Schizophrenia susceptibility genes directly implicated in the life cycles of pathogens: cytomegalovirus, influenza, herpes simplex, rubella, and Toxoplasma gondii

Beyond the association. Toxoplasma gondii in schizophrenia, bipolar disorder, and addiction: systematic review and meta-analysis

OBJECTIVE

To perform a meta-analysis on studies reporting prevalence of Toxoplasma gondii (T. gondii) infection in any psychiatric disorder compared with healthy controls. Our secondary objective was to analyze factors possibly moderating heterogeneity.

METHOD

A systematic search was performed to identify studies into T. gondii infection for all major psychiatric disorders versus healthy controls. Methodological quality, publication bias, and possible moderators were assessed.

RESULTS

A total of 2866 citations were retrieved and 50 studies finally included. Significant odds ratios (ORs) with IgG antibodies were found in schizophrenia (OR 1.81, P < 0.00001), bipolar disorder (OR 1.52, P = 0.02), obsessive-compulsive disorder (OR 3.4, P < 0.001), and addiction (OR 1.91, P < 0.00001), but not for major depression (OR 1.21, P = 0.28). Exploration of the association between T. gondii and schizophrenia yielded a significant effect of seropositivity before onset and serointensity, but not IgM antibodies or gender. The amplitude of the OR was influenced by region and general seroprevalence. Moderators together accounted for 56% of the observed variance in study effects. After controlling for publication bias, the adjusted OR (1.43) in schizophrenia remained significant.

CONCLUSION

These findings suggest that T. gondii infection is associated with several psychiatric disorders and that in schizophrenia reactivation of latent T. gondii infection may occur.

Maternal exposure to sexually transmitted infections and schizophrenia among offspring

Animal models and epidemiologic studies suggest that prenatal maternal infection, and sexually transmitted infection (STI) in particular, is associated with an increased risk of schizophrenia in the offspring. However, findings from prior research studies on common infections, including herpes simplex virus type 2 (HSV-2) and Chlamydia trachomatis (C. trachomatis) have been inconsistent. To investigate these associations, we conducted a case-control study nested in the population-based Finnish Prenatal Study of Schizophrenia. Using linked national registries, 963 cases with schizophrenia (ICD-10 F20) or schizoaffective disorder (ICD-10 F25), and 963 matched controls were identified from among all persons born between 1983 and 1998 in Finland. HSV-2 IgG antibody levels were quantified in archived maternal serum samples drawn during pregnancy. Mothers of 16.4% of cases versus 12.6% of controls were HSV-2 seropositive. Mean levels of maternal HSV-2 IgG were marginally higher among cases than controls (index values of 0.98 versus 0.86; p=0.06). The unadjusted odds ratio (OR) of maternal HSV-2 IgG seropositivity was 1.33 (95% confidence interval (CI)=1.03-1.72, p=0.03). Following adjustment for covariates, the relationship was attenuated (OR=1.22, CI=0.93-1.60; p=0.14). In an exploratory analysis of another STI, C. trachomatis antibodies were measured in a subsample of 207 case-control pairs drawn from the cohort. The proportions of subjects that were seropositive and the mean levels of C. trachomatis antibodies were similar for cases and controls. This study does not support a strong association of HSV-2 or C. trachomatis IgG antibodies in maternal serum during early to mid-gestation with the development of schizophrenia in the offspring.

Role of T helper lymphokines in the immune-inflammatory pathophysiology of schizophrenia: Systematic review and meta-analysis

BACKGROUND

Schizophrenia is highly complex multifactorial psychiatric disorder with poorly defined etiopathophysiology, which also has manifestations in the immune system.

AIMS

The aim of this review is to meta-analyze the available evidence regarding the role of immune activation indicated by the T helper cells in order to evaluate etiopathophysiological links between the immune system and schizophrenia.

METHODS

A literature search was performed in multiple electronic databases for relevant research papers published between 1990 and May 2014. Meta-analyses were conducted under both random- (REM) and fixed-effect models (FEM) by calculating weighted mean differences with 95% confidence intervals. Heterogeneity was assessed with the I(2) index.

RESULTS

Twenty-one studies were selected after observing inclusion and exclusion criteria. In vitro interferon-gamma (INF-γ) and interleukin (IL)-2 production was significantly lower in the schizophrenic patients compared with non-schizophrenic control individuals under both FEM and REM. Serum levels of IL-2 and serum/in vitro IL-4 were not significantly different in both groups under both FEM and REM. Overall Th1:Th2 ratio (INF-γ:IL-4 and IL-2:IL-4) in the serum samples was significantly deflected towards Th2 under both models in the serum samples (- 0.33 [- 0.59 to - 0.06]; P < 0.03, FEM and - 2.44 [- 4.27 to - 0.60]; P < 0.009, REM) but in vitro production Th1:Th2 ratio (INF-γ:IL-4 and IL-2:IL-4) was deflected towards Th1 under both the models (1.11 [0.45-1.78]; P < 0.002, FEM and 6.68 [0.72-12.64]; P < 0.03, REM).

CONCLUSIONS

Whereas the Th1:Th2 ratio in the serum samples deflected towards T2, in vitro Th1:Th2 ratio favored Th1 when the individual study data were meta-analyzed.

Immune aging, dysmetabolism, and inflammation in neurological diseases

As we age, the immune system undergoes a process of senescence accompanied by the increased production of proinflammatory cytokines, a chronic subclinical condition named as “inflammaging”. Emerging evidence from human and experimental models suggest that immune senescence also affects the central nervous system and promotes neuronal dysfunction, especially within susceptible neuronal populations. In this review we discuss the potential role of immune aging, inflammation and metabolic derangement in neurological diseases. The discovery of novel therapeutic strategies targeting age-linked inflammation may promote healthy brain aging and the treatment of neurodegenerative as well as neuropsychiatric disorders.

Understanding schizophrenia as a disorder of consciousness: biological correlates and translational implications from quantum theory perspectives

From neurophenomenological perspectives, schizophrenia has been conceptualized as "a disorder with heterogeneous manifestations that can be integrally understood to involve fundamental perturbations in consciousness". While these theoretical constructs based on consciousness facilitate understanding the 'gestalt' of schizophrenia, systematic research to unravel translational implications of these models is warranted. To address this, one needs to begin with exploration of plausible biological underpinnings of "perturbed consciousness" in schizophrenia. In this context, an attractive proposition to understand the biology of consciousness is "the orchestrated object reduction (Orch-OR) theory" which invokes quantum processes in the microtubules of neurons. The Orch-OR model is particularly important for understanding schizophrenia especially due to the shared 'scaffold' of microtubules. The initial sections of this review focus on the compelling evidence to support the view that "schizophrenia is a disorder of consciousness" through critical summary of the studies that have demonstrated self-abnormalities, aberrant time perception as well as dysfunctional intentional binding in this disorder. Subsequently, these findings are linked with 'Orch-OR theory' through the research evidence for aberrant neural oscillations as well as microtubule abnormalities observed in schizophrenia. Further sections emphasize the applicability and translational implications of Orch-OR theory in the context of schizophrenia and elucidate the relevance of quantum biology to understand the origins of this puzzling disorder as "fundamental disturbances in consciousness".

ZNF804A Transcriptional Networks in Differentiating Neurons Derived from Induced Pluripotent Stem Cells of Human Origin

ZNF804A (Zinc Finger Protein 804A) has been identified as a candidate gene for schizophrenia (SZ), autism spectrum disorders (ASD), and bipolar disorder (BD) in replicated genome wide association studies (GWAS) and by copy number variation (CNV) analysis. Although its function has not been well-characterized, ZNF804A contains a C2H2-type zinc-finger domain, suggesting that it has DNA binding properties, and consequently, a role in regulating gene expression. To further explore the role of ZNF804A on gene expression and its downstream targets, we used a gene knockdown (KD) approach to reduce its expression in neural progenitor cells (NPCs) derived from induced pluripotent stem cells (iPSCs). KD was accomplished by RNA interference (RNAi) using lentiviral particles containing shRNAs that target ZNF804A mRNA. Stable transduced NPC lines were generated after puromycin selection. A control cell line expressing a random (scrambled) shRNA was also generated. Neuronal differentiation was induced, RNA was harvested after 14 days and transcriptome analysis was carried out using RNA-seq. 1815 genes were found to be differentially expressed at a nominally significant level (p<0.05); 809 decreased in expression in the KD samples, while 1106 increased. Of these, 370 achieved genome wide significance (FDR<0.05); 125 were lower in the KD samples, 245 were higher. Pathway analysis showed that genes involved in interferon-signaling were enriched among those that were down-regulated in the KD samples. Correspondingly, ZNF804A KD was found to affect interferon-alpha 2 (IFNA2)-mediated gene expression. The findings suggest that ZNF804A may affect a differentiating neuron’s response to inflammatory cytokines, which is consistent with models of SZ and ASD that support a role for infectious disease, and/or autoimmunity in a subgroup of patients.

Prenatal maternal immune disruption and sex-dependent risk for psychoses

BACKGROUND

Previous studies suggest that abnormalities in maternal immune activity during pregnancy alter the offspring's brain development and are associated with increased risk for schizophrenia (SCZ) dependent on sex.

METHOD

Using a nested case-control design and prospectively collected prenatal maternal sera from which interleukin (IL)-1β, IL-8, IL-6, tumor necrosis factor (TNF)-α and IL-10 were assayed, we investigated sex-dependent associations between these cytokines and 88 psychotic cases [SCZ = 44; affective psychoses (AP) = 44] and 100 healthy controls from a pregnancy cohort followed for > 40 years. Analyses included sex-stratified non-parametric tests adjusted for multiple comparisons to screen cytokines associated with SCZ risk, followed by deviant subgroup analyses using generalized estimating equation (GEE) models.

RESULTS

There were higher prenatal IL-6 levels among male SCZ than male controls, and lower TNF-α levels among female SCZ than female controls. The results were supported by deviant subgroup analyses with significantly more SCZ males with high IL-6 levels (>highest quartile) compared with controls [odd ratio (OR)75 = 3.33, 95% confidence interval (CI) 1.13-9.82], and greater prevalence of low TNF-α levels (<lowest quartile) among SCZ females compared with their controls (OR25 = 6.30, 95% CI 1.20-33.04) and SCZ males. Higher levels of IL-6 were only found among SCZ compared with AP cases. Lower TNF-α levels (non-significant) also characterized female AP cases versus controls, although the prevalence of the lowest levels was higher in SCZ than AP females (70% v. 40%), with no effect in SCZ or AP males.

CONCLUSIONS

The results underscore the importance of immunologic processes affecting fetal brain development and differential risk for psychoses depending on psychosis subtype and offspring sex.

Peptide sharing between influenza A H1N1 hemagglutinin and human axon guidance proteins

Epidemiologic data suggest that maternal microbial infections may cause fetal neurodevelopmental disorders, potentially increasing susceptibility to heavy psychopathologies such as schizophrenia, schizophreniform disorder, autism, pervasive developmental disorders, bipolar disorders, psychosis, epilepsy, language and speech disorders, and cognitive impairment in adult offspring. However, the molecular pathomechanisms underlying such a relationship are not clear. Here we analyze the potential role of the maternal immune response to viral infection in determining fetal brain injuries that increase the risk of neurological disorders in the adult. We use influenza infection as a disease model and human axon guidance pathway, a key process in the formation of neural network during midgestation, as a potential fetal target of immune insults. Specifically, we examined influenza A H1N1 hemagglutinin (HA), an antigenic viral protein, for amino acid sequence similarity to a random library of 188 axon guidance proteins. We obtain the results that (1) contrary to any theoretical expectations, 45 viral pentapeptide matches are distributed throughout a subset of 36 guidance molecules; (2) in 24 guidance proteins, the peptide sharing with HA antigen involves already experimentally validated influenza HA epitopes; and (3) most of the axon guidance vs HA peptide overlap is conserved among influenza A viral strains and subsets. Taken together, our data indicate that immune cross-reactivity between influenza HA and axon guidance molecules is possible and may well represent a pathologic mechanism capable of determining neurodevelopmental disruption in the fetus.

Autoimmunity, inflammation, and psychosis: a search for peripheral markers

Accumulating evidence supports the view that deregulation of the immune system represents an important vulnerability factor for psychosis. In a subgroup of psychotic patients, the high comorbidity with autoimmune and chronic inflammatory conditions suggests a common underlying immune abnormality leading to both conditions. The reviewed data of affective and nonaffective psychosis show that if immune biomarkers exist for such immune abnormality, they may be found in raised macrophage/monocyte inflammatory activation patterns (monocytosis, high-inflammatory gene expression, raised glucocorticoid receptor β/glucocorticoid receptor α ratio, and high levels of proinflammatory and anti-inflammatory monocyte/macrophage derived cytokines in serum/plasma), reduced T cell numbers/proliferation, and TH1 skewing. This activation of the inflammatory response system may be suggestive for microglia activation, as these cells are the macrophages of the brain. Indeed, there is some evidence of activation of the microglia as detected in positron emission tomography scans and in histopathology, and it is assumed that this activation disturbs the development and function of neuronal circuits in the brain. Further, animal models of psychotic conditions (maternal stress and inflammation paradigms) suggest that such monocyte/microglia activation could be seen as the result of a combination of genetic predisposition and an immune-mediated two-hit model. Infection but also environmental stressors during gestation/early life activate microglia, perturbing neuronal development, thereby setting the stage for vulnerability for later psychotic disorders. A second hit, such as endocrine changes, stress, or infection, could further activate microglia, leading to functional abnormalities of the neuronal circuitry in the brain and psychosis.

MicroRNA-206: a promising theranostic marker

MicroRNAs (miRs) are small non-coding RNAs that negatively regulate gene expression by binding to the 3` untranslated regions (3`UTR) of their target mRNAs. MiRs were shown to play pivotal roles in tissue development and function and are also involved in the pathogenesis of various diseases including cancer. MicroRNA-206, which belongs to the group of so-called "myomiRs", is one of the most studied miRs thus far. In addition to being involved in skeletal muscle development and pathology, it has also been established that it is involved in the pathogenesis of numerous diseases including heart failure, chronic obstructive pulmonary disease, Alzheimer's disease and various types of cancers. The aim of this review is to provide a complex overview of microRNA-206, including regulating its expression, a brief description of its known functions in skeletal muscle and a complex overview of its roles in the biology and pathology of other tissues, emphasizing its significant diagnostic and therapeutic potential.

Association between antibodies to multiple infectious and food antigens and new onset schizophrenia among US military personnel

INTRODUCTION

Multiple studies have documented immune activation in many individuals with schizophrenia suggesting that antigens capable of generating a prolonged immune response may be important environmental factors in many cases of this disorder. While existing studies have found single-agent associations of antibodies to food and neurotropic infectious agents with schizophrenia, a simultaneous examination of multiple agents may shed light on agent interactions or possible etiopathogenic pathways.

METHODS

We used traditional regression and novel statistical techniques to examine associations of single and combined infectious and food antigens with schizophrenia. We tested 6106 serum samples from 855 cases and 1165 matched controls.

RESULTS

Higher antibody levels to casein were borderline significant in the prediction of schizophrenia (HR=1.08, p=0.06). Study participants with higher cytomegalovirus (CMV) IgG antibody levels had a reduced risk of developing schizophrenia (HR=0.90; p=0.02). While IgG antibodies to gliadin, Toxoplasma gondii, vaccinia, measles, and human herpesvirus-6 (HHV-6) showed no significant independent associations with schizophrenia, the increase in antibody levels to several combinations of agents, to include casein, measles, CMV, T. gondii and vaccinia, was predictive of an 18-34% increase in the risk of developing schizophrenia.

CONCLUSION

Certain patterns of antibodies, involving some agents, were predictive of developing schizophrenia, with the magnitude of association rising when the level of antibodies increased to two or more agents. A heightened antibody response to a combination of several infectious/food antigens might be an indicator of an altered immune response to antigenic stimuli.

Differential correlations between inflammatory cytokines and psychopathology in veterans with schizophrenia: potential role for IL-17 pathway

Pro-inflammatory cytokines have been consistently reported to be elevated in schizophrenia patients. However, it is not known whether cytokines influence the presentation of psychotic symptoms. To address this issue, we evaluated the relationship between levels of inflammatory molecules and psychopathological parameters in patients with schizophrenia. We hypothesized that severity of symptoms would correlate with increased levels of inflammatory cytokines. Serum samples from 47 veterans with a diagnosis of schizophrenia and 20 healthy controls were tested for levels of 38 cytokines/chemokines involved in regulation of immune/inflammatory reactions using a Millipore multiplex bead array in a Luminex 100 system. We found significantly increased levels of GRO, MCP-1, MDC, and sCD40L, and significantly decreased levels of IFN-γ, IL-2, IL-12p70, and IL-17, in schizophrenia patients compared to controls. In addition, we observed positive correlations between levels of cytokines and the Positive and Negative Symptoms Scale (PANSS) scores in subjects with schizophrenia for G-CSF, IL-1β, IL1ra, IL-3, IL-6, IL-9, IL-10, sCD40L and TNF-β. Pathway analyses showed these cytokines to be part of the IL17 pathway. Using principal component analyses, we found the factor that included these cytokines and IL-17 to be associated with positive, general and total PANSS scores. These results suggest that alterations in this pathway may play a role in development of psychotic symptoms in schizophrenia.

DISC1 mouse models as a tool to decipher gene-environment interactions in psychiatric disorders

DISC1 was discovered in a Scottish pedigree in which a chromosomal translocation that breaks this gene segregates with psychiatric disorders, mainly depression and schizophrenia. Linkage and association studies in diverse populations support DISC1 as a susceptibility gene to a variety of neuropsychiatric disorders. Many Disc1 mouse models have been generated to study its neuronal functions. These mouse models display variable phenotypes, some of them relevant to schizophrenia, others to depression. The Disc1 mouse models are popular genetic models for studying gene-environment interactions in schizophrenia. Five different Disc1 models have been combined with environmental factors. The environmental stressors employed can be classified as either early immune activation or later social paradigms. These studies cover major time points along the neurodevelopmental trajectory: prenatal, early postnatal, adolescence, and adulthood. Various combinations of molecular, anatomical and behavioral methods have been used to assess the outcomes. Additionally, three of the studies sought to rescue the resulting abnormalities. Here we provide background on the environmental paradigms used, summarize the results of these studies combining Disc1 mouse models with environmental stressors and discuss what we can learn and how to proceed. A major question is how the genetic and environmental factors determine which psychiatric disorder will be clinically manifested. To address this we can take advantage of the many Disc1 models available and expose them to the same environmental stressor. The complementary experiment would be to expose the same model to different environmental stressors. DISC1 is an ideal gene for this approach, since in the Scottish pedigree the same chromosomal translocation results in different psychiatric conditions.

Human cytomegalovirus UL76 elicits novel aggresome formation via interaction with S5a of the ubiquitin proteasome system

HCMV UL76 is a member of a conserved Herpesviridae protein family (Herpes_UL24) that is involved in viral production, latency, and reactivation. UL76 presents as globular aggresomes in the nuclei of transiently transfected cells. Bioinformatic analyses predict that UL76 has a propensity for aggregation and targets cellular proteins implicated in protein folding and ubiquitin-proteasome systems (UPS). Furthermore, fluorescence recovery after photobleaching experiments suggests that UL76 reduces protein mobility in the aggresome, which indicates that UL76 elicits the aggregation of misfolded proteins. Moreover, in the absence of other viral proteins, UL76 interacts with S5a, which is a major receptor of polyubiquitinated proteins for UPS proteolysis via its conserved region and the von Willebrand factor type A (VWA) domain of S5a. We demonstrate that UL76 sequesters polyubiquitinated proteins and S5a to nuclear aggresomes in biological proximity. After knockdown of endogenous S5a by RNA interference techniques, the UL76 level was only minimally affected in transiently expressing cells. However, a significant reduction in the number of cells containing UL76 nuclear aggresomes was observed, which suggests that S5a may play a key role in aggresome formation. Moreover, we show that UL76 interacts with S5a in the late phase of viral infection and that knockdown of S5a hinders the development of both the replication compartment and the aggresome. In this study, we demonstrate that UL76 induces a novel nuclear aggresome, likely by subverting S5a of the UPS. Given that UL76 belongs to a conserved family, this underlying mechanism may be shared by all members of the Herpesviridae.

Future perspectives on the treatment of cognitive deficits and negative symptoms in schizophrenia

Drug discovery based on classic models for cognitive impairment and negative symptoms of schizophrenia have met with only modest success. Because cognitive impairment and negative symptoms may result from disruptions in neurodevelopment, more complex developmental models that integrate environmental and genetic risk factors are needed. In addition, it has become clear that biochemical pathways involved in schizophrenia form complex, interconnected networks. Points at which risk factors converge, such as brain-derived neurotrophic factor (BDNF) and protein kinase B (AKT), and from which processes involved in neuroplasticity diverge, are of particular interest for pharmacologic interventions. This paper reviews elements of neurodevelopmental models for cognitive deficits and negative symptoms of schizophrenia with the aim of identifying potential targets for interventions.

Variation in the major histocompatibility complex [MHC] gene family in schizophrenia: associations and functional implications

Schizophrenia is a chronic debilitating neuropsychiatric disorder with a complex genetic contribution. Although multiple genetic, immunological and environmental factors are known to contribute to schizophrenia susceptibility, the underlying neurobiological mechanism(s) is yet to be established. The immune system dysfunction theory of schizophrenia is experiencing a period of renewal due to a growth in evidence implicating components of the immune system in brain function and human behavior. Current evidence indicates that certain immune molecules such as Major Histocompatibility Complex (MHC) and cytokines, the key regulators of immunity and inflammation are directly involved in the neurobiological processes related to neurodevelopment, neuronal plasticity, learning, memory and behavior. However, the strongest support in favor of the immune hypothesis has recently emerged from on-going genome wide association studies advocating MHC region variants as major determinants of one's risk for developing schizophrenia. Further identification of the interacting partners and receptors of MHC molecules in the brain and their role in down-stream signaling pathways of neurotransmission have implicated these molecules as potential schizophrenia risk factors. More recently, combined brain imaging and genetic studies have revealed a relationship between genetic variations within the MHC region and neuromorphometric changes during schizophrenia. Furthermore, MHC molecules play a significant role in the immune-infective and neurodevelopmental pathogenetic pathways, currently hypothesized to contribute to the pathophysiology of schizophrenia. Herein, we review the immunological, genetic and expression studies assessing the role of the MHC in conferring risk for developing schizophrenia, we summarize and discuss the possible mechanisms involved, making note of the challenges to, and future directions of, immunogenetic research in schizophrenia.

Toxoplasmosis and Polygenic Disease Susceptibility Genes: Extensive Toxoplasma gondii Host/Pathogen Interactome Enrichment in Nine Psychiatric or Neurological Disorders

Toxoplasma gondii is not only implicated in schizophrenia and related disorders, but also in Alzheimer's or Parkinson's disease, cancer, cardiac myopathies, and autoimmune disorders. During its life cycle, the pathogen interacts with ~3000 host genes or proteins. Susceptibility genes for multiple sclerosis, Alzheimer's disease, schizophrenia, bipolar disorder, depression, childhood obesity, Parkinson's disease, attention deficit hyperactivity disorder (P  from  8.01E - 05  (ADHD)  to  1.22E - 71) (multiple sclerosis), and autism (P = 0.013), but not anorexia or chronic fatigue are highly enriched in the human arm of this interactome and 18 (ADHD) to 33% (MS) of the susceptibility genes relate to it. The signalling pathways involved in the susceptibility gene/interactome overlaps are relatively specific and relevant to each disease suggesting a means whereby susceptibility genes could orient the attentions of a single pathogen towards disruption of the specific pathways that together contribute (positively or negatively) to the endophenotypes of different diseases. Conditional protein knockdown, orchestrated by T. gondii proteins or antibodies binding to those of the host (pathogen derived autoimmunity) and metabolite exchange, may contribute to this disruption. Susceptibility genes may thus be related to the causes and influencers of disease, rather than (and as well as) to the disease itself.

Exploring the pathogenetic association between schizophrenia and type 2 diabetes mellitus diseases based on pathway analysis

BACKGROUND

Schizophrenia (SCZ) and type 2 diabetes mellitus (T2D) are both complex diseases. Accumulated studies indicate that schizophrenia patients are prone to present the type 2 diabetes symptoms, but the potential mechanisms behind their association remain unknown. Here we explored the pathogenetic association between SCZ and T2D based on pathway analysis and protein-protein interaction.

RESULTS

With sets of prioritized susceptibility genes for SCZ and T2D, we identified significant pathways (with adjusted p-value < 0.05) specific for SCZ or T2D and for both diseases based on pathway enrichment analysis. We also constructed a network to explore the crosstalk among those significant pathways. Our results revealed that some pathways are shared by both SCZ and T2D diseases through a number of susceptibility genes. With 382 unique susceptibility proteins for SCZ and T2D, we further built a protein-protein interaction network by extracting their nearest interacting neighbours. Among 2,104 retrieved proteins, 364 of them were found simultaneously interacted with susceptibility proteins of both SCZ and T2D, and proposed as new candidate risk factors for both diseases. Literature mining supported the potential association of partial new candidate proteins with both SCZ and T2D. Moreover, some proteins were hub proteins with high connectivity and interacted with multiple proteins involved in both diseases, implying their pleiotropic effects for the pathogenic association. Some of these hub proteins are the components of our identified enriched pathways, including calcium signaling, g-secretase mediated ErbB4 signaling, adipocytokine signaling, insulin signaling, AKT signaling and type II diabetes mellitus pathways. Through the integration of multiple lines of information, we proposed that those signaling pathways, which contain susceptibility genes for both diseases, could be the key pathways to bridge SCZ and T2D. AKT could be one of the important shared components and may play a pivotal role to link both of the pathogenetic processes.

CONCLUSIONS

Our study is the first network and pathway-based systematic analysis for SCZ and T2D, and provides the general pathway-based view of pathogenetic association between two diseases. Moreover, we identified a set of candidate genes potentially contributing to the linkage between these two diseases. This research offers new insights into the potential mechanisms underlying the co-occurrence of SCZ and T2D, and thus, could facilitate the inference of novel hypotheses for the co-morbidity of the two diseases. Some etiological factors that exert pleiotropic effects shared by the significant pathways of two diseases may have important implications for the diseases and could be therapeutic intervention targets.

Effects of two commonly found strains of influenza A virus on developing dopaminergic neurons, in relation to the pathophysiology of schizophrenia

Influenza virus (InfV) infection during pregnancy is a known risk factor for neurodevelopment abnormalities in the offspring, including the risk of schizophrenia, and has been shown to result in an abnormal behavioral phenotype in mice. However, previous reports have concentrated on neuroadapted influenza strains, whereas increased schizophrenia risk is associated with common respiratory InfV. In addition, no specific mechanism has been proposed for the actions of maternal infection on the developing brain that could account for schizophrenia risk. We identified two common isolates from the community with antigenic configurations H3N2 and H1N1 and compared their effects on developing brain with a mouse modified-strain A/WSN/33 specifically on the developing of dopaminergic neurons. We found that H1N1 InfV have high affinity for dopaminergic neurons in vitro, leading to nuclear factor kappa B activation and apoptosis. Furthermore, prenatal infection of mothers with the same strains results in loss of dopaminergic neurons in the offspring, and in an abnormal behavioral phenotype. We propose that the well-known contribution of InfV to risk of schizophrenia during development may involve a similar specific mechanism and discuss evidence from the literature in relation to this hypothesis.

Toxoplasma gondii and cognitive deficits in schizophrenia: an animal model perspective

Cognitive deficits are a core feature of schizophrenia. Epidemiological evidence indicates that microbial pathogens may contribute to cognitive impairment in patients with schizophrenia. Exposure to Toxoplasma gondii (T. gondii) has been associated with cognitive deficits in humans. However, the mechanisms whereby the parasite impacts cognition remain poorly understood. Animal models of T. gondii infection may aid in elucidating the underpinnings of cognitive dysfunction. Here, we (1) overview the literature on the association of T. gondii infection and cognitive impairment, (2) critically analyze current rodent models of cognitive deficits resulting from T. gondii infection, and (3) explore possible mechanisms whereby the parasite may affect cognitive function.

Exposure to herpes simplex virus type 1 and cognitive impairments in individuals with schizophrenia

Latent infection with neurotropic herpes viruses, such as herpes simplex virus, type 1 (HSV1), has been generally considered benign in most immunocompetent individuals except for rare cases of encephalitis. However, several recent studies have shown impaired cognitive functions among individuals with schizophrenia exposed to HSV1 compared with schizophrenia patients not exposed to HSV1. Such impairments are robust and are prominently observed in working memory, verbal memory, and executive functions. Brain regions that play a key role in the regulation of these domains have shown smaller volumes, along with correlation between these morphometric changes and cognitive impairments in schizophrenia. One study noted temporal decline in executive function and gray matter loss among HSV1-exposed first-episode antipsychotic-naïve schizophrenia patients. Furthermore, a proof-of-concept double-blind placebo-controlled trial indicated improvement in cognitive performance following supplemental anti-herpes-specific medication among HSV1 seropositive schizophrenia patients. Cross-sectional studies have also identified an association between HSV1 exposure and lesser degrees of cognitive impairment among healthy control individuals and patients with bipolar disorder. These studies fulfill several Bradford-Hill criteria, suggesting etiological links between HSV1 exposure and cognitive impairment. Exposure to other human herpes viruses such as cytomegalovirus and herpes simplex virus type 2 (HSV2) may also be associated with cognitive impairment, but the data are less consistent. These studies are reviewed critically and further lines of enquiry recommended. The results are important from a public health perspective, as HSV1 exposure is highly prevalent in many populations.

Autoimmune diseases and infections as risk factors for schizophrenia

Immunological hypotheses have become increasingly prominent when studying the etiology of schizophrenia. Autoimmune diseases, and especially the number of infections requiring hospitalization, have been identified as significant risk factors for schizophrenia in a dose-response relationship, which seem compatible with an immunological hypothesis for subgroups of patients with schizophrenia. Inflammation and infections may affect the brain through many different pathways that are not necessarily mutually exclusive and can possibly increase the risk of schizophrenia in vulnerable individuals. However, the findings could also be an epiphenomenon and not causal, due to, for instance, common genetic vulnerability, which could be supported by the observations of an increased prevalence of autoimmune diseases and infections in parents of patients with schizophrenia. Nevertheless, autoimmune diseases and infections should be considered in the treatment of individuals with schizophrenia symptoms, and further research is needed of the immune system's possible contributing pathogenic factors in the etiology of schizophrenia.

Genetics of schizophrenia from a clinicial perspective

Schizophrenia (SZ) is a common disorder that runs in families. It has a relatively high heritability, i.e., inherited factors account for the major proportion of its etiology. The high heritability has motivated gene mapping studies that have improved in sophistication through the past two decades. Belying earlier expectations, it is now becoming increasingly clear that the cause of SZ does not reside in a single mutation, or even in a single gene. Rather, there are multiple DNA variants, not all of which have been identified. Additional risk may be conferred by interactions between individual DNA variants, as well as 'gene-environment' interactions. We review studies that have accounted for a fraction of the heritability. Their relevance to the practising clinician is discussed. We propose that continuing research in DNA variation, in conjunction with rapid ongoing advances in allied fields, will yield dividends from the perspective of diagnosis, treatment prediction through pharmacogenetics, and rational treatment through discoveries in pathogenesis.

Novel microRNAs encoded by duck enteritis virus

Duck enteritis virus (DEV) is an important herpesvirus pathogen associated with acute, highly contagious lethal disease in waterfowls. Using a deep sequencing approach on RNA from infected chicken embryo fibroblast cultures, we identified several novel DEV-encoded micro (mi)RNAs. Unlike most mardivirus-encoded miRNAs, DEV-encoded miRNAs mapped mostly to the unique long region of the genome. The precursors of DEV miR-D18 and miR-D19 overlapped with each other, suggesting similarities to miRNA-offset RNAs, although only the DEV-miR-D18-3p was functional in reporter assays. Identification of these novel miRNAs will add to the growing list of virus-encoded miRNAs enabling the exploration of their roles in pathogenesis.

Infectious agents associated with schizophrenia: a meta-analysis

Schizophrenia is a highly disabling and limiting disorder for patients and the possibility that infections by some microorganisms may be associated to its development may allow prevention and recovery. In the current study we have done a meta-analysis of studies that have assessed the possible association between detection of different infectious agents and schizophrenia. We report results that support the idea that there is a statistically significant association between schizophrenia and infection by Human Herpesvirus 2 (OR=1.34; CI 95%: 1.09-1.70; p=0.05), Borna Disease Virus (OR=2.03; CI 95%: 1.35-3.06; p<0.01), Human Endogenous Retrovirus W (OR=19.31; CI 95%: 6.74-55.29; p<0.001), Chlamydophila pneumoniae (OR=6.34; CI 95%: 2.83-14.19; p<0.001), Chlamydophila psittaci (OR=29.05; CI 95%: 8.91-94.70; p<0.001) and Toxoplasma gondii (OR=2.70; CI 95%: 1.34-4.42; p=0.005). The implications of these findings are discussed and further research options are also explicated.

The viral theory of schizophrenia revisited: abnormal placental gene expression and structural changes with lack of evidence for H1N1 viral presence in placentae of infected mice or brains of exposed offspring

Researchers have long noted an excess of patients with schizophrenia were born during the months of January and March. This winter birth effect has been hypothesized to result either from various causes such as vitamin D deficiency (McGrath, 1999; McGrath et al., 2010), or from maternal infection during pregnancy. Infection with a number of viruses during pregnancy including influenza, and rubella are known to increase the risk of schizophrenia in the offspring (Brown, 2006). Animal models using influenza virus or Poly I:C, a viral mimic, have been able to replicate many of the brain morphological, genetic, and behavioral deficits of schizophrenia (Meyer et al., 2006, 2008a, 2009; Bitanihirwe et al., 2010; Meyer and Feldon, 2010; Short et al., 2010). Using a murine model of prenatal viral infection, our laboratory has shown that viral infection on embryonic days 9, 16, and 18 leads to abnormal expression of brain genes and brain structural abnormalities in the exposed offspring (Fatemi et al., 2005, 2008a,b, 2009a,b). The purpose of the current study was to examine gene expression and morphological changes in the placenta, hippocampus, and prefrontal cortex as a result of viral infection on embryonic day 7 of pregnancy. Pregnant mice were either infected with influenza virus [A/WSN/33 strain (H1N1)] or sham-infected with vehicle solution. At E16, placentas were harvested and prepared for either microarray analysis or for light microscopy. We observed significant, upregulation of 77 genes and significant downregulation of 93 genes in placentas. In brains of exposed offspring following E7 infection, there were changes in gene expression in prefrontal cortex (6 upregulated and 24 downregulated at P0; 5 upregulated and 14 downregulated at P56) and hippocampus (4 upregulated and 6 downregulated at P0; 6 upregulated and 13 downregulated at P56). QRT-PCR verified the direction and magnitude of change for a number of genes associated with hypoxia, inflammation, schizophrenia, and autism. Placentas from infected mice showed a number of morphological abnormalities including presence of thrombi and increased presence of immune cells. Additionally, we searched for presence of H1N1 viral-specific genes for M1/M2, NA, and NS1 in placentas of infected mice and brains of exposed offspring and found none. Our results demonstrate that prenatal viral infection disrupts structure and gene expression of the placenta, hippocampus, and prefrontal cortex potentially explaining deleterious effects in the exposed offspring without evidence for presence of viral RNAs in the target tissues.

Marked reduction of AKT1 expression and deregulation of AKT1-associated pathways in peripheral blood mononuclear cells of schizophrenia patients

Background

Recent studies have suggested that deregulated AKT1 signaling is associated with schizophrenia. We hypothesized that if this is indeed the case, we should observe both decreased AKT1 expression as well as deregulation of AKT1 regulated pathways in Peripheral Blood Mononuclear Cells (PBMCs) of schizophrenia patients.

Objectives

To examine PBMC expression levels of AKT1 in schizophrenia patients versus controls, and to examine whether functional biological processes in which AKT1 plays an important role are deregulated in schizophrenia patients.

Methods/Results

A case-control study, investigating whole-genome PBMC gene expression in male, recent onset (<5 years) schizophrenia patients (N = 41) as compared to controls (N = 29). Genes, differentially expressed between patients and controls were identified using ANOVA with Benjamini-Hochberg correction (false discovery rate (FDR) = 0.05). Functional aspects of the deregulated set of genes were investigated with the Ingenuity Pathway Analysis (IPA) Software Tool. We found significantly decreased PBMC expression of AKT1 (p<0.001, t = −4.25) in the patients. AKT1 expression was decreased in antipsychotic-free or -naive patients (N = 11), in florid psychotic (N = 20) and in remitted (N = 21) patients. A total of 1224 genes were differentially expressed between patients and controls (FDR = 0.05). Functional analysis of the entire deregulated gene set indicated deregulated canonical pathways involved in a large number of cellular processes: immune system, cell adhesion and neuronal guidance, neurotrophins and (neural) growth factors, oxidative stress and glucose metabolism, and apoptosis and cell-cycle regulation. Many of these processes are associated with AKT1.

Conclusions

We show significantly decreased PBMC gene expression of AKT1 in male, recent-onset schizophrenia patients. Our observations suggest that decreased PBMC AKT1 expression is a stable trait in recent onset, male schizophrenia patients. We identified several AKT related cellular processes which are potentially affected in these patients, a majority of which play a prominent role in current schizophrenia hypotheses.

Genome-wide association study of antidepressant treatment-emergent suicidal ideation

Emergence of suicidal ideation (TESI) during treatment with antidepressants in major depression led to a black box warning. We performed a genome-wide association study to identify genetic markers, which increase the risk for this serious side effect. TESI was evaluated in depressed in-patients (N=397) and defined by an emergence of suicidal thoughts during hospitalization without suicidal thoughts at admission using the suicide item (3) of the Hamilton Depression Rating Scale. Genotype distribution of 405.383 single-nucleotide polymorphisms (SNPs) in patients with TESI (N=32/8.1%) was compared to patients without increase in suicidal ideation (N=329/82.9%) and to a subgroup never reported suicidal ideation (N=79/19.9%). Top results were analyzed in an independent sample (N=501). None variant reached genome-wide significance, the best associated SNP was rs1630535 (p-value=1.3 × 10(-7)). The top 79 SNPs could be analyzed in an independent sample, and 14 variants showed nominal significant association with the same risk allele in the replication sample. A discriminant analysis classifying patients using these 79 SNPs revealed a 91% probability to classify TESI vs non-TESI cases correctly in the replication sample. Although our data need to be interpreted carefully owing to the small numbers in both cohorts, they suggest that a combination of genetic markers might indeed be used to identify patients at risk for TESI.

DISC1 Pathway in Brain Development: Exploring Therapeutic Targets for Major Psychiatric Disorders

Genetic risk factors for major psychiatric disorders play key roles in neurodevelopment. Thus, exploring the molecular pathways of risk genes is important not only for understanding the molecular mechanisms underlying brain development, but also to decipher how genetic disturbances affect brain maturation and functioning relevant to major mental illnesses. During the last decade, there has been significant progress in determining the mechanisms whereby risk genes impact brain development. Nonetheless, given that the majority of psychiatric disorders have etiological complexities encompassing multiple risk genes and environmental factors, the biological mechanisms of these diseases remain poorly understood. How can we move forward to our research for discovery of the biological markers and novel therapeutic targets for major mental disorders? Here we review recent progress in the neurobiology of disrupted in schizophrenia 1 (DISC1), a major risk gene for major mental disorders, with a particular focus on its roles in cerebral cortex development. Convergent findings implicate DISC1 as part of a large, multi-step pathway implicated in various cellular processes and signal transduction. We discuss links between the DISC1 pathway and environmental factors, such as immune/inflammatory responses, which may suggest novel therapeutic targets. Existing treatments for major mental disorders are hampered by a limited number of pharmacological targets. Consequently, elucidation of the DISC1 pathway, and its association with neuropsychiatric disorders, may offer hope for novel treatment interventions.

Network-assisted Causal Gene Detection in Genome-wide Association Studies: An Improved Module Search Algorithm

The recent success of genome-wide association (GWA) studies has greatly expanded our understanding of many complex diseases by delivering previously unknown loci and genes. A large number of GWAS datasets have already been made available, with more being generated. To explore the underlying moderate and weak signals, we recently developed a network-based dense module search (DMS) method for identification of disease candidate genes from GWAS datasets, leveraging on the joint effect of multiple genes. DMS is designed to dynamically search for the best nodes in a step-wise fashion and, thus, could overcome the limitation of pre-defined gene sets. Here, we propose an improved version of DMS, the topologically-adjusted DMS, to facilitate the analysis of complex diseases. Building on the previous version of DMS, we improved the randomization process by taking into account the topological character, aiming to adjust the bias potentially caused by high-degree nodes in the whole network. We demonstrated the topologically-adjusted DMS algorithm in a GWAS dataset for schizophrenia. We found the improved DMS strategy could effectively identify candidate genes while reducing the burden of high-degree nodes. In our evaluation, we found more candidate genes identified by the topologically-adjusted DMS algorithm have been reported in the previous association studies, suggesting this new algorithm has better performance than the unweighted DMS algorithm. Finally, our functional analysis of the top module genes revealed that they are enriched in immune-related pathways.

Evolutionary-developmental perspectives on immune system interactions among the pregnant woman, placenta, and fetus, and responses to sexually transmitted infectious agents

A balance has evolved over deep time between the various immune systems of the "triad" that is linked together for a short period: the pregnant woman, the fetus, and the placenta. This balance is affected by, and helps to determine, the immune responses to maternal infectious agents that may be transmitted to the fetus/infant transplacentally, intrapartum, or via breast milk. This review identifies newer evolutionary concepts and processes related particularly to the human placenta, innate and adaptive immune systems involved in tolerance, and in responses to sexually transmitted infectious (STI) agents that may be pathogenic to the fetus/infant at different gestational periods and in the first year of life. An evolutionary-developmental (EVO-DEVO) perspective has been applied to the complexities within, and among, the different actors and their beneficial or deleterious outcomes. Such a phylogenetic and ontogenic approach has helped to stimulate several basic questions and suggested possible explanations and novel practical interventions.

Is schizophrenia developmental adaptation to environmental menaces?

Schizophrenia is a devastating mental disorder, with its symptoms typically emerging during late adolescence to young adulthood. In contrast, accumulating evidence suggests that schizophrenia is a developmental disorder in which brain abnormalities may occur even before birth. This has brought the major challenge to explain such discrepancy of brain deficits occurring during prenatal period and emergence of symptoms during adulthood. A number of ideas have been proposed to explain delayed emergence of symptoms at adulthood in relation to maturational processes of various brain systems during adolescence. However, these still lack clear relationship to prenatal deficits. Thus, a key to better understand the pathology of schizophrenia is to unveil a theory or model that can explain the relationship between prenatal deficits and post-pubertal onset of symptoms. Here we propose a novel hypothesis, along with discussion of several lines of evidences supporting it, that schizophrenia may not be a disorder in a strict sense, but rather be understood as the biological state occurring as consequence of adaptation to severe environmental conditions during the prenatal periods, which explains the relationship between prenatal developmental deficits and the postnatal maturational process for onset of symptoms.

The Fox and the Rabbits-Environmental Variables and Population Genetics (1) Replication Problems in Association Studies and the Untapped Power of GWAS (2) Vitamin A Deficiency, Herpes Simplex Reactivation and Other Causes of Alzheimer's Disease

Classical population genetics shows that varying permutations of genes and risk factors permit or disallow the effects of causative agents, depending on circumstance. For example, genes and environment determine whether a fox kills black or white rabbits on snow or black ash covered islands. Risk promoting effects are different on each island, but obscured by meta-analysis or GWAS data from both islands, unless partitioned by different contributory factors. In Alzheimer's disease, the foxes appear to be herpes, borrelia or chlamydial infection, hypercholesterolemia, hyperhomocysteinaemia, diabetes, cerebral hypoperfusion, oestrogen depletion, or vitamin A deficiency, all of which promote beta-amyloid deposition in animal models—without the aid of gene variants. All relate to risk factors and subsets of susceptibility genes, which condition their effects. All are less prevalent in convents, where nuns appear less susceptible to the ravages of ageing. Antagonism of the antimicrobial properties of beta-amyloid by Abeta autoantibodies in the ageing population, likely generated by antibodies raised to beta-amyloid/pathogen protein homologues, may play a role in this scenario. These agents are treatable by diet and drugs, vitamin supplementation, pathogen detection and elimination, and autoantibody removal, although again, the beneficial effects of individual treatments may be tempered by genes and environment.

Increased prevalence of Chlamydophila DNA in post-mortem brain frontal cortex from patients with schizophrenia

Infection can initiate symptoms of mental illness. It has been shown previously that Chlamydophila DNA is present six times more often in the blood of patients with schizophrenia than in the blood of control individuals. Monocytes, the main targets of Chlamydiaceae infection, are microglia precursors. We identified Chlamydiaceae infection using blinded brain DNA samples derived from the frontal cortex. Using PCR and sequence analysis, we found Chlamydophila DNA to be four times greater in patients with schizophrenia than in controls (schizophrenia: N=34, microbial DNA frequency 23.5%; controls: N=35, microbial DNA frequency 5.7%; P=0.045, OR=5.08). Persistent Chlamydophila-infected microglia or neuronal cells may impair neuronal circuits and thus be a mechanism for causing psychiatric illness in these patients.

Schizophrenia: a pathogenetic autoimmune disease caused by viruses and pathogens and dependent on genes

Many genes have been implicated in schizophrenia as have viral prenatal or adult infections and toxoplasmosis or Lyme disease. Several autoantigens also target key pathology-related proteins. These factors are interrelated. Susceptibility genes encode for proteins homologous to those of the pathogens while the autoantigens are homologous to pathogens' proteins, suggesting that the risk-promoting effects of genes and risk factors are conditional upon each other, and dependent upon protein matching between pathogen and susceptibility gene products. Pathogens' proteins may act as dummy ligands, decoy receptors, or via interactome interference. Many such proteins are immunogenic suggesting that antibody mediated knockdown of multiple schizophrenia gene products could contribute to the disease, explaining the immune activation in the brain and lymphocytes in schizophrenia, and the preponderance of immune-related gene variants in the schizophrenia genome. Schizophrenia may thus be a “pathogenetic” autoimmune disorder, caused by pathogens, genes, and the immune system acting together, and perhaps preventable by pathogen elimination, or curable by the removal of culpable antibodies and antigens.

The mind-body-microbial continuum

Our understanding of the vast collection of microbes that live on and inside us (microbiota) and their collective genes (microbiome) has been revolutionized by culture-independent "metagenomic" techniques and DNA sequencing technologies. Most of our microbes live in our gut, where they function as a metabolic organ and provide attributes not encoded in our human genome. Metagenomic studies are revealing shared and distinctive features of microbial communities inhabiting different humans. A central question in psychiatry is the relative role of genes and environment in shaping behavior. The human microbiome serves as the interface between our genes and our history of environmental exposures; explorations of our microbiomes thus offer the possibility of providing new insights into our neurodevelopment and our behavioral phenotypes by affecting complex processes such as inter- and intra personal variations in cognition, personality, mood, sleep, and eating behavior, and perhaps even a variety of neuropsychiatric diseases ranging from affective disorders to autism. Better understanding of microbiome-encoded pathways for xenobiotic metabolism also has important implications for improving the efficacy of pharmacologic interventions with neuromodulatory agents.

Association between bovine casein antibody and new onset schizophrenia among US military personnel

Schizophrenia is a pervasive neuropsychiatric disorder of uncertain etiology. Multiple studies have documented immune activation in individuals with schizophrenia. One antigen capable of inducing a prolonged immune response is bovine casein derived from ingested milk products. Increased levels of casein antibodies have been found in individuals with schizophrenia after diagnosis. This study was directed at determining the potential association between schizophrenia and pre-illness onset levels of immunoglobulin G (IgG) antibodies to bovine casein. Parallel analyses for casein antibody levels with bipolar disorder were included as comparison. Cases were service members who received medical discharges from the military with a schizophrenia diagnosis from 1992 to 2005. Serum specimens were selected for 855 cases and 1165 matched healthy controls. IgG antibodies to bovine whole-casein were measured by solid phase enzyme-linked immunosorbent assays (ELISAs). Hazard ratios (HR) were calculated to examine the associations of casein IgG level with risk of schizophrenia by time to diagnosis and by subjects' initial level. Increasing casein IgG antibody levels among those with a high initial level, drawn before diagnosis, was associated with an 18% increase in the hazard risk of schizophrenia per unit increase (value of low-positive standard) in IgG antibody levels (HR=1.18; 95% CI 1.04, 1.34). This is the first report to identify an association between the risk of schizophrenia and elevated antibodies to bovine casein prior to disease onset. Additional research is required to elucidate the complex genetic environmental interactions involved in the pathogenesis of schizophrenia and to identify potentially modifiable risk factors.

Epstein-Barr and other viral mimicry of autoantigens, myelin and vitamin D-related proteins and of EIF2B, the cause of vanishing white matter disease: massive mimicry of multiple sclerosis relevant proteins by the Synechococcus phage

The Epstein-Barr virus expresses proteins containing numerous short consensi (identical pentapeptides at least, or longer gapped consensi) that are identical to those in 16 multiple sclerosis autoantigens or in the products of multiple sclerosis susceptibility genes. Other viruses implicated in multiple sclerosis also display such mimicry and the Synechococcus phage was identified as a novel and major contributor to this phenomenon. Cyanobacteria hosts of Synechococcus phage favor temperate climes, in line with multiple sclerosis distribution, and bacterial and phage ecology accords closely with multiple sclerosis epidemiology. Bovine, ovine or canine viral proteins were also identified as autoantigen homologues, in line with epidemiological data linking multiple sclerosis to cattle density, sheep contact and dog ownership. Viral proteins align with known autoantigens, other myelin and vitamin D-related proteins and the translation initiation factor EIF2B, which is implicated in vanishing white matter disease. These data suggest that the autoantigens in multiple sclerosis, which causes demyelination in animal models, may be generated by antibodies raised to viral protein homologues. Multiple autoantibodies may cause multiple sclerosis via protein knockdown and immune activation. Their selective removal may be of clinical benefit as already suggested by promising results using plasmapheresis or immunoadsorption in certain multiple sclerosis patients.

The mind-body-microbial continuum

Our understanding of the vast collection of microbes that live on and inside us (microbiota) and their collective genes (microbiome) has been revolutionized by culture-independent "metagenomic" techniques and DNA sequencing technologies. Most of our microbes live in our gut, where they function as a metabolic organ and provide attributes not encoded in our human genome. Metagenomic studies are revealing shared and distinctive features of microbial communities inhabiting different humans. A central question in psychiatry is the relative role of genes and environment in shaping behavior. The human microbiome serves as the interface between our genes and our history of environmental exposures; explorations of our microbiomes thus offer the possibility of providing new insights into our neurodevelopment and our behavioral phenotypes by affecting complex processes such as inter- and intra personal variations in cognition, personality, mood, sleep, and eating behavior, and perhaps even a variety of neuropsychiatric diseases ranging from affective disorders to autism. Better understanding of microbiome-encoded pathways for xenobiotic metabolism also has important implications for improving the efficacy of pharmacologic interventions with neuromodulatory agents.

The chemokine receptor CCR5 in the central nervous system

The expression and the role of the chemokine receptor CCR5 have been mainly studied in the context of HIV infection. However, this protein is also expressed in the brain, where it can be crucial in determining the outcome in response to different insults. CCR5 expression can be deleterious or protective in controlling the progression of certain infections in the CNS, but it is also emerging that it could play a role in non-infectious diseases. In particular, it appears that, in addition to modulating immune responses, CCR5 can influence neuronal survival. Here, we summarize the present knowledge about the expression of CCR5 in the brain and highlight recent findings suggesting its possible involvement in neuroprotective mechanisms.

Cross-domain neurobiology data integration and exploration

Background

Understanding the biomedical implications of data from high throughput experiments requires solutions for effective cross-scale and cross-domain data exploration. However, existing solutions do not provide sufficient support for linking molecular level data to neuroanatomical structures, which is critical for understanding high level neurobiological functions.

Results

Our work integrates molecular level data with high level biological functions and we present results using anatomical structure as a scaffold. Our solution also allows the sharing of intermediate data exploration results with other web applications, greatly increasing the power of cross-domain data exploration and mining.

Conclusions

The Flex-based PubAnatomy web application we developed enables highly interactive visual exploration of literature and experimental data for understanding the relationships between molecular level changes, pathways, brain circuits and pathophysiological processes. The prototype of PubAnatomy is freely accessible at: [http://brainarray.mbni.med.umich.edu/Brainarray/prototype/PubAnatomy]

Fibroblast growth factors in schizophrenia

A large association study by O'Donovan et al recently suggested that genetic variation in fibroblast growth factor receptor (FGFR) 2 increases the risk for developing schizophrenia. Fibroblast growth factors (FGFs) are part of the family of glial growth factors; they control the growth and patterning of specific brain structures and regulate the maintenance and repair of neuronal tissues. In addition, a direct interaction was recently found between FGFRs and adenosine A(2A) receptors, leading to corticostriatal plasticity and antagonizing the signaling pathway of dopamine D(2) receptors. These findings make FGFs plausible candidate genes for schizophrenia. Here, we review the role of FGFs in schizophrenia and combine evidence from studies on variations in FGF genes, RNA expression, protein levels, and FGF administration, as well as the effects of medication and environmental risk factors for schizophrenia. These data suggest that changes in the FGF system contribute to schizophrenia and possibly to a wider range of psychiatric disorders. The role of FGFs in schizophrenia and related disorders needs to be studied in more detail.

Toxoplasma gondii infection in first-episode and inpatient individuals with schizophrenia

BACKGROUND

A high seroprevalence of Toxoplasma gondii infection has been detected in psychiatric patients, particularly in schizophrenia cases.

METHODS

In the present study 98 patients suffering from schizophrenia (58 inpatients and 40 first-episode patients) and 96 control patients (50 healthy volunteers and 46 with a depressive disorder) were examined for the presence of both IgG and IgM antibodies against T. gondii by enzyme-linked immunosorbent assay (ELISA). We applied the Bradford Hill criteria to identify the weight of causal inference.

RESULTS

The positivity rate of anti-T. gondii IgG antibodies among individuals with schizophrenia (57.1%) was significantly higher than in healthy controls (29.2%). There were no associations between immune status ratio (ISR) values and the risk of schizophrenia. The weight of evidence approach using the Bradford Hill criteria revealed a 92% probability of a causal association.

CONCLUSION

Our results show that exposure to T. gondii may lead to schizophrenia.

Evaluation of five antischizophrenic agents against Toxoplasma gondii in human cell cultures

An increasing interest in the association of the presence of antibodies to Toxoplasma gondii and the development of schizophrenia in patients has been generated over the last several years. Some antischizophrenia agents have been shown to have activity against T. gondii in cell culture assays and to ameliorate behavioral changes associated with chronic T. gondii infection in rats. In the present study, we examined the effects of commonly used antipsychotic and mood stabilizing agents (haloperidol, clozapine, fluphenazine, trifluoperazine, and thioridazine) for activity against developing tachyzoites of the RH strain of T. gondii in human fibroblast cell cultures. Neither haloperidol nor clozapine had a measurable effect. Fluphenazine had an IC(50) of 1.7 µM, thioridazine had an IC(50) of 1.2 µM, and trifluoperazine had an IC(50) of 3.8 µM. Our study demonstrates that some agents used to treat schizophrenia have the ability to inhibit T. gondii proliferation in cell culture.

Promoter variant of PIK3C3 is associated with autoimmunity against Ro and Sm epitopes in African-American lupus patients

The PIK3C3 locus was implicated in case-case genome-wide association study of systemic lupus erythematosus (SLE) which we had performed to detect genes associated with autoantibodies and serum interferon-alpha (IFN-α). Herein, we examine a PIK3C3 promoter variant (rs3813065/-442 C/T) in an independent multiancestral cohort of 478 SLE cases and 522 controls. rs3813065 C was strongly associated with the simultaneous presence of both anti-Ro and anti-Sm antibodies in African-American patients [OR = 2.24 (1.34–3.73), P = 2.0 × 10⁻³]. This autoantibody profile was associated with higher serum IFN-α (P = 7.6 × 10⁻⁶). In the HapMap Yoruba population, rs3813065 was associated with differential expression of ERAP2 (P = 2.0 × 10⁻⁵), which encodes an enzyme involved in MHC class I peptide processing. Thus, rs3813065 C is associated with a particular autoantibody profile and altered expression of an MHC peptide processing enzyme, suggesting that this variant modulates serologic autoimmunity in African-American SLE patients.

Cytokine hypothesis of schizophrenia pathogenesis: evidence from human studies and animal models

The pathogenesis of schizophrenia has yet to be fully characterized. Gene-environment interactions have been found to play a crucial role in the vulnerability to this disease. Among various environmental factors, inflammatory immune processes have been most clearly implicated in the etiology and pathology of schizophrenia. Cytokines, regulators of immune/inflammatory reactions and brain development, emerge as part of a common pathway of genetic and environmental components of schizophrenia. Maternal infection, obstetric complications, neonatal hypoxia and brain injury all recruit cytokines to mediate inflammatory processes. Abnormal expression levels of specific cytokines such as epidermal growth factor, interleukins (IL) and neuregulin-1 are found both in the brain and peripheral blood of patients with schizophrenia. Accordingly, cytokines have been proposed to transmit peripheral immune/inflammatory signals to immature brain tissue through the developing blood-brain barrier, perturbing structural and phenotypic development of the brain. This cytokine hypothesis of schizophrenia is also supported by modeling experiments in animals. Animals treated with specific cytokines of epidermal growth factor, IL-1, IL-6, and neuregulin-1 as embryos or neonates exhibit schizophrenia-like behavioral abnormalities after puberty, some of which are ameliorated by treatment with antipsychotics. In this review, we discuss the neurobiological mechanisms underlying schizophrenia and novel antipsychotic candidates based on the cytokine hypothesis.

No association between EGR gene family polymorphisms and schizophrenia in the Chinese population

Early growth response (EGR) genes are thought to have a role in the pathogenesis of schizophrenia because of their conserved DNA binding domain and biologically activity in neuronal plasticity. This zinc-finger motif could influence gene post-translational modification and expression. The multigenetic association model, using markers in genes of similar or antagonistic biological effects within a signal pathway or gene family, might be more appropriate to this aspect of the schizophrenia hypothesis than the single gene strategy. In this study we investigated the role of EGR1, EGR2, EGR3 and EGR4 within the EGR family. Taqman technology was used to examine 12 single nucleotide polymorphisms (SNPs) covering these four genes in 2044 Chinese Han subjects. Case-control analyses were performed to detect association of these 4 genes with schizophrenia and multifactor dimensionality reduction (MDR) analysis was employed to examine their potential gene-gene interaction in schizophrenia. Neither allelic nor genotypic single-locus tests revealed any significant association between EGR1-4 and the risk of schizophrenia nor was any such association found with regard to interaction within EGR1-4 (p(min)=0.623, CV Consistency=10/10). We concluded that although multiple candidate genes are involved in schizophrenogenic development, the EGR family may not play a major role in schizophrenia susceptibility in the Chinese Han population.