Polymorphisms in the serotonin receptor gene HTR2A are associated with quantitative traits in panic disorder

Neurotransmitter Gene Polymorphisms Are Associated with Symptom Clusters in Patients Undergoing Radiation Therapy

OBJECTIVES

Purpose was to evaluate for associations between the severity of three distinct symptom clusters (ie, sickness-behavior, mood-cognitive, treatment-related) and polymorphisms for 16 genes involved in catecholaminergic, GABAergic, and serotonergic neurotransmission.

DATA SOURCES

Patients with breast and prostate cancer (n = 157) completed study questionnaires at the completion of radiation therapy. Memorial Symptom Assessment Scale was used to assess the severity of 32 common symptoms. Three distinct symptom clusters were identified using exploratory factor analysis. Associations between the symptom cluster severity scores and neurotransmitter gene polymorphisms were evaluated using regression analyses.

CONCLUSION

Severity scores for the sickness-behavior symptom cluster were associated with polymorphisms for solute carrier family 6 (SLC6A) member 2 (SLC6A2), SLC6A3, SLC6A1, and 5-hydroxytryptamine receptor (HTR) 2A (HTR2A) genes. For the mood-cognitive symptom cluster, severity scores were associated with polymorphisms for adrenoreceptor alpha 1D, SLC6A2, SLC6A3, SLC6A1, HTR2A, and HTR3A. Severity scores for the treatment-related symptom cluster were associated with polymorphisms for SLC6A2, SLC6A3, catechol-o-methyltransferase, SLC6A1, HTR2A, SLC6A4, and tryptophan hydroxylase 2.

IMPLICATIONS FOR NURSING PRACTICE

Findings suggest that polymorphisms for several neurotransmitter genes are involved in the severity of sickness-behavior, mood-cognitive, and treatment-related symptom clusters in oncology patients at the completion of radiation therapy. Four genes with various associated polymorphisms were common across the three distinct symptom clusters (ie, SLC6A2, SLC6A3, SLC6A1, HTR2A) which suggest that these clusters have common underlying mechanisms.

Association of GABRG3, GABRB3, HTR2A Gene Variants with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental and neurobehavioral disorder characterized by impaired social communication, repetitive and restricted patterns of behavior, activity, or interest, and altered emotional processing. Reported prevalence is 4 times higher in men and it has increased in recent years. Immunological, environmental, epigenetic, and genetic factors play a role in the pathophysiology of autism. Many neurochemical pathways and neuroanatomical events are effective in determining the disease. It is still unclear how the main symptoms of autism occur because of this complex and heterogeneous situation. In this study, we focused on gamma amino butyric acid (GABA) and serotonin, which are thought to contribute to the etiology of autism; it is aimed to elucidate the mechanism of the disease by investigating variant changes in the GABA receptor subunit genes GABRB3, GABRG3 and the HTR2A gene, which encodes one of the serotonin receptors. 200 patients with ASD between the ages of 3-9 and 100 healthy volunteers were included in the study. Genomic DNA isolation was performed from peripheral blood samples taken from volunteers. Genotyping was performed using the RFLP method with PCR specific for specific variants. Data were analyzed with SPSS v25.0 program. According to the data obtained in our study; In terms of HTR2A (rs6313 T102C) genotypes, the homozygous C genotype carrying frequency in the patient group and the homozygous T genotype carrying frequency in the GABRG3 (rs140679 C/T) genotypes were found to be significantly higher in the patient group compared to the control group (*p: 0.0001, p: 0.0001). It was determined that the frequency of individuals with homozygous genotype was significantly higher in the patient group compared to the control group and having homozygous genotypes increased the disease risk approximately 1.8 times. In terms of GABRB3 (rs2081648 T/C) genotypes, it was determined that there was no statistically significant difference in the frequency of carrying homozygous C genotype in the patient group compared to the control group (p: 0.36). According to the results of our study, we think that the HTR2A (rs6313 T102C) polymorphism is effective in modulating the empathic and autistic characteristics of individuals, and that the HTR2A (rs6313 T102C) polymorphism is more distributed in the post-synaptic membranes in individuals with a higher number of C alleles. We believe that this situation can be attributed to the spontaneous stimulatory distribution of the HTR2A gene in the postsynaptic membranes because of T102C transformation. In genetically based autism cases, carrying the point mutation in the rs6313 variant of the HTR2A gene and the C allele and the point mutation in the rs140679 variant of the GABRG3 gene and accordingly carrying the T allele provide a predisposition to the disease.

Biological and cognitive theories explaining panic disorder: A narrative review

The current narrative review summarizes and examines several theories of panic disorder (PD) including biological theories, encompassing neurochemical factors, metabolic and genetic theories, respiratory and hyperventilation theories and cognitive theory. Biological theories have informed the development of psychopharmacological treatments; however, they may be limited in their utility given the efficacy of psychological treatments. In particular, behavioral and, more recently, cognitive models have garnered support due to the efficacy of cognitive-behavior therapy (CBT) in treating PD. The role of combination treatments has been found to be superior in the treatment of PD in particular cases, lending support for the need for an integrated approach and model for PD given that the etiology of PD is complex and multifactorial.

Polymorphisms of the serotonin receptors genes in patients with bruxism: a systematic review

This study aimed to investigate if SNP rs6313, SNP rs2770304, SNP rs4941573, and SNP rs1923884 of the 5-HT2A receptor gene and SNP rs6295 of the 5-HT1A receptor gene are associated with bruxism etiology.

METHODOLOGY

This systematic review was registered in PROSPERO (CRD42018094561). A search was conducted for articles published in or before May 2021. To qualify for eligibility in this review, the studies had to be case-controls, cohort or cross-sectional. The inclusion criteria were the articles with a group of patients with bruxism and a control group in which the presence of these SNPs was evaluated. The exclusion criteria were the investigations of other polymorphisms, the studies that did not consider a control group for comparison, case reports, and reviews. The NOS and JBI were used to evaluate the methodological quality of studies.

RESULTS

We conducted this study with databases, such as Web of Science, Scopus, Embase, PubMed/MEDLINE, and ProQuest. We considered four studies eligible. A total of 672 participants were included,187 with sleep bruxism, 105 with awake bruxism, 89 with sleep and awake bruxism, and 291 controls. One study found a strong association between the SNPs rs6313, rs2770304 and rs4941573 of the 5-HT2A receptor gene and sleep bruxism. In one study, we considered the C allele of the SNP rs2770304 a risk factor for sleep bruxism. We found no significant results of other SNPs in sleep bruxers compared to controls. We found no positive association concerning the SNPs and groups of awake bruxism and sleep and awake bruxism.

CONCLUSION

The different results regarding the SNPs in sleep bruxers could be explained by the genetic distinction between Chilean, Mexican, Japanese, and Polish population. More clinical trials and prospective studies must be conducted with larger sample size and in different ethnicities to confirm the results of this review.

The role of pharmacogenetics in the treatment of anxiety disorders and the future potential for targeted therapeutics

INTRODUCTION

Anxiety disorders (AD) are among the most common mental disorders worldwide. Pharmacotherapy, including benzodiazepines, selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, and tricyclic antidepressants is currently based on 'trial-and-error,' and is effective in a subset of patients or produces partial response only. Recent research proposes that treatment response and tolerability of the drugs are associated with genetic factors.

AREAS COVERED

In the present review, we provide information on pharmacogenetics (PGx) in AD, including pharmacokinetic and pharmacodynamic genes. Moreover, we discuss the future potential of PGx for personalized treatment.

EXPERT OPINION

In psychiatry, PGx testing is still in its infancy, especially in the treatment of AD. As of today, implementation in clinical routine is recommended only for CYP2D6 and CYP2C19, mainly in terms of safety of treatment and potentially of treatment outcome in general. However, the evidence for PGx testing addressing pharmacodynamics for specific AD is limited to date. Nevertheless, PGx may develop into a valuable and promising tool to improve therapy in AD, but there is a need for more research to fully exploit its possibilities. Future perspectives include research into single genes, polygenic risk scores, and pharmacoepigenetics to provide targeted therapy.

Serotonergic receptor gene polymorphism and response to selective serotonin reuptake inhibitors in ethnic Malay patients with first episode of major depressive disorder

The polymorphisms of the 5HTR1A and 5HTR2A receptor genes (rs6295C/G and rs6311G/A) have been evaluated for association with SSRI treatment outcome in various populations with different results. The present study was carried out to determine the association between genotypes of HTR1A-rs6295 and HTR2A-rs6311 with SSRI treatment outcome among the ethnic Malay patients diagnosed with first-episode major depressive disorder (MDD). The patients were recruited from four tertiary hospitals in the Klang Valley region of Malaysia. Predefined efficacy phenotypes based on 25% (partial early response) and 50% (clinical efficacy response) reduction in Montgomery Asberg Depression Rating Scale-self Rated score (MADRS-S) were adopted for assessment of treatment efficacy in this study. Self-reporting for adverse effects (AE) was documented using the Patient Rated Inventory of Side Effect (PRISE) after treatment with SSRI for up to 6 weeks. Adjusted binary logistic regression between genotypes of the polymorphism obtained using sequencing technique with the treatment outcome phenotypes was performed. The 142 patients recruited were made up of 96 females (67.6%) and 46 males (32.4%). Clinical efficacy and Partial early response phenotypes were not significantly associated with genotypes of HTR1A and HTR2A polymorphism. The GG genotype of HTR2A polymorphism has decreased odds for dizziness (CNS) and increased odds for poor concentration. The GA genotype increases the odd for excessive sweating, diarrhoea, constipation and blurred vision. The CC genotype of HTR1A-rs6295 decreases the odd for nausea/vomiting and increases the odd for anxiety. Thus, some genotypes of HTR1A and HTR2A polymorphism were associated with SSRI treatment outcomes in ethnic Malay MDD patients.

In vitro monitoring of HTR2A-positive neurons derived from human-induced pluripotent stem cells

The serotonin 5-HT_2A receptor (5-HT_2AR) has been receiving increasing attention because its genetic variants have been associated with a variety of neurological diseases. To elucidate the pathogenesis of the neurological diseases associated with 5-HT_2AR gene (HTR2A) variants, we have previously established a protocol to induce HTR2A-expressing neurons from human-induced pluripotent stem cells (hiPSCs). Here, we investigated the maturation stages and electrophysiological properties of HTR2A-positive neurons induced from hiPSCs and constructed an HTR2A promoter-specific reporter lentivirus to label the neurons. We found that neuronal maturity increased over time and that HTR2A expression was induced at the late stage of neuronal maturation. Furthermore, we demonstrated successful labelling of the HTR2A-positive neurons, which had fluorescence and generated repetitive action potentials in response to depolarizing currents and an inward current during the application of TCB-2, a selective agonist of 5-HT_2ARs, respectively. These results indicated that our in vitro model mimicked the in vivo dynamics of 5-HT_2AR. Therefore, in vitro monitoring of the function of HTR2A-positive neurons induced from hiPSCs could help elucidate the pathophysiological mechanisms of neurological diseases associated with genetic variations of the HTR2A gene.

Association between autism spectrum disorder and polymorphisms in genes encoding serotine and dopamine receptors

Dysfunctions of the neurotransmitter system are related to the development of many psychological diseases including autism spectrum disorder (ASD). Single nucleotide polymorphisms (SNPs) are correlated with varied susceptibility of ASD and response to treatments. The association between SNPs in genes encoding serotonin and dopamine receptors and childhood ASD was examined in a Chinese Han population. Both autistic children (n = 319) and age-and gender-matched healthy controls (n = 347) were recruited from a local district. Disease severity was evaluated by the childhood autism rating scale (CARS). SNPs of rs6311 and rs6313 in the serotonin receptor HTR2A gene, rs4630328 in the dopamine receptor D2 (DRD2) gene and rs167771 in the DRD3 gene were examined. The CC genotype of rs6311 was significantly associated with an increased risk of ASD (odds ratio (OD) = 1.8 vs TT, 95% confidence interval (CI): 1.2-2.8, P = 0.0085). Carriers of the C allele of rs6311 had a significantly higher risk of childhood ASD (OD =1.3, 95% CI = 1.1-1.7, P = 0.0094). A strong linkage disequilibrium was observed between rs6311 and rs6313 (D' = 0.93, r² = 0.86). There were significant correlations between haplotypes (T-A and C-G of rs6311-rs6313) and risk of childhood ASD. In contrast, the frequencies of genotypes and alleles of rs6313, rs4630328 and rs167771 were not significantly different between the case and control groups. All the SNPs examined were not associated with severity of the disease. Our study demonstrates that certain SNPs in the HTR2A gene, but not the DRD2 and DRD3, are associated with susceptibility to childhood ASD.

Genetic Biomarkers of Panic Disorder: A Systematic Review

(1) Background: Although panic disorder (PD) is one of the most common anxiety disorders severely impacting quality of life, no effective genetic testing exists; known data on possible genetic biomarkers is often scattered and unsystematic which complicates further studies. (2) Methods: We used PathwayStudio 12.3 (Elsevier, The Netherlands) to acquire literature data for further manual review and analysis. 229 articles were extracted, 55 articles reporting associations, and 32 articles reporting no associations were finally selected. (3) Results: We provide exhaustive information on genetic biomarkers associated with PD known in the scientific literature. Data is presented in two tables. Genes COMT and SLC6A4 may be considered the most promising for PD diagnostic to date. (4) Conclusions: This review illustrates current progress in association studies of PD and may indicate possible molecular mechanisms of its pathogenesis. This is a possible basis for data analysis, novel experimental studies, or developing test systems and personalized treatment approaches.

The neuropharmacology of sleep paralysis hallucinations: serotonin 2A activation and a novel therapeutic drug

Sleep paralysis is a state of involuntary immobility occurring at sleep onset or offset, often accompanied by uncanny "ghost-like" hallucinations and extreme fear reactions. I provide here a neuropharmacological account for these hallucinatory experiences by evoking the role of the serotonin 2A receptor (5-HT2AR). Research has shown that 5-HT2AR activation can induce visual hallucinations, "mystical" subjective states, and out-of-body experiences (OBEs), and modulate fear circuits. Hallucinatory experiences triggered by serotonin-serotonergic ("pseudo") hallucinations, induced by hallucinogenic drugs-tend to be "dream-like" with the experiencer having insight ("meta-awareness") that he is hallucinating, unlike dopaminergic ("psychotic" and "life-like") hallucinations where such insight is lost. Indeed, hallucinatory experiences during sleep paralysis have the classic features of serotonergic hallucinations, and are strikingly similar to perceptual and subjective states induced by hallucinogenic drugs (e.g., lysergic acid diethylamide [LSD] and psilocybin), i.e., they entail visual hallucinations, mystical experiences, OBEs, and extreme fear reactions. I propose a possible mechanism whereby serotonin could be functionally implicated in generating sleep paralysis hallucinations and fear reactions through 5-HT2AR activity. Moreover, I speculate on the role of 5-HT2C receptors vis-à-vis anxiety and panic during sleep paralysis, and the orbitofrontal cortex-rich with 5-HT2A receptors-in influencing visual pathways during sleep paralysis, and, in effect, hallucinations. Finally, I propose, for the first time, a drug to target sleep paralysis hallucinations and fear reactions, namely the selective 5-HT2AR inverse agonist, pimavanserin. This account implicates gene HTR2A on chromosome 13q as the underlying cause of sleep paralysis hallucinations and could be explored using positron emission tomography.

"DNA Methylation signatures in panic disorder"

Panic disorder (PD) affects about four million Europeans, with women affected twice as likely as men, causing substantial suffering and high economic costs. The etiopathogenesis of PD remains largely unknown, but both genetic and environmental factors contribute to risk. An epigenome-wide association study (EWAS) was conducted to compare medication-free PD patients (n = 89) with healthy controls (n = 76) stratified by gender. Replication was sought in an independent sample (131 cases, 169 controls) and functional analyses were conducted in a third sample (N = 71). DNA methylation was assessed in whole blood using the Infinium HumanMethylation450 BeadChip. One genome-wide association surviving FDR of 5% (cg07308824, P = 1.094 × 10-7, P-adj = 0.046) was identified in female PD patients (N = 49) compared to controls (N = 48). The same locus, located in an enhancer region of the HECA gene, was also hypermethylated in female PD patients in the replication sample (P = 0.035) and the significance of the association improved in the meta-analysis (P-adj = 0.004). Methylation at this CpG site was associated with HECA mRNA expression in another independent female sample (N = 71) both at baseline (P = 0.046) and after induction by dexamethasone (P = 0.029). Of 15 candidates, 5 previously reported as associated with PD or anxiety traits also showed differences in DNA methylation after gene-wise correction and included SGK1, FHIT, ADCYAP1, HTR1A, HTR2A. Our study examines epigenome-wide differences in peripheral blood for PD patients. Our results point to possible sex-specific methylation changes in the HECA gene for PD but overall highlight that this disorder is not associated with extensive changes in DNA methylation in peripheral blood.

Genetic Correlates of Spirituality/Religion and Depression: A Study in Offspring and Grandchildren at High and Low Familial Risk for Depression

RATIONALE

Possible genetic correlates of spirituality and depression have been identified in community samples. We investigate some of the previously identified candidates in a sample of families at both high and low-risk for depression.

METHOD

Offspring and grandchildren of individuals at high and low-risk for depression, participating in a multi-wave thirty-year longitudinal study, were assessed for seven SNPS drawn from four single gene candidates associated with systems implicated in both depression and spirituality: Serotonin (5-HT1B and 5-HT2A), Dopamine (DRD2), Oxytocin (OT) and Monoamine Vesicular Transporter (VMAT1).

RESULTS

Dopamine (DRD2) Serotonin (5-HT1B), their Transporter (VMAT1) and Oxytocin (OXTR) were positively associated with a high level of importance of spirituality or religion (S/R) in the group at low familial risk for depression. DRD2 minor allele was associated with both lifetime major depressive disorder (MDD) and spirituality in the low-risk group for depression. No SNPs were related to S/R in the group at high familial risk for depression. OXTR was associated with lifetime MDD in the full sample.

CONCLUSION

Genes for dopamine, serotonin, their vesicular transporter, and oxytocin may be associated with S/R in people at low familial risk for depression. Genes for dopamine may be associated both with S/R and increased risk for depression in people at low-risk for depression, suggesting a common pathway or physiology to mild to moderate depression. MDD is associated with oxytocin across risk groups. In the high-risk group, phenotypic expression of S/R may be suppressed.

IMPLICATIONS

The shared association of DRD2 by S/R and depression, generally found to be inversely related, calls for further research on their common physiological pathways, and the phenotypic expression of these pathways based upon use and environment. Prevention for offspring at high familial risk for depression might include support for the development of child spirituality.

Candidate genes in panic disorder: meta-analyses of 23 common variants in major anxiogenic pathways

The utilization of molecular genetics approaches in examination of panic disorder (PD) has implicated several variants as potential susceptibility factors for panicogenesis. However, the identification of robust PD susceptibility genes has been complicated by phenotypic diversity, underpowered association studies and ancestry-specific effects. In the present study, we performed a succinct review of case-control association studies published prior to April 2015. Meta-analyses were performed for candidate gene variants examined in at least three studies using the Cochrane Mantel-Haenszel fixed-effect model. Secondary analyses were also performed to assess the influences of sex, agoraphobia co-morbidity and ancestry-specific effects on panicogenesis. Meta-analyses were performed on 23 variants in 20 PD candidate genes. Significant associations after correction for multiple testing were observed for three variants, TMEM132D rs7370927 (T allele: odds ratio (OR)=1.27, 95% confidence interval (CI): 1.15-1.40, P=2.49 × 10(-6)), rs11060369 (CC genotype: OR=0.65, 95% CI: 0.53-0.79, P=1.81 × 10(-5)) and COMT rs4680 (Val (G) allele: OR=1.27, 95% CI: 1.14-1.42, P=2.49 × 10(-5)) in studies with samples of European ancestry. Nominal associations that did not survive correction for multiple testing were observed for NPSR1 rs324891 (T allele: OR=1.22, 95% CI: 1.07-1.38, P=0.002), TPH1 rs1800532 (AA genotype: OR=1.46, 95% CI: 1.14-1.89, P=0.003) and HTR2A rs6313 (T allele: OR=1.19, 95% CI: 1.07-1.33, P=0.002) in studies with samples of European ancestry and for MAOA-uVNTR in female PD (low-active alleles: OR=1.21, 95% CI: 1.07-1.38, P=0.004). No significant associations were observed in the secondary analyses considering sex, agoraphobia co-morbidity and studies with samples of Asian ancestry. Although these findings highlight a few associations, PD likely involves genetic variation in a multitude of biological pathways that is diverse among populations. Future studies must incorporate larger sample sizes and genome-wide approaches to further quantify the observed genetic variation among populations and subphenotypes of PD.

Serotonin receptor gene (HTR2A) T102C polymorphism modulates individuals' perspective taking ability and autistic-like traits

Previous studies have indicated that empathic traits, such as perspective taking, are associated with the levels of serotonin in the brain and with autism spectrum conditions. Inspired by the finding that the serotonin receptor 2A gene (HTR2A) modulates the availability of serotonin, this study investigated to what extent HTR2A modulates individuals’ perspective taking ability and autistic-like traits. To examine the associations of the functional HTR2A polymorphism T102C (rs6313) with individuals’ perspective taking abilities and autistic-like traits, we differentiated individuals according to this polymorphism and measured empathic and autistic-like traits with Interpersonal Reactivity Index (IRI) and Autism-Spectrum Quotient (AQ) scale in 523 Chinese people. The results indicated that this polymorphism was significantly associated with the scores on Perspective Taking and Personal Distress subscales of IRI, and Communication subscale of AQ. Individuals with a greater number of the C alleles were less likely to spontaneously adopt the point of view of others, more likely to be anxious when observing the pain endured by others, and more likely to have communication problems. Moreover, the genotype effect on communication problems was mediated by individuals’ perspective taking ability. These findings provide evidence that the HTR2A T102C polymorphism is a predictor of individual differences in empathic and autistic-like traits and highlight the role of the gene in the connection between perspective taking and autistic-like traits.

Evidence for Association between the Brain-Derived Neurotrophic Factor Gene and Panic Disorder: A Novel Haplotype Analysis

OBJECTIVE

Panic disorder (PD) is a common psychiatric disorder with a complex etiology, and several studies have suggested that it has a genetic component. Brain-derived neurotrophic factor (BDNF) is the most abundant of the neurotrophins in the brain and is recognized for its important role in the survival, differentiation and growth of neurons. Several lines of research have suggested possible associations between the BDNF gene and PD. In this study, we investigated the BDNF 196G/A (rs6265), 11757G/C (rs16917204), and 270C/T (rs56164415) single nucleotide polymorphisms (SNPs) in order to determine an association with PD. We also identified the genetic sequence associations with PD via haplotype analysis.

METHODS

Participants in this study included 136 PD patients and 263 healthy controls. Male and female subjects were analyzed separately. The genotype and allele frequencies of the PD patients and controls were analyzed using χ(2) statistics. Frequencies and haplotype reconstructions were calculated using the SNP analyzer 2.0.

RESULTS

We found no significant statistical differences in the genotype distributions or allele frequencies of the three tested polymorphisms between the PD and control groups. In addition, no differences were found between PD patients and the controls in either male or female subgroups. However, we found that, the frequency of the G-C haplotype for 196G/A and 11757G/C was significantly higher in PD patients than in the controls.

CONCLUSION

Our result suggest that patients with the G-C haplotype for 196G/A and 11757G/C may be more susceptible to the development of PD. Further studies are needed to replicate the associations that we observed.

Associations between catecholaminergic, GABAergic, and serotonergic genes and self-reported attentional function in oncology patients and their family caregivers

PURPOSE OF THE RESEARCH

Evaluate for associations between variations in genes involved in catecholaminergic, gamma-aminobutyric acid (GABA)-ergic, and serotonergic mechanisms of neurotransmission and attentional function latent classes.

PATIENTS AND METHODS

This descriptive, longitudinal study was conducted at two radiation therapy departments. The sample included three latent classes of individuals with distinct trajectories of self-reported attentional function during radiation therapy, who were previously identified using growth mixture modeling among 167 oncology patients and 85 of their family caregivers. Multivariable models were used to evaluate for genotypic associations of neurotransmission genes with attentional function latent class membership, after controlling for covariates.

RESULTS

Variations in catecholaminergic (i.e., ADRA1D rs4815675, SLC6A3 rs37022), GABAergic (i.e., SLC6A1 rs2697138), and serotonergic (i.e., HTR2A rs2296972, rs9534496) neurotransmission genes were significant predictors of latent class membership in multivariable models.

CONCLUSIONS

Findings suggest that variations in genes that encode for three distinct but related neurotransmission systems are involved in alterations in attentional function. Knowledge of both phenotypic and genetic markers associated with alterations in attentional function can be used by clinicians to identify patients and family caregivers who are at higher risk for this symptom. Increased understanding of the genetic markers associated with alterations in attentional function may provide insights into the underlying mechanisms for this significant clinical problem.

Neurobehavioral characterization of Endonuclease G knockout mice reveals a new putative molecular player in the regulation of anxiety

Endonuclease G (EndoG) has been largely related with a role in the modulation of a caspase-independent cell death pathway in many cellular systems. However, whether this protein plays a specific role in the brain remains to be elucidated. Here we have characterized the behavioral phenotype of EndoG(-/-) null mice and the expression of the nuclease among brain regions. EndoG(-/-) mice showed normal neurological function, learning, motor coordination and spontaneous behaviors. However, these animals displayed lower activity in a running wheel and, strikingly, they were consistently less anxious compared to EndoG(+/+) mice in different tests for anxiety such as plus maze and dark-light test. We next evaluated the expression of EndoG in different brain regions of wild type mice and found that it was expressed in all over but specially enriched in the striatum. Further, subcellular biochemical experiments in neocortical samples from wild type mice revealed that EndoG is localized in pre-synaptic compartments but not in post-synaptic compartments. Altogether these findings suggest that EndoG could play a highly specific role in the regulation of anxiety by modulating synaptic components.

A survey of putative anxiety-associated genes in panic disorder patients with and without bladder symptoms

BACKGROUND

We have previously described a subtype of panic disorder (PD) that we termed 'bladder syndrome', characterized by urological and bladder symptoms (and possibly interstitial cystitis) in the patients and/or their family members and confirmed the validity of this subset in family linkage and association analysis. In this study, we determine (a) whether 20 single-nucleotide polymorphisms (SNPs) reported in the literature can be replicated in a new PD dataset and (b) whether dividing the sample into those with and without the 'bladder syndrome' can help to resolve the genetic heterogeneity within this new sample.

METHODS

We selected 20 putative associated SNPs from the literature, taken from studies published since 2004. We tested these SNPs for association in a sample of 351 PD patients and 552 controls, and then divided them into subgroups of 92 patients from bladder families and 259 from nonbladder families.

RESULTS

(a) When analyzed in all PD patients, none of the 20 SNPs appeared to be replicated (except for SLC6A4 from our previous study, but in a sample that overlaps substantially with that in our previous report). (b) However, some intriguing findings emerged when we separated bladder from nonbladder families: SLC6A4, reported by us previously, yielded stronger evidence than before (P=0.0018) when examined only in nonbladder families, and in contrast, is not statistically significant in bladder families. Two other markers yielded nominally significant results in bladder families - rs5751876 in ADORA2A (P=0.046) and rs12579350 in TMEM16B (P=0.035) - but were not significant in nonbladder families. (c) Two markers had noticeably lower P-values when we differentiated the women and analyzed them separately - rs12579350 in TMEM16B (P-value decreased from 0.035, as above, to 0.00055) and a different SNP in ADORA2A, rs4822492 (P-value decreases from 0.07 to 0.028).

SIGNIFICANCE

Our results indicate that most of the 20 reported associations do not hold up when PD is analyzed as one group. However, our findings provide further evidence that PD with bladder symptoms may be genetically different from PD without bladder. We suggest that it is worth pursuing SLC6A4 in nonbladder PD, and ADORA2A and TMEM16B in bladder PD. Also, the possibility of a male-female difference in PD is worth pursuing. We also briefly discuss issues of replication and multiple tests.

HTR2A gene polymorphisms and Inward and Outward Personal Meaning Organisations

Nardi B, Piva F, Turchi C, Giulietti M, Castellucci G, Arimatea E, Rocchetti D, Rocchetti G, Principato G, Tagliabracci A, Bellantuono C. HTR2A gene polymorphisms and Inward and Outward Personal Meaning Organisations.

Objective:Caregiver behaviours and emotional expressions may induce development of two basic categories of constructing identity and of regulating cognitive and emotional processes: an Inward or an Outward Personal Meaning Organisation (PMO). Inwards read environmental signals through their internal activations. Their emotions are more distinct, and reciprocity is more based on physical distance (protection, loneliness). Outwards read internal activations through the environment. Their emotions are more blurred, and reciprocity is more based on a semantic sight of relations (approval, rules).

It has recently been shown that PMO development may also have physiological and genetic bases. In a functional magnetic resonance imaging (fMRI) study, Inward and Outward subjects showed different amygdala activation patterns and an association with the SLC6A4 serotonin transporter gene 5-HTTLPR polymorphism.

Methods:In this work, 149 healthy subjects were examined with respect to Inward and Outward PMOs. We explored the association with 10 serotonin receptor 2A (HTR2A) gene single nucleotide polymorphisms (SNPs) selected by bioinformatics methods.

Results:An intronic SNP (rs55948462) was found to be significantly associated with an Inward and an Outward PMOs development. However, after statistical adjustments, these results did not remain significant.

Conclusion:We did not find associations between considered SNPs and Inward/Outward PMOs. However, the role of HTR2A polymorphisms was not considered in this study and that of the other serotonin-related genes should be valued.

A preliminary examination of how serotonergic polymorphisms influence brain response following an adolescent cannabis intervention

Given the link between depression, anxiety, and cannabis abuse, a serotonin receptor (rs6311) and transporter polymorphism (rs2020936) were examined as moderators of neural response as measured by functional magnetic resonance imaging following a psychosocial treatment for cannabis use disorders (CUDs). While the proposed hypotheses were unsupported, we found that the rs6311 C allele was significantly related to brain activation (medial frontal gyrus, precuneus), indicating the role of this serotonin receptor in adolescent treatment response.

Potential role of cortical 5-HT(2A) receptors in the anxiolytic action of cyamemazine in benzodiazepine withdrawal

The antipsychotic cyamemazine is a potent serotonin 5-HT(2A) receptor (5-HT(2AR)) antagonist. A positron emission tomography (PET) study in human patients showed that therapeutic doses of cyamemazine produced near saturation of 5-HT(2AR) occupancy in the frontal cortex, whereas dopamine D(2) occupancy remained below the level for motor side effects observed with typical antipsychotics. Recently, numerous studies have revealed the involvement of 5-HT(2AR) in the pathophysiology of anxiety and a double-blind, randomized clinical trial showed similar efficacy of cyamemazine and bromazepam in reducing the anxiety associated with benzodiazepine withdrawal. Therefore, we reviewed the above articles about 5-HT(2AR) and anxiety in order to understand better the anxiolytic mechanisms of cyamemazine in benzodiazepine withdrawal. The 5-HT(2AR) is the most abundant serotonin receptor subtype in the cortex. Non-pharmacological studies with antisense oligodeoxynucleotides and genetically modified mice clearly showed that cortical 5-HT(2AR) signaling positively modulates anxiety-like behavior. With a few exceptions, most other studies reviewed here further support this view. Therefore, the anxiolytic efficacy of cyamemazine in benzodiazepine withdrawal can be due to a 5-HT(2AR) antagonistic activity at the cortical level.

Support for involvement of glutamate decarboxylase 1 and neuropeptide Y in anxiety susceptibility

Genetic mapping efforts have identified putative susceptibility genes for human anxiety disorders. The most intensively studied genes are involved in neurotransmitter metabolism and signaling or stress response. In addition, neuropeptides and targets of anxiolytics have been examined. It has become apparent that gene × environment interactions may explain individual variation in stress resilience and predisposition to mental disorders. We aimed to replicate previous genetic findings in 16 putative anxiety susceptibility genes and further test whether they modulate the risk for developing an anxiety disorder in adulthood after childhood stress exposure. We tested 93 single-nucleotide polymorphisms (SNPs) for genetic association to anxiety disorders in the Finnish population-based Health 2000 sample (282 cases and 575 matched controls). In addition, we examined by logistic regression modeling whether the SNP genotypes modified the effect of the number of self-reported childhood adversities on anxiety disorder risk. The most significant evidence for association was observed in glutamate decarboxylase 1 (GAD1) with phobias (P = 0.0005). A subsequent meta-analysis (N = 1985) incorporating previously published findings supported involvement of a single GAD1 risk haplotype in determining susceptibility to a broad range of internalizing disorders (P = 0.0009). We additionally found that SNPs and haplotypes in neuropeptide Y (NPY) modified the effect of childhood adversities on anxiety susceptibility (P = 0.003). In conclusion, we provide further support for involvement of mainly GAD1, but also NPY in determining predisposition to anxiety disorders.

Serotonin 2A receptor, serotonin transporter and dopamine transporter alterations in dogs with compulsive behaviour as a promising model for human obsessive-compulsive disorder

Neuro-imaging studies have shown altered, yet often inconsistent, serotonergic and dopaminergic neurotransmission in patients with obsessive-compulsive disorder (OCD). We investigated both serotonergic and dopaminergic neurotransmission in 9 drug-naïve dogs with compulsive behaviour, as a potential model for human OCD. Single photon emission computed tomography was used with (123)I-R91150 and (123)I-FP-CIT, in combination with (99m)Tc-ECD brain perfusion co-registration, to measure the serotonin (5-HT) 2A receptor, dopamine transporter (DAT) and serotonin transporter (SERT) availability. Fifteen normally behaving dogs were used as reference group. Significantly lower 5-HT2A receptor radioligand availability in frontal and temporal cortices (bilateral) was observed. Further, in 78% of the compulsive dogs abnormal DAT ratios in left and right striatum were demonstrated. Interestingly, both increased and decreased DAT ratios were observed. Finally, significantly lower subcortical perfusion and (hypo)thalamic SERT availability were observed in the compulsive dogs. This study provides evidence for imbalanced serotonergic and dopaminergic pathways in the pathophysiology of compulsions in dogs. The similarities with the altered neurotransmission in human OCD provide construct validity for this non-induced, natural canine model, suggesting its usefulness for future investigations of the pathophysiology of human OCD as well as the effectiveness of psychopharmacological interventions.

Serotonin-2A receptor and catechol-O-methyltransferase polymorphisms in panic disorder

Catechol-O-methyltransferase (COMT) and serotonin receptor 2A (5HTR2A) polymorphisms have been investigated for their possible role in panic disorder (PD). The aim of this study was to investigate the genotype distribution of the COMT val158met and 5HTR2A 102T/C polymorphisms in PD. COMT val158met is a polymorphism at codon 158 that results in variations in COMT enzymatic activity with high- (H) and low-activity (L) alleles. The 5HTR2A 102T/C polymorphism comprises a T-to-C mutation at position 102. The effects of symptom severity, gender, and age of onset were also investigated. The participants were 105 outpatients with PD and 130 controls. The severity of the symptoms of PD was assessed by the Panic and Agoraphobia Scale (PAS). Polymorphisms of the 5HTR2A and COMT genes were identified using polymerase chain reaction and restriction fragment length polymorphism analysis. A significant relationship was found between the COMT Val158Met polymorphism and PD. No significant differences were found in genotype distributions or allele frequencies of the 5HTR2A polymorphisms between the PD and control groups. There were no significant relationships between the COMT and 5HTR2A polymorphisms and age of onset, gender, presence of agoraphobia, or PAS scores in the PD group (p>0.05).

Behavioral genetics of affective and anxiety disorders

As shown by clinical genetic studies, affective and anxiety disorders are complex genetic disorders with genetic and environmental factors interactively determining their respective pathomechanism. Advances in molecular genetic techniques including linkage studies, association studies, and genome-wide association studies allow for the detailed dissection of the genetic influence on the development of these disorders. Besides the molecular genetic investigation of categorical entities according to standardized diagnostic criteria, intermediate phenotypes comprising neurobiological or neuropsychological traits (e.g., neuronal correlates of emotional processing) that are linked to the disease of interest and that are heritable, have been proposed to be closer to the underlying genotype than the overall disease phenotype. These intermediate phenotypes are dimensional and more precisely defined than the categorical disease phenotype, and therefore have attracted much interest in the genetic investigation of affective and anxiety disorders. Given the complex genetic nature of affective and anxiety disorders with an interaction of multiple risk genes and environmental influences, the interplay of genetic factors with environmental factors is investigated by means of gene-environment interaction (GxE) studies. Pharmacogenetic studies aid in the dissection of the genetically influenced heterogeneity of psychotropic drug response and may contribute to the development of a more individualized treatment of affective and anxiety disorders. Finally, there is some evidence for genetic factors potentially shared between affective and anxiety disorders pointing to a possible overlapping phenotype between anxiety disorders and depression.

Influence of birth weight on internalizing traits modulated by serotonergic genes

OBJECTIVE

Fetal growth predicts childhood behavioral problems associated with brain serotonergic systems. We hypothesized that allelic variations in genes involved in serotonergic function would moderate associations between birth weight (BW) and internalizing traits in childhood.

METHODS

The Child Behavior Checklist was administered to 545 healthy Singaporean children at 8 to 12 years. BW, corrected for gestational age, and candidate single-nucleotide polymorphisms (SNPs) in the TPH2, HTR2A, and SCL6A4 genes were investigated.

RESULTS

There was no significant main effect of BW on internalizing T scores (F = 1.08; P = .36). After multiple corrections, significant main effects on internalizing T scores were found for HTR2A rs2296972 (adjusted: F = 2.85; P = .019) and HTR2A rs6313 (adjusted: F = 5.91; P = .0002). Significant interactions were found between BW and SNPs for the TPH2 gene (rs2171363: P = .008; rs7305115: P = .007) and the HTR2A gene (rs2770304: P = .001; rs6313: P = .026) for internalizing T scores. The CC genotype of TPH2 rs2171363, GG genotype of TPH2 rs7305115, CC genotype of HTR2A rs2770304, and CC genotype of HTR2A rs6313 were associated with reduced internalizing scores for children born in the quartile above the midpoint. No significant main effects or interactions were found for SCL6A4 SNPs.

CONCLUSIONS

These findings suggest that sequence variations in genes involved in serotonergic functions modulate relationships between BW and internalizing traits and might be candidates for plasticity mechanisms that determine individual differences in responses to environmental influences over the course of development.

Human microRNAs miR-22, miR-138-2, miR-148a, and miR-488 are associated with panic disorder and regulate several anxiety candidate genes and related pathways

BACKGROUND

The involvement of microRNAs (miRNAs) in neuronal differentiation and synaptic plasticity suggests a role for miRNAs in psychiatric disorders; association analyses and functional approaches were used to evaluate the implication of miRNAs in the susceptibility for panic disorder.

METHODS

Case-control studies for 712 single-nucleotide polymorphisms (SNPs) tagging 325 human miRNA regions were performed in 203 Spanish patients with panic disorder and 341 control subjects. A sample of 321 anxiety patients and 642 control subjects from Finland and 102 panic disorder patients and 829 control subjects from Estonia was used as a replica. Reporter-gene assays and miRNA overexpression experiments in neuroblastoma cells were used to functionally evaluate the spectrum of genes regulated by the associated miRNAs.

RESULTS

Two SNPs associated with panic disorder: rs6502892 tagging miR-22 (p < .0002), and rs11763020 tagging miR-339 (p < .00008). Other SNPs tagging miR-138-2, miR-488, miR-491, and miR-148a regions associated with different panic disorder phenotypes. Replication in the north-European sample supported several of these associations, although they did not pass correction for multiple testing. Functional studies revealed that miR-138-2, miR-148a, and miR-488 repress (30%-60%) several candidate genes for panic disorder--GABRA6, CCKBR and POMC, respectively--and that miR-22 regulates four other candidate genes: BDNF, HTR2C, MAOA, and RGS2. Transcriptome analysis of neuroblastoma cells transfected with miR-22 and miR-488 showed altered expression of a subset of predicted target genes for these miRNAs and of genes that might be affecting physiological pathways related to anxiety.

CONCLUSIONS

This work represents the first report of a possible implication of miRNAs in the etiology of panic disorder.

Genetics of panic disorder: focus on association studies and therapeutic perspectives

There is evidence for either genetic heterogeneity or complex inheritance with an interaction of environmental factors and multiple single genes in the etiology of panic disorder. Although linkage analyses of panic disorder have implicated several chromosomal regions including 1q, 2q, 4q, 7p, 9q, 12q, 13q, 15q and 22q, they so far have not been able to identify a major gene responsible for panic disorder. Several genes of classical candidate neurotransmitter systems have been reported to be associated with panic disorder. Genetic variation in genes of monoamine oxidase A, catechol-O-methyltransferase, adenosine receptor (ADORA2A) and cholecystokinin B receptor have been inconsistently replicated. There are multiple lines of evidence for highly relevant effects of gender and ethnicity. Future research strategies might focus on broad phenotypes defined by comorbidity or intermediate phenotypes and include the use of animal models for identifying candidate genes, such as the regulator of G-protein signaling (RGS2) gene, genome-wide association studies in large samples, studies of gene-gene and gene-environment interactions and pharmacogenetic studies. The identification of novel pathophysiological pathways may provide the basis for the development of novel therapeutic interventions.

Multiple anxiogenic drugs recruit a parvalbumin-containing subpopulation of GABAergic interneurons in the basolateral amygdala

The basolateral amygdala is a nodal structure within a distributed and interconnected network that regulates anxiety states and anxiety-related behavior. Administration of multiple anxiogenic drugs increases cellular responses (i.e., increases c-Fos expression) in a subregion of the basolateral amygdala, but the neurochemical phenotypes of these cells are not known. The basolateral amygdala contains glutamatergic projection neurons and several populations of γ-aminobutyric acid-synthesizing (GABAergic) interneurons, including a population of parvalbumin (PV)-expressing GABAergic interneurons that co-express the excitatory 5-HT(2A) receptor. The role for these PV-expressing GABAergic interneurons in anxiety-states is unclear. In this experiment we examined the effects of multiple anxiogenic drugs including the 5-HT(2C/2A) receptor agonist m-chlorophenyl piperazine (mCPP), the adenosine receptor antagonist caffeine, the α(2)-adrenoreceptor antagonist yohimbine and the partial inverse agonist at the benzodiazepine allosteric site on the GABA(A) receptor, N-methyl-beta-carboline-3-carboxamide (FG-7142), on c-Fos expression in PV-immunoreactive (PV-ir) interneurons in subdivisions of the basolateral amygdala. All drugs with the exception of mCPP increased c-Fos expression in PV-ir neurons in the basolateral amygdaloid nucleus, anterior part (BLA). The numbers of c-Fos-immunoreactive (c-Fos-ir)/PV-ir GABAergic interneurons in the BLA were positively correlated with the numbers of c-Fos-ir serotonergic neurons in the mid-rostrocaudal dorsal raphe nucleus (DR) and with a measure of anxiety-related behavior. All four drugs increased c-Fos expression in non-PV-ir cells in most of the subdivisions of the basolateral amygdala that were sampled, compared with vehicle-injected controls. Together, these data suggest that the PV/5-HT(2A) receptor expressing GABAergic interneurons in the basolateral amygdala are part of a DR-basolateral amygdala neuronal circuit modulating anxiety-states and anxiety-related behavior.

Advances in molecular genetics of panic disorder

The molecular genetic research on panic disorder (PD) has grown tremendously in the past decade. Although the data from twin and family studies suggest an involvement of genetic factors in the familial transmission of PD with the heritability estimate near 40%, the genetic substrate underlying panicogenesis is not yet understood. The linkage studies so far have suggested that chromosomal regions 13q, 14q, 22q, 4q31-q34, and probably 9q31 are associated with the transmission of PD phenotypes. To date, more than 350 candidate genes have been examined in association studies of PD, but most of these results remain inconsistent, negative, or not clearly replicated. Only Val158Met polymorphism of the catechol-O-methyltransferase gene has been implicated in susceptibility to PD by several studies in independent samples and confirmed in a recent meta-analysis. However, the specific role of this genetic variation in PD requires additional analysis considering its gender- and ethnicity-dependent effect and putative impact on cognitive functions. The recent advantages in bioinformatics and genotyping technologies, including genome-wide association and gene expression methods, provide the means for far more comprehensive discovery in PD. The progress in clinical and neurobiological concepts of PD may further guide genetic research through the current controversies to more definitive findings.

Association Study between 5-HT1A Receptor Gene C(-1019)G Polymorphism and Panic Disorder in a Korean Population

OBJECTIVE

Serotonergic dysfunction is quite evident in panic disorder. We investigated whether the C(-1019)G polymorphism of 5-HT1A receptor gene may play a role in the pathogenesis of panic disorder in a Korean population.

METHODS

The 5-HT1A receptor genotype for the single nucleotide polymorphism (SNP) C(-1019)G was analyzed in 94 patients and 111 healthy controls. The severity of the patients' symptoms was examined using the Spielberger State-Trait Anxiety Inventory (STAI), Panic Disorder Severity Scale (PDSS), Anxiety sensitivity index (ASI), Acute Panic Inventory (API) and Hamilton's Rating Scale for Anxiety (HAM-A).

RESULTS

The distribution of the genotypes of the C/G polymorphism did not differ significantly from those predicted by Hardy-Weinberg equilibrium in patients as well as the controls. No association between the C(-1019)G polymorphism and panic disorder was detected in either the allele frequency or genotype distribution. There was no significant association with genotype distribution in the panic disorder with agoraphobia. However, there was a significant difference of symptom severity between C/C, C/G, and G/G genotype or between C and G allele in panic disorder patients without agoraphobia. PDSS scores were significantly higher in subjects with the G/G genotype or with G allele in patients without agoraphobia, not in total patients or patients with agoraphobia.

CONCLUSION

Although there were no significant differences in the genotype and allele distributions, we found a significant association between panic symptom severity and the serotonin 1A receptor gene. This result suggests that the serotonin 1A receptor and serotonin may play a role in the pathogenesis of panic disorder.

Is subclinical anxiety an endophenotype for bipolar I patients? A study from a Costa Rican sample

BACKGROUND

Although genetic influences on bipolar I disorder are well established, localization of genes that predispose to the illness has been difficult. Some genes predisposing to bipolar I disorder may be transmitted without expression of the categorical clinical phenotype. One strategy to overcome this obstacle is the use of quantitative endophenotypes, as has been done for other medical disorders.

METHODS

We analyzed 30 bipolar I extended families (300 subjects, average family size 10.34 members, range: 2-31) and 20 unrelated healthy controls from a Costa Rican sample. Heritability and genetic correlation of the state and trait scale from the Anxiety State and Trait Inventory was computed by using the general linear model (SOLAR package software). We also assessed variation of both scores among groups (patients, relatives and controls) and tested independence of affection status.

RESULTS

Heritability for state is 0.45 (SE=0.11, p=0.0000001) and for trait is 0.89 (SE=0.06, p=6.22e-29). Genetic correlation for state and trait is 0.29, (SE=0.12, p=0.038-3.19e-8). Bipolar I patients showed the highest trait score (F=12.17 [5,24], p=0.002), (bipolar I patients>relatives with other pathologies, >healthy relatives>unrelated healthy controls) with normal distribution in healthy individuals and no difference regarding depression and mania current status, (F=0.230, df=1, p=0.632 and F=1.401, df=1, p=0.238, respectively), contrary to the state score.

LIMITATIONS

Confounding factors such as comorbid disorders could affect the interaction of subclinical anxiety with mania. Due to our limited budget we were not able to re-evaluate the subjects and conduct a test retest to assess the STAI reliability and mood state independence of anxiety traits over different times. Further research is needed to evaluate if anxiety traits are specially related to bipolar I disorder in comparison with other traits such as anger, attention or response inhibition deficit, pathological impulsivity or low self-directedness.

CONCLUSIONS

Anxiety state and trait are heritable and share some genetic factors but only trait showed normal distribution in healthy subjects, mood current status independence and significant liability for bipolar I disorder. A stair-step distribution of trait anxiety scores in the family members and controls based on their genetic proximity to affected individuals and diagnostic status suggests that trait anxiety could be an endophenotype in these bipolar I families.

An improved in silico selection of phenotype affecting polymorphisms in SLC6A4, HTR1A and HTR2A genes

OBJECTIVE

Among the experimentally assessed DNA variations in serotonin related genes, some influence physiological expression of personality and mental disorders, others alter the responses to pharmacological and/or psychotherapeutic treatments. Because of the huge number of polymorphisms lying in genes and of the great length of time necessary to perform association studies, a selection of the variations being studied is a necessary and crucial step.

METHODS

In this work we used the most updated and assessed bioinformatic tools to predict the phenotype affecting polymorphisms of the human HTR1A, HTR2A and SLC6A4 serotonin related genes. Moreover, we carried out a literature search to collect information about the recent association studies to compare it versus our prediction data.

RESULTS

Gene polymorphism analysis indicated the variations that are worth considering in the association studies in the field of psychiatry, psychology and pharmacogenomics. The literature revision allowed to show both the few well and the most not enough investigated polymorphisms.

CONCLUSIONS

Our data can be useful to select polymorphisms for new association studies, especially those not yet investigated that can be related to behaviour, mental disorders and individual treatment response.

Dopamine and serotonin systems modify environmental effects on human behavior: a review

The relative influences of genetic and environmental factors in the development of human behavior have been a long-term topic for an intense debate. Recent behavioral genetic studies suggest focusing on the joint effect of genes and environment, and especially on the life-course developmental interplay between nature and nurture. Vulnerability to environmental adversities and sensitivity to its benefits may be conditional on genetic background, and regarding psychological outcomes, these kinds of gene x environment interactions may be of higher importance than direct gene-trait associations. In our recent series of studies, we have shown that different variants of serotonergic and dopaminergic genes may moderate the influence of environmental conditions on a range of psychological outcomes, i.e. temperament, depression, hostility, and educational attainment. These studies suggest that depending on their genotype, people may be differentially sensitive to the environmental conditions they encounter. In the light of these results it seems highly plausible that the effects of genes may become evident only when studied in the context of environmental factors.

Investigation of 17 candidate genes for personality traits confirms effects of the HTR2A gene on novelty seeking

Genes involved in serotonergic and dopaminergic neurotransmission have been hypothesized to affect different aspects of personality, but findings from genetic association studies did not provide conclusive results so far. In previous studies, however, only one or a few polymorphisms within single genes were investigated neglecting the possibility that the genetic associations might be more complex comprising several genes or gene regions. To overcome this limitation, we performed an extended genetic association study analyzing 17 serotonergic (SLC6A4, HTR1A, HTR1B, HTR2A, HTR2C, HTR3A, HTR6, MAOA, TPH1, TPH2) and dopaminergic genes (SLC6A3, DRD2, DRD3, DRD4, COMT, MAOA, TH, DBH), which have been previously reported to be implicated with personality traits. One hundred and ninety-five single nucleotide polymorphisms (SNPs) within these genes were genotyped with the Illumina BeadChip technology (HumanHap300, Human-1) in a sample of 366 mentally healthy Caucasians. Additionally, we tried to replicate our results in an independent sample of further 335 Caucasians. Personality traits in both samples were assessed with the German version of Cloninger's Tridimensional Personality Questionnaire. From 30 SNPs showing associations at a nominal level of significance, two intronic SNPs, rs2770296 and rs927544, both located in the HTR2A gene, withstood correction for multiple testing. These SNPs were associated with the personality trait novelty seeking. The effect of rs927544 could be replicated for the novelty seeking subscale extravagance, and the same SNP was also associated with extravagance in the combined samples. Our results show that HTR2A polymorphisms modulate facets of novelty seeking behaviour in healthy adults suggesting that serotonergic neurotransmission is involved in this phenotype.

Antagonism of serotonergic 5-HT2A/2C receptors: mutual improvement of sleep, cognition and mood?

Serotonin [5-hydroxytryptamine (5-HT)] and 5-HT receptors are involved in sleep and in waking functions such as cognition and mood. Animal and human studies support a particular role for the 5-HT(2A) receptor in sleep, which has led to renewed interest in this receptor subtype as a target for the development of novel pharmacological agents to treat insomnia. Focusing primarily on findings in healthy human volunteers, a review of the available data suggests that antagonistic interaction with 5-HT(2A) receptors (and possibly also 5-HT(2C) receptors) prolongs the duration of slow wave sleep and enhances low-frequency (< 7 Hz) activity in the sleep electroencephalogram (EEG), a widely accepted marker of sleep intensity. Despite certain differences, the changes in sleep and the sleep EEG appear to be remarkably similar to those of physiologically more intense sleep after sleep deprivation. It is currently unclear whether these changes in sleep are associated with improved vigilance, cognition and mood during wakefulness. While drug-induced interaction with sleep must be interpreted cautiously, too few studies are available to provide a clear answer to this question. Moreover, functional relationships between sleep and waking functions may differ between healthy controls and patients with sleep disorders. A multimodal approach investigating subjective and objective aspects of sleep and wakefulness provides a promising research avenue for shedding light on the complex relationships among 5-HT(2A/2C) receptor-mediated effects on sleep, the sleep EEG, cognition and mood in health and various diseases associated with disturbed sleep and waking functions.

Reduced 5-HT(2A) receptor signaling following selective bilateral amygdala damage

Neurobiological evidence implicates the amygdala as well as serotonergic (serotonin, 5-HT) signaling via postsynaptic 5-HT(2A) receptors as essential substrates of anxiety behaviors. Assuming a functional interdependence of these substrates, we hypothesized that a low-fear behavioral phenotype due to bilateral lesion of the amygdala would be associated with significant 5-HT(2A) receptor changes. Thus, we used [(18)F]altanserin positron emission tomography (PET) referenced to radioligand plasma levels and corrected for partial volume effects to quantify the spatial distribution of 5-HT(2A) receptor binding potential (BP(P)) in a rare patient with Urbach-Wiethe disease and selective bilateral amygdala calcification damage relative to 10 healthy control subjects. Consistent with our a priori hypothesis, we observed a 70% global decrease in 5-HT(2A) receptor BP(P) in the Urbach-Wiethe patient relative to controls. Thus, brain abnormalities in this patient are not restricted to the amygdala, but extend to overall 5-HT neurotransmission via 5-HT(2A) receptors. Our findings provide important insights into the molecular architecture of human anxiety behaviors and suggest the 5-HT(2A) receptor as a promising pharmacological target to control pathological anxiety.

Serotonin1A receptors in the pathophysiology of schizophrenia: development of novel cognition-enhancing therapeutics

Serotonin (5-HT) receptors have been suggested to play key roles in psychosis, cognition, and mood via influence on neurotransmitters, synaptic integrity, and neural plasticity. Specifically, genetic evidence indicates that 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptor single-nucleotide polymorphisms (SNPs) are related to psychotic symptoms, cognitive disturbances, and treatment response in schizophrenia. Data from animal research suggest the role of 5-HT in cognition via its influence on dopaminergic, cholinergic, glutamatergic, and GABAergic function. This article provides up-to-date findings on the role of 5-HT receptors in endophenotypic variations in schizophrenia and the development of newer cognition-enhancing medications, based on basic science and clinical evidence. Imaging genetics studies on associations of polymorphisms of several 5-HT receptor subtypes with brain structure, function, and metabolism suggest a role for the prefrontal cortex and the parahippocampal gyrus in cognitive impairments of schizophrenia. Data from animal experiments to determine the effect of agonists/antagonists at 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptors on behavioral performance in animal models of schizophrenia based on the glutamatergic hypothesis provide useful information. For this purpose, standard as well as novel cognitive tasks provide a measure of memory/information processing and social interaction. In order to scrutinize mixed evidence for the ability of 5-HT(1A) agonists/antagonists to improve cognition, behavioral data in various paradigms from transgenic mice overexpressing 5-HT(1A) receptors provide valuable insights. Clinical trials reporting the advantage of 5-HT(1A) partial agonists add to efforts to shape pharmacologic perspectives concerning cognitive enhancement in schizophrenia by developing novel compounds acting on 5-HT receptors. Overall, these lines of evidence from translational research will facilitate the development of newer pharmacologic strategies for the treatment of cognitive disturbances of schizophrenia.

Polymorphisms in the galanin gene are associated with symptom-severity in female patients suffering from panic disorder

BACKGROUND

Galanin (GAL) is a neuropeptide, which is expressed primarily in limbic nuclei in the brain and mediates miscellaneous physiological processes and behaviors. In animal studies, both the application of GAL and antagonism of its receptors have been shown to affect anxiety-like and depression-related behavior. In humans, intravenous administration of the neuropeptide galanin has been reported to have fast antidepressant efficacy. Furthermore, GAL is involved in hypothalamic-hypophysiotropic signalling and cosecreted with luteinizing hormone-releasing hormone (LHRH), possibly acting as a mediator of estrogen action.

METHODS

In this study six single nucleotide polymorphisms (SNPs) within the gene coding for GAL were analyzed for possible associations with diagnosis and severity of symptoms in 121 male and female patients suffering from panic disorder (PD).

RESULTS

Our results suggest an association between genetic variations in the GAL-gene and severity of PD-symptoms in female patients. The most pronounced effects could be observed for two haplotypes containing the closely linked, non-protein-coding SNPs rs948854 and rs4432027. Both polymorphisms are located within CpG-dinucleotides in the promoter region of GAL and thus might be involved in epigenetic regulation of the GAL-gene.

LIMITATIONS

A relatively small patient sample was analyzed in this study, the herein presented results need to be validated in independent studies.

CONCLUSIONS

The results of this study underline the potential of further genetic research concerning GAL and a possible role of this neuropeptide in the pathogenesis of female PD. In this regard, GAL and its receptors appear to be a promising target for pharmacological therapy of anxiety and affective disorders.