Association of RGS2 gene polymorphisms with suicide and increased RGS2 immunoreactivity in the postmortem brain of suicide victims

Comparative Transcriptional Analyses in the Nucleus Accumbens Identifies RGS2 as a Key Mediator of Depression-Related Behavior

BACKGROUND

Major depressive disorder is one of the most commonly diagnosed mental illnesses worldwide, with a higher prevalence in women than in men. Although currently available pharmacological therapeutics help many individuals, they are not effective for most. Animal models have been important for the discovery of molecular alterations in stress and depression, but difficulties in adapting animal models of depression for females has impeded progress in developing novel therapeutic treatments that may be more efficacious for women.

METHODS

Using the California mouse social defeat model, we took a multidisciplinary approach to identify stress-sensitive molecular targets that have translational relevance for women. We determined the impact of stress on transcriptional profiles in male and female California mouse nucleus accumbens (NAc) and compared these results with data from postmortem samples of the NAc from men and women diagnosed with major depressive disorder.

RESULTS

Our cross-species computational analyses identified Rgs2 (regulator of G protein signaling 2) as a transcript downregulated by social defeat stress in female California mice and in women with major depressive disorder. RGS2 plays a key role in signal regulation of neuropeptide and neurotransmitter receptors. Viral vector-mediated overexpression of Rgs2 in the NAc restored social approach and sucrose preference in stressed female California mice.

CONCLUSIONS

These studies show that Rgs2 acting in the NAc has functional properties that translate to changes in anxiety- and depression-related behavior. Future studies should investigate whether targeting Rgs2 represents a novel target for treatment-resistant depression in women.

Attenuation of nicotine-induced rewarding and antidepressant-like effects in male and female mice lacking regulator of G-protein signaling 2

Nicotine-induced rewarding and mood altering effects contribute to the continued use of nicotine and the subsequent development of nicotine dependence. The goal of this study was to assess the role of two specific regulators of G-protein signaling (RGS) proteins namely RGS2 and RGS4 in the above described effects of nicotine. Male and female mice lacking either RGS2 (RGS2 KO) or RGS4 (RGS4 KO), and their respective wildtype (WT) littermates were used in this study. The rewarding effects of nicotine (0.5 mg/kg, base; s.c.) were assessed using the conditioned place preference model. Nicotine-induced anxiolytic-like (0.1 mg/kg, base; i.p.) and antidepressant-like (1 mg/kg, base; i.p.) effects were assessed using the elevated plus maze and tail suspension test, respectively. We also assessed effects of nicotine (0, 0.05, 0.1 & 0.5 mg/kg, base; s.c.) on spontaneous locomotor activity. Nicotine-induced rewarding and antidepressant-like effects were observed in both male and female RGS2 WT mice, but not in mice lacking RGS2 compared to respective controls. In contrast, nicotine-induced rewarding and antidepressant-like effects were observed in both male and female mice lacking RGS4 and their WT littermates. Interestingly, deletion of RGS4 facilitated antidepressant-like effect of nicotine in male, but not female mice compared to respective WT littermates. Nicotine-induced anxiolytic-like effect was not influenced by deletion of either RGS2 or RGS4, irrespective of sex. Nicotine (0.5 mg/kg) decreased locomotor activity in both WT and KO mice compared to respective saline, irrespective of genotype and sex. Taken together, these data provide evidence that RGS2, but not RGS4, plays a role in mediating the rewarding and antidepressant-like effects of nicotine. Further research is required to explore the role of RGS2 after chronic exposure to nicotine.

Targeting the renin angiotensin system for the treatment of anxiety and depression

Emotional disorders like anxiety and depression are responsible for considerable morbidity and mortality all over the world. Several antidepressant and anxiolytic medications are available for the treatment of anxiety and depression. However, a significant number of patients either do not respond to these medications or respond inadequately. Hence, there is a need to identify novel targets for the treatment of anxiety and depression. In this review we focus on the renin angiotensin system (RAS) as a potential target for the treatment of these disorders. We review work that has evaluated the effects of various compounds targeting the RAS on anxiety- and depression-like behaviors. Further, we suggest future work that must be carried out to fully exploit the RAS for the treatment of anxiety and depression. The RAS provides an attractive target for both the identification of novel anxiolytic and antidepressant medications and/or for enhancing the efficacy of currently available medications used for the treatment of anxiety and depression.

Genetic Analysis of Rare Human Variants of Regulators of G Protein Signaling Proteins and Their Role in Human Physiology and Disease

Regulators of G protein signaling (RGS) proteins modulate the physiologic actions of many neurotransmitters, hormones, and other signaling molecules. Human RGS proteins comprise a family of 20 canonical proteins that bind directly to G protein-coupled receptors/G protein complexes to limit the lifetime of their signaling events, which regulate all aspects of cell and organ physiology. Genetic variations account for diverse human traits and individual predispositions to disease. RGS proteins contribute to many complex polygenic human traits and pathologies such as hypertension, atherosclerosis, schizophrenia, depression, addiction, cancers, and many others. Recent analysis indicates that most human diseases are due to extremely rare genetic variants. In this study, we summarize physiologic roles for RGS proteins and links to human diseases/traits and report rare variants found within each human RGS protein exome sequence derived from global population studies. Each RGS sequence is analyzed using recently described bioinformatics and proteomic tools for measures of missense tolerance ratio paired with combined annotation-dependent depletion scores, and protein post-translational modification (PTM) alignment cluster analysis. We highlight selected variants within the well-studied RGS domain that likely disrupt RGS protein functions and provide comprehensive variant and PTM data for each RGS protein for future study. We propose that rare variants in functionally sensitive regions of RGS proteins confer profound change-of-function phenotypes that may contribute, in newly appreciated ways, to complex human diseases and/or traits. This information provides investigators with a valuable database to explore variation in RGS protein function, and for targeting RGS proteins as future therapeutic targets.

The Role of G-proteins and G-protein Regulating Proteins in Depressive Disorders

Progress toward new antidepressant therapies has been relatively slow over the past few decades, with the result that individuals suffering from depression often struggle to find an effective treatment – a process often requiring months. Furthermore, the neural factors that contribute to depression remain poorly understood, and there are many open questions regarding the mechanism of action of existing antidepressants. A better understanding of the molecular processes that underlie depression and contribute to antidepressant efficacy is therefore badly needed. In this review we highlight research investigating the role of G-proteins and the regulators of G-protein signaling (RGS) proteins, two protein families that are intimately involved in both the genesis of depressive states and the action of antidepressant drugs. Many antidepressants are known to indirectly affect the function of these proteins. Conversely, dysfunction of the G-protein and RGS systems can affect antidepressant efficacy. However, a great deal remains unknown about how these proteins interact with antidepressants. Findings pertinent to each individual G-protein and RGS protein are summarized from in vitro, in vivo, and clinical studies.

Interplay between RGS2 and childhood adversities in predicting anxiety and depressive disorders: Findings from a general population sample

BACKGROUND

It remains unresolved whether childhood adversities interact with genetic variation in regulator of G-protein signaling 2 (RGS2) rs4606 in predicting various anxiety and depressive disorders and whether diagnostic specificity exists in these interactions.

METHODS

The genotype of RGS2 rs4606 was determined for N = 2,263 adults with European ancestry from the Study of Health in Pomerania. Lifetime anxiety and depressive disorders according to the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, were assessed with the Munich Composite International Diagnostic Interview (DIA-X/M-CIDI). Childhood adversities were assessed with the Childhood Trauma Questionnaire (CTQ, when participants were aged 29-89).

RESULTS

Logistic regressions adjusted for sex and age revealed that rs4606 interacted with total childhood adversity in predicting each diagnostic outcome except for panic disorder and generalized anxiety disorder, uncorrected and corrected for multiple testing (odds ratio [OR] = 1.06-1.16). That is, carriers of the GG (vs. CC/CG) genotype were at decreased risk for anxiety and/or depression in the presence of low, but at increased risk in the presence of high total childhood adversity. Respective gene-environment (G × E) interactions were found for (a) comorbid anxiety and depressive disorders (OR = 1.13), but neither pure anxiety nor pure depressive disorders and (b) pure/temporally primary anxiety disorders (OR = 1.07), but not pure/temporally primary depressive disorders. The G × E interaction remained associated with depressive disorders after introducing pure/temporally primary anxiety disorders as additional predictor (OR = 1.09).

CONCLUSIONS

rs4606 alters the risk of developing a range of anxiety but also depressive disorders after childhood adversities. A complex risk pattern of genotype, environmental factors, and preexisting anxiety contributes to subsequent depression development.

Regulator of G protein signaling 2 differentially regulates nicotine-induced anxiolytic- and antidepressant-like effects in mice

This study assessed the role of regulator of G protein signaling 2 (RGS2) in nicotine-induced anxiolytic- and antidepressant-like effects using RGS2 wildtype (WT) and RGS2 knockout (KO) mice. RGS2 negatively regulates monoaminergic neurotransmission, which is implicated in the pathology of anxiety and depression. We hypothesized that deletion of RGS2 would enhance nicotine-induced anxiolytic- and antidepressant-like effects, which were assessed using the elevated plus maze and tail suspension tests, respectively. Anxiolytic-like effects were observed in both RGS2 WT and KO mice after administration of low dose of nicotine (0.05 mg/kg, base) compared to respective saline controls. Additionally, administration of nicotine (0.1 mg/kg, base) compared to saline resulted in anxiolytic-like effects in RGS2 KO mice, but not RGS2 WT mice, suggesting genetic deletion of RGS2 facilitated anxiolytic-like effects of nicotine. Administration of nicotine (0.5 and 1 mg/kg, base) compared to saline resulted in antidepressant-like effects in RGS2 WT mice. Antidepressant-like effects were observed in RGS2 KO mice only at the highest tested dose of nicotine (1 mg/kg, base) compared to saline controls, suggesting that genetic deletion of RGS2 decreased sensitivity to antidepressant-like effects of nicotine. Together, the data suggest that RGS2 differentially regulated nicotine-induced affective behavioral responses. These data suggest that individuals with RGS2 polymorphisms may experience differential affective responses to tobacco smoking, which may make them vulnerable to developing nicotine addiction.

Regulators of G-protein signaling 2 and 4 differentially regulate cocaine-induced rewarding effects

There is a need to identify new therapeutic targets for the treatment of cocaine addiction due to the rise in cocaine abuse and deaths due to cocaine overdose. Regulator of G protein signaling (RGS) proteins such as RGS2 and RGS4 are widely distributed in brain regions that play a role in drug reward. Importantly, RGS2 and RGS4 negatively regulate G-protein coupled receptor signaling pathways of monoaminergic neurotransmitters that play a role in the rewarding effects of cocaine by enhancing the rate of hydrolysis of Gα-bound guanine nucleotide triphosphate. Thus, the objective of this study was to investigate the effects of cocaine on conditioned place preference (CPP) and locomotor activity in mice that lacked either RGS2 or RGS4 (i.e. knockout (KO) mice) and their wildtype (WT) littermates. Moreover recent studies have reported influence of sex on RGS functioning and hence studies were conducted in both male and female mice. Cocaine-induced CPP was attenuated in male, but not female RGS4 KO mice compared to respective RGS4 WT mice. Cocaine-induced CPP was not influenced by deletion of RGS2 in either male or female mice. Similarly, cocaine-induced locomotor activity was not influenced by deletion of either RGS2 or RGS4 irrespective of sex. Together, the data indicate that the rewarding effects of cocaine were attenuated in the absence of RGS4 expression, but not in the absence of RGS2 expression in a sex-dependent manner. Importantly, these data suggest that RGS4 can serve as a potential target for medications that can be used to treat cocaine addiction.

A switch in G protein coupling for type 1 corticotropin-releasing factor receptors promotes excitability in epileptic brains

Anxiety and stress increase the frequency of epileptic seizures. These behavioral states induce the secretion of corticotropin-releasing factor (CRF), a 40-amino acid neuropeptide neurotransmitter that coordinates many behavioral responses to stress in the central nervous system. In the piriform cortex, which is one of the most seizurogenic regions of the brain, CRF normally dampens excitability. By contrast, CRF increased the excitability of the piriform cortex in rats subjected to kindling, a model of temporal lobe epilepsy. In nonkindled rats, CRF activates its receptor, a G protein (heterotrimeric guanosine triphosphate-binding protein)-coupled receptor, and signals through a Gαq/11-mediated pathway. After seizure induction, CRF signaling occurred through a pathway involving Gαs This change in signaling was associated with reduced abundance of regulator of G protein signaling protein type 2 (RGS2), which has been reported to inhibit Gαs-dependent signaling. RGS2 knockout mice responded to CRF in a similar manner as epileptic rats. These observations indicate that seizures produce changes in neuronal signaling that can increase seizure occurrence by converting a beneficial stress response into an epileptic trigger.

Roles for Regulator of G Protein Signaling Proteins in Synaptic Signaling and Plasticity

The regulator of G protein signaling (RGS) family of proteins serves critical roles in G protein-coupled receptor (GPCR) and heterotrimeric G protein signal transduction. RGS proteins are best understood as negative regulators of GPCR/G protein signaling. They achieve this by acting as GTPase activating proteins (GAPs) for Gα subunits and accelerating the turnoff of G protein signaling. Many RGS proteins also bind additional signaling partners that either regulate their functions or enable them to regulate other important signaling events. At neuronal synapses, GPCRs, G proteins, and RGS proteins work in coordination to regulate key aspects of neurotransmitter release, synaptic transmission, and synaptic plasticity, which are necessary for central nervous system physiology and behavior. Accumulating evidence has revealed key roles for specific RGS proteins in multiple signaling pathways at neuronal synapses, regulating both pre- and postsynaptic signaling events and synaptic plasticity. Here, we review and highlight the current knowledge of specific RGS proteins (RGS2, RGS4, RGS7, RGS9-2, and RGS14) that have been clearly demonstrated to serve critical roles in modulating synaptic signaling and plasticity throughout the brain, and we consider their potential as future therapeutic targets.

Regulator of G-protein signaling 2 repression exacerbates airway hyper-responsiveness and remodeling in asthma

G protein-coupled receptors (GPCRs) are important regulators of cell functions in asthma. We recently reported that regulator of G-protein signaling (RGS) 2, a selective modulator of Gq-coupled GPCRs, is a key regulator of airway hyper-responsiveness (AHR), the pathophysiologic hallmark of asthma. Because RGS2 protein levels in airway cells were significantly lower in patients with asthma compared with patients without asthma, we further investigated the potential pathological importance of RGS2 repression in asthma. The human RGS2 gene maps to chromosome 1q31. We first screened patients with asthma for RGS2 gene promoter single-nucleotide polymorphisms (SNPs) and found significant differences in the distribution of two RGS2 SNPs (A638G, rs2746071 and C395G, rs2746072) between patients with asthma and nonasthmatic subjects. These two SNPs are always associated with each other and have the same higher prevalence in patients with asthma (65%) as compared with nonasthmatic subjects (35%). Point mutations corresponding to these SNPs decrease RGS2 promoter activity by 44%. The importance of RGS2 down-regulation was then determined in an acute IL-13 mouse model of asthma. Intranasal administration of IL-13 in mice also decreased RGS2 expression in lungs by ∼50% and caused AHR. Although naive RGS2 knockout (KO) mice exhibit spontaneous AHR, acute IL-13 exposure further increased AHR in RGS2 KO mice. Loss of RGS2 also significantly enhanced IL-13-induced mouse airway remodeling, including peribronchial smooth muscle thickening and fibrosis, without effects on goblet cell hyperplasia or airway inflammation in mice. Thus, genetic variations and increased inflammatory cytokines can lead to RGS2 repression, which exacerbates AHR and airway remodeling in asthma.

Adenosine Receptors Differentially Regulate the Expression of Regulators of G-Protein Signalling (RGS) 2, 3 and 4 in Astrocyte-Like Cells

The “regulators of g-protein signalling” (RGS) comprise a large family of proteins that limit by virtue of their GTPase accelerating protein domain the signal transduction of G-protein coupled receptors. RGS proteins have been implicated in various neuropsychiatric diseases such as schizophrenia, drug abuse, depression and anxiety and aggressive behaviour. Since conditions associated with a large increase of adenosine in the brain such as seizures or ischemia were reported to modify the expression of some RGS proteins we hypothesized that adenosine might regulate RGS expression in neural cells. We measured the expression of RGS-2,-3, and -4 in both transformed glia cells (human U373 MG astrocytoma cells) and in primary rat astrocyte cultures stimulated with adenosine agonists. Expression of RGS-2 mRNA as well as RGS2 protein was increased up to 30-fold by adenosine agonists in astrocytes. The order of potency of agonists and the blockade by the adenosine A2B-antagonist MRS1706 indicated that this effect was largely mediated by adenosine A2B receptors. However, a smaller effect was observed due to activation of adenosine A2A receptors. In astrocytoma cells adenosine agonists elicited an increase in RGS-2 expression solely mediated by A2B receptors. Expression of RGS-3 was inhibited by adenosine agonists in both astrocytoma cells and astrocytes. However while this effect was mediated by A2B receptors in astrocytoma cells it was mediated by A2A receptors in astrocytes as assessed by the order of potency of agonists and selective blockade by the specific antagonists MRS1706 and ZM241385 respectively. RGS-4 expression was inhibited in astrocytoma cells but enhanced in astrocytes by adenosine agonists.

The RGS2 (-391, C>G) genetic variation correlates to antihypertensive drug responses in Chinese patients with essential hypertension

OBJECTIVE

Regulators of G-protein signaling protein 2 (RGS2) play an irreplaceable role in the control of normal blood pressure (BP). One RGS2 (-391, C>G) genetic variation markedly changes its mRNA expression levels. This study explored the relationship between this genetic variation and the responses to antihypertensive drugs in Chinese patients with essential hypertension.

METHODS

Genetic variations of RGS2 were successfully identified in 367 specimens using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assays. All patients were treated with conventional doses of antihypertensives after a 2-week run-in period and followed-up according to our protocol. A general linear model multivariate analysis of variance (ANOVA) was used for the data analysis.

RESULTS

A significant difference in the mean systolic BP change was observed between RGS2 (-391, C>G) CC/CG (n = 82) and GG (n = 38) genotype carriers (-13.6 vs. -19.9 mmHg, P = 0.043) who were treated with candesartan, irbesartan or imidapril at the end of 6 weeks. In addition, the patients' BP responses to α,β-adrenergic receptor blockers exhibited an age-specific association with the RGS2 (-391, C>G) genetic variation at the end of 4 weeks.

CONCLUSION

The RGS2 (-391, C>G) genetic polymorphism may serve as a biomarker to predict a patient's response to antihypertensive drug therapy, but future studies need to confirm this.

Tempol treatment reduces anxiety-like behaviors induced by multiple anxiogenic drugs in rats

We have published that pharmacological induction of oxidative stress (OS) causes anxiety-like behavior in rats. Using animal models, we also have established that psychological stress induces OS and leads to anxiety-like behaviors. All evidence points towards the causal role of OS in anxiety-like behaviors. To fully ascertain the role of OS in anxiety-like behaviors, it is reasonable to test whether the pro-anxiety effects of anxiogenic drugs caffeine or N-methyl-beta-carboline-3-carboxamide (FG-7142) can be mitigated using agents that minimize OS. In this study, osmotic pumps were either filled with antioxidant tempol or saline. The pumps were attached to the catheter leading to the brain cannula and inserted into the subcutaneous pocket in the back pocket of the rat. Continuous i.c.v. infusion of saline or tempol in the lateral ventricle of the brain (4.3 mmol/day) was maintained for 1 week. Rats were intraperitoneally injected either with saline or an anxiogenic drug one at a time. Two hours later all groups were subjected to behavioral assessments. Anxiety-like behavior tests (open-field, light-dark and elevated plus maze) suggested that tempol prevented anxiogenic drug-induced anxiety-like behavior in rats. Furthermore, anxiogenic drug-induced increase in stress examined via plasma corticosterone and increased oxidative stress levels assessed via plasma 8-isoprostane were prevented with tempol treatment. Protein carbonylation assay also suggested preventive effect of tempol in the prefrontal cortex brain region of rats. Antioxidant protein expression and pro-inflammatory cytokine levels indicate compromised antioxidant defense as well as an imbalance of inflammatory response.

An overview of the neurobiology of suicidal behaviors as one meta-system

Suicidal behaviors (SB) may be regarded as the outmost consequence of mental illnesses, or as a distinct entity per se. Regardless, the consequences of SB are very large to both society and affected individuals. The path leading to SB is clearly a complex one involving interactions between the subject's biology and environmental influences throughout life. With the aim to generate a representative and diversified overview of the different neurobiological components hypothesized or shown implicated across the entire SB field up to date by any approach, we selected and compiled a list of 212 gene symbols from the literature. An increasing number of novel gene (products) have been introduced as candidates, with half being implicated in SB in only the last 4 years. These candidates represent different neuro systems and functions and might therefore be regarded as competing or redundant explanations. We then adopted a unifying approach by treating them all as parts of the same meta-system, using bioinformatic tools. We present a network of all components connected by physical protein-protein interactions (the SB interactome). We proceeded by exploring the differences between the highly connected core (~30% of the candidate genes) and its peripheral parts, observing more functional homogeneity at the core, with multiple signal transduction pathways and actin-interacting proteins connecting a subset of receptors in nerve cell compartments as well as development/morphology phenotypes and the stress-sensitive synaptic plasticity processes of long term potentiation/depression. We suggest that SB neurobiology might also be viewed as one meta-system and perhaps be explained as intrinsic unbalances acting within the core or as imbalances arising between core and specific peripheral components.

Gene environment interaction studies in depression and suicidal behavior: An update

Increasing evidence supports the involvement of both heritable and environmental risk factors in major depression (MD) and suicidal behavior (SB). Studies investigating gene-environment interaction (G × E) may be useful for elucidating the role of biological mechanisms in the risk for mental disorders. In the present paper, we review the literature regarding the interaction between genes modulating brain functions and stressful life events in the etiology of MD and SB and discuss their potential added benefit compared to genetic studies only. Within the context of G × E investigation, thus far, only a few reliable results have been obtained, although some genes have consistently shown interactive effects with environmental risk in MD and, to a lesser extent, in SB. Further investigation is required to disentangle the direct and mediated effects that are common or specific to MD and SB. Since traditional G × E studies overall suffer from important methodological limitations, further effort is required to develop novel methodological strategies with an interdisciplinary approach.

Relationship between Rgs2 gene expression level and anxiety and depression-like behaviour in a mutant mouse model: serotonergic involvement

RGS2 is a member of a family of proteins that negatively modulate G-protein coupled receptor transmission. Variations in the RGS2 gene were found to be associated in humans with anxious and depressive phenotypes. We sought to study the relationship of Rgs2 expression level to depression and anxiety-like behavioural features, sociability and brain 5-HT1A and 5-HT1B receptor expression. We studied male mice carrying a mutation that causes lower Rgs2 gene expression, employing mice heterozygous (Het) or homozygous (Hom) for this mutation, or wild-type (WT). Mice were subjected to behavioural tests reflecting depressive-like behaviour [forced swim test (FST), novelty suppressed feeding test (NSFT)], elevated plus maze (EPM) for evaluation of anxiety levels and the three-chamber sociability test. The possible involvement of raphe nucleus 5-HT1A receptors in these behavioural features was examined by 8-OH-DPAT-induced hypothermia. Expression levels of 5-HT1A and 5-HT1B receptors in the cortex, raphe nucleus and hypothalamus were compared among mice of the different Rgs2 genotype groups. NSFT results demonstrated that Hom mice showed more depressive-like features than Rgs2 Het and WT mice. A trend for such a relationship was also suggested by the FST results. EPM and sociability test results showed Hom and Het mice to be more anxious and less sociable than WT mice. In addition Hom and Het mice were characterized by lower basal body temperature and demonstrated less 8-OH-DPAT-induced hypothermia than WT mice. Finally, Hom and Het mice had significantly lower 5-HT1A and 5-HT1B receptor expression levels in the raphe than WT mice. Our findings demonstrate a relationship between Rgs2 gene expression level and a propensity for anxious and depressive-like behaviour and reduced social interaction that may involve changes in serotonergic receptor expression.

Genomewide association scan of suicidal thoughts and behaviour in major depression

Background

Suicidal behaviour can be conceptualised as a continuum from suicidal ideation, to suicidal attempts to completed suicide. In this study we identify genes contributing to suicidal behaviour in the depression study RADIANT.

Methodology/Principal Findings

A quantitative suicidality score was composed of two items from the SCAN interview. In addition, the 251 depression cases with a history of serious suicide attempts were classified to form a discrete trait. The quantitative trait was correlated with younger onset of depression and number of episodes of depression, but not with gender. A genome-wide association study of 2,023 depression cases was performed to identify genes that may contribute to suicidal behaviour. Two Munich depression studies were used as replication cohorts to test the most strongly associated SNPs. No SNP was associated at genome-wide significance level. For the quantitative trait, evidence of association was detected at GFRA1, a receptor for the neurotrophin GDRA (p = 2e-06). For the discrete trait of suicide attempt, SNPs in KIAA1244 and RGS18 attained p-values of <5e-6. None of these SNPs showed evidence for replication in the additional cohorts tested. Candidate gene analysis provided some support for a polymorphism in NTRK2, which was previously associated with suicidality.

Conclusions/Significance

This study provides a genome-wide assessment of possible genetic contribution to suicidal behaviour in depression but indicates a genetic architecture of multiple genes with small effects. Large cohorts will be required to dissect this further.

Association study of EP1 gene polymorphisms with suicide completers in the Japanese population

BACKGROUND

Both environmental and genetic factors have been reported to be involved in suicidal behaviors. Considerable evidence indicates that impulsive aggression is one of the important risk factors that contribute to suicide. A recent study has shown that prostaglandin E2 type 1 receptor (EP1) signaling regulates impulsive-aggressive behaviors in mice under both social and environmental stresses. To test the possible involvement of the EP1 gene in suicide, we carried out an association study of EP1 gene polymorphisms with suicide completers in the Japanese population.

METHODS

We studied 5 SNPs including one SNP in exon 2 (rs3745459) and four SNPs in the potential promoter region of the EP1 gene (rs3810255, rs3810254, rs3810253 and rs10416814) in 374 healthy control and 287 completed suicide victims using standard Taqman probe genotyping assays.

RESULTS

No significant differences of the genotypic distribution, allelic frequency or haplotype distribution between controls and suicide completers were found. Gender based analysis revealed that genotypic, allelic and haplotypic distributions of rs3810255, rs3810254, rs3810253 and rs10416814 SNPs were significantly different between the female control and female suicide groups, although the differences did not withstand correction for multiple comparisons.

CONCLUSION

We could not find an association of EP1 gene with suicide in the Japanese population. Because several SNPs in the promoter region of the EP1 gene were nominally significantly associated with suicide in the female, further studies with a larger sample size and different population are needed to confirm this result.

Association of RGS2 variants with panic disorder in a Japanese population

Panic disorder (PD) is a severe and chronic psychiatric disorder with significant genetic components underlying its etiology. The gene regulator of G protein signaling 2 (RGS2) has been reported to be associated with anxiety disorders. To confirm the association of RGS2 with PD, we investigated three single nucleotide polymorphisms (SNPs) of RGS2 (rs10801152, rs4606, and rs1819741) in 677 Japanese PD cases and 460 controls. The SNP rs10801152 was suggestive of an association with PD (allele P = 0.045 adjusted using sex and age as confounding factors). The three-SNP haplotype was significantly associated with PD (global permutation P = 4 × 10(-4)). The haplotypes T-G-C and T-C-T showed significant association and protective effect on PD (T-G-C, permutation P = 0.038, OR = 0.80, 95%CI = 0.68-0.95; T-C-T, permutation P = 0.004, OR = 0.38, 95%CI = 0.21-0.70). These results provide support for an association of RGS2 with PD in a Japanese population.

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.

The interpersonal theory of suicide

Suicidal behavior is a major problem worldwide and, at the same time, has received relatively little empirical attention. This relative lack of empirical attention may be due in part to a relative absence of theory development regarding suicidal behavior. The current article presents the interpersonal theory of suicidal behavior. We propose that the most dangerous form of suicidal desire is caused by the simultaneous presence of two interpersonal constructs-thwarted belongingness and perceived burdensomeness (and hopelessness about these states)-and further that the capability to engage in suicidal behavior is separate from the desire to engage in suicidal behavior. According to the theory, the capability for suicidal behavior emerges, via habituation and opponent processes, in response to repeated exposure to physically painful and/or fear-inducing experiences. In the current article, the theory's hypotheses are more precisely delineated than in previous presentations (Joiner, 2005), with the aim of inviting scientific inquiry and potential falsification of the theory's hypotheses.

Association of genetic variants in the neurotrophic receptor-encoding gene NTRK2 and a lifetime history of suicide attempts in depressed patients

CONTEXT

A consistent body of evidence supports a role of reduced neurotrophic signaling in the pathophysiology of major depressive disorder (MDD) and suicidal behavior. Especially in suicide victims, lower postmortem brain messenger RNA and protein levels of neurotrophins and their receptors have been reported.

OBJECTIVE

To determine whether the brain-derived neurotrophic factor (BDNF) gene or its high-affinity receptor gene, receptor tyrosine kinase 2 (NTRK2), confer risk for suicide attempt (SA) and MDD by investigating common genetic variants in these loci.

DESIGN

Eighty-three tagging single-nucleotide polymorphisms (SNPs) covering the genetic variability of these loci in European populations were assessed in a case-control association design.

SETTING

Inpatients and screened control subjects.

PARTICIPANTS

The discovery sample consisted of 394 depressed patients, of whom 113 had SA, and 366 matched healthy control subjects. The replication studies comprised 744 German patients with MDD and 921 African American nonpsychiatric clinic patients, of whom 152 and 119 were positive for SA, respectively.

INTERVENTIONS

Blood or saliva samples were collected from each participant for DNA extraction and genotyping.

MAIN OUTCOME MEASURES

Associations of SNPs in BDNF and NTRK2 with SA and MDD.

RESULTS

Independent SNPs within NTRK2 were associated with SA among depressed patients of the discovery sample that could be confirmed in both the German and African American replication samples. Multilocus interaction analysis revealed that single SNP associations within this locus contribute to the risk of SA in a multiplicative and interactive fashion (P = 4.7 x 10(-7) for a 3-SNP model in the combined German sample). The effect size was 4.5 (95% confidence interval, 2.1-9.8) when patients carrying risk genotypes in all 3 markers were compared with those without any of the 3 risk genotypes.

CONCLUSIONS

Our results suggest that a combination of several independent risk alleles within the NTRK2 locus is associated with SA in depressed patients, further supporting a role of neurotrophins in the pathophysiology of suicide.

Regulators of G protein signaling in neuropsychiatric disorders

Regulators of G protein signaling (RGS) comprise a diverse group of about 40 proteins which determine signaling amplitude and duration via modulation of receptor/G protein or receptor/effector coupling. Several members of the RGS family are expressed in the brain, where they have precise roles in regulation of important physiological processes. The unique functions of each RGS can be attributed to its structure, distinct pattern of expression, and regulation, and its preferential interactions with receptors, Galpha subunits and other signaling proteins. Evidence suggests dysfunction of RGS proteins is related to several neuropathological conditions. Moreover, clinical and preclinical work reveals that the efficacy and/or side effects of treatments are highly influenced by RGS activity. This article summarizes findings on RGS proteins in vulnerability to several neuropsychiatric disorders, the mechanism via which RGS proteins control neuronal responses and their potential use as drug targets.

Structural determinants of G-protein alpha subunit selectivity by regulator of G-protein signaling 2 (RGS2)

"Regulator of G-protein signaling" (RGS) proteins facilitate the termination of G protein-coupled receptor (GPCR) signaling via their ability to increase the intrinsic GTP hydrolysis rate of Galpha subunits (known as GTPase-accelerating protein or "GAP" activity). RGS2 is unique in its in vitro potency and selectivity as a GAP for Galpha(q) subunits. As many vasoconstrictive hormones signal via G(q) heterotrimer-coupled receptors, it is perhaps not surprising that RGS2-deficient mice exhibit constitutive hypertension. However, to date the particular structural features within RGS2 determining its selectivity for Galpha(q) over Galpha(i/o) substrates have not been completely characterized. Here, we examine a trio of point mutations to RGS2 that elicits Galpha(i)-directed binding and GAP activities without perturbing its association with Galpha(q). Using x-ray crystallography, we determined a model of the triple mutant RGS2 in complex with a transition state mimetic form of Galpha(i) at 2.8-A resolution. Structural comparison with unliganded, wild type RGS2 and of other RGS domain/Galpha complexes highlighted the roles of these residues in wild type RGS2 that weaken Galpha(i) subunit association. Moreover, these three amino acids are seen to be evolutionarily conserved among organisms with modern cardiovascular systems, suggesting that RGS2 arose from the R4-subfamily of RGS proteins to have specialized activity as a potent and selective Galpha(q) GAP that modulates cardiovascular function.

Variant in RGS2 moderates posttraumatic stress symptoms following potentially traumatic event exposure

Polymorphisms in the RGS2 (regulator of G-protein signaling 2) gene were found to be associated with anxious behavior in mice and anxiety in humans. We examined whether rs4606, a single nucleotide polymorphism (SNP) of RGS2, and social support moderated risk for PTSD in an epidemiologic sample. The study examines 607 adults from the 2004 Florida Hurricanes study who returned buccal DNA samples via mail. rs4606 was associated with increased symptoms of posthurricane PTSD symptoms under conditions of high hurricane exposure and low social support (P<.05). Further, this polymorphism was associated with lifetime PTSD symptoms under conditions of lifetime exposure to a potentially traumatic event, and low social support (P<.001). These gene by environment interactions remained significant after adjustment for sex, ancestry, and age. RGS2 rs4606 modifies risk of postdisaster and lifetime PTSD symptoms under conditions of high stressor exposure. This is the first demonstration of gene-environment interaction for this locus.

RGS2 and generalized anxiety disorder in an epidemiologic sample of hurricane-exposed adults

BACKGROUND

Generalized anxiety disorder (GAD) is a common and sometimes disabling condition often associated with stressful life events that involve significant loss or danger. The disorder appears moderately heritable. Polymorphisms in the RGS2 (regulator of G-protein signaling 2) gene were recently associated with anxious behavior in mice and panic disorder and trait anxiety in humans. We examined whether rs4606, a single nucleotide polymorphism (SNP) in the 3' UTR of RGS2, was associated with GAD in an epidemiologic sample of adults exposed to the 2004 Florida Hurricanes.

METHODS

The sample for the current study is 607 adults from the 2004 Florida Hurricane Study who returned buccal DNA samples via mail. Participants were selected via random digit dial procedures and interviewed via telephone about hurricane exposure, social support, and GAD symptoms. The outcome measure was DSM-IV diagnosis of GAD derived from structured interviews.

RESULTS

RGS2 SNP rs4606 was significantly associated with GAD in this sample. In logistic regression analyses, each C allele was associated with a 100% (P=.026) increased risk of GAD after controlling for age, sex, ancestry, hurricane exposure, and social support.

CONCLUSIONS

These findings are consistent with a previously published study showing a higher prevalence of the C allele among panic disorder patients than controls. This study points toward a relevant polymorphism for GAD at the 3' end of the RGS2 gene; and suggests that studying a recently disaster-exposed sample is both feasible and may improve power to find gene-disorder associations.

Variation in RGS2 is associated with suicidal ideation in an epidemiological study of adults exposed to the 2004 Florida hurricanes

This study examined whether rs4606, a single nucleotide polymorphism (SNP) in the translated region at the 3' end of RGS2, was related to suicidal ideation in an epidemiologic sample of adults living in areas affected by the 2004 Florida hurricanes. An epidemiologic sample of residents of Florida was recruited via random digit-dial procedures after the 2004 Florida hurricanes; participants were interviewed about suicidal ideation, hurricane exposure, and social support. Participants who returned buccal DNA samples via mail (n = 607) were included here. Rs4606 in RGS2 was associated with increased symptoms of current suicidal ideation (p < 0.01). Each "C" allele was associated with 5.59 times increased risk of having current ideation. No gene-by-environment interactions were found, perhaps due to low power. RGS2 rs4606 is related to risk of current suicidal ideation in stressor-exposed adults.

Association analysis of Rgs7 variants with panic disorder

Following our recent finding of Rgs2 playing a role in the development of human panic disorder (PD), we examine another positional and functional candidate from the functionally interwoven Rgs (regulator of G-protein signaling) family, Rgs7, in the pathogenesis of PD. A German PD sample (N = 224) was compared with matched controls (N = 224) for seven SNPs within and flanking the gene. The intronic SNP3 (rs11805657) and its corresponding haplotypes were found to be associated with PD, particularly PD with comorbid agoraphobia (PDAgP), with the effect originating from the female subgroup (P values 0.008-0.047). The rare A-allele was underrepresented in patients, suggesting a protective effect with carriers possessing an about 2-fold lower risk for developing the disorder compared to G/G homozygotes. Our results argue against a major role of Rgs7 gene variants in the pathogenesis of PD, but are consistent with a minor gender-specific effect on PD, particularly PDAgP.