Genetic associations with clinical characteristics in bipolar affective disorder and recurrent unipolar depressive disorder

Next-generation precision medicine for suicidality prevention

Suicidality remains a clear and present danger in society in general, and for mental health patients in particular. Lack of widespread use of objective and/or quantitative information has hampered treatment and prevention efforts. Suicidality is a spectrum of severity from vague thoughts that life is not worth living, to ideation, plans, attempts, and completion. Blood biomarkers that track suicidality risk provide a window into the biology of suicidality, as well as could help with assessment and treatment. Previous studies by us were positive. Here we describe new studies we conducted transdiagnostically in psychiatric patients, starting with the whole genome, to expand the identification, prioritization, validation and testing of blood gene expression biomarkers for suicidality, using a multiple independent cohorts design. We found new as well as previously known biomarkers that were predictive of high suicidality states, and of future psychiatric hospitalizations related to them, using cross-sectional and longitudinal approaches. The overall top increased in expression biomarker was SLC6A4, the serotonin transporter. The top decreased biomarker was TINF2, a gene whose mutations result in very short telomeres. The top biological pathways were related to apoptosis. The top upstream regulator was prednisolone. Taken together, our data supports the possibility that biologically, suicidality is an extreme stress-driven form of active aging/death. Consistent with that, the top subtypes of suicidality identified by us just based on clinical measures had high stress and high anxiety. Top therapeutic matches overall were lithium, clozapine and ketamine, with lithium stronger in females and clozapine stronger in males. Drug repurposing bioinformatic analyses identified the potential of renin-angiotensin system modulators and of cyclooxygenase inhibitors. Additionally, we show how patient reports for doctors would look based on blood biomarkers testing, personalized by gender. We also integrated with the blood biomarker testing social determinants and psychological measures (CFI-S, suicidal ideation), showing synergy. Lastly, we compared that to machine learning approaches, to optimize predictive ability and identify key features. We propose that our findings and comprehensive approach can have transformative clinical utility.

Not Just a Mood Disorder─Is Depression a Neurodevelopmental, Cognitive Disorder? Focus on Prefronto-Thalamic Circuits

Depression is one of the most burdensome psychiatric disorders, affecting hundreds of millions of people worldwide. The disease is characterized not only by severe emotional and affective impairments, but also by disturbed vegetative and cognitive functions. Although many candidate mechanisms have been proposed to cause the disease, the pathophysiology of cognitive impairments in depression remains unclear. In this article, we aim to assess the link between cognitive alterations in depression and possible developmental changes in neuronal circuit wiring during critical periods of susceptibility. We review the existing literature and propose a role of serotonin signaling during development in shaping the functional states of prefrontal neuronal circuits and prefronto-thalamic loops. We discuss how early life insults affecting the serotonergic system could be important in the alterations of these local and long-range circuits, thus favoring the emergence of neurodevelopmental disorders, such as depression.

Association of two variable number of tandem repeats in the monoamine oxidase A gene promoter with suicide completion: The present study and meta-analysis

BACKGROUND

One potential cause of suicide is serotonergic dysfunction. Sex differences have been reported to modulate the effects of serotonergic polymorphisms. Monoamine oxidase A (MAOA) is an enzyme that degrades serotonin and is located on the X chromosome. A previous study indicated that the upstream (u) variable number of tandem repeat (VNTR) in the MAOA gene promoter may be associated with suicide. However, a meta-analysis showed that this polymorphism may not be related to suicide. According to a recent study, compared with the uVNTR, the distal (d)VNTR and the haplotypes of the two VNTRs modulate MAOA expression.

METHODS

We examined the two VNTRs in the MAOA gene promoter in 1007 subjects who committed suicide and 844 healthy controls. We analyzed the two VNTRs using fluorescence-based polymerase chain reaction assays. We conducted a meta-analysis for the two VNTRs to update it.

RESULTS

Our results demonstrated that neither the genotype-based associations nor allele/haplotype frequencies of the two VNTRs were significantly associated with suicide. In the meta-analysis, we did not indicate relationships between uVNTR and suicide nor did we identify articles analyzing dVNTR in suicide.

CONCLUSION

Overall, we did not find a relationship between the two VNTRs in the MAOA promoter and suicide completion; thus, warranting further studies are required.

Dysregulation of tryptophan metabolism and distortion of cell signaling after oral exposure to ethanol and Kynurenic acid

Kynurenic acid (KYNA), an unavoidable tryptophan metabolite during fermentation is naturally blended with alcohol in all alcoholic beverages. Thus, alcohol drinking inevitably results in co-intake of KYNA. Effects of alcohol or KYNA on human health have been widely studied. However, the combined effects of both remain unknown. Here we report that alcohol and KYNA have a synergistic impact of on global gene expression, especially the gene sets related to tryptophan metabolism and cell signaling. Adult mice were exposed to alcohol (ethanol) and/or KYNA daily for a week. Transcriptomes of the brain, kidney and liver were profiled via bulk RNA sequencing. Results indicate that while KYNA alone largely promotes, and alcohol alone mostly inhibits gene expression, alcohol and KYNA co-administration has a stronger inhibition of global gene expression. Tryptophan metabolism is severely skewed towards kynurenine pathway by decreasing tryptophan hydroxylase 2 and increasing tryptophan dioxygenase. Quantification of tryptophan metabolic enzymes corroborates the transcriptional changes of these enzymes. Furthermore, the co-administration greatly enhances the GnRH signaling pathway. This research provides critical data to better understand the effects of alcohol and KYNA in mix on human health.

The genetics of neurosystems in mental ill-health and suicidality: Beyond serotonin

Suicidal behavior is a major health problem worldwide. The risk of suicide-related behavior is supposed to be determined by a complex interplay of sociocultural factors, psychiatric history, personality traits, and genetic vulnerability. Family and twin studies point towards a partial heritability of suicidal behavior. First molecular genetic studies concentrated on genes of the serotonergic system based on the biochemical evidence that serotonergic neurotransmission is implicated in this behavior. Furthermore, genes of e.g. the dopaminergic and noradrenergic neurotransmitter systems have also been the subject of investigations in this context. The aim of this article is to review molecular genetic studies in suicidal behavior beyond the serotonergic system and to emphasize findings on new genes.

Proof-of-concept study of a multi-gene risk score in adolescent bipolar disorder

BACKGROUND

Few studies have examined multiple genetic variants concurrently for the purpose of classifying bipolar disorder (BD); the literature among youth is particularly sparse. We selected 35 genetic variants, previously implicated in BD or associated characteristics, from which to identify the most robustly predictive group of genes.

METHODS

215 Caucasian adolescents (114 BD and 101 healthy controls (HC), ages 13-20 years) were included. Psychiatric diagnoses were determined based on semi-structured diagnostic interviews. Genomic DNA was extracted from saliva for genotyping. Two models were used to calculate a multi-gene risk score (MGRS). Model 1 used forward and backward regressions, and model 2 used a PLINK generated method.

RESULTS

In model 1, GPX3 rs3792797 was significant in the forward regression, DRD4 exonIII was significant in the backward regression; IL1β rs16944 and DISC1 rs821577 were significant in both the forward and backward regressions. These variants are involved in dopamine neurotransmission; inflammation and oxidative stress; and neuronal development. Model 1 MGRS did not significantly discriminate between BD and HC. In model 2, ZNF804A rs1344706 was significantly associated with BD; however, this association did not predict diagnosis when entered into the weighted model.

LIMITATIONS

This study was limited by the number of genetic variants examined and the modest sample size.

CONCLUSIONS

Whereas regression approaches identified four genetic variants that significantly discriminated between BD and HC, those same variants no longer discriminated between BD and HC when computed as a MGRS. Future larger studies are needed evaluating intermediate phenotypes such as neuroimaging and blood-based biomarkers.

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.

The Regulation of Monoamine Oxidase A Gene Expression by Distinct Variable Number Tandem Repeats

The monoamine oxidase A (MAOA) uVNTR (upstream variable number tandem repeat) is one of the most often cited examples of a gene by environment interaction (GxE) in relation to behavioral traits. However, MAOA possesses a second VNTR, 500 bp upstream of the uVNTR, which is termed d- or distal VNTR. Furthermore, genomic analysis indicates that there are a minimum of two transcriptional start sites (TSSs) for MAOA, one of which encompasses the uVNTR within the 5' untranslated region of one of the isoforms. Through expression analysis in semi-haploid HAP1 cell lines genetically engineered in order to knockout (KO) either the uVNTR, dVNTR, or both VNTRs, we assessed the effect of the two MAOA VNTRs, either alone or in combination, on gene expression directed from the different TSSs. Complementing our functional analysis, we determined the haplotype variation of these VNTRs in the general population. The expression of the two MAOA isoforms was differentially modulated by the two VNTRs located in the promoter region. The most extensively studied uVNTR, previously considered a positive regulator of the MAOA gene, did not modulate the expression of what it is considered the canonical isoform, while we found that the dVNTR positively regulated this isoform in our model. In contrast, both the uVNTR and the dVNTR were found to act as negative regulators of the second less abundant MAOA isoform. The haplotype analysis for these two VNTRs demonstrated a bias against the presence of one of the potential variants. The uVNTR and dVNTR differentially affect expression of distinct MAOA isoforms, and thus, their combined profiling offers new insights into gene-regulation, GxE interaction, and ultimately MAOA-driven behavior.

Maoa and Maob polymorphisms and personality traits in suicide attempters and healthy controls: a preliminary study

Serotonergic neurotransmission dysfunctions have been well documented in patients with suicidal behaviour. We investigated monoamine oxidase A (MAOA: rs2064070, rs6323, rs909525) and B (MAOB: rs1799836, rs2311013, rs2205655) genetic modulation of personality traits (Temperament and Character Inventory, TCI) as endophenotype for suicidal behaviour. 108 suicide attempters and 286 healthy controls of German origin were screened. Among females, allelic analyses revealed associations between MAOA rs6323 A allele and higher Harm Avoidance in suicide attempters and MAOB rs2205655 A allele and higher Cooperativeness scores in healthy controls. Among males, MAOA rs909525 A allele was associated with higher Reward Dependence in suicide attempters. Multivariate analyses controlling for age and educational level mainly confirmed results. Case-control analyses in this subsample do not differ from our previously reported one. Despite of the small sample size, a possible involvement of these genes in the modulation of personality traits closely related to suicidal behaviour cannot be excluded.

Comparison of 16S and COX1 genes mitochondrial regions and their usefulness for genetic analysis of ticks (Acari: Ixodidae)

INTRODUCTION

In recent decades the analysis of mitochondrial genes has been used for population and phylogenetic studies of ticks allowing many advances in their systematics. Mitochondrial ribosomal 16S (16S) subunit is one of the most frequently used among those genes available for tick analysis, whereas cytochrome oxidase gene 1 (COX1) has recently been used and proposed as an alternative to the traditional 16S gene marker. 

OBJECTIVE

To evaluate the usefulness of 16S and COX1 in genetic studies of ticks by analyzing sequences of three species commonly found in the Caribbean region of Colombia. 

RESULTS

The analysis of both genes sequences allowed us to identify the three species with high levels of confidence and interspecific genetic divergence (19-22%), although only COX1 allowed us to detect intraspecific genetic variability (up to ~0.8%). A substitution saturation analysis indicated that the 16S gene was not saturated with transitions while the COX1 gene showed saturation distances starting at ~17%. 

CONCLUSION

Our results indicated that the 16S gene seems to have better features for interspecific phylogenetic analyses because of its high level of genetic divergence and low saturation pattern, while the COX1 gene appears to be more useful for intraspecific genetic variability studies. However, as our study was conducted at a local scale, future studies at different biogeographical scales would help to establish its usefulness in wider and more complex scenarios.

Biological aspects and candidate biomarkers for psychotic bipolar disorder: A systematic review

AIM

We carried out a systematic review of the available literature about potential biomarkers of psychotic bipolar disorder (BD-P), a specific subset presenting worse outcome and greater risk of relapse than non-psychotic bipolar disorder (BD-NP).

METHODS

We searched the main psychiatric databases (PubMed, ISI Web of Knowledge, PsychInfo). Only original articles with the main topic of BD-P compared to schizophrenia/BD-NP/healthy controls (HC) written in English from 1994 to 2015 were included.

RESULTS

BD-P patients presented higher kynurenic acid levels in the cerebrospinal fluid, elevated anti- S accharomyces cerevisiae antibodies levels, and lower serum levels of dehydroepiandrosterone sulfate and progesterone than BD-NP/HC. Event-related potentials abnormalities have been identified in BD-P with respect to BD-NP. BD-P patients also presented bigger ventricles but similar hippocampal volumes compared to BD-NP/HC. Although the results are contrasting, some cognitive deficits seemed to be related to the psychotic dimension of bipolar affective disorder, such as impairment in verbal/logical memory, working memory, verbal and semantic fluency and executive functioning. Finally, polymorphisms of genes, such as NRG1, 5HTTLPR (s), COMT, DAOA and some chromosome regions (16p12 and 13q), were positively associated with BD-P.

CONCLUSION

Data about the identification of specific biomarkers for BD-P are promising, but most of them have not yet been replicated. They could lead the clinicians to an early diagnosis and proper treatment, thus ameliorating outcome of BD-P and reducing the biological changes associated with a long duration of illness. Further studies with bigger samples are needed to detect more specific biological markers of the psychotic dimension of bipolar affective disorder.

Association involving serotonin transporter gene linked polymorphic region and bipolar disorder type 1 in Iranian population

INTRODUCTION

Serotonin transporter gene linked polymorphic region, also called 5HTTLPR, is a candidate in the genetics of bipolar disorder; however, the results of previous association studies are inconsistent. Several explanations have been proposed for that inconsistency; among them are the existing differences both in the genetic basis of bipolar disorder subtypes and the genetic backgrounds of the studied populations. We aimed to investigate the association of 5HTTLPR with bipolar disorder type I (BP-1) in Iranian population.

METHODS

In this case-control study, 146 patients with BP-1 and 165 controls were recruited. The patients were selected through the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, 4th edition. It was required that the patients do not have any present history of general medical conditions, substance abuse, and concurrent major psychiatric disorders. The polymorphism was evaluated by blood sampling and subsequent DNA extraction, polymerase chain reaction, and agarose gel electrophoresis. Chi-square test was used for analyzing allelic and genotype frequencies and two-tailed P values were obtained.

RESULTS

The S allele was significantly more frequent in the BP-1 patients compared with the controls (P = 0.02, S allele odds ratio = 1.5, confidence interval 95% = 1.06-2.11).

DISCUSSION

Our statistically significant results suggest that the role of 5HTTLPR in the pathogenesis of BP-1 needs to be clarified by further scrutiny in Iranian population and other populations of Near East.

The genetics of early-onset bipolar disorder: A systematic review

BACKGROUND

Early-onset bipolar disorder has been associated with a significantly worse prognosis than late-onset BD and has been hypothesized to be a genetically homogenous subset of BD. A sizeable number of studies have investigated early-onset BD through linkage-analyses, candidate-gene association studies, genome-wide association studies (GWAS), and analyses of copy number variants (CNVs), but this literature has not yet been reviewed.

METHODS

A systematic review was conducted using the PubMed database on articles published online before January 15, 2015 and after 1990. Separate searches were made for linkage studies, candidate gene-association studies, GWAS, and studies on CNVs.

RESULTS

Seventy-three studies were included in our review. There is a lack of robust positive findings on the genetics of early-onset BD in any major molecular genetics method.

LIMITATIONS

Early-onset populations were quite small in some studies. Variance in study methods hindered efforts to interpret results or conduct meta-analysis.

CONCLUSIONS

The field is still at an early phase for research on early-onset BD. The largely null findings mirror the results of most genetics research on BD. Although most studies were underpowered, the null findings could mean that early-onset BD may not be as genetically homogenous as has been hypothesized or even that early-onset BD does not differ genetically from adult-onset BD. Nevertheless, clinically the probabilistic developmental risk trajectories associated with early-onset that may not be primarily genetically determined continued to warrant scrutiny. Future research should dramatically expand sample sizes, use atheoretical research methods like GWAS, and standardize methods.

Investigating the genetic variation underlying episodicity in major depressive disorder: suggestive evidence for a bipolar contribution

BACKGROUND

Highly recurrent major depressive disorder (MDD) has reportedly increased risk of shifting to bipolar disorder; high recurrence frequency has, therefore, featured as evidence of 'soft bipolarity'. We aimed to investigate the genetic underpinnings of total depressive episode count in recurrent MDD.

METHODS

Our primary sample included 1966 MDD cases with negative family history of bipolar disorder from the RADIANT studies. Total episode count was adjusted for gender, age, MDD duration, study and center before being tested for association with genotype in two separate genome-wide analyses (GWAS), in the full set and in a subset of 1364 cases with positive family history of MDD (FH+). We also calculated polygenic scores from the Psychiatric Genomics Consortium MDD and bipolar disorder studies.

RESULTS

Episodicity (especially intermediate episode counts) was an independent index of MDD familial aggregation, replicating previous reports. The GWAS produced no genome-wide significant findings. The strongest signals were detected in the full set at MAGI1 (p=5.1×10(-7)), previously associated with bipolar disorder, and in the FH+ subset at STIM1 (p=3.9×10(-6) after imputation), a calcium channel signaling gene. However, these findings failed to replicate in an independent Munich cohort. In the full set polygenic profile analyses, MDD polygenes predicted episodicity better than bipolar polygenes; however, in the FH+ subset, both polygenic scores performed similarly.

LIMITATIONS

Episode count was self-reported and, therefore, subject to recall bias.

CONCLUSIONS

Our findings lend preliminary support to the hypothesis that highly recurrent MDD with FH+ is part of a 'soft bipolar spectrum' but await replication in larger cohorts.

Genes in the serotonin pathway are associated with bipolar affective disorder in a Han Chinese population

Serotonin plays an important role in mood regulation, but the involvement of serotonin pathway genes in the development of bipolar I disorder (BP-I), a mood disorder, is not clear. We selected 21 single-nucleotide polymorphisms (SNPs) within the HTR2A gene, 8 within the SLC6A4 gene and 23 within the TPH2 gene for genotyping using the GoldenGate genotyping assay. A total of 375 patients with BP-I and 475 normal controls were recruited. Two out of 21 SNPs (rs1475196 and rs9567747) in the HTR2A gene and 1/23 SNPs (rs17110566) in the TPH2 gene were significantly associated with BP-I, both genotype-wise and allele-wise. Furthermore, a specific haplotype in the HTR2A gene showed a significant association with BP-I. Our results indicate that the HTR2A and TPH2 genes in the serotonin pathway play important roles in susceptibility to BP-I.

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.

The 5HTT and MAO-A polymorphisms associate with depressive mood and climacteric symptoms in postmenopausal women

OBJECTIVE

The aim of this study was to assess the influence of the 44-bp polymorphism in the 5HTTLPR (SLC 6A4) (serotonin-transporter-linked polymorphic region, solute carrier family 6 member 4) promoter region and the 30-bpVNTR (variable number of tandem repeats) polymorphism in the MAO-A (monoamine oxidase A) promoter region on the prevalence of depressive mood and the severity of climacteric symptoms in postmenopausal women.

MATERIAL AND METHODS

The study involved 630 women from northern Poland who had their last menstrual period at least one year before the study. The women did not abuse alcohol or cigarettes, had not been diagnosed as having endocrinological, cancerous or mental diseases, and had not received psychiatric treatment by the time. This survey-based study was performed using the following research instruments: the Beck Depression Inventory (BDI), to evaluate depressive symptoms, and the Blatt-Kupperman Menopausal Index, to measure the severity of climacteric symptoms.

RESULTS

The average age of the women was 57.5 ± 6.4 years. Depressive symptoms of different severity according to the BDI were diagnosed in 29.2% of the women (minor-18.6%, moderate-7.1%, severe-3.5%) and according to the Blatt-Kupperman Menopausal Index were diagnosed in 42% of the women (minor-24.1%, moderate-9.2%, severe-8.7%). Allele 'l' was significantly more common in the women without climacteric symptoms than those with minor, moderate or severe climacteric complaints (p ≤ 0.05). There was a significant correlation between the severity of climacteric and depressive symptoms (p ≤ 0.05). The women who had severe climacteric symptoms also had more severe depressive symptoms.

CONCLUSIONS

1. The 5HTTLPR gene polymorphism contributes to climacteric symptoms in postmenopausal women. 2. The Blatt-Kupperman Menopausal Index is an instrument which can not only be used for the measurement of the severity of climacteric symptoms but also the early detection of perimenopausal women at the risk of developing depressive symptoms.

The role of the serotonergic system at the interface of aggression and suicide

Alterations in serotonin (5-HT) neurochemistry have been implicated in the aetiology of all major neuropsychiatric disorders, ranging from schizophrenia to mood and anxiety-spectrum disorders. This review will focus on the multifaceted implications of 5-HT-ergic dysfunctions in the pathophysiology of aggressive and suicidal behaviours. After a brief overview of the anatomical distribution of the 5-HT-ergic system in the key brain areas that govern aggression and suicidal behaviours, the implication of 5-HT markers (5-HT receptors, transporter as well as synthetic and metabolic enzymes) in these conditions is discussed. In this regard, particular emphasis is placed on the integration of pharmacological and genetic evidence from animal studies with the findings of human experimental and genetic association studies. Traditional views postulated an inverse relationship between 5-HT and aggression and suicidal behaviours; however, ample evidence has shown that this perspective may be overly simplistic, and that such pathological manifestations may reflect alterations in 5-HT homoeostasis due to the interaction of genetic, environmental and gender-related factors, particularly during early critical developmental stages. The development of animal models that may capture the complexity of such interactions promises to afford a powerful tool to elucidate the pathophysiology of impulsive aggression and suicidability, and identify new effective therapies for these conditions.

Pathophysiology of depression and mechanisms of treatment

Major depression is a serious disorder of enormous sociological and clinical relevance. The discovery of antidepressant drugs in the 1950s led to the first biochemical hypothesis of depression, which suggested that an impairment in central monoaminergic function was the major lesion underlying the disorder. Basic research in all fields of neuroscience (including genetics) and the discovery of new antidepressant drugs have revolutionized our understanding of the mechanisms underlying depression and drug action. There is no doubt that the monoaminergic system is one of the cornerstones of these mechanisms, but multiple interactions with other brain systems and the regulation of central nervous system function must also be taken into account In spite of all the progress achieved so far, we must be aware that many open questions remain to be resolved in the future.

Monoamine oxidase A gene polymorphism and suicide: an association study and meta-analysis

BACKGROUND

Abnormalities in brain monoamine transmission have been implicated in the pathogenesis of suicidal behavior. Studies examining the association between monoamine oxidase A (MAOA)-uVNTR polymorphism and suicide revealed inconsistent findings. This study aims to evaluate the possible association between the MAOA-uVNTR polymorphism and suicidal behaviors by examining our own subjects and conducting a meta-analytic review.

METHODS

373 unrelated psychiatric patients (including 160 suicide attempters and 213 non-suicide attempters) were genotyped for the MAOA-uVNTR polymorphism. A meta-analysis was then performed by pooling data from seven case-control association studies by random effects model.

RESULTS

Our results indicate that there is no association between the MAOA-uVNTR polymorphism and suicide attempts in both genders. It also reveals that there is no association with violent suicide attempts. In the meta-analysis, there is no association between the polymorphism and suicidal behaviors. Also, there is no difference in the allelic distribution between psychiatric patients with and without suicidal behaviors. Limitations Our study was constrained by the insufficient information about environmental risk factors of suicide.

CONCLUSIONS

Our study is the first one to use meta-analysis in exploring the role of the MAOA-uVNTR polymorphism in suicidal behavior in psychiatric patients. No significant association was found in our study, suggesting MAOA-uVNTR polymorphism is unlikely to contribute significantly to suicide behavior. Further studies investigating the gene-environment interaction or focusing on the genetic risk factors of endophenotypes of suicidal behaviors are warranted.

P2RX7 gene is associated consistently with mood disorders and predicts clinical outcome in three clinical cohorts

We investigated the effect of nine candidate genes on risk for mood disorders, hypothesizing that predisposing gene variants not only elevate the risk for mood disorders but also result in clinically significant differences in the clinical course of mood disorders. We genotyped 178 DSM-IV bipolar I and II and 272 major depressive disorder patients from three independent clinical cohorts carefully diagnosed with semistructured interviews and prospectively followed up with life charts for a median of 60 (range 6-83) months. Healthy control subjects (n = 1322) were obtained from the population-based national Health 2000 Study. We analyzed 62 genotyped variants within the selected genes (BDNF, NTRK2, SLC6A4, TPH2, P2RX7, DAOA, COMT, DISC1, and MAOA) against the presence of mood disorder, and in post-hoc analyses, specifically against bipolar disorder or major depressive disorder. Estimates for time ill were based on life charts. The P2RX7 gene variants rs208294 and rs2230912 significantly elevated the risk for a familial mood disorder (OR = 1.35, P = 0.0013, permuted P = 0.06, and OR = 1.44, P = 0.0031, permuted P = 0.17, respectively). The results were consistent in all three cohorts. The same risk alleles predicted more time ill in all cohorts (OR 1.3, 95% CI 1.1-1.6, P = 0.0069 and OR 1.7, 95% CI 1.3-2.3, P = 0.0002 with rs208294 and rs2230912, respectively), so that homozygous carriers spent 12 and 24% more time ill. P2RX7 and its risk alleles predisposed to mood disorders consistently in three independent clinical cohorts. The same risk alleles resulted in clinically significant differences in outcome of patients with major depressive and bipolar disorder.

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.

Influence of the serotonin transporter gene polymorphism, cannabis and childhood sexual abuse on phenotype of bipolar disorder: a preliminary study

OBJECTIVE

The gene coding for the 5-HT transporter (5-HTT) is considered as a candidate gene for bipolar disorder, either as a "vulnerability" or as a "modifying the phenotype" gene. Psychotic symptoms occur at least once in one bipolar patient out of two, the relevant risk factors being insufficiently understood. The gene × environment interaction approach offers the opportunity to disentangle the latter, including childhood sexual abuse and cannabis abuse.

METHODS

We investigated the 5-HTTLPR of the 5-HTT gene (G) and the presence of childhood sexual abuse and cannabis comorbidity (E) in 137 bipolar patients with (versus without) lifetime psychotic symptoms.

RESULTS

The short allele and cannabis abuse were significantly more frequent among patients with psychotic symptoms than in those without (p=0.01 and p=0.004, respectively), while childhood sexual abuse was not. Complex interactions were found between presence of the short allele, cannabis abuse or dependence and childhood sexual abuse.

CONCLUSIONS

The short allele of the 5-HTTLPR polymorphism of the 5-HTT gene was a risk factor for psychotic symptoms in bipolar disorder in the present sample, directly but also indirectly, through the presence of cannabis abuse or dependence, as an exacerbating factor heightening psychotic symptoms.

The tryptophan hydroxylase 1 (TPH1) gene, schizophrenia susceptibility, and suicidal behavior: a multi-centre case-control study and meta-analysis

Serotonin (5-hydroxytryptamin; 5-HT) alternations has since long been suspected in the pathophysiology of schizophrenia. Tryptophan hydroxylase (tryptophan 5-monooxygenase; TPH) is the rate-limiting enzyme in the biosynthesis of 5-HT, and sequence variation in intron 6 of the TPH1 gene has been associated with schizophrenia. The minor allele (A) of this polymorphism (A218C) is also more frequent in patients who have attempted suicide and individuals who died by suicide, than in healthy control individuals. In an attempt to replicate previous findings, five single nucleotide polymorphisms (SNPs) were genotyped in 837 Scandinavian schizophrenia patients and 1,473 controls. Three SNPs spanning intron 6 and 7, including the A218C and A779C polymorphisms, were associated with schizophrenia susceptibility (P = 0.019). However there were no differences in allele frequencies of these loci between affected individuals having attempted suicide at least once and patients with no history of suicide attempts (P = 0.84). A systematic literature review and meta-analysis support the A218C polymorphism as a susceptibility locus for schizophrenia (odds ratio 1.17, 95% confidence interval 1.07-1.29). Association studies on suicide attempts are however conflicting (heterogeneity index I(2) = 0.54) and do not support the A218C/A779C polymorphisms being a susceptibility locus for suicidal behavior among individuals diagnosed with a psychiatric disorder (OR = 0.96 [0.80-1.16]). We conclude that the TPH1 A218/A779 locus increases the susceptibility of schizophrenia in Caucasian and Asian populations. In addition, the data at hand suggest that the locus contributes to the liability of psychiatric disorders characterized by elevated suicidal rates, rather than affecting suicidal behavior of individuals suffering from a psychiatric disorder.

Association of MAOA gene functional promoter polymorphism with CSF dopamine turnover and atypical depression

OBJECTIVE

Monoamine oxidase-A (MAO-A) is a key mitochondrial enzyme that metabolizes biogenic amine neurotransmitters such as dopamine and serotonin. Individuals with atypical depression (AD) are particularly responsive to treatment with MAO inhibitors (MAOIs). Biomarker tests are essential for prompt diagnosis of AD, and to identify those with an altered brain neurotransmitter metabolism who may selectively respond to MAOI therapy.

METHODS

In a sample of 118 Scandinavian patients with treatment-resistant depression who are naive to MAOI therapy, we investigated the associations between a common MAOA functional promoter polymorphism (MAOA-uVNTR), cerebrospinal fluid (CSF) neurotransmitter metabolites, and AD susceptibility. The metabolites for dopamine (homovanillic acid, HVA), serotonin (5-hydroxyindoleacetic acid) and noradrenaline (3-methoxy-4-hydroxyphenylglycol) were measured in the CSF.

RESULTS

AD was associated with the female sex and a higher HVA in CSF (P=0.008). The carriers of the MAOA-uVNTR short allele were significantly overrepresented among women with AD (P=0.005; odds ratio=4.76; 95% confidence interval=1.5-13.1; statistical power=80.0%). Moreover, the MAOA-uVNTR genotype significantly influenced the HVA concentration (P=0.01) and showed a strong trend in relation to 5-hydroxyindoleacetic acid concentration (P=0.057) in women. The mediational statistical analyses showed the CSF-HVA concentration as a key driver of the relationship between MAOA-uVNTR genotype and AD.

CONCLUSION

The association of the MAOA-uVNTR with both susceptibility to AD and dopamine metabolite (HVA) concentration lends further biological plausibility for high MAO-A enzyme activity as a mechanistic factor for genetic predisposition to AD through altered dopamine turnover. Our observations provide new evidence on the in-vivo functional significance of the MAOA-uVNTR short allele as a high activity variant.

Premorbid adjustment: a phenotype highlighting a distinction rather than an overlap between schizophrenia and bipolar disorder

BACKGROUND

Premorbid adjustment (PMA) in schizophrenia (SZ) has been widely studied and shown to be worse in individuals who develop SZ as compared to controls. It has been proposed as a predictor of clinical presentation and outcome, and may delineate a specific SZ phenotype for genetic and other biological studies. Research into PMA in BD has been scarce and inconclusive.

AIMS

The authors compared PMA in individuals suffering from BD with that of healthy controls and investigated whether levels of PMA in BD patients correlate with specific phenotypic features.

METHODS

The authors investigated 344 BD patients and 137 population-based controls. Retrospective PMA assessment was performed using the Premorbid Adjustment Scale (PAS). An overall score as well as sub-scores for age ranges and functional domains were obtained.

RESULTS

Patients had a better overall PAS score than controls and outperformed controls during early and late adolescence. They scored significantly better than controls in the functional domains "sociability and withdrawal" and "adaptation to school". No differences were observed for the other subscales and there were no differences between groups during childhood. No association was observed between PMA and any of the phenotype characteristics investigated.

CONCLUSIONS

In the largest study to date on PMA in BD, PMA was shown to be better in bipolar patients than in healthy controls. PMA in BD is not a simple proxy for commonly studied phenotypic markers of severity. PMA emerges as a phenotype in its own right, and highlights an aspect of disparity rather than overlap between SZ and BD.

High-activity variants of the uMAOA polymorphism increase the risk for depression in a large primary care sample

Studies on the association between the functional uMAOA polymorphism and depression have yielded non-conclusive results up till now. One thousand two hundred twenty eight consecutive Spanish primary care attendees, participating in the PREDICT study, agreed to take part in this genetic PREDICT-Gene study. We explored the association between depression and either high-activity uMAOA alleles or genotypes. Depression was diagnosed using the Composite International Diagnostic Interview (CIDI) to establish three different depressive outcomes (ICD-10 Depressive Episode (DE), ICD-10 Severe Depressive Episode (SDE) and DSM-IV Major Depression (MD)). uMAOA genetic variation was determined by PCR amplification and subsequent electrophoresis. Crude and adjusted (gender and/or age) odds ratios, with 95% confidence intervals, were calculated for the associations between allele or genotype frequencies and all three depressive outcomes. We found associations between all three depressive phenotypes and either high-activity alleles or high-activity genotypes in both sexes. The associations were statistically significant for females but not for males. Testing the same associations on the entire sample (males and females) also yielded significant associations between depression and either high-activity alleles or high-activity genotype distribution that were independent of age and/or gender (ICD-10 DE: OR = 1.98; 95% CI: 1.42-1.77; P = 0.00002; ICD-10-SDE: OR = 2.05; 95% CI: 1.38-3.05; P = 0.0002; DSM-IV MD: OR = 1.91; 95% CI: (1.26-2.91); P = 0.0014). Our results provide fairly consistent evidence that high-activity variants of the MAOA promoter polymorphism confer a modestly higher risk for depression.

Role of variation in the serotonin transporter protein gene (SLC6A4) in trait disturbances in the ventral anterior cingulate in bipolar disorder

Bipolar disorder (BD) is associated with abnormalities of the ventral anterior cingulate cortex (vACC) and its connection sites, including the amygdala, which are key components of a corticolimbic neural system that subserves emotional regulation. Decreased functional connectivity from the vACC to the amygdala in healthy individuals is associated with the short 's' allele--as opposed to the long 'l' allele--of a well-known serotonin transporter promoter polymorphism (5-HTTLPR, locus SLC6A4), as are features of BD. This study tests the hypothesis that the s allele influences dysfunction in the vACC-amygdala neural system in BD. A total of 30 euthymic individuals with BD (20 s carriers, 10 ll) and 48 healthy comparison (HC) participants (34 s, 14 ll) participated in an event-related functional magnetic resonance imaging scan while processing fearful, happy, or neutral faces. During fear and happy face processing, vACC activation was significantly lower in the BD compared to the HC group, and in s carriers compared to ll individuals within both the HC and BD groups, such that BD s carriers exhibited the greatest magnitude of vACC dysfunction. No significant differences were detected in amygdala activation. The findings suggest that the 5-HTTLPR s allele may contribute to a trait-related, genetically derived, neurobiological subgroup within BD characterized by prominent vACC dysfunction. Future treatment may be optimized for this BD subgroup by targeting the serotonergic system and the vACC.

An association study of monoamine oxidase A (MAOA) gene polymorphism in methamphetamine psychosis

Methamphetamine continues to be the most widely abused drug in Japan. Chronic methamphetamine users show psychiatric signs, including methamphetamine psychosis. Monoamine oxidase A (MAOA) is one of the major enzymes responsible for the degradation of neurotransmitters. Abnormalities in MAO levels have been related to a wide range of psychiatric disorders. We examined whether or not the MAOA-u variable-number tandem repeat (VNTR) has a functional polymorphism in methamphetamine psychosis and whether or not such a polymorphism is related to the prolongation of psychosis. As expected, there was a significant difference in the MAOA-u VNTR between males with persistent versus transient methamphetamine psychosis (p=0.018, odds ratio (OR)=2.76, 95% CI: 1.18-6.46). Our results suggest that the high-activity allele class of MAOA-u VNTR in males may be involved in susceptibility to a persistent course of methamphetamine psychosis. We found no differences among females. The sample size of females with methamphetamine psychosis was too small to have significant analysis.

Hypomanic, cyclothymic and hostile personality traits in bipolar spectrum illness: a family-based study

OBJECTIVES

To examine hypomanic, cyclothymic and hostile personality traits in a large, euthymic, family-based group of individuals with bipolar disorder (BPD) and their affectively ill and healthy relatives. To test whether these traits follow a distribution with the most "pathological" scores in the bipolar disorder I (BPD I) group and the least "pathological" scores in the unaffected relatives.

METHODS

Two-hundred and ninety-six individuals from 47 bipolar disorder families were administered a battery of personality questionnaires (Temperament Evaluation of Memphis, Pisa, Paris, and San Diego; Temperament and Character Inventory; Affective Neuroscience Personality Scale; Hypomanic Personality Scale; Borderline Traits Questionnaire) as well as a self-rating depression (Beck Depression Inventory) and mania (Altman Self-Rating Mania) scale. Out of the 296 participants, 57 were diagnosed with BPD I, 24 with bipolar disorder II (BPD II), 58 with recurrent major depression (MDE-R), 45 had one previous depressive episode (MDE-S), and 86 were unaffected. Twenty six individuals had another DSM-IV diagnosis.

RESULTS

The BPD I group displayed elevated hypomanic, cyclothymic and hostile traits. These traits were also characteristic of the BPD II group but were less salient in the MDE-R group. The MDE-S group did not differ significantly from unaffected relatives. Hypomanic personality characteristics were clearly elevated in both BPD groups and differentiated BPD from major depressive disorder (MDD) individuals.

CONCLUSIONS

Our results provide preliminary support for the hypothesis that temperament is a genetically quantitative trait.

Association of MAO-A variant with complicated grief in major depression

BACKGROUND/AIMS

It has been suggested that monoamine oxidase A (MAO-A) activity is involved in the pathogenesis of major depression. Bereavement-related complicated grief significantly increases the risk of major depression and has been shown to be influenced by serotonergic tonus, possibly conferred by MAO-A activity. Complicated grief--whose inclusion in DSM-V as a separate mental disorder is under discussion--has been shown to be a distinct syndrome with symptoms not seen in depression. Therefore, in the present study, genetic variation in the MAO-A gene was investigated for its influence on complicated grief in major depression.

METHODS

Sixty-six unrelated Caucasian patients (41 female, 25 male) with major depression and a history of bereavement were evaluated for complicated grief using the Inventory of Complicated Grief (ICG), the posttraumatic stress reaction after the loss by means of the Impact of Event Scale (IES-R) and further psychopathological measures. Patients were additionally genotyped for the functional variable number tandem repeat (VNTR) in the promoter region of the MAO-A gene.

RESULTS

The more active longer allele of the MAO-A VNTR was significantly associated with complicated grief in the female subgroup of patients (chi(2) = 9.471, p = 0.002, OR = 9.208, 95% CI 2.129-38.899, Bonferroni-corrected p = 0.012), whereas there was no such effect in male patients. Higher posttraumatic stress reaction was only nominally associated with the more active longer allele of the MAO-A VNTR in the female subgroup of patients (genotypes: chi(2) = 5.939, p = 0.015, OR = 5.333, 95% CI 1.366-20.557, Bonferroni-corrected p = 0.087). No significant associations of MAO-A VNTR with the severity of depressive symptoms (Beck Depression Inventory), anxiety symptoms (Spielberger State-Trait Anxiety Inventory), general mental health (Brief Symptom Inventory), or perceived social support (F-SozU) were found (all p > 0.10).

CONCLUSION

The present pilot study for the first time suggests a gender-specific contribution of the more active MAO-A VNTR variant to an increased vulnerability for complicated grief as a potential intermediate phenotype of major depression.

Stress, genes and the biology of suicidal behavior

Suicidal behavior is partly heritable. Studies seeking the responsible candidate genes have examined genes involved in neurotransmitter systems shown to have altered function in suicide and attempted suicide. These neurotransmitter systems include the serotonergic, noradrenergic, and dopaminergic systems and the hypothalamic-pituitary-adrenal axis. With some exceptions, most notably the serotonin transporter gene promoter polymorphism (HTTLPR), replication of candidate gene association studies findings has been difficult. This article reviews current knowledge of specific gene effects and gene-environment interactions that influence risk for suicidal behavior. Effects of childhood stress on development and how it influences adult responses to current stress are shown to be relevant for mood disorders, aggressive/impulsive traits, and suicidal behavior.

The genetics of suicide: a critical review of molecular studies

Genetic epidemiology research has shown that genes contribute to suicide risk. Unfortunately, the first 30 years of candidate-based association studies have provided little information about the specific genetic contributors. This article reviews genetic association studies of suicidal phenotypes published to date. Possible theoretical, methodological, and operational challenges accounting for the modest success of association studies in the field are also discussed. The authors conclude that future research may benefit from using a more systematic and comprehensive selection of candidate genes and variants, examining gene-environment and gene-gene interactions, and investigating higher-order moderators.

The genetics of psychotic bipolar disorder

Psychotic features, defined as delusions or hallucinations, commonly occur in bipolar disorder (BP) and may be indicative of a more homogeneous form of the illness, with possible etiologic ties to schizophrenia. Several studies have shown that psychotic features aggregate in bipolar families, and increased interest in the molecular genetics of psychotic BP is emerging. Although preliminary, linkage studies of psychotic BP show replicated evidence for suggestive genome-wide linkage to chromosomes 8p and 13q, which have been implicated in prior linkage studies of schizophrenia and BP. Association studies of psychotic BP and subtypes such as mood-incongruent psychotic BP have uncovered modest positive results for several candidate schizophrenia susceptibility genes, including dysbindin, DAOA/G30, Disrupted-in-Schizophrenia-1, and neuregulin 1. These tentative results are consistent with the hypothesis that the subphenotype of psychotic BP may represent a clinical manifestation of "overlap" genes between schizophrenia and mood disorder syndromes.

Gene-based SNP mapping of a psychotic bipolar affective disorder linkage region on 22q12.3: association with HMG2L1 and TOM1

Genetic linkage studies in both bipolar affective disorder (BPAD) and schizophrenia have implicated overlapping regions of chromosome 22q. We previously reported that BPAD pedigrees containing multiple members with psychotic symptoms showed suggestive linkage to chromosome 22q12.3. Now we have tested 189 single nucleotide polymorphisms (SNPs) spanning a 3 Mb region around the linkage peak for association with BPAD in 305 families, unrelated cases, and controls. SNPs were selected in or near genes, resulting in coverage at a density of 1 SNP per 6.7 kb across the 22 annotated genes in the region. The strongest signal emerged from family-based association analysis of an 11-SNP, 54 kb haplotype straddling the gene HMG2L1 and part of TOM1. A 3-marker haplotype of SNPs within TOM1 was associated with BPAD (allele-wise P = 0.0011) and with psychotic BPAD (allele-wise P = 0.00049). As hypothesized, the mean odds ratio for the risk alleles across the region was 1.39 in the psychotic but only 0.96 in the non-psychotic subset. Genotype-wise analyses yielded similar results, but the psychotic/non-psychotic distinction was more pronounced with mean odds ratios of 1.91 versus 0.8. Permutation of genotype-wise results for rs2413338 in HMG2L1 showed an empirical P = 0.037 for the difference between subsets. HMG2L1 is a negative regulator of Wnt signaling, a pathway of interest in psychotic BPAD as it is activated by both mood stabilizer and anti-psychotic medications. Further work is needed to confirm these results and uncover the functional variation underlying the association signal.

Candidate genes for panic disorder: insight from human and mouse genetic studies

Panic disorder is a major cause of medical attention with substantial social and health service cost. Based on pharmacological studies, research on its etiopathogenesis has been focused on the possible dysfunction of specific neurotransmitter systems. However, recent work has related the genes involved in development, synaptic plasticity and synaptic remodeling to anxiety disorders. This implies that learning processes and changes in perception, interpretation and behavioral responses to environmental stimuli are essential for development of complex anxiety responses secondary to the building of specific brain neural circuits and to adult plasticity. The focus of this review is on progress achieved in identifying genes that confer increased risk for panic disorder through genetic epidemiology and the use of genetically modified mouse models. The integration of human and animal studies targeting behavioral, systems-level, cellular and molecular levels will most probably help identify new molecules with potential impact on the pathogenetic aspects of the disease.

Monoamine oxidase A gene is associated with borderline personality disorder

OBJECTIVE

Monoamine oxidase A is a mitochondrial enzyme involved in the degradation of certain neurotransmitter amines: serotonin and norepinephrine. As for its role in aggression, impulsivity, suicide and mood liability, monoamine oxidase A can be considered a functional candidate in borderline personality disorder.

METHODS

To test for this hypothesis we genotyped two polymorphic markers in monoamine oxidase A gene, a promoter VNTR and an rs6323 (T941G) in exon 8, in 111 Caucasian borderline personality disorder patients and 289 Caucasian healthy controls. Association analyses using individual marker and haplotype data were performed by a program of COCAPHASE in UNPHASED (MRC Human Genome Mapping Project Resource Centre, Cambridge, UK).

RESULTS

We found that the borderline personality disorder patients had a high frequency of the high activity VNTR alleles (chi=4.696, P=0.03) and a low frequency of the low activity haplotype (chi=5.089, P=0.02).

CONCLUSION

These results show that the monoamine oxidase A gene may play an important role in the etiological development of the borderline personality disorder.

The MAOA T941G polymorphism and short-term treatment response to mirtazapine and paroxetine in major depression

This study investigated the possible association of the MAOA T941G gene variant with differential antidepressant response to mirtazapine and/or paroxetine in 102 patients with major depression (DSM-IV criteria) participating in a randomized double-blind controlled clinical trial. Female mirtazapine-treated patients homozygous for the T-allele had a significantly faster and better treatment response than TG/GG-patients. In males, we failed to show an association between MAOA T941G gene variant and mirtazapine response. In the paroxetine-treated group, there were no significant differences in treatment response between MAOA T941G genotype groups. Time course of response and antidepressant efficacy of mirtazapine, but not paroxetine, seem to be influenced in a clinically relevant manner by this allelic variation within the MAOA gene, at least in female patients. An independent replication of our finding is needed. If replicated, genotyping of this locus could become a promising tool to predict response to mirtazapine treatment in females suffering from major depression.

Molecular genetic findings in suicidal behavior: what is beyond the serotonergic system?

Various studies provide consistent evidence for a genetic component in suicidal behavior. First molecular genetic studies concentrated on genes of the serotonergic system based on the biochemical evidence that serotonergic neurotransmission is implicated in this behavior. Furthermore, genes of the dopaminergic and noradrenergic neurotransmitter systems have also been the subjects of investigations in this context. Some epidemical and clinical studies showed that low serum cholesterol levels are associated with suicidal behavior and genes involved in these pathways have been investigated. Microarray experiments provide the possibility of genome-wide gene expression analysis and help to investigate associated molecular mechanisms. The aim of this article is to review molecular genetic studies in suicidal behavior and to emphasize findings on new genes.

Genetics of suicide

The concept that genetic factors contribute to the complex trait of suicidal behaviour has stimulated much work aimed at identifying susceptibility genes. So far molecular genetic studies focused on the serotonergic pathway as the intent to die and the lethality of suicide acts were related to the serotonergic system. Two genes have so far emerged as being involved in the vulnerability for suicidality: first, the intronic polymorphisms (A218C or A779C) of the tryptophan hydroxylase 1 (TPH1) gene, which was suggested as a quantitative risk factor for suicidal behaviour; second, the insertion/deletion polymorphism of the serotonin transporter gene (5-HTTLPR), which does not seem to be involved in general suicidal behaviour, but in violent and repeated suicide attempts. The data have further shown that the MAOA gene, which is consistently associated with impulsive-aggressive personality traits, is not related to suicide but might induce violent methods in subjects with other suicide risk factors. Predominantly negative were the findings with any type of the serotonin receptors and inconsistent with catecholamine-synthesizing and -metabolizing enzymes or with the dopaminergic receptors. This paper reviews the status of current knowledge in this area, points to the weakness of the investigations and presents new approaches beyond the serotonergic system.

Carving chaos: genetics and the classification of mood and psychotic syndromes

Though Kraepelin's century-old division of major mental illness into mood disorder and schizophrenia remains in place, debate abounds over the most appropriate classification. Although these arguments previously rested solely on clinical grounds, they now are rooted in genetics and neurobiology. This article reviews evidence from the fields of genetic epidemiology, linkage, association, cytogenetics, and gene expression. Taken together, these data suggest some overlap in the genes that predispose to bipolar disorder and schizophrenia. One gene, DAOA (D-amino acid oxidase activator, also known as G72), has been repeatedly implicated as an overlap gene, while DISC1 and others may constitute additional shared susceptibility genes. Further, some evidence implicates syndromes of co-occurring mood and psychotic symptoms in association with the putative risk alleles in overlap genes. From a nosologic perspective, the existence of overlap genes, coupled with the genotype-phenotype correlations discovered to date, supports the reality of the much debated schizoaffective disorder. Potential non-overlap syndromes--such as nonpsychotic bipolar disorder or cyclothymic temperament, on the one hand, and negative symptoms or the deficit syndrome, on the other--could turn out to have their own unique genetic determinants. If genotypes are to be the anchor points of a clinically useful system of classification, they must ultimately be shown to inform prognosis, treatment, and prevention. No gene variants have yet met these tests in bipolar disorder or schizophrenia.

Further clarification of the contribution of the tryptophan hydroxylase (TPH) gene to suicidal behavior using systematic allelic and genotypic meta-analyses

Suicide is a major public health issue, especially in western countries, accounting for approximately 1 million deaths every year throughout the world. The tryptophan hydroxylase (TPH) gene has been extensively studied as a candidate for suicidal behavior due to its role in serotonergic neurotransmission. Since the first study associating the gene with schizophrenia, there have been many attempts to replicate it. However, a number of these studies have produced contrary results, possibly reflecting inadequate statistical power and the use of different populations. Association data relating European and, more particularly, Asian populations has become increasingly available in recent years. To examine whether the aggregate data provide evidence of statistical significance, the current meta-analysis has combined all the published studies up to July 2005, and examined the polymorphisms (A779C, A218C, A-6526G) in the context of varied suicidal behaviors by analyzing the studies in total and in subsets. Compared with the inconsistent results of previous studies, the current results (22 references) confirm a strong overall association between suicidal behavior and the A779C/A218C polymorphisms, supporting the involvement of TPH in the pathogenesis of suicidal behavior.

Cluster B personality disorders are associated with allelic variation of monoamine oxidase A activity

Genetic variants of the monoamine oxidase A (MAOA) have been associated with aggression-, anxiety-, and addiction-related behavior in several nonclinical and clinical populations. Here, we investigated the influence of allelic variation of MAOA activity on aggression-related personality traits and disease risk in patients with personality disorders. Personality disorders were diagnosed with the Structured Clinical Interview of DSM-IV and were allocated to cluster A, B, and C. Personality features were assessed by the revised NEO Personality Inventory and the Tridimensional Personality Questionnaire. The genotype of the MAOA gene-linked polymorphic region (MAOA-LPR) was determined in 566 patients with personality disorders and in 281 healthy controls. MAOA genotype was significantly associated with cluster B personality disorders (chi2=7.77, p=0.005, df=1) but not with cluster C personality disorders. In total, 26.0% of cluster B patients were hemi- or homozygous for the low-activity variant of the MAOA genotype, compared to 16.4% in the control group. Associations between MAOA variants and personality domains related to impulsivity and aggressiveness were inconsistent. Our findings further support the notion that allelic variation of MAOA activity contributes modestly to the balance of hyper- (impulsive-aggressive) and hyporeactive (anxious-depressive) traits.

The monoamine oxidase A gene may influence the means used in suicide attempts

OBJECTIVE

Compelling evidence suggests that serotonin system dysfunction is associated with certain behavioral disorders, including suicidal behavior and impulsive aggression. A functional polymorphism in the promoter region of the monoamine oxidase A gene (uVNTR) was recently identified and the presence of the 2-3 alleles was found to be associated with a higher level of transcription, central nervous system serotonergic responsivity and impulsive aggression. A dinucleotide repeat in intron 2 of the gene (monoamine oxidase A-CAn) has been described previously, and is in linkage disequilibrium with the variable number of tandom repeats (VNTR). The aim of the study was to investigate, in a large sample, whether the monoamine oxidase A gene was involved in the susceptibility to suicidal behavior.

METHODS

We genotyped 738 West European Caucasians, who had made suicide attempts, and 222 controls of the same ethnic origin, with no history of suicidal behavior. The two variants of the monoamine oxidase A gene have been tested.

RESULTS

We did not find any association between the two monoamine oxidase A gene variants and suicidal behavior. However, the frequency of the uVNTR 2-3 alleles was significantly higher in men who had attempted suicide by violent means than in men who had used non-violent means. The odds ratio for the uVNTR 2-3 alleles versus the uVNTR 1-4 alleles was 2.17 [95% confidence interval (1.08-4.35)]. Haplotypes did not allow strengthening the effect observed with the uVNTR.

CONCLUSION

These results suggest that an excess of high-activity monoamine oxidase A gene promoter alleles may be associated with traits orienting suicidal behavior towards a violent act.

Population-based and family-based studies on the serotonin transporter gene polymorphisms and bipolar disorder: a systematic review and meta-analysis

The serotonin transporter (5-HTT) is a candidate gene for bipolar disorder (BPD). It has been investigated for association with the illness in a series of studies, but overall results have been inconsistent and its role in the disorder remains controversial. Systematic reviews using meta-analytical techniques are a useful method for objectively and reproducibly assessing individual studies and generating combined results. We performed two meta-analyses of published studies--both population-based and family-based studies--investigating the association between BPD and the 5-HTT gene-linked polymorphic region (5-HTTLPR) and the intron 2 variable numbers of tandem repeats (VNTR) polymorphisms. The literature was searched using Medline and Embase to identify studies for inclusion. We statistically joined population-based and family-based studies into a single meta-analysis. For both polymorphisms, our review revealed significant pooled odds ratios (ORs): 1.12 (95% CI 1.03-1.21) for the 5-HTTLPR and 1.12 (95% CI 1.02-1.22) for the intron 2 VNTR. Meta-regression showed that neither the study type (population-based vs family-based; P=0.41 for the 5-HTTLPR and P=0.91 for the intron 2 VNTR) nor the sample ethnicity (Caucasian vs non-Caucasian; P=0.35 for the 5-HTTLPR and P=0.66 for the intron 2 VNTR) significantly contributed to the heterogeneity of the meta-analyses. The observed ORs could be regarded simply as a very small but detectable effect of the 5-HTT, which has an additive effect when combined with other susceptibility loci. Alternative hypotheses on this finding were also discussed: a stronger effect of the haplotypes involving the two polymorphisms or other SNP markers; a more direct effect of these polymorphisms on specific phenotypes of BPD; and the presence of gene-environment interaction as a mediator of the genetic effects of 5-HTT.

Structural variation of the monoamine oxidase A gene promoter repeat polymorphism in nonhuman primates

By conferring allele-specific transcriptional activity on the monoamine oxidase A (MAOA) gene in humans, length variation of a repetitive sequence [(variable number of tandem repeat (VNTR)] in the MAOA promoter influences a constellation of personality traits related to aggressive and antisocial behavior and increases the risk of neurodevelopmental and psychiatric disorders. Here, we have analyzed the presence and variability of this MAOA promoter repeat in several species of nonhuman primates. Sequence analysis of MAOA's transcriptional control region revealed the presence of the VNTR in chimpanzee (Pan troglodytes), bonobo (Pan paniscus), gorilla (Gorilla gorilla), orangutan (Pongo pygmaeus), rhesus macaque (Macaca mulatta) and Gelada baboon (Theropithecus gelada). The majority of P. troglodytes and P. paniscus showed a single repeat with a sequence identical to the VNTR sequence in humans. In contrast, analyses of the remaining species revealed shorter sequences similar to the first 18 bp of human VNTR. Compared with other nonhuman primates, the VNTR sequence of M. mulatta showed the highest length variability with allele frequencies of 35, 25 and 40% for the five, six and seven repeat variants, respectively. The extent of variability of the MAOA promoter repeat in both rhesus monkeys and humans supports the notion that there may be a relationship between functional MAOA expression and aggression-related traits in humans and rhesus macaque populations.