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The serotonin 2A receptor (5‐HT2AR) is implicated in the pathophysiology and treatment of various psychiatric disorders. [18F]altanserin and [11C]Cimbi‐36 positron emission tomography (PET) allow for high‐resolution imaging of 5‐HT2AR in the living human brain. Cerebral 5‐HT2AR binding is strongly genetically determined, though the impact of specific variants is poorly understood. Candidate gene studies suggest that HTR2A single nucleotide polymorphisms including rs6311/rs6313, rs6314, and rs7997012 may influence risk for psychiatric disorders and mediate treatment response. Although known to impact in vitro expression of 5‐HT2AR or other serotonin (5‐HT) proteins, their effect on human in vivo brain 5‐HT2AR binding has as of yet been insufficiently studied. We thus assessed the extent to which these variants and the commonly studied 5‐HTTLPR predict neocortex in vivo 5‐HT2AR binding in healthy adult humans. We used linear regression analyses and likelihood ratio tests in 197 subjects scanned with [18F]altanserin or [11C]Cimbi‐36 PET. Although we observed genotype group differences in 5‐HT2AR binding of up to ~10%, no genetic variants were statistically significantly predictive of 5‐HT2AR binding in what is the largest human in vivo 5‐HT2AR imaging genetics study to date. Thus, in vitro and post mortem results suggesting effects on 5‐HT2AR expression did not carry over to the in vivo setting. To any extent these variants might affect clinical risk, our findings do not support that 5‐HT2AR binding mediates such effects. Our observations indicate that these individual variants do not significantly contribute to genetic load on human in vivo 5‐HT2AR binding., We evaluated whether common HTR2A single nucleotide polymorphisms rs6313, rs6314, rs7997012, and the 5‐HTTLPR predict 5‐HT2AR binding, assessed with [18F]altanserin and [11C]Cimbi‐36 positron emission tomography in healthy individuals. This is the largest study to date evaluating genetic predictors of a human in vivo serotonin protein (n = 197). Although relative differences of up to 10% were detected, no statistically significant effect was observed. Our results do not support a significant contribution of these individual variants to genetic load on 5‐HT2AR binding.

Background Several studies indicated that antipsychotic treatment response and side effect manifestation can be different due to inter-individual variability in genetic variations. Aim of the study Here we perform a case-control study to explore a potential association between schizophrenia and variants within the antipsychotic drug molecular targets (DRD1, DRD2, DRD3, HTR2A, HTR6) and metabolizing enzymes (CYP2D6, COMT) genes in Armenian population including also analysis of their possible relationship with disease clinical symptoms. Methods A total of 18 SNPs was studied in patients with schizophrenia (n = 78) and healthy control subjects (n = 77) using MassARRAY genotyping. Results: We found that two studied genetic variants, namely DRD2 rs4436578*C and HTR2A rs6314*A are underrepresented in the group of patients compared to healthy subjects. After the correction for multiple testing, the rs4436578*C variant remained significant while the rs6314*A reported borderline significance. No significant differences in minor allele frequencies for other studied variants were identified. Also, a relationship between the genotypes and age of onset as well as disease duration has been detected. Conclusions The DRD2 rs4436578*C genetic variant might have protective role against schizophrenia, at least in Armenians.

Objective Genetic polymorphisms and mutations in candidate genes are considered important in the etiology of autism, and particular interest is focussed on the serotonin system. Here, we used SNP analysis in the serotonin receptor gene to identify differences between autistic and healthy control children. Methods Genetic association of rs6313 (T102C) and rs6314 (C1354T) polymorphisms in HTR2A gene with susceptibility to the development of autism in children were investigated using PCRRFLP, and correlated serotonin levels in blood serum using ELISA method. Results We uniquely found an association between the presence of the T allele at the position rs6313 (OR=2.00, 95%CI: 1.23-3.26, p=0.005), and between the presence of the C allele at the position rs6314 (OR=2.24, 95% CI: 1.47-3.42, p=0.0002) of the serotonin receptor gene under conditions of a decreased ASD incidence. We also noted that T allele at the position rs6313, and C allele at the position rs6314 was 3 times more frequent in Control males than in ASD males. We found no statistical significant correlation between HTR2A SNPs and the blood serum level of serotonin between autistic and control children. Conclusion This study shows the involvement of HTR2A, rather than the concentration of serotonin, in the development of autism, and provides a rationale for future design of therapeutic modalities based on the serotonin system for childhood autism.

OBJECTIVE Migraine, a highly prevelant headache disorder, is regarded as a polygenic multifactorial disease. Serotonin (5-HT) and their respective receptors have been implicated in the patogenesis. METHODS We investigated the 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT2C receptor gene polymorphisms and their association with migraine in Turkish patients. The rs6295, rs1300060, rs1228814, rs6311, rs6313, rs6314, rs6318, rs3813929 (-759C/T) and rs518147 polymorphisms were analyzed in 135 patients with migraine and 139 healthy subjects, using a BioMark 96.96 dynamic array system. RESULTS We found no difference in the frequency of the analyzed eight out of nine polymorpisms between migraine and control groups. However, a significant association was found between the rs3813929 polymorphism in the promoter region of 5-HTR2C gene and migraine. Also, the allele of rs3813929 was more common in the migraine group. CONCLUSION This result suggests that the 5-HTR2C rs3813929 polymorphism can be a genetic risk factor for migraine in a Turkish population.

Pharmacological studies have yielded valuable insights into the role of the serotonin 2A (5-HT2A) receptor in major depressive disorder (MDD) and antidepressant drugs (ADs) response. However, it is still unknown whether genetic variants in the HTR2A gene affect the therapeutic outcome of ADs and the mechanism underlying the regulation of such response remains poorly described. In this context, a translational human-mouse study offers a unique opportunity to address the possibility that variations in the HTR2A gene may represent a relevant marker to predict the efficacy of ADs. In a first part of this study, we investigated in depressed patients the effect of three HTR2A single nucleotide polymorphisms (SNPs), selected for their potential functional consequences on 5-HT2A receptor (rs6313, rs6314 and rs7333412), on response and remission rates after 3 months of antidepressant treatments. We also explored the consequences of the constitutive genetic inactivation of the 5-HT2A receptor (i.e. in 5-HT2A(-/-) mice) on the activity of acute and prolonged administration of SSRIs. Our clinical data indicate that GG patients for the rs7333412 SNP were less prone to respond to ADs than AA/AG patients. In the preclinical study, we demonstrated that the 5-HT2A receptor exerts an inhibitory influence on the neuronal activity of the serotonergic system after acute administration of SSRIs. However, while the chronic administration of the SSRIs escitalopram or fluoxetine elicited a progressive increased in the firing rate of 5-HT neurons in 5-HT2A(+/+) mice, it failed to do so in 5-HT2A(-/-) mutants. These electrophysiological impairments were associated with a decreased ability of the chronic administration of fluoxetine to stimulate hippocampal plasticity and to produce antidepressant-like activities. Genetic loss of the 5-HT2A receptor compromised the activity of chronic treatment with SSRIs, making this receptor a putative marker to predict ADs response.

OBJECTIVE: We examined the effect of risk alleles of polymorphisms of three schizophrenia risk genes that mediate monoamine signalling in the brain on regional brain volumes of schizophrenia and healthy control subjects. The risk alleles and the gene polymorphisms studied were: Val allele of catechol o-methyltransferase (COMT) rs4680 polymorphism; short allele of 5-hydroxy tryptamine transporter linked polymorphic region (5HTTLPR) polymorphism; and T allele of 5-hydroxy tryptamine 2A (5HT2A) rs6314 polymorphism. METHODS: The study was carried out on patients with recent onset schizophrenia (n=41) recruited from the outpatient department of National Institute of Mental Health and Neurosciences, Bangalore, India and healthy control subjects (n=39), belonging to South Indian Dravidian ethnicity. Individual and additive effects of risk alleles of the above gene polymorphisms on brain morphometry were explored using voxel-based morphometry. RESULTS: Irrespective of phenotypes, individuals with the risk allele T of the rs6314 polymorphism of 5HT2A gene showed greater (at cluster-extent equivalent to family wise error-correction [FWEc] p

Suicide is an important public health problem. The aim of the present study is to determine the incidence of serotonin receptor gene polymorphisms (rs6313and rs6314) in patients with a history of suicide attempt by blood sampling and to evaluate whether a causal relation exists between gene polymorphisms and suicide. After obtaining the necessary approvals for the study, we included 178 patients with attempted suicide history admitted to the emergency room between December 14, 2016 and July 31, 2016; 174 control subjects were also included. The blood samples were tested for rs6313 and rs6314 polymorphisms. Among the 178 cases with attempted suicide history, 116 (65.2%) were females and 62 (35.8%) were males. With regard to rs6313 polymorphisms in the case group, 40 cases had AA genotype, 99 had AG genotype, and 39 had GG genotype. In the control group, 38 subjects had AA genotype, 91 had AG genotype, and 45 had GG genotype. With regard to rs6314 polymorphisms, 176 cases in the case group had AG genotype and two cases had GG genotype in the case group, whereas 171 subjects in the control group had AG genotype and three subjects had GG genotype in the control group. The present study did not find any significant association between the incidence of rs6313 and rs6314 polymorphisms and suicidal behavior.

Aim Life events are series of events that disrupt a person's psychological equilibrium and may enhance the development of a disorder such as suicide. Several studies have assessed a relationship between 5-hydroxytryptamine (serotonin) 2A receptor (5-HTR2A) gene polymorphisms with an increased risk of suicide. However, there has been no study about the association between three 5-HTR2A gene polymorphisms, A1438G (rs6311), T102C (rs6313) and C1354T (rs6314), suicide, stressful life, and loss events in a same time. Methods Relatives of 191 suicide victims were interviewed using a semi-structured questionnaire designed according to Iranian culture. Venous blood was taken from all subjects for DNA isolation. 5-HTR2A polymorphisms in a total of 191 suicide victims and 218 healthy controls were genotyped using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP). Chi-squared and Fisher's exact tests were used to compare genotype and allele frequencies between suicide and control groups. Correction for multiple comparisons was calculated using Bonferroni correction. Results There was a significant association between the 102 C/C genotype of 5-HTR2A gene and suicide (к2 = 8.700, P = 0.012). Furthermore, we found that suicide victims with a 102 C/C genotype had a significantly higher number of stressful life and loss events (P 0.05). Conclusion Our results suggest that C102T (rs6313) polymorphism of 5-HTR2A gene may be involved in the susceptibility to suicide, higher number of stressful life and loss events, but A1438G (rs6311) and C1354T (rs6314) polymorphisms of 5-HTR2A gene were not associated with suicide, higher number of stressful life and loss events.

Serotonin receptor 2A (HTR2A) is an important signalling factor implicated in cognitive functions and known to be associated with schizophrenia. The biological significance of HTR2A in schizophrenia remains unclear as molecular analyses including genetic association, mRNA expression and methylation studies have reported inconsistent results. In this study, we examine HTR2A expression and methylation and the interaction with HTR2A polymorphisms to identify their biological significance in schizophrenia. Subjects included 25 schizophrenia and 25 control post-mortem brain samples. Genotype and mRNA data was generated by transcriptome sequencing. DNA methylation profiles were generated for CpG sites within promoter-exon I region. Expression, genotype and methylation data were examined for association with schizophrenia. HTR2A mRNA levels were reduced by 14% (p = 0.006) in schizophrenia compared to controls. Three CpG sites were hypermethylated in schizophrenia (cg5 p = 0.028, cg7 p = 0.021, cg10 p = 0.017) and HTR2A polymorphisms rs6314 (p = 0.008) and rs6313 (p = 0.026) showed genetic association with schizophrenia. Differential DNA methylation was associated with rs6314 and rs6313. There was a strong correlation between HTR2A DNA methylation and mRNA expression. The results were nominally significant but did not survive the rigorous Benjamini-Hochberg correction for multiple testing. Differential HTR2A expression in schizophrenia in our study may be the result of the combined effect of multiple differentially methylated CpG sites. Epigenetic HTR2A regulation may alter brain function, which contributes to the development of schizophrenia.

An association between serotonin 2A receptor (5-HT2AR), encoded by HTR2A gene, and major depressive disorder (MDD) has been suggested. Here, we combined preclinical and ecological clinical approaches to explore the impact of impaired 5-HT2AR-mediated transmission on MDD or anxio-depressive-like phenotype in mice. Htr2a knock-out mice (Htr2a(-/-)) and wild-type mice were compared for the ability of chronic corticosterone to elicit some anxio-depressive-like phenotype in three behavioral paradigms (elevated plus maze, tail suspension test and splash test). Accordingly, two single nucleotide polymorphisms of the HTR2A gene (rs6314 ie His452Tyr and rs6313 ie 102C/T), which specific allelic variants may decrease 5-HT2AR-mediated transmission (as in Htr2a(-/-)mice), were studied in a sample of 485 Caucasian patients with MDD. In response to chronic corticosterone exposure, Htr2a(-/-) mice displayed more pronounced anxiodepressive-like phenotype than wild-type mice, as shown by a significant higher "emotionality score" (p0.01). In patients, the C allele of rs6313 was more frequent in depressed patients (p=0.019) and was also associated with a more severe major depressive episode (p=0.03). This translational and ecological study involving constitutive Htr2a(-/-) knock-out mice and related SNPs in depressed patients suggests that a lower neurotransmission at the 5-HT2AR may favor the susceptibility and severity of MDE. It also suggests that specific allelic variants of the rs6313 and rs6314 may reduce 5-HT2AR-mediated transmission.

The serotonin 2A receptor gene (HTR2A) harbors two functional single nucleotide polymorphisms (SNPs) that are frequent in populations of African and European descent; rs6311, which affects mRNA expression, and rs6314, which changes the amino acid sequence of the encoded protein and affects the signaling properties of the receptor. Multiple clinical associations support a role for these SNPs in cognitive and neuropsychiatric phenotypes, although studies in autism spectrum disorder (ASD) remain equivocal. Here, we tested transmission disequilibrium of rs6311 and rs6314 in a cohort of 158 ASD trios (simplex and multiplex), observing significant under-transmission of the minor "A" allele of rs6311 to offspring with ASD (permuted P = 0.0004). Consistent with our previous findings in the dorsolateral prefrontal cortex of unaffected individuals, rs6311/A decreases expression of HTR2A mRNA with an extended 5' untranslated region (UTR) in the frontopolar cortex in brain samples from 54 ASD patients and controls. Interpreting the clinical results in the context of our mRNA expression analysis, we speculate that any risk associated with rs6311 is conferred by greater expression of the long 5'UTR mRNA isoform. The current study corroborates earlier associations between rs6311 and ASD in a family study, supporting the hypothesis that rs6311 plays a modulatory role in ASD risk.

Food reinforcement, or the motivation to eat, has been associated with increased energy intake, greater body weight and prospective weight gain. Much of the previous research on the reinforcing value of food has focused on the role of dopamine, but it may be worthwhile to examine genetic polymorphisms in the serotonin and opioid systems as these neurotransmitters have been shown to be related to reinforcement processes and to influence energy intake. We examined the relationship among 44 candidate genetic polymorphisms in the dopamine, serotonin and opioid systems, and food reinforcement and body mass index (BMI) in a sample of 245 individuals. Polymorphisms in the Monoamine oxidase A (MAOA-LPR) and serotonin receptor 2A genes (rs6314) moderated the effect of food reinforcement on BMI, accounting for an additional 5-10% variance and revealed a potential role of the single nucleotide polymorphism, rs6314 in the serotonin 2A receptor as a differential susceptibility factor for obesity. Differential susceptibility describes a factor that can confer either risk or protection depending on a second variable, such that rs6314 is predictive of both high and low BMI based on the level of food reinforcement, while the diathesis stress or dual-gain model influences only one end of the outcome measure. The interaction with MAOA-LPR better fit the dual-risk or diathesis stress model, with the 3.5R/4R allele conferring protection for individuals low in food reinforcement. These results provide new insight into genes theoretically involved in obesity and support the hypothesis that genetics moderate the association between food reinforcement on BMI.

Objective and background Our aim was to characterize the association of 2 functional single nucleotide polymorphisms (rs6311 and rs6314) in the serotonin 2A receptor gene (HTR2A) with severity of depression symptoms in children with autism spectrum disorder. These polymorphisms have been shown to be associated with depression symptom severity and response to selective serotonin reuptake inhibitor drugs in adults with diagnosed depressive disorder. Methods Parents of 104 children with autism spectrum disorder rated their children's depressive symptoms using a validated scale based on criteria from the Diagnostic and Statistical Manual of Mental Disorders, 4th edition. We compared severity of depression symptoms across the rs6311 and rs6314 genotypes, measured from the children's genomic DNA. Results Children homozygous for the G allele of rs6311 had significantly more severe depression symptoms than those with G/A or A/A genotypes (P=0.025). The effect size (partial eta-squared) was small (ηp=0.047) but was somewhat larger when we controlled for severity of generalized anxiety disorder symptoms (P=0.006, ηp=0.072). When we restricted our analyses to white participants, our results were essentially the same as for the entire sample (P=0.004, ηp=0.086). There was no significant association between rs6314 (C/C versus T carriers) and severity of depression. Conclusions Our findings suggest that the HTR2A functional rs6311 polymorphism, which other studies have associated with differential HTR2A mRNA expression, may modulate the severity of depression symptoms in children with autism spectrum disorder. These tentative, hypothesis-generating findings need replication with larger, independent samples.

Several gene variants have been related to major depressive disorder (MDD) treatment outcomes; however, few studies have investigated a possible different effect on pharmacotherapy and brief psychotherapy response. A total of 137 MDD patients were randomized to either interpersonal counseling (IPC; n = 40) or antidepressant pharmacological treatment (n = 97). Outcomes were remission, response, and symptom improvement at week 8. Five genetic variants were investigated (5HTR2A rs6314, BDNF rs6265, SLC6A4 rs8076005, CREB1 rs2253206, and TPH2 rs11179023) as possible modulators of outcomes. The LC6A4 rs8076005 AA genotype and A allele were associated with response rate in the antidepressant group (p = 0.015 and 0.005, respectively) and in the whole sample (p = 0.03 and 0.02, respectively). In the IPC group a non-significant trend in the same direction was observed. The TPH2 rs11179023 A allele showed a marginal association with symptom improvement in the IPC group only. Other gene variants did not impact on outcomes in any treatment group. Our study suggests that rs8076005 in the SLC6A4 gene may be a modulator of antidepressant response, especially when pharmacological treatment is used.

Wagner et al. (2008) recently published a brief report in the International Journal of Neuropsychopharmacology , which replicated the previous findings of de Quervain et al. (2003) and indicated that the functional 5-HT2A receptor variant, His452Tyr (rs6314), is associated with episodic long-term memory in humans. There is considerable evidence from studies in animals and humans that serotonin is pivotally implicated in learning and memory (e.g. Buhot, 1997). The tyrosine (Tyr) allele of the His452Tyr variant in the human 5-HT2A receptor is associated with blunted receptor response upon serotonin stimulation (Ozaki et al. 1997) with effects on intracellular calcium levels and protein kinase-A phosphorylation, both of which are important for memory formation at the cellular level. This would influence performance on memory tasks, as has been shown for pharmacological manipulation of serotonin receptors (Meneses, 2007). Wagner et al. (2008) compared 113 His/His carriers to 20 His/Tyr carriers on a variety of cognitive tests. They hypothesized that the His/Tyr group would manifest poorer performance on long-term recall and recognition tasks. To test the discriminant validity of the variant (i.e. that the variant is specifically related to long-term episodic memory functions and not to other cognitive functions), Wagner et al. (2008) also tested performance differences between the groups on tasks measuring short-term memory, attention and executive functions. The results showed that the His/Tyr group recognized and recalled fewer words than the His/His group on an auditory, free recall, learning task with a 30-min retention interval between learning phase and test phase. There was no similar pattern of difference for tasks measuring attention and executive functioning. We obtained further data on the association between the 5-HT2A receptor His452Tyr variant and memory function from the ‘Why Do Young Women Smoke?’ (WDYWS) project, a study ongoing …

Importance Serotonin (5-hydroxytryptamine) receptor 2a (5-HT2AR) signaling is important for modulation of corticostriatal pathways and prefrontal activity during cognition. Furthermore, newer antipsychotic drugs target 5-HT2AR. A single-nucleotide polymorphism in the 5-HT2AR gene ( HTR2A rs6314, C>T; OMIM 182135) has been weakly associated with differential 5-HT2AR signaling and with physiologic as well as behavioral effects. Objective To use a hierarchical approach to determine the functional effects of this single-nucleotide polymorphism on 5-HT2AR messenger RNA and protein expression, on prefrontal phenotypes linked with genetic risk for schizophrenia, and on treatment with olanzapine. Design In silico predictions, in vitro, and case-control investigations. Setting Academic and clinical facilities. Participants The postmortem study included 112 brains from healthy individuals; the in vivo investigation included a total sample of 371 healthy individuals and patients with schizophrenia. Exposures Patients received olanzapine monotherapy for 8 weeks. Main Outcomes and Measures In silico predictions, messenger RNA, and protein expression in postmortem human prefrontal cortex and HeLa cells, functional magnetic resonance imaging prefrontal activity and behavior during working memory and attention in healthy individuals, and response to an 8-week trial of olanzapine treatment in patients with schizophrenia. Results Bioinformatic analysis predicted that rs6314 alters patterns of splicing, with possible effects on HTR2A expression. Moreover, the T allele was associated with reduced prefrontal messenger RNA expression in postmortem prefrontal cortex, with reduced protein expression in vitro, inefficient prefrontal blood oxygen level–dependent functional magnetic resonance imaging response during working memory and attentional control processing, and impaired working memory and attention behavior, as well as with attenuated improvement in negative symptoms after olanzapine treatment. Conclusions and Relevance Our results suggest that HTR2A rs6314 affects 5-HT2AR expression and functionally contributes to genetic modulation of known endophenotypes of schizophrenia-like higher-level cognitive behaviors and related prefrontal activity, as well as response to treatment with olanzapine.

Background Serotonin receptor 1A and 2A genes polymorphisms (HTR1A and HTR2A) have been associated to increased risk of depression and suicide. Hypomethylated HTR1A has been associated to Systemic Lupus Erythematosus (SLE) patients manifestations. Preliminary results in our cohort showed an association between HTR2A polymorphisms and SLE manifestations development risk and depression risk in SLE patients. Objectives To investigate the association of 5-HTR2A polymorphisms (rs6314, rs6313) and clinical organ involvement, specific antibodies expression and damage accrual and time to damage accrual in SLE patients. Methods 75 SLE patients were evaluated for 5-HTR2A polymorphisms rs6314 and rs6313, by a Taqman assay and PCR-RFLP methodology, respectively. SLE diagnosis was based in ACR 1999 criteria, the organic involvement and specific antibodies were reviewed in the charts (Cumulative SLE manifestations for genetic studies) and damage was assessed by SDI (Systemic Lupus International Collaborating Clinics - Damage Index). Statistical analysis was made with SPSS 22.0. Results 75 SLE patients (70 female) with a mean age of diagnosis of 29.55 years old (SD 12.0) and mean follow-up time of 17,39 years (SD 7,70). Mucocutaneous involvement occurred in 88%, articular 85,3%, renal 46,7%, 30,7% neuropsychiatric. 38 patients (50,7%) had organ damage acrrual with a mean time to first damage accrual of 3,75 years (SD 6,88). 7 (9,3%) accrued renal damage and 15 (20%) neuropsychiatric. Polymorphism distribution was rs6313 (CC 22,7%, CT 54,7% e TT 14,7%) and rs 6314 (CC 86,7%, CT 13,3%). No association was found between these polymorphisms and any clinical involvement, cytopenias, antibodies, damage accrual or time to damage. Neuropsychiatric damage accrual was earlier in patients carrying CC rs6314. Conclusions Contradictory results are a very common phenomena in studies of complex diseases mainly due to the interaction fo several genes. Although poorly studied the serotonin receptor and transporter genes have been linked to SLE development and depression in SLE patients. In our study, there was no relation between any clinical or serological manifestations and the rs6313 and rs6314 HTR2A polymorphism but the earlier neuropsychiatric damage accrual opens a window of doubt of what might be the role of serotonin in SLE heterogeneity. Disclosure of Interest None declared

and PsycINFO databases. We included in the review only polymorphisms investigated in at least three independent samples. We performed meta-analytic calculations when genetic data about the same polymorphism were available for three or more independent samples. For meta-analyses, data were entered and analyzed into the Cochrane Collaboration Review Manager Software (RevMan version 5.2). Individual and pooled odds ratio (OR) and associated 95% confidence intervals (CIs) were calculated. Heterogeneity among studies was assessed with Chi2-test of fit and I2. The significance of the pooled effect size was determined using a Z test. Data were analyzed using a random effect framework because of the assumption of the presence of significant betweenstudy heterogeneity. A funnel plot was created to reveal selective reporting by plotting natural logarithm of individual study effect size. Publication bias was also assessed using the Egger test through the statistics environment R (http://www.R-project.org) version 3.0.2, package ‘metaphor’. Results: Our literature search yielded 9266 articles on CLZ; among these, we identify 59 pertinent pharmacogenetic studies about CLZ efficacy which were included in the present study. Genotype data were retrieved for 14 polymorphisms in 9 genes upon the total 168 polymorphisms in 44 genes that were investigated in literature. Among these, we had available data from at least three independent sample for 8 SNPs in order to perform meta-analyses. Although literature review provided conflicting results, four genetic variants within serotonin genes resulted associated to CLZ response in our meta-analyses: rs6311 (p = 0.02) and rs6314 (p = 0.02) within HTR2A gene, rs6318 (p = 0.007) within HTR2C gene and rs1062613 (p = 0.03) within HT3A gene. On the other hand four SNPs (rs1799732 within DRD2 gene, rs6280 within DRD3 gene, rs6311 within HTR2A gene, rs1800629 within TNFa gene) were not associated with CLZ efficacy in our analyses. Discussion: Literature review provided conflicting results. On the other hand, our meta-analyses showed four association among genetic variants within serotonin genes and CLZ response. These data suggest a strong importance of CLZ serotonergic effects in the determination of the clinical response to this drug. Further data are required to better dissect these findings, which could be another piece to knowledge to move forward the simplistic dopaminergic hypothesis for schizophrenia.

OBJECTIVE The serotonin 2A receptor gene (HTR2A) is involved in serotonergic neurotransmission, and has been targeted as a functional candidate for mood disorders because of the extensive support for the involvement of serotonin in mood regulation. We previously reported linkage evidence for a bipolar affective disorder susceptibility locus on chromosome 13q, which harbours HTR2A, thus making the gene both a positional and functional candidate. We assessed HTR2A for association in an Australian bipolar disorder case-control cohort. METHODS Single nucleotide polymorphisms (SNPs) were selected across HTR2A exons and introns, and were investigated for association in an Australian cohort of 218 cases and 166 healthy controls. SNP haplotypes were also examined for association. RESULTS Significant association of rs2224721 (P = 0.02) and borderline significance of rs1923886 (P = 0.05) were observed. The former remained significant after multiple testing corrections using the rough False Discovery Rate method, but did not exceed the more conservative Bonferroni's correction threshold. Haplotype association analysis suggests that the haplotype CCGCA (at SNPs rs3125, rs6314, rs1923886, rs2224721 and rs2770296) is protective against bipolar disorder (P = 0.021, odds ratio 0.63) and the rarer haplotype CCACG confers risk to the disorder (P = 0.0065, odds ratio 3.08). CONCLUSION We found that HTR2A is associated with bipolar disorder. The HTR2A gene should not be excluded as a potential susceptibility gene for bipolar disorder despite a number of conflicting association results.

Several studies suggest involvement of serotoninergic system in the pathophysiology of Autism Spectrum Disorder (ASD). The 5-HT receptor binding studies using (3)H-lysergic acid diethylamide ((3)H-LSD) and linkage analysis provided evidences to consider HTR2A as a potential candidate gene for ASD. The three SNPs, -1438A/G (rs6311), 102T/C (rs6313) and 1354C/T (rs6314) of HTR2A have been well studied in the etiology of various neuropsychiatric disorders. But studies on association of this gene with ASD are limited to two reports from American and Korean populations. Additionally there are reports, which demonstrated paternal imprinting of HTR2A with expression from only one allele. So far no reports are available on HTR2A and its association with any neuropsychiatric disorders from Indian population. Therefore, the present study investigates association of the above mentioned three markers of HTR2A with ASD in Indian population using population and family-based approaches. The study also deals with allelic expression pattern of HTR2A in Peripheral Blood Leukocytes (PBLs) to understand the parental imprinting status. The genotyping analyses were carried out for probands, parents and controls. The subsequent association analyses did not show association of these markers with ASD. So, HTR2A is unlikely to be a genetic marker for ASD in Indian population. The expression analyses showed absence of monoallelic expression, suggesting lack of parental imprinting of HTR2A gene. However, we noticed methylation of the CpG sites at -1438A/G and 102T/C loci of HTR2A gene. Further bioinformatics analysis revealed absence of CpG islands in the promoter of the gene supporting biallelic expression pattern of HTR2A in PBLs.

Background Fibromyalgia is a chronic pain syndrome, characterized by widespread pain and tenderness at spesific anatomical localizations. Objectives The purpose is investigating candidate genes related to the serotonergic system which is thought to be responsible for the pathophysiology of primer fibromyalgia and the validity of serotonin receptor gene polymorphisms for the Turkish society. Methods Ninety-six female patients diagnosed with fibromyalgia according to 1990 and 2010 ACR criteria and 96 healthy controls were included in the study. A detailed medical history of the patients were taken, the symptoms were questioned. Assessment of disease activity and functional status were performed with tender point examination and assessment of the severity of the pain, Fibromyalgia Impact Questionnaire. A total of 192 blood samples were taken from the patient and the control group and isolation of DNA was performed. Primer design for serotonin receptor gene was done, the products derived from polymerase chain reaction were cleaned. The analysis of sequence results after the sequence reaction and statistical evaluation were performed. Results The regions of serotonin receptor 2A gene were analyzed. According to the analysis, E318E mutation occurring at amino acid 318 which has not caused a change in any amino acid, and V143V mutation which has not caused a change at amino acid 143 were detected for the first time. A similar number of heterozygous polymorphic allele of rs35224115 single-nucleotide polymorphism were found in the patient and control groups. Although, Rs6305 was found as polymorphic heterozygous in 7 samples in the patient grup, it was found in 3 samples in the control group. Although, Rs6314 was found in 3 samples as polymorphic heterozygous in the control group, it was found in 16 samples in the patient group. The difference between the two groups in terms of the incidence of heterozygous allele was statistically significant according to chi-square test (p=0.002). Conclusions In our study that we investigate the relationship between fibromyalgia and the exons of serotonin receptor 2A gene which are the protein-coding regions, we found that rs6314 polymorphism associated with the disease. This relationship is a result which can be used and developed for diagnostic and treatment process. We also determined two new possible polymorphism single base change (E318E, V143V), but we did not find any relationship with the fibromyalgia syndrome. We determined that, there was no differce in terms of other known polymorphisms between patients and controls. Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.4187

The variance of results between our recent article [1] and the replication study by Kirsten and colleagues [2] in German patients may prompt the reader to ask the simple question: what conclusion can be drawn from these contradictory results? One possible answer is that one of the two studies is wrong and all the clues would indicate the first report as the one describing a spurious finding. This is consistent with a general overestimate of the role of a gene in the first association study of it [3] and, indeed, we have always been aware of the possibility of false positive findings. Hence, we provided the reader a mean (for example, the false probability report probability) with which to gauge the strength of the association and the chance of having described a spurious result [1]. A second possible answer is that the variance of results stems from methodological differences between the two studies. It has been argued that replication studies should be viewed as tools to uncover heterogeneity rather than tools to test the hypothesis generated by the initial association [3] and, in a more extreme view, the relevance of replication has been questioned [4]. Our and Kirsten and colleagues' studies are heterogeneous with regard to many aspects, starting with 'phenotype definition'. In our report we included only patients fulfilling the American College of Rheumatology criteria for the classification of systemic sclerosis (SSc), while Kristen and colleagues also included 19% of early SSc patients according to LeRoy's definition [5]; we also had 75% limited cutaneous SSc patients compared to 50% in the German population. This different phenotype definition implies that the sets of causative loci or traits underlying the different definitions are likely to be different [3]. Moreover, the prevalence of females in our population was much higher (93.9% versus 50%) and it is well-known that platelets differently aggregate in males and females due to hormonal and gender-specific influences [6]. As we hypothesized that the rs6314 polymorphism does not act as a causative genetic mutation per se, but rather it is important in amplifying SSc-causative and coagulative pathological processes once they have already been triggered by other factors [1], all the above-mentioned and other hidden differences in the genetic background are likely to be of particular relevance. In this sense, it is reductive to consider the importance of the studied single nucleotide polymorphism on SSc susceptibility only for its main independent effect, but it should more appropriately be viewed in the context of a broader gene-gene or gene-environmental frame.

Basic research has shown that serotonin plays an important role in memory formation. Accordingly, genetic variation of serotonin receptors can be expected to affect memory and to underlie, in part, the heritability of memory capacity. A study by de Quervain and colleagues found a highly significant association of the functional 5-HT2A receptor variant His452Tyr (rs6314) with long-term memory. We replicated this finding in a cohort of 133 adults (mean age 43.5 yr). Carriers of the Tyr allele showed poorer verbal delayed recall and recognition, while immediate recall and additional measures of attentional and executive function were not affected by the His452Tyr genotype. Results suggest a possible role of 5-HT2A receptors in memory consolidation. Serotonergic drugs may have the potential to improve memory.

Recently, two naturally occurring amino acid substitutions were identified in the C-terminal region of the serotonin 5-HT 2A receptor. One of these, His 452 Tyr, has a rarer allele Tyr frequency of 9%. If 452 Tyr alters 5-HT 2 function, it would thus be a candidate allele for human neurobehavioral variation. The present study was designed to evaluate the potential influence of the 452 His and 452 Tyr alleles on cellular 5-HT 2A functions. Platelet 5-HT 2A binding and 5-HT-induced Ca 2+ response were compared in eight 452 His/ 452 His homozygous and eight 452 His/ 452 Tyr heterozygous individuals matched for sex, age, and diagnosis (all were patients with seasonal affective disorder). There was no difference in 5-HT 2A binding measured using 125 I-lysergic acid diethylamide. Nor were levels of G-protein subunits or PKC α, δ, e, or ζ significantly altered. However, when Ca 2+ response was stimulated by 2, 5, 10, or 25 μM 5-HT, significant differences were found. In 452 His/ 452 Tyr heterozygotes, 452 Tyr was associated with both smaller peak amplitude in Ca 2+ mobilization and a different time course of response, with slower peak latency and longer half-time in 452 His/ 452 Tyr heterozygotes compared with 452 His/ 452 His homozygotes. The overall difference in the response of the 5-HT 2 receptor in individuals with 452 Tyr was a blunting of the shape of the Ca 2+ mobilization peak. The data reported here suggest that the primary sequence of this intracellular domain is important in function of the receptor and that the 452 His and 452 Tyr 5-HT 2A alleles should be carefully evaluated for effects on human neurobehavioral variation.