar disorder have focussed on genes involved in major neurotransmitter systems or brain development. Functional polymorphisms in the serotonin transporter (5-HTTLPR), catechol-O-methyltransferase (Val158Met) and dopamine D3 receptor (Ser9Gly) genes have all been associated with bipolar disorder. We aimed at investigating whether these functional variants contribute to the genetic etiology of bipolar disorder in a northern Swedish isolated population. Moreover, we wanted to gain information about the synergistic contribution of these functional variants. Neither of these functional polymorphisms was associated with bipolar disorder in the northern Swedish patient-control sample nor did we find evidence of gene-gene interaction. Together, our data suggest that these functional variants are not involved in the etiology of bipolar disorder in the northern Swedish population nor did gene-gene interaction analysis support a central role of these variants in bipolar disorder.

A 40-basepair VNTR polymorphism in the dopamine transporter (DAT1) gene and the rapid response to antidepressant treatment

Finding predictors of the response to antidepressant therapy is a major goal of molecular psychiatry. The genes encoding the serotonin (SERT) and dopamine (DAT1) transporters are among the possible candidate genes modulating an individual's antidepressant response. In a naturalistic prospective cohort study with a total of 190 fully assessed patients, improvement of depression symptoms during the 3 weeks following initiation of antidepressant therapy was recorded using the 21-item Hamilton Depression Rating Scale (HDRS). The SLC6A3 3' UTR 40-bp variable number of tandem repeats (VNTR) and the SLC6A4 5' 44-bp insertion/deletion polymorphism were analyzed by polymerase chain reaction. There was a significantly smaller number of rapid responders among homozygous carriers of the DAT1 9-repeat allele (9/9) than among heterozygous (9/10) and homozygous (10/10) carriers of the 10-repeat allele (19 versus 37 versus 52%, respectively, P=0.0037). Median decline in HDRS score was 35, 40, and 52% in patients with the 9/9, 9/10, and 10/10 genotypes, respectively (P=0.013). The effect was found in all classes of medications (selective serotonin reuptake inhibitors (SSRIs), tricyclics, mirtazapine, venlafaxine) and statistically significant also within the subgroup of patients having received SSRIs. The serotonin promoter insertion/deletion genotype had no effect in the entire study group, but there was an insignificant trend of better response in the l/l and l/s carriers who received SSRIs or mirtazapine. In conclusion, the dopamine transporter VNTR polymorphism influenced rapid response to antidepressant therapy. Compared with homozygous carriers of the 10-repeat allele, carriers of the 9/10 genotype had an odds ratio (OR) calculated by logistic regression analysis of 1.6 (95% CI 0.8-3.2) and carriers of the 9/9 genotype had an OR of 6.0 (1.5-24.4) for no or poor response. Further studies are required to confirm this clinical association and to elucidate the underlying mechanisms.

Cumulative effect of COMT and 5-HTTLPR polymorphisms and their interaction with disease severity and comorbidities on the risk of psychosis in Alzheimer disease

OBJECTIVE

The objective of this study was to investigate the cumulative effect of the genes likely involved in Alzheimer disease (AD)-related psychosis and their interaction with disease stage and environmental factors.

METHODS

Two hundred thirty-four patients with AD underwent clinical and neuropsychologic examination, behavioral and psychiatric disturbances evaluation, and were subsequently divided into two subgroups according to the presence (AD-P) or the absence (AD-nP) of psychotic symptoms. Cathecol-O-methyltransferase (COMT), serotonin gene-linked promoter region (5-HTTLPR), and Apolipoprotein E (ApoE) genotypes were performed.

RESULTS

COMT*H (H/H or H/liter; odds ratio [OR]: 2.4; 95% confidence interval [CI]: 1.13-5.11) and 5-HTTLPR*S (S/S or S/liter, OR: 2.14; 95% CI: 1.13-4.07) were associated with AD-P. A gene dose effect was observed; in fact, carriers of both polymorphisms showed a fivefold risk for psychosis compared with patients bearing no polymorphisms. An interaction between these two genetic variations with disease stage and ischemic cardiomyopathy was found, the latter influencing AD-P risk only if "at-risk" genetic polymorphisms were present. The combined trend effect of COMT*H plus 5-HTTLPR*S and advance disease stage on AD-P risk was approximately 200% greater than that predicted by assuming additive effects, whereas the one obtained by COMT*H plus 5-HTTLPR*S and ischemic cardiomyopathy was 50% greater. ApoE genotype did not influence AD-P risk.

CONCLUSIONS

These findings claim for a synergic effect of COMT*H and 5-HTTLPR*S polymorphisms on the risk of psychosis in AD and for their interaction with disease stage and ischemic cardiomyopathy. This study suggests that considering both the genetic background and the environmental correlates might provide new insight for understanding psychosis mechanisms related to AD.

The Italian preadolescent mental health project (PrISMA): rationale and methods

The Italian preadolescent mental health project (PrISMA--Progetto Italiano Salute Mentale Adolescenti) is the first Italian study designed to estimate the prevalence of mental disorders in preadolescents (10-14 years old) living in urban areas, and to analyse the demographic and biological correlates of emotional and behavioural problems. This paper describes the rationale, methods and the analysis plan of the project. The design of the study used a two-stage sampling procedure, one screening stage of emotional and behavioural problems in a large sample of subjects attending public and private schools and a second stage of diagnostic assessment in a sample including all high scorers and a proportion of low scorers. In the screening stage, parents of preadolescents were asked to fill in the Child Behavior Checklist (CBCL), whereas in the second stage preadolescents and their parents were administered the Development and Well Being Assessment for the assessment of mental disorders together with the Strengths and Difficulties Questionnaire and two scales (C-GAS and HoNOSCA) designed to evaluate the functioning of the preadolescent in different areas. Genetic samples were collected during the screening stage, after parents gave their informed written consent. The findings of this study are expected to allow an adequate planning of interventions for the prevention and the treatment of mental disorders in preadolescence as well as efficient health services.

Interaction analysis between 5-HTTLPR and TNFA −238/−308 polymorphisms in schizophrenia

This study investigated the potential interaction between the polymorphisms of serotonin transporter gene (SLC6A4, a 44 base pair insertion/deletion in the promoter region, 5-HTTLPR) and tumor necrosis factor-alpha gene (TNFA; -238G/A and -308G/A polymorphisms) on the development of schizophrenia, as well as the interaction of the three polymorphisms in relation to symptomatology, family history, onset age and antipsychotic treatment response. Genomic DNA analyses with polymerase chain reaction (PCR) was used for the genotyping. One hundred and fifty-two (152) patients with schizophrenia and 152 normal controls participated in the study. Any associations between the individual polymorphism and schizophrenia were not found. However, marginal association between subjects with both TNFA -238 A allele (genotype AA plus AG) and 5-HTTLPR s allele (ss plus sl) and presence of family history was found (p = 0.023; p = 0.026). The subjects with TNFA -308 AG genotype showed higher change in PANSS total score (p = 0.028). No significant interaction effect between 5-HTTLPR and TNFA -238/-308 polymorphisms either on the development of schizophrenia or on antipsychotics treatment response and psychopathology was found, although a significant interaction effect for subjects carrying TNFA -238 AG and -308 AA genotypes on a positive family history was observed (p = 0.017). These results suggest that the interaction effects between 5-HTTLPR and TNFA -238/-308 polymorphisms gives no significant contribution to the susceptibility to schizophrenia, and is not associated with clinical variables, antipsychotic treatment response and psychopathological features, except for family history of disease, at least in the Korean population.

Meta-analysis reveals association between serotonin transporter gene STin2 VNTR polymorphism and schizophrenia

The serotonin transporter gene (SLC6A4) is a candidate gene for schizophrenia based on serotonin transporter's crucial role in serotonergic neurotransmission. However, association studies have produced conflicting results regarding the association between two common SLC6A4 gene polymorphisms, the promoter insertion/deletion (5-HTTLPR) and the intron 2 VNTR (STin2 VNTR) polymorphisms, and schizophrenia susceptibility. To further elucidate the putative association between the two SLC6A4 gene polymorphisms and schizophrenia susceptibility, we performed a meta-analysis based on all original published association studies between schizophrenia and the 5-HTTLPR and STin2 VNTR polymorphisms published before April 2004. Our analyses showed no statistically significant evidence for the association between the Short allele of the 5-HTTLPR polymorphism and schizophrenia (random-effects pooled odds ratio (OR)=0.99, 95% Confidence Interval (CI)=0.92-1.07, Z=-0.23, P=0.82) from 19 population-based association studies consisting of 2990 case and 3875 control subjects. However, highly significant evidence for association between the STin2.12 allele of the STin2 VNTR polymorphism (random-effects pooled OR=1.24, 95% CI=1.11-1.38, Z=3.82, P=0.00014) and schizophrenia was found from 12 population-based association studies consisting of 2177 cases and 2369 control subjects. Our meta-analysis suggests that the STin2.12 allele of the STin2 VNTR polymorphism is likely a risk factor for schizophrenia susceptibility. Our data imply that following completion of the International HapMap Project, a comprehensive evaluation of a set of markers that fully characterize the linkage disequilibrium relationships at the SLC6A4 gene should be tested in large well-characterized clinical samples in order to understand the role of this gene in schizophrenia susceptibility.

Serotonin Transporter Gene Polymorphism and Migraine in the Korean Population

OBJECTIVE

To evaluate the association between a serotonin (5-HT) transporter gene polymorphism and migraines in Koreans.

BACKGROUND

The 5-HT metabolism is believed to play an important part in the pathophysiology of migraines, and a polymorphism of the serotonin transporter (5-HTT) promoter region might influence 5-HTT expression and serotonin uptake.

METHODS

This study compared 52 patients with migraine and 170 healthy control subjects in order to determine the association between a polymorphism of the 5-HTT gene-linked polymorphic region (5-HTTLPR) and migraine. Using PCR techniques, the products of the 484-base pair (bp) fragments were denoted as being short alleles (s) and those of 528 bp as being long (l).

RESULTS

The genotype distribution of the healthy controls was s/s (56.5%), s/l (38.2%), and l/l (5.3%) and that of the patients with migraine was 65.4%, 30.8%, and 3.8%, respectively. No significant differences were noted in the genotype and allele frequencies of 5-HTTLPR between the patients with migraine and the control subjects.

CONCLUSIONS

A 5-HTTLPR polymorphism does not appear to be involved in the genetic predisposition to migraines.

No association of serotonin transporter gene (SLC6A4) with schizophrenia and bipolar disorder in Japanese patients: association analysis based on linkage disequilibrium

Serotonin transporter gene (SLC6A4) is one of the most promising candidate genes for psychiatric disorders such as schizophrenia (SCZ) and bipolar disorder (BP). Two functional polymorphisms, 5HTTLPR and 5HTTVNTR, have been a focus for genetic association analyses; however, no conclusive results have been obtained. We conducted, 1) a mutation search of SLC6A4, 2) LD mapping to select 'tagging' markers (10 SNPs and 5HTTVNTR, while 5HTTLPR was treated as an independent marker because of its allelic form), and 3) association analysis of these 'tagging' markers and independent markers (5HTTLPR and Asn605Lys) with SCZ and BP in Japanese patients. In this mutation search, a nonsynonymous SNP, Asn605Lys, was detected. No associations of 'tagging' markers and independent markers with such conditions were found. These results indicate that SLC6A4 might not play a major role in SCZ and BP in Japanese patients, a finding that agrees with both the common disease-common variant hypothesis and common disease-rare variant hypothesis.

No evidence for interaction between 5-HT2A receptor and serotonin transporter genes in schizophrenia

This study was to aim at investigating the potential interaction for the serotonin receptor gene (5-HTR) 2A and serotonin transporter gene (5-HTTLPR) polymorphisms in the development of schizophrenia, as well as the interaction of the two polymorphisms in relation with symptomatology, family history, age of onset and antipsychotic response. Genomic DNA analysis with polymerase chain reaction (PCR) was used for the genotyping. One hundred and eleven (111) patients with schizophrenia and 172 normal controls participated in the study. We did not find any association between the individual polymorphism and schizophrenia. The significant interaction effect between 5-HTTLPR and 5-HTR2A polymorphisms on the development of schizophrenia as well as on the antipsychotics response, family history, symptomatology and age at onset, was not found. However, subject with 5-HTR2A*TT genotype were found to have lower age of onset, compared to their counterparts (p=0.01). These results suggest that the interaction between 5-HTTLPR and 5-HTR2A polymorphisms may not contribute to susceptibility to schizophrenia as well as some clinical factors such as antipsychotic response, at least in the Korean population.

Meta-analysis of the association between two polymorphisms in the serotonin transporter gene and affective disorders

Family, twin, and adoption studies show that psychiatric diseases including bipolar disorder (BP) and unipolar disorder (UP) have a substantial genetic component. For these illnesses, both positive and negative associations have been reported for two polymorphisms located in the serotonin transporter gene (5-HTT) on chromosome 17: a 17-base-pair (bp) variable-number tandem-repeat (VNTR) in intron 2 and a 44-bp insertion/deletion in the promoter region. Thus, associations between these 5-HTT polymorphisms and affective disorders remain unclear. The present work investigates these potential associations in meta-analyzes that maximize the power to find associations between each disease and the two 5-HTT polymorphisms. We applied meta-analysis techniques to case-control studies of two 5-HTT polymorphisms and two affective disorders (BP and UP), resulting in four meta-analyzes. For each polymorphism, we assessed the evidence for allelic associations, heterogeneity among studies, the influence of individual studies, and the potential for publication bias. The short allele(s) of the 44-bp insertion/deletion polymorphism showed a significant association for BP (odds ratio (OR) = 1.13, P = 0.001) but not UP. For the 17-bp VNTR, an increase in the number of tandem repeats had no significant association with any of the disorders. The small but significant effects of the 44-bp insertion/deletion polymorphism for BP is consistent with being one of many genes that contributes to the multi-factorial nature of these psychiatric disorders.

The power of sample size and homogenous sampling: association between the 5-HTTLPR serotonin transporter polymorphism and major depressive disorder

BACKGROUND

Several lines of evidence indicate that abnormalities in the functioning of the central serotonergic system are involved in the pathogenesis of affective illness. A 44-base-pair insertion/deletion polymorphism in the 5' regulatory region of the serotonin transporter gene (5-HTTLPR), which influences expression of the serotonin transporter, has been the focus of intensive research since an initial report on an association between 5-HTTLPR and depression-related personality traits. Consistently replicated evidence for an involvement of this polymorphism in the etiology of mood disorders, particularly in major depressive disorder (MDD), remains scant.

METHODS

We assessed a potential association between 5-HTTLPR and MDD, using the largest reported sample to date (466 patients, 836 control subjects). Individuals were all of German descent. Patients were systematically recruited from consecutive inpatient admissions. Control subjects were drawn from random lists of the local Census Bureau and screened for psychiatric disorders.

RESULTS

The short allele of 5-HTTLPR was significantly more frequent in patients than in control subjects (45.5% vs. 39.9%; p = .006; odds ratio = 1.26).

CONCLUSIONS

These results support an involvement of 5-HTTLPR in the etiology of MDD. They also demonstrate that the detection of small genetic effects requires very large and homogenous samples.

Proposed multigenic Composite Inheritance in major depression

Various rationale have been considered in the familial inheritance pattern of major depression ranging from simple one-gene Mendelian inheritance to pseudo-additive gene action. We instead predict broad genetic expressivity patterns in the progeny of parents where at least one parent has recurrent major depression. In keeping with this idea, we feel that recurrent major depression could involve an expression imbalance of "normal" genes either exclusively or along with allelic variation(s). The patterns of pathology are theoretically conceptualized as qualitative and quantitative, meaning that expressivity of the genetic pattern in these children may range from minimal to complete even among siblings. Thus, prediction of the particular genetic pattern expressed by a particular child might prove difficult. The complex inheritance pattern that we propose is referred to as Composite Inheritance. Composite Inheritance considers that both the up- and down-regulation of luxury genes and housekeeping genes are involved in this dichotomous qualitative inheritance pattern and also the wide quantitative expressivity. The luxury genes include such genes as those coding for the neurotransmitter transporters and receptors. The housekeeping genes found to date include those that code for proteins involved in gene transcription, secondary signaling systems, fatty acid metabolism and transport, and intracellular calcium homeostasis. Other luxury and housekeeping genes no doubt remain to be discovered. Our current research utilizes an empirical approach involving advanced genomics and specialized pattern recognition mathematics in families having at least one parent with recurrent major depression. The goal of our research is to develop a pattern recognition system of genetic expressivity in major depression to which prevention and early intervention may be tailored.

Serotonergic polymorphisms and psychotic disorders in populations from North Spain

There is strong biological evidence relating alterations in the serotonergic system with mental disorders. These alterations may be originated at the DNA level by sequence mutations that alter the functioning of serotonin receptors and transporter. To test this hypothesis we investigated three genetic variants of the 5-HT2A receptor (-1438G/A, 102T/C and His452Tyr) and two variants of the serotonin transporter (a VNTR in the second intron and a 44 bp insertion/delition in the promoter region of the gene) in a clinical sample recruited in a human isolate and in surrounding areas in Northern Spain (N = 257) and in ethnically matched controls (N = 334). No clear association was found between 5-HT2A variants and psychosis. However, marginal associations were observed between the 5-HTT LPR and VNTR variants and psychosis (P < or = 0.05) indicating a minor contribution to psychosis of genetic alterations in this gene.