Norio Ozaki

Association of structural polymorphisms in the human period3 gene with delayed sleep phase syndrome

Recent progress in biological clock research has facilitated genetic analysis of circadian rhythm sleep disorders, such as delayed sleep phase syndrome (DSPS) and non‐24‐h sleep–wake syndrome (N‐24). We analyzed the human period3 (hPer3) gene, one of the human homologs of the Drosophila clock‐gene period (Per), as a possible candidate for rhythm disorder susceptibility. All of the coding exons in the hPer3 gene were screened for polymorphisms by a PCR‐based strategy using genomic DNA samples from sleep disorder patients and control subjects. We identified six sequence variations with amino acid changes, of which five were common and predicted four haplotypes of the hPer3 gene. One of the haplotypes was significantly associated with DSPS (Bonferronis corrected P = 0.037; odds ratio = 7.79; 95% CI 1.59–38.3) in our study population. Our results suggest that structural polymorphisms in the hPer3 gene may be implicated in the pathogenesis of DSPS.

Serotonin transporter missense mutation associated with a complex neuropsychiatric phenotype

Two common serotonin transporter (SERT) untranslated region gene variants have been intensively studied, but remain inconclusively linked to depression and other neuropsychiatric disorders. We now report an uncommon coding region SERT mutation, Ile425Val, in two unrelated families with OCD and other serotonin-related disorders. Six of the seven family members with this mutation had OCD (n=5) or obsessive-compulsive personality disorder (n=1) and some also met diagnostic criteria for multiple other disorders (Aspergers syndrome, social phobia, anorexia nervosa, tic disorder and alcohol and other substance abuse/dependence). The four most clinically affected individuals—the two probands and their two slbs—had the I425V SERT gene gain-of-function mutation and were also homozygous for 5′-UTR SERT gene variant with greater transcriptional efficacy.

DNA Methylation Profiles of the Brain-Derived Neurotrophic Factor (BDNF) Gene as a Potent Diagnostic Biomarker in Major Depression

Major depression, because of its recurring and life-threatening nature, is one of the top 10 diseases for global disease burden. Major depression is still diagnosed on the basis of clinical symptoms in patients. The search for specific biological markers is of great importance to advance the method of diagnosis for depression. We examined the methylation profile of 2 CpG islands (I and IV) at the promoters of the brain-derived neurotrophic factor (BDNF) gene, which is well known to be involved in the pathophysiology of depression. We analyzed genomic DNA from peripheral blood of 20 Japanese patients with major depression and 18 healthy controls to identify an appropriate epigenetic biomarker to aid in the establishment of an objective system for the diagnosis of depression. Methylation rates at each CpG unit was measured using a MassArray® system (SEQUENOM), and 2-dimensional hierarchical clustering analyses were undertaken to determine the validity of these methylation profiles as a diagnostic biomarker. Analyses of the dendrogram from methylation profiles of CpG I, but not IV, demonstrated that classification of healthy controls and patients at the first branch completely matched the clinical diagnosis. Despite the small number of subjects, our results indicate that classification based on the DNA methylation profiles of CpG I of the BDNF gene may be a valuable diagnostic biomarker for major depression.

Adolescent Stress–Induced Epigenetic Control of Dopaminergic Neurons via Glucocorticoids

Defeat, Distress, and Glucocorticoids Understanding how individuals control emotions and cope with stressful events is a major clinical concern and of importance for the treatment of psychiatric illnesses (see the Perspective by McEwen). Barik et al. (p. 332) discovered that aggressive defeat stress in mice caused glucocortioid release and increased activity in the dopamine system. Deleting the glucocorticoid receptors in dopaminoceptive neurons completely prevented the social avoidance that usually follows aggressive defeat. How the combination of genetic factors and environmental stressors during adolescence determines adult behavior and how their disturbance results in neuropsychiatric disorders is poorly understood. Niwa et al. (p. 335) found that isolation stress during adolescence, which does not cause any long-lasting changes in wild-type mice, induced significant neurochemical and behavioral alterations in mutant mice expressing a dominant-negative variant of the disrupted in schizophrenia 1 gene under the control of the prion protein promoter. These deficits could be reversed by a glucocorticoid receptor antagonist. Genetically susceptible mice isolated during adolescence can subsequently present schizophrenia-like symptoms. [Also see Perspective by McEwen] Environmental stressors during childhood and adolescence influence postnatal brain maturation and human behavioral patterns in adulthood. Accordingly, excess stressors result in adult-onset neuropsychiatric disorders. We describe an underlying mechanism in which glucocorticoids link adolescent stressors to epigenetic controls in neurons. In a mouse model of this phenomenon, a mild isolation stress affects the mesocortical projection of dopaminergic neurons in which DNA hypermethylation of the tyrosine hydroxylase gene is elicited, but only when combined with a relevant genetic risk for neuropsychiatric disorders. These molecular changes are associated with several neurochemical and behavioral deficits that occur in this mouse model, all of which are blocked by a glucocorticoid receptor antagonist. The biology and phenotypes of the mouse models resemble those of psychotic depression, a common and debilitating psychiatric disease.

Aberrant DNA methylation associated with bipolar disorder identified from discordant monozygotic twins

To search DNA methylation difference between monozygotic twins discordant for bipolar disorder, we applied a comprehensive genome scan method, methylation-sensitive representational difference analysis (MS-RDA) to lymphoblastoid cells derived from the twins. MS-RDA isolated 10 DNA fragments derived from 5′ region of known genes/ESTs. Among these 10 regions, four regions showed DNA methylation differences between bipolar twin and control co-twin confirmed by bisulfite sequencing. We performed a case–control study of DNA methylation status of these four regions by pyrosequencing. Two regions, upstream regions of spermine synthase (SMS) and peptidylprolyl isomerase E-like (PPIEL) (CN265253), showed aberrant DNA methylation status in bipolar disorder. SMS, a gene on X chromosome, showed significantly higher DNA methylation level in female patients with bipolar disorder compared with control females. However, there was no difference of mRNA expression. In PPIEL, DNA methylation level was significantly lower in patients with bipolar II disorder than in controls. The expression level of PPIEL was significantly higher in bipolar II disorder than in controls. We found strong inverse correlation between gene expression and DNA methylation levels of PPIEL. These results suggest that altered DNA methylation statuses of PPIEL might have some significance in pathophysiology of bipolar disorder.

Role of serotonin transporter promoter repeat length polymorphism (5-HTTLPR) in seasonality and seasonal affective disorder

Seasonal variations in mood and behavior (seasonality) and seasonal affective disorder (SAD) have been attributed to seasonal fluctuations in brain serotonin (5-HT).1 the short (s), as opposed to the long (l), allele of the 5-HT transporter linked polymorphism (5-HTTLPR) has been associated with neuroticism and depression.2,3 We hypothesized that this short allele would also be associated with SAD and with higher levels of seasonality. Ninety-seven SAD patients and 71 non-seasonal healthy controls with low seasonality levels were genotyped for 5-HTTLPR and compared statistically. Patients with SAD were less likely to have the l/l genotype (27.8% vs 47.9%; P < 0.01) and more likely to have the s allele (44.8% vs 32.4%; P < 0.02) as compared to controls. the three 5-httlpr genotypes were also differentially distributed in patients and controls (P < 0.03). the sad patients with the l/l genotype had a lower mean seasonality score than did patients with the other two genotypes (mean ± s.d. = 15.3 ± 2.8 vs 17.1 ± 3.4 respectively; P < 0.02). the 5-httlpr short allele contributes to the trait of seasonality and is a risk factor for sad, providing further evidence for a relationship between genetic variation in the 5-ht transporter (5-htt) and behavior.

Genome-wide association study of schizophrenia in a Japanese population.

BACKGROUND Genome-wide association studies have detected a small number of weak but strongly supported schizophrenia risk alleles. Moreover, a substantial polygenic component to the disorder consisting of a large number of such alleles has been reported by the International Schizophrenia Consortium. METHOD We report a Japanese genome-wide association study of schizophrenia comprising 575 cases and 564 controls. We attempted to replicate 97 markers, representing a nonredundant panel of markers derived mainly from the top 150 findings, in up to three data sets totaling 1990 cases and 5389 controls. We then attempted to replicate the observation of a polygenic component to the disorder in the Japanese and to determine whether this overlaps that seen in UK populations. RESULTS Single-locus analysis did not reveal genome-wide support for any locus in the genome-wide association study sample (best p = 6.2 × 10(-6)) or in the complete data set in which the best supported locus was SULT6B1 (rs11895771: p = 3.7 × 10(-5) in the meta-analysis). Of loci previously supported by genome-wide association studies, we obtained in the Japanese support for NOTCH4 (rs2071287: p(meta) = 5.1 × 10(-5)). Using the approach reported by the International Schizophrenia Consortium, we replicated the observation of a polygenic component to schizophrenia within the Japanese population (p = .005). Our trans Japan-UK analysis of schizophrenia also revealed a significant correlation (best p = 7.0 × 10(-5)) in the polygenic component across populations. CONCLUSIONS These results indicate a shared polygenic risk of schizophrenia between Japanese and Caucasian samples, although we did not detect unequivocal evidence for a novel susceptibility gene for schizophrenia.

Evaluating the state dependency of the Temperament and Character Inventory dimensions in patients with major depression: a methodological contribution.

BACKGROUND Little is known as to whether or not the seven personality dimensions of Cloningers theory, particularly the three character dimensions newly included in the theory, are independent of the states of depression. METHODS One hundred and eight patients with major depression filled out the Temperament and Character Inventory (TCI) before and after a 16-week antidepressant treatment. RESULTS The level of depression, as assessed by the Hamilton Rating Scale for Depression, was correlated positively to the harm avoidance score and negatively to the self-directedness and cooperativeness scores. During the treatment, the scores on these three dimensions significantly changed toward normal values in treatment-responders, but were stable in treatment-nonresponders. The changes in these dimensions were significantly explained by the change in the depression severity during treatment. Scores on novelty seeking, reward dependence, persistence, and self-transcendence were not correlated significantly to the level of depression and did not change significantly during the treatment in either treatment-responders or nonresponders. LIMITATIONS The changes in the TCI scores during treatment in this study may reflect a non-specific tendency for the scores to change on retest. CONCLUSIONS The results suggest that a depressive state can significantly affect assessments of harm avoidance, self-directedness, and cooperativeness in major depression. The administration of the TCI during a depressive episode may elevate the HA score, and may lower the SD and C scores. These findings highlight the importance of considering the state of depression before drawing conclusions about the TCI personality traits, when a patient with major depression is still experiencing a depressive episode.

Association of AKT1 with schizophrenia confirmed in a Japanese population

BACKGROUND Abnormality of the V-akt murine thymoma viral oncogene homologue 1 (AKT1) may be a predisposing factor in schizophrenia. Recent evidence supporting this hypothesis showed decreased AKT1 protein levels in patients with schizophrenia and significant association of AKT1 haplotypes according to the transmission disequilibrium test. METHODS We provide the first replication of this evidence using a relatively large case-control sample (507 Japanese schizophrenia and 437 control subjects). We genotyped five single nucleotide polymorphisms (SNPs) from the original study and one additional SNP. RESULTS We found a positive association with an SNP (SNP5) different from the original studys findings (SNP3) and also significance in the haplotypes constructed from the combination of SNP5. Linkage disequilibrium around SNP5 was complex and may produce this positive association. CONCLUSIONS Our study provides support for the theory that AKT1 is a susceptibility gene for Japanese schizophrenia. Fine linkage disequilibrium mapping is required for a conclusive result.

Pituitary adenylate cyclase-activating polypeptide is associated with schizophrenia

Pituitary adenylate cyclase-activating polypeptide (PACAP, ADCYAP1: adenylate cyclase-activating polypeptide 1), a neuropeptide with neurotransmission modulating activity, is a promising schizophrenia candidate gene. Here, we provide evidence that genetic variants of the genes encoding PACAP and its receptor, PAC1, are associated with schizophrenia. We studied the effects of the associated polymorphism in the PACAP gene on neurobiological traits related to risk for schizophrenia. This allele of the PACAP gene, which is overrepresented in schizophrenia patients, was associated with reduced hippocampal volume and poorer memory performance. Abnormal behaviors in PACAP knockout mice, including elevated locomotor activity and deficits in prepulse inhibition of the startle response, were reversed by treatment with an atypical antipsychotic, risperidone. These convergent data suggest that alterations in PACAP signaling might contribute to the pathogenesis of schizophrenia.