Cross-Disorder Analysis of Genic and Regulatory Copy Number Variations in Bipolar Disorder, Schizophrenia, and Autism Spectrum Disorder

BACKGROUND

We aimed to determine the similarities and differences in the roles of genic and regulatory copy number variations (CNVs) in bipolar disorder (BD), schizophrenia (SCZ), and autism spectrum disorder (ASD).

METHODS

Based on high-resolution CNV data from 8708 Japanese samples, we performed to our knowledge the largest cross-disorder analysis of genic and regulatory CNVs in BD, SCZ, and ASD.

RESULTS

In genic CNVs, we found an increased burden of smaller (<100 kb) exonic deletions in BD, which contrasted with the highest burden of larger (>500 kb) exonic CNVs in SCZ/ASD. Pathogenic CNVs linked to neurodevelopmental disorders were significantly associated with the risk for each disorder, but BD and SCZ/ASD differed in terms of the effect size (smaller in BD) and subtype distribution of CNVs linked to neurodevelopmental disorders. We identified 3 synaptic genes (DLG2, PCDH15, and ASTN2) as risk factors for BD. Whereas gene set analysis showed that BD-associated pathways were restricted to chromatin biology, SCZ and ASD involved more extensive and similar pathways. Nevertheless, a correlation analysis of gene set results indicated weak but significant pathway similarities between BD and SCZ or ASD (r = 0.25-0.31). In SCZ and ASD, but not BD, CNVs were significantly enriched in enhancers and promoters in brain tissue.

CONCLUSIONS

BD and SCZ/ASD differ in terms of CNV burden, characteristics of CNVs linked to neurodevelopmental disorders, and regulatory CNVs. On the other hand, they have shared molecular mechanisms, including chromatin biology. The BD risk genes identified here could provide insight into the pathogenesis of BD.

A preliminary study on predictors of treatment response to repetitive transcranial magnetic stimulation in patients with treatment-resistant depression in Japan

BACKGROUND

Brain imaging studies have reported that the effect of repetitive transcranial magnetic stimulation (rTMS) is associated with the activities of the dorsolateral prefrontal cortex (DLPFC) and ventral medial prefrontal cortex (VMPFC). However, few studies have been conducted in Japanese patients.

AIM

We aimed to identify brain regions associated with depressive symptom changes by measuring regional cerebral blood flow (rCBF) in the DLPFC and VMPFC before and after the high-frequency rTMS to the left DLPFC in Japanese patients with treatment-resistant depression.

METHOD

Fourteen patients participated in the rTMS study and were assessed with the 17-item Hamilton depression rating scale (HAM-D₁₇ ). Among them, 13 participants underwent magnetic resonance imaging scan of the brain using the arterial spin labeling method. The rCBF was calculated using the fine stereotactic region of interest template (FineSRT) program for automated analysis. We focused on eight regions reported in previous studies.

RESULTS

Depression severity significantly decreased after 2 week (HAM-D₁₇ :11.4 ± 2.8, P = 0.00027) and 4 week (HAM-D₁₇ : 11.0 ± 3.7, P = 0.0023) of rTMS treatment. There was no significant change in rCBF at each region in the pre-post design. However, there was a significantly negative correlation between baseline rCBF in the right DLPFC and the improvement in HAM-D₁₇ score (r = -0.559, P = 0.047).

CONCLUSION

We obtained supportive evidence for the effectiveness of rTMS to the prefrontal cortex in treatment-resistant depression, which may be associated with reduced rCBF of the right DLPFC before initiation of rTMS.

Association of Serotonin Transporter Gene (5-HTTLPR/rs25531) Polymorphism with Comorbidities of Panic Disorder

INTRODUCTION

Panic disorder (PD) has many comorbidities such as depression, bipolar disorder (BPD), and agoraphobia (AG). PD is a moderately heritable anxiety disorder whose pathogenesis is not well understood. Recently, a tri-allelic serotonin transporter (5-HTTLPR/rs25531) polymorphism was reported to be more sensitive to personality traits compared to the bi-allelic 5-HTTLPR polymorphism. We hypothesized that the 5-HTTLPR/rs25531 polymorphism may lead to a pathological anxious state depending on the presence or absence of a comorbidity in PD.

METHODS

In this study, we investigated the relationship between comorbidities in PD and tri-allelic 5-HTTLPR polymorphisms. A total of 515 patients with PD (148 males, 367 females) were genotyped, and the Revised NEO Personality Inventory as well as anxiety-related psychological tests were administered. Depression, BPD, and AG were diagnosed as comorbidities.

RESULTS

For the tri-allele 5-HTTLPR genotype, a significant interaction effect was found between openness to experience and comorbid depression. Examination of the interaction between AG and the tri-allelic 5-HTTLPR genotype revealed that L' allele carriers are associated with higher trait anxiety than the S'S' genotype group in PD without AG.

CONCLUSION

Some anxiety and personality traits can be characterized by the tri-allelic gene effect of 5-HTTLPR. These results suggest that tri-allelic 5-HTTLPR genotypes have genetic effects on the presence of comorbidities of PD.

Utility of VSRAD for diagnosing Alzheimer's disease in patients screened for dementia

Objective

To investigate the utility of the voxel-based specific regional analysis system for Alzheimer’s disease (VSRAD).

Methods

Clinical data from patients who underwent screening for dementia using VSRAD and the Japanese version of COGNISTAT, the Neurobehavioral Cognitive Status Examination, were retrospectively investigated to specify the domains of cognitive function that correlate with the statistical mean value of positive Z-scores in the target volume-of-interest (VOI). A receiver operating characteristic (ROC) curve was constructed to assess the mean value of positive Z-scores in discriminating patients with AD.

Results

A total of 72 patients were included (18 male and 54 female; 15 patients with AD). The mean value of positive Z-scores in the target VOI was significantly correlated with standardized COGNISTAT scores for Orientation and Memory in all patients (r = –0.35 and –0.38, respectively). ROC curve analysis revealed that a cut-off of 1.57 for mean value of positive Z-scores in the target VOI provided 69.4% accuracy in discriminating patients with AD, with a sensitivity of 0.80 and specificity of 0.67.

Conclusions

The results evinced the value of VSRAD in diagnosing AD. The degree of atrophy represented by the target VOI may reflect impairments in Orientation and Memory, which are early stage symptoms observed in AD.

Sensitivity to gene dosage and gene expression affects genes with copy number variants observed among neuropsychiatric diseases

BACKGROUND

Copy number variants (CNVs) have been reported to be associated with diseases, traits, and evolution. However, it is hard to determine which gene should have priority as a target for further functional experiments if a CNV is rare or a singleton. In this study, we attempted to overcome this issue by using two approaches: by assessing the influences of gene dosage sensitivity and gene expression sensitivity. Dosage sensitive genes derived from two-round whole-genome duplication in previous studies. In addition, we proposed a cross-sectional omics approach that utilizes open data from GTEx to assess the effect of whole-genome CNVs on gene expression.

METHODS

Affymetrix Genome-Wide SNP Array 6.0 was used to detect CNVs by PennCNV and CNV Workshop. After quality controls for population stratification, family relationship and CNV detection, 287 patients with narcolepsy, 133 patients with essential hypersomnia, 380 patients with panic disorders, 164 patients with autism, 784 patients with Alzheimer disease and 1280 healthy individuals remained for the enrichment analysis.

RESULTS

Overall, significant enrichment of dosage sensitive genes was found across patients with narcolepsy, panic disorders and autism. Particularly, significant enrichment of dosage-sensitive genes in duplications was observed across all diseases except for Alzheimer disease. For deletions, less or no enrichment of dosage-sensitive genes with deletions was seen in the patients when compared to the healthy individuals. Interestingly, significant enrichments of genes with expression sensitivity in brain were observed in patients with panic disorder and autism. While duplications presented a higher burden, deletions did not cause significant differences when compared to the healthy individuals. When we assess the effect of sensitivity to genome dosage and gene expression at the same time, the highest ratio of enrichment was observed in the group including dosage-sensitive genes and genes with expression sensitivity only in brain. In addition, shared CNV regions among the five neuropsychiatric diseases were also investigated.

CONCLUSIONS

This study contributed the evidence that dosage-sensitive genes are associated with CNVs among neuropsychiatric diseases. In addition, we utilized open data from GTEx to assess the effect of whole-genome CNVs on gene expression. We also investigated shared CNV region among neuropsychiatric diseases.

Comparative Analyses of Copy-Number Variation in Autism Spectrum Disorder and Schizophrenia Reveal Etiological Overlap and Biological Insights

Compelling evidence in Caucasian populations suggests a role for copy-number variations (CNVs) in autism spectrum disorder (ASD) and schizophrenia (SCZ). We analyzed 1,108 ASD cases, 2,458 SCZ cases, and 2,095 controls in a Japanese population and confirmed an increased burden of rare exonic CNVs in both disorders. Clinically significant (or pathogenic) CNVs, including those at 29 loci common to both disorders, were found in about 8% of ASD and SCZ cases, which was significantly higher than in controls. Phenotypic analysis revealed an association between clinically significant CNVs and intellectual disability. Gene set analysis showed significant overlap of biological pathways in both disorders including oxidative stress response, lipid metabolism/modification, and genomic integrity. Finally, based on bioinformatics analysis, we identified multiple disease-relevant genes in eight well-known ASD/SCZ-associated CNV loci (e.g., 22q11.2, 3q29). Our findings suggest an etiological overlap of ASD and SCZ and provide biological insights into these disorders.

A case of methamphetamine use disorder presenting a condition of ultra-rapid cycler bipolar disorder

Methamphetamine, a potent psychostimulant, may cause a condition of mood disorder among users. However, arguments concerning methamphetamine-induced mood disorder remain insufficient. This case study describes a male with methamphetamine-induced bipolar disorder not accompanied by psychotic symptoms, who twice in an 11-year treatment period, manifested an ultra-rapid cycler condition alternating between manic and depressive mood states with 3- to 7-day durations for each. The conditions ensued after a bout of high-dose methamphetamine use and shifted to a moderately depressive condition within 1 month after the use under a treatment regimen of aripiprazole and mood stabilizers. The cycler condition may be characteristic of a type of the bipolar disorder and a sign usable for characterization. Further efforts are needed to seek distinctive features and to improve diagnostic assessment of methamphetamine-induced mood disorders.

Mutations of the glycine cleavage system genes possibly affect the negative symptoms of schizophrenia through metabolomic profile changes

AIM

Hypofunction of N-methyl-D-aspartate receptors (NMDAR) may contribute to the pathophysiology of schizophrenia (SCZ). Recently, the glycine cleavage system (GCS) was shown to affect NMDAR function in the brain. GCS functional defects cause nonketotic hyperglycinemia, the atypical phenotype of which presents psychiatric symptoms similar to SCZ. Here, we examined the involvement of GCS in SCZ.

METHODS

First, to identify the rare variants and the exonic deletions, we resequenced all the coding exons and the splice sites of four GCS genes (GLDC, AMT, GCSH, and DLD) in 474 patients with SCZ and 475 controls and performed multiplex ligation-dependent probe amplification analysis in SCZ. Next, we performed metabolome analysis using plasma of patients harboring GCS variants (n = 5) and controls (n = 5) by capillary electrophoresis time-of-flight mass spectrometry. The correlation between plasma metabolites and Positive and Negative Syndrome Scale score was further examined.

RESULTS

Possibly damaging variants were observed in SCZ: A203V, S801N in GLDC, near the atypical nonketotic hyperglycinemia causative mutations (A202V, A802V); G825D in GLDC, a potential neural tube defect causative mutation; and R253X in AMT. Marked elevation of plasma 5-oxoproline (pyroglutamic acid), aspartate, and glutamate, which might affect NMDAR function, was observed in patients harboring GCS variants. The aspartate level inversely correlated with negative symptoms (r = -0.942, P = 0.0166).

CONCLUSION

These results suggest that GCS rare variants possibly contribute to the pathophysiology of SCZ by affecting the negative symptoms through elevation of aspartate.

Whole-exome sequencing and gene-based rare variant association tests suggest that PLA2G4E might be a risk gene for panic disorder

Panic disorder (PD) is characterized by recurrent and unexpected panic attacks, subsequent anticipatory anxiety, and phobic avoidance. Recent epidemiological and genetic studies have revealed that genetic factors contribute to the pathogenesis of PD. We performed whole-exome sequencing on one Japanese family, including multiple patients with panic disorder, which identified seven rare protein-altering variants. We then screened these genes in a Japanese PD case-control group (384 sporadic PD patients and 571 controls), resulting in the detection of three novel single nucleotide variants as potential candidates for PD (chr15: 42631993, T>C in GANC; chr15: 42342861, G>T in PLA2G4E; chr20: 3641457, G>C in GFRA4). Statistical analyses of these three genes showed that PLA2G4E yielded the lowest p value in gene-based rare variant association tests by Efficient and Parallelizable Association Container Toolbox algorithms; however, the p value did not reach the significance threshold in the Japanese. Likewise, in a German case-control study (96 sporadic PD patients and 96 controls), PLA2G4E showed the lowest p value but again did not reach the significance threshold. In conclusion, we failed to find any significant variants or genes responsible for the development of PD. Nonetheless, our results still leave open the possibility that rare protein-altering variants in PLA2G4E contribute to the risk of PD, considering the function of this gene.

Novel rare variations in genes that regulate developmental change in N-methyl-d-aspartate receptor in patients with schizophrenia

The mechanism underlying the vulnerability to developing schizophrenia (SCZ) during adolescence remains elusive. Hypofunction of N-methyl-d-aspartate receptors (NMDARs) has been implicated in the pathophysiology of SCZ. During development, the composition of synaptic NMDARs dramatically changes from NR2B-containing NMDARs to NR2A-containing NMDARs through the phosphorylation of NR2B S1480 or Y1472 by CDK5, CSNK2A1, and EphB2, which plays a pivotal role in the maturation of neural circuits. We hypothesized that the dysregulation of developmental change in NMDARs could be involved in the onset of SCZ. Using next-generation sequencing, we re-sequenced all the coding regions and splice sites of CDK5, CSNK2A1, and EphB2 in 474 patients with SCZ and 475 healthy controls. Variants on the database for human control subjects of Japanese origin were removed and all the nonsynonymous and nonsense variants were validated using Sanger sequencing. Four novel variants in CDK5 were observed in patients with SCZ but were not observed in controls. The total number of variants, however, was not significantly different between the SCZ and control groups (P=0.062). In silico analyses predicted P271T to be damaging. Further genetic research using a larger sample is required to examine whether CDK5 is involved in the pathophysiology of SCZ.

Identification of candidate genes involved in the etiology of sporadic Tourette syndrome by exome sequencing

Tourette Syndrome (TS) is a neurodevelopmental disorder characterized by chronic motor and vocal tics. Although there is a large genetic contribution, the genetic architecture of TS remains unclear. Exome sequencing has successfully revealed the contribution of de novo mutations in sporadic cases with neuropsychiatric disorders such as autism and schizophrenia. Here, using exome sequencing, we investigated de novo mutations in individuals with sporadic TS to identify novel risk loci and elucidate the genetic background of TS. Exome analysis was conducted for sporadic TS cases: nine trio families and one quartet family with concordant twins were investigated. Missense mutations were evaluated using functional prediction algorithms, and their population frequencies were calculated based on three public databases. Gene expression patterns in the brain were analyzed using the BrainSpan Developmental Transcriptome. Thirty de novo mutations, including four synonymous and four missense mutations, were identified. Among the missense mutations, one in the rapamycin-insensitive companion of mammalian target of rapamycin (RICTOR)-coding gene (rs140964083: G > A, found in one proband) was predicted to be hazardous. In the three public databases analyzed, variants in the same SNP locus were absent, and variants in the same gene were either absent or present at an extremely low frequency (3/5,008), indicating the rarity of hazardous RICTOR mutations in the general population. The de novo variant of RICTOR may be implicated in the development of sporadic TS, and RICTOR is a novel candidate factor for TS etiology.

Association of Aryl Hydrocarbon Receptor-Related Gene Variants with the Severity of Autism Spectrum Disorders

Exposure to environmental chemicals, such as dioxin, is known to have adverse effects on the homeostasis of gonadal steroids, thereby potentially altering the sexual differentiation of the brain to express autistic traits. Dioxin-like chemicals act on the aryl hydrocarbon receptor (AhR), polymorphisms, and mutations of AhR-related gene may exert pathological influences on sexual differentiation of the brain, causing autistic traits. To ascertain the relationship between AhR-related gene polymorphisms and autism susceptibility, we identified genotypes of them in patients and controls and determined whether there are different gene and genotype distributions between both groups. In addition, to clarify the relationships between the polymorphisms and the severity of autism, we compared the two genotypes of AhR-related genes (rs2066853, rs2228099) with the severity of autistic symptoms. Although no statistically significant difference was found between autism spectrum disorder (ASD) patients and control individuals for the genotypic distribution of any of the polymorphisms studied herein, a significant difference in the total score of severity was observed in rs2228099 polymorphism, suggesting that the polymorphism modifies the severity of ASD symptoms but not ASD susceptibility. Moreover, we found that a significant difference in the social communication score of severity was observed. These results suggest that the rs2228099 polymorphism is possibly associated with the severity of social communication impairment among the diverse ASD symptoms.

Effect of metabotropic glutamate receptor-3 variants on prefrontal brain activity in schizophrenia: An imaging genetics study using multi-channel near-infrared spectroscopy

BACKGROUND

The glutamatergic system is essential for learning and memory through its crucial role in neural development and synaptic plasticity. Genes associated with the glutamatergic system, including metabotropic glutamate receptor (mGluR or GRM) genes, have been implicated in the pathophysiology of schizophrenia. Few studies, however, have investigated a relationship between polymorphism of glutamate-related genes and cortical function in vivo in patients with schizophrenia. We thus explored an association between genetic variations in GRM3 and brain activation driven by a cognitive task in the prefrontal cortex in patients with schizophrenia.

MATERIALS AND METHODS

Thirty-one outpatients with schizophrenia and 48 healthy controls participated in this study. We measured four candidate single nucleotide polymorphisms (rs274622, rs2299225, rs1468412, and rs6465084) of GRM3, and activity in the prefrontal and temporal cortices during a category version of a verbal fluency task, using a 52-channel near-infrared spectroscopy instrument.

RESULTS AND DISCUSSION

The rs274622 C carriers with schizophrenia were associated with significantly smaller prefrontal activation than patients with TT genotype. This between-genotype difference tended to be confined to the patient group. GRM3 polymorphisms are associated with prefrontal activation during cognitive task in schizophrenia.

Genome-wide Association Study of Autism Spectrum Disorder in the East Asian Populations

Autism spectrum disorder is a heterogeneous neurodevelopmental disorder with strong genetic basis. To identify common genetic variations conferring the risk of ASD, we performed a two-stage genome-wide association study using ASD family and healthy control samples obtained from East Asian populations. A total of 166 ASD families (n = 500) and 642 healthy controls from the Japanese population were used as the discovery cohort. Approximately 900,000 single nucleotide polymorphisms (SNPs) were genotyped using Affymetrix Genome-Wide Human SNP array 6.0 chips. In the replication stage, 205 Japanese ASD cases and 184 healthy controls, as well as 418 Chinese Han trios (n = 1,254), were genotyped by TaqMan platform. Case-control analysis, family based association test, and transmission/disequilibrium test (TDT) were then conducted to test the association. In the discovery stage, significant associations were suggested for 14 loci, including 5 known ASD candidate genes: GPC6, JARID2, YTHDC2, CNTN4, and CSMD1. In addition, significant associations were identified for several novel genes with intriguing functions, such as JPH3, PTPRD, CUX1, and RIT2. After a meta-analysis combining the Japanese replication samples, the strongest signal was found at rs16976358 (P = 6.04 × 10(-7)), which is located near the RIT2 gene. In summary, our results provide independent support to known ASD candidate genes and highlight a number of novel genes warranted to be further investigated in a larger sample set in an effort to improve our understanding of the genetic basis of ASD.

Anger tendency may be associated with duration of illness in panic disorder

Background

Several studies have reported an increased tendency towards anger in patients with panic disorder (PD). If this propensity for anger arises from the pathological process of PD, it may be associated with the duration of the illness. The present study therefore examined the relationship between duration of PD and the personality tendency to experience anger in PD patients.

Methods

Participants were 413 patients (132 men and 281 women; age = 38.7 years) with PD. Diagnoses were confirmed using the Mini-International Neuropsychiatric Interview. Illness duration ranged from less than a year to 51 years. After participants completed the Revised NEO Personality Inventory, we examined the association between illness duration and the Angry Hostility and Impulsiveness subscale scores. In the analysis, participants were divided into two groups by duration of illness (long group, n = 186 and short group, n = 200) using the median value (9 years) as a cut-off because of the skewed distribution of the duration. Patients with an illness duration of 9 years (n = 27) were excluded from the comparison.

Results

The duration of illness was significantly correlated with the Angry Hostility score (p = 0.002) after controlling for age. Scores were significantly higher in the long group than in the short group (p = 0.04). No significant association was observed between Impulsiveness scores and duration of illness.

Conclusion

The present study suggests that longer PD duration is related to a stronger tendency to experience anger.

Gender-specific association between the COMT Val158Met polymorphism and openness to experience in panic disorder patients

BACKGROUND

Because major depression and panic disorder are both more prevalent among females and since several lines of evidence suggest that genetic factors might influence an individual's vulnerability to panic disorder, gene-gender interactions are being examined in such psychiatric disorders and mental traits. A number of studies have suggested that specific genes, e.g. catechol-O-methyltransferase (COMT), might lead to distinct clinical characteristics of panic disorder.

METHOD

We compared gender-specific personality-related psychological factors of 470 individuals with panic disorder and 458 healthy controls in terms of their COMT Val158Met polymorphism and their scores on the Revised NEO Personality Inventory (NEO PI-R) and State-Trait Anxiety Inventory (STAI) with a 1-way analysis of covariance.

RESULTS

In the male panic disorder patients, the NEO PI-R score for openness to experience was significantly lower in the Met/Met carrier group, whereas there was no such association among the female panic disorder patients or the male or female control groups.

CONCLUSION

The gender-specific effect of the COMT genotype suggests that the COMT Val/Met genotype may influence a personality trait, openness to experience, in males with panic disorder.

DNA modification study of major depressive disorder: beyond locus-by-locus comparisons

BACKGROUND

Major depressive disorder (MDD) exhibits numerous clinical and molecular features that are consistent with putative epigenetic misregulation. Despite growing interest in epigenetic studies of psychiatric diseases, the methodologies guiding such studies have not been well defined.

METHODS

We performed DNA modification analysis in white blood cells from monozygotic twins discordant for MDD, in brain prefrontal cortex, and germline (sperm) samples from affected individuals and control subjects (total N = 304) using 8.1K CpG island microarrays and fine mapping. In addition to the traditional locus-by-locus comparisons, we explored the potential of new analytical approaches in epigenomic studies.

RESULTS

In the microarray experiment, we detected a number of nominally significant DNA modification differences in MDD and validated selected targets using bisulfite pyrosequencing. Some MDD epigenetic changes, however, overlapped across brain, blood, and sperm more often than expected by chance. We also demonstrated that stratification for disease severity and age may increase the statistical power of epimutation detection. Finally, a series of new analytical approaches, such as DNA modification networks and machine-learning algorithms using binary and quantitative depression phenotypes, provided additional insights on the epigenetic contributions to MDD.

CONCLUSIONS

Mapping epigenetic differences in MDD (and other psychiatric diseases) is a complex task. However, combining traditional and innovative analytical strategies may lead to identification of disease-specific etiopathogenic epimutations.

Common variants at 1p36 are associated with superior frontal gyrus volume

The superior frontal gyrus (SFG), an area of the brain frequently found to have reduced gray matter in patients with schizophrenia, is involved in self-awareness and emotion, which are impaired in schizophrenia. However, no genome-wide association studies of SFG volume have investigated in patients with schizophrenia. To identify single-nucleotide polymorphisms (SNPs) associated with SFG volumes, we demonstrated a genome-wide association study (GWAS) of gray matter volumes in the right or left SFG of 158 patients with schizophrenia and 378 healthy subjects. We attempted to bioinformatically ascertain the potential effects of the top hit polymorphism on the expression levels of genes at the genome-wide region. We found associations between five variants on 1p36.12 and the right SFG volume at a widely used benchmark for genome-wide significance (P<5.0 × 10(-8)). The strongest association was observed at rs4654899, an intronic SNP in the eukaryotic translation initiation factor 4 gamma, 3 (EIF4G3) gene on 1p36.12 (P=7.5 × 10(-9)). No SNP with genome-wide significance was found in the volume of the left SFG (P>5.0 × 10(-8)); however, the rs4654899 polymorphism was identified as the locus with the second strongest association with the volume of the left SFG (P=1.5 × 10(-6)). In silico analyses revealed a proxy SNP of rs4654899 had effect on gene expression of two genes, HP1BP3 lying 3' to EIF4G3 (P=7.8 × 10(-6)) and CAPN14 at 2p (P=6.3 × 10(-6)), which are expressed in moderate-to-high levels throughout the adult human SFG. These results contribute to understand genetic architecture of a brain structure possibly linked to the pathophysiology of schizophrenia.

Gene×gene×gender interaction of BDNF and COMT genotypes associated with panic disorder

Genetic and gender differences are among the factors that have a role in the etiology of panic disorder (PD). It is thought that PD is related to neurotransmitter pathways, such as brain-derived neurotrophic factor (BDNF) and catechol-O-methyltransferase (COMT), both of which are involved in the regulation of the monoamine mechanism. We examined the interactions of BDNF, COMT and gender differences in terms of personality characteristics in PD. The subjects were 470 patients (178 men, 292 women) with a DSM-IV diagnosis of PD, and 458 healthy controls (195 men, 263 women). The subjects were further clinically characterized using the Revised NEO Personality Inventory (NEO-PI-R) and State-Trait Anxiety Inventory (STAI). COMT Val158Met polymorphisms (rs4680) and BDNF Val66Met (rs6265) polymorphisms were genotyped using allelic discrimination by a real-time PCR assay. A multivariate analysis of covariance (MANCOVA) was performed with STAI and NEO-PI-R scores as the dependent factor, gender and genotyping groups (BDNF and COMT) as fixed factors, and the covariate of age in the PD and healthy control groups. Post hoc MANCOVA tests were conducted to evaluate COMT × BDNF interactions. An interaction of BDNF × COMT × gender was confirmed in the PD group by MANCOVA on STAI scores and NEO-PI-R Neuroticism and Extraversion scores, whereas no association of such interactions was observed in the healthy controls. The anxiety sensitivity of the COMT Met+BDNF Val/Val carriers was higher than that of the COMT Val/Val+BDNF Val/Val carriers by post hoc MANCOVA. A significant BDNF × COMT × gender interaction was observed in the PD patients but not in the controls. Our findings partly demonstrated the involvement of a gene × gene × gender interaction in the pathogenesis of PD.

Associations between sleep habits and mental health status and suicidality in a longitudinal survey of monozygotic twin adolescents

Several epidemiological studies have indicated that there is a relationship between sleep habits, such as sleep duration, bedtime and bedtime regularity, and mental health status, including depression and anxiety in adolescents. However, it is still to be clarified whether the relationship is direct cause-and-effect or mediated by the influence of genetic and other traits, i.e. quasi-correlation. To examine this issue, we conducted a twin study using a total of 314 data for monozygotic twins from a longitudinal survey of sleep habits and mental health status conducted in a unified junior and senior high school (grades 7-12), located in Tokyo, Japan. Three-level hierarchical linear model analysis showed that both bedtime and sleep duration had significant associations with the Japanese version of the 12-item General Health Questionnaire (GHQ-12) score, suicidal thoughts and the experience of self-harm behaviours when genetic factors and shared environmental factors, which were completely shared between co-twins, were controlled for. These associations were statistically significant even after controlling for bedtime regularity, which was also associated significantly with the GHQ-12 score. These suggest that the associations between sleep habits and mental health status were still statistically significant after controlling for the influence of genetic and shared environmental factors of twins, and that there may be a direct cause-and-effect in the relationship in adolescents. Thus, late bedtime and short sleep duration could predict subsequent development of depression and anxiety, including suicidal or self-injury risk. This suggests that poor mental health status in adolescents might be improved by health education and intervention concerning sleep and lifestyle habits.

Irritable bowel syndrome, its cognition, anxiety sensitivity, and anticipatory anxiety in panic disorder patients

AIM

The present study examined the effect of irritable bowel syndrome (IBS), cognitive appraisal of IBS, and anxiety sensitivity on anticipatory anxiety (AA) and agoraphobia (AG) in patients with panic disorder (PD).

METHODS

We examined 244 PD patients who completed a set of questionnaires that included the Rome II Modular Questionnaire to assess the presence of IBS, the Anxiety Sensitivity Index (ASI), the Cognitive Appraisal Rating Scale (CARS; assessing the cognitive appraisal of abdominal symptoms in four dimensions: commitment, appraisal of effect, appraisal of threat, and controllability), and items about the severity of AA and AG. The Mini International Neuropsychiatric Interview was used to diagnose AG and PD.

RESULTS

After excluding individuals with possible organic gastrointestinal diseases by using 'red flag items,' valid data were obtained from 174 participants, including 110 PD patients without IBS (PD/IBS[-]) and 64 with IBS (PD/IBS[+]). The PD/IBS[+] group had higher AA and higher comorbidity with AG than the PD/IBS[-] group. In the PD/IBS[+] group, the controllability score of CARS was significantly correlated with AA and ASI. Multiple regression analysis showed a significant effect of ASI but not of controllability on AA in PD/IBS[+] subjects.

CONCLUSION

This study suggested that the presence of IBS may be related to agoraphobia and anticipatory anxiety in PD patients. Cognitive appraisal could be partly related to anticipatory anxiety in PD patients with IBS with anxiety sensitivity mediating this correlation.

DNA methylation analysis of BDNF gene promoters in peripheral blood cells of schizophrenia patients

Accumulating evidence suggests that epigenetic alterations in brain-derived neurotrophic factor (BDNF) promoters are associated with the pathophysiology of psychiatric disorders. Epigenetic changes in BDNF were reported not only in brain tissues but also in other tissues, including peripheral blood cells (PBC) and saliva. We examined DNA methylation levels of BDNF promoters I and IV using genomic DNA derived from PBC of healthy controls (n=100), and patients with schizophrenia (n=100), all from the Japanese population, by pyrosequencing. The examined CpG sites were chosen based on previous epigenetic studies that reported altered DNA methylation. We found a significantly higher level of methylation at BDNF promoter I in patients with schizophrenia compared to controls, although the difference was small. Subsequent analysis revealed that in controls, the methylation level of BDNF promoters was associated with sex, and the methylation difference observed in promoter I was more prominent in male patients with schizophrenia. Epigenetic alteration of BDNF in the PBC might reflect the pathophysiology of schizophrenia, and could be a potential biomarker.

Neural correlate of autistic-like traits and a common allele in the oxytocin receptor gene

Sub-clinical autistic-like traits (ALTs) are continuously distributed in the general population and genetically linked to autism. Although identifying the neurogenetic backgrounds of ALTs might enhance our ability to identify those of autism, they are largely unstudied. Here, we have examined the neuroanatomical basis of ALTs and their association with the oxytocin receptor gene (OXTR) rs2254298A, a known risk allele for autism in Asian populations which has also been implicated in limbic-paralimbic brain structures. First, we extracted a four-factor structure of ALTs, as measured using the Autism-Spectrum Quotient, including 'prosociality', 'communication', 'details/patterns' and 'imagination' in 135 neurotypical adults (79 men, 56 women) to reduce the genetic heterogeneity of ALTs. Then, in the same population, voxel-based morphometry revealed that lower 'prosociality', which indicates strong ALTs, was significantly correlated to smaller regional grey matter volume in the right insula in males. Males with lower 'prosociality' also had less interregional structural coupling between the right insula and the ventral anterior cingulate cortex. Furthermore, males with OXTR rs2254298A had significantly smaller grey matter volume in the right insula. These results show that decreased volume of the insula is a neuroanatomical correlate of ALTs and a potential intermediate phenotype linking ALTs with OXTR in male subjects.

Prevalence of bipolar disorder in panic disorder patients in the Japanese population

BACKGROUND

We examined the rate of bipolar I (BPD-I) and bipolar II disorders (BPD-II) in panic disorder (PD) patients, and compared clinical and psychological variables between PD patients with and without bipolar disorders (BPD).

METHODS

Participants were 649 Japanese patients with PD (215 men and 434 women, 38.49 ± 10.40 years) at outpatient clinics for anxiety disorders. Constructive interviews using the Mini-International Neuropsychiatric Interview (MINI) were conducted to confirm the diagnosis of PD, agoraphobia, and BPD, as well as the presence and severity of suicide risk in each subject. Clinical records were also reviewed to confirm the diagnosis of PD and BPD. Participants then completed several questionnaires, including the State Trait Anxiety Inventory-Trait scale, the Anxiety Sensitivity Index, and the Revised Neuroticism-Extraversion- Openness Personality Inventory (NEO-PI-R).

RESULTS

We found that 22.34% of the PD patients had BPD (BPD-I: 5.24%, BPD-II: 17.10%). PD patients with BPD-I showed higher prevalence and severity of suicide risk, trait anxiety, anxiety sensitivity, and neuroticism, and lower agreeableness (subscales of the NEO-PI-R) than those with BPD-II and those without BPD.

LIMITATION

First, we could not investigate the order of the onset of PD and BPD. Second, BPD patients without PD were not studied as another control group for PD patients with BPD.

CONCLUSION

PD patients had high prevalence of BPD. Both PD patients with BPD-I and those with BPD-II had high severity of suicide risk, trait anxiety, anxiety sensitivity, neuroticism, and agreeableness, though these characteristics were more prominent in patients with BPD-I.

Season of birth effect on psychotic-like experiences in Japanese adolescents

A number of studies have investigated seasonality of birth in schizophrenia. Most of the studies have consistently observed an excess of winter births, often associated with decreased summer births. We postulated that psychotic-like experiences (PLEs), subclinical hallucinatory and delusional experiences, may also be affected by birth season. In the present study, we assessed the season of birth effect on the prevalence of PLEs using data from the cross-sectional survey of 19,436 Japanese adolescents. As a result, significant excess of winter births was observed in the prevalence of PLEs, accompanied by a decreased proportion of summer births. The odds ratios for the prevalence of PLEs were estimated to be 1.11, which was on the same order with those for the development of schizophrenia in the previous meta-analytic studies. To our knowledge, this is the first to show the seasonality of birth in the prevalence of PLEs and implicate the winter birth effect on subclinical stage of schizophrenia.

Irregular bedtime and nocturnal cellular phone usage as risk factors for being involved in bullying: a cross-sectional survey of Japanese adolescents

Purpose

A number of studies have tried to identify risk factors for being involved in bullying in order to help developing preventive measures; however, to our knowledge, no study has investigated the effect of nocturnal lifestyle behavior such as sleep pattern or cellular phone usage. In the present study, we aimed to investigate the relationship between school bullying and sleep pattern or nocturnal cellular phone usage in adolescents. The effect of school size on school bullying was also examined.

Methods

Data from the cross-sectional survey of psychopathologies conducted for 19,436 Japanese students from 45 public junior high schools (7^th–9^th grade) and 28 senior high schools (10^th–12^th grade) were analyzed.

Results

Bullying status was significantly associated with irregular bedtime (OR = 1.23 and 1.41 for pure bullies and bully-victims, respectively) and e-mail exchange or calling after lights-out (OR = 1.53 and 1.31 for pure bullies and bully-victims, respectively) after controlling domestic violence and substance usage. In addition, school size was significantly associated with the increased risk of bullying in junior high school students (OR = 1.13 for bully-victims).

Conclusions

The present results suggested that sleep pattern and nocturnal cellular phone usage might be risk factors for being involved in school bullying in adolescents. Although further accumulation of data is needed, progressive trend towards nocturnal lifestyle and increasing usage of cellular phone might impair the well-being of adolescents. School-based interventions for lifestyle including sleep pattern and cellular phone usage may be encouraged to reduce school bullying.

5-hmC in the brain is abundant in synaptic genes and shows differences at the exon-intron boundary

5-hydroxymethylcytosine (5-hmC), a derivative of 5-methylcytosine (5-mC), is abundant in the brain for unknown reasons. Our goal was to characterize the genomic distribution of 5-hmC and 5-mC in human and mouse tissues. We assayed 5-hmC using glucosylation coupled with restriction enzyme digestion, and interrogation on microarrays. We detected 5-hmC enrichment in genes with synapse-related functions in both human and mouse brain. We also identified substantial tissue-specific differential distributions of these DNA modifications at the exon-intron boundary, in both human and mouse. This boundary change was mainly due to 5-hmC in the brain, but due to 5-mC in non-neural contexts. This pattern was replicated in multiple independent datasets and with single molecule sequencing. Moreover, in human frontal cortex, constitutive exons contained higher levels of 5-hmC, relative to alternatively-spliced exons. Our study suggests a novel role for 5-hmC in RNA splicing and synaptic function in the brain.

A multi-tissue analysis identifies HLA complex group 9 gene methylation differences in bipolar disorder

Epigenetic studies of DNA and histone modifications represent a new and important activity in molecular investigations of human disease. Our previous epigenome-wide scan identified numerous DNA methylation differences in post-mortem brain samples from individuals affected with major psychosis. In this article, we present the results of fine mapping DNA methylation differences at the human leukocyte antigen (HLA) complex group 9 gene (HCG9) in bipolar disorder (BPD). Sodium bisulfite conversion coupled with pyrosequencing was used to interrogate 28 CpGs spanning ∼700 bp region of HCG9 in 1402 DNA samples from post-mortem brains, peripheral blood cells and germline (sperm) of bipolar disease patients and controls. The analysis of nearly 40 000 CpGs revealed complex relationships between DNA methylation and age, medication as well as DNA sequence variation (rs1128306). Two brain tissue cohorts exhibited lower DNA methylation in bipolar disease patients compared with controls at an extended HCG9 region (P=0.026). Logistic regression modeling of BPD as a function of rs1128306 genotype, age and DNA methylation uncovered an independent effect of DNA methylation in white blood cells (odds ratio (OR)=1.08, P=0.0077) and the overall sample (OR=1.24, P=0.0011). Receiver operating characteristic curve A prime statistics estimated a 69-72% probability of correct BPD prediction from a case vs control pool. Finally, sperm DNA demonstrated a significant association (P=0.018) with BPD at one of the regions demonstrating epigenetic changes in the post-mortem brain and peripheral blood samples. The consistent multi-tissue epigenetic differences at HCG9 argue for a causal association with BPD.

Association of SNPs linked to increased expression of SLC1A1 with schizophrenia

Glutamate is one of the key molecules involved in signal transduction in the brain, and dysfunction of glutamate signaling could be linked to schizophrenia. The SLC1A1 gene located at 9p24 encodes the glutamate transporter EAAT3/EAAC1. To investigate the association between the SLC1A1 gene and schizophrenia in the Japanese population, we genotyped 19 tagging single nucleotide polymorphisms (tagSNPs) in the SLC1A1 gene in 576 unrelated individuals with schizophrenia and 576 control subjects followed by replication in an independent case-control study of 1,344 individuals with schizophrenia and 1,344 control subjects. In addition, we determined the boundaries of the copy number variation (CNV) region in the first intron (Database of Genomic Variants, chr9:4516796-4520549) and directly genotyped the CNV because of significant deviation from the Hardy-Weinberg equilibrium. The CNV was not associated with schizophrenia. Four SNPs showed a possible association with schizophrenia in the screening subjects and the associations were replicated in the same direction (nominal allelic P < 0.05), and, among them, an association with rs7022369 was replicated even after Bonferroni correction (allelic nominal P = 5 × 10(-5) , allelic corrected P = 2.5 × 10(-4) , allelic odds ratio, 1.30; 95% CI: 1.14-1.47 in the combined subjects). Expression analysis quantified by the real-time quantitative polymerase chain reaction in the postmortem prefrontal cortex of 43 Japanese individuals with schizophrenia and 11 Japanese control subjects revealed increased SLC1A1 expression levels in individuals homozygous for the rs7022369 risk allele (P = 0.003). Our findings suggest the involvement of SLC1A1 in the pathogenesis of schizophrenia.

Positive association of phencyclidine-responsive genes, PDE4A and PLAT, with schizophrenia

As schizophrenia-like symptoms are produced by administration of phencyclidine (PCP), a noncompetitive antagonist of N-methyl-D-aspartate (NMDA) receptors, PCP-responsive genes could be involved in the pathophysiology of schizophrenia. We injected PCP to Wistar rats and isolated five different parts of the brain in 1 and 4 hr after the injection. We analyzed the gene expression induced by the PCP treatment of these tissues using the AGILENT rat cDNA microarray system. We observed changes in expression level in 90 genes and 21 ESTs after the treatment. Out of the 10 genes showing >2-fold expressional change evaluated by qRT-PCR, we selected 7 genes as subjects for the locus-wide association study to identify susceptibility genes for schizophrenia in the Japanese population. In haplotype analysis, significant associations were detected in combinations of two SNPs of BTG2 (P = 1.4 × 10(-6) ), PDE4A (P = 1.4 × 10(-6) ), and PLAT (P = 1 × 10(-3) ), after false discovery rate (FDR) correction. Additionally, we not only successfully replicated the haplotype associations in PDE4A (P = 6.8 × 10(-12) ) and PLAT (P = 0.015), but also detected single-point associations of one SNP in PDE4A (P = 0.0068) and two SNPs in PLAT (P = 0.0260 and 0.0104) in another larger sample set consisting of 2,224 cases and 2,250 controls. These results indicate that PDE4A and PLAT may be susceptibility genes for schizophrenia in the Japanese population.

Effects of metabotropic glutamate receptor 3 genotype on phonetic mismatch negativity

Background

The genetic and molecular basis of glutamatergic dysfunction is one key to understand schizophrenia, with the identification of an intermediate phenotype being an essential step. Mismatch negativity (MMN) or its magnetic counterpart, magnetic mismatch field (MMF) is an index of preattentive change detection processes in the auditory cortex and is generated through glutamatergic neurotransmission. We have previously shown that MMN/MMF in response to phoneme change is markedly reduced in schizophrenia. Variations in metabotropic glutamate receptor (GRM3) may be associated with schizophrenia, and has been shown to affect cortical function. Here we investigated the effect of GRM3 genotypes on phonetic MMF in healthy men.

Methods

MMF in response to phoneme change was recorded using magnetoencephalography in 41 right-handed healthy Japanese men. Based on previous genetic association studies in schizophrenia, 4 candidate SNPs (rs6465084, rs2299225, rs1468412, rs274622) were genotyped.

Results

GRM3 rs274622 genotype variations significantly predicted MMF strengths (p = 0.009), with C carriers exhibiting significantly larger MMF strengths in both hemispheres compared to the TT subjects.

Conclusions

These results suggest that variations in GRM3 genotype modulate the auditory cortical response to phoneme change in humans. MMN/MMF, particularly those in response to speech sounds, may be a promising and sensitive intermediate phenotype for clarifying glutamatergic dysfunction in schizophrenia.

Association of RGS2 variants with panic disorder in a Japanese population

Panic disorder (PD) is a severe and chronic psychiatric disorder with significant genetic components underlying its etiology. The gene regulator of G protein signaling 2 (RGS2) has been reported to be associated with anxiety disorders. To confirm the association of RGS2 with PD, we investigated three single nucleotide polymorphisms (SNPs) of RGS2 (rs10801152, rs4606, and rs1819741) in 677 Japanese PD cases and 460 controls. The SNP rs10801152 was suggestive of an association with PD (allele P = 0.045 adjusted using sex and age as confounding factors). The three-SNP haplotype was significantly associated with PD (global permutation P = 4 × 10(-4)). The haplotypes T-G-C and T-C-T showed significant association and protective effect on PD (T-G-C, permutation P = 0.038, OR = 0.80, 95%CI = 0.68-0.95; T-C-T, permutation P = 0.004, OR = 0.38, 95%CI = 0.21-0.70). These results provide support for an association of RGS2 with PD in a Japanese population.

Association study of PDE4B with panic disorder in the Japanese population

BACKGROUND

Panic disorder (PD) is a severe and chronic psychiatric disorder with genetic components underlying in its etiology. The Phosphodiesterase 4B (PDE4B) gene has been reported to be associated with several psychiatric disorders. Several studies indicated that PDE4B may be involved in the regulation of anxiety and depression. Therefore, we investigate the association of PDE4B with PD in the Japanese population.

METHODS

We genotyped 14 single nucleotide polymorphisms (SNPs) of PDE4B in 231 PD cases (85 males and 146 females) and 407 controls (162 males and 245 females). Differences in the genotype, allele and haplotype frequencies between the two groups were compared.

RESULTS

We found a significant association between PDE4B and PD in the haplotype analysis (haplotype C-T-T-A, permutation P=0.031, OR=1.81, 95% CI=1.30-2.51). Sex-specific analyses demonstrated that PDE4B was associated with PD in females in the allele/genotype and haplotype analyses (rs10454453, allele P=0.042, genotype P=0.0034; haplotype C-T-T-A, permutation P=0.028).

CONCLUSION

Our results suggest that PDE4B may play a role in the pathophysiology of PD in the Japanese population. Replication studies using larger samples will be needed for more reliable conclusions.

Association between the oxytocin receptor gene and amygdalar volume in healthy adults

BACKGROUND

Recent studies have suggested that oxytocin affects social cognition and behavior mediated by the oxytocin receptor (OXTR) in amygdala in humans as well as in experimental animals. Genetic studies have revealed a link between the OXTR gene and the susceptibility to autism spectrum disorders (ASD), especially in the social dysfunctional feature of ASD.

METHODS

We examined the relationship between amygdala volume measured with manual tracing methodology and seven single nucleotide polymorphisms and one haplotype-block in OXTR, which were previously reported to be associated with ASD, in 208 socially intact Japanese adults with no neuropsychiatric history or current diagnosis.

RESULTS

The rs2254298A allele of OXTR was significantly associated with larger bilateral amygdala volume. The rs2254298A allele effect on amygdala volume varied in proportion to the dose of this allele. The larger the number of rs2254298A alleles an individual had, the larger their amygdala volume. Such an association was not observed with hippocampal volume or with global brain volumes, including whole gray, white matter, and cerebrospinal-fluid space. Furthermore, two three-single nucleotide polymorphism haplotypes, including rs2254298G allele, showed significant associations with the smaller bilateral amygdala volume.

CONCLUSIONS

The present results suggest that OXTR might be associated with the susceptibility to ASD, especially in its aspects of social interaction and communication mediated by a modulation of amygdala development, one of the most distributed brain regions with high density of OXTR. Furthermore, amygdala volume measured with magnetic resonance imaging could be a useful intermediate phenotype to uncover the complex link between OXTR and social dysfunction in ASD.

Effect of tryptophan hydroxylase-2 gene variants on amygdalar and hippocampal volumes

Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the synthesis of serotonin (5-HT). Genetic variations in human TPH2, a newly identified isoform of TPH, have been shown to impact on enzymatic activity of TPH and to be associated with emotion-related personality traits and mood/anxiety disorders. Identification of an intermediate phenotype that bridges the relationship between genes and behavior may be of great importance in the further clarification of how hTPH2 contributes to emotional regulation. Previous studies have shown that a polymorphism in the upstream regulatory region of hTPH2 (SNP G-703T, rs4570625) correlates functional MRI response of the amygdala. In this study, we examined the effect of this genotype on amygdalar and hippocampal volumes in 208 mentally healthy individuals. To measure volumes of amygdala and hippocampus, gray matter regions of interest were outlined manually on three-dimensional MRI data obtained using a 1.5-T scanner. Additionally, personality traits were evaluated using the Temperament and Character Inventory (TCI). Those subjects with T allele carriers were associated with significantly smaller volumes in bilateral amygdala and hippocampus and higher reward dependence than those with G allele homozygotes. These results suggest that amygdalar and hippocampal volumes assessed using MRI may be a useful intermediate phenotype that will uncover the biological pathway linking 5-HT synthesis and emotional behaviors and affective disorders.

Association of the oxytocin receptor (OXTR) gene polymorphisms with autism spectrum disorder (ASD) in the Japanese population

The oxytocin receptor (OXTR) gene, which is located on chromosome 3p25.3, has been implicated as a candidate gene for susceptibility of autism spectrum disorder (ASD). Positive associations between OXTR and ASD have been reported in earlier studies. However, the results were inconsistent and demand further studies. In this study, we investigated the associations between OXTR and ASD in a Japanese population by analyzing 11 single-nucleotide polymorphisms (SNPs) using both family-based association test (FBAT) and population-based case-control test. No significant signal was detected in the FBAT test. However, significant differences were observed in allelic frequencies of four SNPs, including rs2254298 between patients and controls. The risk allele of rs2254298 was 'A', which was consistent with the previous study in Chinese, and not with the observations in Caucasian. The difference in the risk allele of this SNP in previous studies might be attributable to an ethnic difference in the linkage disequilibrium structure between the Asians and Caucasians. In addition, haplotype analysis exhibits a significant association between a five-SNP haplotype and ASD, including rs22542898. In conclusion, our study might support that OXTR has a significant role in conferring the risk of ASD in the Japanese population.

Replication of a genome-wide association study of panic disorder in a Japanese population

Panic disorder (PD) is an anxiety disorder characterized by recurrent and unexpected panic attacks, subsequent worry and phobic avoidance. Although a number of association and linkage studies have been conducted, no gene has been identified as a susceptibility locus. We previously conducted a genome-wide association analysis of PD in 200 Japanese patients and the same number of controls, using a 500 K single nucleotide polymorphisms (SNPs) chip. In this study, we report a replication analysis of PD using the DigTag2 assay. The second stage sample consisted of 558 Japanese patients and 566 controls. Thirty-two markers were tested in a replication sample. As a result, no significant association was found after correction for multiple testing. However, the difference was observed at the nominal allele P-value <0.05 for two SNPs (rs6733840 and rs132617). We also conducted haplotype analyses of SNPs in the APOL3 and CLU genes. Our results failed to show any significant association with PD in these genes. Further studies on these variants with a larger sample size may be worth testing to confirm the results.

Association between catechol-O-methyltrasferase Val108/158Met genotype and prefrontal hemodynamic response in schizophrenia

Background

“Imaging genetics” studies have shown that brain function by neuroimaging is a sensitive intermediate phenotype that bridges the gap between genes and psychiatric conditions. Although the evidence of association between functional val108/158met polymorphism of the catechol-O-methyltransferase gene (COMT) and increasing risk for developing schizophrenia from genetic association studies remains to be elucidated, one of the most topical findings from imaging genetics studies is the association between COMT genotype and prefrontal function in schizophrenia. The next important step in the translational approach is to establish a useful neuroimaging tool in clinical settings that is sensitive to COMT variation, so that the clinician could use the index to predict clinical response such as improvement in cognitive dysfunction by medication. Here, we investigated spatiotemporal characteristics of the association between prefrontal hemodynamic activation and the COMT genotype using a noninvasive neuroimaging technique, near-infrared spectroscopy (NIRS).

Methodology/Principal Findings

Study participants included 45 patients with schizophrenia and 60 healthy controls matched for age and gender. Signals that are assumed to reflect regional cerebral blood volume were monitored over prefrontal regions from 52-channel NIRS and compared between two COMT genotype subgroups (Met carriers and Val/Val individuals) matched for age, gender, premorbid IQ, and task performance. The [oxy-Hb] increase in the Met carriers during the verbal fluency task was significantly greater than that in the Val/Val individuals in the frontopolar prefrontal cortex of patients with schizophrenia, although neither medication nor clinical symptoms differed significantly between the two subgroups. These differences were not found to be significant in healthy controls.

Conclusions/Significance

These data suggest that the prefrontal NIRS signals can noninvasively detect the impact of COMT variation in patients with schizophrenia. NIRS may be a promising candidate translational approach in psychiatric neuroimaging.

Association between sigma-1 receptor gene polymorphism and prefrontal hemodynamic response induced by cognitive activation in schizophrenia

The molecular biological role of the sigma-1 receptor (Sig-1R) has attracted much attention. Evidence suggests that the Sig-1R engaged in modulating NMDA and dopamine receptors is involved in the pathophysiology of schizophrenia and the mechanism of psychotropic drug efficacy. However, whether the Sig-1R genotype affects brain function in schizophrenia in vivo remains unknown. We investigated the association between Sig-1R functional polymorphism (Gln2Pro) and brain function in schizophrenia. The subjects were 40 patients with schizophrenia and 60 healthy controls, all right-handed, who gave written informed consent to participate. Signals, detected from prefrontal regions by 52-channel near-infrared spectroscopy (NIRS) during cognitive activation, were compared between two Sig1-R genotype subgroups (Gln/Gln individuals and Pro carriers) matched for age, gender, premorbid IQ and task performance. The prefrontal hemodynamic response of healthy controls during the verbal fluency task was higher than that of patients with schizophrenia. For the patients with schizophrenia, even after controlling the effect of medication, the [oxy-Hb] increase in the prefrontal cortex of the Gln/Gln genotype group was significantly greater than that of the Pro carriers (false discovery rate corrected p<0.05). Clinical symptoms were not significantly different between the two Sig-1R genotype subgroups. These differences were not significant in the healthy controls. This is the first functional imaging genetics study that implicated the association between Sig-1R genotype and prefrontal cortical function in schizophrenia in vivo. Our findings also suggest that the prefrontal hemodynamic response assessed by noninvasive and less demanding NIRS is a useful intermediate phenotype for translational research in schizophrenia.