Genetic association analysis of serotonin 2A receptor gene (HTR2A) with bipolar disorder and major depressive disorder in the Japanese population

The role of serotonin in depression-A historical roundup and future directions

Depression is one of the most common psychiatric disorders worldwide, affecting approximately 280 million people, with probably much higher unrecorded cases. Depression is associated with symptoms such as anhedonia, feelings of hopelessness, sleep disturbances, and even suicidal thoughts. Tragically, more than 700 000 people commit suicide each year. Although depression has been studied for many decades, the exact mechanisms that lead to depression are still unknown, and available treatments only help a fraction of patients. In the late 1960s, the serotonin hypothesis was published, suggesting that serotonin is the key player in depressive disorders. However, this hypothesis is being increasingly doubted as there is evidence for the influence of other neurotransmitters, such as noradrenaline, glutamate, and dopamine, as well as larger systemic causes such as altered activity in the limbic network or inflammatory processes. In this narrative review, we aim to contribute to the ongoing debate on the involvement of serotonin in depression. We will review the evolution of antidepressant treatments, systemic research on depression over the years, and future research applications that will help to bridge the gap between systemic research and neurotransmitter dynamics using biosensors. These new tools in combination with systemic applications, will in the future provide a deeper understanding of the serotonergic dynamics in depression.

Early weaning modulates eating behavior and promotes hypofunction of the serotonergic (5HT) system in juvenile male rats

Early life stress (ELS) has been associated with developmental impairments. Early weaning (EW) is a postnatal stress model consisting of interruption of lactation and maternal care. The 5HT-system has been associated with neurobehavioral modulations promoted by ELS. Thus, the present work aims to investigate the effects of early weaning on feeding behavior and serotonergic system of juvenile male rats. For this, rats were submitted to early (PND15) or natural (PND30) weaning and had the body weight, food intake in circadian phases, and food intake in response to fenfluramine assessed. mRNA expression of serotoninergic receptors (5HT1A and 5HT2C) and transporter (SERT) was assessed in the hypothalamus and brainstem, as well as NPY and POMC mRNA expression in hypothalamus. The results show that early weaning promoted changes in the percentage of weight gain during lactation period and increase in body weight at PND40. It was also observed that EW promoted increase and decrease in food intake in light and dark phase, respectively, and leads to a decreased action of fenfluramine on inhibition of food intake. In addition, early weaning promoted increased NPY and SERT mRNA expression in the hypothalamus and 5HT2C in the brainstem. Together, the data indicate that the stress caused by early weaning impairs the eating behavior of juvenile male rats through hypofunction of the 5HT-system.

Associations Among Monoamine Neurotransmitter Pathways, Personality Traits, and Major Depressive Disorder

Major depressive disorder (MDD) is a complex psychiatric disease requiring multidisciplinary approaches to identify specific risk factors and establish more efficacious treatment strategies. Although the etiology and pathophysiology of MDD are not clear until these days, it is acknowledged that they are almost certainly multifactorial and comprehensive. Monoamine neurotransmitter system dysfunction and specific personality traits are independent risk factors for depression and suicide. These factors also demonstrate complex interactions that influence MDD pathogenesis and symptom expression. In this review, we assess these relationships with the aim of providing a reference for the development of precision medicine.

Association of HTR1A gene polymorphisms with obsessive-compulsive disorder and its treatment response: the influence of sex and clinical characteristics

OBJECTIVE

There have been controversial results in the literature on the association between HTR1A polymorphisms (rs10042486, C-1019G, and Gly272Asp) and obsessive-compulsive disorder (OCD). Here, the plausibility for such genetic and pharmacogenetic association was investigated by assessing a sample of Iranian OCD patients.

METHOD

OCD patients had fulfilled the criteria for DSM-IV-TR with Y-BOCS scores higher than 9. A total of 207 controls and 205 patients' blood samples were genotyped by means of PCR-RFLP.

RESULTS

The results showed that there was no association between these three SNPs and the treatment response. The distribution of rs10042486 genotypes was significantly different in the patients compared to the controls. The association analyses of the C-1019G showed significant differences in the genotypic frequency of the patients with or without a positive family history of psychiatric disorders. Similar differences in female patients were also observed. We found that the age of onset also associates with the C-1019G polymorphism but only in the female patients. No association of Gly272Asp polymorphism and OCD was observed in this study.

CONCLUSION

We concluded that among the HTR1A polymorphisms, only the association of rs10042486 CT genotype and OCD was statistically significant. The association of C-1019G with OCD by considering the age of onset and family history was just significant in the female patients. No significant association between the studied HTR1A SNPs with treatment response was observed. Acquiring both positive and negative pharmacogenetic outcomes in each population helps to select the appropriate medication for a particular patient with fewer side effects.

Serotonin 2A receptor (5-HT2A) gene promoter variant interacts with chronic perceived stress to modulate resting parasympathetic activity in humans

Decreased resting vagal (parasympathetic) tone is implicated in the development of stress-related disorders, including anxiety and depression. Chronic stress elevates the expression of serotonin 2A receptors (5-HT2A), while activation of 5-HT2A leads to inhibition of parasympathetic synaptic transmission. The T allele of the promoter variant, rs6311 (C>T), of the 5-HT2A gene has been shown to increase the 5-HT2A expression in vitro and to be associated with anxiety and depressive disorders. We thus hypothesized that the 5-HT2A functional polymorphism may influence resting vagal activity among persons with chronically high levels of perceived stress. A total of 1138 well-defined healthy, medication-free Han Chinese were included for 5-HT2A genotyping. The Perceived Stress Scale (PSS) was used to measure the level of perceived stress during the last month and participants were divided into low and high PSS groups. Resting-state heart rate variability (HRV) was used to assess autonomic function. No significant between-genotype difference was found in any HRV variable in the low PSS group (n=610). However, in the high PSS group (n=528), high frequency power and root mean square of successive heartbeat interval differences (both HRV indices of parasympathetic activity) were significantly reduced in T/T genotype carriers compared to C/C homozygotes. Our findings are the first to show that individuals homozygous for the high-expressing 5-HT2A (T) allele exhibit diminished resting vagal tone-an index of stress vulnerability-when experiencing chronically elevated levels of perceived stress. The present results may advance our understanding of the genetic mechanism underlying individual differences in susceptibility to stress.

Central serotonin-2A (5-HT2A) receptor dysfunction in depression and epilepsy: the missing link?

5-Hydroxytryptamine 2A receptors (5-HT_2A-Rs) are G-protein coupled receptors. In agreement with their location in the brain, they have been implicated not only in various central physiological functions including memory, sleep, nociception, eating and reward behaviors, but also in many neuropsychiatric disorders. Interestingly, a bidirectional link between depression and epilepsy is suspected since patients with depression and especially suicide attempters have an increased seizure risk, while a significant percentage of epileptic patients suffer from depression. Such epidemiological data led us to hypothesize that both pathologies may share common anatomical and neurobiological alteration of the 5-HT_2A signaling. After a brief presentation of the pharmacological properties of the 5-HT_2A-Rs, this review illustrates how these receptors may directly or indirectly control neuronal excitability in most networks involved in depression and epilepsy through interactions with the monoaminergic, GABAergic and glutamatergic neurotransmissions. It also synthetizes the preclinical and clinical evidence demonstrating the role of these receptors in antidepressant and antiepileptic responses.

Converging translational evidence for the involvement of the serotonin 2A receptor gene in major depressive disorder

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" (p<0.01). 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.

Are there depression and anxiety genetic markers and mutations? A systematic review

BACKGROUND

Genetic factors may encourage or even cause the occurrence of mood disorders such as anxiety and/or depression. However, despite the significant amount of work and sophisticated technology is not fully elucidated which genes or regions of nuclear or mitochondrial DNA, or which types of genetic changes, alone or in combination, can represent reliable genetic markers of anxiety and/or depression.

OBJECTIVE

To identify whether there are genetic changes that can cause depression or anxiety and if there are genetic markers that can be used to detect these changes.

METHODS

A systematic review of 01.01.2004 to 03.28.2014 was held by VHL (Virtual Health Library). The search was performed with the descriptors ׳׳anxiety׳׳, ׳׳depression׳׳, "mutation" and "genetic markers׳׳. The selected articles were indexed in MEDLINE. The information pertinent to the study was selected, categorized and analyzed. Of the 374 articles found, 29 met the eligibility criteria.

RESULTS

FMR1 gene polymorphisms, dopaminergic (DAT, DRD, COMT), serotonin (5-HTTLPR, HTR1A, HTR2A), interleukins, MCR1, HCN (potassium channel), neurorregulinas, GABAergic (GABA, GAD, DBI) DBI, GABA (Gabra) receptors and GAD genes (GAD1, GAD2) appear to contribute to generate condition of depression or anxiety like. Mutations in mitochondrial DNA in 124pb allele of D2S2944 in ofil 1 and 2 loci of chromosomes 4 and 7, respectively, and the chromosomes 8p, 17p and 15q appear to be associated with the origin of depression or anxiety.

CONCLUSION

Some studies show only associations with one of the disorders, mainly anxiety. Few have shown association with both simultaneously. Other studies showed specific association of gender, or even specific ethnic groups. It was noticed, controversies over certain markers. Interesting results were observed in combination of changes, especially in cases of SNPs, indicating that perhaps this is the most appropriate way to find reliable markers.

Influence of 5-HTR2A genetic polymorphisms on the efficacy of antidepressants in the treatment of major depressive disorder: a meta-analysis

OBJECTIVE

The aim of the current meta-analysis was to assess the influence of common genetic polymorphisms in the 5-HTR2A gene on the efficacy of antidepressants in the treatment of major depressive disorder (MDD).

METHOD

MEDLINE (1966-2013), Cochrane Library Database (Issue 12, 2013), EMBASE (1980-2013), CINAHL (1982-2013), Web of Science (1945-2013) and Chinese Biomedical Database (CBM) (1982-2013) were searched without language restrictions. Meta-analysis was performed using the STATA statistical software. We calculated the odds ratio (OR) and its 95% confidence interval (95% CI) to estimate the efficacy of antidepressants in the treatment of MDD.

RESULTS

Eleven studies with a total of 1775 MDD patients met the inclusion criteria of this meta-analysis. Three common polymorphisms in the 5-HTR2A gene were assessed, including rs6311 C>T, rs7997012 G>A, and rs6313 T>C. Our findings suggested that the 5-HTR2A rs6313 T>C polymorphism was significantly correlated with a higher response rate to antidepressants in MDD patients (allele model: OR=1.33, 95% CI=1.05-1.68, P=0.020; dominant model: OR=1.62, 95% CI=1.21-2.18, P=0.001; homozygous model: OR=1.85, 95% CI=1.18-2.90, P=0.008). The rs7997012 G>A polymorphism was also associated with a higher response rate to antidepressants in MDD patients under the dominant model (OR=1.92, 95% CI=1.02-3.61, P=0.044). However, no significant correlation was found for the 5-HTR2A rs6311 C>T polymorphism under five genetic models (all P>0.05).

CONCLUSION

Our findings provide empirical evidence that the 5-HTR2A rs6313 T>C and rs7997012 G>A polymorphism may be correlated with the efficacy of antidepressants in the treatment of MDD.

Association of HTR2A T102C and A-1438G polymorphisms with susceptibility to major depressive disorder: a meta-analysis

Serotonin 2A receptor (HTR2A) gene was implicated to be associated with major depressive disorder (MDD) susceptibility due to its role of key neurotransmitter in many physiologic processes. A great number of related studies reported in different populations have emerged. The results of these studies, however, have been inconsistent and thereby definite conclusions are difficult to establish. With the cumulative data in recent years, it was necessary to carry out a comprehensive analysis of previous findings. Electronic databases were systematically searched for studies published before May 2013. Pooled odds ratios (OR) and 95 % confidence interval (CI) were estimated under three different genetic models. Subgroup and sensitivity analyses were also performed. A total of 21 studies, 3,299 patients and 4,092 controls, met the selection criteria. 15 studies included HTR2A T102C polymorphism (with a total of 2,409 patients and 3,130 controls), and 9 studies included HTR2A A-1438G polymorphism (with a total of 1,510 patients and 2,281 controls). Our results showed that no significant association of MDD susceptibility with T102C polymorphism was found in allelic analysis and genotypic analysis (For T vs. C: OR = 1.06, 95 % CI = 0.95-1.18, P = 0.307; For TT + TC vs. CC: OR = 1.07, 95 % CI = 0.90-1.28, P = 0.451; For TT vs. TC + CC: OR = 1.08, 95 % CI = 0.95-1.22, P = 0.235). With respect to A-1438G polymorphism, however, carriers with A allele tend to suffer from MDD (AA + AG vs. GG: OR = 1.20, 95 % CI = 1.02-1.43, P = 0.030). When stratified by race for T102C polymorphism and A-1438G polymorphism of the HTR2A, we found no significant association. In conclusions, our study suggests that the A allele of A-1438G polymorphism might play a role in susceptibility to MDD. On the contrary, T102C polymorphism does not seem to be capable of modifying MDD risk.

Association of the T102C polymorphism in the HTR2A gene with major depressive disorder, bipolar disorder, and schizophrenia

A number of studies have assessed a relationship between the T102C polymorphism in the HTR2A gene with an increased risk of major depressive disorder (MDD), bipolar disorder (BPD), and schizophrenia (SCZ). However, the results have been inconsistent. Hence, we performed this study to further evaluate potential associations between the T102C polymorphism and MDD, BPD, and SCZ. The strength of separate associations between the T102C polymorphism and the risk of MDD, BPD, or SCZ was measured by ORs and 95% confidence intervals (CIs) in six genetic models. Cochran's chi-square-based Q-statistic and I(2) were used to evaluate the heterogeneity between studies. The funnel plot and the Egger's test were used to assess the publication bias. Cumulative meta-analysis was also performed to evaluate the trend in OR over time. No significant association was found in the overall analysis of MDD, BPD and SCZ with a sample size of 17,178 cases and 20,855 control subjects. In a further analysis by ethnicity, the OR and 95% CIs indicated the T102C polymorphism was not associated with MDD, BPD, or SCZ in Caucasian, Asian or Chinese populations. No publication bias was observed in the meta-analysis, and the cumulative analyses indicated the robust stability of the results. Thus, the results of our study indicate that the T102C polymorphism is not associates with increased susceptibility to MDD, BPD, and SCZ.

The serotonin 1A receptor gene confer susceptibility to mood disorders: results from an extended meta-analysis of patients with major depression and bipolar disorder

The serotonin 1A receptor gene (HTR1A) has been associated with mood disorders (MDs), including major depressive disorder (MDD) and bipolar disorder (BP). Therefore, we conducted a systematic review and meta-analysis between rs6295 (C-1019G) as well as rs878567 in HTR1A and MDs. Searching PubMed through May 2012, 15 studies, including our own, previously unpublished association study (135 MDD patients and 107 healthy controls), met inclusion criteria for the meta-analysis of rs6295 (4,297 MDs patients and 5,435 controls). Five association studies met criteria for the meta-analysis of rs878567 (2041MDs patients and 2,734 controls). rs6295 was associated with combined MDs (P allele model = 0.007 and P recessive model = 0.01). When divided by diagnostic subgroup (MDD = 3,119 patients and 4,380 controls or BP = 1,170 patients and 2,252 controls), rs6295 was associated with each MDs separately (MDD: P allele model = 0.006, P recessive model = 0.01; BP: P dominant model = 0.003). Likewise, rs878567 was associated with combined MDs (2,041 patients and 2,734 controls (P allele model = 0.0002, P dominant model = 0.0008, and P recessive model = 0.01). When divided by diagnostic subgroup (MDD = 1,013 patients and 1,728 controls or BP = 1,051 patients and 2,099 controls), rs878567 was associated with MDD (P allele model = 0.0007 and P dominant model = 0.01), while only one BP study had such data, precluding a meta-analysis. All of these significances survived correction for multiple comparisons. Results from this expanded meta-analysis, which included our own new study, suggest that rs6295 (C-1019G) and rs878567 in HTR1A are related to the pathophysiology of MDs, with overlap between MDD and BP. Findings provide additional clues to the underlying biology and treatment targets in MDs.

HTR2A-1438A/G polymorphism influences the risk of schizophrenia but not bipolar disorder or major depressive disorder: a meta-analysis

The incidence of psychiatric disorders has been shown to have a strong genetic component, and we conducted this study to investigate whether the -1438A/G polymorphism of the HTR2A gene was associated with susceptibility to schizophrenia (SZ), bipolar disorder (BD), and major depressive disorder (MDD). Pooled odd ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using data obtained from a total 27 studies that investigated an association between the HTR2A -1438A/G polymorphism and SZ (15), BD (7), and MDD (4). We failed to observe an association between the HTR2A -1438A/G polymorphism and BD and MDD, and we found contrary results with regard to SZ. Our results showed that the -1438A/G polymorphism was a risk factor for SZ, especially in Caucasians (allele model: OR, 1.12; 95% CI, 1.05-1.20; I(2) = 17.3%; dominant model: OR, 1.14; 95% CI, 1.03-1.27; I(2) = 15.3%; recessive model: OR, 1.20; 95% CI, 1.06-1.37; I(2) = 0.0%; codominant model 1: OR, 1.16; 95% CI, 1.01-1.32; I(2) = 0.0%). We found that the association of the HTR2A -1438A/G polymorphism with SZ depends on the ethnic origin of the study population, and this genetic variant does not modify the susceptibility to BD or MDD. © 2013 Wiley Periodicals, Inc.

Meta-analysis of genetic association studies on bipolar disorder

Numerous candidate gene association studies of bipolar disorder (BP) have been carried out, but the results have been inconsistent. Individual studies are typically underpowered to detect associations with genes of small effect sizes. We conducted a meta-analysis of published candidate gene studies to evaluate the cumulative evidence. We systematically searched for all published candidate gene association studies of BP. We then carried out a random-effects meta-analysis on all polymorphisms that were reported on by three or more case-control studies. The results from meta-analyses of these genes were compared with the findings from a recent mega-analysis of eleven genome-wide association studies (GWAS) in BP performed by the Psychiatric GWAS Consortium (PGC). A total of 487 articles were included in our review. Among these, 33 polymorphisms in 18 genes were reported on by three or more case-control studies and included in the random-effects meta-analysis. Polymorphisms in BDNF, DRD4, DAOA, and TPH1, were found to be nominally significant with a P-value < 0.05. However, none of the findings were significant after correction for multiple testing. Moreover, none of these polymorphisms were nominally significant in the PGC-BP GWAS. A number of plausible candidate genes have been previously associated with BP. However, the lack of robust findings in our review of these candidate genes highlights the need for more atheoretical approaches to study the genetics of BP afforded by GWAS. The results of this meta-analysis and from other on-going genomic experiments in BP are available online at Metamoodics (http://metamoodics.igm.jhmi.edu).

No Association Between GRM3 and Japanese Methamphetamine-Induced Psychosis

Several investigations have suggested that abnormalities in glutamate neural transmission play a role in the pathophysiology of psychiatric disorders, including schizophrenia. The metabotropic glutamate 3 receptor (mGluR3) gene was reported to be associated with schizophrenia, and paranoid type schizophrenia has symptoms that are similar to those of methamphetamine-induced psychosis. This suggests that mGluR3 gene (GRM3) is a good candidate gene for the pathogenesis of methamphetamine-induced psychosis. To evaluate the association between GRM3 and methamphetamine-induced psychosis, we conducted a case-control study of Japanese samples (181 methamphetamine-induced psychosis and 232 controls).

Possible association between ubiquitin-specific peptidase 46 gene and major depressive disorders in the Japanese population

BACKGROUND

Several investigations have reported that abnormalities in circadian rhythms might be related to the pathophysiology of major depressive disorder (MDD) and the therapeutic response to selective serotonin reuptake inhibitors (SSRIs). Recently, ubiquitin-specific peptidase 46 (USP46), a new molecule related to the circadian clock system, has been described. We conducted a case control study between seven tagging SNPs (rs10517263, rs17675844, rs6554557, rs12646800, rs2244291, rs10034164, rs346005) in the USP46 gene, MDD, and the SSRI therapeutic response in MDD in the Japanese population.

METHOD

We recruited 432 MDD patients (202 males and 230 females) and 792 healthy controls (319 males and 473 females). Two hundred sixty-one of 432 MDD patients were treated with SSRIs (fluvoxamine, sertraline or paroxetine).

RESULT

We detected an association between the USP46 gene and MDD in a haplotype analysis (rs2244291-rs10034164-rs346005 and rs12646800-rs2244291-rs10034164-rs346005). However, we did not find any association between the USP46 gene and SSRI response or remission in MDD in the Japanese population.

LIMITATIONS

A replication study using larger samples may be required for conclusive results, since our sample size was small.

CONCLUSIONS

Our results suggest that the USP46 gene might play a role in the pathophysiology of MDD in the Japanese population.

Lithium differentially affects clock gene expression in serum-shocked NIH-3T3 cells

Bipolar disorder has been associated with disturbances in circadian rhythms. Lithium is frequently used in the long-term treatment of bipolar disorder, and has been shown to prolong such rhythms in animals and humans. To examine whether lithium affects the expression of genes regulating the circadian clock, cultured NIH-3T3 cells were synchronized by serum-shocking, and the relative expression of the clock genes Period1 (Per1), Period2 (Per2), Period3 (Per3), Cryptochrome1 (Cry1), Cryptochrome2 (Cry2), Brain and muscle aryl hydrocarbon nuclear translocator-like 1 (Bmal1), Circadian locomotor output cycles kaput (Clock), Rev-Erb-α (Nr1d1), RAR-related orphan receptor α (Ror-α), Glycogen synthase kinase-3β (Gsk-3β), Casein kinase 1-ε (CK1-ε; Csnk1ε), E4 binding protein 4 (E4BP4; Nfil-3) and albumin D-binding protein (Dbp) was examined for three consecutive days in the presence of lithium (20 mM) or vehicle (20 mM NaCl). We found that lithium significantly increased the expression of Per2 and Cry1, whereas Per3, Cry2, Bmal1, E4BP4 and Rev-Erb-α expression was reduced. We also found that lithium prolonged the period of Per2. Taken together, these effects on clock gene expression may be relevant for the effects of lithium on biological rhythms and could also give new leads to further explore its mood-stabilizing actions in the treatment of bipolar disorder.

SIRT1 gene is associated with major depressive disorder in the Japanese population

BACKGROUND

Many studies including our previous ones as to PROKR2 and CLOCK have suggested that circadian genes may be involved in the mechanisms of mood disorders and their treatment responses. Also several recent investigations have reported that SIRT1 plays an important role in the circadian system as conventional circadian clock genes, and also have some relation to dopaminergic metabolism. So we considered the SIRT1 gene to be a good candidate gene for the pathophysiology for MDD and SSRI responses in MDD, and conducted a case-control study using four tagging SNPs (450 MDD patients, including 261 patients treated by SSRIs and 766 controls).

METHOD

The MDD patients in this study had scores of 12 or higher on the 17 items of the Structured Interview Guide for Hamilton Rating Scale for Depression (SIGH-D). We defined a clinical response as a decrease of more than 50% in baseline SIGH-D within 8 weeks, and clinical remission as an SIGH-D score of less than 7 at 8 weeks. Marker-trait association analysis was used to evaluate allele and genotype association with the chi-square test, and haplotype association analysis was evaluated with a likelihood ratio test.

RESULT

We found an association between rs10997875 in SIRT1 gene and MDD in the allele/genotype analysis. In addition, this significance of these associations survived Bonferroni correction. However, we did not find any association between SIRT1 gene and SSRI therapeutic response in MDD in the allele/genotype analysis or haplotype analysis.

LIMITATIONS

A replication study using larger samples may be required for conclusive results, since our sample size was small.

CONCLUSIONS

Our results suggest that rs10997875 in SIRT1 gene may play a role in the pathophysiology of MDD in the Japanese population.

PROKR2 is associated with methamphetamine dependence in the Japanese population

BACKGROUND

Many patients with drug addiction are reported to have comorbid mood disorders. One of the suggested pathophysiological mechanisms for mood disorders is disruption of circadian rhythms. Several animal studies have shown that methamphetamine altered the expression of circadian clock molecules in the brain. Therefore, it is possible that mood disorders and drug addiction have common susceptibility genes. Recently, we reported that the prokineticin 2 receptor gene (PROKR2) was associated with mood disorders including major depressive disorder and bipolar disorder in the Japanese population. In the present study, therefore, we conducted an association analysis of tagging SNPs in PROKR2 with Japanese methamphetamine dependence patients.

METHODS

Using five tagging SNPs in PROKR2, we conducted a genetic association analysis of case-control samples (199 methamphetamine dependence patients and 337 healthy controls). The age and sex of the control subjects did not differ from those of the methamphetamine dependence patients.

RESULTS

We detected a significant association between PROKR2 and methamphetamine dependence patients in allele/genotype-wise and haplotype-wise analysis.

CONCLUSION

Our results suggest that PROKR2 may play a role in the pathophysiology of methamphetamine dependence in the Japanese population. However, because we did not perform a mutation scan of PROKR2, a replication study using a larger sample may be required for conclusive results.

Pharmacogenetic study of serotonin 6 receptor gene with antidepressant response in major depressive disorder in the Japanese population

OBJECTIVE

Several investigations have suggested that alterations in serotonin 6 (5-HT6) receptors might be associated with the pathophysiology of major depressive disorder (MDD), and that 5-HT6 receptors might be a therapeutic target for serotonin selective reuptake inhibitor (SSRI) in MDD. To evaluate the association between HTR6 and the efficacy of SSRI treatment in Japanese MDD patients, we conducted a case-control study in a Japanese population sample.

METHODS

We selected five tagging SNPs (rs6693503, rs1805054, rs4912138, rs3790757 and rs9659997), and performed an association analysis of HTR6 and the efficacy of SSRI treatment in 260 MDD patients.

RESULTS

We did not detect an association between tagging SNPs in HTR6 and the therapeutic response to SSRI in MDD in allele/genotype or haplotype analysis.

CONCLUSIONS

HTR6 may not play an important role in the pathophysiology of SSRI response in the Japanese population. Because our sample was relatively small, statistical errors were possible in the results of our association analyses. To overcome these limitations, a replication study using a larger sample may be required for conclusive results.

Association analysis of SIGMAR1 with major depressive disorder and SSRI response

BACKGROUND

Several investigations have suggested the possible involvement of sigma 1 non-opioid intracellular receptor 1 (sigma 1 receptor) in the pathophysiology of major depressive disorder (MDD). Sigma 1 receptors are also one of the major pharmacological therapeutic targets of selective serotonin reuptake inhibitors (SSRIs). To evaluate the association of sigma 1 receptor gene (SIGMAR1) and MDD and SSRIs therapeutic response in MDD, we conducted a case-control study of Japanese samples (466 MDD patients, 516 controls and 208 MDD patients treated by fluvoxamine or sertraline).

METHOD

We defined a clinical response as a decrease of more than 50% in baseline the Structured Interview Guide for Hamilton Rating Scale for Depression (SIGH-D) within 8 weeks, and clinical remission as an SIGH-D score of less than 7 at 8 weeks. Therefore, we selected rs1800866 in SIGMAR1 for the following association analysis.

RESULTS

In the logistic regression analysis, we detected an association of the phenotypes (MDD or controls) with rs1800866 genotype. However, we did not detect an association between rs1800866 and SSRI therapeutic response in Japanese MDD. In addition, remission with SSRI was not associated with rs1800866. Also, we did not detect a novel polymorphism in SIGMAR1 when we performed a mutation search using MDD treated by SSRIs samples.

CONCLUSION

Our results suggest that rs1800866 in SIGMAR1 may play a role in the pathophysiology of MDD in the Japanese population. Also, SIGMAR1 does not play a role in the therapeutic response to SSRI in Japanese MDD patients. However, because our sample was small, a replication study using another population and larger sample will be required for conclusive results.

Association analysis of GRM2 and HTR2A with methamphetamine-induced psychosis and schizophrenia in the Japanese population

BACKGROUND

Abnormalities in glutaminergic neural transmission have been suggested to be involved in the pathogenesis of schizophrenia. A recent study reported that alterations in the 5-HT2A-mGluR2 complex may be involved in neural transmission in the schizophrenic cortex. In addition, methamphetamine-induced psychosis is thought to be similar to schizophrenia. Therefore, we conducted a case-control study with Japanese samples (738 schizophrenia patients, 196 methamphetamine-induced psychosis patients, and 802 controls) to evaluate the association and interaction between GRM2, HTR2A and schizophrenia.

METHODS

We selected three 'tagging SNPs' in GRM2, and two biologically functional SNPs in HTR2A (T102C and A1438G), for the association analysis.

RESULTS

We detected a significant association between methamphetamine-induced psychosis and GRM2 in a haplotype-wise analysis, but not HTR2A. We did not detect an association between GRM2 or HTR2A and schizophrenia. In addition, no interactions of GRM2 and HTR2A were found in methamphetamine-induced psychosis or schizophrenia. We did not detect any novel polymorphisms in GRM2 when we performed a mutation search using methamphetamine-induced psychosis samples.

CONCLUSION

Our results suggested that GRM2 may play a role in the pathophysiology of methamphetamine-induced psychosis but not schizophrenia in the Japanese population. A replication study using larger samples or samples of other populations will be required for conclusive results.

Lack of association between MAGEL2 and schizophrenia and mood disorders in the Japanese population

Several investigations have reported that abnormalities in circadian rhythms might be related with the pathophysiology of psychiatric disorders, since many psychiatric patients have insomnia and sleep-awake disturbance. A recent animal study reported that Magel2, which encodes a member of the MAGE/necdin family of proteins, might be associated in the pathophysiology of psychiatric disorders. Magel2 gene knockout mice showed altered concentrations of both dopamine and serotonin in several parts of the brain compared with controls. In addition, the authors of that study detected a bilateral reduction in cortical volume in distinct regions of the Magel2 gene knockout mice brain, including focused regions in the parieto-temporal lobe of the cerebral cortex, the amygdala, the hippocampus, and the nucleus accumbens. These mice were also found to have hypoactivity and abnormalities in circadian rhythms. From this evidence, we considered Magel2 gene (MAGEL2) to be a good candidate gene for the pathophysiology of schizophrenia and mood disorder, and we conducted a case-control study among Japanese (731 schizophrenia patients, 465 MDD patients, 156 BP patients and 758 controls) using three tagging SNPs in MAGEL2 (rs850815, rs8920 and rs4480754), selected using the HapMap database. We did not find any association between MAGEL2 and schizophrenia, BP or MDD in allele/genotype-wise analysis or haplotype-wise analysis. Our results suggest that MAGEL2 may not play a role in the pathophysiology of schizophrenia and mood disorders in the Japanese population. A replication study using larger samples may be required for conclusive results, since our sample size was small and our study analyzed only three SNPs in MAGEL2.

Differential association of circadian genes with mood disorders: CRY1 and NPAS2 are associated with unipolar major depression and CLOCK and VIP with bipolar disorder

Disruptions in circadian rhythms have been described in mood disorders (MD), but the involvement of genetic variation in genes pertaining to the molecular circadian machinery in the susceptibility to MD has not been conclusively determined. We examined 209 single-nucleotide polymorphisms (SNPs) covering 19 circadian genes (ADCYAP1, ARNTL, ARNTL2, BHLHB2, BHLHB3, CLOCK, CRY1, CRY2, CSNK1E, DBP, NPAS2, NR1D1, PER1, PER2, PER3, RORA, TIMELESS, VIP, and VIPR2) in a sample of 534 MD patients (335 with unipolar major mood depression (MDD) and 199 with bipolar disorder (BD)) and 440 community-based screened controls. Nominally, statistically significant associations were found in 15 circadian genes. The gene-wide test, corrected for the number of SNPs analyzed in each gene, identified significant associations in CRY1 (rs2287161), NPAS2 (rs11123857), and VIPR2 (rs885861) genes with the combined MD sample. In the MDD subsample, the same SNPs in CRY1 and NPAS2 of the combined sample remained associated, whereas in the BD subsample CLOCK (rs10462028) and VIP (rs17083008) were specifically associated. The association with an SNP located 3' near CRY1 gene in MDD remained statistically significant after permutation correction at experiment level (p=0.007). Significant additive effects were found between the SNPs that were statistically significant at the gene-wide level. We also found evidence of associations between two-marker haplotypes in CRY1 and NPAS2 genes and MD. Our data support the contribution of the circadian system to the genetic susceptibility to MD and suggest that different circadian genes may have specific effects on MD polarity.

Serotonin 6 receptor gene and mood disorders: case-control study and meta-analysis

Several evidence suggests that alterations in serotonin 6 (5-HT6) receptors might be associated with the pathophysiology of mood disorders. Therefore, to evaluate the association between HTR6 and BP and MDD, we conducted a case-control study of Japanese population samples (1007 BP patients, 447 MDD patients and 1753 controls) with five tagging SNPs, including rs1805054 (C267T), in HTR6. In addition, we conducted a meta-analysis of rs1805054, which has been examined in other studies. We selected five tagging SNPs (rs6693503, rs1805054, rs4912138, rs3790757 and rs9659997). Moreover, three association studies for BP and four association studies for MDD, including this study, met our criteria for the meta-analysis of rs1805054. We did not detect an association between tagging SNPs in HTR6 and BP and MDD in the allele/genotype, haplotype analysis or meta-analysis. In conclusion, we found no association involving polymorphism and mood disorder in the Japanese population. However, because changes in expression level or signal transduction of this receptor may be involved in the pathology of these diseases, it will be necessary to conduct the further study about the relationship between this receptor and mood disorders in the future.

HTR2A is associated with SSRI response in major depressive disorder in a Japanese cohort

Several recent investigations reported that the serotonin 2A receptor gene (HTR2A) was associated with selective serotonin reuptake inhibitors (SSRIs) in major depressive disorder. There have also been two reported association analyses of HTR2A with SSRI response in Japanese MDD patients, but the results were rather inconsistent and both studies had the problem of small sample sizes. Therefore, we conducted a replication association study using a sample larger than those in the two original Japanese studies (265 MDD patients), and found that four SNPs, two functional SNPs (-A1438G: rs6311 and T102C: rs6313) and two SNPs (rs7997012 and rs1928040) in HTR2A, were associated with the therapeutic response to SSRIs. HTR2A was associated with the therapeutic response SSRIs in Japanese MDD patients in a haplotype-wise analysis (P(all markers) = 0.0136), and a significant association between rs1928040 in HTR2A and SSRI response was detected in MDD (P(allele-wise analysis) = 0.0252). However, this significance disappeared after Bonferroni correction (P(allele-wise analysis) = 0.101). In conclusion, we suggest that HTR2A may play an important role in the pathophysiology of the therapeutic response to SSRIs in Japanese MDD patients. However, it will be important to replicate and confirm these findings in other independent studies using large samples.

Serotonin 1A receptor gene and major depressive disorder: an association study and meta-analysis

Several genetic studies have shown an association between the 5-HT1A receptor gene (HTR1A) and major depressive disorder (MDD); however, results have been rather inconsistent. Moreover, to our knowledge, no association study on HTR1A and MDD in the Japanese population has been reported. Therefore, to evaluate the association between HTR1A and MDD, we conducted a case-control study of Japanese population samples with two single-nucleotide polymorphisms (SNPs), including rs6295 (C-1019G) in HTR1A. In addition, we conducted a meta-analysis of rs6295, which has been examined in other papers. Using one functional SNP (rs6295) and one tagging SNP (rs878567) selected with the HapMap database, we conducted a genetic association analysis of case-control samples (331 patients with MDD and 804 controls) in the Japanese population. Seven population-based association studies, including this study, met our criteria for the meta-analysis of rs6295. We found an association between rs878567 and Japanese MDD patients in the allele-wise analysis, but the significance of this association did not remain after Bonferroni's correction. We also did not detect any association between HTR1A and MDD in the allele/genotype-wise or haplotype-wise analysis. On the other hand, we detected an association between rs6295 and MDD in the meta-analysis (P(Z)=0.0327). In an explorative analysis, rs6295 was associated with Asian MDD patients after correction for multiple testing (P(Z)=0.0176), but not with Caucasian MDD patients (P(Z)=0.138). Our results suggest that HTR1A may not have a role in the pathophysiology of Japanese MDD patients. On the other hand, according to the meta-analysis, HTR1A was associated with MDD patients, especially in the Asian population.