Shinsuke Washizuka

Association of mitochondrial complex I subunit gene NDUFV2 at 18p11 with bipolar disorder

Linkage of bipolar disorder with 18p11 has been replicated by several investigators. A nuclear‐encoded mitochondrial complex I subunit gene, NDUFV2, is one of the candidate genes in this locus, since the possible pathophysiological significance of mitochondrial dysfunction in bipolar disorder has been suggested. The objective of our study was to clarify the association between the NDUFV2 gene and bipolar disorder. We performed the real‐time quantitative reverse transcription polymerase chain reaction (RT‐PCR) for NDUFV2 mRNA expression in lymphoblastoid cell lines derived from patients with bipolar disorder and healthy controls. We also screened novel polymorphisms using denaturing high performance liquid chromatography (D‐HPLC) and PCR‐direct sequencing method. Detected five single nucleotide polymorphisms (SNPs) were genotyped. A decrease of the expression level of NDUFV2 gene was found in patients with bipolar I disorder compared with controls (P = 0.006). We also found that the haplotype frequencies of the four polymorphisms in the upstream region of NDUFV2 were significantly different between bipolar disorders and controls (P = 0.0001). Our findings suggest that polymorphisms of the NDUFV2 gene may be one of the genetic risk factors for bipolar disorder.

Mechanisms of altered Ca2+ signalling in transformed lymphoblastoid cells from patients with bipolar disorder.

Altered Ca2+ signalling has been reported in the platelets and lymphoblastoid cells of patients with bipolar disorder. Recent genetic studies have suggested possible pathophysiological roles for mitochondria and endoplasmic reticulum, both of which are essential for the regulation of intracellular Ca2+ signalling. The goal of this study was to determine molecular mechanisms of altered intracellular Ca2+ signalling in bipolar disorder. Lymphoblastoid cell lines were established from patients with bipolar I disorder (n=13) and controls (n=11). Using Ca2+ indicators, cytosolic and mitochondrial Ca2+ responses to the following three reagents were examined: platelet-activating factor; carbonyl cyanide m-chlorophenylhydrazone (CCCP), a mitochondrial uncoupler that abolishes mitochondrial Ca2+ uptake; and thapsigargin, an endoplasmic reticulum Ca2+ pump inhibitor. The 10-5 M thapsigargin-induced cytosolic Ca2+ response was significantly higher in patients with bipolar disorder (p&0.05). Such difference was not seen when the effects of Ca2+ influx from outside the plasma membrane was eliminated using Ca2+-free measurement buffer. On the other hand, response to 10-7 M thapsigargin tended to be higher in patients with bipolar disorder when at the Ca2+-free conditions. CCCP-induced Ca2+ responses differed significantly between mitochondrial DNA 5178/10398 haplotypes (p=0.001) that had been previously reported to be associated with bipolar disorder. These results suggest that all components, i.e. the store-operated calcium channel (SOCC), endoplasmic reticulum, and mitochondria, somehow contribute to the altered Ca2+ signalling in bipolar disorder.

Association of Mitochondrial Complex I Subunit Gene NDUFV2 at 18p11 with Bipolar Disorder in Japanese and the National Institute of Mental Health Pedigrees

BACKGROUND Linkage with 18p11 is one of the replicated findings in molecular genetics of bipolar disorder. Because mitochondrial dysfunction has been suggested in bipolar disorder, NDUFV2 at 18p11, encoding a subunit of the complex I, reduced nicotinamide adenine dinucleotide (NADH)ubiquinone oxidoreductase, is a candidate gene for this disorder. We previously reported that a polymorphism in the upstream region of NDUFV2, -602G> A, was associated with bipolar disorder in Japanese subjects; however, functional significance of -602G> A was not known. METHODS We screened the further upstream region of NDUFV2. We performed a case-control study in Japanese patients with bipolar disorder and control subjects and a transmission disequilibrium test in 104 parent and proband trios of the National Institute of Mental Health (NIMH) Genetics Initiative pedigrees. We also performed the promoter assay to examine functional consequence of the -602G> A polymorphism. RESULTS The -602G> A polymorphism was found to alter the promoter activity. We found that the other haplotype block surrounding -3542G> A was associated with bipolar disorder. The association of the haplotypes consisting of -602G> A and -3542G> A polymorphisms with bipolar disorder was seen both in Japanese case-control samples and NIMH trios. CONCLUSION Together these findings indicate that the polymorphisms in the promoter region of NDUFV2 are a genetic risk factor for bipolar disorder by affecting promoter activity.

Expression of HSPF1 and LIM in the lymphoblastoid cells derived from patients with bipolar disorder and schizophrenia.

AbstractWe have previously reported the altered expressions of HSPF1 and LIM in the lymphoblastoid cell lines (LCLs) derived from Japanese patients with bipolar disorder (bipolar I disorder). The altered expression at the LCL level would be useful for developing diagnostic markers as well as a cellular model for bipolar disorder. In this study, we extended our previous study by measuring their expressions using the following samples: (1) larger number of LCLs from Japanese subjects, (2) LCLs from Caucasian subjects, and (3) LCLs from patients with bipolar II disorder or schizophrenia. We confirmed the increased expression of HSPF1 (P=0.009) and decreased expression of LIM (P=0.001) in the LCLs from patients with Japanese bipolar I disorder. These altered expressions were also observed in those from patients with Japanese bipolar II disorder (P=0.002 for HSPF1 and P=0.072 for LIM). We also found the altered expressions of HSPF1 in LCLs from Caucasian patients with bipolar II disorder (P=0.011) and LIM in those from patients with schizophrenia (P=0.001).

Expression of mitochondrial complex I subunit gene NDUFV2 in the lymphoblastoid cells derived from patients with bipolar disorder and schizophrenia

Several studies have suggested mitochondrial abnormality in bipolar disorder (BD) and schizophrenia (SZ). We have previously reported the decreased expression of mitochondrial complex I subunit gene, NDUFV2 at 18p11, in lymphoblastoid cell lines (LCLs) from Japanese patients with bipolar I disorder (BDI). Recently it was reported that no differences were found in NDUFV2 mRNA levels in LCLs of Caucasian BDI patients compared with controls. In this study, we tested the altered expression of NDUFV2 in extended Japanese LCLs and LCLs from different ethnic groups. Similar tendency was found in the current study compared with our previous study, since decreased expression of NDUFV2 in LCLs from Japanese patients with BDI was found (p=0.03). We also found that the expressions of NDUFV2 were up-regulated in those from patients with Japanese bipolar II disorder (p=0.001) and the mRNA levels of this gene were down-regulated in Caucasian SZ (p=0.000001) compared with controls. Furthermore, we revealed that the mRNA expression of NDUFV2 in LCLs cultured with valproate, one of mood stabilizers, were significantly increased compared with controls (p=0.02). Our study presented the further evidence of biological significance of NDUFV2 in BD and SZ.

Neuroanatomical correlates of attention-deficit-hyperactivity disorder accounting for comorbid oppositional defiant disorder and conduct disorder

Aim:  An increasing number of neuroimaging studies have been conducted to uncover the pathophysiology of attention‐deficit–hyperactivity disorder (ADHD). The findings are inconsistent, however, at least partially due to methodological differences. In the present study voxel‐based morphometry (VBM) was used to evaluate brain morphology in ADHD subjects after taking into account the confounding effect of oppositional defiant disorder (ODD) and conduct disorder (CD) comorbidity.

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.

Possible relationship between mitochondrial DNA polymorphisms and lithium response in bipolar disorder

Although many investigators have been searching for genetic markers to predict lithium response in bipolar disorders, no genetic predictor has been established yet. We previously reported the association of mitochondrial DNA (mtDNA) 5178 and 10398 polymorphisms with bipolar disorder. The objective of this study is to clarify whether these mtDNA polymorphisms can predict response to maintenance lithium treatment in bipolar patients. We examined these polymorphisms and some clinical variables in 54 bipolar patients. A logistic regression analysis was performed and revealed that patients carrying the 10398A polymorphism showed a significantly better response to lithium (p=0.03). Some clinical variables such as sex, age at onset, and rapid cycling also showed a significant association with lithium response in univariate analysis (chi2 test, p&0.05). Our findings suggest that the mtDNA 10398 polymorphism might be related to maintenance lithium treatment response.

No association of mutations and mRNA expression of WFS1/wolframin with bipolar disorder in humans

Association of WFS1 (wolframin) and bipolar disorder has been suggested by psychiatric manifestations in patients or non-symptomatic carriers of Wolfram disease and linkage of bipolar disorder with 4p16, the locus of WFS1. Five studies of WFS1 in bipolar disorder did not support this association, although possible association of several missense mutations has not been excluded yet. In this study, four such mutations were genotyped in 184 patients with bipolar disorder and 207 controls. None had the A559T and A602V mutations, and no association of G576S and H611R with bipolar disorder was found. We also quantified the expression levels of WFS1 mRNA in the postmortem brains of patients with bipolar disorder, depression, schizophrenia, and controls. There was no significant difference of the expression levels. These results did not support the pathophysiological significance of WFS1 in bipolar disorder.

Mitochondrial DNA sequence analysis of patients with ‘atypical psychosis’

Abstract  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’.