Identification of candidate genes for psychosis in rat models, and possible association between schizophrenia and the 14-3-3eta gene

The 14-3-3 Protein Family and Schizophrenia

Schizophrenia is a debilitating mental disorder that affects approximately 1% of the world population, yet the disorder is not very well understood. The genetics of schizophrenia is very heterogenous, making it hard to pinpoint specific alterations that may cause the disorder. However, there is growing evidence from human studies suggesting a link between alterations in the 14-3-3 family and schizophrenia. The 14-3-3 proteins are abundantly expressed in the brain and are involved in many important cellular processes. Knockout of 14-3-3 proteins in mice has been shown to cause molecular, structural, and behavioral alterations associated with schizophrenia. Thus, 14-3-3 animal models allow for further exploration of the relationship between 14-3-3 and schizophrenia as well as the study of schizophrenia pathology. This review considers evidence from both human and animal model studies that implicate the 14-3-3 family in schizophrenia. In addition, possible mechanisms by which alterations in 14-3-3 proteins may contribute to schizophrenia-like phenotypes such as dopaminergic, glutamatergic, and cytoskeletal dysregulations are discussed.

Dysregulation of peripheral expression of the YWHA genes during conversion to psychosis

The seven human 14-3-3 proteins are encoded by the YWHA-gene family. They are expressed in the brain where they play multiple roles including the modulation of synaptic plasticity and neuronal development. Previous studies have provided arguments for their involvement in schizophrenia, but their role during disease onset is unknown. We explored the peripheral-blood expression level of the seven YWHA genes in 92 young individuals at ultra-high risk for psychosis (UHR). During the study, 36 participants converted to psychosis (converters) while 56 did not (non-converters). YWHA genes expression was evaluated at baseline and after a mean follow-up of 10.3 months using multiplex quantitative PCR. Compared with non-converters, the converters had a significantly higher baseline expression levels for 5 YWHA family genes, and significantly different longitudinal changes in the expression of YWHAE, YWHAG, YWHAH, YWHAS and YWAHZ. A principal-component analysis also indicated that the YWHA expression was significantly different between converters and non-converters suggesting a dysregulation of the YWHA co-expression network. Although these results were obtained from peripheral blood which indirectly reflects brain chemistry, they indicate that this gene family may play a role in psychosis onset, opening the way to the identification of prognostic biomarkers or new drug targets.

Involvement of the 14-3-3 Gene Family in Autism Spectrum Disorder and Schizophrenia: Genetics, Transcriptomics and Functional Analyses

The 14-3-3 protein family are molecular chaperones involved in several biological functions and neurological diseases. We previously pinpointed YWHAZ (encoding 14-3-3ζ) as a candidate gene for autism spectrum disorder (ASD) through a whole-exome sequencing study, which identified a frameshift variant within the gene (c.659-660insT, p.L220Ffs*18). Here, we explored the contribution of the seven human 14-3-3 family members in ASD and other psychiatric disorders by investigating the: (i) functional impact of the 14-3-3ζ mutation p.L220Ffs*18 by assessing solubility, target binding and dimerization; (ii) contribution of common risk variants in 14-3-3 genes to ASD and additional psychiatric disorders; (iii) burden of rare variants in ASD and schizophrenia; and iv) 14-3-3 gene expression using ASD and schizophrenia transcriptomic data. We found that the mutant 14-3-3ζ protein had decreased solubility and lost its ability to form heterodimers and bind to its target tyrosine hydroxylase. Gene-based analyses using publicly available datasets revealed that common variants in YWHAE contribute to schizophrenia (p = 6.6 × 10-7), whereas ultra-rare variants were found enriched in ASD across the 14-3-3 genes (p = 0.017) and in schizophrenia for YWHAZ (meta-p = 0.017). Furthermore, expression of 14-3-3 genes was altered in post-mortem brains of ASD and schizophrenia patients. Our study supports a role for the 14-3-3 family in ASD and schizophrenia.

Interactome Studies of Psychiatric Disorders

High comorbidity and complexity have precluded reliable diagnostic assessment and treatment of psychiatric disorders. Impaired molecular interactions may be relevant for underlying mechanisms of psychiatric disorders but by and large remain unknown. With the help of a number of publicly available databases and various technological tools, recent research has filled the paucity of information by generating a novel dataset of psychiatric interactomes. Different technological platforms including yeast two-hybrid screen, co-immunoprecipitation-coupled with mass spectrometry-based proteomics, and transcriptomics have been widely used in combination with cellular and molecular techniques to interrogate the psychiatric interactome. Novel molecular interactions have been identified in association with different psychiatric disorders including autism spectrum disorders, schizophrenia, bipolar disorder, and major depressive disorder. However, more extensive and sophisticated interactome research needs to be conducted to overcome the current limitations such as incomplete interactome databases and a lack of functional information among components. Ultimately, integrated psychiatric interactome databases will contribute to the implementation of biomarkers and therapeutic intervention.

Studies on Prostaglandin-Endoperoxide Synthase 1: Lower Levels in Schizophrenia and After Treatment with Antipsychotic Drugs in Conjunction with Aspirin

Background

Antipsychotic drugs plus aspirin (acetylsalicylic acid), which targets prostaglandin-endoperoxide synthase 1 (PTGS1: COX1), improved therapeutic outcomes when treating schizophrenia. Our microarray data showed higher levels of PTGS1 mRNA in the dorsolateral prefrontal cortex from subjects with schizophrenia of long duration of illness, suggesting aspirin plus antipsychotic drugs could have therapeutic effects by lowering PTGS1 expression in the cortex of subjects with the disorder.

Methods

We used Western blotting to measure levels of PTSG1 protein in human postmortem CNS, rat and mouse cortex, and cells in culture.

Results

Compared with controls, PTGS1 levels were 41% lower in the dorsolateral prefrontal cortex (P<.01), but not the anterior cingulate or frontal pole, from subjects with schizophrenia. Levels of PTGS1 were not changed in the dorsolateral prefrontal cortex in mood disorders or in the cortex of rats treated with antipsychotic drugs. There was a strong trend (P=.05) to lower cortical PTGS1 10 months after mice were treated postnatally with polyinosinic-polycytidylic acid sodium salt (Poly I:C), consistent with cortical PTGS1 being lower in adult mice after exposure to an immune activator postnatally. In CCF-STTG1 cells, a human-derived astrocytic cell line, aspirin caused a dose-dependent decrease in PTGS1 that was decreased further with the addition of risperidone.

Conclusions

Our data suggest low levels of dorsolateral prefrontal cortex PTGS1 could be associated with the pathophysiology of schizophrenia, and improved therapeutic outcome from treating schizophrenia with antipsychotic drugs augmented with aspirin may be because such treatment lowers cortical PTGS1.

Comparative Analysis of Gene Expression Profiles Involved in Calcium Signaling Pathways Using the NLVH Animal Model of Schizophrenia

In this study, we evaluated the expression profile changes of genes that intervene in the calcium signaling pathway, in young and adult Wistar rats, using the animal model of neonatal lesion in ventral hippocampus (NLVH) (a recognized animal model for schizophrenia) and compared to the group of control animals (Sham). Through microarray technology, gene expression profiles were obtained from the three brain areas (nucleus accumbens, prefrontal cortex, and hippocampus) of young male Wistar rats (45 days) and adults (90 days) whether or not subjected to NLVH. The calcium signaling pathway reported a greater number of differentially expressed genes with z-score two values, > 2 (over-expression) and < - 2 (under-expression), in the three evaluated areas. The comparative analyses of this approach were performed in juvenile and adult rats with ventral hippocampal lesion in neonate rats (NLVH). NLVH influenced change expressions in various genes involved in Ca²⁺ homeostasis, including Cacna1d, Atp2a2, Adcy2, Ppp3cb, and Ptk2b. The expression of Adcy2, Ppp3cb, and Ptk2b genes changed in both age groups; therefore, the study of gene expression profiles between juvenile and adult rats may help to understand the molecular mechanisms of schizophrenia.

Identification of the BRD1 interaction network and its impact on mental disorder risk

Background

The bromodomain containing 1 (BRD1) gene has been implicated with transcriptional regulation, brain development, and susceptibility to schizophrenia and bipolar disorder. To advance the understanding of BRD1 and its role in mental disorders, we characterized the protein and chromatin interactions of the BRD1 isoforms, BRD1-S and BRD1-L.

Methods

Stable human cell lines expressing epitope tagged BRD1-S and BRD1-L were generated and used as discovery systems for identifying protein and chromatin interactions. Protein-protein interactions were identified using co-immunoprecipitation followed by mass spectrometry and chromatin interactions were identified using chromatin immunoprecipitation followed by next generation sequencing. Gene expression profiles and differentially expressed genes were identified after upregulating and downregulating BRD1 expression using microarrays. The presented functional molecular data were integrated with human genomic and transcriptomic data using available GWAS, exome-sequencing datasets as well as spatiotemporal transcriptomic datasets from the human brain.

Results

We present several novel protein interactions of BRD1, including isoform-specific interactions as well as proteins previously implicated with mental disorders. By BRD1-S and BRD1-L chromatin immunoprecipitation followed by next generation sequencing we identified binding to promoter regions of 1540 and 823 genes, respectively, and showed correlation between BRD1-S and BRD1-L binding and regulation of gene expression. The identified BRD1 interaction network was found to be predominantly co-expressed with BRD1 mRNA in the human brain and enriched for pathways involved in gene expression and brain function. By interrogation of large datasets from genome-wide association studies, we further demonstrate that the BRD1 interaction network is enriched for schizophrenia risk.

Conclusion

Our results show that BRD1 interacts with chromatin remodeling proteins, e.g. PBRM1, as well as histone modifiers, e.g. MYST2 and SUV420H1. We find that BRD1 primarily binds in close proximity to transcription start sites and regulates expression of numerous genes, many of which are involved with brain development and susceptibility to mental disorders. Our findings indicate that BRD1 acts as a regulatory hub in a comprehensive schizophrenia risk network which plays a role in many brain regions throughout life, implicating e.g. striatum, hippocampus, and amygdala at mid-fetal stages.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0308-x) contains supplementary material, which is available to authorized users.

Dysregulated 14-3-3 Family in Peripheral Blood Leukocytes of Patients with Schizophrenia

The 14-3-3 family, which is composed of seven distinct members in humans, plays important roles in the cell cycle, apoptosis, synaptic plasticity and neuronal differentiation and migration. Previous genetic and post-mortem gene expression studies have linked this family to schizophrenia. However, the direction of gene expression changes in these studies has been inconsistent, and reports of 14-3-3 gene expression in living schizophrenic patients are still lacking. Here, we assessed 14-3-3 gene and protein expression levels in peripheral blood leukocytes from drug-naïve first-episode schizophrenic patients and matched controls. mRNA and protein expression levels were quantified by qRT-PCR and UPLC-MRM/MS, respectively. Expression analysis revealed four downregulated and one upregulated mRNA transcripts as well as five downregulated protein levels of 14-3-3 isoforms in schizophrenia. Moreover, significant positive correlations between 14-3-3 mRNA and protein expression levels were found in schizophrenia, and we also identified negative correlations between ε, θ and ζ isoform expression levels and positive symptoms of schizophrenia. Our results suggest that gene and protein expression levels for the 14-3-3 family are dysregulated in schizophrenia, perhaps owing to specific regulatory mechanisms, and we also suggest that expression of the 14-3-3ε, θ and ζ isoform genes could be useful indicators of disease severity.

Loss of function of Ywhah in mice induces deafness and cochlear outer hair cells' degeneration

In vertebrates, 14-3-3 proteins form a family of seven highly conserved isoforms with chaperone activity, which bind phosphorylated substrates mostly involved in regulatory and checkpoint pathways. 14-3-3 proteins are the most abundant protein in the brain and are abundantly found in the cerebrospinal fluid in neurodegenerative diseases, suggesting a critical role in neuron physiology and death. Here we show that 14-3-3eta-deficient mice displayed auditory impairment accompanied by cochlear hair cells' degeneration. We show that 14-3-3eta is highly expressed in the outer and inner hair cells, spiral ganglion neurons of cochlea and retinal ganglion cells. Screening of YWHAH, the gene encoding the 14-3-3eta isoform, in non-syndromic and syndromic deafness, revealed seven non-synonymous variants never reported before. Among them, two were predicted to be damaging in families with syndromic deafness. In vitro, variants of YWHAH induce mild mitochondrial fragmentation and severe susceptibility to apoptosis, in agreement with a reduced capacity of mutated 14-3-3eta to bind the pro-apoptotic Bad protein. This study demonstrates that YWHAH variants can have a substantial effect on 14-3-3eta function and that 14-3-3eta could be a critical factor in the survival of outer hair cells.

Effect of MK-801 and Clozapine on the Proteome of Cultured Human Oligodendrocytes

Separate lines of evidence have demonstrated the involvement of N-methyl-D-aspartate (NMDA) receptor and oligodendrocyte dysfunctions in schizophrenia. Here, we have carried out shotgun mass spectrometry proteome analysis of oligodendrocytes treated with the NMDA receptor antagonist MK-801 to gain potential insights into these effects at the molecular level. The MK-801 treatment led to alterations in the levels of 68 proteins, which are associated with seven distinct biological processes. Most of these proteins are involved in energy metabolism and many have been found to be dysregulated in previous proteomic studies of post-mortem brain tissues from schizophrenia patients. Finally, addition of the antipsychotic clozapine to MK-801-treated oligodendrocyte cultures resulted in changes in the levels of 45 proteins and treatment with clozapine alone altered 122 proteins and many of these showed opposite changes to the MK-801 effects. Therefore, these proteins and the associated energy metabolism pathways should be explored as potential biomarkers of antipsychotic efficacy. In conclusion, MK-801 treatment of oligodendrocytes may provide a useful model for testing the efficacy of novel treatment approaches.

Protein expression profiles characterize distinct features of mouse cerebral cortices at different developmental stages

The proper development of the mammalian cerebral cortex requires precise protein synthesis and accurate regulation of protein expression levels. To reveal signatures of protein expression in developing mouse cortices, we here generate proteomic profiles of cortices at embryonic and postnatal stages using tandem mass spectrometry (MS/MS). We found that protein expression profiles are mostly consistent with biological features of the developing cortex. Gene Ontology (GO) and KEGG pathway analyses demonstrate conserved molecules that maintain cortical development such as proteins involved in metabolism. GO and KEGG pathway analyses further identify differentially expressed proteins that function at specific stages, for example proteins regulating the cell cycle in the embryonic cortex, and proteins controlling axon guidance in the postnatal cortex, suggesting that distinct protein expression profiles determine biological events in the developing cortex. Furthermore, the STRING network analysis has revealed that many proteins control a single biological event, such as the cell cycle regulation, through cohesive interactions, indicating a complex network regulation in the cortex. Our study has identified protein networks that control the cortical development and has provided a protein reference for further investigation of protein interactions in the cortex.

Rapid antidepressants stimulate the decoupling of GABA(B) receptors from GIRK/Kir3 channels through increased protein stability of 14-3-3η

A single injection of N-methyl-D-aspartate receptor (NMDAR) antagonists produces a rapid antidepressant response. Lasting changes in the synapse structure and composition underlie the effectiveness of these drugs. We recently discovered that rapid antidepressants cause a shift in the γ-aminobutyric acid receptor (GABABR) signaling pathway, such that GABABR activation shifts from opening inwardly rectifiying potassium channels (Kir/GIRK) to increasing resting dendritic calcium signal and mammalian Target of Rapamycin activity. However, little is known about the molecular and biochemical mechanisms that initiate this shift. Herein, we show that GABABR signaling to Kir3 (GIRK) channels decreases with NMDAR blockade. Blocking NMDAR signaling stabilizes the adaptor protein 14-3-3η, which decouples GABABR signaling from Kir3 and is required for the rapid antidepressant efficacy. Consistent with these results, we find that key proteins involved in GABABR signaling bidirectionally change in a depression model and with rapid antidepressants. In socially defeated rodents, a model for depression, GABABR and 14-3-3η levels decrease in the hippocampus. The NMDAR antagonists AP5 and Ro-25-6981, acting as rapid antidepressants, increase GABABR and 14-3-3η expression and decrease Kir3.2. Taken together, these data suggest that the shift in GABABR function requires a loss of GABABR-Kir3 channel activity mediated by 14-3-3η. Our findings support a central role for 14-3-3η in the efficacy of rapid antidepressants and define a critical molecular mechanism for activity-dependent alterations in GABABR signaling.

Up-regulated 14-3-3β and 14-3-3ζ proteins in prefrontal cortex of subjects with schizophrenia: effect of psychotropic treatment

14-3-3 is a family of conserved regulatory proteins that bind to a multitude of functionally diverse signalling proteins. Various genetic studies and gene expression and proteomic analyses have involved 14-3-3 proteins in schizophrenia (SZ). On the other hand, studies about the status of these proteins in major depressive disorder (MD) are still missing. Immunoreactivity values of cytosolic 14-3-3β and 14-3-3ζ proteins were evaluated by Western blot in prefrontal cortex (PFC) of subjects with schizophrenia (SZ; n=22), subjects with major depressive disorder (MD; n=21) and age-, gender- and postmortem delay-matched control subjects (n=52). The modulation of 14-3-3β and 14-3-3ζ proteins by psychotropic medication was also assessed. The analysis of both proteins in SZ subjects with respect to matched control subjects showed increased 14-3-3β (Δ=33±10%, p<0.05) and 14-3-3ζ (Δ=29±6%, p<0.05) immunoreactivity in antipsychotic-free but not in antipsychotic-treated SZ subjects. Immunoreactivity values of 14-3-3β and 14-3-3ζ were not altered in MD subjects. These results show the specific up-regulation of 14-3-3β and 14-3-3ζ proteins in PFC of SZ subjects and suggest a possible down-regulation of both proteins by antipsychotic treatment.

Use of translational pharmacodynamic biomarkers in early-phase clinical studies for schizophrenia

Schizophrenia is a severe mental disorder characterized by cognitive deficits, and positive and negative symptoms. The development of effective pharmacological compounds for the treatment of schizophrenia has proven challenging and costly, with many compounds failing during clinical trials. Many failures occur due to disease heterogeneity and lack of predictive preclinical models and biomarkers that readily translate to humans during early characterization of novel antipsychotic compounds. Traditional early-phase trials consist of single- or multiple-dose designs aimed at determining the safety and tolerability of an investigational compound in healthy volunteers. However, by incorporating a translational approach employing methodologies derived from preclinical studies, such as EEG measures and imaging, into the traditional Phase I program, critical information regarding a compound's dose-response effects on pharmacodynamic biomarkers can be acquired. Furthermore, combined with the use of patients with stable schizophrenia in early-phase clinical trials, significant 'de-risking' and more confident 'go/no-go' decisions are possible.

14-3-3 proteins are required for hippocampal long-term potentiation and associative learning and memory

14-3-3 is a family of regulatory proteins highly expressed in the brain. Previous invertebrate studies have demonstrated the importance of 14-3-3 in the regulation of synaptic functions and learning and memory. However, the in vivo role of 14-3-3 in these processes has not been determined using mammalian animal models. Here, we report the behavioral and electrophysiological characterization of a new animal model of 14-3-3 proteins. These transgenic mice, considered to be a 14-3-3 functional knock-out, express a known 14-3-3 inhibitor in various brain regions of different founder lines. We identify a founder-specific impairment in hippocampal-dependent learning and memory tasks, as well as a correlated suppression in long-term synaptic plasticity of the hippocampal synapses. Moreover, hippocampal synaptic NMDA receptor levels are selectively reduced in the transgenic founder line that exhibits both behavioral and synaptic plasticity deficits. Collectively, our findings provide evidence that 14-3-3 is a positive regulator of associative learning and memory at both the behavioral and cellular level.

Combined analysis of exon splicing and genome wide polymorphism data predict schizophrenia risk loci

Schizophrenia has a strong genetic basis, and genome-wide association studies (GWAS) have shown that effect sizes for individual genetic variants which increase disease risk are small, making detection and validation of true disease-associated risk variants extremely challenging. Specifically, we first identify genes with exons showing differential expression between cases and controls, indicating a splicing mechanism that may contribute to variation in disease risk and focus on those showing consistent differential expression between blood and brain tissue. We then perform a genome-wide screen for SNPs associated with both normalised exon intensity of these genes (so called splicing QTLs) as well as association with schizophrenia. We identified a number of significantly associated loci with a biologically plausible role in schizophrenia, including MCPH1, DLG3, ZC3H13, and BICD2, and additional loci that influence splicing of these genes, including YWHAH. Our approach of integrating genome-wide exon intensity with genome-wide polymorphism data has identified a number of plausible SZ associated loci.

Drug discovery based on genetic and metabolic findings in schizophrenia

Recent progress in the genetics of schizophrenia provides the rationale for re-evaluating causative factors and therapeutic strategies for this disease. Here, we review the major candidate susceptibility genes and relate the aberrant function of these genes to defective regulation of energy metabolism in the schizophrenic brain. Disturbances in energy metabolism potentially lead to neurodevelopmental deficits, impaired function of the mature nervous system and failure to maintain neurites/dendrites and synaptic connections. Current antipsychotic drugs do not specifically address these underlying deficits; therefore, a new generation of more effective medications is urgently needed. Novel targets for future drug discovery are identified in this review. The coordinated application of structure-based drug design, systems biology and research on model organisms may greatly facilitate the search for next-generation antipsychotic drugs.

Simulating real world functioning in schizophrenia using a naturalistic city environment and single-trial, goal-directed navigation

OBJECTIVE

To develop a virtual reality platform that would serve as a functionally meaningful measure of cognition in schizophrenia and that would also complement standard batteries of cognitive tests during clinical trials for cognitive treatments in schizophrenia, be amenable to human neuroimaging research, yet lend itself to neurobiological comparison with rodent analogs.

METHOD

Thirty-three patients with schizophrenia and 33 healthy controls matched for age, sex, video gaming experience, and education completed eight rapid, single-trial virtual navigation tasks within a naturalistic virtual city. Four trials tested their ability to find different targets seen during the passive viewing of a closed path that led them around different city blocks. Four subsequent trials tested their ability to return to four different starting points after viewing a path that took them several blocks away from the starting position.

RESULTS

Individuals with schizophrenia had difficulties in way-finding, measured as distance travelled to find targets previously encountered within the virtual city. They were also more likely not to notice the target during passive viewing, less likely to find novel shortcuts to targets, and more likely to become lost and fail completely in finding the target. Total travel distances across all eight trials strongly correlated (negatively) with neurocognitive measures and, for 49 participants who completed the Quality of Life Scale, psychosocial functioning.

CONCLUSION

Single-trial, goal-directed navigation in a naturalistic virtual environment is a functionally meaningful measure of cognitive functioning in schizophrenia.

Addiction Research Centres and the Nurturing of Creativity. Substance abuse research in a modern health care centre: the case of the Centre for Addiction and Mental Health

The Centre for Addiction and Mental Health is one of the premier centres for research related to substance use and addiction. This research began more than 50 years ago with the Addiction Research Foundation (ARF), an organization that contributed significantly to knowledge about the aetiology, treatment and prevention of substance use, addiction and related harm. After the merger of the ARF with three other institutions in 1998, research on substance use continued, with an additional focus on comorbid substance use and other mental health disorders. In the present paper, we describe the structure of funding and organization and selected current foci of research. We argue for the continuation of this successful model of integrating basic, epidemiological, clinical, health service and prevention research under the roof of a health centre.

Impairment of the tyrosine hydroxylase neuronal network in the orbitofrontal cortex of a genetically modified mouse model of schizophrenia

Important genes have been identified that are associated with susceptibility to schizophrenia. DISC1 is one of these candidate genes. The protein 14-3-3 epsilon is a DISC1-interacting molecule and is associated with axon elongation. The genetically modified 14-3-3 epsilon heterozygous knockout mice are considered to be an animal model of schizophrenia because they present endophenotypes of schizophrenia including working memory impairment. This study investigated the immunohistochemical expression of tyrosine hydroxylase (TH) to reveal the alterations in the functional structure of the axon elongation caused by the deficit of 14-3-3 epsilon. The study focused on the orbitofrontal cortex in the prefrontal cortex which is a region of interest in schizophrenia research. The investigation used eight 15-week-old knockout mice and six age-matched wild-type mice. The TH immunopositive fibers were linear and dense in the wild-type mice. These fibers were serpentine, thin and short in the knockout mice. Although it appeared that dendritic spine-like immunopositive varices were strung tightly in the fibers of wild-type mice, these were few and sparse in those of the of the knockout mice. Quantitative analysis showed a significant decrease in the total extent of the TH-immunopositive fibers in the orbital cortex of the knockout mouse. There is thought to be a dysfunction of a neurotransmitter such as dopamine and noradrenalin in the prefrontal cortex of these knockout mice.

Impaired NMDA receptor transmission alters striatal synapses and DISC1 protein in an age-dependent manner

NMDA receptors are key regulators of synaptic plasticity, and their hypofunction is thought to contribute to the pathophysiology of CNS disorders. Furthermore, NMDA receptors participate in the formation, maintenance, and elimination of synapses. The consequences of NMDA receptor hypofunction on synapse biology were explored in a genetic mouse model, in which the levels of NMDA receptors are reduced to 10% of normal levels (i.e., NR1-knockdown mice). In these mice, synapse number is reduced in an age-dependent manner; reductions are observed at the postpubertal age of 6 wk, but normal at 2 wk of age. Efforts to uncover the biochemical underpinnings of this phenomenon reveal synapse-specific reductions in 14-3-3ε protein and in Disrupted in Schizophrenia-1 (DISC1), two schizophrenia susceptibility factors that have been implicated in the regulation of spine density. Subchronic administration of MK-801, an NMDA receptor antagonist, produces similar synaptic reductions in both spine density and DISC1, indicating that synaptic levels of DISC1 are regulated by NMDA receptor function. The synaptic reduction of DISC1 and 14-3-3ε is developmentally correlated with the age-dependent decrease in striatal spine density.

SRD5A2 is associated with increased cortisol metabolism in schizophrenia spectrum disorders

OBJECTIVE

Dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis is documented in bipolar disorder and schizophrenia, but the mechanism is unclear; recently, increased activity of cortisol metabolizing enzymes was indicated in these disorders. We investigated whether five genes involved in cortisol metabolism were associated with altered activity of cortisol metabolizing enzymes in bipolar disorder (BD) and schizophrenia spectrum disorders (SCZ).

METHODS

A case-control sample of subjects with BD (N=213), SCZ (N=274) and healthy controls (N=370) from Oslo, Norway, were included and genotyped from 2003 to 2008. A sub-sample (healthy controls: N=151; SCZ: N=40; BD: N=39) had estimated enzyme activities based on measurements of urinary free cortisol, urinary free cortisone and metabolites. A total of 102 single nucleotide polymorphisms (SNPs) in the SRD5A1, SRD5A2, AKR1D1, HSD11B1 and HSD11B2 genes were genotyped, and significant SNPs analyzed in the sub-sample.

RESULTS

There was a significant association of rs6732223 in SRD5A2 (5α-reductase) with SCZ (p=0.0043, Bonferroni corrected p=0.030, T risk allele). There was a significantly increased 5α-reductase activity associated with rs6732223 (T allele) within the SCZ group (p=0.011).

CONCLUSIONS

The present data suggest an interaction between SCZ and SRD5A2 variants coding for the enzyme 5α-reductase, giving rise to increased 5α-reductase activity in SCZ. The findings may have implications for cortisol metabolizing enzymes as possible drug targets.

Evidence that putative ADHD low risk alleles at SNAP25 may increase the risk of schizophrenia

Synaptosomal Associated Protein 25 kDa (SNAP25) has been implicated in the pathogenesis of schizophrenia by numerous neuropathological studies and genetic variation at SNAP25 has been reported to be associated with ADHD. Expression levels of the putative schizophrenia susceptibility gene DTNBP1 has been shown to influence the levels of SNAP25 in vitro. We undertook directed mutation screening of SNAP25 in UK schizophrenic cases followed by direct association analysis of all variants identified and identified known exonic SNPs that showed evidence for association (rs3746544 P = 0.004 OR = 1.26, rs8636 P = 0.003 OR = 1.27), although these SNPs are highly correlated (r(2) > 0.99). We additionally genotyped a further 31 tag SNPs spanning the SNAP25 locus and identified several independent SNPs that were nominally associated with schizophrenia (strongest association at rs3787283, P = 0.006, OR = 1.25) however, due to the number of tests performed no SNP met experiment-wise significance (minimum permuted P-value = 0.1). Post hoc analysis revealed that the SNPs nominally associated with schizophrenia (rs3787283, rs3746544) were the same as those previously demonstrated to be associated with ADHD but with the opposite alleles, allowing the intriguing hypothesis that genetic variation at SNAP25 may be differentially associated with both schizophrenia and ADHD.

Family-based association of YWHAH in psychotic bipolar disorder

YWHAH is a positional and functional candidate gene for both schizophrenia and bipolar disorder (BP). This gene has been previously shown to be associated with both disorders, and the chromosome location (22q12.3) has been repeatedly implicated in linkage studies for these disorders. It codes for the eta subtype of the 14-3-3 protein family, is expressed mainly in brain, and is involved in HPA axis regulation. We investigated the association of YWHAH with BP in a large sample, consisting of 1211 subjects from 318 nuclear families including 554 affected offspring. We tested for association with the standard BP phenotype as well as subtypes defined by psychotic and mood-incongruent features. We genotyped five tag SNPs and the (GCCTGCA)(n) polymorphic locus present in this gene. Using a family-based association test, we found that rs2246704 was associated with BP (OR 1.31, P = 0.03) and psychotic BP (OR = 1.66, P = 0.002). The polymorphic repeat and two other SNPs were also modestly associated with psychotic BP. We have provided additional evidence for association of variants in YWHAH with major mental illness. Additional association analyses of larger sample sets will be required to clarify the role of YWHAH in schizophrenia and BP. The use of clinical sub-phenotypes such as psychotic features or other potential schizophrenia/BP overlap variables including cognitive abnormalities and poor functioning might shed further light on the potential subtypes of illness most closely associated with genetic variation in YWHAH.

Animal models of gene-environment interactions in schizophrenia

The pathogenesis of schizophrenia and related mental illnesses likely involves multiple interactions between susceptibility genes of small effects and environmental factors. Gene-environment interactions occur across different stages of neurodevelopment to produce heterogeneous clinical and pathological manifestations of the disease. The main obstacle for mechanistic studies of gene-environment interplay has been the paucity of appropriate experimental systems for elucidating the molecular pathways that mediate gene-environment interactions relevant to schizophrenia. Recent advances in psychiatric genetics and a plethora of experimental data from animal studies allow us to suggest a new approach to gene-environment interactions in schizophrenia. We propose that animal models based on identified genetic mutations and measurable environment factors will help advance studies of the molecular mechanisms of gene-environment interplay.

Proteomic analysis of rat brains following exposure to electroconvulsive therapy

Electroconvulsive therapy (ECT) is one of the most effective treatments used in psychiatry to date. The mechanisms of ECT action, however, are the least understood and still unclear. As a tool to elucidate the mechanisms of action of ECT, we employed proteomic analysis based on the identification of differentially expressed proteins after exposure to repeated ECT in rat brains. The expression of proteins was visualized by silver stain after two-dimensional gel electrophoresis. Of 24 differentially expressed protein spots (p<0.05 by Student t-test), six different proteins from 7 spots were identified by matrix-assisted laser desorption/ionization time-of flight (MALDI-TOF)/mass spectrometry. Among the identified proteins, there were five dominantly expressed proteins in the ECT-treated rat brain tissues (p<0.05); S100 protein beta chain, 14-3-3 protein zeta/delta, similar to ubiquitin-like 1 (sentrin) activating enzyme subunit 1, suppressor of G2 allele of SKP1 homolog, and phosphatidylinositol transfer protein alpha. The expression of only one protein, ACY1 protein, was repressed (p<0.05). These findings likely serve for a better understanding of mechanisms involved in the therapeutic effects of ECT.

Target identification for CNS diseases by transcriptional profiling

Gene expression changes in neuropsychiatric and neurodegenerative disorders, and gene responses to therapeutic drugs, provide new ways to identify central nervous system (CNS) targets for drug discovery. This review summarizes gene and pathway targets replicated in expression profiling of human postmortem brain, animal models, and cell culture studies. Analysis of isolated human neurons implicates targets for Alzheimer's disease and the cognitive decline associated with normal aging and mild cognitive impairment. In addition to tau, amyloid-beta precursor protein, and amyloid-beta peptides (Abeta), these targets include all three high-affinity neurotrophin receptors and the fibroblast growth factor (FGF) system, synapse markers, glutamate receptors (GluRs) and transporters, and dopamine (DA) receptors, particularly the D2 subtype. Gene-based candidates for Parkinson's disease (PD) include the ubiquitin-proteosome system, scavengers of reactive oxygen species, brain-derived neurotrophic factor (BDNF), its receptor, TrkB, and downstream target early growth response 1, Nurr-1, and signaling through protein kinase C and RAS pathways. Increasing variability and decreases in brain mRNA production from middle age to old age suggest that cognitive impairments during normal aging may be addressed by drugs that restore antioxidant, DNA repair, and synaptic functions including those of DA to levels of younger adults. Studies in schizophrenia identify robust decreases in genes for GABA function, including glutamic acid decarboxylase, HINT1, glutamate transport and GluRs, BDNF and TrkB, numerous 14-3-3 protein family members, and decreases in genes for CNS synaptic and metabolic functions, particularly glycolysis and ATP generation. Many of these metabolic genes are increased by insulin and muscarinic agonism, both of which are therapeutic in psychosis. Differential genomic signals are relatively sparse in bipolar disorder, but include deficiencies in the expression of 14-3-3 protein members, implicating these chaperone proteins and the neurotransmitter pathways they support as possible drug targets. Brains from persons with major depressive disorder reveal decreased expression for genes in glutamate transport and metabolism, neurotrophic signaling (eg, FGF, BDNF and VGF), and MAP kinase pathways. Increases in these pathways in the brains of animals exposed to electroconvulsive shock and antidepressant treatments identify neurotrophic and angiogenic growth factors and second messenger stimulation as therapeutic approaches for the treatment of depression.

No association between tagging SNPs of SNARE complex genes (STX1A, VAMP2 and SNAP25) and schizophrenia in a Japanese population

Abnormalities in neural connections and the neurotransmitter system appear to be involved in the pathophysiology of schizophrenia. The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, which consists of Syntaxin1A, vesicle-associated membrane protein 2 (VAMP2) and synaptosomal-associated protein 25 kDa (SNAP25), plays an important role in the neurotransmitter system, and is therefore an attractive place to search for candidate genes for schizophrenia. We conducted a two-stage genetic association analysis of Syntaxin1A (STX1A), VAMP2 and SNAP25 genes with schizophrenia (first-set screening samples: 377 cases and 377 controls, second-set confirmation samples: 657 cases and 527 controls). Based on the linkage disequilibrium, 40 SNPs (STX1A, 8 SNPs; VAMP2, 3 SNPs; SNAP25, 29 SNPs) were selected as 'tagging SNPs'. Only nominally significant associations of an SNP (rs12626080) and haplotype (rs363014 and rs12626080) in SNAP25 were detected in the first-set screening scan. To validate this significance, we carried out a replication analysis of these SNP and haplotype associations in second-set samples with a denser set of markers (including five additional SNPs). However, these associations could not be confirmed in the second-set analysis. These results suggest that the SNARE complex-related genes do not play a major role in susceptibility to schizophrenia in the Japanese population.

Associations of SNAP-25 polymorphisms with cognitive dysfunctions in Caucasian patients with schizophrenia during a brief trail of treatment with atypical antipsychotics

The synaptosomal-associated protein of 25 kDa (SNAP-25) is part of the soluble N-ethylmaleimide-sensitive fusion protein (NSF) attachment receptor (SNARE), which mediates synaptic neurotransmission. In earlier studies a possible involvement of this protein in schizophrenia has been shown. As neurocognitive impairment is a core feature in the pathology of schizophrenia and considered to be a putative endophenotype according to genetic studies we investigated the influences of different SNAP-25 polymorphisms on neuropsychological test results before and during treatment with atypical antipsychotics. A total of 104 schizophrenic patients treated with atypical antipsychotics were genotyped for three different polymorphisms of the SNAP-25 gene (MnlI, TaiI and DdeI in the 3'-UTR). Cognitive function was assessed at baseline, week 4 or 6 and week 8 or 12. Results of individual neuropsychological tests were assigned to six cognitive domains (reaction time and quality; executive function; working, verbal and visual memory) and a general cognitive index. The MnlI and TaiI polymorphisms showed no associations to deficits on neuropsychological test results. In contrast, we observed a significant relation between the DdeI polymorphism of the SNAP-25 gene and cognitive dysfunctions. Homozygote T/T allele carriers of the DdeI polymorphism showed significant better neuropsychological test results in cognitive domains verbal memory and executive functions than those with the combined T/C and C/C genotypes (P < 0.01) at all three time points, but no differences in response to treatment with atypical antipsychotics. Additionally, TT carriers exhibited significantly better results in a general cognitive index (P < 0.05). As we observed an association between the DdeI polymorphism of the SNAP-25 gene and cognitive dysfunctions of schizophrenic patients our finding suggests that the SNAP-25 gene could play a role in the pathophysiology of neurocognitive dysfunctions in schizophrenia but is not predictive for treatment response with atypical antipsychotics.

The DISC locus in psychiatric illness

The DISC locus is located at the breakpoint of a balanced t(1;11) chromosomal translocation in a large and unique Scottish family. This translocation segregates in a highly statistically significant manner with a broad diagnosis of psychiatric illness, including schizophrenia, bipolar disorder and major depression, as well as with a narrow diagnosis of schizophrenia alone. Two novel genes were identified at this locus and due to the high prevalence of schizophrenia in this family, they were named Disrupted-in-Schizophrenia-1 (DISC1) and Disrupted-in-Schizophrenia-2 (DISC2). DISC1 encodes a novel multifunctional scaffold protein, whereas DISC2 is a putative noncoding RNA gene antisense to DISC1. A number of independent genetic linkage and association studies in diverse populations support the original linkage findings in the Scottish family and genetic evidence now implicates the DISC locus in susceptibility to schizophrenia, schizoaffective disorder, bipolar disorder and major depression as well as various cognitive traits. Despite this, with the exception of the t(1;11) translocation, robust evidence for a functional variant(s) is still lacking and genetic heterogeneity is likely. Of the two genes identified at this locus, DISC1 has been prioritized as the most probable candidate susceptibility gene for psychiatric illness, as its protein sequence is directly disrupted by the translocation. Much research has been undertaken in recent years to elucidate the biological functions of the DISC1 protein and to further our understanding of how it contributes to the pathogenesis of schizophrenia. These data are the main subject of this review; however, the potential involvement of DISC2 in the pathogenesis of psychiatric illness is also discussed. A detailed picture of DISC1 function is now emerging, which encompasses roles in neurodevelopment, cytoskeletal function and cAMP signalling, and several DISC1 interactors have also been defined as independent genetic susceptibility factors for psychiatric illness. DISC1 is a hub protein in a multidimensional risk pathway for major mental illness, and studies of this pathway are opening up opportunities for a better understanding of causality and possible mechanisms of intervention.

Increases in expression of 14-3-3 eta and 14-3-3 zeta transcripts during neuroprotection induced by delta9-tetrahydrocannabinol in AF5 cells

The molecular mechanisms involved in N-methyl-D-aspartate (NMDA)-induced cell death and Delta9-tetrahydrocannabinol (THC)-induced neuroprotection were investigated in vitro with an AF5 neural progenitor cell line model. By microarray analysis, Ywhah, CK1, Hsp60, Pdcd 4, and Pdcd 7 were identified as being strongly regulated by both NMDA toxicity and THC neuroprotection. The 14-3-3 eta (14-3-3eta; gene symbol Ywhah) and 14-3-3 zeta (14-3-3zeta; gene symbol Ywhaz) transcripts were deceased by NMDA treatment and increased by THC treatment prior to NMDA, as measured by cDNA microarray analysis and quantitative real-time RT-PCR. Other 14-3-3 isoforms were unchanged. Whereas up-regulation of 14-3-3zeta expression was observed 30 min after treatment with THC plus NMDA, down-regulation by NMDA alone was not seen until 16 hr after treatment. By Western blotting, THC increased 14-3-3 protein only in cells that were also treated with NMDA. Overexpression of 14-3-3eta or 14-3-3zeta by transient plasmid transfection increased 14-3-3 protein levels and decreased NMDA-induced cell death. These data suggest that increases in 14-3-3 proteins mediate THC-induced neuroprotection under conditions of NMDA-induced cellular stress.

GLT-1 down-regulation induced by clozapine in rat frontal cortex is associated with synaptophysin up-regulation

In rat frontal cortex, extracellular levels of glutamate are raised by the anti-psychotic drug clozapine. We have recently shown that a significant reduction in the levels of the glutamate transporter GLT-1 may be one of the mechanisms responsible for this elevation. Here we studied whether GLT-1 down-regulation induced by chronic clozapine treatment is associated with changes in the expression of synaptophysin, synaptosome-associated protein of 25 kDa (SNAP-25) and vesicular glutamate transporter 1 (VGLUT1), three major presynaptic proteins involved in neurotransmitter release. Quantitative high-resolution confocal microscopy studies in vivo showed that GLT-1 down-regulation is closely associated with a significant increase in synaptophysin, but not SNAP-25 and VGLUT1, expression. This was confirmed in vitro studies, and in western blotting studies of synaptophysin, SNAP-25 and VGLUT1. In addition, our results show that, following clozapine treatment, synaptophysin expression increases in the very cortical regions in which GLT-1 expression is down-regulated. These findings suggest that part of the effects of clozapine may be exerted via an action on the presynaptic machinery involved in neurotransmitter release.

Critical appraisal of DNA microarrays in psychiatric genomics

Transcriptome profiling using DNA microarrays are data-driven approaches with the potential to uncover unanticipated relationships between gene expression alterations and psychiatric disorders. Studies to date have yielded both convergent and divergent findings. Differences may be explained, at least in part, by the use of a variety of microarray platforms and analytical approaches. Consistent findings across studies suggest, however, that important relationships may exist between altered gene expression and genetic susceptibility to psychiatric disorders. For example, GAD67, RGS4, DTNBP1, NRG1, and GABRAB2 show expression alterations in the postmortem brain of subjects with schizophrenia, and these genes have been also implicated as putative, heritable schizophrenia susceptibility genes. Thus, we propose that for some genes, altered expression in the postmortem human brain may have a dual origin: polymorphisms in the candidate genes themselves or upstream genetic-environmental factors that converge to alter their expression level. We hypothesize that certain gene products, which function as "molecular hubs," commonly show altered expression in psychiatric disorders and confer genetic susceptibility for one or more diseases. Microarray gene expression studies are ideally suited to reveal these putative disease-associated molecular hubs and to identify promising candidates for genetic association studies.

Fibroblast growth factor receptor signaling affects development and function of dopamine neurons - inhibition results in a schizophrenia-like syndrome in transgenic mice

Developing and mature midbrain dopamine (DA) neurons express fibroblast growth factor (FGF) receptor-1 (FGFR1). To determine the role of FGFR1 signaling in the development of DA neurons, we generated transgenic mice expressing a dominant negative mutant [FGFR1(TK-)] from the catecholaminergic, neuron-specific tyrosine hydroxylase (TH) gene promoter. In homozygous th(tk-)/th(tk-) mice, significant reductions in the size of TH-immunoreactive neurons were found in the substantia nigra compacta (SNc) and the ventral tegmental area (VTA) at postnatal days 0 and 360. Newborn th(tk-)/th(tk-) mice had a reduced density of DA neurons in both SNc and VTA, and the changes in SNc were maintained into adulthood. The reduced density of DA transporter in the striatum further demonstrated an impaired development of the nigro-striatal DA system. Paradoxically, the th(tk-)/th(tk-) mice had increased levels of DA, homovanilic acid and 3-methoxytyramine in the striatum, indicative of excessive DA transmission. These structural and biochemical changes in DA neurons are similar to those reported in human patients with schizophrenia and, furthermore, these th(tk-)/th(tk-) mice displayed an impaired prepulse inhibition that was reversed by a DA receptor antagonist. Thus, this study establishes a new developmental model for a schizophrenia-like disorder in which the inhibition of FGF signaling leads to alterations in DA neurons and DA-mediated behavior.

Transmission disequilibrium test provides evidence of association between promoter polymorphisms in 22q11 gene DGCR14 and schizophrenia

Recent research has suggested that the DiGeorge syndrome critical region gene 14 (DGCR14) exhibits activity differences of more than 1.5 fold between the haplotypes of the variants in the promoter region. DGCR14 is located at 22q11.21, an acknowledged region for susceptibility to schizophrenia. To test the hypothesis that DGCR14 may be involved in the etiology of the disease, we carried out a family-based association study between the reported functional markers and schizophrenia in 235 Chinese Han trios. We found significant evidence of preferential transmission of the promoter variants of DGCR14 across all the trios (Best p-value = 0.00038, Global p-value = 0.0008). The positive results have suggested that DGCR14 is likely to play an important role in the etiology of schizophrenia in the Chinese Han population.

Human p53 tumor suppressor gene (TP53) and schizophrenia: case-control and family studies

The human p53 tumor suppressor gene (TP53) is considered as a candidate susceptibility gene for schizophrenia because of its functions in neurodevelopment. To test for an association between TP53 and schizophrenia, both the case-control study and the transmission disequilibrium test (TDT) were performed on genotype data from eight polymorphisms in TP53. Our samples included 286 Toronto schizophrenia cases and 264 controls, and 163 Portuguese nuclear families. In the Toronto case-control study significant differences of allele frequencies of the CAA Ins/Del (p=0.027) and the 16bp Ins/Del (p=0.022) were detected. In TDT analysis we found significant differences for transmission of the CAA Ins/Del (p=0.017) in Portuguese schizophrenia families. Haplotype analysis also showed a significant association between TP53 and schizophrenia. These results provide further evidence that TP53 may play a role in the pathogenesis of schizophrenia.

Genetic and post-mortem mRNA analysis of the 14-3-3 genes that encode phosphoserine/threonine-binding regulatory proteins in schizophrenia and bipolar disorder

BACKGROUND

Previous work with animal models of psychosis, human genetic studies, and human post-mortem gene expression studies implicate the 14-3-3 family of genes in schizophrenia. The 14-3-3 genes code for a family of proteins that bind to and regulate other proteins, and they modulate neurodevelopment, cell-division, signal transduction and gene transcription.

OBJECTIVE

To explore the role of five 14-3-3 isoforms (beta, gamma, epsilon, zeta, and eta) in schizophrenia by: (1) comparing mRNA levels in post-mortem brain from schizophrenic, bipolar and control subjects and (2) assessing genetic association with schizophrenia in both case-control and nuclear family samples.

METHODS

Quantitative PCR (q-PCR) was used to determine relative mRNA levels in dorsolateral prefrontal cortex (Brodmann's area 46) samples donated by the Stanley Medical Research Institute (SMRI). Selected SNPs were genotyped in all five isoforms for association analysis in both family and case-control samples.

RESULTS

No significant differences in 14-3-3 mRNA expression levels between the diagnostic groups were found. A significant genetic association with schizophrenia was found for the 14-3-3zeta isoform in a subset of nuclear families of British ancestry (TDT: chi(2)=7.2; df=1; p=0.0073), in the case-control sample overall (p=0.011), and in a subset of the case-control sample.

CONCLUSION

The results, in combination with other published evidence, suggest that further work is necessary to clarify what role the 14-3-3 genes may play in the etiology and pathogenesis of schizophrenia.

Cortical gene expression in the neonatal ventral-hippocampal lesion rat model

Schizophrenia is a chronic, debilitating psychotic illness of unknown etiology that has been the subject of many genetic studies. We studied the neonatal ventral-hippocampal lesioned rat as an animal model of schizophrenia in order to identify novel candidate genes for schizophrenia. Temporal and frontal cortices were assessed using cDNA microarrays for differences in mRNA expression associated with the lesion, haloperidol treatment and in two rat strains with differential sensitivity to the behavioural effects of the lesion. Genes that had altered expression levels as a result of the lesion, that were normalized by haloperidol treatment, and that differed between rat strains were selected. The pattern of differential transcription was confirmed with quantitative PCR for all six candidate genes: large conductance calcium-activated potassium channel, subfamily M, beta member 1 (Kcnmb1); doublecortex (dcx); adenylyl cyclase-associated protein 1 (CAP1); adenosine monophosphate deaminase 2-isoform L (AMPD2); malic enzyme 3, NADP(+)-dependent, mitochondrial (Me3); and aspartylglucosaminidase (AGA). None of these genes has been extensively studied in schizophrenia, and further work with post-mortem tissue and genetic studies are ongoing.

Altered expression of 14-3-3 genes in the prefrontal cortex of subjects with schizophrenia

Seven distinct 14-3-3 proteins are expressed in mammals. One of the 14-3-3 genes (eta) has been previously associated with decreased expression in the prefrontal cortex (PFC) of subjects with schizophrenia. DNA microarray analysis of the PFC of 10 subjects with schizophrenia and 10 matched controls indicated that the majority of 14-3-3 genes exhibited moderate to marked decreases in expression in schizophrenia, which were significant at the group level across all 10 comparisons (p<0.021). Selected changes in gene expression were further examined using in situ hybridization (ISH) in the same subject pairs as well as in four monkeys treated chronically with haloperidol and matched control animals. All analyses were performed blind to subject identity and diagnosis, or treatment. ISH analysis and multivariate analysis of covariance confirmed the significant decreases in expression of two 14-3-3 genes: beta -31.9%, zeta -18.2%. Two other 14-3-3 genes exhibited more modest decreases in expression levels that were significant only in pairwise comparisons that did not factor in post-mortem interval or tissue storage time: gamma -11.9%, eta -15.4%. In the PFC of haloperidol-treated monkeys, there was no difference in 14-3-3 zeta expression, while 14-3-3 beta increased 28% (p<0.05) as a result of neuroleptic treatment. Our results suggest that decreased expression of selected 14-3-3 genes is a common feature of schizophrenia and that the 14-3-3 beta transcript may be unique among the 14-3-3 genes in its increase in response to haloperidol and decrease in the disease state.

The SNAP-25 gene may be associated with clinical response and weight gain in antipsychotic treatment of schizophrenia

The synaptosomal-associated protein of 25 kDa (SNAP-25) is an essential component of the core complex that mediates presynaptic vesicle trafficking. Thus, SNAP-25 is directly involved in the release of neurotransmitters. Quantitative alterations of SNAP-25 expression have been reported in brain regions and cerebrospinal fluid (CSF) of schizophrenics and in haloperidol treated rats. This observed altered expression may be influenced by genetic variants of SNAP-25. We hypothesized that polymorphisms of the SNAP-25 gene (sites DdeI, MnlI and TaiI in the 3'UTR) are associated with antipsychotic drug response and induced weight gain. A sample of 59 patients with prior suboptimal response to antipsychotic treatment and diagnosed with DSM-IV schizophrenia or schizoaffective disorder was examined. Patients were administered clozapine, haloperidol, olanzapine or risperidone for up to 14 weeks. Clinical response was defined as the difference between the baseline and the endpoint total scores on the Positive and Negative Syndrome Scale (PANSS). Weight was assessed at baseline and at study endpoint. ANOVA revealed that the MnlI and TaiI polymorphisms were associated with response (F[2,53] = 4.57, p = 0.01 and F[2,52] = 3.53, p = 0.03) and with weight gain (F[2,52] = 4.28, p = 0.01 and F[2,51] = 3.38, p = 0.04). When covariates were included, the MnlI polymorphism remained significantly associated with changes of PANSS scores, but not with weight gain. The DdeI polymorphism was not associated with response or weight gain. These findings suggest that SNAP-25 gene variants affect clinical response in patients with prior poor response to antipsychotics. Weight changes do not seem to be associated with polymorphism of the SNAP-25 gene, however, replication in independent samples is warranted.

Association of 14-3-3 ε gene haplotype with completed suicide in Japanese

Genetic factors have been suggested to be involved in suicide. Although some genetic factors, such as serotonergic transduction, have been associated with suicide, the results are inconsistent. There is a possibility that various signaling anomalies are involved in the biological vulnerability to suicide. We carried out a genome-wide gene-expression study in the brains of suicide victims using DNA microarrays;14-3-3 epsilon, which is related to neurogenesis, was one of the genes upregulated in the brains of suicide victims in the microarray analysis. This was confirmed by Western blot analysis. To examine the possibility of the involvement of 14-3-3 epsilon in the pathogenesis of suicide, we investigated the association of the 14-3-3 epsilon gene and completed suicide. We used three high-frequency SNPs (rs1532976, rs3752826, and rs9393) and found a significant association of two alleles (rs1532976 and rs3752826) with completed suicide (p < 0.05). Moreover, the distribution of haplotype revealed a more significant difference between completed suicide and controls (p=0.0005). This finding suggests that 14-3-3 epsilon is a potential suicide susceptibility gene and implies that dysregulation of neurogenesis may be involved in suicide.

An empirical Bayesian significance test of cDNA library data

Automated high-throughput sequencing of cDNA clones from numerous libraries has generated a wealth of information about both genome sequence and relative transcript abundances. A common statistical challenge in the analysis of library sequences is to infer whether there is differential expression for the same transcript under two different conditions, such as normal and diseased tissue. In contrast to the continuously variable intensity measurements from microarray experiments, data from cDNA library sequencing presents itself as a discrete count of the incidence of some clone or transcript in a finite sample. In this paper, we first propose a statistical model for data generated from cDNA library sequencing efforts. The model is based on the Poisson mixed with generalized inverse Gaussian (PGIG), introduced by Sichel (1971, 1975). PGIG has been used in modeling population abundance, ecological studies, word frequencies in publications, etc. Using data from the literature, we show that the proposed model provides a good fit to the observed data. Using this new model for cDNA library data, we developed an empirical Bayesian significance test (EBST) for inferring the statistical significance of differential gene expression from discrete data.

A family-based association study of schizophrenia with polymorphisms at three candidate genes

Clinical researches have shown that there is a genetic contribution to the pathogenesis of schizophrenia. Recent studies have suggested that three genes neuropeptide Y (NPY), phosphoinositide-3-kinase class 3 (PIK3C3) and 14-3-3 eta chain gene (YWHAH) are probably associated with schizophrenia. To replicate these findings, we carried out a family-based study on a sample of 235 trios. Our results suggest that the polymorphisms at the NPY and YWHAH genes are unlikely to be linked with genetic susceptibility to schizophrenia. However, we found significant evidence of preferential transmission of the -432C allele of the PIK3C3 gene in the entire trios (Z=2.91, d.f.=1, P=0.0036) and the male probands trios (Z=2.66, d.f.=1, P=0.0079).

From genomics to proteomics: new directions in molecular neuropsychiatry

Neuropsychiatry, like many other biomedical sciences, has been revolutionized by the advances in genomic technologies over the years. The advent of PCR (polymerase chain reaction) and the sequencing of the human genome have provided invaluable insights into the molecular genetics of the various psychiatric disorders through the study of candidate genes and linkage analyses. However, biological phenotype is dictated by protein expression, which has been shown to stray from the genetic blueprint designated by the genome. Consequently, the field of proteomics has recently emerged as a powerful means of exploring protein structure, function, and expression patterns. The ability to study disease at the gene and protein levels presents a tremendous opportunity for neuropsychiatric research, particularly in terms of the potential for developing therapeutic agents for novel protein targets.

Molecular fingerprinting of TGFß-treated embryonic maxillary mesenchymal cells

The transforming growth factor-beta (TGF(beta)) family represents a class of signaling molecules that plays a central role in normal embryonic development, specifically in development of the craniofacial region. Members of this family are vital to development of the secondary palate where they regulate maxillary and palate mesenchymal cell proliferation and extracellular matrix synthesis. The function of this growth factor family is particularly critical in that perturbation of either process results in a cleft of the palate. While the cellular and phenotypic effects of TGF(beta) on embryonic craniofacial tissue have been extensively cataloged, the specific genes that function as downstream mediators of TGF(beta) in maxillary/palatal development are poorly defined. Gene expression arrays offer the ability to conduct a rapid, simultaneous assessment of hundreds to thousands of differentially expressed genes in a single study. Inasmuch as the downstream sequelae of TGF(beta) action are only partially defined, a complementary DNA (cDNA) expression array technology (Clontech's Atlas Mouse cDNA Expression Arrays), was utilized to delineate a profile of differentially expressed genes from TGF(beta)-treated primary cultures of murine embryonic maxillary mesenchymal cells. Hybridization of a membrane-based cDNA array (1178 genes) was performed with 32P-labeled cDNA probes synthesized from RNA isolated from either TGF(beta)-treated or vehicle-treated embryonic maxillary mesenchymal cells. Resultant phosphorimages were subject to AtlasImage analysis in order to determine differences in gene expression between control and TGF(beta)-treated maxillary mesenchymal cells. Of the 1178 arrayed genes, 552 (47%) demonstrated detectable levels of expression. Steady state levels of 22 genes were up-regulated, while those of 8 other genes were down-regulated, by a factor of twofold or greater in response to TGF(beta). Affected genes could be grouped into three general functional categories: transcription factors and general DNA-binding proteins; growth factors/signaling molecules; and extracellular matrix and related proteins. The extent of hybridization of each gene was evaluated by comparison with the abundant, constitutively expressed mRNAs: ubiquitin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ornithine decarboxylase (ODC), cytoplasmic beta-actin and 40S ribosomal protein. No detectable changes were observed in the expression levels of these genes in-response to TGF(beta) treatment. Gene expression profiling results were verified by Real-Time quantitative polymerase chain reaction. Utilization of cDNA microarray technology has enabled us to delineate a preliminary transcriptional map of TGF(beta) responsiveness in embryonic maxillary mesenchymal cells. The profile of differentially expressed genes offers revealing insights into potential molecular regulatory mechanisms employed by TGF(beta) in orchestrating craniofacial ontogeny.

Schizophrenia: from phenomenology to neurobiology

Schizophrenia is a common and debilitating illness, characterized by chronic psychotic symptoms and psychosocial impairment that exact considerable human and economic costs. The literature in electronic databases as well as citations and major articles are reviewed with respect to the phenomenology, pathology, treatment, genetics and neurobiology of schizophrenia. Although studied extensively from a clinical, psychological, biological and genetic perspective, our expanding knowledge of schizophrenia provides only an incomplete understanding of this complex disorder. Recent advances in neuroscience have allowed the confirmation or refutation of earlier findings in schizophrenia, and permit useful comparisons between the different levels of organization from which the illness has been studied. Schizophrenia is defined as a clinical syndrome that may include a collection of diseases that share a common presentation. Genetic factors are the most important in the etiology of the disease, with unknown environmental factors potentially modulating the expression of symptoms. Schizophrenia is a complex genetic disorder in which many genes may be implicated, with the possibility of gene-gene interactions and a diversity of genetic causes in different families or populations. A neurodevelopmental rather than degenerative process has received more empirical support as a general explanation of the pathophysiology, although simple dichotomies are not particularly helpful in such a complicated disease. Structural brain changes are present in vivo and post-mortem, with both histopathological and imaging studies in overall agreement that the temporal and frontal lobes of the cerebral cortex are the most affected. Functional imaging, neuropsychological testing and clinical observation are also generally consistent in demonstrating deficits in cognitive ability that correlate with abnormalities in the areas of the brain with structural abnormalities. The dopamine and other neurotransmitter systems are certainly involved in the treatment or modulation of psychotic symptoms. These broad findings represent the distillation of a large body of disparate data, but firm and specific findings are sparse, and much about schizophrenia remains unknown.