Influence of RGS2 on sertraline treatment for social anxiety disorder

Anti-angiogenic mechanisms and serotonergic dysfunction in the Rgs2 knockout model for the study of psycho-obstetric risk

Psychiatric and obstetric diseases are growing threats to public health and share high rates of co-morbidity. G protein-coupled receptor signaling (e.g., vasopressin, serotonin) may be a convergent psycho-obstetric risk mechanism. Regulator of G Protein Signaling 2 (RGS2) mutations increase risk for both the gestational disease preeclampsia and for depression. We previously found preeclampsia-like, anti-angiogenic obstetric phenotypes with reduced placental Rgs2 expression in mice. Here, we extend this to test whether conserved cerebrovascular and serotonergic mechanisms are also associated with risk for neurobiological phenotypes in the Rgs2 KO mouse. Rgs2 KO exhibited anxiety-, depression-, and hedonic-like behaviors. Cortical vascular density and vessel length decreased in Rgs2 KO; cortical and white matter thickness and cell densities were unchanged. In Rgs2 KO, serotonergic gene expression was sex-specifically changed (e.g., cortical Htr2a, Maoa increased in females but all serotonin targets unchanged or decreased in males); redox-related expression increased in paraventricular nucleus and aorta; and angiogenic gene expression was changed in male but not female cortex. Whole-cell recordings from dorsal raphe serotonin neurons revealed altered 5-HT1A receptor-dependent inhibitory postsynaptic currents (5-HT1A-IPSCs) in female but not male KO neurons. Additionally, serotonin transporter blockade by the SSRI sertraline increased the amplitude and time-to-peak of 5-HT1A-IPSCs in KO neurons to a greater extent than in WT neurons in females only. These results demonstrate behavioral, cerebrovascular, and sertraline hypersensitivity phenotypes in Rgs2 KOs, some of which are sex-specific. Disruptions may be driven by vascular and cell stress mechanisms linking the shared pathogenesis of psychiatric and obstetric disease to reveal future targets.

Candidate Biological Markers for Social Anxiety Disorder: A Systematic Review

Social anxiety disorder (SAD) is a common psychiatric condition associated with a high risk of psychiatric comorbidity and impaired social/occupational functioning when not promptly treated. The identification of biological markers may facilitate the diagnostic process, leading to an early and proper treatment. Our aim was to systematically review the available literature about potential biomarkers for SAD. A search in the main online repositories (PubMed, ISI Web of Knowledge, PsychInfo, etc.) was performed. Of the 662 records screened, 61 were included. Results concerning cortisol, neuropeptides and inflammatory/immunological/neurotrophic markers remain inconsistent. Preliminary evidence emerged about the role of chromosome 16 and the endomannosidase gene, as well as of epigenetic factors, in increasing vulnerability to SAD. Neuroimaging findings revealed an altered connectivity of different cerebral areas in SAD patients and amygdala activation under social threat. Some parameters such as salivary alpha amylase levels, changes in antioxidant defenses, increased gaze avoidance and QT dispersion seem to be associated with SAD and may represent promising biomarkers of this condition. However, the preliminary positive correlations have been poorly replicated. Further studies on larger samples and investigating the same biomarkers are needed to identify more specific biological markers for SAD.

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.

Genetics of social anxiety disorder: a systematic review

Social anxiety disorder (SAD) is a common psychiatric disorder, often associated with avoidant temperament. Research studies have implicated a strong genetic architecture of SAD. We have conducted a systematic review on the genetics of SAD and yielded 66 articles. In general, prior research studies have focused on the serotonin transporter, oxytocin receptor, brain-derived neurotrophic factor and catechol-O-methyltransferase genes. Mixed and inconsistent results have been reported. Additional approaches and phenotypes have also been investigated, including pharmacogenetics of treatment response, imaging genetics and gene-environment interactions. Future directions warrant further international collaborative efforts, deep-phenotyping of clinical characteristics including consistent and reliable measurement-based symptom severity, and larger sample sizes to ensure sufficient power for stratification due to the heterogeneity of this chronic and often debilitating condition.

The Serotonin-Immune Axis in Preeclampsia

PURPOSE OF REVIEW

To review the literature and detail the potential immune mechanisms by which hyperserotonemia may drive pro-inflammation in preeclampsia and to provide insights into potential avenues for therapeutic discovery.

RECENT FINDINGS

Preeclampsia is a severe hypertensive complication of pregnancy associated with significant maternal and fetal risk. Though it lacks any effective treatment aside from delivery of the fetus and placenta, recent work suggests that targeting serotonin systems may be one effective therapeutic avenue. Serotonin dysregulation underlies multiple domains of physiologic dysfunction in preeclampsia, including vascular hyporeactivity and excess platelet aggregation. Broadly, serotonin is increased across maternal and placental domains, driven by decreased catabolism and increased availability of tryptophan precursor. Pro-inflammation, another hallmark of the disease, may drive hyperserotonemia in preeclampsia. Interactions between immunologic dysfunction and hyperserotonemia in preeclampsia depend on multiple mechanisms, which we discuss in the present review. These include altered immune cell, kynurenine pathway metabolism, and aberrant cytokine production mechanisms, which we detail. Future work may leverage animal and in vitro models to reveal serotonin targets in the context of preeclampsia's immune biology, and ultimately to mitigate vascular and platelet dysfunction in the disease. Hyperserotonemia in preeclampsia drives pro-inflammation via metabolic, immune cell, and cytokine-based mechanisms. These immune mechanisms may be targeted to treat vascular and platelet endophenotypes in preeclampsia.

Emerging Roles for Regulator of G Protein Signaling 2 in (Patho)physiology

Since their discovery in the mid-1990s, regulator of G protein signaling (RGS) proteins have emerged as key regulators of signaling through G protein-coupled receptors. Among the over 20 known RGS proteins, RGS2 has received increasing interest as a potential therapeutic drug target with broad clinical implications. RGS2 is a member of the R4 subfamily of RGS proteins and is unique in that it is selective for Gα q Despite only having an RGS domain, responsible for the canonical GTPase activating protein activity, RGS2 can regulate additional processes, such as protein synthesis and adenylate cyclase activity, through protein-protein interactions. Here we provide an update of the current knowledge of RGS2 function as it relates to molecular mechanisms of regulation as well as its potential role in regulating a number of physiologic systems and pathologies, including cardiovascular disease and central nervous system disorders, as well as various forms of cancer. SIGNIFICANCE STATEMENT: Regulator of G protein signaling (RGS) proteins represent an exciting class of novel drug targets. RGS2, in particular, could have broad clinical importance. As more details are emerging on the regulation of RGS2 in various physiological systems, the potential utility of this small protein in therapeutic development is increasing.

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.

RGS2 drives male aggression in mice via the serotonergic system

Aggressive behavior in our modern, civilized society is often counterproductive and destructive. Identifying specific proteins involved in the disease can serve as therapeutic targets for treating aggression. Here, we found that overexpression of RGS2 in explicitly serotonergic neurons augments male aggression in control mice and rescues male aggression in Rgs2-/- mice, while anxiety is not affected. The aggressive behavior is directly correlated to the immediate early gene c-fos induction in the dorsal raphe nuclei and ventrolateral part of the ventromedial nucleus hypothalamus, to an increase in spontaneous firing in serotonergic neurons and to a reduction in the modulatory action of Gi/o and Gq/11 coupled 5HT and adrenergic receptors in serotonergic neurons of Rgs2-expressing mice. Collectively, these findings specifically identify that RGS2 expression in serotonergic neurons is sufficient to drive male aggression in mice and as a potential therapeutic target for treating aggression.

Four single nucleotide polymorphisms in genes involved in neuronal signaling are associated with Opioid Use Disorder in West Virginia

Objective

Pilot study to assess utility in opioid use disorder (OUD) of a panel of single nucleotide polymorphisms in genes previously related to substance use disorder (SUD) and/or phenotypes that predispose individuals to OUD/SUD.

Design

Genetic association study.

Setting

West Virginia University's Chestnut Ridge Center Comprehensive Opioid Abuse Treatment (COAT) clinic for individuals diagnosed with OUD.

Patients

Sixty patients 18 years of age or older with OUD undergoing medication (buprenorphine/naloxone)-assisted treatment (MAT); all sixty patients recruited contributed samples for genetic analysis.

Outcome Measures

Minor allele frequencies for single nucleotide polymorphisms.

Results

Four of the fourteen single nucleotide polymorphisms examined were present at frequencies that are statistically significantly different than in a demographically-matched general population.

Conclusions

For the purposes of testing WV individuals via genetic means for predisposition to OUD, at least four single nucleotide polymorphisms in three genes are likely to have utility in predicting susceptibility. Additional studies with larger populations will need to be conducted to confirm these results before use in a clinical setting.

Genetics of Anxiety Disorders

PURPOSE OF REVIEW

Anxiety disorders are among the most common mental disorders with a lifetime prevalence of over 20%. Clinically, anxiety is not thought of as a homogenous disorder, but is subclassified in generalized, panic, and phobic anxiety disorder. Anxiety disorders are moderately heritable. This review will explore recent genetic and epigenetic approaches to anxiety disorders explaining differential susceptibility risk.

RECENT FINDINGS

A substantial portion of the variance in susceptibility risk can be explained by differential inherited and acquired genetic and epigenetic risk. Available data suggest that anxiety disorders are highly complex and polygenic. Despite the substantial progress in genetic research over the last decade, only few risk loci for anxiety disorders have been identified so far. This review will cover recent findings from large-scale genome-wide association studies as well as newer epigenome-wide studies. Progress in this area will likely require analysis of much larger sample sizes than have been reported to date. We discuss prospects for clinical translation of genetic findings and future directions for research.

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.

A functional genetic variation of SLC6A2 repressor hsa-miR-579-3p upregulates sympathetic noradrenergic processes of fear and anxiety

Increased sympathetic noradrenergic signaling is crucially involved in fear and anxiety as defensive states. MicroRNAs regulate dynamic gene expression during synaptic plasticity and genetic variation of microRNAs modulating noradrenaline transporter gene (SLC6A2) expression may thus lead to altered central and peripheral processing of fear and anxiety. In silico prediction of microRNA regulation of SLC6A2 was confirmed by luciferase reporter assays and identified hsa-miR-579-3p as a regulating microRNA. The minor (T)-allele of rs2910931 (MAF_cases = 0.431, MAF_controls = 0.368) upstream of MIR579 was associated with panic disorder in patients (p_allelic = 0.004, n_cases = 506, n_controls = 506) and with higher trait anxiety in healthy individuals (p_ASI = 0.029, p_ACQ = 0.047, n = 3112). Compared to the major (A)-allele, increased promoter activity was observed in luciferase reporter assays in vitro suggesting more effective MIR579 expression and SLC6A2 repression in vivo (p = 0.041). Healthy individuals carrying at least one (T)-allele showed a brain activation pattern suggesting increased defensive responding and sympathetic noradrenergic activation in midbrain and limbic areas during the extinction of conditioned fear. Panic disorder patients carrying two (T)-alleles showed elevated heart rates in an anxiety-provoking behavioral avoidance test (F(2, 270) = 5.47, p = 0.005). Fine-tuning of noradrenaline homeostasis by a MIR579 genetic variation modulated central and peripheral sympathetic noradrenergic activation during fear processing and anxiety. This study opens new perspectives on the role of microRNAs in the etiopathogenesis of anxiety disorders, particularly their cardiovascular symptoms and comorbidities.

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.

Patient similarity for precision medicine: A systematic review

Evidence-based medicine is the most prevalent paradigm adopted by physicians. Clinical practice guidelines typically define a set of recommendations together with eligibility criteria that restrict their applicability to a specific group of patients. The ever-growing size and availability of health-related data is currently challenging the broad definitions of guideline-defined patient groups. Precision medicine leverages on genetic, phenotypic, or psychosocial characteristics to provide precise identification of patient subsets for treatment targeting. Defining a patient similarity measure is thus an essential step to allow stratification of patients into clinically-meaningful subgroups. The present review investigates the use of patient similarity as a tool to enable precision medicine. 279 articles were analyzed along four dimensions: data types considered, clinical domains of application, data analysis methods, and translational stage of findings. Cancer-related research employing molecular profiling and standard data analysis techniques such as clustering constitute the majority of the retrieved studies. Chronic and psychiatric diseases follow as the second most represented clinical domains. Interestingly, almost one quarter of the studies analyzed presented a novel methodology, with the most advanced employing data integration strategies and being portable to different clinical domains. Integration of such techniques into decision support systems constitutes and interesting trend for future research.

Imaging and Genetic Approaches to Inform Biomarkers for Anxiety Disorders, Obsessive-Compulsive Disorders, and PSTD

Anxiety disorders are the most common mental health problem in the world and also claim the highest health care cost among various neuropsychiatric disorders. Anxiety disorders have a chronic and recurrent course and cause significantly negative impacts on patients' social, personal, and occupational functioning as well as quality of life. Despite their high prevalence rates, anxiety disorders have often been under-diagnosed or misdiagnosed, and consequently under-treated. Even with the correct diagnosis, anxiety disorders are known to be difficult to treat successfully. In order to implement better strategies in diagnosis, prognosis, treatment decision, and early prevention for anxiety disorders, tremendous efforts have been put into studies using genetic and neuroimaging techniques to advance our understandings of the underlying biological mechanisms. In addition to anxiety disorders including panic disorder, generalised anxiety disorder (GAD), specific phobias, social anxiety disorders (SAD), due to overlapping symptom dimensions, obsessive-compulsive disorder (OCD), and post-traumatic stress disorder (PTSD) (which were removed from the anxiety disorder category in DSM-5 to become separate categories) are also included for review of relevant genetic and neuroimaging findings. Although the number of genetic or neuroimaging studies focusing on anxiety disorders is relatively small compare to other psychiatric disorders such as psychotic disorders or mood disorders, various structural abnormalities in the grey or white matter, functional alterations of activity during resting-state or task conditions, molecular changes of neurotransmitter receptors or transporters, and genetic associations have all been reported. With continuing effort, further genetic and neuroimaging research may potentially lead to clinically useful biomarkers for the prevention, diagnosis, and management of these disorders.

Pharmacotherapy for social anxiety disorder: Interpersonal predictors of outcome and the mediating role of the working alliance

Social anxiety disorder (SAD) is highly prevalent and associated with high levels of impairment and distress. Therapies for SAD leave many patients symptomatic at the end of treatment, and little is known about predictors or mechanisms of treatment outcome. Given the interpersonal dysfunction fundamental to SAD, this study investigated whether prominent interpersonal features of SAD (submissive behavior, childhood maltreatment, suppression of anger, and depression) predicted attrition and response to pharmacotherapy and whether the working alliance mediated these relationships. This is the first study to examine the role of the working alliance in pharmacotherapy for SAD. One hundred thirty-eight treatment-seeking individuals with a primary diagnosis of SAD received 12 weeks of open treatment with paroxetine. Higher levels of depression predicted greater severity of SAD at the end of treatment, and higher levels of submissive behavior and childhood emotional maltreatment predicted a greater probability of attrition from treatment. The psychiatrist-assessed working alliance mediated response to pharmacotherapy for individuals who reported a history of emotional maltreatment. These results identify variables that predict pharmacotherapy outcome and emphasize the importance of the working alliance as a mechanism of treatment response for those with a history of emotional maltreatment. Implications for person-specific treatment selection are discussed.

Morbid Anxiety: Identification and Treatment

Due to their prevalence, chronicity, and poorly understood pathophysiology, anxiety disorders remain an important public health problem. Despite clear diagnostic guidelines and the availability of excellent evidence-based treatments, most anxiety patients remain underrecognized and inadequately treated. This clinical synthesis highlights changes to anxiety disorder diagnosis that became effective with DSM-5. The article also provides some clinical perspective on clarifying differential diagnostic problems and building an alliance with the anxious patient. The quality and strength of the evidence base for current anxiolytic medications options (selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, benzodiazepines, and other agents), antianxiety psychotherapies (cognitive-behavioral therapy and brief dynamic therapies), and combination treatments are discussed. A brief update on newer treatment strategies, such as cognitive enhancement, complementary therapies, and neuromodulation, is included. Future directions for anxiety nosology and treatment are summarized, including the National Institute of Mental Health Research Domain Criteria initiative and the promising role of personalized medicine.

An RGS2 3'UTR polymorphism is associated with preeclampsia in overweight women

BACKGROUND

Preeclampsia is a common and heterogeneous vascular syndrome of pregnancy. Its genetic risk profile is yet unknown and may vary between individuals and populations. The rs4606 3' UTR polymorphism of the Regulator of G-protein signaling 2 gene (RGS2) in the mother has been implicated in preeclampsia as well as in the development of chronic hypertension after preeclampsia. The RGS2 protein acts as an inhibitor of physiological vasoconstrictive pathways, and a low RGS2 level is associated with hypertension and obesity, two conditions that predispose to preeclampsia. We genotyped the rs4606 polymorphism in 1339 preeclamptic patients and in 697 controls from the Finnish Genetics of Preeclampsia Consortium (FINNPEC) cohort to study the association of the variant with preeclampsia.

RESULTS

No association between rs4606 and preeclampsia was detected in the analysis including all women. However, the polymorphism was associated with preeclampsia in a subgroup of overweight women (body mass index ≥ 25 kg/m(2), and < 30 kg/m(2)) (dominant model; odds ratio, 1.64; 95 % confidence interval, 1.10-2.42).

CONCLUSIONS

Our results suggest that RGS2 might be involved in the pathogenesis of preeclampsia particularly in overweight women and contribute to their increased risk for hypertension and other types of cardiovascular disease later in life.

Biological markers for anxiety disorders, OCD and PTSD - a consensus statement. Part I: Neuroimaging and genetics

OBJECTIVES

Biomarkers are defined as anatomical, biochemical or physiological traits that are specific to certain disorders or syndromes. The objective of this paper is to summarise the current knowledge of biomarkers for anxiety disorders, obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD).

METHODS

Findings in biomarker research were reviewed by a task force of international experts in the field, consisting of members of the World Federation of Societies for Biological Psychiatry Task Force on Biological Markers and of the European College of Neuropsychopharmacology Anxiety Disorders Research Network.

RESULTS

The present article (Part I) summarises findings on potential biomarkers in neuroimaging studies, including structural brain morphology, functional magnetic resonance imaging and techniques for measuring metabolic changes, including positron emission tomography and others. Furthermore, this review reports on the clinical and molecular genetic findings of family, twin, linkage, association and genome-wide association studies. Part II of the review focuses on neurochemistry, neurophysiology and neurocognition.

CONCLUSIONS

Although at present, none of the putative biomarkers is sufficient and specific as a diagnostic tool, an abundance of high-quality research has accumulated that will improve our understanding of the neurobiological causes of anxiety disorders, OCD and PTSD.

Biological predictors of pharmacological therapy in anxiety disorders

At least one third of patients with anxiety disorders do not adequately respond to available pharmacological treatment. The reason that some patients with anxiety disorders respond well, but others not, to the same classes of medication is not yet fully understood. It is suggested that several biological factors may influence treatment mechanisms in anxiety and therefore could be identified as possible biomarkers predicting treatment response. In this review, we look at current evidence exploring different types of treatment predictors, including neuroimaging, genetic factors, and blood-related measures, which could open up novel perspectives in clinical management of patients with anxiety disorders.

Novel developments in genetic and epigenetic mechanisms of anxiety

PURPOSE OF REVIEW

The present review aims to deliver a systematic overview of current developments and trends in (epi)genetics of anxiety and to identify upcoming challenges and opportunities.

RECENT FINDINGS

Genes related to peptide and hormone signaling have been suggested for anxiety-related phenotypes, e.g., the NPSR1 gene, which has been associated predominantly with panic disorder in women, and shown to interact with environmental factors and to influence psychometric, neurophysiological, and neuroimaging correlates of anxiety. Similar multi-level results have been reported for genetic and epigenetic variation in the OXTR gene, especially in social anxiety disorder (SAD), and for CRHR1 gene variation in women with panic disorder. Variants in RGS2 and ASIC1 genes were linked to panic disorder, with the latter also being implicated in SAD treatment response. Finally, monoaminergic 'risk' genes (SLC6A4, MAOA, HTR1A) were related to SAD, generalized anxiety disorder and women with panic disorder, anxiety traits and response to psychopharmacological and psychotherapeutic interventions.

SUMMARY

Converging evidence for potential genetic and epigenetic risk markers has been gathered and future studies call for independent replications and multi-level integration of dimensional approaches, environmental factors, and biological readouts, while considering sex-specific substratification. Particularly, epigenetic variation appears promising for disease course and treatment response predictions.

The Genetics of Stress-Related Disorders: PTSD, Depression, and Anxiety Disorders

Research into the causes of psychopathology has largely focused on two broad etiologic factors: genetic vulnerability and environmental stressors. An important role for familial/heritable factors in the etiology of a broad range of psychiatric disorders was established well before the modern era of genomic research. This review focuses on the genetic basis of three disorder categories-posttraumatic stress disorder (PTSD), major depressive disorder (MDD), and the anxiety disorders-for which environmental stressors and stress responses are understood to be central to pathogenesis. Each of these disorders aggregates in families and is moderately heritable. More recently, molecular genetic approaches, including genome-wide studies of genetic variation, have been applied to identify specific risk variants. In this review, I summarize evidence for genetic contributions to PTSD, MDD, and the anxiety disorders including genetic epidemiology, the role of common genetic variation, the role of rare and structural variation, and the role of gene-environment interaction. Available data suggest that stress-related disorders are highly complex and polygenic and, despite substantial progress in other areas of psychiatric genetics, few risk loci have been identified for these disorders. Progress in this area will likely require analysis of much larger sample sizes than have been reported to date. The phenotypic complexity and genetic overlap among these disorders present further challenges. The review concludes with a discussion of prospects for clinical translation of genetic findings and future directions for research.

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.

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.

Targeting the modulation of neural circuitry for the treatment of anxiety disorders

Anxiety disorders are a major public health concern. Here, we examine the familiar area of anxiolysis in the context of a systems-level understanding that will hopefully lead to revealing an underlying pharmacological connectome. The introduction of benzodiazepines nearly half a century ago markedly improved the treatment of anxiety disorders. These agents reduce anxiety rapidly by allosterically enhancing the postsynaptic actions of GABA at inhibitory type A GABA receptors but side effects limit their use in chronic anxiety disorders. Selective serotonin reuptake inhibitors and serotonin/norepinephrine reuptake inhibitors have emerged as an effective first-line alternative treatment of such anxiety disorders. However, many individuals are not responsive and side effects can be limiting. Research into a relatively new class of agents known as neurosteroids has revealed novel modulatory sites and mechanisms of action that are providing insights into the pathophysiology of certain anxiety disorders, potentially bridging the gap between the GABAergic and serotonergic circuits underlying anxiety. However, translating the pharmacological activity of compounds targeted to specific receptor subtypes in rodent models of anxiety to effective therapeutics in human anxiety has not been entirely successful. Since modulating any one of several broad classes of receptor targets can produce anxiolysis, we posit that a systems-level discovery platform combined with an individualized medicine approach based on noninvasive brain imaging would substantially advance the development of more effective therapeutics.