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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.

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.

Several investigations have reported that the translin-associated factor X gene (TSNAX)/disrupted-in-schizophrenia-1 gene (DISC1) was associated with major psychiatric disorders including schizophrenia, bipolar disorder (BP), and major depressive disorder (MDD). TSNAX is located immediately upstream of DISC1, and has been shown to undergo intergenic splicing with DISC1. It thus may also be influenced by translocation. To our knowledge, there are no reported gene-based association analyses between TSNAX and mood disorders in the Japanese population. We conducted a case-control study of Japanese samples (158 bipolar patients, 314 major depressive disorder patients, and 811 controls) with three tagging SNPs in TSNAX, selected using HapMap database. In addition, we performed an association analysis between TSNAX and the efficacy of fluvoxamine treatment in 120 Japanese patients with MDD. 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. We found an association between rs766288 in TSNAX and female MDD in the allele/genotype analysis. However, we did not find any association between TSNAX and BP or the fluvoxamine therapeutic response in MDD in the allele/genotype analysis or haplotype analysis. Our results suggest that rs766288 in TSNAX may play a role in the pathophysiology of female MDD in the Japanese population. A replication study using larger samples may be required for conclusive results, since our sample size was small.

The neuregulin 1 gene (NRG1) has been identified as a candidate gene for schizophrenia in a linkage study in the Icelandic population. Recent evidence also suggested that it might be related to the neurodevelopmental hypothesis and glutamate hypothesis for schizophrenia. Because the symptomatology of methamphetamine (METH) use disorder with accompanying psychosis is similar to that of patients with schizophrenia, NRG1 is an appropriate candidate gene for METH-induced psychosis. We conducted a case-control association study between NRG1 and METH-induced psychosis in a Japanese population (184 subjects with METH-induced psychosis and 534 controls). Written informed consent was obtained from each subject. We selected four SNPs (SNP8NRG221533, SNP8NRG241930, SNP8NRG243177, and rs3924999) in NRG1 from previous reports. No significant association was found between NRG1 and METH-induced psychosis in the allele/genotype-wise or haplotype-wise analyses. In conclusion, NRG1 might not contribute to the risk of METH-induced psychosis in the Japanese population.

Recently the clock genes have been reported to play some roles in neural transmitter systems, including the dopamine system, as well as to regulate circadian rhythms. Abnormalities in both of these mechanisms are thought to be involved in the pathophysiology of major mental illness such as schizophrenia and mood disorders including bipolar disorder (BP) and major depressive disorder (MDD). Recent genetic studies have reported that CLOCK, one of the clock genes, is associated with these psychiatric disorders. Therefore, we investigated the association between the six tagging SNPs in CLOCK and the risk of these psychiatric disorders in Japanese patients diagnosed with schizophrenia (733 patients), BP (149) and MDD (324), plus 795 Japanese controls. Only one association, with schizophrenia in females, was detected in the haplotype analysis (P = 0.0362). However, this significance did not remain after Bonferroni correction (P = 0.0724). No significant association was found with BP and MDD. In conclusion, we suggest that CLOCK may not play a major role in the pathophysiology of Japanese schizophrenia, BP and MDD patients. However, it will be important to replicate and confirm these findings in other independent studies using large samples.

Background: A recent study reported an association between rs2234693, which influences enhancer activity levels in estrogen receptor alpha gene (ESR1), and schizophrenia. This study reported that schizophrenic patients with the CC genotype have significantly lower ESR1 mRNA levels in the prefrontal cortex than patients with other genotypes. The symptoms of methamphetamine induced psychosis are similar to those of paranoid type schizophrenia. Therefore, we conducted an association analysis of rs2234693 with Japanese methamphetamine induced psychosis patients., Method: Using rs2234693, we conducted a genetic association analysis of case-control samples (197 methamphetamine induced psychosis patients and 197 healthy controls). The age and sex of the control subjects did not differ from those of the methamphetamine induced psychosis patients., Results: We detected a significant association between ESR1 and methamphetamine induced psychosis patients in allele/genotype-wise analysis. For further interpretation of these associations, we performed single marker analysis of subjects divided by sex. Rs2234693 was associated with male methamphetamine induced psychosis., Discussion: Our results suggest that rs2234693 in ESR1 may play a role in the pathophysiology of Japanese methamphetamine induced psychosis patients.

Background: Several lines of evidence implicate abnormalities in glutamate neural transmission in the pathophysiology of mood disorders, including major depressive disorder (MDD) and bipolar disorder (BP). Preclinical antidepressant effects were also reported for group II metabotropic glutamate receptor (Group II mGluRs) antagonists show dose-dependent antidepressant-like effects in murine models of depression. Also, it has been suggested that abnormalities in the hypothalamic-pituitary-adrenal axis and serotonergic neural transmission are important mechanisms in the pathophysiology of mood disorders. Group II mGluRs play an important role in regulating the function of these mechanisms. From these results, it has been suggested that abnormalities in Group II mGluRs might be involved in the pathophysiology of mood disorders, including MDD) and BP, and may influence the clinical response to treatment with SSRIs in MDD. Therefore, we studied the association between Group II mGluR genes (GRM2 and GRM3) and mood disorders and the efficacy of fluvoxamine treatment in Japanese MDD patients., Materials and Methods: Using three tagging SNPs in GRM2 and an SNP (rs6465084) reported functional variant in GRM3, we conducted a genetic association analysis of case-control samples (325 MDD patients, 155 BP patients and 802 controls) in the Japanese population. In addition, we performed an association analysis of GRM2 and GRM3 and the efficacy of fluvoxamine treatment in 117 Japanese patients with MDD. 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., Results: We found an association between rs6465084 in GRM3 and MDD in the allele-wise analysis after Bonferroni's correction (P-value=0.0371). However, we did not find any association between GRM3 and BP or the fluvoxamine therapeutic response in MDD in the allele/genotype-wise analysis. We also did not detect any association between GRM2 and MDD, BP or the fluvoxamine therapeutic response in MDD in the allele/genotype-wise or haplotype-wise analysis., Discussion: We detected an association between only one marker (rs6465084) in GRM3 and Japanese MDD patients. However, because we did not perform an association analysis based on LD and a mutation scan of GRM3, a replication study using a larger sample and based on LD may be required for conclusive results.

Because several investigations, including genetic studies, have reported associations between serotonin (5-HT) 2A receptor gene and mood disorders, 5-HT 2A receptor gene (HTR2A) is a good candidate gene for the pathophysiology of mood disorders such as major depressive disorder (MDD) and bipolar disorder (BP). Using two functional SNPs (T102C and -A1438G) and two SNPs (rs7997012 and rs1928040) in HTR2A, which reported an association with therapeutic response to the SSRI, we conducted a genetic association analysis of case-control samples (325 MDD patients, 155 BP patients and 802 controls) in the Japanese population. We did not detect significant an association of HTR2A with MDD and BP in allele/genotype-wise or haplotype-wise analysis. In this study, we could detect no evidence of genetic association between 4 markers near HTR2A and mood disorders in the Japanese population, but sample sizes, especially BP, were probably too small to allow a meaningful test.

The neuronal nitric oxide synthase gene (NOS1) is located on 12q24, in a susceptibility region for schizophrenia, and produces nitric oxide (NO) in the brain. NO plays a role in neurotransmitter release and is the second messenger of the N-methyl-D-aspartate (NMDA) receptor. Furthermore, it is connected to the dopaminergic and serotonergic neural transmission systems. Therefore, abnormalities in the NO pathway are thought to be involved in the pathophysiology of schizophrenia. Several genetic studies showed an association of NOS1 with schizophrenia. However, results of replication studies have been inconsistent. Therefore, we conducted a replication study of NOS1 with schizophrenia in a Japanese sample. We selected seven SNPs (rs41279104, rs3782221, rs3782219, rs561712, rs3782206, rs2682826, and rs6490121) in NOS1 that were positively associated with schizophrenia in previous studies. Two SNPs showed an association with Japanese schizophrenic patients (542 cases and 519 controls, rs3782219: P allele = 0.0291 and rs3782206: P allele = 0.0124, P genotype = 0.0490), and almost these significances remained with an increased sample size (1154 cases and 1260 controls, rs3782219: P allele = 0.0197 and rs3782206: P allele = 0.0480). However, these associations also might have resulted from type I error on account of multiple testing (rs3782219: P allele = 0.133 and rs3782206: P allele = 0.168). In conclusion, we could not replicate the association between seven SNPs in NOS1 and schizophrenia found in several earlier studies, using larger Japanese schizophrenia and control samples.

Recent studies have shown that selective serotonin reuptake inhibitors (SSRIs) have circadian properties, suggesting that the antidepressive action of SSRIs may also be attributable to circadian mechanisms. Another study reported an association between clock gene (CLOCK) and improvements in insomnia symptoms from SSRIs treatment. Therefore, we examined the association between CLOCK and the efficacy of fluvoxamine treatment in 121 patients with Japanese major depressive disorder (MDD). 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 therapeutic response as a decrease of more than a 50% in baseline SIGH-D within 8 weeks, and clinical remission as a SIGH-D score of less than seven at 8 weeks. We selected three tagging SNPs in CLOCK for the subsequent statistical association analysis. We detected a significant association between rs3736544, a synonymous polymorphism in exon 20, and the fluvoxamine therapeutic response in MDD in the allele/genotype-wise analyses. In addition, remission with fluvoxamine was also significantly associated with rs3736544. These associations remained significant after Bonferroni correction. Moreover, haplotype analysis findings supported these significant associations, which appeared to be due mainly to rs3736544, in the fluvoxamine therapeutic remission. Our results indicate that CLOCK genotype may be a predictor of fluvoxamine treatment response in Japanese MDD. However, our sample size was small, and a replication study using larger samples may be required for conclusive results.

Several investigations have suggested that disruption of circadian rhythms may provide the foundation for the development of mood disorders such as bipolar disorder (BP) and major depressive disorder (MDD). Recent animal studies reported that prokineticin 2 or prokineticin 2 receptor gene deficient mice showed disruptions in circadian and homeostatic regulation of sleep. This evidence indicates that prokineticin 2 gene (PROK2) and prokineticin 2 receptor gene (PROKR2) are good candidate genes for the pathogenesis of mood disorders. To evaluate the association between PROK2, PROKR2, and mood disorders, we conducted a case-control study of Japanese samples (151 bipolar patients, 319 major depressive disorder patients, and 340 controls) with four and five tagging SNPs in PROK2 or PROKR2, respectively, selected by HapMap database. We detected a significant association between PROKR2 and major depressive disorder and bipolar disorder in the Japanese population. In conclusion, our findings suggest that PROKR2 may play a role in the pathophysiology of mood disorders in the Japanese population. However, because our samples were small, it will be important to replicate and confirm these findings in other independent studies using larger samples.

The mesolimbic system is thought to be involved in the reinforcing action of many addictive drugs and the release of dopamine modulated by neuronal nicotine cholinergic receptors (nAChRs). Several investigations suggested that nAChRs on dopaminergic terminals play an important role in the development of some long-lasting adaptations associated with drug abuse. A majority of high-affinity nicotine binding sites in the brain have been showed in heteropentameric alpha4 (alpha4) and beta2 subunit (beta2) of nAChRs. Therefore, we conducted a genetic association analysis of the alpha4 gene (CHRNA4) and beta2 gene (CHRNB2) with methamphetamine (METH)-use disorder (191 cases and 753 controls). We first evaluated the linkage disequilibrium (LD) structure of these genes and selected 7 and 5 tagging SNPs (tag SNPs) on CHRNA4 and CHRNB2, respectively. Some tag SNPs were significantly associated with total METH-use disorder and METH-induced psychosis; however, these associations were no longer statistically significant after Bonferroni's correction for multiple testing. In conclusion, our results suggest that neither CHRNA4 nor CHRNB2 plays a major role in Japanese METH-use disorder.

Abnormal intracellular signaling molecules in dopamine signal transduction are thought to be associated with the pathophysiology of methamphetamine (METH)-use disorder. A recent study reported that a new intracellular protein, prostate apoptosis response 4 (Par-4), plays a critical role in dopamine 2 receptor signaling. We therefore analyzed the association between the Par-4 gene (PAWR) and METH-use disorder in a Japanese population (191 patients with METH-use disorder and 466 healthy controls). Using the recommended "gene-based" association analysis, we selected five tagging SNPs in PAWR from the HapMap database. No significant allele/genotype-wise or haplotype-wise association was found between PAWR and METH-use disorder. These results suggest that PAWR does not play a major role in METH-use disorders in the Japanese population.

A recent study showed a significant association between schizophrenia in European samples and the glutamate cysteine ligase modifier (GCLM) subunit gene, which is the key glutathione (GSH)-synthesizing enzyme. Since the symptoms of methamphetamine (METH)-induced psychosis are similar to those of schizophrenia, the GCLM gene is thought to be a good candidate gene for METH-use disorder or related disorders. To evaluate the association between the GCLM gene and METH-use disorder and schizophrenia, we conducted a case-control study of Japanese subjects (METH-use disorder, 185 cases; schizophrenia, 742 cases; and controls, 819). Four SNPs (2 SNPs from an original report and JSNP database, and 2 "tagging SNPs" from HapMap database) in the GCLM gene were examined in this association analysis; one SNP showed an association with both METH-use disorder and METH-induced psychosis. After Bonferroni's correction for multiple testing, however, this significance disappeared. No significant association was found with schizophrenia. Our findings suggest that a common genetic variation in the GCLM gene might not contribute to the risk of METH-use disorder and schizophrenia in the Japanese population.

Several lines of evidence from animal and genetic analyses showed that the calcineurin A gamma subunit gene (PPP3CC) plays an important role in the pathogenesis of schizophrenia. Moreover, a recent large Japanese case-control study confirmed the genetic association of PPP3CC with schizophrenia. The symptoms of methamphetamine (MAP)-induced psychosis are similar to those of schizophrenia, suggesting that PPP3CC is an attractive candidate gene not only for schizophrenia, but also for METH-related disorders. In this study, we carried out a genetic association study of PPP3CC with MAP-use disorder in a Japanese population. We selected five haplotype-tagging SNPs from the aforementioned replication study and genotyped 393 samples (MAP abuse, 128; control, 265). We could not detect a significant association of all tagging SNPs with each condition. In conclusion, our data suggest that PPP3CC does not elevate the risk of MAP-use disorder in the Japanese population.