Association study of the 15q11-q13 maternal expression domain in Japanese autistic patients

Chromosome 15q11-q13 has been a focus of genetic studies of autism susceptibility, because cytogenetic abnormalities are frequently observed in this region in autistic patients. An imprinted, maternally expressed gene within the region may have a role in autistic symptomatology. In the present study, we investigated the association between autism and the maternal expression domain (MED) in the region, containing the UBE3A and ATP10C genes, and the upstream imprinting center (IC), which mediates coordinate control of imprinted expression throughout the region. We analyzed 41 single nucleotide polymorphisms (SNPs) in 166 patients with autism and 416 controls from a Japanese population. As a result, a statistically significant difference after correction for multiple testing was observed between the patients and controls in the genotypic distribution of SNP rs7164989 (SNP8 in this study) located in SNRPN, whose promoter corresponds to the IC (P = 0.018, corrected for multiple testing). In the analysis of a four-marker haplotype located in ATP10C, a statistically significant difference after correction for multiple testing was observed in the frequency of one haplotype between male patients and controls (permutation P = 0.033, corrected for multiple testing). Thus, the present study may suggest the association between autism and the MED or the upstream IC in chromosome 15q11-q13 in the Japanese population.

Association and interaction analyses of NRG1 and ERBB4 genes with schizophrenia in a Japanese population

Neuregulin 1 (NRG1) is one of the most promising candidate genes for schizophrenia. A number of replication studies have been conducted, although the results were inconsistent and no susceptible variant has yet been identified. The inconsistency might be attributed to the ethnic difference in allele and haplotype frequencies. However, it is equally possible that one or more genes interacting with NRG1 may also be implicated in schizophrenia and attribute to the inconsistency. To test the hypothesis, we conducted an interaction analysis between NRG1 and one of its receptor's (ERBB4) polymorphisms as well as the association analysis of the two genes associated with schizophrenia in Japanese. We observed no significant difference between patients and controls in allele frequencies or genotypic distributions of the 18 polymorphisms of the genes. The permutation test showed no significant differences in estimated haplotype frequencies between patients and controls, including the haplotype HAP(ICE). In the interaction analysis, significant interaction was observed between rs2919381 in NRG1 and rs7560730 in ERBB4 (P = 0.047, corrected). Thus, our results suggest the possibility that interaction between variants in NRG1 and ERBB4 might contribute to susceptibility for schizophrenia in a Japanese population. Further investigation may be necessary to confirm our results.

Up-regulation of ADM and SEPX1 in the lymphoblastoid cells of patients in monozygotic twins discordant for schizophrenia

The contribution of genetic factors to schizophrenia is well established and recent studies have indicated several strong candidate genes. However, the pathophysiology of schizophrenia has not been totally elucidated yet. To date, studies of monozygotic twins discordant for schizophrenia have provided insight into the pathophysiology of this illness; this type of study can exclude inter-individual variability and confounding factors such as effects of drugs. In this study we used DNA microarray analysis to examine the mRNA expression patterns in the lymphoblastoid (LB) cells derived from two pairs of monozygotic twins discordant for schizophrenia. From five independent replicates for each pair of twins, we selected five genes, which included adrenomedullin (ADM) and selenoprotein X1 (SEPX1), as significantly changed in both twins with schizophrenia. Interestingly, ADM was previously reported to be up-regulated in both the LB cells and plasma of schizophrenic patients, and SEPX1 was included in the list of genes up-regulated in the peripheral blood cells of schizophrenia patients by microarray analysis. Then, we performed a genetic association study of schizophrenia in the Japanese population and examined the copy number variations, but observed no association. These findings suggest the possible role of ADM and SEPX1 as biomarkers of schizophrenia. The results also support the usefulness of gene expression analysis in LB cells of monozygotic twins discordant for an illness.

Association between mitochondrial DNA 10398A>G polymorphism and the volume of amygdala

Mitochondrial calcium regulation plays a number of important roles in neurons. Mitochondrial DNA (mtDNA) is highly polymorphic, and its interindividual variation is associated with various neuropsychiatric diseases and mental functions. An mtDNA polymorphism, 10398A>G, was reported to affect mitochondrial calcium regulation. Volume of hippocampus and amygdala is reportedly associated with various mental disorders and mental functions and is regarded as an endophenotype of mental disorders. The present study investigated the relationship between the mtDNA 10398A>G polymorphism and the volume of hippocampus and amygdala in 118 right-handed healthy subjects. The brain morphometry using magnetic resonance images employed both manual tracing volumetry in the native space and voxel-based morphometry (VBM) in the spatially normalized space. Amygdala volume was found to be significantly larger in healthy subjects with 10398A than in those with 10398G by manual tracing, which was confirmed by the VBM. Brain volumes in the other gray matter regions and all white matter regions showed no significant differences associated with the polymorphism. These provocative findings might provide a clue to the complex relationship between mtDNA, brain structure and mental disorders.

No association between the ryanodine receptor 3 gene and autism in a Japanese population

AIM

Autism is a neurodevelopmental disorder with a complex genetic etiology. Chromosome 15q11-q14 has been proposed to harbor a gene for autism susceptibility because deletion of the region leads to Prader-Willi syndrome or Angelman syndrome, having phenotypic overlap with autism. Here we studied the association between autism and the ryanodine receptor 3 (RyR3) gene, which is located in the region. This is the first study, to our knowledge, that has investigated the association.

METHODS

We genotyped 14 tag single nucleotide polymorphisms (SNPs) in 166 Japanese patients with autism and 375 controls.

RESULTS

No significant difference was observed between the patients and controls in allelic frequencies or genotypic distributions of the 14 SNPs. Analysis after confining the subjects to males showed similar results.

CONCLUSIONS

The present study provides no positive evidence for the association between the RyR3 gene and autism in the Japanese population.

Characteristics of fatigue in panic disorder patients

It was suggested that fatigue is one of characteristics of panic disorder. Fatigue was assessed in 360 patients with panic disorder using the Japanese version of the Multidimensional Fatigue Inventory (MFI-J). The scores for general fatigue and reduced activity were significantly higher in the patients than in the controls. These tendencies were also observed in men when the subject group was differentiated according to sex, but not in women. In contrast, the trend for higher score for physical fatigue was observed only in the female patients. Thus, the present study suggests that the characteristics of fatigue vary with sex in panic disorder.

Methylation status of the reelin promoter region in the brain of schizophrenic patients

BACKGROUND

Hypermethylation of the reelin (RELN) promoter region and the reduced levels of its messenger RNA and protein have been implicated in the pathophysiology of schizophrenia. We intended a technical replication of recent studies that observed hypermethylation of CpG or CpNpG sites in the RELN promoter region in the brain of schizophrenic patients.

METHODS

The DNA methylation status of the promoter region of RELN was examined by using the pyrosequencing method in the prefrontal cortices of 14 patients with schizophrenia and 13 control subjects.

RESULTS

All of the CpG and two proposed CpNpG sites analyzed showed no detectable DNA methylation (< 5%) in both control subjects and patients with schizophrenia. No detectable DNA methylation was observed in both gray and white matter, excluding the possibility of cellular heterogeneity of start materials.

CONCLUSIONS

We did not confirm the hypermethylation of the RELN promoter region in the brains of schizophrenic patients, suggested in the previous studies.

Global hypomethylation of peripheral leukocyte DNA in male patients with schizophrenia: a potential link between epigenetics and schizophrenia

Genetic and epigenetic factors can potentially alter susceptibility to psychiatric disorders such as schizophrenia. In order to explore the effect of epigenetics on the pathogenesis of schizophrenia, we examined the global methylation level of leukocyte DNA from 210 patients with schizophrenia (124 males and 86 females) and 237 healthy subjects (108 males and 129 females). Methylated deoxycytidine (mC) content in peripheral leukocyte DNA was measured by high performance liquid chromatography (HPLC). We confirmed in the healthy subjects our previous finding that there are sex-dependent differences in mC content (males>females; beta=0.319, p<0.001), in addition to the effect of age (beta=-0.141, p=0.022). We therefore used multiple regression to analyze the data from all subjects by sex, with age as a co-variant. In males, a tendency was observed toward lower mC content in patients than in controls (beta=-0.115, p=0.075), with a significant effect of age (beta=-0.212, p<0.001). This difference was more prominent in younger individuals. In females, no effect of age or disease status on mC content was observed. These results established that there is significant sex-dependent difference in the mC content of human peripheral leukocyte DNA, and raise the possibility that alterations in DNA methylation state are present in patients with schizophrenia.

Association study of monoamine oxidase and catechol-O-methyltransferase genes with smoking behavior

OBJECTIVE

The genes of catalytic enzymes of dopamine, including monoamine oxidase (MAOA and MAOB) and catechol-O-methyltransferase (COMT), have been major candidates for genes that affect smoking behavior. In this study, we investigated the relationship between smoking behavior and four polymorphisms of these genes, the MAOA variable number tandem repeat polymorphism, the MAOA 1460 T/C polymorphism, the MAOB intron 13 G/A polymorphism, and the COMT Val158Met polymorphism. The association between the MAOB polymorphism and personality traits was also explored.

PARTICIPANTS AND METHODS

The polymorphisms were genotyped in 451 healthy Japanese volunteers. Data on smoking habits were obtained from structured interviews. In addition to testing the association between each polymorphism and smoking status, epistatic and additive effects between two polymorphisms were also investigated.

RESULTS

A significant association was observed between the COMT Val158Met polymorphism and smoking status. Male participants with the Val/Val genotype had a significantly higher risk of heavy smoking compared with those with other genotypes, although no significant association was observed in female participants. No evidence was obtained for an association between the MAO genes and smoking behavior, including epistatic or additive effects. No significant association was observed between the MAOB polymorphism and personality traits.

CONCLUSION

This study may suggest a role of the COMT Val158Met polymorphism in smoking behavior in Japanese individuals.

Association study between the cholecystokinin A receptor gene and schizophrenia in the Japanese population

Cholecystokinin A receptor (CCK-AR) has been implicated in the pathophysiology of schizophrenia through its mediation of dopamine-release in the central nervous system. Several studies have observed the association between the CCK-AR gene and schizophrenia. Especially, the association has been repeatedly observed between the 779T/C polymorphism and auditory hallucinations or positive symptoms of schizophrenia. In this study, we investigated the association between the 779T/C polymorphism of the CCK-AR gene and schizophrenia in 290 Japanese patients with schizophrenia and 290 controls. As a result, no significant difference was observed in genotypic distributions or allelic frequencies between the patients and controls, although there was a trend for the association between the C allele of the polymorphism and hallucination (P=0.024) or hallucinatory-paranoid state (P=0.049). In conclusion, the present results may not provide evidence for the association between the CCK-AR gene and schizophrenia in the Japanese population.

Association analysis of HSP90B1 with bipolar disorder

Pathophysiological role of endoplasmic reticulum (ER) stress response signaling has been suggested for bipolar disorder. The goal of this study was to test the genetic association between bipolar disorder and an ER chaperone gene, HSP90B1 (GRP94/gp96), which is located on a candidate locus, 12q23.3. We tested the genetic association between bipolar disorder and HSP90B1 by case-control studies in two independent Japanese sample sets and by a transmission disequilibrium test (TDT) in NIMH Genetics initiative bipolar trio samples (NIMH trios). We also performed gene expression analysis of HSP90B1 in lymphoblastoid cells. Among the 11 SNPs tested, rs17034977 showed significant association in both Japanese sample sets. The frequency of the SNP was lower in NIMH samples than in Japanese samples and there was no significant association in NIMH trios. Gene expression analysis of HSP90B1 in lymphoblastoid cells suggested a possible relationship between the associated SNP and mRNA levels. HSP90B1 may have a pathophysiological role in bipolar disorder in the Japanese population, though further study will be needed to understand the underlying functional mechanisms.

Association study between the TNXB locus and schizophrenia in a Japanese population

The chromosome 6p21-24 region, which contains the human leukocyte antigen (HLA) region, has been suggested as an important locus for a susceptibility gene for schizophrenia. Recently, a significant association between schizophrenia and the TNXB locus, located immediately telomeric of the NOTCH4 locus in the HLA region, was observed. Few studies have further investigated the region in schizophrenia. In the present study, we investigated the region in a Japanese population. Subjects included 241 patients with schizophrenia and 290 controls. Twenty-six single nucleotide polymorphisms (SNPs) and the corresponding haplotypes were analyzed. As a result, exactly the same SNPs in the TNXB locus (rs1009382 and rs204887) as in the previous study were associated with schizophrenia (P = 0.034 and 0.034, respectively, uncorrected). A SNP (rs2071287) in the NOTCH4 locus and haplotype around it were also suggested to associate with the disease, consistent with another previous study (P = 0.041 and permutation P = 0.024, respectively, uncorrected). Although these associations became insignificant after Bonferroni correction, the findings might provide support for the association of the TNXB locus or its adjacent region of the NOTCH4 locus with schizophrenia.

Gender-Common and -Specific Neuroanatomical Basis of Human Anxiety-Related Personality Traits

Exploration of the relationships between regional brain volume and anxiety-related personality traits is important for understanding preexisting vulnerability to depressive and anxiety disorders. However, previous studies on this topic have employed relatively limited sample sizes and/or image processing methodology, and they have not clarified possible gender differences. In the present study, 183 (male/female: 117/66) right-handed healthy individuals in the third and fourth decades of life underwent structural magnetic resonance imaging scans and Temperament and Character Inventory. Neuroanatomical correlates of individual differences in the score of harm avoidance (HA) were examined throughout the entire brain using voxel-based morphometry. We found that higher scores on HA were associated with smaller regional gray matter volume in the right hippocampus, which was common to both genders. In contrast, female-specific correlation was found between higher anxiety-related personality traits and smaller regional brain volume in the left anterior prefrontal cortex. The present findings suggest that smaller right hippocampal volume underlies the basis for higher anxiety-related traits common to both genders, whereas anterior prefrontal volume contributes only in females. The results may have implications for why susceptibility to stress-related disorders such as anxiety disorders and depression shows gender and/or individual differences.

Human brain structural change related to acute single exposure to sarin

OBJECTIVE

This study aimed to identify persistent morphological changes subsequent to an acute single-time exposure to sarin, a highly poisonous organophosphate, and the neurobiological basis of long-lasting somatic and cognitive symptoms in victims exposed to sarin.

METHODS

Thirty-eight victims of the 1995 Tokyo subway sarin attack, all of whom had been treated in an emergency department for sarin intoxication, and 76 matched healthy control subjects underwent T1-weighted and diffusion tensor magnetic resonance imaging (DTI) in 2000 to 2001. Serum cholinesterase (ChE) levels measured immediately and longitudinally after the exposure and the current severity of chronic reports in the victims were also evaluated.

RESULTS

The voxel-based morphometry exhibited smaller than normal regional brain volumes in the insular cortex and neighboring white matter, as well as in the hippocampus in the victims. The reduced regional white matter volume correlated with decreased serum cholinesterase levels and with the severity of chronic somatic complaints related to interoceptive awareness. Voxel-based analysis of diffusion tensor magnetic resonance imaging further demonstrated an extensively lower than normal fractional anisotropy in the victims. All these findings were statistically significant (corrected p < 0.05).

INTERPRETATION

Sarin intoxication might be associated with structural changes in specific regions of the human brain, including those surrounding the insular cortex, which might be related to elevated subjective awareness of internal bodily status in exposed individuals.

No association between the metabotropic glutamate receptor type 3 gene (GRM3) and schizophrenia in a Japanese population

Several lines of evidence have suggested that the metabotropic glutamate receptor 3 (GRM3) gene is a candidate susceptibility gene for schizophrenia. To our knowledge, six studies have investigated the genetic association between GRM3 and schizophrenia, although the results have been quite controversial. In the present study, we investigated the association between the GRM3 gene and schizophrenia in 402 Japanese people by analyzing 10 single nucleotide polymorphisms (SNPs), including all SNPs that showed significant results in previous studies. We observed no significant difference in allelic frequencies or genotypic distributions of the 10 SNPs between the controls and patients. A permutation test showed no significant global differences in estimated haplotype frequencies between the controls and patients. Thus, the present study provides no positive evidence of an association between the GRM3 gene and schizophrenia in the Japanese population.

Insertional polymorphism of endogenous retrovirus HERV-K115 in schizophrenia

Retroviruses are implicated in the pathogenesis of schizophrenia. Human endogenous retrovirus type K115 (HERV-K115) is a full-length, potentially transcriptional retrovirus and is also polymorphic. We investigated the frequency of HERV-K115 in Japanese schizophrenia patients and healthy controls. No difference was found in the frequency between patients and controls (8.4% versus 9.4%, respectively). However, a marginal difference was observed in age at onset between the HERV-K positive and negative patients (p=0.057). The HERV-K115 insertion appeared to be more frequent in patients with younger onset than those with later onset. These results preliminarily suggest that HERV-K115 may not be associated with schizophrenia in general, but that it could play a partial role in early precipitation of the disease.

No association of DRD2, DRD3, and tyrosine hydroxylase gene polymorphisms with personality traits in the Japanese population

BACKGROUND

Dopamine D2 receptor (DRD2) and dopamine D3 receptor (DRD3) genes could be candidates for personality-related genes considering their pharmacological profiles or structures. However, a limited number of studies have investigated the association between these genes and personality traits. In the present study, we investigated the DRD2, DRD3, and tyrosine hydroxylase (TH) genes in relation to personality traits in the Japanese population. Epistasis (gene-gene interaction) among the genes was extensively analyzed, in addition to the analysis based on each gene.

METHODS

The -241A/G, -141C Ins/Del, and Ser311Cys polymorphisms in the DRD2 gene, the Ser9Gly polymorphism of the DRD3 gene, and the Val81Met and PstI site polymorphisms in the TH gene were genotyped in 257 healthy Japanese subjects. Personality traits were evaluated by using the Revised NEO Personality Inventory (NEO PI-R) and the State-Trait Anxiety Inventory (STAI). The associations between gene polymorphisms and the scores for NEO PI-R or Trait Anxiety of STAI were statistically analyzed by one-way analysis of covariance (ANCOVA) adjusting sex and age. Epistasis was assessed using two-way ANCOVA between the polymorphisms of independent two genes.

RESULTS

In the analysis based on each gene, trends for association were observed between State Anxiety and the DRD2 -141C Ins/Del polymorphism (p = 0.031, uncorrected), and between Trait Anxiety and the DRD2 Ser311Cys or TH PstI site polymorphism (p = 0.048 and 0.041, respectively, uncorrected). In epistatic analysis, a trend for interaction was observed on the scores for Neuroticism and Trait Anxiety between the DRD2 -141C Ins/Del and TH Val81Met polymorphisms (p = 0.015 and 0.010, respectively, uncorrected). However, these differences were insignificant after Bonferroni correction.

CONCLUSION

The present study did not provide evidence for the association between these dopamine-related genes and personality traits in the Japanese population.

No association between the CNTF null mutation and schizophrenia or personality

The ciliary neurotrophic factor (CNTF) is a neurotrophic cytokine that plays a critical role in neurodevelopment. On the basis of neurodevelopmental hypothesis, the CNTF gene has been a candidate locus for schizophrenia. Several studies have investigated the association between the null mutation of the gene and schizophrenia, however, with inconsistent results. In the present study, we investigated the association in 222 Japanese patients with schizophrenia and 237 controls. The association between the mutation and personality traits was also studied, to investigate the effect of the mutation in participants from the general population. As a result, no association was observed between the mutation and schizophrenia nor personality traits, evaluated by using the Revised NEO Personality Inventory scores. The present study did not provide evidence for the association between the CNTF gene and schizophrenia or personality traits in the Japanese population.

Clinical features of soft bipolarity in major depressive inpatients

Because of the difficulties of ascertaining episode of hypomania by past history of the patients, it is of clinical value to find variables which predict the development of bipolar II disorder in depressive patients. Taking advantage of relatively long hospitalization, the authors tried to elucidate fine clinical features of the soft bipolarity. The subjects were 39 patients with Major Depressive Episode, diagnosed according to the 4th edition of the Diagnostic and Statistical Manual criteria. Among them, 15 patients were diagnosed as bipolar II disorder (BPII), whereas 24 patients were with unipolar depression (UP), using a structured clinical interview to assess the mood spectrum (SCI-MOODS). In addition to ordinary clinical and demographic variables, the authors studied fine symptomatology of depression, premorbid personality, and interpersonal relationship. Continuous variables were analyzed by t-test. Categorical variables were tested by chi2 analysis. In terms of premorbid personality, manic type (Zerssen) was found more frequently in BPII (UP 2/24, BPII 9/15, P < 0.05). Patients with BPII tended to show apparently quick disappearance of depressive symptoms (UP 2/24, BPII 9/15, P = 0.01). The most prominent result was a high prevalence of comorbidity of borderline personality disorder (BPD) among BPII (UP 0/24, BPII 6/15, P = 0.02). As Akiskal indicated that mood lability represents the most powerful predictor of hypomanias, patients with BPII showed quick response in mood to admission. The current subjects with BPII had high frequency of manic type of premorbid personality, indicating the usefulness of this variable for the prediction of hypomanias. Finally, the authors could observe development of BPD during hospitalization exclusively among BPII, to support the possibility of BPD as a state effect of BPII.

No evidence for an association between the BDNF Val66Met polymorphism and schizophrenia or personality traits

Brain-derived neurotrophic factor (BDNF) is a member of the nerve growth factor family, which plays a critical role in neurodevelopment. Based on the neurodevelopmental hypothesis, the BDNF gene has been a candidate locus for schizophrenia. In Caucasians, recent studies identified an association with the Val66Met polymorphism, which has been suggested to affect episodic memory and hippocampal function in humans. However, in other populations, the association has not been replicated. In the present study, we investigated the association between the Val66Met polymorphism of the gene and schizophrenia in 401 Japanese patients with schizophrenia and 569 controls. As a result, we did not observe a significant difference in genotypic distribution or allele frequencies between the patients and controls (chi2=0.56, df=2, p=0.76 and chi2=0.39, df=1, p=0.53, respectively). We also investigated the association between the polymorphism and personality traits in the controls; however, no significant association was observed. Thus, the present study did not provide evidence for an association between the BDNF gene and schizophrenia or personality traits in the Japanese population.

Association study of the dysbindin (DTNBP1) gene in schizophrenia from the Japanese population

Dysbindin (DTNBP1: dystrobrevin binding protein 1), located on 6p22.3, is a candidate susceptibility gene for schizophrenia. Several studies, mostly in Caucasians, have provided evidence for an association between schizophrenia and the gene, although no common polymorphism or haploytpe has been established. In Asian populations, two studies investigated a limited number of single nucleotide polymorphisms (SNPs) of dysbindin and observed support for the association. In the present study, we investigated 12 SNPs of dysbindin, including those examined in previous Asian studies, and the corresponding haplotypes in a Japanese people with schizophrenia. As a result, no significant difference was observed between patients and controls in allelic frequencies or genotypic distributions of the 12 SNPs. Permutation test however showed significant differences in frequencies of the estimated 10-marker haplotypes between patients and controls (global p = 0.006). The present study may provide further support for an association between dysbindin and schizophrenia in Asian populations. The results might be similar to a previous Asian study, but specific haplotypes suggested for the association differed between the studies. Studies with more markers and subjects may be required before firm conclusions can be reached.

No association between the Clara cell secretory protein (CC16) gene polymorphism and personality traits

Clara cell secretory protein (CC16) is an anti-inflammatory protein expressed in the respiratory tract. Several studies have suggested the association between CC16 and mental disturbances, such as schizophrenia, depression, and post-traumatic stress disorder. In the present study, we investigated the association between the CC16 gene A38G polymorphism and personality traits in 214 healthy Japanese subjects. Personality traits were evaluated by using the Revised NEO Personality Inventory (NEO PI-R) and the State-Trait Anxiety Inventory (STAI). As a result, no significant association was observed between the genotypes and the scores of the NEO PI-R or the STAI. The present results suggest that CC16 may not have a major role in the development of personality traits.

Association between corticotropin-releasing hormone receptor 2 (CRHR2) gene polymorphism and personality traits

Corticotropin-releasing hormone (CRH) has been implicated in the pathophysiology of anxiety disorders and depression. Corticotropin-releasing hormone receptor 2 (CRHR2) is one of the receptors that mediate CRH signal. The purpose of the present study was to investigate the association between the CRHR2 gene and personality traits, evaluated using the Revised NEO Personality Inventory (NEO PI-R), in 243 healthy Japanese subjects. As a result, significant association was observed between the polymorphism in intron 2 (rs2267717) and Openness (P = 0.004, uncorrected, anova), while no relationship was observed concerning Neuroticism. The present result suggests an association between CRHR2 and the personality trait of Openness.

No association of 5-HT2C, 5-HT6, and tryptophan hydroxylase-1 gene polymorphisms with personality traits in the Japanese population

Serotonin 2C receptor (5-HT(2C)), serotonin 6 receptor (5-HT(6)), and tryptophan hydroxylase-1 (TPH1) genes could be candidates for personality-related genes considering the role of serotonin in various mental functions and behavior. However, a limited number of studies have investigated the association between these genes and personality traits. In the present study, we investigated the three serotonin-related genes, 5-HT(2C), 5-HT(6), and TPH1 genes, in relation to personality traits in the Japanese population. The Cys23Ser polymorphisms in the 5-HT(2C) gene, the 267T/C polymorphism of the 5-HT(6) gene, and the 779A/C polymorphisms in the TPH1 gene were genotyped in 253 healthy Japanese subjects. Personality traits were evaluated by using the Revised NEO Personality Inventory (NEO PI-R) and the State-Trait Anxiety Inventory (STAI). As a result, no significant association was observed between the polymorphisms and the NEO PI-R or the STAI scores. The present results did not provide evidence for the association between the three serotonin-related genes and personality traits. The genes might not have major role in the development of personality traits, although further investigation with larger sample size may be recommended for conclusion.

Association between dopamine D4 receptor (DRD4) exon III polymorphism and Neuroticism in the Japanese population

The association between the dopamine D4 receptor (DRD4) exon III polymorphism and personality trait of novelty seeking (NS) has been studied intensively. In the Japanese population, the results of the previous studies did not always coincide. In the present study, we investigated the association between the polymorphism and personality traits evaluated by using the Revised NEO Personality Inventory (NEO PI-R) and State-Trait Anxiety Inventory (STAI) in 196 Japanese subjects. A meta-analysis of the present and previous Japanese studies was also conducted regarding NS. As a result, significant association was observed between the polymorphism and personality traits evaluated by using NEO PI-R as a whole (p=0.022, MANCOVA). Subsequent analyses showed a significant association between short alleles (2-4 repeats) and higher scores for Neuroticism or its subscales, Anxiety, Depression, and Vulnerability (p=0.015, 0.039, 0.021, and 0.008, respectively, uncorrected). No other significant difference in the scores for NEO PI-R was observed in the subsequent analyses. Significant association was also observed between the polymorphism and scores for STAI as a whole (p=0.004, MANCOVA). Subsequent analyses did not show significant association, although a weak trend for the relation between the genotype consisting of short alleles and Trait Anxiety was observed (p=0.10, uncorrected). The meta-analysis showed no significant association between the polymorphism and NS. Thus, the present study suggested the association between the short allele of the DRD4 exon III polymorphism and personality trait of Neuroticism in Japanese subjects.

Association of mitochondrial complex I subunit gene NDUFV2 at 18p11 with schizophrenia in the Japanese population

Schizophrenia and bipolar disorder share common genetic background. Several loci such as 18p11, 13q32, and 22q11-13 were commonly linked with these diseases. Since mitochondrial dysfunction has been suggested in both of these disorders, NDUFV2 at 18p11, encoding a subunit of the complex I, NADH ubiquinone oxidoreductase, is a candidate gene for these diseases. We previously reported that single nucleotide polymorphisms (SNPs) in the upstream region of NDUFV2 were associated with bipolar disorder in Japanese. The association of haplotype consisting of two SNPs, -3542G > A and -602G > A, with bipolar disorder was also seen both in Japanese and the National Institute of Mental Health Pedigrees trios. In this study, 2 polymorphisms, -3542G > A and -602G > A, were investigated in 229 schizophrenic patients as compared with controls. Individual genotypes were not associated with schizophrenia. However, the haplotype consisting of these two SNPs were significantly associated with schizophrenia. These results suggested that inter-individual variation of the genomic sequence of the promoter region of NDUFV2 might be a genetic risk factor common to bipolar disorder and schizophrenia.

Combined analysis of association between personality traits and three functional polymorphisms in the tyrosine hydroxylase, monoamine oxidase A, and catechol-O-methyltransferase genes

Several molecular genetic studies have been conducted with regard to the association between catecholamine-related genes and personality traits. However, the results of replication studies did not always coincide. One of the possible reasons may be that the effect exerted by the individual gene is small. In the present study, we investigated the association between personality traits and systematic combination of functional polymorphisms in three genes that regulate the metabolism of catecholamines, namely, tyrosine hydroxylase (TH), monoamine oxidase A (MAOA), and catechol-O-methyltransferase (COMT). The (TCAT)n repeat in the TH gene, the promoter variable number tandem repeat (VNTR) in the MAOA gene, and Val158Met in the COMT gene were genotyped in 256 healthy Japanese volunteers. Personality traits were evaluated using the NEO Personality Inventory-Revised (NEO PI-R). As a result, the score for Neuroticism increased, and those for Extraversion and Conscientiousness decreased according to the degree of functional polymorphic change, i.e., the lower synthesis/higher catalysis of catecholamines. A statistically significant difference was observed in the change of Extraversion (p=0.04, after Bonferroni correction). These results may provide evidence for the association between metabolic change of catecholamines and personality traits, which may be due to the additive effect of the three genes.

Functional polymorphisms of HSPA5: possible association with bipolar disorder

Altered endoplasmic reticulum stress (ER) response signaling is suggested in bipolar disorder. Previously, we preliminarily reported the genetic association of HSPA5 (GRP78/BiP) with bipolar disorder. Here, we extended our analysis by increasing the number of Japanese case-control samples and NIMH Genetics Initiative bipolar trio samples (NIMH trios), and also analyzed schizophrenia samples. In Japanese, nominally significant association of one haplotype was observed in extended samples of bipolar disorder but not in schizophrenia. In NIMH trios, no association was found in total samples. However, an exploratory analysis suggested that the other haplotype was significantly over-transmitted to probands only from the paternal side. The associated haplotype in Japanese or NIMH pedigrees shared three common polymorphisms in the promotor, which was found to alter promotor activity. These findings suggested promotor polymorphisms of HSPA5 may affect the interindividual variability of ER stress response and may confer a genetic risk factor for bipolar disorder.

Association study of the DISC1/TRAX locus with schizophrenia in a Japanese population

Disrupted-in-Schizophrenia-1 (DISC1), identified by cytogenetic approaches in a pedigree with familial psychosis, is considered a candidate susceptibility gene for schizophrenia in some populations. In the pedigree, the TRAX gene, located adjacent to DISC1 on the disrupted chromosome 1, may also contribute to the pathophysiology of the familial schizophrenia. We studied association of the DISC1 and TRAX genes with schizophrenia in 338 Japanese by analyzing 15 single nucleotide polymorphisms (SNPs), including 12 SNPs in DISC1 and three in TRAX, respectively. No significant difference was observed between the patients and controls in allelic frequencies or genotypic distributions of 15 SNPs. A weak trend for the association in genotypic distribution of one SNP in TRAX (major homo/hetero/minor homo: 0.324/0.431/0.245 vs. 0.293/0.526/0.181 for patients vs controls, p = 0.039 in the 2 x 3 comparison) turned out to be insignificant after Bonferroni correction. Haplotype analysis did not support the association between the patients and controls. The present study suggests that the DISC1/TRAX locus may not have a major role in Japanese schizophrenia.

Mitochondrial DNA sequence analysis of patients with 'atypical psychosis'

Although classical psychopathological studies have shown the presence of an independent diagnostic category, 'atypical psychosis', most psychotic patients are currently classified into two major diagnostic categories, schizophrenia and bipolar disorder, by the Diagnostic and Statistical Manual of Mental Disorders (4th edn; DSM-IV) criteria. 'Atypical psychosis' is characterized by acute confusion without systematic delusion, emotional instability, and psychomotor excitement or stupor. Such clinical features resemble those seen in organic mental syndrome, and differential diagnosis is often difficult. Because patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) sometimes show organic mental disorder, 'atypical psychosis' may be caused by mutations of mitochondrial DNA (mtDNA) in some patients. In the present study whole mtDNA was sequenced for seven patients with various psychotic disorders, who could be categorized as 'atypical psychosis'. None of them had known mtDNA mutations pathogenic for mitochondrial encephalopathy. Two of seven patients belonged to a subhaplogroup F1b1a with low frequency. These results did not support the hypothesis that clinical presentation of some patients with 'atypical psychosis' is a reflection of subclinical mitochondrial encephalopathy. However, the subhaplogroup F1b1a may be a good target for association study of 'atypical psychosis'.

XBP1 gene polymorphism (-116C/G) and personality

Recently, a polymorphism of the XBP1 gene (-116 C/G) was observed to play a significant role in the development of bipolar mood disorder from the Japanese population. The present study investigated a role of the polymorphism in the development of personality in healthy Japanese volunteers (n = 195). Personality traits were evaluated using NEO Personality Inventory-Revised (NEO PI-R). As a result, a statistical trend for association between the polymorphism (genotype) and the NEO PI-R scores of agreeableness and neuroticism was observed (ANOVA, P = 0.01 and 0.006, respectively). Subjects with the G allele, especially those with G-G genotype, tended to show lower neuroticism and higher agreeableness in the present study. The result is provisional and should be interpreted with caution, partly because the previous study suggested the allele as a risk allele for bipolar disorder. Further studies are required to confirm the results.

Seasonality of schizophrenia births in the Japanese population: increased winter births possibly confined to the north area

A number of North American and European studies have observed a higher proportion of winter births in schizophrenia patients. Thus, seasonal fluctuation of unknown environmental factors may affect brain development in ways that alter susceptibility to schizophrenia. Specification of these factors may help elucidate the etiopathological mechanism of the disease, about which little is certain. A small number of studies have investigated this issue in Asian populations, and the findings are not as consistent as those of Western populations. No remarkable excess of winter births has been observed in Japanese or Korean studies, while some studies have reported a significant decrease of summer births. We further investigated the issue in Japanese patients with schizophrenia (n=3927). No significant excess of winter births was observed, but a decrease in the summer births was found in male subjects. This is largely consistent with previous Japanese studies; however, when the subjects were confined to those born in a colder and higher latitude area of Japan (n=1338), a consistent trend for both a winter increase, and a summer decrease, was found. However, the results did not consistently reach statistical significance, possibly due to the lack of statistical power. Environmental factors that correlate with latitude might play a role in the development of the seasonality of births in schizophrenia. Further studies in a larger sample size are required to test these possibilities.

Serotonin 2A receptor gene polymorphism and personality traits: no evidence for significant association

A number of studies have observed associations between the serotonin 2A (5-HT2A) receptor and mental disorders. Here, we investigated correlations between polymorphisms (-1438G/A and 102T/C) of the 5-HT2A gene and personality traits in healthy Japanese volunteers (n = 239). The personality traits were evaluated using the Revised NEO Personality Inventory (NEO PI-R). The -1438G/A and 102T/C were in complete linkage disequilibrium. There was a tendency for associations between the genotype and the scores for Agreeableness, Conscientiousness and Neuroticism of the NEO PI-R (P = 0.028, 0.039 and 0.062, respectively; analysis of variance, uncorrected for multiple testing). Subjects with the A/A of -1438G/A (or T/T of 102T/C) appeared to be lower in Neuroticism and higher in Conscientiousness than the rest of the subjects. However, the results were statistically non-significant after Bonferroni's correction for multiple testing of the five scales of the NEO PI-R. Thus, the present study provided no evidence for statistically significant associations between the 5-HT2A polymorphisms and the personality traits.

Association between the neurofibromatosis-1 (NF1) locus and autism in the Japanese population

Autistic patients have a 100 to 190-fold increased risk of neurofibromatosis compared to the general population. This suggests that the two diseases may share a common etiological background. Recently, a new allele (or the six-repeat allele) of the (AAAT)(n) repeat polymorphism in an Alu sequence in the neurofibromatosis-1 (NF1) gene was observed exclusively in severe autistic patients, not in controls, in Caucasians of French ancestry. This suggests a role of the NF1 gene in the development of autism. We investigated three microsatellite polymorphisms within the intron-27b and intron-38 of the NF1 region, including the (AAAT)(n) and two (CA)n repeat polymorphisms, in Japanese subjects with autism (n = 74) and controls (n = 122). The six-repeat allele of the (AAAT)(n) polymorphism was not found either in patients or controls, possibly indicating an ethnic difference in the polymorphism. However, significant differences were observed in the allele distributions of the (AAAT)(n) and a (CA)(n), which were located at intron-27b, between patients and controls, although an association was not significant between autism and another polymorphism at intron-38. This may suggest an involvement of the NF1 locus in susceptibility to autism, although further investigations are recommended.

Association of the XBP1-116C/G polymorphism with schizophrenia in the Japanese population

Schizophrenia and bipolar disorder share some clinical features and linkage studies have shown that several loci are common. Recently, the authors found that the -116C-->G substitution in the promotor region of XBP1, a pivotal gene in endoplasmic reticulum (ER) stress response, causes the impairment of ER stress response, and that the -116C/C genotype is a protective factor; in other words the presence of the G allele increases the risk for bipolar disorder. The gene is located on 22q12.1, which is also linked with schizophrenia. The polymorphisms were investigated in 234 schizophrenic patients as compared with controls. Significant difference of genotype distribution was observed, which suggested that the -116C/C genotype is a protective factor for both of the major mental disorders.

Association of six polymorphisms of the NOTCH4 gene with schizophrenia in the Japanese population

The NOTCH4 gene is located at 6p21.3 and involved in the development and patterning of the central nervous systems. Recently, Wei and Hemmings [2000] observed that the gene was associated with schizophrenia. Subsequent to the report, several studies investigated the gene in schizophrenia, with controversial and inconclusive results. In the present study, we investigated six polymorphisms (SNPs 1-5 and a CTG repeat) of the gene in Japanese subjects with schizophrenia (n = 284) and the same number of controls. The polymorphisms include SNP5, which has been observed to be associated with schizophrenia in a Chinese population and two new SNPs 3-4 adjacent to SNP5, in addition to the SNPs 1-2 and the CTG repeat, which were suggested for the association with the disease in the previous study. As a result, no significant difference in genotypic distributions or allelic frequencies of the six polymorphisms of the gene was observed between the patients and the controls. Also, no significant difference was found in frequencies of haplotypes of the six polymorphisms between the patients and the controls. However, the distribution of SNP2 was significantly deviated from Hardy-Weinberg equilibrium in the patients (P = 0.000986), not in the controls, which could be a chance or due to an association of SNP2 with the disease. In conclusion, the present study provided no clear evidence for an association between the NOTCH4 gene and schizophrenia in the Japanese population.

Mitochondrial DNA polymorphisms and extraversion

Mitochondria is the major site of energy production in cells, therefore, mitochondrial abnormality may affect functions of organs including the brain, which constantly requires high levels of energy consumption. Previous studies have suggested a role of mitochondria and their DNA polymorphisms in neuro-psychiatric disorders, including Alzheimer's disease, Parkinson's disease, schizophrenia and bipolar mood disorder. Thus, we hypothesized that mitochondrial DNA polymorphisms might be related with the development of personality. The present study investigated a role of two mitochondrial DNA polymorphisms, the C5178A and A10398G, in personality traits evaluated using the NEO PI-R scores in 238 healthy Japanese volunteers. Subjects with the 5178A genotype showed significantly higher extraversion score than those with the 5178C genotype (P = 0.027), while no significant association was observed between the C5178A polymorphism and other scores. No significant association was found between the A10398G polymorphism and any scores. Regarding the 5178-10398 haplotype, the score of extraversion, not other scores, was significantly associated with the A-G haplotype (P = 0.042). Although further studies are recommended for the confirmation, the result may suggest a role of the mitochondrial DNA polymorphism in the personality trait.

Season of birth effect on personality in a general population

Seasonality of births in schizophrenia and other mental disorders has been consistently observed. This may be through effects of unknown environmental factors that seasonally fluctuate on the brain development. The effects may affect cognitive function of the brain and behavioral characteristics that might be correlated with the development of personality not only in patients with mental disorders but also in healthy subjects. We, therefore, investigated the effects of season of birth on personality traits in healthy Japanese adults (n = 397). Personality traits were evaluated using the NEO Personality Inventory-Revised (NEO PI-R). A trend for lower Agreeableness in subjects born during winter (December to February) than other subjects was observed (P = 0.036, after correction for the multiple testing, multiple regression analysis adjusting for age and sex). Other major factors of the NEO PI-R, including Neuroticism, Extraversion, Openness and Conscientiousness, were not affected by season of birth. Further studies may be recommended to confirm the results, considering the relatively limited sample size. Evaluation of cognitive functions and behaviors using other measures including event-related potentials and functional MRI may also help the interpretation of the present result.

What causes seasonality of birth in schizophrenia?

An excess of winter-spring births (and/or a decrease of summer births) has consistently been observed in schizophrenia (SCZ). This observation may provide a significant clue about the causes of the disease if specific factors which cause the phenomenon can be determined. This paper reviews several studies which investigated factors correlated with this observation in SCZ, in an attempt to determine which factors more likely cause the seasonality. Among the candidates of the factors are meteorological variables (such as ambient temperature), several infections, maternal hormones, sperm quality, nutrition and external toxins. A variation of procreation might also have an effect. Among the factors, the most extensively studied are temperature and viral infections. Some of them have appeared promising, but further studies are definitely required. Several challenges, including complicated correlations of the factors and determination of the susceptible period during pregnancy, need to be overcome. Comparisons of the data from areas and cohorts with different patterns of the candidate factors may be helpful. Animal studies may also help investigate the molecular and physiological mechanisms of the phenomenon.

Gastrin-releasing peptide receptor (GRPR) locus in Japanese subjects with autism

Gastrin-releasing peptide receptor (GRPR) gene is considered a candidate locus for infantile autism for several reasons. The present study investigated two polymorphic sites (C/450/T and C/661/T) in the second exon of the GRPR gene in Japanese patients with autism (DSM-IV) and healthy subjects. The two polymorphic sites were at high linkage disequilirium, consistent with a previous study in a North American population. The C450-C661 allele, which was observed in one-third of the chromosomes from the North American subjects, was less frequent (6-7%) in the Japanese subjects, suggesting a large ethnic difference in the frequency of the polymorphism. The allele frequencies and genotype distributions were not significantly different between the patients and controls. However, further studies are required to exclude the GRPR locus as a candidate locus for autism, considering the low frequency of the polymorphism in the Japanese subjects.

Voxel-based analysis of MRI reveals anterior cingulate gray-matter volume reduction in posttraumatic stress disorder due to terrorism

MRI studies using the manual tracing method have shown a smaller-than-normal hippocampal volume in patients with posttraumatic stress disorder (PTSD). However, these studies have yielded inconsistent results, and brain structures other than the hippocampus have not been well investigated. A recently developed, fully automated method called voxel-based morphometry enables an exploration of structural changes throughout the brain by applying statistical parametric mapping to high-resolution MRI. Here we first used this technology in patients with PTSD. Participants were 9 victims of the Tokyo subway sarin attack with PTSD and 16 matched victims of the same traumatic event without PTSD. The voxel-based morphometry showed a significant gray-matter volume reduction in the left anterior cingulate cortex (ACC) in trauma survivors with PTSD compared with those without PTSD. The severity of the disorder was negatively correlated with the gray-matter volume of the left ACC in PTSD subjects. There were no significant differences in other gray-matter regions or any of the white-matter regions between two groups. The present study demonstrates evidence for structural abnormalities of ACC in patients with PTSD. Together with previous functional neuroimaging studies showing a dysfunction of this region, the present findings provide further support for the important role of ACC, which is pivotally involved in attention, emotional regulation, and conditioned fear, in the pathology of PTSD.

Serotonin transporter-linked promoter region polymorphism and personality traits in a Japanese population

Serotonin transporter gene may play a critical role in a regulation of mood and other aspects of mental status. A large number of association studies have investigated a correlation between the polymorphism in the serotonin transporter-linked promoter region (5-HTTLPR) and anxiety-related personality traits. The results, however, have been inconsistent. Heterogeneity of subjects regarding gender, occupation, social-class and other environmental factors, in addition to effects of other genes, might have confounded the results. Here, we studied an association between the 5-HTTLPR polymorphism and personality traits in primarily female (78%) healthy subjects (n=244), who had homogeneous backgrounds regarding ethnicity (Japanese) and occupation. Personality traits of the subjects were assessed with the revised NEO Personality Inventory. No significant association was observed between the polymorphism and neuroticism or other personality traits, in all subjects, all females (n=190) or female nurses (n=159). Thus, our findings provided no evidence for an association between the 5-HTTLPR polymorphism and anxiety-related or other personality traits.

Serum cholesterol, uric acid and cholinesterase in victims of the Tokyo subway sarin poisoning: a relation with post-traumatic stress disorder

Cholesterol and uric acid, which might correlate with steroidogenesis and monoamine functions, may change under emotionally stressful conditions and in mental disturbances. Among anxiety disorders, an increase of serum cholesterol has been observed in panic disorder. However, the issue has not been adequately investigated in other anxiety disorders, including post-traumatic stress disorder (PTSD). The present study investigated serum cholesterols, uric acid and cholinesterase in victims of the Tokyo subway sarin poisoning, 1995, in a series of 5-year follow-ups. Cholinesterase was studied, in relevance with serum lipid changes and symptoms of PTSD, and also in light of a biological effect of sarin. Out of 34 victims, eight developed PTSD and two were currently diagnosed with PTSD using the Clinician-Administered PTSD Scale (CAPS). No significant relationship was observed between PTSD and serum cholesterols or uric acid. Several factors including co-occurrence of other mental disturbances with PTSD, in addition to the limited sample size, might have affected the result. In contrast, serum cholinesterase level was significantly reduced in the victims with the development of PTSD, compared with the matched controls (P<0.02, t-test). This might partly reflect a long-term remnant effect of sarin intoxication, although an effect of the psychological experience could not be totally excluded.

Human leukocyte antigen-A specificities and its relation with season of birth in Japanese patients with schizophrenia

Several studies, including one from Japan, have observed an increase of Human Leukocyte Antigen (HLA)-A24 and A26 in schizophrenia, although others failed to observe the increase. No use of systematic diagnostic criteria and a not-adequately reliable typing technique might have affected the results in the previous studies. We investigated HLA-A specificities in Japanese patients with schizophrenia (DSM-IV), recruited from the same area as in the early Japanese study. A DNA-based technique (polymerase chain reaction-microtiter plate hybridization) was employed. No significant difference was observed in frequencies of any HLA-A specificities between patients and controls, including A24 and A26. No significant association was found between the HLA-A and birth-season in patients. Thus, no evidence was obtained for an association between HLA-A and schizophrenia from the Japanese population.

Molecular genetic studies of schizophrenia: challenges and insights

Schizophrenia (SCZ) is a mental disease that affects approximately 1% of the population with life-long devastating consequences. Based on evidence for a major contribution of genetic factors, a decade of extensive efforts has been dedicated to the search of DNA sequence variations that increase the risk to SCZ. Search for genes in rare multiplex SCZ families with a large number of affected individuals and quasi-Mendelian mode of inheritance using genetic linkage methodology has been one of the favorite strategies in psychiatric genetics. Although several genomic regions were suggested for linkage to SCZ, not a single gene causing or predisposing to SCZ has been identified thus far. Furthermore, it is not clear whether the genes of familial SCZ are also involved in sporadic cases that represent the overwhelming majority of SCZ patients. For sporadic cases, genetic association studies comparing the distribution of allelic frequencies of candidate genes in SCZ patients and controls have been performed but the outcome of such studies has also been quite modest. Several factors such as possible involvement of numerous interactive genes of minor effect, yet unknown environmental effects and diagnostic ambiguities of the disease have made genetic studies in SCZ quite unproductive. In terms of future studies, a genome-wide association search is a promising approach; however, this approach requires genotyping of thousands of genetic markers in large samples. In addition, a detailed analysis of the genes, expression of which changes under the influence of environmental factors, can indicate good candidates for genetic association studies. In this connection, investigations of the epigenetic regulation of genes and not only the DNA sequence variation, may be necessary for complete understanding of the etiopathogenic mechanisms of SCZ.

Zinc homeostasis in the brain of adult rats fed zinc-deficient diet

Zinc concentration and (65)Zn uptake in the brain of rats fed zinc-deficient diet for 12 weeks were examined, based on a previous finding of the impairment of learning behavior by the zinc deprivation. Zinc concentrations in the brain, except for the hippocampal formation, did not decrease significantly in zinc-deficient rats, whereas zinc concentration in the liver of the zinc-deficient rats was approximately half that of control rats. When zinc-deficient rats were subjected to brain autoradiography with (65)Zn, (65)Zn concentration in any brain region of zinc-deficient rats was significantly higher than in control rats 6 days after injection of (65)ZnCl(2). The increase rate of (65)Zn concentration in the brain by the zinc deprivation was approximately 150%, and was similar to those in the liver and serum, suggesting that dietary zinc deprivation may cause a scarcity of zinc in the brain, in addition to the peripheral tissues such as the liver. These results indicate that the adult brain is responsive to dietary zinc deprivation. In the brain of zinc-deficient rats, the increase rate of (65)Zn concentration in the hippocampal formation seemed to be low compared to those in other brain regions. The hippocampal formation may be the most responsive to dietary zinc deprivation in the adult brain. The present finding demonstrates that zinc homeostasis in the brain is altered by chronically dietary zinc deprivation.