Benedikt Klauke

Neuropeptide S receptor gene—converging evidence for a role in panic disorder

Animal studies have suggested neuropeptide S (NPS) and its receptor (NPSR) to be involved in the pathogenesis of anxiety-related behavior. In this study, a multilevel approach was applied to further elucidate the role of NPS in the etiology of human anxiety. The functional NPSR A/T (Asn107Ile) variant (rs324981) was investigated for association with (1) panic disorder with and without agoraphobia in two large, independent case–control studies, (2) dimensional anxiety traits, (3) autonomic arousal level during a behavioral avoidance test and (4) brain activation correlates of anxiety-related emotional processing in panic disorder. The more active NPSR rs324981 T allele was found to be associated with panic disorder in the female subgroup of patients in both samples as well as in a meta-analytic approach. The T risk allele was further related to elevated anxiety sensitivity, increased heart rate and higher symptom reports during a behavioral avoidance test as well as decreased activity in the dorsolateral prefrontal, lateral orbitofrontal and anterior cingulate cortex during processing of fearful faces in patients with panic disorder. The present results provide converging evidence for a female-dominant role of NPSR gene variation in panic disorder potentially through heightened autonomic arousal and distorted processing of anxiety-relevant emotional stimuli.

Monoamine oxidase A gene DNA hypomethylation - a risk factor for panic disorder?

The monoamine oxidase A (MAOA) gene has been suggested as a prime candidate in the pathogenesis of panic disorder. In the present study, DNA methylation patterns in the MAOA regulatory and exon 1/intron 1 region were investigated for association with panic disorder with particular attention to possible effects of gender and environmental factors. Sixty-five patients with panic disorder (44 females, 21 males) and 65 healthy controls were analysed for DNA methylation status at 42 MAOA CpG sites via direct sequencing of sodium bisulfate treated DNA extracted from blood cells. The occurrence of recent positive and negative life events was ascertained. Male subjects showed no or only very minor methylation with some evidence for relative hypomethylation at one CpG site in intron 1 in patients compared to controls. Female patients exhibited significantly lower methylation than healthy controls at 10 MAOA CpG sites in the promoter as well as in exon/intron 1, with significance surviving correction for multiple testing at four CpG sites (p≤0.001). Furthermore, in female subjects the occurrence of negative life events was associated with relatively decreased methylation, while positive life events were associated with increased methylation. The present pilot data suggest a potential role of MAOA gene hypomethylation in the pathogenesis of panic disorder particularly in female patients, possibly mediating a detrimental influence of negative life events. Future studies are warranted to replicate the present finding in independent samples, preferably in a longitudinal design.

Life events in panic disorder-an update on "candidate stressors".

Studies on gene–environment interactions in mental disorders are characterized by powerful genetic techniques and well defined “candidate genes,” whereas a definition of “candidate stressors,” in most cases assessed in the form of life events (LEs), is inconsistent or not even provided. This review addresses this problem, with particular attention to the clinical phenotype of panic disorder (PD), by providing an overview and critical discussion for which life events are known to contribute to the etiology of the disease and how they may be conceptualized. There is converging evidence for a significant impact of cumulative as well as specific life events, such as threat, interpersonal and health‐related events in adulthood, and abuse or loss/separation experiences in childhood, respectively, on the pathogenesis of panic disorder with some overlapping effect across the anxiety disorder spectrum as well as on comorbid major depression. Besides genetic vulnerability factors, personality and behavioral characteristics, such as anxiety sensitivity, neuroticism, and cognitive appraisal might moderate the influence of LEs on the development of panic disorder. The present state of knowledge regarding the specification and conceptualization of LEs in PD within a more complex multifactorial model, involving mediating and moderating factors in between genes and the clinical phenotype, is hoped to aid in informing future gene–environment interaction studies in panic disorder. Depression and Anxiety, 2010.

New names for known things: On the association of novel word forms with existing semantic information

The plasticity of the adult memory network for integrating novel word forms (lexemes) was investigated with whole-head magnetoencephalography (MEG). We showed that spoken word forms of an (artificial) foreign language are integrated rapidly and successfully into existing lexical and conceptual memory networks. The new lexemes were learned in an untutored way, by pairing them frequently with one particular object (and thus meaning), and infrequently with 10 other objects (learned set). Other novel word forms were encountered just as often, but paired with many different objects (nonlearned set). Their impact on semantic memory was assessed with cross-modal priming, with novel word forms as primes and object pictures as targets. The MEG counterpart of the N400 (N400m) served as an indicator of a semantic (mis)match between words and pictures. Prior to learning, all novel words induced a pronounced N400m mismatch effect to the pictures. This component was strongly reduced after training for the learned novel lexemes only, and now closely resembled the brains response to semantically related native-language words. This result cannot be explained by mere stimulus repetition or stimulus–stimulus association. Thus, learned novel words rapidly gained access to existing conceptual representations, as effectively as related native-language words. This association of novel lexemes and conceptual information happened fast and almost without effort. Neural networks mediating these integration processes were found within left temporal lobe, an area typically described as one of the main generators of the N400 response.

Meta-analysis argues for a female-specific role of MAOA-uVNTR in panic disorder in four European populations

Panic disorder (PD) is a common mental disorder, ranking highest among the anxiety disorders in terms of disease burden. The pathogenesis of PD is multifactorial with significant heritability, however only a few convincing risk genes have been reported thus far. One of the most promising candidates is the gene encoding monoamine oxidase A (MAOA), due to its key role in monoaminergic neurotransmission, established validity of animal models, and the efficacy of MAO inhibitors in the treatment of PD. A promoter repeat polymorphism in MAOA (MAOA‐uVNTR) impacts on gene expression; high‐expression alleles have been reported to increase the risk for PD. To further scrutinize the role of this polymorphism, we performed a formal meta‐analysis on MAOA‐uVNTR and PD using original data from four published European (Estonian, German, Italian, and Polish) samples and genotypes from three hitherto unpublished German PD samples, resulting in the largest (n = 1,115 patients and n = 1,260 controls) genetic study on PD reported to date. In the unpublished samples, evidence for association of MAOA‐uVNTR with PD was obtained in one of the three samples. Results of the meta‐analysis revealed a significant and female‐specific association when calculating an allelic model (OR = 1.23, P = 0.006). This sex‐specific effect might be explained by a gene‐dose effect causing higher MAOA expression in females. Taken together, our meta‐analysis therefore argues that high‐expression MAOA‐uVNTR alleles significantly increase the risk towards PD in women. However, epigenetic mechanisms might obfuscate the genetic association, calling for ascertainment in larger samples as well as assessment of the MAOA promoter methylation status therein.

Serotonin transporter gene and childhood trauma--a G × E effect on anxiety sensitivity.

Background: Genetic factors and environmental factors are assumed to interactively influence the pathogenesis of anxiety disorders. Thus, a gene–environment interaction (G × E) study was conducted with respect to anxiety sensitivity (AS) as a promising intermediate phenotype of anxiety disorders. Method: Healthy subjects (N = 363) were assessed for AS, childhood maltreatment (Childhood Trauma Questionnaire), and genotyped for functional serotonin transporter gene variants (5‐HTTLPR/5‐HTT rs25531). The influence of genetic and environmental variables on AS and its subdimensions was determined by a step‐wise hierarchical regression and a multiple indicator multiple cause (MIMIC) model. Results: A significant G × E effect of the more active 5‐HTT genotypes and childhood maltreatment on AS was observed. Furthermore, genotype (LL)–childhood trauma interaction particularly influenced somatic AS subdimensions, whereas cognitive subdimensions were affected by childhood maltreatment only. Conclusions: Results indicate a G × E effect of the more active 5‐HTT genotypes and childhood maltreatment on AS, with particular impact on its somatic subcomponent. Depression and Anxiety, 2011.

The interaction of early life experiences with COMT val158met affects anxiety sensitivity

The pathogenesis of anxiety disorders is considered to be multifactorial with a complex interaction of genetic factors and individual environmental factors. Therefore, the aim of this study was to examine gene‐by‐environment interactions of the genes coding for catechol‐O‐methyltransferase (COMT) and monoamine oxidase A (MAOA) with life events on measures related to anxiety. A sample of healthy subjects (N = 782; thereof 531 women; mean age M = 24.79, SD = 6.02) was genotyped for COMT rs4680 and MAOA‐uVNTR (upstream variable number of tandem repeats), and was assessed for childhood adversities [Childhood Trauma Questionnaire (CTQ)], anxiety sensitivity [Anxiety Sensitivity Index (ASI)] and anxious apprehension [Penn State Worry Questionnaire (PSWQ)]. Main and interaction effects of genotype, environment and gender on measures related to anxiety were assessed by means of regression analyses. Association analysis showed no main gene effect on either questionnaire score. A significant interactive effect of childhood adversities and COMT genotype was observed: Homozygosity for the low‐active met allele and high CTQ scores was associated with a significant increment of explained ASI variance [R2 = 0.040, false discovery rate (FDR) corrected P = 0.04]. A borderline interactive effect with respect to MAOA‐uVNTR was restricted to the male subgroup. Carriers of the low‐active MAOA allele who reported more aversive experiences in childhood exhibited a trend for enhanced anxious apprehension (R2 = 0.077, FDR corrected P = 0.10). Early aversive life experiences therefore might increase the vulnerability to anxiety disorders in the presence of homozygosity for the COMT 158met allele or low‐active MAOA‐uVNTR alleles.

Neuropeptide S receptor gene (NPSR) and life events: G × E effects on anxiety sensitivity and its subdimensions

Abstract Objectives. The pathogenesis of anxiety is assumed to be interactively influenced by genetic and environmental factors. Thus, a gene–environment interaction (G × E) study of the neuropeptide S receptor gene (NPSR) A/T polymorphism (rs324981) and life events was conducted with respect to anxiety sensitivity (AS) as an intermediate phenotype of anxiety disorders. Methods. A sample of 475 healthy German subjects was genotyped for NPSR and assessed for AS, childhood maltreatment (CTQ) and recent life events (LTE). Influences on AS and its subdimensions were determined by a step-wise hierarchical regression and a multiple indicator multiple cause (MIMIC) model. Results. Significant main effects of NPSR and CTQ as well as significant G × E were observed, with T/T homozygosity and a high CTQ score resulting in increased anxiety sensitivity. MIMIC modelling yielded association of AS subfactor “concern about mental/cognitive incapacitation” and the basal somatic subdimension “concern about physical sensations” to be associated with CTQ and its interaction with NPSR, while the acute somatic subfactor “concern about heart/lung failure” was associated with NPSR and its interaction with LTE. Conclusions. Results indicate G × E effects of the more active NPSR rs324981 T allele and life events on AS with differential effects of temporally proximal and distal factors on specific AS subdimensions.

Epigenetic signature of panic disorder: A role of glutamate decarboxylase 1 (GAD1) DNA hypomethylation?

Glutamate decarboxylases (GAD67/65; GAD1/GAD2) are crucially involved in gamma-aminobutyric acid (GABA) synthesis and thus were repeatedly suggested to play an important role in the pathogenesis of anxiety disorders. In the present study, DNA methylation patterns in the GAD1 and GAD2 promoter and GAD1 intron 2 regions were investigated for association with panic disorder, with particular attention to possible effects of environmental factors. Sixty-five patients with panic disorder (f=44, m=21) and 65 matched healthy controls were analyzed for DNA methylation status at 38 GAD1 promoter/intron2 and 10 GAD2 promoter CpG sites via direct sequencing of sodium bisulfate treated DNA extracted from blood cells. Recent positive and negative life events were ascertained. Patients and controls were genotyped for GAD1 rs3762556, rs3791878 and rs3762555, all of which are located in the analyzed promoter region. Patients with panic disorder exhibited significantly lower average GAD1 methylation than healthy controls (p<0.001), particularly at three CpG sites in the promoter as well as in intron 2. The occurrence of negative life events was correlated with relatively decreased average methylation mainly in the female subsample (p=0.01). GAD1 SNP rs3762555 conferred a significantly lower methylation at three GAD1 intron 2 CpG sites (p<0.001). No differential methylation was observed in the GAD2 gene. The present pilot data suggest a potentially compensatory role of GAD1 gene hypomethylation in panic disorder possibly mediating the influence of negative life events and depending on genetic variation. Future studies are warranted to replicate the present finding in independent samples, preferably in a longitudinal design.

Allelic variation in CRHR1 predisposes to panic disorder: evidence for biased fear processing.

Corticotropin-releasing hormone (CRH) is a major regulator of the hypothalamic–pituitary–adrenal axis. Binding to its receptor CRHR1 triggers the downstream release of the stress response-regulating hormone cortisol. Biochemical, behavioral and genetic studies revealed CRHR1 as a possible candidate gene for mood and anxiety disorders. Here we aimed to evaluate CRHR1 as a risk factor for panic disorder (PD). Allelic variation of CRHR1 was captured by 9 single-nucleotide polymorphisms (SNPs), which were genotyped in 531 matched case/control pairs. Four SNPs were found to be associated with PD, in at least one sub-sample. The minor allele of rs17689918 was found to significantly increase risk for PD in females after Bonferroni correction and furthermore decreased CRHR1 mRNA expression in human forebrains and amygdalae. When investigating neural correlates underlying this association in patients with PD using functional magnetic resonance imaging, risk allele carriers of rs17689918 showed aberrant differential conditioning predominantly in the bilateral prefrontal cortex and safety signal processing in the amygdalae, arguing for predominant generalization of fear and hence anxious apprehension. Additionally, the risk allele of rs17689918 led to less flight behavior during fear-provoking situations but rather increased anxious apprehension and went along with increased anxiety sensitivity. Thus reduced gene expression driven by CRHR1 risk allele leads to a phenotype characterized by fear sensitization and hence sustained fear. These results strengthen the role of CRHR1 in PD and clarify the mechanisms by which genetic variation in CRHR1 is linked to this disorder.