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1.  Effects of HTR1A C(-1019)G on Amygdala Reactivity & Trait Anxiety 
Archives of general psychiatry  2009;66(1):33-40.
Background
5-HT1A autoreceptors mediate negative feedback inhibition of serotonergic neurons and play a critical role in regulating 5-HT signaling involved in shaping the functional response of major forebrain targets, such as the amygdala, supporting complex behavioral processes. A common functional variation (C(-1019)G) in the human 5-HT1A gene (HTR1A) represents one potential source of such inter-individual variability. Both in vitro and in vivo the -1019G blocks transcriptional repression leading to increased autoreceptor expression. Thus, the -1019G may contribute to relatively decreased 5-HT signaling at postsynaptic forebrain target sites via increased negative feedback.
Objectives & Design
To use imaging genetics to evaluate the effects of HTR1A C(-1019)G on amygdala reactivity in 89 healthy adults and employ path analyses to explore the impact of HTR1A-mediated variability in amygdala reactivity on individual differences in trait anxiety. We hypothesized that the -1019G, which potentially results in decreased 5-HT signaling, would be associated with relatively decreased amygdala reactivity and related trait anxiety.
Results
Consistent with prior findings, the -1019G was associated with significantly decreased threat-related amygdala reactivity. Importantly, this effect was independent of that associated with another common functional polymorphism impacting 5-HT signaling, namely the 5-HTTLPR. While there were no direct genotype effects on trait anxiety, the HTR1A C(-1019)G indirectly predicted 9.2% of interindividual variability in trait anxiety through its effects on amygdala reactivity.
Conclusions
Our findings further implicate relatively increased 5-HT signaling, associated with genetic variation mediating increased 5-HT1A autoreceptors, in driving amygdala reactivity and trait anxiety. Moreover, they provide empirical documentation of the basic premise that genetic variation impacts emergent behavioral processes related to psychiatric disease risk indirectly by biasing the response of underlying neural circuitries.
doi:10.1001/archpsyc.66.1.33
PMCID: PMC2736132  PMID: 19124686
2.  Do Menopausal Status and Use of Hormone Therapy Affect Antidepressant Treatment Response? Findings from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) Study 
Journal of Women's Health  2013;22(2):121-131.
Abstract
Background
Menopausal status and use of hormonal contraception or menopausal hormone therapy (HT) may affect treatment response to selective serotonin reuptake inhibitors (SSRIs). This report evaluates whether menopausal status and use of hormonal contraceptives or menopausal HT affect outcome in women treated with citalopram.
Methods
In the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study, 896 premenopausal and 544 postmenopausal women were treated with citalopram for 12–14 weeks. Baseline demographic and clinical characteristics were used in adjusted analysis of the effect of menopausal status and use of hormonal contraceptives or menopausal HT on outcomes. Remission was defined as final Hamilton Rating Scale for Depression-17 (HRSD17) ≤7 or Quick Inventory of Depressive Symptomatology-Self-Report (QIDS-SR16) score ≤5 and response as ≥50% decrease from the baseline QIDS-SR16 score.
Results
Premenopausal and postmenopausal women differed in multiple clinical and demographic baseline variables but did not differ in response or remission rates. Premenopausal women taking hormonal contraceptives had significantly greater unadjusted remission rates on the HRSD17 and the QIDS-SR16 than women not taking contraception. Response and remission rates were not different between postmenopausal women taking vs. not taking HT. Adjusted results showed no significant difference in any outcome measure across menopause status in women who were not taking contraception/HT. There were no significant differences in adjusted results across HT status in premenopausal or postmenopausal women.
Conclusions
In this study, citalopram treatment outcome was not affected by menopausal status. Hormonal contraceptives and HT also did not affect probability of good outcome.
doi:10.1089/jwh.2012.3479
PMCID: PMC3613168  PMID: 23398127
3.  Role of HtrA in Growth and Competence of Streptococcus mutans UA159 
Journal of Bacteriology  2005;187(9):3028-3038.
We report here that HtrA plays a role in controlling growth and competence development for genetic transformation in Streptococcus mutans. Disruption of the gene for HtrA resulted in slow growth at 37°C, reduced thermal tolerance at 42°C, and altered sucrose-dependent biofilm formation on polystyrene surfaces. The htrA mutant also displayed a significantly reduced ability to undergo genetic transformation. A direct association between HtrA and genetic competence was demonstrated by the increased expression of the htrA gene upon exposure to competence-stimulating peptide. The induction of htrA gradually reached a maximum at around 20 min, suggesting that HtrA may be involved in a late competence response. Complementation of the htrA mutation in a single copy on the chromosome of the mutant could rescue the defective growth phenotypes but not transformability, apparently because a second gene, spo0J, immediately downstream of htrA, also affects transformation. The htrA and spo0J genes were shown to be both individually transcribed and cotranscribed and probably have a functional connection in competence development. HtrA regulation appears to be finely tuned in S. mutans, since strains containing multiple copies of htrA exhibited abnormal growth phenotypes. Collectively, the results reveal HtrA to be an integral component of the regulatory network connecting cellular growth, stress tolerance, biofilm formation, and competence development and reveal a novel role for the spo0J gene in genetic transformation.
doi:10.1128/JB.187.9.3028-3038.2005
PMCID: PMC1082816  PMID: 15838029
4.  Serotonin-1A Receptor Polymorphism (rs6295) Associated with Thermal Pain Perception 
PLoS ONE  2012;7(8):e43221.
Background
Serotonin (5-HT) is highly involved in pain regulation and serotonin-1A (5-HT1A) receptors are important in determining central 5-HT tone. Accordingly, variation in the 5-HT1A receptor gene (HTR1A) may contribute to inter-individual differences in human pain sensitivity. The minor G-allele of the HTR1A single nucleotide polymorphism (SNP) rs6295 attenuates firing of serotonergic neurons and reduces postsynaptic expression of the receptor. Experiments in rodents suggest that 5-HT1A-agonism modulates pain in opposite directions at mild compared to high noxious intensities. Based upon this and several other similar observations, we hypothesized that G-carriers would exhibit a relative hypoalgesia at mild thermal stimuli but tend towards hyperalgesia at higher noxious intensities.
Methods
Fourty-nine healthy individuals were selectively genotyped for rs6295. Heat- and cold-pain thresholds were assessed along with VAS-ratings of a range of suprathreshold noxious heat intensities (45°C–49°C). Nociceptive-flexion reflex (NFR) thresholds were also assessed.
Results
Volunteers did not deviate significantly from Hardy-Weinberg equilibrium. G-carriers were less sensitive to threshold-level thermal pain. This relative hypoalgesia was abolished at suprathreshold noxious intensities where G-carriers instead increased their ratings of heat-pain significantly more than C-homozygotes. No differences with regard to NFR-thresholds emerged.
Conclusion/Significance
To the best of our knowledge this is the first study of human pain perception on the basis of variation in HTR1A. The results illustrate the importance of including a range of stimulus intensities in assessments of pain sensitivity. In speculation, we propose that an attenuated serotonergic tone may be related to a ‘hypo- to hyperalgesic’ response-pattern. The involved mechanisms could be of clinical interest as variation in pain regulation is known to influence the risk of developing pain pathologies. Further investigations are therefore warranted.
doi:10.1371/journal.pone.0043221
PMCID: PMC3432037  PMID: 22952650
5.  The serotonin 1A receptor C(-1019)G polymorphism in relation to suicide attempt 
Background
Serotonergic neurotransmission has been implicated in suicidal behavior. Association between suicidal completers and a regulatory C(-1019)G polymorphism (rs6295) in the serotonin 1A receptor (HTR1A) gene was previously reported, whereas a following study showed no association in a sample of suicide attempters.
Methods
The involvement of the implicated G-allele of the 5-HTR1A C(-1019)G polymorphism (rs6295) was analyzed with the transmission disequilibrium test (TDT) in a sample of 272 suicide attempter families.
Results
No overtransmission of the G-allele was found in the entire sample of suicide attempters (p = 0.1460; n = 272 trios). However, a strong trend for overtransmission of the G-allele was observed in a sub-sample selected for a high level of previous traumatic and/or stressful life events prior to the suicide attempt (p = 0.0630, two-tail; n = 94 trios).
Conclusion
The current results show that variation at the rs6295 polymorphism of the HTR1A gene is not associated with suicide attempts generally. However, the results indicate a possible role of the G-allele in suicidal behavior in connection with high exposure to traumatic and/or stressful life events, which is in need of future investigation.
doi:10.1186/1744-9081-2-14
PMCID: PMC1459178  PMID: 16626484
6.  Genetic Variation in HTR2A Influences Serotonin Transporter Binding Potential as Measured using PET and [11C]DASB 
In a previous study we showed that genetic variation in HTR2A, which encodes the serotonin 2A receptor, influenced outcome of citalopram treatment in patients with major depressive disorder (MDD). Since chronic administration of citalopram, which selectively and potently inhibits the serotonin transporter (5-HTT), putatively enhances serotonergic transmission, it is conceivable that genetic variation within HTR2A also influences pretreatment 5-HTT function or serotonergic transmission. The present study used positron emission tomography (PET) and the selective 5-HTT ligand, [11C]DASB, to investigate whether the HTR2A marker alleles that predict treatment outcome also predict differences in 5-HTT binding.
Brain levels of 5-HTT were assessed in vivo using PET measures of the nondisplaceable component of the [11C]DASB binding potential (BPND). DNA from 43 patients and healthy volunteers, all unmedicated, was genotyped with 14 single nucleotide polymorphisms (SNPs) located within or around HTR2A. Allelic association with BPND was assessed in 8 brain regions, with covariates to control for race and ethnicity.
We detected allelic association between [11C]DASB BPND in thalamus and 3 markers in a region spanning the 3′ untranslated region and second intron of HTR2A (rs7333412, p=0.000045; rs7997012, p= 0.000086; rs977003, p=0.000069). The association signal at rs7333412 remained significant (p<0.05) after applying corrections for multiple testing via permutation.
Genetic variation in HTR2A that previously was associated with citalopram treatment outcome also was associated with thalamic 5-HTT binding. While further work is needed to identify the actual functional genetic variants involved, these results suggest that a relationship exists between genetic variation in HTR2A and either 5-HTT expression or central serotonergic transmission that influences the therapeutic response to 5-HTT inhibition in major depression.
doi:10.1017/S1461145709991027
PMCID: PMC3810474  PMID: 20047709
Genetic Association; Positron Emission Tomography; Serotonin Transporter; [11C]DASB; HTR2A
7.  Pharmacogenetics Studies in STAR*D: Strengths, Limitations, and Results 
Several lines of evidence support an important genetic contribution to the wide individual variation in therapeutic response to antidepressant medications. The Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study provided the largest cohort assembled to date of DNA from patients with nonpsychotic major depressive disorder, uniformly treated with citalopram and followed prospectively for up to 12 weeks. This pivotal study changed the face of pharmacogenetics research by increasing the sample size by an order of magnitude as well as by providing detailed prospective information about antidepressant response and tolerability. Several groups have identified markers in genes and tested the replication of previous findings of genes associated with outcome and side effects of antidepressant treatment. Variants in HTR2A, GRIK4, and KCNK2 were associated with citalopram treatment outcome. Replication was achieved in markers in the FKBP5 gene. Other findings in PDE11A and BDNF were not successfully replicated, and reports of potential confounders in previous associations with serotonin transporter variation (SLC6A4) were identified. Polymorphisms in pharmacokinetic genes involved in metabolism and transmembrane transport were also not associated with antidepressant response. Adverse events were also tested. Treatment-emergent suicidal ideation was associated with GRIK2, GRIA3, PAPLN, IL28RA, and CREB1. Sexual dysfunction was linked with variation in GRIN3A, GRIA1 GRIA3, and GRIK2. Reported and future findings of pharmacogenetics studies in STAR*D could help elucidate pathways involved in major depression and those pertinent to antidepressant outcome and side effects. Replication of these findings in independent samples could lead to the development of new treatments and to optimization of available treatments.
doi:10.1176/appi.ps.60.11.1446
PMCID: PMC3775610  PMID: 19880459
8.  Transcriptional regulation of the 5-HT1A receptor: implications for mental illness 
The serotonin-1A (5-HT1A) receptor is an abundant post-synaptic 5-HT receptor (heteroreceptor) implicated in regulation of mood, emotion and stress responses and is the major somatodendritic autoreceptor that negatively regulates 5-HT neuronal activity. Based on animal models, an integrated model for opposing roles of pre- and post-synaptic 5-HT1A receptors in anxiety and depression phenotypes and response to antidepressants is proposed. Understanding differential transcriptional regulation of pre- versus post-synaptic 5-HT1A receptors could provide better tools for their selective regulation. This review examines the transcription factors that regulate brain region-specific basal and stress-induced expression of the 5-HT1A receptor gene (Htr1a). A functional polymorphism, rs6295 in the Htr1a promoter region, blocks the function of specific repressors Hes1, Hes5 and Deaf1, resulting in increased 5-HT1A autoreceptor expression in animal models and humans. Its association with altered 5-HT1A expression, depression, anxiety and antidepressant response are related to genotype frequency in different populations, sample homogeneity, disease outcome measures and severity. Preliminary evidence from gene × environment studies suggests the potential for synergistic interaction of stress-mediated repression of 5-HT1A heteroreceptors, and rs6295-induced upregulation of 5-HT1A autoreceptors. Targeted therapeutics to inhibit 5-HT1A autoreceptor expression and induce 5-HT1A heteroreceptor expression may ameliorate treatment of anxiety and major depression.
doi:10.1098/rstb.2011.0376
PMCID: PMC3405675  PMID: 22826341
serotonin; transcription; receptor; raphe; anxiety; depression
9.  Catechol O-methyltransferase pharmacogenomics and selective serotonin reuptake inhibitor response 
The Pharmacogenomics Journal  2010;12(1):78-85.
We applied a systematic pharmacogenetic approach to investigate the role of genetic variation in the gene encoding catechol O-methyltransferase (COMT) in individual variation in selective serotonin reuptake inhibitor (SSRI) response among depressed patients. Twenty-three single nucleotide polymorphisms (SNPs) in COMT were genotyped using DNA from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study (N=1914). One SNP, rs13306278, located in the distal promoter region of COMT, showed significant association with remission in White Non-Hispanic (WNH) subjects (P = 0.038). Electromobility shift assay for rs13306278 showed alternation in the ability of the variant sequence to bind nuclear proteins. A replication study was performed using samples from the Mayo Clinic PGRN Citalopram/Escitalopram Pharmacogenomic study (N=422) that demonstrated a similar trend for association. Our findings suggest that novel genetic markers in the COMT distal promoter may influence SSRI response phenotypes.
doi:10.1038/tpj.2010.69
PMCID: PMC3113454  PMID: 20877297
Pharmacogenetics; catechol O-methyltransferase; COMT; selective serotonin reuptake inhibitor; major depressive disorder; STAR*D
10.  Genetic Polymorphisms in the HTR2C and Peroxisome Proliferator-Activated Receptors Are Not Associated with Metabolic Syndrome in Patients with Schizophrenia Taking Clozapine 
Psychiatry Investigation  2011;8(3):262-268.
Objective
Genetic variation in the serotonin-2C receptor encoded by the HTR2C gene is one of the genetic determinants of antipsychotic-induced weight gain. Peroxisome proliferator-activated receptors are nuclear receptors regulating the expression of genes involved in lipid and glucose metabolism. In this cross-sectional study, we investigated whether HTR2C-759C/T, HTR2C-697G/C, PPARα V227A, and PPARγ 161C/T genotypes were associated with metabolic syndrome (MetS) in patients with schizophrenia taking clozapine.
Methods
One hundred forty-six Korean patients using clozapine for more than one year were genotyped for the HTR2C-759C/T, HTR2C-697G/C, PPARα V227A, and PPARγ 161C/T polymorphisms, and their weight, waist circumference, blood pressure, triglycerides, high-density lipoprotein-cholesterol, total cholesterol, and glucose were measured. We used the criteria for MetS proposed by the National Cholesterol Education Program-adapted Adult Treatment Panel III.
Results
The prevalence of MetS was 47.3% and was similar among men (49%) and women (42.9%). We found no significant differences between patients with and without MetS in terms of genotypes or allele frequencies. Logistic regression analyses also revealed no association between MetS and each genotype.
Conclusion
We did not find significant associations between four polymorphisms (HTR2C-759C/T, HTR2C-697G/C, PPARα V227A, and PPARγ 161C/T) and MetS in patients with schizophrenia taking clozapine.
doi:10.4306/pi.2011.8.3.262
PMCID: PMC3182393  PMID: 21994515
Metabolic syndrome; Clozapine; HTR2C; PPAR; Polymorphism; Schizophrenia
11.  Polymorphisms in GRIK4, HTR2A, and FKBP5 Show Interactive Effects in Predicting Remission to Antidepressant Treatment 
Neuropsychopharmacology  2009;35(3):727-740.
Single-nucleotide polymorphisms (SNPs) in the FKBP5, GRIK4, and HTR2A genes have been shown to be associated with response to citalopram treatment in the STAR*D sample, but only associations with FKBP5 have so far been tested in the Munich Antidepressant Response Signature (MARS) project. Response and remission of depressive symptoms after 5 weeks of antidepressant treatment were tested against 82 GRIK4 and 37 HTR2A SNPs. Association analysis was conducted in about 300 depressed patients from the MARS project, 10% of whom had bipolar disorder. The most predictive SNPs from these two genes and rs1360780 in FKBP5 were then genotyped in a total of 387 German depressed in-patients to analyze potential additive and interactive effects of these variants. We could not replicate previous findings of the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study in our sample. Although not statistically significant, the effect for the best GRIK4 SNP of STAR*D (rs1954787, p=0.076, pcorrected=0.98) seemed to be in the same direction. On the other hand, the nominally significant association with the top HTR2A SNPs of STAR*D (rs7997012, allelic, p=0.043, pcorrected=0.62) was with the opposite risk allele. The GRIK4 SNP (rs12800734, genotypic, p=0.0019, pcorrected=0.12) and the HTR2A SNP (rs17288723, genotypic, p=0.0011, pcorrected=0.02), which showed the strongest association with remission in our sample, had not been reported previously. Associations across all genetic markers within the GRIK4 (genotypic, p=0.022) or HTR2A (genotypic, p=0.012) locus using the Fisher's product method (FPM) were also significant. In all 374 patients, the best predictive model included a main effect for GRIK4 rs12800734 and two significant interactions between GRIK4 rs12800734 and FKBP5 rs1360780, and GRIK4 rs12800734 and HTR2A rs17288723. This three SNP model explained 13.1% of the variance for remission after 5 weeks (p=0.00051 for the model). Analyzing a sub-sample of 194 patients, plasma ACTH (p=0.002) and cortisol (p=0.021) responses of rs12800734 GG (GRIK4) carriers, who also showed favorable treatment response, were significantly lower in the second combined dexamethasone (dex)/corticotrophin-releasing hormone (CRH) test before discharge compared with the other two genotype groups. Despite large differences in ethnicity and design compared with the STAR*D study, our results from the MARS study further support both independent and interactive involvement of GRIK4, HTR2A and FKBP5 in antidepressant treatment response.
doi:10.1038/npp.2009.180
PMCID: PMC3055621  PMID: 19924111
GRIK4; HTR2A; FKBP5; interaction; antidepressant treatment response; affective disorder; Pharmacogenetics/Pharmacogenomics; Depression; Unipolar/Bipolar; Glutamate; Serotonin; GRIK4; HTR2A; FKBP5; pharmacogenetic; antidepressant treatment response
12.  Association Between 5HT1b Receptor Gene and Methamphetamine Dependence 
Current Neuropharmacology  2011;9(1):163-168.
Several lines of evidence implicate serotonergic dysfunction in diverse psychiatric disorders including anxiety, depression, and drug abuse. Mice with a knock-out of the 5HT1b receptor gene (HTR1B) displayed increased locomotor response to cocaine and elevated motivation to self-administer cocaine and alcohol. Previous genetic studies showed significant associations of HTR1B with alcohol dependence and substance abuse, but were followed by inconsistent results. We examined a case-control genetic association study of HTR1B with methamphetamine-dependence patients in a Japanese population. The subjects were 231 patients with methamphetamine dependence, 214 of whom had a co-morbidity of methamphetamine psychosis, and 248 age- and sex-matched healthy controls. The three single nucleotide polymorphisms (SNPs), rs130058 (A-165T), rs1228814 (A-700C) and rs1228814 (A+1180G) of HTR1B were genotyped. There was no significant difference in allelic and genotypic distributions of the SNPs between methamphetamine dependence and the control. Genetic associations of HTR1B were tested with several clinical phenotypes of methamphetamine dependence and/or psychosis, such as age at first abuse, duration of latency from the first abuse to onset of psychosis, prognosis of psychosis after therapy, and complication of spontaneous relapse of psychotic state. There was, however, no asscocation between any SNP and the clinical phenotypes. Haplotype analyses showed the three SNPs examined were within linkage disequilibrium, which implied that the three SNPs covered the whole HTR1B, and distribution of estimated haplotype frequency was not different between the groups. The present findings may indicate that HTR1B does not play a major role in individual susceptibility to methamphetamine dependence or development of methamphetamine-induced psychosis.
doi:10.2174/157015911795017137
PMCID: PMC3137174  PMID: 21886584
Methamphetamine dependence; association study; HTR1B; haplotype.
13.  No Effect of Serotoninergic Gene Variants on Response to Interpersonal Counseling and Antidepressants in Major Depression 
Psychiatry Investigation  2013;10(2):180-189.
Objective
Gene variants within the serotonin pathway have been associated with major depressive disorder (MDD) treatment outcomes, however a possible different modulation on pharmacological or psychological treatments has never been investigated.
Methods
One hundred sixty MDD patients were partially randomized to either inter-personal counseling (IPC) or antidepressants. The primary outcome was remission at week 8. Five serotonergic polymorphisms were investigated (COMT rs4680, HTR1A rs6295, HTR2A rs2224721, HTR2A rs7997012 and SLC6A4 rs421417).
Results
IPC (n=43) and antidepressant (n=117) treated patients did not show any difference in remission rates at week 8 (corrected for baseline severity, age and center). None of the studied gene variants impacted on response and remission rates at week 8 neither in the IPC nor in the antidepressant group. An analysis of the whole sample showed a trend of association between rs7997012 AA genotype and a better treatment outcome.
Conclusion
Our study confirms that IPC is an effective psychological intervention comparable to antidepressants in mild-moderate MDD. Polymorphisms related to the serotonin system did not exert a major effect on clinical outcomes in none of the treatment groups.
doi:10.4306/pi.2013.10.2.180
PMCID: PMC3687053  PMID: 23798967
Antidepressants; Psychotherapy; 5-HT; 5-HT1A receptor; 5-HT2A receptor; Serotonin transporter; COMT; Genes; Polymorphism; Major depression
14.  Polymorphisms of the serotonin transporter and receptor genes: susceptibility to substance abuse 
Serotonin (5-hydroxytryptamine [5-HT]) is an important neurotransmitter implicated in regulating substance-use disorder (SUD) acquisition, maintenance, and recovery. During the past several years, an abundance of research has begun discovering and describing specific 5-HT genetic polymorphisms associated with SUDs. Genetic variations in the 5-HT system, such as SLC6A4, HTR1B, HTR2A, HTR2C, HTR3 (HTR3A, HTR3B, HTR3C, HTR3D, and HTR3E), likely play a role contributing to SUD patient heterogeneity. The 5-HT transporter-linked polymorphic region S allele, located in SLC6A4, has now been modestly associated with alcohol dependence in two large meta-analyses. Additional 5-HT genes may also play a role but have not been extensively investigated. A limited number of SUD treatment studies have included 5-HT gene variation as moderating treatment outcomes, but the results have been equivocal. Future research on 5-HT addiction genetics should adopt whole-genome sequencing technology, utilize large study samples, and collect data from multiple ethnic groups. Together, these methods will build on the work already conducted with the aim of utilizing 5-HT genetics in SUD treatment settings.
doi:10.2147/SAR.S25864
PMCID: PMC3427938  PMID: 22933845
serotonin; genetic; substance dependence; addiction; alcohol; drug
15.  Polymorphisms of the serotonin transporter and receptor genes: susceptibility to substance abuse 
Serotonin (5-hydroxytryptamine [5-HT]) is an important neurotransmitter implicated in regulating substance-use disorder (SUD) acquisition, maintenance, and recovery. During the past several years, an abundance of research has begun discovering and describing specific 5-HT genetic polymorphisms associated with SUDs. Genetic variations in the 5-HT system, such as SLC6A4, HTR1B, HTR2A, HTR2C, HTR3 (HTR3A, HTR3B, HTR3C, HTR3D, and HTR3E), likely play a role contributing to SUD patient heterogeneity. The 5-HT transporter-linked polymorphic region S allele, located in SLC6A4, has now been modestly associated with alcohol dependence in two large meta-analyses. Additional 5-HT genes may also play a role but have not been extensively investigated. A limited number of SUD treatment studies have included 5-HT gene variation as moderating treatment outcomes, but the results have been equivocal. Future research on 5-HT addiction genetics should adopt whole-genome sequencing technology, utilize large study samples, and collect data from multiple ethnic groups. Together, these methods will build on the work already conducted with the aim of utilizing 5-HT genetics in SUD treatment settings.
doi:10.2147/SAR.S25864
PMCID: PMC3427938  PMID: 22933845
serotonin; genetic; substance dependence; addiction; alcohol; drug
16.  Serotonin receptor expression along the dorsal–ventral axis of mouse hippocampus 
Using in situ hybridization, we describe, for the first time, the profiles of expression of serotonin receptors (Htr/5-HTR) along the dorsal–ventral axis of mouse hippocampus. cRNA probes for most Htrs, excluding Htr6, were used. All hippocampal subregions and the entorhinal cortex cells providing input into the hippocampus were examined. The study shows that some, but not all, Htrs are expressed in the cells of the hippocampal circuitry. At both the subfield and the cell type levels, a somewhat overlapping pattern is observed. Four serotonin receptors, Htr1a, Htr2a, Htr2c and Htr7, display an expression pattern that changes along the dorsal–ventral axis of the hippocampus. Given the proposed functional differentiation of the hippocampus along its long axis, with the dorsal pole more involved in cognitive functions and the ventral pole more involved in mood and anxiety, our results suggest that serotonin receptors enriched in the ventral pole probably contribute to mood- and anxiety-related behaviours.
doi:10.1098/rstb.2012.0038
PMCID: PMC3405677  PMID: 22826340
serotonin; hippocampus; antidepressant
17.  Pharmacogenetic predictors of nausea and vomiting of pregnancy severity and response to antiemetic therapy: a pilot study 
Background
Nausea and vomiting of pregnancy (NVP) is a common condition. The objective of this study was to evaluate the association between response to antiemetics in the treatment of NVP and genetic polymorphisms in the serotonin receptor subunit genes HTR3A and HTR3B.
Methods
Pregnant women ≥18 years of age with NVP starting antiemetic therapy with promethazine, prochlorperazine, metoclopramide, or ondansetron at ≤ 16 weeks gestational age were eligible. The study recruited 29 women with complete data and sampling who returned for their one week follow-up and were genotyped for HTR3A and HTR3B polymorphisms. Severity of NVP was captured (using Pregnancy Unique Quantification of Emesis (PUQE) and Quality of Life (QOL) tools) upon enrollment and after one week of antiemetic therapy. These measures were correlated with pharmacogenetic variability.
Results
Subjects with genotype associated with high serotonin affinity of the 5-HT3B receptor (rs1176744, CC) required more antiemetic medications (p < 0.001) than other subjects. Those with genotypes associated with increased expression of the 5-HT3A receptor subunit (rs1062613, CT or TT) had worse final PUQE scores (p = 0.01) than other subjects while rs3782025 variants carriers had significantly better initial (p = 0.02) and final (p = 0.02) PUQE scores than other subjects.
Conclusions
HTR3B and HTR3A gene variants may contribute to variability in response to antiemetic therapy for NVP.
doi:10.1186/1471-2393-13-132
PMCID: PMC3693967  PMID: 23786674
Pregnancy; Nausea and vomiting of pregnancy; Antiemetics; Pharmacogenomics
18.  Editing of the Serotonin 2C Receptor Pre-mRNA: Effects of the Morris Water Maze 
Gene  2007;391(1-2):186-197.
The pre-mRNA encoding the serotonin 2C receptor, HTR2C (official mouse gene symbol, Htr2c), is subject to adenosine deamination that produces inosine at five sites within the coding region. Combinations of this site-specific A-to-I editing can produce 32 different mRNA sequences encoding 24 different protein isoforms with differing biochemical and pharmacological properties. Studies in humans have reported abnormalities in patterns of HTR2C editing in psychiatric disorders, and studies in rodents show altered patterns of editing in response to drug treatments and stressful situations. To further explore the biological significance of editing of the Htr2c mRNA and its regulation, we have examined patterns of Htr2c editing in C57BL/6J mice after exposure to the hidden platform version of the Morris Water Maze, a test of spatial learning that, in mice, is also associated with stress. In brains of both swimming controls and mice trained to find the platform, subtle time dependent changes in editing patterns are seen as soon as one hour after a probe trial and typically last less than 24 hours. Changes in whole brain with cerebellum removed differ from those seen in isolated hippocampus and cortex. Unexpectedly, in hippocampi from subsets of mice, abnormally low levels of editing were seen that were not correlated with behavior or with editing levels in cortex. These data implicate responses to spatial learning and stress, in addition to stochastic processes, in the generation of subtle changes in editing patterns of Htr2c.
doi:10.1016/j.gene.2006.12.023
PMCID: PMC2677018  PMID: 17307311
5HT2C receptor; inosine; protein isoforms; primer extension; spatial learning; stress
19.  Resequencing of serotonin-related genes and association of tagging SNPs to citalopram response 
Pharmacogenetics and genomics  2009;19(1):1-10.
Several reports have been published investigating the relationship between common variants in serotonin-related candidate genes and antidepressant response, and most of the results have been equivocal. We previously reported a significant association between variants in serotonin-related genes and response to the selective serotonin reuptake inhibitor fluoxetine. Here, we attempt to expand upon and replicate these results by (i) resequencing the exonic and putatively regulatory regions of five serotonin-related candidate genes (HTR1A, HTR2A, TPH1, TPH2, and MAOA) in our fluoxetine-treated sample to uncover novel variants; (ii) selecting tagging single nucleotide polymorphisms (SNPs) for these genes from the resequencing data; and (iii) evaluating these tagging SNPs for association with response to the selective serotonin reuptake inhibitor citalopram in an independent sample of participants who are enrolled in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) clinical study (N=1953). None of the variants associated previously with fluoxetine response were found to be associated with citalopram response in the STAR*D sample set. Nor were any of the additional tagging SNPs found to be associated with citalopram response. An additional SNP in HTR2A (rs7997012), previously reported to be associated with outcome of citalopram treatment in this sample, but not well tagged by any of the other SNPs we studied, was also genotyped, and was associated with citalopram response (P=0.0002), strongly supporting the previous observation in the same STAR*D sample. Our results suggest that resequencing the serotonin-related genes did not identify any additional common SNPs that have not been identified previously. It appears that genetic variation in these five genes has a marginal effect on response to citalopram, although a previously observed association was supported and awaits replication in an independent sample.
doi:10.1097/FPC.0b013e3283163ecd
PMCID: PMC2896826  PMID: 19077664
association; citalopram; fluoxetine; pharmacogenetics; single nucleotide polymorphism
20.  Association Study Between the Serotonin 1A Receptor (HTR1A) Gene and Neuroticism, Major Depression, and Anxiety Disorders 
The serotonin neurotransmitter system in general, and the serotonin 1A receptor in particular, has been broadly implicated in the pathophysiology of mood and anxiety disorders, although the results of genetic association studies have been mixed. In this study, we examined the serotonin 1A receptor gene, HTR1A, for its association with shared genetic risk across a range of anxiety and depression-related phenotypes. Using multivariate structural equation modeling, we selected twin pairs from the population-based Virginia Adult Twin Study of Psychiatric and Substance Use Disorders scoring at the extremes of a latent genetic risk factor that underlies susceptibility to neuroticism, major depression, and several anxiety disorders. One member from each selected pair was entered into a 2-stage, case-control association study for the HTR1A gene. In the resulting sample of 589 cases and 539 controls, four SNPs spanning the HTR1A locus, including the C(−1019)G functional promoter polymorphism (rs6295), were screened in stage 1, the positive results of which were tested for replication in stage 2. While one marker met threshold significance criteria in stage 1, this association was not replicated in stage 2. Post-hoc analyses did not reveal association to any of the specific psychiatric phenotypes. Our data suggests that the HTR1A gene may not play a major role in the genetic susceptibility underlying depressive and anxiety-related phenotypes.
doi:10.1002/ajmg.b.30656
PMCID: PMC2859302  PMID: 18163385
serotonin; depression; anxiety; personality; association study; genetics
21.  Sertraline for the Treatment of Depression in Alzheimer Disease: Genetic Influences 
Objective
To assess the potential for genetic influences on sertraline treatment efficacy for depression of Alzheimer disease (dAD). Four functional genetic variants were studied: 2 serotonin receptors (HTR2A-T102C and HTR2C-Cys23Ser), the serotonin transporter (5HTT-LPR), and brain-derived neurotrophic factor (BDNF-Val66Met). Treatment response by genotype was measured by (1) the modified Alzheimer’s Disease Cooperative Study Clinical Global Impression of Change, (2) the Cornell scale for Depression in Dementia, and (3) remission of depression.
Methods
We utilized data from the Depression in Alzheimer’s Disease Study 2 (DIADS-2), a 24-week, randomized, multicenter trial showing no significant treatment effect of sertraline on dAD. Proportional odds logistic regression and mixed effects models were used to examine the above mentioned outcome measures.
Results
No significant interactions were seen between any of the genetic polymorphisms and the selected outcomes above at 12 or 24 weeks.
Discussion
Treatment outcomes in the DIADS-2 trial were not significantly influenced by genetic variation at the loci that were assessed. Future studies should continue to examine the interaction of depression-related genetic variants with antidepressant treatment in Alzheimer disease patients with depression.
doi:10.1177/0891988711422527
PMCID: PMC3535452  PMID: 22228829
Alzheimer disease; sertraline; depression; randomized trial; dementia; antidepressant
22.  Comparative Analysis of the Roles of HtrA-Like Surface Proteases in Two Virulent Staphylococcus aureus Strains  
Infection and Immunity  2005;73(1):563-572.
The HtrA surface protease is involved in the virulence of many pathogens, mainly by its role in stress resistance and bacterial survival. Staphylococcus aureus encodes two putative HtrA-like proteases, referred to as HtrA1 and HtrA2. To investigate the roles of HtrA proteins in S. aureus, we constructed htrA1, htrA2, and htrA1 htrA2 insertion mutants in two genetically different virulent strains, RN6390 and COL. In the RN6390 context, htrA1 inactivation resulted in sensitivity to puromycin-induced stress. The RN6390 htrA1 htrA2 mutant was affected in the expression of several secreted virulence factors comprising the agr regulon. This observation was correlated with the disappearance of the agr RNA III transcript in the RN6390 htrA1 htrA2 mutant. The virulence of this mutant was diminished in a rat model of endocarditis. In the COL context, both HtrA1 and HtrA2 were essential for thermal stress survival. However, only HtrA1 had a slight effect on exoprotein expression. The htrA mutations did not diminish the virulence of the COL strain in the rat model of endocarditis. Our results indicate that HtrA proteins have different roles in S. aureus according to the strain, probably depending on specific differences in the regulation of virulence factor and stress protein expression. We propose that HtrA1 and HtrA2 contribute to pathogenicity by controlling the production of certain extracellular factors that are crucial for bacterial dissemination, as revealed in the RN6390 background. We speculate that HtrA proteins act in the agr-dependent regulation pathway by assuring folding and/or maturation of some surface components of the agr system.
doi:10.1128/IAI.73.1.563-572.2005
PMCID: PMC538960  PMID: 15618196
23.  The role of the serotonergic system in suicidal behavior 
Serotonin is a widely investigated neurotransmitter in several psychopathologies, including suicidal behavior (SB); however, its role extends to several physiological functions involving the nervous system, as well as the gastrointestinal and cardiovascular systems. This review summarizes recent research into ten serotonergic genes related to SB. These genes – TPH1, TPH2, SLC6A4, SLC18A2, HTR1A, HTR1B, HTR2A, DDC, MAOA, and MAOB – encode proteins that are vital to serotonergic function: tryptophan hydroxylase; the serotonin transporter 5-HTT; the vesicular transporter VMAT2; the HTR1A, HTR1B, and HTR2A receptors; the L-amino acid decarboxylase; and the monoamine oxidases. This review employed a systematic search strategy and a narrative research methodology to disseminate the current literature investigating the link between SB and serotonin.
doi:10.2147/NDT.S50300
PMCID: PMC3825712  PMID: 24235834
serotonin; suicide; genetic
24.  An Evaluation of the Quick Inventory of Depressive Symptomatology and the Hamilton Rating Scale for Depression: A Sequenced Treatment Alternatives to Relieve Depression Trial Report 
Biological psychiatry  2005;59(6):493-501.
Background
Nine DSM-IV-TR criterion symptom domains are evaluated to diagnose major depressive disorder (MDD). The Quick Inventory of Depressive Symptomatology (QIDS) provides an efficient assessment of these domains and is available as a clinician rating (QIDS-C16), a self-report (QIDS-SR16), and in an automated, interactive voice response (IVR) (QIDS-IVR16) telephone system. This report compares the performance of these three versions of the QIDS and the 17-item Hamilton Rating Scale for Depression (HRSD17).
Methods
Data were acquired at baseline and exit from the first treatment step (citalopram) in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial. Outpatients with nonpsychotic MDD who completed all four ratings within ±2 days were identified from the first 1500 STAR*D subjects. Both item response theory and classical test theory analyses were conducted.
Results
The three methods for obtaining QIDS data produced consistent findings regarding relationships between the nine symptom domains and overall depression, demonstrating interchangeability among the three methods. The HRSD17, while generally satisfactory, rarely utilized the full range of item scores, and evidence suggested multidimensional measurement properties.
Conclusions
In nonpsychotic MDD outpatients without overt cognitive impairment, clinician assessment of depression severity using either the QIDS-C16 or HRSD17 may be successfully replaced by either the self-report or IVR version of the QIDS.
doi:10.1016/j.biopsych.2005.08.022
PMCID: PMC2929841  PMID: 16199008
Quick Inventory of Depressive Symptomatology; Inventory of Depressive Symptomatology; item response theory; Samejima graded response model; depressive symptoms
25.  Construction and characterization of a Yersinia enterocolitica O:8 high-temperature requirement (htrA) isogenic mutant. 
Infection and Immunity  1996;64(6):2088-2094.
The high-temperature requirement (HtrA) family of stress response proteins are induced by different environmental stress conditions in a variety of bacteria and have been shown to contribute to the pathogenicity of some of these species. In this study, the htrA gene from Yersinia enterocolitica O:8 was amplified, cloned, and sequenced. Analysis of the deduced amino acid sequence predicted that the putative HtrA homolog contains a serine protease active site and a catalytic triad characteristic of trypsin-like serine proteases, structural features characteristic of previously described HtrA proteins. In order to evaluate the biological functions of Y. enterocolitica HtrA, an isogenic mutant was constructed by a reverse-genetics PCR-based approach. Characterization of the mutant provided evidence supporting a stress response function for the Y. enterocolitica htrA gene product. In contrast to the parent strain, the mutant showed increased sensitivity to killing by H2O2, O2- and temperature stress (50 degrees C). The mutant was avirulent in the murine yersiniosis injection model and offered partial protection to mice challenged with the parent strain. Further studies with the Y. enterocolitica htrA mutant should increase our knowledge of the host-pathogen interactions which occur during Yersinia infections.
PMCID: PMC174040  PMID: 8675311

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