Genetic association study between RGS2 and anxiety-related phenotypes

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.

The genetics of anxiety-related negative valence system traits

NIMH's Research Domain Criteria (RDoC) domain of negative valence systems (NVS) captures constructs of negative affect such as fear and distress traditionally subsumed under the various internalizing disorders. Through its aims to capture dimensional measures that cut across diagnostic categories and are linked to underlying neurobiological systems, a large number of phenotypic constructs have been proposed as potential research targets. Since "genes" represent a central "unit of analysis" in the RDoC matrix, it is important for studies going forward to apply what is known about the genetics of these phenotypes as well as fill in the gaps of existing knowledge. This article reviews the extant genetic epidemiological data (twin studies, heritability) and molecular genetic association findings for a broad range of putative NVS phenotypic measures. We find that scant genetic epidemiological data is available for experimentally derived measures such as attentional bias, peripheral physiology, or brain-based measures of threat response. The molecular genetic basis of NVS phenotypes is in its infancy, since most studies have focused on a small number of candidate genes selected for putative association to anxiety disorders (ADs). Thus, more research is required to provide a firm understanding of the genetic aspects of anxiety-related NVS constructs. © 2016 Wiley Periodicals, Inc.

Direct, indirect and pleiotropic effects of candidate genes on internalizing disorder psychopathology

BACKGROUND

Twin studies of internalizing disorders suggest that their high co-morbidity is partially explained by shared genetic risk. Few studies have investigated pleiotropic effects of well-validated candidate genes across phenotypes.

METHOD

Subjects were 928 Caucasian patients who presented to an out-patient clinic specializing in the assessment and treatment of anxiety and mood disorders. We constructed latent dimensional phenotypes across the internalizing spectrum (neuroticism, extraversion, depression, generalized anxiety, panic/agoraphobia, social phobia, post-traumatic stress, and obsessions-compulsions) by combining diagnostic criteria with other clinical indicators. We selected multiple variants in four evidence-based candidate genes (SLC6A4, COMT, GAD1, RGS2) with previously reported effects on several of these phenotypes. We conducted genetic association testing of their direct and indirect effects as well as gene × stress interactions (G × E).

RESULTS

We detected 19 nominally significant main effect associations for the 10 polymorphisms tested among the eight phenotypes (24%). These were generally phenotype non-specific, showing pleiotropic effects across multiple domains. The majority of observed sharing was between depression, panic disorder, and post-traumatic stress disorder. Some of these were best explained by mediational models in which genes increase liability for disorders indirectly via their effects on temperament. Limited G × E effects were detected between variants in SLC6A4 and both panic/agoraphobia and post-traumatic stress.

CONCLUSIONS

Examining just a few candidate genes for their potential roles in internalizing phenotypes, we found moderate support for the shared effects of several polymorphisms. These findings highlight the richness and complexity by which genes potentially contribute to psychopathology via pleiotropy, moderation by stress, and mediation by temperament.

MicroRNA hsa-miR-4717-5p regulates RGS2 and may be a risk factor for anxiety-related traits

Regulator of G-protein Signaling 2 (RGS2) is a key regulator of G-protein-coupled signaling pathways involved in fear and anxiety. Data from rodent models and genetic analysis of anxiety-related traits and disorders in humans suggest down-regulation of RGS2 expression to be a risk factor for anxiety. Here we investigated, whether genetic variation in microRNAs mediating posttranscriptional down-regulation of RGS2 may be a risk factor for anxiety as well. 75 microRNAs predicted to regulate RGS2 were identified by four bioinformatic algorithms and validated experimentally by luciferase reporter gene assays. Specificity was confirmed for six microRNAs (hsa-miR-1271-5p, hsa-miR-22-3p, hsa-miR-3591-3p, hsa-miR-377-3p, hsa-miR-4717-5p, hsa-miR-96-5p) by disrupting their seed sequence at the 3' untranslated region of RGS2. Hsa-miR-4717-5p showed the most robust effect on RGS2 and regulated two other candidate genes of anxiety disorders (CNR1 and IKBKE) as well. Two SNPs (rs150925, rs161427) within and 1,000 bp upstream of the hostgene of hsa-miR-4717-5p (MIR4717) show a minor allele frequency greater than 0.05. Both were in high linkage disequilibrium (r(2) = 1, D' = 1) and both major (G) alleles showed a trend for association with panic disorder with comorbid agoraphobia in one of two patient/control samples (combined n(patients) = 497). Dimensional anxiety traits, as described by Anxiety Sensitivity Index (ASI) and Agoraphobic Cognitions Questionnaire (ACQ) were significantly higher among carriers of both major (G) alleles in a combined patient/control sample (n(combined) = 831). Taken together, data indicate that MIR4717 regulates human RGS2 and contributes to the genetic risk towards anxiety-related traits.

Regulator of G Protein Signaling 2: A Versatile Regulator of Vascular Function

Regulators of G protein signaling (RGS) proteins of the B/R4 family are widely expressed in the cardiovascular system where their role in fine-tuning G protein signaling is critical to maintaining homeostasis. Among members of this family, RGS2 and RGS5 have been shown to play key roles in cardiac and smooth muscle function by tightly regulating signaling pathways that are activated through Gq/11 and Gi/o classes of heterotrimeric G proteins. This chapter reviews accumulating evidence supporting a key role for RGS2 in vascular function and the implication of changes in RGS2 function and/or expression in the pathogenesis of blood pressure disorders, particularly hypertension. With such understanding, RGS2 and the signaling pathways it controls may emerge as novel targets for developing next-generation antihypertensive drugs/agents.

The nature of individual differences in inhibited temperament and risk for psychiatric disease: A review and meta-analysis

What makes us different from one another? Why does one person jump out of airplanes for fun while another prefers to stay home and read? Why are some babies born with a predisposition to become anxious? Questions about individual differences in temperament have engaged the minds of scientists, psychologists, and philosophers for centuries. Recent technological advances in neuroimaging and genetics provide an unprecedented opportunity to answer these questions. Here we review the literature on the neurobiology of one of the most basic individual differences-the tendency to approach or avoid novelty. This trait, called inhibited temperament, is innate, heritable, and observed across species. Importantly, inhibited temperament also confers risk for psychiatric disease. Here, we provide a comprehensive review of inhibited temperament, including neuroimaging and genetic studies in human and non-human primates. We conducted a meta-analysis of neuroimaging findings in inhibited humans that points to alterations in a fronto-limbic-basal ganglia circuit; these findings provide the basis of a model of inhibited temperament neurocircuitry. Lesion and neuroimaging studies in non-human primate models of inhibited temperament highlight roles for the amygdala, hippocampus, orbitofrontal cortex, and dorsal prefrontal cortex. Genetic studies highlight a role for genes that regulate neurotransmitter function, such as the serotonin transporter polymorphisms (5-HTTLPR), as well as genes that regulate stress response, such as corticotropin-releasing hormone (CRH). Together these studies provide a foundation of knowledge about the genetic and neural substrates of this most basic of temperament traits. Future studies using novel imaging methods and genetic approaches promise to expand upon these biological bases of inhibited temperament and inform our understanding of risk for psychiatric disease.

RGS2 ggenetic variation: association analysis with panic disorder and dimensional as well as intermediate phenotypes of anxiety

Accumulating evidence from mouse models points to the G protein-coupled receptor RGS2 (regulator of G-protein signaling 2) as a promising candidate gene for anxiety in humans. Recently, RGS2 polymorphisms were found to be associated with various anxiety disorders, e.g., rs4606 with panic disorder (PD), but other findings have been negative or inconsistent concerning the respective risk allele. To further examine the role of RGS2 polymorphisms in the pathogenesis of PD, we genotyped rs4606 and five additional RGS2 tag single nucleotide polymorphisms (SNPs; rs16834831, rs10801153, rs16829458, rs1342809, rs1890397) in two independent PD samples, comprising 531 matched case/control pairs. The functional SNP rs4606 was nominally associated with PD when both samples were combined. The upstream SNP rs10801153 displayed a Bonferroni-resistant significant association with PD in the second and the combined sample (P = 0.006 and P = 0.017). We furthermore investigated the effect of rs10801153 on dimensional anxiety traits, a behavioral avoidance test (BAT), and an index for emotional processing in the respective subsets of the total sample. In line with categorical results, homozygous risk (G) allele carriers displayed higher scores on the Agoraphobic Cognitions Questionnaire (ACQ; P = 0.015) and showed significantly more defensive behavior during fear provoking situations (P = 0.001). Furthermore, significant effects on brain activation in response to angry (P = 0.013), happy (P = 0.042) and neutral faces (P = 0.032) were detected. Taken together, these findings provide further evidence for the potential role of RGS2 as a candidate gene for PD.

Regulators of G-protein-signaling proteins: negative modulators of G-protein-coupled receptor signaling

Regulators of G-protein-signaling (RGS) proteins are a category of intracellular proteins that have an inhibitory effect on the intracellular signaling produced by G-protein-coupled receptors (GPCRs). RGS along with RGS-like proteins switch on through direct contact G-alpha subunits providing a variety of intracellular functions through intracellular signaling. RGS proteins have a common RGS domain that binds to G alpha. RGS proteins accelerate GTPase and thus enhance guanosine triphosphate hydrolysis through the alpha subunit of heterotrimeric G proteins. As a result, they inactivate the G protein and quickly turn off GPCR signaling thus terminating the resulting downstream signals. Activity and subcellular localization of RGS proteins can be changed through covalent molecular changes to the enzyme, differential gene splicing, and processing of the protein. Other roles of RGS proteins have shown them to not be solely committed to being inhibitors but behave more as modulators and integrators of signaling. RGS proteins modulate the duration and kinetics of slow calcium oscillations and rapid phototransduction and ion signaling events. In other cases, RGS proteins integrate G proteins with signaling pathways linked to such diverse cellular responses as cell growth and differentiation, cell motility, and intracellular trafficking. Human and animal studies have revealed that RGS proteins play a vital role in physiology and can be ideal targets for diseases such as those related to addiction where receptor signaling seems continuously switched on.

Regulator of G-protein signaling 6 (RGS6) promotes anxiety and depression by attenuating serotonin-mediated activation of the 5-HT(1A) receptor-adenylyl cyclase axis

Targeting serotonin (5-HT) bioavailability with selective 5-HT reuptake inhibitors (SSRIs) remains the most widely used treatment for mood disorders. However, their limited efficacy, delayed onset of action, and side effects restrict their clinical utility. Endogenous regulator of G-protein signaling (RGS) proteins have been implicated as key inhibitors of 5-HT(1A)Rs, whose activation is believed to underlie the beneficial effects of SSRIs, but the identity of the specific RGS proteins involved remains unknown. We identify RGS6 as the critical negative regulator of 5-HT(1A)R-dependent antidepressant actions. RGS6 is enriched in hippocampal and cortical neurons, 5-HT(1A)R-expressing cells implicated in mood disorders. RGS6(-/-) mice exhibit spontaneous anxiolytic and antidepressant behavior rapidly and completely reversibly by 5-HT(1A)R blockade. Effects of the SSRI fluvoxamine and 5-HT(1A)R agonist 8-OH-DPAT were also potentiated in RGS6(+/-) mice. The phenotype of RGS6(-/-) mice was associated with decreased CREB phosphorylation in the hippocampus and cortex, implicating enhanced Gα(i)-dependent adenylyl cyclase inhibition as a possible causative factor in the behavior observed in RGS6(-/-) animals. Our results demonstrate that by inhibiting serotonergic innervation of the cortical-limbic neuronal circuit, RGS6 exerts powerful anxiogenic and prodepressant actions. These findings indicate that RGS6 inhibition may represent a viable means to treat mood disorders or enhance the efficacy of serotonergic agents.

Interaction between genetic variants and exposure to Hurricane Katrina on post-traumatic stress and post-traumatic growth: a prospective analysis of low income adults

BACKGROUND

There is considerable variation in psychological reactions to natural disasters, with responses ranging from relatively mild and transitory symptoms to severe and persistent posttraumatic stress (PTS). Some survivors also report post-traumatic growth (PTG), or positive psychological changes due to the experience and processing of the disaster and its aftermath. Gene-environment interaction (GxE) studies could offer new insight into the factors underlying variability in post-disaster psychological responses. However, few studies have explored GxE in a disaster context.

METHODS

We examined whether ten common variants in seven genes (BDNF, CACNA1C, CRHR1, FKBP5, OXTR, RGS2, SLC6A4) modified associations between Hurricane Katrina exposure and PTS and PTG. Data were from a prospective study of 205 low-income non-Hispanic Black parents residing in New Orleans prior to and following Hurricane Katrina.

RESULTS

We found a significant association (after correction) between RGS2 (rs4606; p=0.0044) and PTG, which was mainly driven by a cross-over GxE (p=0.006), rather than a main genetic effect (p=0.071). The G (minor allele) was associated with lower PTG scores for low levels of Hurricane exposure and higher PTG scores for moderate and high levels of exposure. We also found a nominally significant association between variation in FKBP5 (rs1306780, p=0.0113) and PTG, though this result did not survive correction for multiple testing.

LIMITATIONS

Although the inclusion of low-income non-Hispanic Black parents allowed us to examine GxE among a highly vulnerable group, our findings may not generalize to other populations or groups experiencing other natural disasters. Moreover, not all participants invited to participate in the genetic study provided saliva.

CONCLUSIONS

To our knowledge, this is the first study to identify GxE in the context of post-traumatic growth. Future studies are needed to clarify the role of GxE in PTS and PTG and post-disaster psychological responses, especially among vulnerable populations.

Anxiety genetics - findings from cross-species genome-wide approaches

Anxiety disorders are complex diseases, which often occur in combination with major depression, alcohol use disorder, or general medical conditions. Anxiety disorders were the most common mental disorders within the EU states in 2010 with 14% prevalence. Anxiety disorders are triggered by environmental factors in genetically susceptible individuals, and therefore genetic research offers a great route to unravel molecular basis of these diseases. As anxiety is an evolutionarily conserved response, mouse models can be used to carry out genome-wide searches for specific genes in a setting that controls for the environmental factors. In this review, we discuss translational approaches that aim to bridge results from unbiased genome-wide screens using mouse models to anxiety disorders in humans. Several methods, such as quantitative trait locus mapping, gene expression profiling, and proteomics, have been used in various mouse models of anxiety to identify genes that regulate anxiety or play a role in maintaining pathological anxiety. We first discuss briefly the evolutionary background of anxiety, which justifies cross-species approaches. We then describe how several genes have been identified through genome-wide methods in mouse models and subsequently investigated in human anxiety disorder samples as candidate genes. These studies have led to the identification of completely novel biological pathways that regulate anxiety in mice and humans, and that can be further investigated as targets for therapy.