Suicide, stress and serotonin receptor 1A promoter polymorphism -1019C>G in Slovenian suicide victims.

Implication of serotonergic system in suicide and suicide attempts has been discussed for several years. One of the most abundant serotonin receptors in the mammalian brain is the receptor 1A (5-HT1A); studies of its polymorphisms and suicide have provided very inconsistent results so far. The suggestion that the G allele depresses HTR1A autoreceptor expression, and therefore reduces serotonergic neurotransmission that might predispose to depression and suicide, made the promoter polymorphism -1019C>G a very promising candidate gene. In our study we analyzed promoter polymorphism -1019C>G on 323 suicide victims and 190 controls (all of Slovenian origin), taking into account sex, suicide method, and in case of suicide victims also stressful life events. Differences in the distributions of genotype and allele frequencies were not statistically significant between suicide victims and control group, and the same was found for distributions according to sex and suicide method. For 62 suicide victims information about stressful life events in the month prior to the suicide and in childhood was provided. For analysis we combined CG/GG genotypes and compared them to the CC genotype. More stressful life events in the month prior to the suicide were reported for the subgroup with CC genotype (mean number of events = 2.53; SD = 1.50) in comparison to subgroup with CG/GG genotypes (mean number of events = 1.58; SD = 1.32; P < 0.05). However, subgroups of suicide victims with CC or CG/GG genotypes did not differ regarding numbers of reported stressful life events in childhood (P > 0.05). Our study provides no evidence for the implication of HTR1A promoter polymorphism in suicide in general, but it suggests further studies that would take into account the interconnected network of suicide completion, genetic background and stress, beside other risk factors.

Suicide risk: where, why and how is it generated?

In this editorial we will first use the findings of epidemiological research to show that the closer we get to brain dysfunction, the higher is the suicide risk (Where?). Secondly, a distinction will be made between the proximate and ultimate causation of suicide behaviour as a biological phenomenon (Why?). Using the evolutionary psychiatry approach, the ultimate causation of suicide could answer the question why does suicidal behaviour exist at all? Third, we will review the most attractive recent molecular genetic findings in the field of suicidology genetics (How?). These three perspectives will in turn lead us to summarise where, why and how suicide risk is generated?

Case report on the analysis of single nucleotide polymorphisms of the serotonergic pathway and array-based comparative genomic hybridisation of a suicide victim.

Slovenia, with its population of 2 million, has one of the highest suicide rates in Europe (around 30 per 100,000). It has been determined by twin studies that up to 45% of the variance in suicidal ideation and behaviour may be attributable to genetic variables. In the present paper we report on a case of a male suicide victim. Before the psychological autopsy was performed we genotyped this person for 15 genetic polymorphisms of the serotonergic pathway, since molecular-genetic studies of neurotransmitters from brain and blood samples of suicide victims have shown that the serotonergic system might be implicated in suicide. This case report evaluated by psychological autopsy and serotoninergic gene polymorphisms determination indicates the influence of genetic and environmental factors contributing to the suicidal behaviour of the individual person. Probably the interplay between genes and stressful events jut before suicide, together with mental disorder lead to suicide in the case described.

Serotonin transporter gene promoter (5-HTTLPR) and intron 2 (VNTR) polymorphisms: a study on Slovenian population of suicide victims.

Several studies have been carried out to investigate how genetic variants of gene encoding for the serotonin transporter (5-HTT) may confer susceptibility to suicide. It was demonstrated that polymorphisms in the promoter region (5-HTTLPR) and in the second intron (VNTR) have functional consequences and are for this reason of particular interest in relation to various psychiatric disorders. In our study, we analyzed 5-HTTLPR and VNTR polymorphisms in 235 suicide victims and 233 controls in a Slovenian population to find a possible association of the polymorphisms and suicidal behavior. No statistically important differences between genotypes of controls and suicide group (5-HTTLPR: Pearson's chi2=1.597, df=2, P=0.455; VNTR: Pearson's chi=1.961, df=4, P=0.744), as well as no differences in allele distribution (5-HTTLPR: Pearson's chi2=0.598, df=1, P=0.467; VNTR: Pearson's chi2=0.837, df=2, P=0.654) were found, although a slightly higher frequency of LL genotype and of L allele was observed in the suicide group. Haplotype frequency analysis showed no excess of particular haplotypes between the two groups. Our study showed no association of serotonin transporter polymorphisms and suicide. The study, however, was performed on a population with a very high suicide rate (27.1 victims/100,000 citizens) and the role of 5-HTTLPR polymorphisms may be different in other populations.

TrkB gene expression and DNA methylation state in Wernicke area does not associate with suicidal behavior.

BACKGROUND: Alterations of DNA methylation and expression of suicide-related genes occurring in specific brain's areas have been associated to suicidal behavior. In the BDNF pathway, TrkB gene in frontal cortex and hippocampus, and BDNF gene in Wernicke area have been found hypermethylated and down-regulated in suicide subjects as compared to controls. In this work we investigated whether epigenetic modifications of TrkB gene occur in Wernicke area of 18 suicide subjects as compared to 18 controls. METHODS: MassArray analysis was performed to determine the methylation degree of TrkB promoter in post-mortem samples. TrkB full length and TrkB-T1 mRNA levels were assessed by quantitative RT-PCR. Geometric averaging of four internal control genes was calculated for normalization of results. RESULTS: We found that TrkB and TrkB-T1 expression and promoter methylation in Wernicke area did not correlate with suicidal behavior whereas, in the same samples, the BDNF promoter IV was significantly hypermethylated in suicide with respect of controls. LIMITATION: Data from a single brain's area in this study's sample. CONCLUSIONS: Our data show that no correlation exists between TrkB gene methylation and suicide in Wernicke area, confirming that expression and methylation state of suicide-related genes, even belonging to the same pathway, may be specific for brain area.

Increased BDNF promoter methylation in the Wernicke area of suicide subjects.

CONTEXT: Brain-derived neurotrophic factor (BDNF) plays a pivotal role in the pathophysiology of suicidal behavior and BDNF levels are decreased in the brain and plasma of suicide subjects. So far, the mechanisms leading to downregulation of BDNF expression are poorly understood. OBJECTIVES: To test the hypothesis that alterations of DNA methylation could be involved in the dysregulation of BDNF gene expression in the brain of suicide subjects. DESIGN: Three independent quantitative methylation techniques were performed on postmortem samples of brain tissue. BDNF messenger RNA levels were determined by quantitative real-time polymerase chain reaction. SETTING: Academic medical center. PATIENTS OR OTHER PARTICIPANTS: Forty-four suicide completers and 33 nonsuicide control subjects of white ethnicity. MAIN OUTCOME MEASURES: The DNA methylation degree at BDNF promoter IV and the genome-wide DNA methylation levels in the brain's Wernicke area. RESULTS: Postmortem brain samples from suicide subjects showed a statistically significant increase of DNA methylation at specific CpG sites in BDNF promoter/exon IV compared with nonsuicide control subjects (P < .001). Most of the CpG sites lying in the -300/+500 region, on both strands, had low or no methylation, with the exception of a few sites located near the transcriptional start site that had differential methylation, while genome-wide methylation levels were comparable among the subjects. The mean methylation degree at the 4 CpG sites analyzed by pyrosequencing was always less than 12.9% in the 33 nonsuicide control subjects, while in 13 of 44 suicide victims (30%), the mean methylation degree ranged between 13.1% and 34.2%. Higher methylation degree corresponded to lower BDNF messenger RNA levels. CONCLUSIONS: BDNF promoter/exon IV is frequently hypermethylated in the Wernicke area of the postmortem brain of suicide subjects irrespective of genome-wide methylation levels, indicating that a gene-specific increase in DNA methylation could cause or contribute to the downregulation of BDNF expression in suicide subjects. The reported data reveal a novel link between epigenetic alteration in the brain and suicidal behavior.

Selected summaries from the XVII World Congress of Psychiatric Genetics, San Diego, California, USA, 4-8 November 2009.

The XVII World Congress of Psychiatric Genetics, sponsored by The International Society of Psychiatric Genetics (ISPG) took place in San Diego, California from 4 to 8 November 2009. Approximately 550 participants gathered to discuss the latest molecular genetic findings relevant to serious mental illness, including schizophrenia, mood disorders, substance abuse, autism, and attention deficit disorder. Recent advances in the field were discussed, including the genome-wide association studies results, copy number variation (CNV) in the genome, genomic imaging, and large multicenter collaborations. The following report, written by junior travel awardees who were assigned sessions as rapporteurs represents some of the areas covered in oral presentation during the conference, and reports on some of the notable major new findings described at this 2009 World Congress of Psychiatric Genetics.

Promoter and functional polymorphisms of HTR2C and suicide victims.

In Europe, the countries with the highest suicide rates form a so-called J-curve, which starts in Finland and extends down to Slovenia-a country with one of the world's highest suicide rates. So far, the strongest association between suicide and genes has been shown for the serotonergic system. A functional polymorphism 68G>C (Cys23Ser) and a promoter polymorphism-995G>A of serotonin receptor 2C (HTR2C) have already been investigated, but no associations with suicide were determined. In the present study 334 suicide victims and 211 controls of Slovenian origin were genotyped for the above-mentioned polymorphisms using standard methods. In the case of the polymorphism-995G>A no association with suicide was found. However, a significant association was observed between female suicide victims and polymorphism 68G>C. The significance remained when we combined alleles of female and male populations. An excess of GG genotype and allele G was observed. However, no statistically important differences were present when only males were analyzed. Haplotype analysis on female population showed marginal association of haplotype G-C with suicide. The present study speaks for the plausible implication of the HTR2C in suicide susceptibility.

Selected summaries from the XVI World Congress of Psychiatric Genetics, Osaka, Japan, 11-15 October 2008.

The XVI World Congress of Psychiatric Genetics, sponsored by the International Society of Psychiatric Genetics took place in Osaka, Japan, October 2008. Approximately 600 participants gathered to discuss the latest molecular genetic findings relevant to serious mental illnesses, including schizophrenia, bipolar disorder, major depression, alcohol and drug abuse, autism, and attention-deficit disorder. Recently, the field has advanced considerably and includes new genome-wide association studies with the largest numbers of individuals screened and density of markers to date, as well as newly uncovered genetic phenomena, such as copy number variation that may prove to be relevant for specific brain disorders. The following report represents some of the areas covered during this conference and some of the major new findings presented.

Association study of seven polymorphisms in four serotonin receptor genes on suicide victims.

A number of molecular genetic studies have investigated if serotonin (5-HT) receptor subtypes are involved in the pathogenesis of depression, suicidal behavior, aggression, and impulsive behavior. Existence of many receptor subtypes for a single transmitter permits a great diversity of signaling raising the possibility that they may serve as genetic markers for suicidal behavior. Most previous studies of suicide have analyzed polymorphisms of the receptors 5-HT1A, 5-HT1B, 5-HT2A, fewer have examined 5-HT1F. We report a study of possible association between the polymorphisms in the 5-HT receptor genes (1A, 1B, 1F, and 2A) and suicidal behavior on a sample of 226 suicide victims and 225 healthy control subjects. No significant differences in genotype frequency distributions between the suicide victims and healthy control subjects were observed for four polymorphisms; three were not polymorphic. A single polymorphism, C-1420T in gene 5-HT2A, showed a slight association with suicide (chi2= 4.94, df = 2, P = 0.067), but the correlation was not statistically significant. None of the tested genetic variants of serotonin receptors appears to be associated with suicidal behavior in the Slovenian population which has a relatively high suicide rate.