Schizophrenia and affective disorders--cosegregation with a translocation at chromosome 1q42 that directly disrupts brain-expressed genes: clinical and P300 findings in a family

Gene models of schizophrenia: DISC1 mouse models

Disrupted in Schizophrenia-1 (DISC1) is one of the most likely susceptibility genes for schizophrenia (SZ). DISC1 is being established as a hub protein with various functions in the pre- and postnatal development of the nervous system. Since generation of a knockout (KO) mouse has proved challenging, various alternative approaches have been taken. Seven DISC1 mouse models have been described to date. All of them display neuroanatomical and behavioral abnormalities relevant to SZ, although most of them have not been fully characterized yet, requiring further analysis. NRG1 and ErbB4, also highly promising susceptibility genes for SZ, share many features with DISC1. They are involved in various aspects of pre- and postnatal neurodevelopment. The NRG1 and ErbB4 mouse models also display neuroanatomical and behavioral abnormalities similar to the DISC1 mouse models. In the future, four main directions need further study. First, further characterization of the seven DISC1 mouse models, especially in light of basic research findings. Second, more extensive employment of the inducible models. Third, generation of a DISC1 KO. Fourth, combination of the DISC1 mouse models with other risk factors: crossing with other genetic models such as NRG1/ErbB4 mutants and exposure to environmental risk factors.

Additive effect of NRG1 and DISC1 genes on lateral ventricle enlargement in first episode schizophrenia

Neuregulin 1 (NRG1) and Disrupted-in-schizophrenia (DISC1) genes, which are candidate genes for schizophrenia, are implicated in brain development. We have previously reported an association between the T allele of the rs6994992 SNP within NRG1 gene and lateral ventricle (LV) enlargement in first-episode schizophrenia patients. Moreover, transgenic mice with mutant DISC1 have also been reported as showing LV enlargement. In this study, we examined the possible interactive effects of NRG1 and DISC1 on brain volumes in a sample of first-episode schizophrenia patients. Ninety-one patients experiencing their first episode of schizophrenia underwent genotyping of three SNPs within DISC1 and structural brain MRI. These results were combined with our previously reported genotypes on three SNPs within NRG1. The T/T genotype of rs2793092 SNP in DISC1 was significantly associated with increased LV volume. However, taking into account the rs6994992 SNP in the NRG1 gene, which was also associated with LV volume in a previous study, the DISC1 SNP only predicted LV enlargement among those patients carrying the T allele in the NRG1 SNP. Those patients with the "at risk" allelic combinations in both genes had LV volumes which were 48% greater than those with none of the allelic combinations. Our findings suggest that NRG1 and DISC1 genes may be associated with brain abnormalities in schizophrenia through their influence on related pathways of brain development.

Understanding the role of DISC1 in psychiatric disease and during normal development

The biology of schizophrenia is complex with multiple hypotheses (dopamine, glutamate, neurodevelopmental) well supported to underlie the disease. Pathways centered on the risk factor "disrupted in schizophrenia 1" (DISC1) may be able to explain and unite these disparate hypotheses and will be the topic of this mini-symposium preview. Nearly a decade after its original identification at the center of a translocation breakpoint in a large Scottish family that was associated with major psychiatric disease, we are starting to obtain credible insights into its function and role in disease etiology. This preview will highlight a number of exciting areas of current DISC1 research that are revealing roles for DISC1 during normal brain development and also in the disease state. Together these different threads will provide a timely and exciting overview of the DISC1 field and its potential in furthering our understanding of psychiatric diseases and in developing new therapies.

DISC1 regulates new neuron development in the adult brain via modulation of AKT-mTOR signaling through KIAA1212

Disrupted-in-schizophrenia 1 (DISC1), a susceptibility gene for major mental illnesses, regulates multiple aspects of embryonic and adult neurogenesis. Here, we show that DISC1 suppression in newborn neurons of the adult hippocampus leads to overactivated signaling of AKT, another schizophrenia susceptibility gene. Mechanistically, DISC1 directly interacts with KIAA1212, an AKT binding partner that enhances AKT signaling in the absence of DISC1, and DISC1 binding to KIAA1212 prevents AKT activation in vitro. Functionally, multiple genetic manipulations to enhance AKT signaling in adult-born neurons in vivo exhibit similar defects as DISC1 suppression in neuronal development that can be rescued by pharmacological inhibition of mammalian target of rapamycin (mTOR), an AKT downstream effector. Our study identifies the AKT-mTOR signaling pathway as a critical DISC1 target in regulating neuronal development and provides a framework for understanding how multiple susceptibility genes may functionally converge onto a common pathway in contributing to the etiology of certain psychiatric disorders.

Association studies and gene expression analyses of the DISC1-interacting molecules, pericentrin 2 (PCNT2) and DISC1-binding zinc finger protein (DBZ), with schizophrenia and with bipolar disorder

Disrupted-in-Schizophrenia 1 (DISC1) and its molecular cascade have been implicated in the pathophysiology of major psychoses. Previously, we identified pericentrin 2 (PCNT2) and DISC1-binding zinc finger protein (DBZ) as binding partners of DISC1; further, we observed elevated expression of PCNT2 in the postmortem brains and in the lymphocytes of bipolar disorder patients, compared to controls. Here, we examined the association of PCNT2 with schizophrenia in a case-control study of Japanese cohorts. We also examined the association of DBZ with schizophrenia and with bipolar disorder, and compared the mRNA levels of DBZ in the postmortem brains of schizophrenia, bipolar and control samples. DNA from 180 schizophrenia patients 201 controls were used for the association study of PCNT2 and DBZ with schizophrenia. Association of DBZ with bipolar disorder was examined in DNA from 238 bipolar patients and 240 age- and gender-matched controls. We observed significant allelic and genotypic associations of the PCNT2 SNPs, rs2249057, rs2268524, and rs2073380 (Ser/Arg) with schizophrenia; the association of rs2249057 (P = 0.002) withstand multiple testing correction. Several two SNP- and three SNP-haplotypes showed significant associations; the associations of haplotypes involving rs2249057 withstand multiple testing correction. No associations were observed for DBZ with schizophrenia or with bipolar disorder; further, there was no significant difference between the DBZ mRNA levels of control, schizophrenia and bipolar postmortem brains. We suggest a possible role of PCNT2 in the pathogenesis of schizophrenia. Abnormalities of PCNT2, the centrosomal protein essential for microtubule organization, may be suggested to lead to neurodevelopmental abnormalities.

Genetic association and post-mortem brain mRNA analysis of DISC1 and related genes in schizophrenia

Convergent evidence from genetic linkage, genetic association and biological studies implicates the Disrupted in schizophrenia 1 (DISC1) gene in the etiology and pathophysiology of schizophrenia. We conducted genetic association studies in matched case-control and family sample sets (N=117 families; N=210 case-control pairs), testing polymorphisms across DISC1 and DISC1 interacting genes: LIS1, NUDEL, FEZ1 and PDE4B. We found that DISC1 variants, particularly in the exon 9/intron 9/intron 10 region of the gene, may be associated with risk for schizophrenia in our sample population. There was no strong evidence for association with LIS1, NUDEL, FEZ1 and PDE4B. Gene-gene interaction analyses and mRNA quantification in post-mortem brains from schizophrenia patients and control subjects did not reveal significant differences.

Advancing a functional genomics for schizophrenia: psychopathological and cognitive phenotypes in mutants with gene disruption

Schizophrenia is a complex, heritable psychotic disorder in which numerous genes and environmental adversities appear to interact in determining disease phenotype. In addition to genes regulating putative pathophysiological mechanisms, a new generation of molecular studies has indicated numerous candidate genes to be associated with risk for schizophrenia. The present review focuses on studies in mice mutant for genes associated with putative pathophysiological mechanisms and candidate risk genes for the disorder. It seeks to evaluate the extent to which each mutation of a schizophrenia-related gene accurately models multiple aspects of the schizophrenia phenotype or more circumscribed, distinct endophenotypes in terms of psychopathology and pathobiology; in doing so, it places particular emphasis on positive symptoms, negative symptoms and cognitive dysfunction. To further this goal, it juxtaposes continually evolving mutant genomics with emergent clinical genomic studies. Opportunities and challenges associated with the use of such mutants, including diagnostic specificity and the translational barrier associated with modelling schizophrenia, are discussed. The potential value of genetic models for exploring gene-gene and gene-environment interactions relating to schizophrenia is highlighted. Elucidation of the contribution of genetic variation to specific symptom clusters and underlying aspects of pathobiology will have important implications for identifying treatments that target distinct domains of psychopathology and dysfunction on an individual patient basis.

Oligomer assembly of the C-terminal DISC1 domain (640-854) is controlled by self-association motifs and disease-associated polymorphism S704C

Genetic studies have established a role of disrupted-in-schizophrenia-1 (DISC1) in chronic mental diseases (CMD). Limited experimental data are available on the domain structure of the DISC1 protein although multiple interaction partners are known including a self-association domain within the middle part of DISC1 (residues 403-504). The DISC1 C-terminal domain is deleted in the original Scottish pedigree where DISC1 harbors two coiled-coil domains and disease-associated polymorphisms at 607 and 704, as well as the important nuclear distribution element-like 1 (NDEL1) binding site at residues 802-839. Here, we performed mutagenesis studies of the C-terminal domain of the DISC1 protein (residues 640-854) and analyzed the expressed constructs by biochemical and biophysical methods. We identified novel DISC1 self-association motifs and the necessity of their concerted action for orderly assembly: the region 765-854 comprising a coiled-coil domain is a dimerization domain and the region 668-747 an oligomerization domain; dimerization was found to be a prerequisite for orderly assembly of oligomers. Consistent with this, disease-associated polymorphism C704 displayed a slightly higher oligomerization propensity. The heterogeneity of DISC1 multimers in vitro was confirmed with a monoclonal antibody binding exclusively to HMW multimers. We also identified C-terminal DISC1 fragments in human brains, suggesting that C-terminal fragments could carry out DISC1-dependent functions. When the DISC1 C-terminal domain was transiently expressed in cells, it assembled into a range of soluble and insoluble multimers with distinct fractions selectively binding NDEL1, indicating functionality. Our results suggest that assembly of the C-terminal domain is controlled by distinct domains including the disease-associated polymorphism 704 and is functional in vivo.

Further immunohistochemical characterization of BRD1 a new susceptibility gene for schizophrenia and bipolar affective disorder

We have recently shown that the gene BRD1 is associated with schizophrenia and bipolar affective disorder and that the BRD1 protein (BRD1) which is expressed in neurons may occur in a short and a long variant. The aim of the study was to generate polyclonal antibodies against new BRD1 epitopes enabling discrimination between the long and short BRD1 variants, and elucidate the BRD1 distribution in several human tissues, including the CNS. Polyclonal rabbit antibodies were raised against three different BRD1 epitopes. One (67) was specific for the long BRD1 variant, whereas the two others (63/64 and 65/66) like the original monoclonal mouse antibody (K22) were predicted to stain both variants. Immunohistochemical staining procedures were subsequently performed on paraffin-embedded human cerebral cortex and microarray slides containing 30 different human tissues. Western blotting confirmed the predicted specificity of the developed antibodies. K22, 63/64 and 65/66 displayed a similar neuronal staining pattern characterized by a distinct but weak nuclear staining, while the surrounding cytoplasm and proximal dendrites were more intensely stained. Interestingly, staining with 67 generated in contrast primarily an intense nuclear staining. The new antibodies resulted, furthermore, in a prominent neuroglial reaction characterized by staining of cell bodies, nuclei and glial processes. The tissue microarray analysis revealed that BRD1 was widely distributed in human tissues. The particular expression profile, e.g., the degree of nuclear and/or cytoplasmatic staining, seemed, however, to be highly tissue dependent. These results suggest a general role of BRD1 in the cell and stress that the two BRD1 variants may play different roles in the etiology of psychiatric disease.

DISC1 splice variants are upregulated in schizophrenia and associated with risk polymorphisms

Disrupted-In-Schizophrenia-1 (DISC1) is a promising susceptibility gene for major mental illness, but the mechanism of the clinical association is unknown. We searched for DISC1 transcripts in adult and fetal human brain and tested whether their expression is altered in patients with schizophrenia and is associated with genetic variation in DISC1. Many alternatively spliced transcripts were identified, including groups lacking exon 3 (Delta3), exons 7 and 8 (Delta7Delta8), an exon 3 insertion variant (extra short variant-1, Esv1), and intergenic splicing between TSNAX and DISC1. Isoforms Delta7Delta8, Esv1, and Delta3, which encode truncated DISC1 proteins, were expressed more abundantly during fetal development than during postnatal ages, and their expression was higher in the hippocampus of patients with schizophrenia. Schizophrenia risk-associated polymorphisms [non-synonymous SNPs rs821616 (Cys704Ser) and rs6675281 (Leu607Phe), and rs821597] were associated with the expression of Delta3 and Delta7Delta8. Moreover, the same allele at rs6675281, which predicted higher expression of these transcripts in the hippocampus, was associated with higher expression of DISC1Delta7Delta8 in lymphoblasts in an independent sample. Our results implicate a molecular mechanism of genetic risk associated with DISC1 involving specific alterations in gene processing.

Mood-incongruent psychosis in bipolar disorder: conditional linkage analysis shows genome-wide suggestive linkage at 1q32.3, 7p13 and 20q13.31

OBJECTIVE

The majority of research into functional psychosis has proceeded under the assumption that schizophrenia and bipolar disorder are distinct entities with separate underlying disease processes and treatments. This view has been increasingly challenged in both clinical and genetic studies. Findings in recent association studies at two specific genes suggest that the occurrence of mood-incongruent psychotic features may indicate a relatively homogeneous subset of the bipolar phenotype. We examined this hypothesis.

METHODS

Caucasian affected individuals were ascertained from Europe (the United Kingdom, the Republic of Ireland, Germany, Italy and Andalusia). Consensus best-estimate diagnoses were assigned by two independent raters according to all available information. There was no cross-site evaluation of inter-rater reliability. Families multiply affected by bipolar spectrum mood disorder were selected, comprising 383 affected relative pairs. Individuals were considered to be affected if they were diagnosed with DSM-IV bipolar I disorder or schizoaffective disorder, bipolar type. Multipoint, affected relative pair covariate linkage analysis was performed.

RESULTS

Significant familiality of incongruent psychosis was observed [intra-class correlation coefficient (ICC) = 0.309; p = 0.001, one-tail]. Covariate linkage analysis provided three regions with genome-wide suggestive evidence for linkage on chromosomes 1q32.3 (LOD = 4.15, expected 0.12 times per genome scan), 7p13 (LOD = 3.32) and 20q13.31 (LOD = 2.98). No region in our analysis met criteria for genome-wide significance.

CONCLUSION

Our results provide molecular support for the hypothesis that genes may exist for specific forms of bipolar illness, dependent on the presence or absence of incongruent psychosis. Our findings suggest that researchers should take account of mood-congruence/incongruence of psychotic features in studies of bipolar disorder.

Neurodevelopmental mechanisms of schizophrenia: understanding disturbed postnatal brain maturation through neuregulin-1-ErbB4 and DISC1

Schizophrenia (SZ) is primarily an adult psychiatric disorder in which disturbances caused by susceptibility genes and environmental insults during early neurodevelopment initiate neurophysiological changes over a long time course, culminating in the onset of full-blown disease nearly two decades later. Aberrant postnatal brain maturation is an essential mechanism underlying the disease. Currently, symptoms of SZ are treated with anti-psychotic medications that have variable efficacy and severe side effects. There has been much interest in the prodromal phase and the possibility of preventing SZ by interfering with the aberrant postnatal brain maturation associated with this disorder. Thus, it is crucial to understand the mechanisms that underlie the long-term progression to full disease manifestation to identify the best targets and approaches towards this goal. We believe that studies of certain SZ genetic susceptibility factors with neurodevelopmental implications will be key tools in this task. Accumulating evidence suggests that neuregulin-1 (NRG1) and disrupted-in-schizophrenia-1 (DISC1) are probably functionally convergent and play key roles in brain development. We provide an update on the role of these emerging concepts in understanding the complex time course of SZ from early neurodevelopmental disturbances to later onset and suggest ways of testing these in the future.

DISC1 association, heterogeneity and interplay in schizophrenia and bipolar disorder

Disrupted in schizophrenia 1 (DISC1) has been associated with risk of schizophrenia, schizoaffective disorder, bipolar disorder, major depression, autism and Asperger syndrome, but apart from in the original translocation family, true causal variants have yet to be confirmed. Here we report a harmonized association study for DISC1 in European cohorts of schizophrenia and bipolar disorder. We identify regions of significant association, demonstrate allele frequency heterogeneity and provide preliminary evidence for modifying interplay between variants. Whereas no associations survived permutation analysis in the combined data set, significant corrected associations were observed for bipolar disorder at rs1538979 in the Finnish cohorts (uncorrected P=0.00020; corrected P=0.016; odds ratio=2.73+/-95% confidence interval (CI) 1.42-5.27) and at rs821577 in the London cohort (uncorrected P=0.00070; corrected P=0.040; odds ratio=1.64+/-95% CI 1.23-2.19). The rs821577 single nucleotide polymorphism (SNP) showed evidence for increased risk within the combined European cohorts (odds ratio=1.27+/-95% CI 1.07-1.51), even though significant corrected association was not detected (uncorrected P=0.0058; corrected P=0.28). After conditioning the European data set on the two risk alleles, reanalysis revealed a third significant SNP association (uncorrected P=0.00050; corrected P=0.025). This SNP showed evidence for interplay, either increasing or decreasing risk, dependent upon the presence or absence of rs1538979 or rs821577. These findings provide further support for the role of DISC1 in psychiatric illness and demonstrate the presence of locus heterogeneity, with the effect that clinically relevant genetic variants may go undetected by standard analysis of combined cohorts.

Schizophrenia: from the brain to peripheral markers. A consensus paper of the WFSBP task force on biological markers

Objective. The phenotypic complexity, together with the multifarious nature of the so-called "schizophrenic psychoses", limits our ability to form a simple and logical biologically based hypothesis for the disease group. Biological markers are defined as biochemical, physiological or anatomical traits that are specific to particular conditions. An important aim of biomarker discovery is the detection of disease correlates that can be used as diagnostic tools. Method. A selective review of the WFSBP Task Force on Biological Markers in schizophrenia is provided from the central nervous system to phenotypes, functional brain systems, chromosomal loci with potential genetic markers to the peripheral systems. Results. A number of biological measures have been proposed to be correlated with schizophrenia. At present, not a single biological trait in schizophrenia is available which achieves sufficient specificity, selectivity and is based on causal pathology and predictive validity to be recommended as diagnostic marker. Conclusions. With the emergence of new technologies and rigorous phenotypic subclassification the identification of genetic bases and assessment of dynamic disease related alterations will hopefully come to a new stage in the complex field of psychiatric research.

Construction of balanced translocation t(1;11)(q42.1;q14.3) probe and screening application in genomic samples in Taiwan

The disrupted-in-schizophrenia 1 (DISC1) gene is a candidate gene in schizophrenia. The balanced t(1;11)(q42.1;q14.3) translocation with a breakpoint between exons 8 and 9 of DISC1 has been found to be co-segregated with psychosis in a Scottish family. To examine whether the t(1;11)(q42.1;q14.3) translocation exists in Taiwanese samples, we constructed a plasmid probe that carried the two DNA fragments of chromosome 1 (738 bp) and chromosome 11 (719 bp) that covered the breakpoint. This probe was validated using a derived DNA gift from the translocation carrier of the Scottish family. We screened genomic DNA samples from 619 subjects (507 cases and 112 controls). None of the subjects showed the designed polymerase chain reaction (PCR) product detected by the probe. We concluded that the significant association between schizophrenia and the DISC1 gene in the Taiwanese sample was not caused by balance translocation, but rather by polymorphic variations of the gene to be detected.

Proteomic analysis reveals novel binding partners of dysbindin, a schizophrenia-related protein

Schizophrenia is a complex mental disorder with fairly high level of heritability. Dystrobrevin binding protein 1, a gene encoding dysbindin protein, is a susceptibility gene for schizophrenia that was identified by family-based association analysis. Recent studies revealed that dysbindin is involved in the exocytosis and/or formation of synaptic vesicles. However, the molecular function of dysbindin in synaptic transmission is largely unknown. To investigate the signaling pathway in which dysbindin is involved, we isolated dysbindin-interacting molecules from rat brain lysate by combining ammonium sulfate precipitation and dysbindin-affinity column chromatography, and identified dysbindin-interacting proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and liquid chromatography-tandem mass spectrometry. Proteins involved in protein localization process, including Munc18-1, were identified as dysbindin-interacting proteins. Munc18-1 was co-immunoprecipitated with dysbindin from rat brain lysate, and directly interacted with dysbindin in vitro. In primary cultured rat hippocampal neurons, a part of dysbindin was co-localized with Munc18-1 at pre-synaptic terminals. Our result suggests a role for dysbindin in synaptic vesicle exocytosis via interaction with Munc18-1.

Association between genes of Disrupted in schizophrenia 1 (DISC1) interactors and schizophrenia supports the role of the DISC1 pathway in the etiology of major mental illnesses

BACKGROUND

Disrupted in Schizophrenia 1 (DISC1) is currently one of the most interesting candidate genes for major mental illness, having been demonstrated to associate with schizophrenia, bipolar disorder, major depression, autism, and Asperger's syndrome. We have previously reported a DISC1 haplotype, HEP3, and an NDE1 spanning tag haplotype to associate to schizophrenia in Finnish schizophrenia families. Because both DISC1 and NDE1 display association in our study sample, we hypothesized that other genes interacting with DISC1 might also have a role in the etiology of schizophrenia.

METHODS

We selected 11 additional genes encoding components of the "DISC1 pathway" and studied these in our study sample of 476 families including 1857 genotyped individuals. We performed single nucleotide polymorphism (SNP) and haplotype association analyses in two independent sets of families. For markers and haplotypes found to be consistently associated in both sets, the overall significance was tested with the combined set of families.

RESULTS

We identified three SNPs to be associated with schizophrenia in PDE4D (rs1120303, p = .021), PDE4B (rs7412571, p = .018), and NDEL1 (rs17806986, p = .0038). Greater significance was observed with allelic haplotypes of PDE4D (p = .00084), PDE4B (p = .0022 and p = .029), and NDEL1 (p = .0027) that increased or decreased schizophrenia susceptibility.

CONCLUSIONS

Our findings with other converging lines of evidence support the underlying importance of DISC1-related molecular pathways in the etiology of schizophrenia and other major mental illnesses.

Genetics of psychosis; insights from views across the genome

The major psychotic illnesses, schizophrenia and bipolar disorder (BD), are among the most heritable common disorders, but finding specific susceptibility genes for them has not been straightforward. The reasons are widely assumed to include lack of valid phenotypic definition, absence of good theories of pathophysiology for candidate gene studies, and the involvement of many genes, each making small contributions to population risk. Within the last year or so, a number of genome wide association (GWAS) of schizophrenia and BD have been published. These have produced stronger evidence for association to specific risk loci than have earlier studies, specifically for the zinc finger binding protein 804A (ZNF804A) locus in schizophrenia and for the calcium channel, voltage-dependent, L type, alpha 1C subunit (CACNA1C) and ankyrin 3, node of Ranvier (ANK3) loci in bipolar disorder. The ZNF804A and CACNA1C loci appear to influence risk for both disorders, a finding that supports the hypothesis that schizophrenia and BD are not aetiologically distinct. In the case of schizophrenia, a number of rare copy number variants have also been detected that have fairly large effect sizes on disease risk, and that additionally influence risk of autism, mental retardation, and other neurodevelopmental disorders. The existing findings point to some likely pathophysiological mechanisms but also challenge current concepts of disease classification. They also provide grounds for optimism that larger studies will reveal more about the origins of these disorders, although currently, very little of the genetic risk of either disorder is explained.

Modeling cognitive endophenotypes of schizophrenia in mice

Schizophrenia is a complex mental disorder that is still characterized by its symptoms rather than by biological markers because we have only a limited knowledge of its underlying molecular basis. In the past two decades, however, technical advances in genetics and brain imaging have provided new insights into the biology of the disease. Based on these advances we are now in a position to develop animal models that can be used to test specific hypotheses of the disease and explore mechanisms of pathogenesis. Here, we consider some of the insights that have emerged from studying in mice the relationship between defined genetic and molecular alterations and the cognitive endophenotypes of schizophrenia.

Evidence-based medicine and electrophysiology in schizophrenia

In research on schizophrenia electrophysiological measures have been investigated to identify biomarkers of the disorder, indices enabling differential diagnosis among psychotic disorders, prognostic indicators or endophenotypes. The present systematic review will focus on the most largely studied electrophysiological indices, i.e., qualitative or quantitative (limited to spectral analysis) EEG and the P300 event-related potential. The PubMed clinical query was used with research methodology filters for each of the following categories: diagnosis/prognosis/ aetiology and a broad sensitive search strategy. The key-words: SCHIZOPHRENIA AND EEG/P3/P300 were used. The search results were then narrowed by including the terms "human" and "English language", and cross-referenced. Systematic reviews and meta-analyses, when available, were also used for cross-referencing. Case reports and studies irrelevant to the topics and methodologies under examination were excluded. The remaining papers were screened to verify the eligibility for this systematic review. Inclusion criteria were: a) a diagnosis of schizophrenia confirmed by DSM-III/ICD-9 criteria (or later editions of the same classification systems); b) the inclusion of both a schizophrenia study group and an healthy control group (when appropriate, i.e., for P300 and quantitative EEG); c) qualitative or spectral EEG findings and amplitude measures for P300. The included studies were then reviewed to verify homogeneity of the results, as well as the presence of the information needed for the present systematic review and meta-analysis. Previous reviews and studies meeting the above requirements (n = 22 for qualitative EEG; n = 45 for spectral EEG and n = 132 for P300) were classified according to the Oxford Centre for Evidence-based Medicine (EBM) levels of evidence criteria. For qualitative EEG as a diagnostic test, the majority of studies predated the introduction of DSM-III and were excluded from the review. Few post DSM-III studies investigated the usefulness of qualitative EEG in the differential diagnosis between schizophrenia and psychosis due to general medical condition. None of them was Oxford CEBM level 3b (non-consecutive-study or cohort-study without consistently-applied reference standard) or better (exploratory or validating cohort-study). No meta-analysis could be conducted due to the lack of reliable quantification methods in the reviewed studies. For spectral EEG as a diagnostic test, most studies qualified as level 4 (case-control study with poor reference standard), and only 24% as level 3b or better. An increase of slow activity in patients is reported by most of these studies. As to meta-analyses examining 29 studies, with 32 independent samples for the delta band and 35 for the theta band, a moderate effect size was found and only 1 study yielded findings in the opposite direction for both measures. There was no identified source for the discrepancy. The analysis of moderator factors included medication, band frequency limits, spectral parameters and disease stage. The medication status was significant for the theta band but the effect was unclear as findings for drug-naïve and drug-free patients were in a different direction. Chronicity had a significant effect on both delta and theta bands, with slow activity increase larger in chronic than in first episode patients. For P3 amplitude reduction as a diagnostic index, 63% of the studies qualified as level 3b or better. Meta-analysis (52 studies, 60 independent samples) results demonstrated a large effect size. None of the studies reported opposite findings. The analysis of moderator factors, including medication status and disease stage, revealed no significant effect on data heterogeneity. In conclusion, the examined indices are good candidates but are not ready yet for clinical applications aimed to improve present diagnostic standards for schizophrenia. Further research carried out according to adequate methodological standards and based on large scale multi-center studies is mandatory.

Schizophrenia from a neural circuitry perspective: advancing toward rational pharmacological therapies

Schizophrenia is a severe disorder that disrupts the function of multiple brain systems, resulting in impaired social and occupational functioning. The etiology and pathogenesis of schizophrenia appear to involve the interplay of a potentially large number of genetic liabilities and adverse environmental events that disrupt brain developmental pathways. In this Review, we discuss a strategy for determining how particular common and core clinical features of the illness are associated with pathophysiology in certain circuits of the cerebral cortex. The identification of molecular alterations in these circuits is providing critical insights for the rational development of new therapeutic interventions.

Clinical perspectives on the genetics of schizophrenia: a bottom-up orientation

Phenomenology has been the reference point that investigators have used in their efforts to understand schizophrenia. Although symptoms and signs are crucial for the diagnosis of schizophrenia, there is an ongoing debate since Kraepelin attempted to group symptoms to understand the etiology of schizophrenia. Several operational criteria have been developed to establish the diagnosis of schizophrenia, making it obvious that there are no precise symptomatological boundaries. There is little clear indication which of the systems is valid for genetic and other biological research. Despite the enormous effort to find a linkage between schizophrenia and one or more loci, the results are far from conclusive. Another approach is the search for candidate genes of which DICS1 and 22q11 deletion syndrome are examples. In all studies into the genetic underpinnings of schizophrenia, however, the clinical vantage point is neglected in that a broad clinical phenotype with respect to, e.g., developmental issues, symptoms and comorbidity is narrowed down to one categorical diagnosis. This is illustrated by the lack of exclusion criteria in genetic studies and by the occurrence of schizophrenia-like psychoses in a broad array of genetic syndromes. In case of 22q11 deletion syndrome, the psychotic symptoms emerge in the context of brain anomalies, a plethora of somatic abnormalities and specific neurocognitive deficits. Prader-Willi syndrome is a hypothalamic disorder in which psychotic symptoms may occur that resemble schizophrenia. It is concluded that not only schizophrenia is a highly variable disease but that the genetic samples are even much more heterogeneous.

Disrupted in schizophrenia 1 regulates neuronal progenitor proliferation via modulation of GSK3beta/beta-catenin signaling

The Disrupted in Schizophrenia 1 (DISC1) gene is disrupted by a balanced chromosomal translocation (1; 11) (q42; q14.3) in a Scottish family with a high incidence of major depression, schizophrenia, and bipolar disorder. Subsequent studies provided indications that DISC1 plays a role in brain development. Here, we demonstrate that suppression of DISC1 expression reduces neural progenitor proliferation, leading to premature cell cycle exit and differentiation. Several lines of evidence suggest that DISC1 mediates this function by regulating GSK3beta. First, DISC1 inhibits GSK3beta activity through direct physical interaction, which reduces beta-catenin phosphorylation and stabilizes beta-catenin. Importantly, expression of stabilized beta-catenin overrides the impairment of progenitor proliferation caused by DISC1 loss of function. Furthermore, GSK3 inhibitors normalize progenitor proliferation and behavioral defects caused by DISC1 loss of function. Together, these results implicate DISC1 in GSK3beta/beta-catenin signaling pathways and provide a framework for understanding how alterations in this pathway may contribute to the etiology of psychiatric disorders.

Association of variants in DISC1 with psychosis-related traits in a large population cohort

CONTEXT

There is an abundance of data from human genetic studies and animal models that implies a role for the disrupted in schizophrenia 1 gene (DISC1) in the etiology of schizophrenia and other major mental illnesses.

OBJECTIVE

To study the effect of previously identified risk alleles of DISC1 on quantitative intermediate phenotypes for psychosis in an unselected population.

DESIGN

We examined 41 single-nucleotide polymorphisms within DISC1 and performed tests of association with 4 quantitative phenotypes.

SETTING

Academic research.

PARTICIPANTS

Individuals from an unselected birth cohort in Finland. Originally, everyone born in the catchment area in 1966 (N = 12 058) was included in the study. Of these, 4651 (38.6%) attended the 31-year follow-up and could be included in the study.

MAIN OUTCOME MEASURES

Scores on 4 psychometric instruments selected to function as proxies for positive and negative aspects of psychotic disorders, including the Perceptual Aberration Scale, Revised Social Anhedonia Scale, Revised Physical Anhedonia Scale, and Schizoidia Scale by Golden and Meehl.

RESULTS

Carriers of the minor allele of marker rs821577 had significantly higher scores on social anhedonia (P < .001). The minor allele of marker rs821633 was strongly associated with lower scores on social anhedonia when analyzed dependent on the absence of the minor alleles of markers rs1538979 and rs821577 (P < .001).

CONCLUSIONS

Variants in DISC1 affect the level of social anhedonia, a cardinal symptom of schizophrenia in the general population. DISC1 might be more central to human psychological functioning than previously thought, as it seems to affect the degree to which people enjoy social interactions.

NDE1 and NDEL1: multimerisation, alternate splicing and DISC1 interaction

Nuclear Distribution Factor E Homolog 1 (NDE1) and NDE-Like 1 (NDEL1) are highly homologous mammalian proteins. However, whereas NDEL1 is well studied, there is remarkably little known about NDE1. We demonstrate the presence of multiple isoforms of both NDE1 and NDEL1 in the brain, showing that NDE1 binds directly to multiple isoforms of Disrupted in Schizophrenia 1 (DISC1), and to itself. We also show that NDE1 can complex with NDEL1. Together these results predict a high degree of complexity of DISC1-mediated regulation of neuronal activity.

Autism spectrum disorders and childhood-onset schizophrenia: clinical and biological contributions to a relation revisited

OBJECTIVE

To highlight emerging evidence for clinical and biological links between autism/pervasive developmental disorder (PDD) and schizophrenia, with particular attention to childhood-onset schizophrenia (COS).

METHOD

Clinical, demographic, and brain developmental data from the National Institute of Mental Health (and other) COS studies and selected family, imaging, and genetic data from studies of autism, PDD, and schizophrenia were reviewed.

RESULTS

In the two large studies that have examined this systematically, COS is preceded by and comorbid with PDD in 30% to 50% of cases. Epidemiological and family studies find association between the disorders. Both disorders have evidence of accelerated trajectories of anatomic brain development at ages near disorder onset. A growing number of risk genes and/or rare small chromosomal variants (microdeletions or duplications) are shared by schizophrenia and autism.

CONCLUSIONS

Biological risk does not closely follow DSM phenotypes, and core neurobiological processes are likely common for subsets of these two heterogeneous clinical groups. Long-term prospective follow-up of autistic populations and greater diagnostic distinction between schizophrenia spectrum and autism spectrum disorders in adult relatives are needed.

Schizophrenia-related neural and behavioral phenotypes in transgenic mice expressing truncated Disc1

Disrupted-in-Schizophrenia-1 (DISC1), identified by positional cloning of a balanced translocation (1;11) with the breakpoint in intron 8 of a large Scottish pedigree, is associated with a range of neuropsychiatric disorders including schizophrenia. To model this mutation in mice, we have generated Disc1(tr) transgenic mice expressing 2 copies of truncated Disc1 encoding the first 8 exons using a bacterial artificial chromosome (BAC). With this partial simulation of the human situation, we have discovered a range of phenotypes including a series of novel features not previously reported. Disc1(tr) transgenic mice display enlarged lateral ventricles, reduced cerebral cortex, partial agenesis of the corpus callosum, and thinning of layers II/III with reduced neural proliferation at midneurogenesis. Parvalbumin GABAergic neurons are reduced in the hippocampus and medial prefrontal cortex, and displaced in the dorsolateral frontal cortex. In culture, transgenic neurons grow fewer and shorter neurites. Behaviorally, transgenic mice exhibit increased immobility and reduced vocalization in depression-related tests, and impairment in conditioning of latent inhibition. These abnormalities in Disc1(tr) transgenic mice are consistent with findings in severe schizophrenia.

Association of the SerCys DISC1 polymorphism with human hippocampal formation gray matter and function during memory encoding

A common nonsynonymous single nucleotide polymorphism leading to a serine-to-cysteine substitution at amino acid 704 (Ser(704)Cys) in the DISC1 protein sequence has been recently associated with schizophrenia and with specific hippocampal abnormalities. Here, we used multimodal neuroimaging to investigate in a large sample of healthy subjects the putative association of the Ser(704)Cys DISC1 polymorphism with in vivo brain phenotypes including hippocampal formation (HF) gray matter volume and function (as assessed with functional MRI) as well as HF functional coupling with the neural network engaged during encoding of recognition memory. Individuals homozygous for DISC1 Ser allele relative to carriers of the Cys allele showed greater gray matter volume in the HF. Further, Ser/Ser subjects exhibited greater engagement of the HF together with greater HF-dorsolateral prefrontal cortex functional coupling during memory encoding, in spite of similar behavioral performance. These findings consistently support the notion that Ser(704)Cys DISC1 polymorphism is physiologically relevant. Moreover, they support the hypothesis that genetic variation in DISC1 may affect the risk for schizophrenia by modifying hippocampal gray matter and function.

DISC1-kendrin interaction is involved in centrosomal microtubule network formation

Disrupted-In-Schizophrenia 1 (DISC1) was identified as a novel gene disrupted by a (1;11)(q42.1;q14.3) translocation segregating with schizophrenia, bipolar disorder and other major mental illnesses in a Scottish family. We previously identified 446-533 amino acids of DISC1 as the kendrin-binding region by means of a directed yeast two-hybrid interaction assay and showed that the DISC1-kendrin interaction is indispensable for the centrosomal localization of DISC1. In this study, to confirm the DISC1-kendrin interaction, we examined the interaction between deletion mutants of DISC1 and kendrin. Then, we demonstrated that the carboxy-terminus of DISC1 is indispensable for the interaction with kendrin. Furthermore, the immunocytochemistry revealed that the carboxy-terminus of DISC1 is also required for the centrosomal targeting of DISC1. Overexpression of the DISC1-binding region of kendrin or the DISC1 deletion mutant lacking the kendrin-binding region impairs the microtubule organization. These findings suggest that the DISC1-kendrin interaction plays a key role in the microtubule dynamics.

Mice lacking the schizophrenia-associated protein FEZ1 manifest hyperactivity and enhanced responsiveness to psychostimulants

FEZ1 (fasciculation and elongation protein zeta 1), a mammalian ortholog of Caenorhabditis elegans UNC-76, interacts with DISC1 (disrupted in schizophrenia 1), a schizophrenia susceptibility gene product, and polymorphisms of human FEZ1 have been associated with schizophrenia. We have now investigated the role of FEZ1 in brain development and the pathogenesis of schizophrenia by generating mice that lack Fez1. Immunofluorescence staining revealed FEZ1 to be located predominantly in gamma-aminobutyric acid-containing interneurons. The Fez1(-/-) mice showed marked hyperactivity in a variety of behavioral tests as well as enhanced behavioral responses to the psychostimulants MK-801 and methamphetamine. In vivo microdialysis revealed that the methamphetamine-induced release of dopamine in the nucleus accumbens was exaggerated in the mutant mice, suggesting that enhanced mesolimbic dopaminergic transmission contributes to their hyperactivity phenotype. These observations implicate impairment of FEZ1 function in the pathogenesis of schizophrenia.

Associations of ATF4 gene polymorphisms with schizophrenia in male patients

Activating transcription factor 4 (ATF4) is considered as a positional candidate gene for schizophrenia due to its location at chromosome 22q13, a region linked to schizophrenia. Furthermore, as protein interaction partner of ATF4, disrupted in schizophrenia 1 (DISC1) and its signal pathway implicated in the pathophysiology of schizophrenia have been widely supported by a number of genetic and neurobiological studies. Our aim was to investigate whether ATF4 is associated with schizophrenia in case-control samples of Han Chinese subjects consisting of 352 schizophrenia patients and 357 healthy controls. We detected 18 single nucleotide polymorphisms (SNPs) in ATF4 locus, two of which were analyzed, including one insertion at the putative core promoter region (rs17001266, -/C) and one nonsynonymous variant in exon 1 (rs4894, C/A, Pro22Gln). Allele distributions of two SNPs showed significant associations with schizophrenia in male subjects (respectively, rs17001266: P = 0.021, OR = 1.58, 95% CI = 1.07-2.33; rs4894: P = 0.004, OR = 1.78, 95% CI = 1.19-2.67), but not in female subjects as well as the entire population. Two haplotypes CC and -A constructed of rs17001266-rs4894 also revealed significant associations with schizophrenia in male group (global P = 0.0097). These findings support that ATF4 gene may be involved in susceptibility to schizophrenia with sex-dependent effect in the Chinese Han population and suggest that further functional assays are needed to verify their relevance to the pathogenesis of schizophrenia.

DISC1 is associated with prefrontal cortical gray matter and positive symptoms in schizophrenia

BACKGROUND

DISC1 is considered a susceptibility gene for schizophrenia and schizoaffective disorder, but little is known regarding the potential mechanisms through which it may confer increased risk. Given that DISC1 plays a role in cerebral cortex development, polymorphisms in this gene may have relevance for neurobiological models of schizophrenia that have implicated cortical deficits in its pathophysiology.

METHODS

We investigated whether the DISC1 leu607phe polymorphism was associated with prefrontal gray matter volumes using magnetic resonance imaging in a cohort of patients with schizophrenia (N=19) and healthy volunteers (N=25) and positive and negative symptoms in 200 patients with schizophrenia.

RESULTS

Among patients and healthy volunteers, phe carriers (N=11) had significantly less gray matter in the superior frontal gyrus and anterior cingulate gyrus compared to leu/leu homozygotes (N=33). Further, among patients left superior frontal gyrus gray matter volume was significantly negatively correlated with severity of hallucinations. In addition, patients who were phe carriers (N=144) had significantly greater severity of positive symptoms (hallucinations) compared to patients who were leu/leu homozygotes (N=56).

DISCUSSION

These findings implicate DISC1 in variation of prefrontal cortical volume and positive symptoms, thus providing a potential mechanism through which DISC1 may confer increased risk for schizophrenia or schizoaffective disorder.

Molecular mechanisms of stress-induced prefrontal cortical impairment: implications for mental illness

The symptoms of mental illness often involve weakened regulation of thought, emotion, and behavior by the prefrontal cortex. Exposure to stress exacerbates symptoms of mental illness and causes marked prefrontal cortical dysfunction. Studies in animals have revealed the intracellular signaling pathways activated by stress exposure that induce profound prefrontal cortical impairment: Excessive dopamine stimulation of D1 receptors impairs prefrontal function via cAMP intracellular signaling, leading to disconnection of prefrontal networks, while excessive norepinephrine stimulation of alpha1 receptors impairs prefrontal function via phosphatidylinositol-protein kinase C intracellular signaling. Genetic studies indicate that the genes disrupted in serious mental illness (bipolar disorder and schizophrenia) often encode for the intracellular proteins that serve as brakes on the intracellular stress pathways. For example, disrupted in schizophrenia 1 (DISC1) normally regulates cAMP levels, while regulator of G protein signaling 4 (RGS4) and diacylglycerol kinase (DGKH)-the molecule most associated with bipolar disorder- normally serve to inhibit phosphatidylinositol-protein kinase C intracellular signaling. Patients with mutations resulting in loss of adequate function of these genes likely have weaker endogenous regulation of these stress pathways. This may account for the vulnerability to stress and the severe loss of PFC regulation of behavior, thought, and affect in these illnesses. This review highlights the signaling pathways onto which genetic vulnerability and stress converge to impair PFC function and induce debilitating symptoms such as thought disorder, disinhibition, and impaired working memory.

Schizophrenia: from developmental deviance to dopamine dysregulation

Two major theories of schizophrenia are respectively, the neurodevelopmental hypothesis and the dopamine hypothesis. Each of these has recently been revised. Firstly, the classical neurodevelopmental hypothesis has been modified to include the pathogenic effects of psychostimulants and cannabis abuse, and also of chronic social adversity; it is perhaps now more appropriately termed, the developmental hypothesis. Secondly, recent amendments to the dopamine hypothesis suggest that excess striatal dopamine is responsible for increased salience being given to insignificant events and thoughts, and that this underpins the development of psychotic symptoms. Traditionally, it has been thought that this striatal dopamine dysregulation might be secondary to frontal dysfunction. However, recent animal research shows that over-expression of striatal D(2) receptors results in frontal dysfunction manifesting as cognitive difficulties and animal equivalents of so-called negative symptoms. This raises the question whether early intervention may prevent the development of these latter problems. Finally, the two theories are beginning to be integrated through the growing evidence that all the developmental risk factors which increase risk of schizophrenia appear to act by facilitating dopamine dysregulation.

Identification of YWHAE, a gene encoding 14-3-3epsilon, as a possible susceptibility gene for schizophrenia

Schizophrenia is a complex mental disorder with a fairly high degree of heritability. Although the causes of schizophrenia remain unclear, it is now widely accepted that it is a neurodevelopmental and neurodegenerative disorder involving disconnectivity and disorder of the synapses. Disrupted-in-schizophrenia 1 (DISC1) is a promising candidate susceptibility gene involved in neurodevelopment, including maturation of the cerebral cortex. To identify other susceptibility genes for schizophrenia, we screened for DISC1-interacting molecules [NudE-like (NUDEL), Lissencephaly-1 (LIS1), 14-3-3epsilon (YWHAE), growth factor receptor bound protein 2 (GRB2) and Kinesin family 5A of Kinesen1 (KIF5A)], assessing a total of 25 tagging single-nucleotide polymorphisms (SNPs) in a Japanese population. We identified a YWHAE SNP (rs28365859) that showed a highly significant difference between case and control samples, with higher minor allele frequencies in controls (P(allele) = 1.01 x 10(-5) and P(genotype) = 4.08 x 10(-5) in 1429 cases and 1728 controls). Both messenger RNA transcription and protein expression of 14-3-3epsilon were also increased in the lymphocytes of healthy control subjects harboring heterozygous and homozygous minor alleles compared with homozygous major allele subjects. To further investigate a potential role for YWHAE in schizophrenia, we studied Ywhae(+/-) mice in which the level of 14-3-3epsilon protein is reduced to 50% of that in wild-type littermates. These mice displayed weak defects in working memory in the eight-arm radial maze and moderately enhanced anxiety-like behavior in the elevated plus-maze. Our results suggest that YWHAE is a possible susceptibility gene that functions protectively in schizophrenia.

Neurophysiological endophenotypes across bipolar and schizophrenia psychosis

The search for liability genes of the world's 2 major psychotic disorders, schizophrenia and bipolar disorder I (BP-I), has been extremely difficult even though evidence suggests that both are highly heritable. This difficulty is due to the complex and multifactorial nature of these disorders. They encompass several intermediate phenotypes, some overlapping across the 2 psychotic disorders that jointly and/or interactively produce the clinical manifestations. Research of the past few decades has identified several neurophysiological deficits in schizophrenia that frequently occur before the onset of psychosis. These include abnormalities in smooth pursuit eye movements, P50 sensory gating, prepulse inhibition, P300, mismatch negativity, and neural synchrony. Evidence suggests that many of these physiological deficits are distinct from each other. They are stable, mostly independent of symptom state and medications (with some exceptions) and are also observed in non-ill relatives. This suggests a familial and perhaps genetic nature. Some deficits are also observed in the BP-I probands and to a lesser extent their relatives. These deficits in physiological measures may represent the intermediate phenotypes that index small effects of genes (and/or environmental factors). The use of these measures in genetic studies may help the hunt for psychosis liability genes and clarify the extent to which the 2 major psychotic disorders share etio-pathophysiology. In spite of the rich body of work describing these neurophysiological measures in psychotic disorders, challenges remain: Many of the neurophysiological phenotypes are still relatively complex and are associated with low heritability estimates. Further refinement of these physiological phenotypes is needed that could identify specific underlying physiological deficits and thereby improve their heritability estimates. The extent to which these neurophysiological deficits are unique or overlap across BP-I and schizophrenia is unclear. And finally, the clinical and functional consequences of the neurophysiological deficits both in the probands and their relatives are not well described.

Psychiatric genetics: progress amid controversy

Several psychiatric disorders--such as bipolar disorder, schizophrenia and autism--are highly heritable, yet identifying their genetic basis has been challenging, with most discoveries failing to be replicated. However, inroads have been made by the incorporation of intermediate traits (endophenotypes) and of environmental factors into genetic analyses, and through the identification of rare inherited variants and novel structural mutations. Current efforts aim to increase sample sizes by gathering larger samples for case-control studies or through meta-analyses of such studies. More attention on unique families, rare variants, and on incorporating environment and the emerging knowledge of biological function and pathways into genetic analysis is warranted.

Genetic causality in schizophrenia and bipolar disorder: out with the old and in with the new

Schizophrenia (SZ) and bipolar disorder are highly heritable forms of major mental illness. Great hopes were held out for a major breakthrough with the advent of genome wide association studies, but to date there have been no obvious low hanging fruit. A richer harvest of strong candidates has however emerged from molecular cytogenetics and copy number variant mapping strategies promise to add more. Both strategies identify gene mutations, paving a direct path to biological studies and tests of causality. Risk genes and convergent biological pathways common to both disorders are being revealed, offering hope for a better understanding of aetiological factors and for the development of biomarkers to aid in diagnosis and prognosis.

Insolubility of disrupted-in-schizophrenia 1 disrupts oligomer-dependent interactions with nuclear distribution element 1 and is associated with sporadic mental disease

Disrupted-in-schizophrenia 1 (DISC1) and other genes have been identified recently as potential molecular players in chronic psychiatric diseases such as affective disorders and schizophrenia. A molecular mechanism of how these genes may be linked to the majority of sporadic cases of these diseases remains unclear. The chronic nature and irreversibility of clinical symptoms in a subgroup of these diseases prompted us to investigate whether proteins corresponding to candidate genes displayed subtle features of protein aggregation. Here, we show that in postmortem brain samples of a distinct group of patients with phenotypes of affective disorders or schizophrenia, but not healthy controls, significant fractions of DISC1 could be identified as cold Sarkosyl-insoluble protein aggregates. A loss-of-function phenotype could be demonstrated for insoluble DISC1 through abolished binding to a key DISC1 ligand, nuclear distribution element 1 (NDEL1): in human neuroblastoma cells, DISC1 formed expression-dependent, detergent-resistant aggregates that failed to interact with endogenous NDEL1. Recombinant (r) NDEL1 expressed in Escherichia coli selectively bound an octamer of an rDISC1 fragment but not dimers or high molecular weight multimers, suggesting an oligomerization optimum for molecular interactions of DISC1 with NDEL1. For DISC1-related sporadic psychiatric disease, we propose a mechanism whereby impaired cellular control over self-association of DISC1 leads to excessive multimerization and subsequent formation of detergent-resistant aggregates, culminating in loss of ligand binding, here exemplified by NDEL1. We conclude that the absence of oligomer-dependent ligand interactions of DISC1 can be associated with sporadic mental disease of mixed phenotypes.

QTLs identified for P3 amplitude in a non-clinical sample: importance of neurodevelopmental and neurotransmitter genes

BACKGROUND

The P3(00) event-related potential is an index of processing capacity (P3 amplitude) and stimulus evaluation (P3 latency) as well as a phenotypic marker of various forms of psychopathology where P3 abnormalities have been reported.

METHODS

A genome-wide linkage scan of 400-761 autosomal markers, at an average spacing of 5-10 centimorgans (cM), was completed in 647 twins/siblings (306 families mostly comprising dizygotic twins), mean age 16.3, range 15.4-20.1 years, for whom P3 amplitude and latency data were available.

RESULTS

Significant linkage for P3 amplitude was observed on chromosome 7q for the central recording site (logarithm-of-odds [LOD] = 3.88, p = .00002) and in the same region for both frontal (LOD = 2.19, p = .0015) and parietal (LOD = 1.67, p = .0053) sites, with multivariate analysis also identifying linkage in this region (LOD = 2.14, p = .0017). Suggestive linkage was also identified on 6p (LOD(max) = 2.49) and 12q (LOD(max) = 2.24), with other promising regions identified on 9q (LOD(max) = 2.14) and 10p (LOD(max) = 2.18). Less striking were the results for P3 latency; LOD > 1.5 were found on chromosomes 1q, 9q, 10q, 12q, and 19p.

CONCLUSIONS

This is a first step in the identification of genes for normal variation in the P3. Loci identified here for P3 amplitude suggest the possible importance of neurodevelopmental genes in addition to those influencing neurotransmitters, fitting with the evidence that P3 amplitude is sensitive to diverse types of brain abnormalities.

Disrupted-in-Schizophrenia-1

Chromosomal abnormalities can be powerful tools to identify genes that influence disease risk. The study of a chromosome translocation that segregated with severe psychiatric illness in a large family led directly to the discovery of a gene disrupted by a chromosomal breakpoint. Disrupted-in-Schizophrenia-1 (DISC1) is now an important candidate risk gene for schizophrenia and affective disorders. We review the work that led up to this discovery and the evidence that it is important in the wider population with schizophrenia and affective disorders. We also discuss the latest findings on the neuronal functions of the protein DISC1 encoded by the gene.

Validating endophenotypes for schizophrenia using statistical modeling of twin data

The use of endophenotypes (intermediate quantitative traits) is one strategy that may provide valuable information about the neural mechanisms underlying disease etiology and facilitate discovery of susceptibility genes. For a trait to be an appropriate endophenotype, several key features should exist. In this article we discuss validating potential electrophysiological endophenotypes for schizophrenia based on conventionally accepted criteria. We focus on applying a twin study design and model fitting techniques to evaluate whether three event-related potential paradigms (P300, P50, and MMN) meet criteria as valid endophenotypes of schizophrenia.

Genomic structural variation and schizophrenia

It has recently been demonstrated that a large amount of structural variation exists in the human genome. Since 2004, when two landmark studies reported polymorphic levels of copy number variation in phenotypically normal individuals, our understanding of genome-wide levels of copy number variation has grown. This has inspired hypotheses about this class of variation's contribution to complex genetic phenotypes, including the specific hypothesis that structural variation is associated with psychiatric illness. The technology to accurately and efficiently detect polymorphic structural variants is still largely under development, but some examples of genomic imbalance contributing to schizophrenia and bipolar disorder already have been identified. Although much optimism surrounds this burgeoning field, the technical challenges in reliably identifying structural variation mean recent literature should be approached with caution.

Gene and expression analyses reveal enhanced expression of pericentrin 2 (PCNT2) in bipolar disorder

BACKGROUND

DISC1 has been suggested as a causative gene for psychoses in a large Scottish kindred. PCNT2 has recently been identified as an interacting partner of DISC1. In this study, we investigated the role of PCNT2 in bipolar disorder, by gene expression analysis and genetic association study.

METHODS

By TaqMan real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), we examined the messenger RNA (mRNA) levels of PCNT2 in the postmortem prefrontal cortex of bipolar disorder (n = 34), schizophrenia (n = 31), and control subjects (n = 32), obtained from Stanley Array Collection. We also compared the mRNA levels of PCNT2 in the peripheral blood lymphocytes of bipolar disorder (n = 21), schizophrenia (n = 21), depression (n = 33), and control subjects (n = 57). For the association study, 23 single nucleotide polymorphisms (SNPs) were analyzed in 285 bipolar disorder patients and 287 age-and gender-matched control subjects, all of Japanese origin. The genotypes were determined by TaqMan assay.

RESULTS

Significantly higher expression of PCNT2 was observed in the brain samples of bipolar group, compared with the control (p = .001) and schizophrenia (p = .018) groups. In the peripheral blood lymphocytes also, a significantly higher expression of PCNT2 was observed in the bipolar group, compared with the control subjects (p = .043). However, none of the SNPs analyzed in our study showed a significant association with bipolar disorder; a weak tendency toward association was observed for two intronic SNPs.

CONCLUSIONS

Our findings suggest that elevated levels of PCNT2 might be implicated in the pathophysiology of bipolar disorder.