Brains Of Suicide Completers Research Articles

Genome-wide DNA methylation meta-analysis in the brains of suicide completers

Suicide is the second leading cause of death globally among young people representing a significant global health burden. Although the molecular correlates of suicide remains poorly understood, it has been hypothesised that epigenomic processes may play a role. The objective of this study was to identify suicide-associated DNA methylation changes in the human brain by utilising previously published and unpublished methylomic datasets. We analysed prefrontal cortex (PFC, n = 211) and cerebellum (CER, n = 114) DNA methylation profiles from suicide completers and non-psychiatric, sudden-death controls, meta-analysing data from independent cohorts for each brain region separately. We report evidence for altered DNA methylation at several genetic loci in suicide cases compared to controls in both brain regions with suicide-associated differentially methylated positions enriched among functional pathways relevant to psychiatric phenotypes and suicidality, including nervous system development (PFC) and regulation of long-term synaptic depression (CER). In addition, we examined the functional consequences of variable DNA methylation within a PFC suicide-associated differentially methylated region (PSORS1C3 DMR) using a dual luciferase assay and examined expression of nearby genes. DNA methylation within this region was associated with decreased expression of firefly luciferase but was not associated with expression of nearby genes, PSORS1C3 and POU5F1. Our data suggest that suicide is associated with DNA methylation, offering novel insights into the molecular pathology associated with suicidality.

Regulation of impulsive and aggressive behaviours by a novel lncRNA.

High impulsive and aggressive traits associate with poor behavioural self-control. Despite their importance in predicting behavioural negative outcomes including suicide, the molecular mechanisms underlying the expression of impulsive and aggressive traits remain poorly understood. Here, we identified and characterized a novel long noncoding RNA (lncRNA), acting as a regulator of the monoamine oxidase A (MAOA) gene in the brain, and named it MAOA-associated lncRNA (MAALIN). Our results show that in the brain of suicide completers, MAALIN is regulated by a combination of epigenetic mechanisms including DNA methylation and chromatin modifications. Elevated MAALIN in the dentate gyrus of impulsive-aggressive suicides was associated with lower MAOA expression. Viral overexpression of MAALIN in neuroprogenitor cells decreased MAOA expression while CRISPR-mediated knock out resulted in elevated MAOA expression. Using viral-mediated gene transfer, we confirmed that MAALIN in the hippocampus significantly decreases MAOA expression and exacerbates the expression of impulsive-aggressive behavioural traits in CD1 aggressive mice. Overall, our findings suggest that variations in DNA methylation mediate the differential expression of a novel lncRNA that acts on MAOA expression to regulate impulsive-aggressive behaviours.

Functional DNA methylation in a transcript specific 3′UTR region of TrkB associates with suicide

Previous studies indicate that a subgroup of suicide completers has low cortical brain expression levels of TrkB-T1, a TrkB gene transcript that is highly expressed in astrocytes. Epigenetic modifications, including methylation changes in the TrkB promoter, partially explain TrkB-T1 low expression levels in brain tissue from suicide completers. The aim of this study was to investigate whether methylation changes in other regions of the TrkB gene could also contribute to the significant downregulation of the TrkB-T1 transcript observed in the brain of suicide completers. Methylation levels were assessed on BA8/9 from suicide completers expressing low TrkB-T1 transcript levels and controls, using custom-made Agilent arrays tiling the whole TrkB gene. After statistical correction for multiple testing, five probes located in the TrkB-T1 3′UTR region were found hypermethylated in the frontal cortex of suicide completers. These results were validated for four CpGs spanning a 150 bp sequence by cloning and Sanger sequencing bisulfite treated DNA. We found a significant correlation between the methylation level at these four CpGs and TrkB-T1 expression in BA8/9. Site-specific hypermethylation on this 3′UTR sequence induced decreased luciferase activity in reporter gene cell assays. Site-specific differential methylation in the TrkB-T1 3′UTR region associates with functional changes in TrkB-T1 expression and may play a significant role in the important decrease of cortical TrkB-T1 expression observed among suicide completers.

Primary Prevention Research in Suicide

At the American Association of Suicidology’s (AAS) 46th Annual Conference in Austin, Texas (http://www.suicidology.org/web/guest/education-and-training/annualconference), participants were challenged to address why there has not been more progress in reducing the rates of completed suicides (Berman, 2013). A draft of recommendations from the National Action Alliance for Suicide Prevention’s Research Prioritization Task Force was presented at the meeting and subsequently published in this journal (National Action Alliance for Suicide Prevention [NAASP], 2013a, 2013b). The purpose of this commentary is to address this challenge by emphasizing the importance of employing a disease etiology strategy that integrates molecular data with clinical data, environmental data, and health outcomes in a dynamic, iterative fashion. The recommendations of the Research Prioritization Task Force tackle important public health program issues and are embedded within seven key questions, summarized as: 1. Why do people become suicidal? 2. How do we better detect/predict risk? 3. What interventions prevent suicidal behavior? 4. What are the effective services for treating suicidal persons and preventing suicidal behavior? 5. How do we reduce stigma? 6. What are the suicide prevention interventions outside of health-care settings? 7. Which existing and new infrastructure needs are required to further reduce suicidal behavior? (NAASP, 2013b; Silverman et al., 2013)

Regulatory role of miRNAs in polyamine gene expression in the prefrontal cortex of depressed suicide completers

MicroRNAs (miRNAs) are small, non-coding RNA molecules that play an important role in the post-transcriptional regulation of mRNA. These molecules have been the subject of growing interest as they are believed to control the regulation of a large number of genes, including those expressed in the brain. Evidence suggests that miRNAs could be involved in the pathogenesis of neuropsychiatric disorders. Alterations in metabolic enzymes of the polyamine system have been reported to play a role in predisposition to suicidal behaviour. We have previously shown the expression of the polyamine genes SAT1 and SMOX to be down-regulated in the brains of suicide completers. In this study, we hypothesized that the dysregulation of these genes in depressed suicide completers could be influenced by miRNA post-transcriptional regulation. Using a stringent target prediction analysis, we identified several miRNAs that target the 3'UTR of SAT1 and SMOX. We profiled the expression of 10 miRNAs in the prefrontal cortex (BA44) of suicide completers (N=15) and controls (N=16) using qRT-PCR. We found that several miRNAs showed significant up-regulation in the prefrontal cortex of suicide completers compared to psychiatric healthy controls. Furthermore, we demonstrated a significant correlation between these miRNAs and the expression levels of both SAT1 and SMOX. Our results suggest a relationship between miRNAs and polyamine gene expression in the suicide brain, and postulate a mechanism for SAT1 and SMOX down-regulation by post-transcriptional activity of miRNAs.

The Neuroepigenetics of Suicide

The Neuroepigenetics of Suicide

Genome-Wide Methylation Changes in the Brains of Suicide Completers

Gene expression changes have been reported in the brains of suicide completers. More recently, differences in promoter DNA methylation between suicide completers and comparison subjects in specific genes have been associated with these changes in gene expression patterns, implicating DNA methylation alterations as a plausible component of the pathophysiology of suicide. The authors used a genome-wide approach to investigate the extent of DNA methylation alterations in the brains of suicide completers. Promoter DNA methylation was profiled using methylated DNA immunoprecipitation (MeDIP) followed by microarray hybridization in hippocampal tissue from 62 men (46 suicide completers and 16 comparison subjects). The correlation between promoter methylation and expression was investigated by comparing the MeDIP data with gene expression profiles generated through mRNA microarray. Methylation differences between groups were validated on neuronal and nonneuronal DNA fractions isolated by fluorescence-assisted cell sorting. The authors identified 366 promoters that were differentially methylated in suicide completers relative to comparison subjects (273 hypermethylated and 93 hypomethylated). Overall, promoter methylation differences were inversely correlated with gene expression differences. Functional annotation analyses revealed an enrichment of differential methylation in the promoters of genes involved, among other functions, in cognitive processes. Validation was performed on the top genes from this category, and these differences were found to occur mainly in the neuronal cell fraction. These results suggest broad reprogramming of promoter DNA methylation patterns in the hippocampus of suicide completers. This may help explain gene expression alterations associated with suicide and possibly behavioral changes increasing suicide risk.

Effects of histone modifications on increased expression of polyamine biosynthetic genes in suicide

Altered polyamine metabolism has been consistently observed as underlying the suicide process. We recently performed a global analysis of polyamine gene expression across the brains of suicide completers, and identified up-regulation of four genes, arginase II (ARG2), S-adenosylmethionine decarboxylase (AMD1), and antizymes 1 and 2 (OAZ1 and OAZ2), which play essential roles in polyamine biosynthesis. To determine if a shared epigenetic mechanism is involved in their overexpression in the prefrontal cortex, we measured promoter levels of tri-methyl modified histone-3-lysine-4 (H3K4me3), a marker of open chromatin, and assessed its association with suicide and gene expression. We identified increased H3K4me3 in the promoter region of OAZ1 in suicide, and found that H3K4me3 was correlated with the expression of OAZ1 and ARG2. Overall, our findings indicate that the H3K4me3 modification plays an important role in the regulation of polyamine biosynthesis, and that this mechanism may be involved in the neurobiology of suicide.

Global gene expression profiling of the polyamine system in suicide completers

In recent years, gene expression, genetic association, and metabolic studies have implicated the polyamine system in psychiatric conditions, including suicide. Given the extensive regulation of genes involved in polyamine metabolism, as well as their interconnections with the metabolism of other amino acids, we were interested in further investigating the expression of polyamine-related genes across the brain in order to obtain a more comprehensive view of the dysregulation of this system in suicide. To this end, we examined the expression of genes related to polyamine metabolism across 22 brain regions in a sample of 29 mood-disordered suicide completers and 16 controls, and identified 14 genes displaying differential expression. Among these, altered expression of spermidine/spermine N1-acetyltransferase, spermine oxidase, and spermine synthase, has previously been observed in brains of suicide completers, while the remainder of the genes represent novel findings. In addition to genes with direct involvement in polyamine metabolism, including S-adenosylmethionine decarboxylase, ornithine decarboxylase antizymes 1 and 2, and arginase II, we identified altered expression of several more distally related genes, including aldehyde dehydrogenase 3 family, member A2, brain creatine kinase, mitochondrial creatine kinase 1, glycine amidinotransferase, glutamic-oxaloacetic transaminase 1, and arginyl-tRNA synthetase-like. Many of these genes displayed altered expression across several brain regions, strongly implying that dysregulated polyamine metabolism is a widespread phenomenon in the brains of suicide completers. This study provides a broader view of the nature and extent of the dysregulation of the polyamine system in suicide, and highlights the importance of this system in the neurobiology of suicide.

Epigenetic regulation of spermidine/spermine N 1-acetyltransferase (SAT1) in Suicide

We have recently shown that the expression of spermidine/spermine N1-acetyltransferase (SAT1) is downregulated across the brains of suicide completers, and that its expression is influenced by genetic variations in the promoter. Several promoter polymorphisms in SAT1, including rs6526342, have been associated with suicide and other psychiatric disorders, and display haplotype-specific effects on expression. However, these effects cannot explain total variability in SAT1 expression, and other regulatory mechanisms, such as epigenetic factors, may also be at play. In this study, we assessed the involvement of epigenetic factors in controlling SAT1 expression in the prefrontal cortex of suicide completers by mapping CpG methylation across a 1880-bp region of the SAT1 promoter, and measuring levels of tri-methylated histone-3-lysine 27 (H3K27me3) at the promoter in suicide completers and controls. Our results demonstrated that CpG methylation was significantly negatively correlated with SAT1 expression. Although overall or site-specific CpG methylation was not associated with suicide or SAT1 expression, we observed high levels of methylation at the polymorphic CpG site created by rs6526342, indicating a relationship between promoter haplotypes and methylation. There was no association between H3K27me3 and suicide, nor was this modification associated with SAT1 expression. Overall, our results indicate that epigenetic factors in the promoter region of SAT1 influence gene expression levels, and may provide a mechanism for both our previous findings of haplotype-specific effects of promoter variations on SAT1 expression, as well as the widespread downregulation of SAT1 expression observed in the brains of suicide completers.

Parent of origin effect and allelic expression imbalance of the serotonin transporter in bipolar disorder and suicidal behaviour

Suicide and suicidal behaviour are a major health concern worldwide particularly in patients with mood disorders. Family, adoption and twin studies show that genetics influences suicidal behaviour. The serotonin transporter (5HTT) plays an important role in the pathophysiology of mood disorders and may also be involved in suicidal behaviour since 5HTT binding is decreased in the brain of suicide completers. Because the effect of genomic imprinting in the 5HTT gene on suicidal behaviour has not been investigated, we analysed the parent-of-origin effect (POE) of four 5HTT markers and the differential expression of the 5HTT G2651T (rs1042173) alleles in suicide attempters affected by bipolar disorder. We performed a family based association study and ETDT/QTDT analyses of the rs25531, HTTLPR, VNTR-2 and G2651T polymorphisms in 312 nuclear families with at least one subject affected by bipolar disorder. The main outcomes investigated in this study are bipolar disorder diagnosis, suicide attempts, suicidal behaviour severity and age at onset of bipolar disorder. We also compared the allele-specific mRNA levels in lymphoblastoid cells from 13 bipolar suicide attempters and 8 bipolar non-suicide attempters. Allele 2651T was transmitted significantly more often to bipolar patients (P=0.042). There was no significant difference between maternal and paternal transmission ratios. Furthermore, there was no significant difference in the ratio of T/G-specific mRNA expression between bipolar attempters and non-attempters. These data do not support a role for differential allelic expression of 5HTT for suicidal behaviour in bipolar disorder. Small sample size and the fact that RNA was obtained from lymphoblastoid cell lines were some of the limitations of this study.

Genetic and epigenetic influences on expression of spermine synthase and spermine oxidase in suicide completers

Alterations in the levels of spermine synthase (SMS) and spermine oxidase (SMOX), two enzymes involved in polyamine metabolism, have previously been observed in brains of suicide completers. To characterize the roles played by genetic and epigenetic factors in determining expression levels of these genes, as well as to identify potential mechanisms by which to explain our findings in suicide completers, we (1) assessed the role of promoter polymorphisms in determining expression in the brain and in vitro, and (2) examined CpG methylation and levels of methylated histone H3 lysine-27 in the promoter regions of these genes in the prefrontal cortex of suicide completers and healthy controls. We identified several promoter haplotypes in SMS and SMOX, but found no consistent effects of haplotype on expression levels in either the brain or in reporter gene assays performed in three different cell lines. We also found no overall effects of epigenetic factors in determining expression, with the exception of a relationship between CpG methylation at one site in the promoter of SMOX and its expression in Brodmann area 8/9. In conclusion, the genetic and epigenetic factors examined in this study show little influence on the expression levels of SMS and SMOX, and do not appear to be responsible for the dysregulated expression of these genes in suicide completers.

Association of the SAT1 in/del polymorphism with suicide completion

Several studies have observed decreased expression of spermidine/spermine N1-acetyltransferase (SAT1) in the brains of suicide completers, and we previously identified a single-nucleotide polymorphism in the promoter region of SAT1 which was associated with suicide completion and SAT1 expression in the brain. We recently characterized the haplotype structure of the SAT1 promoter region and identified an insertion/deletion (in/del) of 15 adenine residues. This variant appears to be a predictor of SAT1 expression, and we were thus interested in determining if the lower expressing deletion allele was found more frequently among suicide completers. To this end, we genotyped the in/del in a sample of 771 French-Canadian males, comprising 326 suicide completers and 445 non-suicide controls. We found no significant difference in the frequencies of the two alleles between suicide completers and controls in the entire sample. However, we observed a significantly higher frequency of the deletion in the depressed suicide completers compared to the depressed non-suicides. These results add support for a role of SAT1 in conferring a risk for suicide completion, in particular in the context of depressive disorders.

Genetic and epigenetic analysis of SSAT gene dysregulation in suicidal behavior

It has recently been proposed that the SSAT gene plays a role in the predisposition to suicidal behavior. SSAT expression was found to be down-regulated in the brain of suicide completers. In addition, a single nucleotide polymorphism (SNP) rs6526342 was associated both with variation in SSAT expression and with suicidal behavior. In this study, we aimed to characterize the relationship between SSAT dysregulation and suicide behavior. To this end, we measured SSAT expression levels in the ventral prefrontal cortex (VPFC) of suicide completers (n = 20) and controls (n = 20) and found them to be significantly down-regulated in suicide victims (P = 0.007). To identify the basis of the regulation of SSAT expression, we performed an association analysis of 309 SNPs with SSAT transcript levels in 53 lymphoblastoid cell lines from the CEPH collection. We then examined the methylation status of the SSAT promoter region in males and females suicide completers and control subjects whose SSAT brain expression had been measured. We found no evidence to support a role for SNPs in controlling the level of SSAT expression. SSAT promoter methylation levels were not different between suicide completers and controls and did not correlate with SSAT expression levels. In addition, we found no indication of a genetic association between suicidal behavior and SNPs located within the SSAT gene. Our study provides new results which show that dysregulation of SSAT expression does play a role in suicide behavior. However, our data do not support any association between rs6526342 and variation in SSAT expression or suicidal behavior.

Cholesterol content in brains of suicide completers

An association between low levels of serum cholesterol and violent or suicidal behaviour has frequently been reported, but it remains unclear how cholesterol in the peripheral system might be related to the brain functions involved in mediating suicidal behaviour. To our knowledge, there have been no previous studies aimed at answering the important question of whether there are differences in cholesterol within the brains of suicide completers. In the present study, cholesterol content was measured in cortical and subcortical tissue of brains from 41 male suicide completers and 21 male controls that died of sudden causes with no direct influence on brain tissue. No significant differences in cholesterol content were found between suicides and controls in the frontal cortex, amygdala or hippocampus. However, when the suicide completers were stratified into violent (n=31) or non-violent (n=10) groups based on the method of death, violent suicides were found to have lower grey-matter cholesterol content overall compared to non-violent suicides [F(1,111)=4.75, p=0.03], specifically in the frontal cortex (t=-4.16, d.f.=37, p<0.0005). Further exploration of the frontal cortex revealed that violent suicides had lower cholesterol content compared to non-violent suicides in the orbitofrontal cortex (t=-2.01, d.f.=36, p=0.05) and the ventral prefrontal cortex (t=-2.49, d.f.=37, p=0.02). This study represents the first direct examination of cholesterol content in brain tissue from suicide completers, and the present findings provide added support for the relationship between low cholesterol and violent or suicidal behaviour.

Data Back Relationship Between Serotonin Binding, Suicide Attempts

Back to table of contents Previous article Next article Clinical & Research NewsFull AccessData Back Relationship Between Serotonin Binding, Suicide AttemptsJoan Arehart-TreichelJoan Arehart-TreichelSearch for more papers by this authorPublished Online:20 Jun 2003https://doi.org/10.1176/pn.38.12.0026aDo serotonin abnormalities in the brain underlie suicidal thoughts and behavior? Postmortem evidence from the brains of suicide completers indicates yes. So has cerebrospinal fluid evidence from suicide attempters. And now evidence from the brains of a handful of suicide attempters indicates yes as well.Kees van Heeringen, M.D., Ph.D., chair of psychiatry at the University Hospital Gent in Belgium, and his coworkers have found that serotonin receptors in the prefrontal cortex of nine suicide attempters did not bind as well as did serotonin receptors in the prefrontal cortex of 13 control subjects. They reported their finding in the April Journal of Affective Disorders.“These results compliment our findings,” Maria Oquendo, M.D., an associate professor of clinical psychiatry at Columbia University, told Psychiatric News. In the January Archives of General Psychiatry, Oquendo and her team reported that they had found less serotonergic response to a chemical challenge in the prefrontal cortexes of 16 very suicidal depressed subjects than in the prefrontal cortexes of nine less suicidal depressed subjects.Still another strength of the study, Oquendo pointed out, is that the researchers focused on those serotonin receptors that have been found to be involved in suicide completion—the 5-HT2a receptors. The study also links poor 5-HT2a binding with hopelessness—a well-documented risk factor for suicide.The suicidal subjects whom van Heeringen and his colleagues selected for their study were persons who had been admitted to the University Hospital Gent Department of Psychiatry following a suicide attempt. Seven were male, two female. For at least six months before the study, all were free of psychotropic drugs, except for benzodiazepines, barbiturates, or anti-epileptic drugs that were ingested during the suicide attempt. None were substance abusers. Control subjects consisted of seven males and six females who were recruited from the hospital staff and screened for personal and familial psychiatric histories as well as medical histories. None used psychotropic medications or abused substances.The suicidal subjects were assigned a psychiatric diagnosis according to DSM-IV criteria. Four were diagnosed with major depressive disorder, two with narcissistic personality disorder, one with borderline personality disorder, one with dependent personality disorder, and one with brief psychotic disorder. Then both suicidal subjects and control subjects were assessed for personality characteristics using a Dutch version of Cloninger’s 240-item Temperament and Character Inventory and for hopelessness according to Beck’s Hopelessness Scale. After that, a radioactively labeled chemical that binds selectively to 5-HT2a receptors and brain imaging were used to visualize 5-HT2a receptor binding in all the subjects’ frontal cortexes.The researchers then compared serotonin receptor binding in the suicide attempters with that in the controls. They found that the suicide attempters had a significantly lower binding potential of 5-HT2a receptors in the prefrontal cortex than had the control subjects, especially in the dorsolateral area of the prefrontal cortex, which is involved in anticipation and planning.The investigators then looked to see whether they could identify any personality traits that characterized the suicide attempters compared with the controls. The suicidal subjects scored significantly higher on harm avoidance and hopelessness and significantly lower on self-directedness and cooperativeness than had the controls.Finally, the scientists attempted to see whether they could make any statistically significant connections between the low serotonin-binding potential in the prefrontal cortexes of the suicidal subjects and particular personality characteristics that the subjects possessed. A significant link was found between harm avoidance and binding potential and also between hopelessness and binding potential.Thus, “lower central serotonergic function, hopelessness, and harm avoidance are interrelated phenomena, which may increase the probability of the occurrence of attempted suicide,” van Heeringen and his team concluded.The results, van Heeringen told Psychiatric News, also imply that drugs that enhance serotonin activity in the brain might possibly “prevent the occurrence of suicidal behavior through their effect on hopelessness and anxiety regulation.”In fact, Oquendo and her coworkers are exploring the possible value of the SSRIs, as well as of some other medications, in preventing suicidal behavior (Psychiatric News, October 18, 2002).The study by van Heeringen and his colleagues was financed by the Fund for Scientific Research–Flanders.An abstract of the study, “Prefrontal 5-HT2a Receptor Binding Index, Hopelessness, and Personality Characteristics in Attempted Suicide,” can be accessed on the Web at www.sciencedirect.com by clicking on “Browse A-Z of journals,” then “j,” then Journal of Anxiety Disorders. ▪ ISSUES NewArchived

Serotonin and Suicidal Behaviora

Studies of the brain of suicide victims indicate there is a decrease in brain stem levels of 5-HT and/or 5-HIAA. There also appears to be a region-specific increase in 5-HT2 receptors, which are post synaptic and may therefore be increased in number secondary to decreased serotonin levels. Lack of information about how 5-HT2 and other serotonin receptor populations are regulated hamper our ability to explain the mechanisms underlying these findings. If the initial reports of a decrease in the number of imipramine binding sites prove to be correct then this finding would be further evidence for an effect involving the serotonin neurons, seen in this case at the level of the terminals. The relationship between suicide attempters and completers remains to be worked out. However, studies of suicide attempters, particularly those making more lethal attempts, appear to confirm the findings made in the brain of suicide completers. Neuroendocrine and CSF studies indicate the presence of serotonin subresponsivity and lower levels of CSF 5-HIAA. Thus, the overall direction of change is towards a weaker serotonin signal which rather than being due to a primary receptor defect (a possibility that cannot be ruled out but for which there is no current evidence), appears to be due to reduced levels of serotonin release. The causes of this effect represent a research challenge. It is clear that reduced levels of serotonin alone cannot explain the timing and type of suicidal behavior. Future studies must address the role of other neurotransmitters which may explain why some aggression is directed outward (towards other people) and in other cases the aggression is directed toward the self (suicidal behavior). Defining the role of serotonin and other involved transmitter systems is a necessary step before a comprehensive pharmacological treatment plan can be designed and tested.