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

Effective factors in the pathogenesis of Toxoplasmagondii

Toxoplasma gondii (T. gondii) is a cosmopolitan protozoan parasite in humans and animals. It infects about 30 % of the human population worldwide and causes potentially fatal diseases in immunocompromised hosts and neonates. For this study, five English-language databases (ScienceDirect, ProQuest, Web of Science, PubMed, and Scopus) and the internet search engine Google Scholar were searched. This review was accomplished to draw a global perspective of what is known about the pathogenesis of T. gondii and various factors affecting it. Virulence and immune responses can influence the mechanisms of parasite pathogenesis and these factors are in turn influenced by other factors. In addition to the host's genetic background, the type of Toxoplasma strain, the routes of transmission of infection, the number of passages, and different phases of parasite life affect virulence. The identification of virulence factors of the parasite could provide promising insights into the pathogenesis of this parasite. The results of this study can be an incentive to conduct more intensive research to design and develop new anti-Toxoplasma agents (drugs and vaccines) to treat or prevent this infection. In addition, further studies are needed to better understand the key agents in the pathogenesis of T. gondii.

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.

Investigating the Clinical Profile of Suicide Attempters Who Used a Violent Suicidal Means

In our study, we aimed to explore the profile of the high-risk subgroup of suicide attempters that used a violent means compared to suicide attempters that chose a non-violent suicide means. Therefore, we recruited a sample of inpatients with recent suicide attempts in three psychiatric hospitals in Thuringia, Germany. We used a structured clinical interview to assess the psychiatric diagnoses, sociodemographic data, and characteristics of the suicide attempt. Furthermore, we used several validated clinical questionnaires to measure suicidal ideations, suicide intent, depression severity, hopelessness, impulsivity, aggression, anger expression, and childhood trauma. We compared 41 individuals using violent means to 59 using non-violent means with univariate and multivariate statistical analyses. We found significantly (corrected for multiple comparisons) higher levels of impulsivity-related sensation-seeking in violent suicide attempters in univariate and multivariate analyses, and additionally in anger expression directed inward at an uncorrected statistical threshold. Besides that, there were no significant differences between the two groups. We assume that underlying neurocognitive mechanisms, such as impaired decision-making processes and/or differences in risk/loss assessment, could explain the higher levels of questionnaire-based sensation-seeking in subjects who use violent suicide means. Further research is needed, including neuroimaging and biochemical techniques, to gain more insight into the mechanisms underlying the choice of a suicidal means.

Toxoplasmosis: Targeting neurotransmitter systems in psychiatric disorders

The most common form of the disease caused by Toxoplasma gondii (T. gondii) is latent toxoplasmosis due to the formation of tissue cysts in various organs, such as the brain. Latent toxoplasmosis is probably a risk factor in the development of some neuropsychiatric disorders. Behavioral changes after infection are caused by the host immune response, manipulation by the parasite, central nervous system (CNS) inflammation, as well as changes in hormonal and neuromodulator relationships. The present review focused on the exact mechanisms of T. gondii effect on the alteration of behavior and neurotransmitter levels, their catabolites and metabolites, as well as the interaction between immune responses and this parasite in the etiopathogenesis of psychiatric disorders. The dysfunction of neurotransmitters in the neural transmission is associated with several neuropsychiatric disorders. However, further intensive studies are required to determine the effect of this parasite on altering the level of neurotransmitters and the role of neurotransmitters in the etiology of host behavioral changes.

Monoamino Oxidase A Gene Single-Nucleotide Polymorphisms and Methylation Status and the Risk of Violent Suicide Attempts in Affective Disorder Patients

Background: When investigating the neurobiology of suicidal behavior, Monoamino Oxidase A (MAOA) is one of the prime suspects to consider. Interestingly, MAOA dysregulation has also been associated with violent behavior in previous publications. In the present study, we aimed to establish an association between polymorphisms of the MAOA gene and methylation status of the MAOA gene Exon I, and suicide attempts with violent methods in a sample of affective disorder patients. Methods: Eight hundred fourteen Caucasian affective disorder patients were assessed at the Department of Psychiatry and Psychotherapy of the Medical University Vienna, the Karl Landsteiner University for Health and Science and Zentren für seelische Gesundheit, BBRZ-Med Leopoldau. An assemblage of psychiatric interviews was performed (e.g., SCAN, HAMD, SBQ-R, CTQ) and DNA samples of peripheral blood cells were collected for Sequenom MassARRAY® iPLEX Gold genotyping and Multiplexed and Sensitive DNA Methylation Testing. Results: Female affective disorder patients with a history of violent suicide attempt were found to have a significantly increased frequency of the AA genotype in the rs5906957 single nucleotide polymorphism (p = 0.003). Furthermore, the MAOA gene exon I promoter region showed significantly decreased methylation in female violent suicide attempter(s) as opposed to female affective disorder patients who had no history of suicide attempt or no history of suicide attempt with violent method. Limitations: The small sample size hampers to reveal small genetic effects as to be expected in psychiatric disorders. Conclusions: This study offers promising findings about associations between the MAOA gene and violent suicide especially in women.

Suicide: Genetics and Heritability

Nature vs nurture is, and has been, a never stopping debate since Lamarck and Darwin exposed their corresponding theories on evolution, and even before them, such discussion already existed. Is suicide a heritable conduct? Is it learnt? Maybe the answer is both and none, at the same time. From genetic twin studies to epigenetic and environmental influence on development, this chapter aims to take a look at different points of view and most relevant theories in one of the worlds leading causes of death, specially for young individuals. We explore different studies aiming to find biomarkers for suicide, as well as other traits frequently encountered in individuals who engage in suicidal behavior, such as impulsivity, aggressivity, and hopelessness. Finally, this chapter also looks at some of the most recent approaches in treatment and prevention of suicidal behavior, in order to highlight what they have in common and try to explain (at least partially) why they could be effective.

Interleukin (IL)-8 polymorphisms contribute in suicide behavior

Previous studies have highlighted the role of immune dysregulation in suicide behavior. Interleukin (IL)-8 is a chemokine with neuroprotective effects whose lower serum concentrations have been detected in individuals committed suicide. In the present study, we genotyped three single nucleotide polymorphisms (SNPs) within IL-8 gene (rs4073, rs2227306 and rs1126647) in 229 individuals who attempted suicide with soft suicide methods, 235 suicide victims and 290 individuals without any history of psychiatric disorders or suicide attempt. The T allele of rs4073 was significantly over-represented in suicide attempt group compared with both control and completed suicide groups (adjusted P values of 8.3E-7 and 9.8E-8 respectively). This SNP was associated with suicide attempt in both dominant and co-dominant models (P values of 6.2E-9 and 4.3 E-8 respectively). The genotype and allele frequencies of other SNPs were not significantly different among the three study groups. The T C A haplotype (rs4073, rs2227306 and rs1126647 respectively) were significantly less prevalent in completed suicide group compared with suicide attempt group (OR (95% CI) = 0.63 (0.46-0.86), adjusted P value = 0.03). Besides, the A T A haplotype has significant lower frequency in individuals who attempted soft suicide compared with controls (OR (95% CI) = 0.44 (0.26-0.75), adjusted P value = 0.02). However, this haplotype was significantly more prevalent in individuals attempted hard methods compared with those attempted soft methods (OR (95% CI) = 2.21 (1.26-3.87), adjusted P value = 0.04). The present study provided further evidence for the role of IL-8 in suicide behavior.

Serotonergic 5HTTLPR/rs25531 s-allele homozygosity associates with violent suicides in male citalopram users

Depressive disorders are involved as a background factor in over 50% of suicide cases. The most widely used antidepressants today are serotonin selective reuptake inhibitors (SSRIs). However, not all users benefit from SSRI medication. Although the overall number of suicides in Finland have decreased notably during the last decade, the annual rate is still relatively high, particularly in male population. In this study, we tested the hypothesis that the genetic variants associated with decreased citalopram efficiency, 5HTTLPR/rs25531, and increased impulsive behavior, MAOA-uVNTR and HTR2B Q20*, are more frequent among citalopram users committing suicide than among the citalopram users in general. Also the effect of alcohol was evaluated. The study population comprised 349 suicide victims (184 males and 165 females). Based on the suicide method used, cases were divided into two groups; violent (88 males and 49 females) and non-violent (96 males and 116 females). The control group (284; 159 males and 125 females) consisted of citalopram users who died of causes other than suicide. We found that male citalopram users with low functioning s/s genotype of 5HTTLPR/rs25531 were in increased risk to commit violent suicide (OR 2.50, 95%CI 1.15-5.42, p = 0.020). Surprisingly, high blood alcohol concentration was observed to be a risk factor only in non-violent suicides (both males and females), but not in violent ones. No association between suicides and MAOA-uVNTR and HTR2B Q20*, which have been previously connected to violent and impulsive behavior, was detected.

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.

Genetic Association Studies of Suicidal Behavior: A Review of the Past 10 Years, Progress, Limitations, and Future Directions

Suicidal behaviors (SBs), which range from suicidal ideation to suicide attempts and completed suicide, represent a fatal dimension of mental ill-health. The involvement of genetic risk factors in SB is supported by family, twin, and adoption studies. The aim of this paper is to review recent genetic association studies in SBs including (i) case-control studies, (ii) family-based association studies, and (iii) genome-wide association studies (GWAS). Various studies on genetic associations have tended to suggest that a number of genes [e.g., tryptophan hydroxylase, serotonin receptors and transporters, or brain-derived neurotrophic factors (BDNFs)] are linked to SBs, but these findings are not consistently supported by the results obtained. Although the candidate-gene approach is useful, it is hampered by the present state of knowledge concerning the pathophysiology of diseases. Interpretations of GWAS results are mostly hindered by a lack of annotation describing the functions of most variation throughout the genome. Association studies have addressed a wide range of single-nucleotide polymorphisms in numerous genes. We have included 104 such studies, of which 10 are family-based association studies and 11 are GWAS. Numerous meta-analyses of case-control studies have shown significant associations of SB with variants in the serotonin transporter gene (5-HTT or SLC6A4) and the tryptophan hydroxylase 1 gene (TPH1), but others report contradictory results. The gene encoding BDNF and its receptor (NTRK2) are also promising candidates. Only two of the GWAS showed any significant associations. Several pathways are mentioned in an attempt to understand the lack of reproducibility and the disappointing results. Consequently, we review and discuss here the following aspects: (i) sample characteristics and confounding factors; (ii) statistical limits; (iii) gene-gene interactions; (iv) gene, environment, and by time interactions; and (v) technological and theoretical limits.

Serotonergic genes and suicide: a systematic review

Suicide is one of the leading causes of death in the world. Its aetiology is complex and diverse, however, epidemiological studies show that suicidal behavior is partly heritable. Neurobiological evidence implicates serotonergic dysfunction in suicidality, stimulating genetic research to focus on genes related to the serotonergic system. In this paper, we review evidence from studies examining the association between various serotonergic genes (Tryptophan Hydroxylase genes: TPH1; TPH2, Serotonin Transporter gene: 5-HTTLPR in SLC6A4, Serotonin Receptor genes: HTR1A, HTR2A, HTR1B, HTR2C and Monoamine Oxidase A gene: MAOA) and suicidal behavior. The data show associations between variation on the TPH1 gene and 5-HTTLPR gene and violent suicidal behavior in Caucasian populations, with the least inconsistencies. Results are mixed for the TPH2 gene and serotonin receptor genes, but for some genes, studies that include haplotypic analyses or that examine a larger coding region of the genes tend to provide more reliable results. Findings on endophenotypes of suicidality, such as aggression and impulsivity traits, show positive associations for the TPH1, HTR2A, and MAOA genes, but need further replication, since negative associations are also occasionally reported. Since genes can only partially explain suicidal risk, several studies during the past decade have tried to incorporate environmental factors in the susceptibility model. Studies to date show that variation on the 5-HTTLPR, MAOA and HTR2A gene can interact with stressful life events to increase risk for suicidal behavior. Limitations of case-control studies are discussed and future considerations are put forward with regard to endophenotypic measurements and gene-environment interactions.

MAOA and MAOB polymorphisms and anger-related traits in suicidal participants and controls

MAOA and, to a lesser extent, MAOB polymorphisms have been related to aggression traits and suicidality. We aimed to investigate the role of MAOA and MAOB in suicidal versus non-suicidal participants and interactions between genetic variation and suicidal status on aggression and anger-related traits. The sample was composed of three groups: one group of suicide attempters (n = 171, males 35.1 %), one group of suicide completers (n = 90, males 57.8 %) and a healthy control group (n = 317, males 43.8 %). We examined the following markers: MAOA rs909525, rs6323, and rs2064070, and MAOB rs1799836. Anger traits were measured with the state-trait anger expression inventory (STAXI) and aggression traits with the questionnaire for measuring factors of aggression (FAF). Associations were separately examined for males and females. Variation in the three MAOA variants was associated with higher levels of anger expressed outwards (STAXI "anger-out" subscale) in male suicidal patients compared to controls (p < 0.001). In females, the C allele of rs6323 showed higher scores on the same subscale ("anger out") (p = 0.002). Allele frequencies of the MAOA rs909525 were associated with suicidality (p < 0.007). Our findings show an association between genetic variation in three polymorphisms of the MAOA and anger traits in suicidal males and one replication for the functional variant rs6323 in females. This relationship was stronger than a direct genetic association with suicide status. Future studies incorporating endophenotypic measures of anger and aggression in suicidal participants are warranted.

Genetics of emergent suicidality during antidepressive treatment--data from a naturalistic study on a large sample of inpatients with a major depressive episode

Factors contributing to treatment-emergent suicidal ideation (TESI) using antidepressants have been in the focus of recent research strategies. We investigated previously established clinical predictors of TESI and combined these with several polymorphisms of candidate genes in patients with major depressive disorder. Common polymorphisms involved in the tryptophan hydroxylase 1 (TPH1) and 2 (TPH2), serotonin transporter, monoamine oxidase A (MAOA) and brain-derived neurotrophic factor (BDNF) were investigated in a naturalistic inpatient study of the German research network on depression. We compared patients showing TESI with non-TESI suicidal patients and with non-suicidal patients using univariate tests to detect relevant factors, which were further tested in logistic regression and CART (Classification and Regression Trees) analyses. Of the 269 patients, TESI occurred in 22 patients (17 female), 117 patients were defined as non-TESI suicidal patients, and 130 patients were classified as non-suicidal. When comparing cases with both control groups we found the TPH2 rs1386494 (C/T) polymorphism to be moderately associated with TESI (Univariate tests: TESI vs. non-suicidality: p=0.005; adjusted: p=0.09; TESI vs. non-TESI suicidal patients: p=0.0024; adjusted: p=0.086). This polymorphism remained the only significant genetic factor in addition to clinical predictors in logistic regression and CART analyses. CART analyses suggested interactions with several clinical predictors. Haplotype analyses further supported a contribution of this polymorphism in TESI. The TPH2 rs1386494 (C/T) polymorphism might contribute to the genetic background of TESI. This polymorphism has been previously associated with committed suicide and major depressive disorder. The small number of cases warrants replication in larger patient samples. Lack of a placebo control group hampers definite conclusions on an association with antidepressive treatment.

An association study of suicide and candidate genes in the serotonergic system

INTRODUCTION

Strong evidence demonstrates a genetic susceptibility to suicidal behaviour and a relationship between suicide and mental disorders. The aim of this study was to test for association between suicide and five selected genetic variants, which had shown association with suicide in other populations.

METHOD

We performed a nationwide case-control study on all suicide cases sent for autopsy in Denmark between the years 2000 and 2007. The study comprised 572 cases and 1049 controls and is one of the largest genetic studies in completed suicide to date. The analysed markers were located within the Serotonin Transporter (SLC6A4), Monoamine Oxidase-A (MAOA) and the Tryptophan Hydroxylase I and II (TPH1 and TPH2) genes.

RESULTS

None of the genetic markers within SLC6A4, MAOA, TPH1 and TPH2 were significantly associated with completed suicide or suicide method in the basic association tests. Exploratory interaction test showed that the minor allele of rs1800532 in TPH1 has a protective effect for males younger than 35 years and females older than 50 years, whereas for the oldest male subjects, it tended to be a risk factor. We also observed a significant interaction between age-group and the 5-HTTLPR genotype (with and without rs25531) in SLC6A4. The long allele or high expression allele tends to have a protective effect in the middle age-group.

LIMITATION

We only analysed a limited number of genetic variants.

CONCLUSION

None of the analysed variants are strong risk factors. To reveal a better understanding of the genes involved in suicide, we suggest future studies should include both genetic and non-genetic factors.

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.

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.

Genetic and environmental contributions to self-reported thoughts of self-harm and suicide

Thoughts of self-harm and suicidal behavior are thought to be influenced by both genetics and environment. Molecular genetic studies are beginning to address the question of which genes may be involved and whether different genes may be expressed in men and women. We examined thoughts of self-harm and suicidal behavior in a large general population twin sample including male and female same- and opposite-sex twins. In this study, data on self-reported thoughts of self-harm and suicide were obtained from self-report questionnaires (Beck Depression Inventory and Youth or Adult Self Report forms) in 6,265 twin pairs (11,008 individuals) aged 11-90 (62% female) from the Netherlands Twin Registry. Liability threshold models were compared including sex and age (linear and quadratic) effects. Models were compared using measures of parsimony to calculate the simplest model to the data. A model with additive genetic and unique environmental contributions fitted the data for both males and females. There were no qualitative sex differences, but the relative contributions differed between men and women. Heritability was higher in women (0.74, 95% CI 0.65-0.81) than men (0.45, 95% CI 0.28-0.61). The remaining variance was accounted for by environmental influence unique to an individual. These results suggest contributions from additive genetic factors to self-reported thoughts of self-harm and suicide and support the continued study of both molecular genetic and individual-specific environmental risk factors.

Autism severity is associated with child and maternal MAOA genotypes

Autism severity is associated with child and maternal MAOA genotypes. We replicated and extended a previously reported association between autism severity and a functional polymorphism in the monoamine oxidase A (MAOA) promoter region, MAOA-uVNTR, in a sample of 119 males, aged 2-13 years, with autism spectrum disorder from simplex families. We demonstrated that (i) boys with the low activity 3-repeat MAOA allele had more severe sensory behaviors, arousal regulation problems, and aggression, and worse social communication skills than males with the high activity allele; and (ii) problems with aggression, as well as with fears and rituals, were modified by the mothers' genotype. Boys with the 4-repeat high activity allele who had homozygous 4-repeat mothers showed increased severity of these behaviors relative to those born to heterozygous mothers. These findings indicate the importance of considering maternal genotype in examining associations of MAOA and other genes with behavior in male offspring.

Recent molecular genetic studies and methodological issues in suicide research

Suicide behavior (SB) spans a spectrum ranging from suicidal ideation to suicide attempts and completed suicide. Strong evidence suggests a genetic susceptibility to SB, including familial heritability and common occurrence in twins. This review addresses recent molecular genetic studies in SB that include case-control association, genome gene-expression microarray, and genome-wide association (GWA). This work also reviews epigenetics in SB and pharmacogenetic studies of antidepressant-induced suicide. SB fulfills criteria for a complex genetic phenotype in which environmental factors interact with multiple genes to influence susceptibility. So far, case-control association approaches are still the mainstream in SB genetic studies, although whole genome gene-expression microarray and GWA studies have begun to emerge in recent years. Genetic association studies have suggested several genes (e.g., serotonin transporter, tryptophan hydroxylase 2, and brain-derived neurotrophic factor) related to SB, but not all reports support these findings. The case-control approach while useful is limited by present knowledge of disease pathophysiology. Genome-wide studies of gene expression and genetic variation are not constrained by our limited knowledge. However, the explanatory power and path to clinical translation of risk estimates for common variants reported in genome-wide association studies remain unclear because of the presence of rare and structural genetic variation. As whole genome sequencing becomes increasingly widespread, available genomic information will no longer be the limiting factor in applying genetics to clinical medicine. These approaches provide exciting new avenues to identify new candidate genes for SB genetic studies. The other limitation of genetic association is the lack of a consistent definition of the SB phenotype among studies, an inconsistency that hampers the comparability of the studies and data pooling. In summary, SB involves multiple genes interacting with non-genetic factors. A better understanding of the SB genes by combining whole genome approaches with case-control association studies, may potentially lead to developing effective screening, prevention, and management of SB.

Molecular-genetic correlates of self-harming behaviors in eating-disordered women: findings from a combined Canadian-German sample

Across populations, findings suggest that rates of self-mutilation, suicidal acts, and other self-harming behaviors (SHBs) may be influenced by polymorphisms that code for activity of the serotonin transporter (e.g., 5HTTLPR) and the enzyme, monoamine oxidase A (e.g., MAOAuVNTR). SHBs being common in patients with Eating Disorders (EDs), we evaluated (in a large sample of eating-disordered women) relationships between triallelic 5HTTLPR and MAOAuVNTR variants, on the one hand, and SHBs, on the other. We had 399 eating-disordered women report on eating symptoms and lifetime history of SHBs, and provide blood samples for genotyping. Individuals carrying high-function MAOAuVNTR alleles reported a history of SHBs about twice as often as did carriers of low-function alleles. We obtained no comparable main effect of 5HTTLPR, or MAOAuVNTR×5HTTLPR interaction effect. Genetic variations did not predict severity of eating symptoms. As in other populations, our findings link the MAOAuVNTR high-function alleles with increased risk of self-directed harm in bulimic females. We discuss theoretical and clinical ramifications of our results.

Neither single-marker nor haplotype analyses support an association between monoamine oxidase A gene and bipolar disorder

Monoamine oxidase A (MAOA) abnormality has been suggested as a crucial factor in the pathogenesis of mood disorder, because MAOA is associated with the metabolism of monoamines such as serotonin and norepinephrine. Various MAOA gene polymorphisms have been investigated for possible associations with bipolar disorder (BD), but the results are controversial. Our goal was to investigate whether MAOA gene polymorphisms, especially the promoter uVNTR polymorphism and the EcoRV polymorphism, are associated either with BD or with different clinical subtypes of BD. A total of 714 Han Chinese subjects in Taiwan (305 controls and 409 BD patients) were recruited for study. All subjects were interviewed with the Chinese Version of the Modified Schedule of Affective Disorders and Schizophrenia-Lifetime; BD was diagnosed according to DSM-IV criteria. Genotyping for MAOA polymorphisms was performed using PCR and restriction fragment length polymorphism. The MAOA promoter polymorphisms uVNTR and EcoRV were not associated with BD or any of its subtypes, in either the frequencies of alleles or genotypes. In multiple logistic regression and haplotype frequency analysis, we confirmed these negative results in both females and males. Our results suggest that MAOA polymorphisms do not play a major role in pathogenesis of BD or its clinical subtypes in Han Chinese.

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.

Gene expression profiling of post-mortem orbitofrontal cortex in violent suicide victims

The neurobiological basis of suicidal behaviour is multifactorial and complex. Several lines of evidence indicate that environmental factors as well as multiple genes and interactions of both are implicated in its aetiology. The aim of this study was to establish the transcriptomic expression profile of post-mortem brain tissue of suicide victims in order to identify new candidate genes and biological patterns for suicidal behaviour. Post-mortem orbitofrontal cortex tissue was derived from 11 suicide victims and 10 non-psychiatric controls carefully selected from a brain bank of over 150 brains, and the expression of more than 23000 messenger RNAs was assessed in this case-control study. Validation experiments were carried out using quantitative RT-PCR as an independent method. A classification of the differentially expressed genes according to their biological function and statistical analyses of the data were performed in order to identify biological pathways that are over-represented in the suicide group. In total, 124 transcripts demonstrated significant changes (fold changes > or = 1.3, p value < or = 0.01), with 59 showing under-, and 65 over-expression in the suicide group. The results could be validated for nine particularly interesting transcripts (CDCA7L, CDH12, EFEMP1, MLC1, PCDHB5, PTPRR, S100A13, SCN2B, and ZFP36). The pathway analysis showed that the Gene Ontology categories 'central nervous system development', 'homophilic cell adhesion', 'regulation of cell proliferation' and 'transmission of nerve impulse' were significantly enriched. The differentially expressed genes and significant biological processes might be involved in the pathophysiology of suicide and warrant further attention.

The influence of four serotonin-related genes on decision-making in suicide attempters

Genetic factors have been associated with the vulnerability to suicidal behavior. We previously reported decision-making impairment in suicide attempters and hypothesized that these cognitive alterations may represent an endophenotype of suicidal behavior. In this study, we aimed to investigate the influence of four serotonin-related genes relevant to suicidal behavior on decision-making, in a large population of suicide attempters. The Iowa Gambling Task was used to assess decision-making in 168 patients with a personal history of attempted suicide. Patients were genotyped for four serotonergic polymorphisms: 5HTTLPR, TPH1 A218C, MAOA u-VNTR, and TPH2 rs1118997. Patients carrying the 5HTTLPR-ll and -sl, TPH1-CC and -AC, MAOA-HH (in women) and TPH2-AA genotypes significantly improved their performance during the task, suggesting a genetic modulation of the learning process required for advantageous decision-making. In contrast, genotypes previously associated with a higher risk of suicidal behavior, a greater sensitivity to the environment and a higher propensity to negative feelings are those conferring poorer learning abilities. We hypothesize that the influence of genetic factors on the vulnerability to suicidal behavior may partly be achieved through their modulation of decision-making and particularly its learning component.

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.