Molecular characterization of schizophrenia viewed by microarray analysis of gene expression in prefrontal cortex

Adolescent Stress-Induced Ventral Hippocampus Redox Dysregulation Underlies Behavioral Deficits and Excitatory/Inhibitory Imbalance Related to Schizophrenia

BACKGROUND AND HYPOTHESIS

Redox dysregulation has been proposed as a convergent point of childhood trauma and the emergence of psychiatric disorders, such as schizophrenia (SCZ). A critical region particularly vulnerable to environmental insults during adolescence is the ventral hippocampus (vHip). However, the impact of severe stress on vHip redox states and their functional consequences, including behavioral and electrophysiological changes related to SCZ, are not entirely understood.

STUDY DESIGN

After exposing adolescent animals to physical stress (postnatal day, PND31-40), we explored social and cognitive behaviors (PND47-49), the basal activity of pyramidal glutamate neurons, the number of parvalbumin (PV) interneurons, and the transcriptomic signature of the vHip (PND51). We also evaluated the impact of stress on the redox system, including mitochondrial respiratory function, reactive oxygen species (ROS) production, and glutathione (GSH) levels in the vHip and serum.

STUDY RESULTS

Adolescent-stressed animals exhibited loss of sociability, cognitive impairment, and vHip excitatory/inhibitory (E/I) imbalance. Genome-wide transcriptional profiling unveiled the impact of stress on redox system- and synaptic-related genes. Stress impacted mitochondrial respiratory function and changes in ROS levels in the vHip. GSH and glutathione disulfide (GSSG) levels were elevated in the serum of stressed animals, while GSSG was also increased in the vHip and negatively correlated with sociability. Additionally, PV interneuron deficits in the vHip caused by adolescent stress were associated with oxidative stress.

CONCLUSIONS

Our results highlight the negative impact of adolescent stress on vHip redox regulation and mitochondrial function, which are partially associated with E/I imbalance and behavioral abnormalities related to SCZ.

Psychedelics action and schizophrenia

Psychedelics are compounds acting by serotonin 5-hydroxytryptamine (5-HT)2A receptor activation and induce several behavioral responses. They are of special interest because of their positive effects on neuropsychiatric disorders (depression and posttraumatic stress disorder). However, several findings revealed that some psychedelic actions are similar to symptoms observed in schizophrenia (psychosis, sensorimotor gating impairments, attention, and working memory deficits) which might limit their clinical applications. Psychedelics activate some neurotransmitters, i.e., serotonergic, and glutamatergic, that are also impaired in schizophrenia. Therefore, the neurobiological background of psychedelics and schizophrenia is partially similar. Another important aspect to discuss is the perspective of using psychedelics in schizophrenia therapy. Postmortem studies showed a loss of synapses in schizophrenia, and the positive effects of psychedelics on neuroplasticity (synaptogenesis, neurogenesis, and neuritogenesis) might be essential in the context of schizophrenia therapy. However, because of psychedelics' psychotic action, the recommended doses of psychedelics in schizophrenia treatment are not established, and subpsychedelic dosing or microdosing are considered. Exploratory studies are needed to determine the tolerability of treatment and appropriate dosing regimen. Another therapeutic option is using non-hallucinogenic psychedelic analogs that also induce neuroplastic outcomes but do not have psychotogenic effects. Further preclinical and clinical studies are needed to recognize the potential effectiveness of 5-HT2A agonists in schizophrenia therapy.

Neuron navigators: A novel frontier with physiological and pathological implications

Neuron navigators are microtubule plus-end tracking proteins containing basic and serine rich regions which are encoded by neuron navigator genes (NAVs). Neuron navigator proteins are essential for neurite outgrowth, neuronal migration, and overall neurodevelopment along with some other functions as well. The navigator proteins are substantially expressed in the developing brain and have been reported to be differentially expressed in various tissues at different ages. Over the years, the research has found neuron navigators to be implicated in a spectrum of pathological conditions such as developmental anomalies, neurodegenerative disorders, neuropathic pain, anxiety, cancers, and certain inflammatory conditions. The existing knowledge about neuron navigators remains sparse owing to their differential functions, undiscovered modulators, and unknown molecular mechanisms. Investigating the possible role of neuron navigators in various physiological processes and pathological conditions pose as a novel field that requires extensive research and might provide novel mechanistic insights and understanding of these aspects.

Localization and Diagnostic Specificity of Glutamic Acid Decarboxylase Transcript Alterations in the Dorsolateral Prefrontal Cortex in Schizophrenia

BACKGROUND

Working memory (WM) deficits in schizophrenia are thought to reflect altered inhibition in the dorsolateral prefrontal cortex (DLPFC). This interpretation is supported by findings of lower transcript levels of the 2 enzymes, GAD67 and GAD65, which mediate basal and activity-dependent GABA (gamma-aminobutyric acid) synthesis, respectively. However, the relative magnitude, location within the depth of the DLPFC, and specificity to the disease process of schizophrenia of alterations in GAD67 and/or GAD65 remain unclear.

METHODS

Levels of GAD67 and GAD65 messenger RNAs (mRNAs) in superficial (layers 2/superficial 3) and deep (deep layer 6/white matter) zones of the DLPFC were quantified by quantitative polymerase chain reaction in subjects with schizophrenia (n = 41), major depression (n = 42), or bipolar disorder (n = 39) and unaffected comparison (n = 43) subjects.

RESULTS

Relative to the unaffected comparison group, GAD67 and GAD65 mRNA levels in the schizophrenia group were lower (p = .039, effect size = -0.69 and p = .027, effect size = -0.72, respectively) in the superficial zone but were unaltered in the deep zone. In the major depression group, only GAD67 mRNA levels were lower and only in the superficial zone (p = .089, effect size = 0.70). No differences were detected in the bipolar disorder group. Neither GAD67 nor GAD65 mRNA alterations were explained by psychosis, mood disturbance, or common comorbid factors.

CONCLUSIONS

Alterations in markers of GABA synthesis demonstrated transcript, DLPFC zone, and diagnostic specificity. Given the dependence of WM on GABA neurotransmission in the superficial DLPFC, our findings suggest that limitations to GABA synthesis in this location contribute to WM impairments in schizophrenia, especially during demanding WM tasks, when GABA synthesis requires the activity of both GAD67 and GAD65.

Associations between prefrontal PI (16:0/20:4) lipid, TNC mRNA, and APOA1 protein in schizophrenia: A trans-omics analysis in post-mortem brain

Background

Though various mechanisms have been proposed for the pathophysiology of schizophrenia, the full extent of these mechanisms remains unclear, and little is known about the relationships among them. We carried out trans-omics analyses by comparing the results of the previously reported lipidomics, transcriptomics, and proteomics analyses; all of these studies used common post-mortem brain samples.

Methods

We collected the data from three aforementioned omics studies on 6 common post-mortem samples (3 schizophrenia patients and 3 controls), and analyzed them as a whole group sample. Three correlation analyses were performed for each of the two of three omics studies in these samples. In order to discuss the strength of the correlations in a limited sample size, the p-values of each correlation coefficient were confirmed using the Student's t-test. In addition, partial correlation analysis was also performed for some correlations, to verify the strength of the impact of each factor on the correlations.

Results

The following three factors were strongly correlated with each other: the lipid level of phosphatidylinositol (PI) (16:0/20:4), the amount of TNC mRNA, and the quantitative signal intensity of APOA1 protein. PI (16:0/20:4) and TNC showed a positive correlation, while PI (16:0/20:4) and APOA1, and TNC and APOA1 showed negative correlations. All of these correlations reached at p < 0.01. PI (16:0/20:4) and TNC were decreased in the prefrontal cortex of schizophrenia samples, while APOA1 was increased. Partial correlation analyses among them suggested that PI (16:0/20:4) and TNC have no direct correlation, but their relationships are mediated by APOA1.

Conclusion

The current results suggest that these three factors may provide new clues to elucidate the relationships among the candidate mechanisms of schizophrenia, and support the potential of trans-omics analyses as a new analytical method.

Gene Expression and Epigenetic Regulation in the Prefrontal Cortex of Schizophrenia

Schizophrenia pathogenesis remains challenging to define; however, there is strong evidence that the interaction of genetic and environmental factors causes the disorder. This paper focuses on transcriptional abnormalities in the prefrontal cortex (PFC), a key anatomical structure that determines functional outcomes in schizophrenia. This review summarises genetic and epigenetic data from human studies to understand the etiological and clinical heterogeneity of schizophrenia. Gene expression studies using microarray and sequencing technologies reported the aberrant transcription of numerous genes in the PFC in patients with schizophrenia. Altered gene expression in schizophrenia is related to several biological pathways and networks (synaptic function, neurotransmission, signalling, myelination, immune/inflammatory mechanisms, energy production and response to oxidative stress). Studies investigating mechanisms driving these transcriptional abnormalities focused on alternations in transcription factors, gene promoter elements, DNA methylation, posttranslational histone modifications or posttranscriptional regulation of gene expression mediated by non-coding RNAs.

Dorsolateral Prefrontal Cortex Glutamate/Gamma-Aminobutyric Acid (GABA) Alterations in Clinical High Risk and First-Episode Schizophrenia: A Preliminary 7-T Magnetic Resonance Spectroscopy Imaging Study

Converging lines of evidence suggest that an imbalance between excitation and inhibition is present in the dorsolateral prefrontal cortex (DLPFC) of schizophrenia (SCZ). Gamma-aminobutyric-acid (GABA) and, to a lesser extent, glutamate (Glu) abnormalities were reported in the DLPFC of SCZ patients, especially on the right hemisphere, by post-mortem studies. However, in vivo evidence of GABA, Glu, and Glu/GABA DLPFC abnormalities, particularly on the right side and the early stages of illness, is limited. In this preliminary study, we utilized 7-Tesla magnetic resonance spectroscopic imaging (MRSI) to investigate bilateral Glu/Creatine (Cre), GABA/Cre, and Glu/GABA in the DLPFC of sixteen first episode schizophrenia (FES), seventeen clinical high risk (CHR), and twenty-six healthy comparison (HC) subjects. FES and CHR had abnormal GABA/Cre and Glu/GABA in the right DLPFC (rDLPFC) compared with HC participants, while no differences were observed in the left DLPFC (lDLPFC) among the three groups. Furthermore, HC had higher Glu/GABA in rDLPFC compared to lDLPFC (R > L), whereas the opposite relationship (R < L) was observed in the DLPFC Glu/GABA of FES patients. Altogether, these findings indicate that GABA/Cre and Glu/GABA DLPFC alterations are present before illness manifestation and worsen in FES patients, thus representing a putative early pathophysiological biomarker for SCZ and related psychotic disorders.

Multi-omics insights into the biological mechanisms underlying statistical gene-by-lifestyle interactions with smoking and alcohol consumption

Though both genetic and lifestyle factors are known to influence cardiometabolic outcomes, less attention has been given to whether lifestyle exposures can alter the association between a genetic variant and these outcomes. The Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium's Gene-Lifestyle Interactions Working Group has recently published investigations of genome-wide gene-environment interactions in large multi-ancestry meta-analyses with a focus on cigarette smoking and alcohol consumption as lifestyle factors and blood pressure and serum lipids as outcomes. Further description of the biological mechanisms underlying these statistical interactions would represent a significant advance in our understanding of gene-environment interactions, yet accessing and harmonizing individual-level genetic and 'omics data is challenging. Here, we demonstrate the coordinated use of summary-level data for gene-lifestyle interaction associations on up to 600,000 individuals, differential methylation data, and gene expression data for the characterization and prioritization of loci for future follow-up analyses. Using this approach, we identify 48 genes for which there are multiple sources of functional support for the identified gene-lifestyle interaction. We also identified five genes for which differential expression was observed by the same lifestyle factor for which a gene-lifestyle interaction was found. For instance, in gene-lifestyle interaction analysis, the T allele of rs6490056 (ALDH2) was associated with higher systolic blood pressure, and a larger effect was observed in smokers compared to non-smokers. In gene expression studies, this allele is associated with decreased expression of ALDH2, which is part of a major oxidative pathway. Other results show increased expression of ALDH2 among smokers. Oxidative stress is known to contribute to worsening blood pressure. Together these data support the hypothesis that rs6490056 reduces expression of ALDH2, which raises oxidative stress, leading to an increase in blood pressure, with a stronger effect among smokers, in whom the burden of oxidative stress is greater. Other genes for which the aggregation of data types suggest a potential mechanism include: GCNT4×current smoking (HDL), PTPRZ1×ever-smoking (HDL), SYN2×current smoking (pulse pressure), and TMEM116×ever-smoking (mean arterial pressure). This work demonstrates the utility of careful curation of summary-level data from a variety of sources to prioritize gene-lifestyle interaction loci for follow-up analyses.

Evidence that a working memory cognitive phenotype within schizophrenia has a unique underlying biology

It is suggested studying phenotypes within the syndrome of schizophrenia will accelerate understanding the complex molecular pathology of the disorder. Supporting this hypothesis, we have identified a sub-group within schizophrenia with impaired working memory (WM) and have used Affymetrix™ Human Exon 1.0 ST Arrays to compare their blood RNA levels (n=16) to a group of with intact WM (n=18). Levels of 72 RNAs were higher in blood from patients with impaired WM, 11 of which have proven links to the maintenance of different aspects of working memory (cognition). Overall, changed gene expression in those with impaired WM could be linked to cognition through glutamatergic activity, olfaction, immunity, inflammation as well as energy and metabolism. Our data gives preliminary support to the hypotheses that there is a working memory deficit phenotype within the syndrome of schizophrenia with has a biological underpinning. In addition, our data raises the possibility that a larger study could show that the specific changes in gene expression we have identified could prove to be the biomarkers needed to develop a blood test to identify those with impaired WM; a significant step toward allowing the use of personalised medicine directed toward improving their impaired working memory.

Functional impairment of cortical AMPA receptors in schizophrenia

Clinical and preclinical studies suggest that some of the behavioral alterations observed in schizophrenia (SZ) may be mechanistically linked to synaptic dysfunction of glutamatergic signaling. Recent genetic and proteomic studies suggest alterations of cortical glutamate receptors of the AMPA-type (AMPARs), which are the predominant ligand-gated ionic channels of fast transmission at excitatory synapses. The impact of gene and protein alterations on the electrophysiological activity of AMPARs is not known in SZ. In this proof of principle work, using human postmortem brain synaptic membranes isolated from the dorsolateral prefrontal cortex (DLPFC), we combined electrophysiological analysis from microtransplanted synaptic membranes (MSM) with transcriptomic (RNA-Seq) and label-free proteomics data in 10 control and 10 subjects diagnosed with SZ. We observed in SZ a reduction in the amplitude of AMPARs currents elicited by kainate, an agonist of AMPARs that blocks the desensitization of the receptor. This reduction was not associated with protein abundance but with a reduction in kainate's potency to activate AMPARs. Electrophysiologically-anchored dataset analysis (EDA) was used to identify synaptosomal proteins that linearly correlate with the amplitude of the AMPARs responses, gene ontology functional annotations were then used to determine protein-protein interactions. Protein modules associated with positive AMPARs current increases were downregulated in SZ, while protein modules that were upregulated in SZ were associated with decreased AMPARs currents. Our results indicate that transcriptomic and proteomic alterations, frequently observed in the DLPFC in SZ, converge at the synaptic level producing a functional electrophysiological impairment of AMPARs.

Disrupted-in-schizophrenia-1 is required for normal pyramidal cell-interneuron communication and assembly dynamics in the prefrontal cortex

We interrogated prefrontal circuit function in mice lacking Disrupted-in-schizophrenia-1 (Disc1-mutant mice), a risk factor for psychiatric disorders. Single-unit recordings in awake mice revealed reduced average firing rates of fast-spiking interneurons (INTs), including optogenetically identified parvalbumin-positive cells, and a lower proportion of INTs phase-coupled to ongoing gamma oscillations. Moreover, we observed decreased spike transmission efficacy at local pyramidal cell (PYR)-INT connections in vivo, suggesting a reduced excitatory effect of local glutamatergic inputs as a potential mechanism of lower INT rates. On the network level, impaired INT function resulted in altered activation of PYR assemblies: While assembly activations defined as coactivations within 25 ms were observed equally often, the expression strength of individual assembly patterns was significantly higher in Disc1-mutant mice. Our data, thus, reveal a role of Disc1 in shaping the properties of prefrontal assembly patterns by setting INT responsiveness to glutamatergic drive.

Thalamocortical Development: A Neurodevelopmental Framework for Schizophrenia

Adolescence is a period of increased vulnerability for the development of psychiatric disorders, including schizophrenia. The prefrontal cortex (PFC) undergoes substantial maturation during this period, and PFC dysfunction is central to cognitive impairments in schizophrenia. As a result, impaired adolescent maturation of the PFC has been proposed as a mechanism in the etiology of the disorder and its cognitive symptoms. In adulthood, PFC function is tightly linked to its reciprocal connections with the thalamus, and acutely inhibiting thalamic inputs to the PFC produces impairments in PFC function and cognitive deficits. Here, we propose that thalamic activity is equally important during adolescence because it is required for proper PFC circuit development. Because thalamic abnormalities have been observed early in the progression of schizophrenia, we further postulate that adolescent thalamic dysfunction can have long-lasting consequences for PFC function and cognition in patients with schizophrenia.

Brain Environment Interactions: Stress, Posttraumatic Stress Disorder, and the Need for a Postmortem Brain Collection

Stress, especially the extreme stress of traumatic events, can alter both neurobiology and behavior. Such extreme environmental situations provide a useful model for understanding environmental influences on human biology and behavior. This paper will review some of the evidence of brain alterations that occur with exposure to environmental stress. This will include recent studies using neuroimaging and will address the need for histological confirmation of imaging study results. We will review the current scientific approaches to understanding brain environment interactions, and then make the case for the collection and study of postmortem brain tissue for the advancement of our understanding of the effects of environment on the brain.Creating a brain tissue collection specifically for the investigation of the effects of extreme environmental stressors fills a gap in the current research; it will provide another of the important pieces to the puzzle that constitutes the scientific investigation of negative effects of environmental exposures. Such a resource will facilitate new discoveries related to the psychiatric illnesses of acute stress disorder and posttraumatic stress disorder, and can enable scientists to correlate structural and functional imaging findings with tissue abnormalities, which is essential to validate the results of recent imaging studies.

Elevated endogenous GDNF induces altered dopamine signalling in mice and correlates with clinical severity in schizophrenia

Presynaptic increase in striatal dopamine is the primary dopaminergic abnormality in schizophrenia, but the underlying mechanisms are not understood. Here, we hypothesized that increased expression of endogenous GDNF could induce dopaminergic abnormalities that resemble those seen in schizophrenia. To test the impact of GDNF elevation, without inducing adverse effects caused by ectopic overexpression, we developed a novel in vivo approach to conditionally increase endogenous GDNF expression. We found that a 2-3-fold increase in endogenous GDNF in the brain was sufficient to induce molecular, cellular, and functional changes in dopamine signalling in the striatum and prefrontal cortex, including increased striatal presynaptic dopamine levels and reduction of dopamine in prefrontal cortex. Mechanistically, we identified adenosine A2a receptor (A_2AR), a G-protein coupled receptor that modulates dopaminergic signalling, as a possible mediator of GDNF-driven dopaminergic abnormalities. We further showed that pharmacological inhibition of A_2AR with istradefylline partially normalised striatal GDNF and striatal and cortical dopamine levels in mice. Lastly, we found that GDNF levels are increased in the cerebrospinal fluid of first episode psychosis patients, and in post-mortem striatum of schizophrenia patients. Our results reveal a possible contributor for increased striatal dopamine signalling in a subgroup of schizophrenia patients and suggest that GDNF-A_2AR crosstalk may regulate dopamine function in a therapeutically targetable manner.

Plasmolipin and Its Role in Cell Processes

The mechanisms involved in the origin and development of malignant and neurodegenerative diseases are an important area of modern biomedicine. A crucial task is to identify new molecular markers that are associated with rearrangements of intracellular signaling and can be used for prognosis and the development of effective treatment approaches. The proteolipid plasmolipin (PLLP) is a possible marker. PLLP is a main component of the myelin sheath and plays an important role in the development and normal function of the nervous system. PLLP is involved in intracellular transport, lipid raft formation, and Notch signaling. PLLP is presumably involved in various disorders, such as cancer, schizophrenia, Alzheimer's disease, and type 2 diabetes mellitus. PLLP and its homologs were identified as possible virus entry receptors. The review summarizes the data on the PLLP structure, normal functions, and role in diseases.

Emerging evidence implicating a role for neurexins in neurodegenerative and neuropsychiatric disorders

Synaptopathies are brain disorders characterized by dysfunctional synapses, which are specialized junctions between neurons that are essential for the transmission of information. Synaptic dysfunction can occur due to mutations that alter the structure and function of synaptic components or abnormal expression levels of a synaptic protein. One class of synaptic proteins that are essential to their biology are cell adhesion proteins that connect the pre- and post-synaptic compartments. Neurexins are one type of synaptic cell adhesion molecule that have, recently, gained more pathological interest. Variants in both neurexins and their common binding partners, neuroligins, have been associated with several neuropsychiatric disorders. In this review, we summarize some of the key physiological functions of the neurexin protein family and the protein networks they are involved in. Furthermore, examination of published literature has implicated neurexins in both neuropsychiatric and neurodegenerative disorders. There is a clear link between neurexins and neuropsychiatric disorders, such as autism spectrum disorder and schizophrenia. However, multiple expression studies have also shown changes in neurexin expression in several neurodegenerative disorders, including Alzheimer's disease and Parkinson's disease. Therefore, this review highlights the potential importance of neurexins in brain disorders and the importance of doing more targeted studies on these genes and proteins.

Analysis of Molecular Networks in the Cerebellum in Chronic Schizophrenia: Modulation by Early Postnatal Life Stressors in Murine Models

Despite the growing importance of the cerebellum as a region highly vulnerable to accumulating molecular errors in schizophrenia, limited information is available regarding altered molecular networks with potential therapeutic targets. To identify altered networks, we conducted one-shot liquid chromatography–tandem mass spectrometry in postmortem cerebellar cortex in schizophrenia and healthy individuals followed by bioinformatic analysis (PXD024937 identifier in ProteomeXchange repository). A total of 108 up-regulated proteins were enriched in stress-related proteins, half of which were also enriched in axonal cytoskeletal organization and vesicle-mediated transport. A total of 142 down-regulated proteins showed an enrichment in proteins involved in mitochondrial disease, most of which were also enriched in energy-related biological functions. Network analysis identified a mixed module of mainly axonal-related pathways for up-regulated proteins with a high number of interactions for stress-related proteins. Energy metabolism and neutrophil degranulation modules were found for down-regulated proteins. Further, two double-hit postnatal stress murine models based on maternal deprivation combined with social isolation or chronic restraint stress were used to investigate the most robust candidates of generated networks. CLASP1 from the axonal module in the model of maternal deprivation was combined with social isolation, while YWHAZ was not altered in either model. METTL7A from the degranulation pathway was reduced in both models and was identified as altered also in previous gene expression studies, while NDUFB9 from the energy network was reduced only in the model of maternal deprivation combined with social isolation. This work provides altered stress- and mitochondrial disease-related proteins involved in energy, immune and axonal networks in the cerebellum in schizophrenia as possible novel targets for therapeutic interventions and suggests that METTL7A is a possible relevant altered stress-related protein in this context.

An updated reappraisal of synapsins: structure, function and role in neurological and psychiatric disorders

Synapsins (Syns) are phosphoproteins strongly involved in neuronal development and neurotransmitter release. Three distinct genes SYN1, SYN2 and SYN3, with elevated evolutionary conservation, have been described to encode for Synapsin I, Synapsin II and Synapsin III, respectively. Syns display a series of common features, but also exhibit distinctive localization, expression pattern, post-translational modifications (PTM). These characteristics enable their interaction with other synaptic proteins, membranes and cytoskeletal components, which is essential for the proper execution of their multiple functions in neuronal cells. These include the control of synapse formation and growth, neuron maturation and renewal, as well as synaptic vesicle mobilization, docking, fusion, recycling. Perturbations in the balanced expression of Syns, alterations of their PTM, mutations and polymorphisms of their encoding genes induce severe dysregulations in brain networks functions leading to the onset of psychiatric or neurological disorders. This review presents what we have learned since the discovery of Syn I in 1977, providing the state of the art on Syns structure, function, physiology and involvement in central nervous system disorders.

GABAergic dysfunction, neural network hyperactivity and memory impairments in human aging and Alzheimer's disease

In this review, we focus on the potential role of the γ-aminobutyric acidergic (GABAergic) system in age-related episodic memory impairments in humans, with a particular focus on Alzheimer's disease (AD). Well-established animal models have shown that GABA plays a central role in regulating and synchronizing neuronal signaling in the hippocampus, a brain area critical for episodic memory that undergoes early and significant morphologic and functional changes in the course of AD. Neuroimaging research in humans has documented hyperactivity in the hippocampus and losses of resting state functional connectivity in the Default Mode Network, a network that itself prominently includes the hippocampus-presaging episodic memory decline in individuals at-risk for AD. Apolipoprotein ε4, the highest genetic risk factor for AD, is associated with GABAergic dysfunction in animal models, and episodic memory impairments in humans. In combination, these findings suggest that GABA may be the linchpin in a complex system of factors that eventually leads to the principal clinical hallmark of AD: episodic memory loss. Here, we will review the current state of literature supporting this hypothesis. First, we will focus on the molecular and cellular basis of the GABAergic system and its role in memory and cognition. Next, we report the evidence of GABA dysregulations in AD and normal aging, both in animal models and human studies. Finally, we outline a model of GABAergic dysfunction based on the results of functional neuroimaging studies in humans, which have shown hippocampal hyperactivity to episodic memory tasks concurrent with and even preceding AD diagnosis, along with factors that may modulate this association.

Genetic aspects in schizophrenia. Receptoral theories. Metabolic theories

Ties between schizophrenia (SCZ) and genetics are undeniably significant issue prone to be discussed in the nowadays psychology. Recent research on this domain focuses more on specific genes and heredity (specifically monozygotic pairs of twins) for diagnosing SCZ, than on environmental influences. SCZ is considered a multifactorial disease, thought to convert from a merger of risk and biological genes and environmental factors that could alter and reshape the trajectory of brain development. On this regard, this review sums up recent and innovative methods of distinguishing schizophrenic features from other mental illnesses in patients, based on chromosomal and genes changes. The term “reverse genetics” is no longer up to date, being replaced with “genome scanning” and “positional cloning”. For many researchers, genome scanning is continuing the reverse of the sensible strategy for detecting various important biological disorders, which may start from the discovery of a protein or any other molecule involved in a biological process, being followed by its gene cloning. Genes being discovered in this manner could become candidate genes for the disease. However, genome scanning occurs through testing each chromosomal segment (or mitochondrial genome) for the counter transmission of the disease.

Progressions on the Coexistence of Neuronal and Glial Precursor Cells in the Cerebral Ventricular Zone

Heterogeneity is defined as the quality or state of being diverse in character or content. This article summarizes the natural progression from my studies, reported in the first issue of the Journal of Neuroscience, that identified molecular heterogeneity in precursor cells of the developing primate cerebral cortex to the current state in which differences defined at the molecular, cellular, circuit, and systems levels are building data encyclopedias. The emphasis on heterogeneity has impacted many contributors in the field of developmental neuroscience, who have led a quest to determine the extent to which there is diversity, when it appears developmentally, and what heritable and nonheritable factors mediate nervous system assembly and function. Since the appearance of the article on progenitor cell heterogeneity in the inaugural issue of the Journal of Neuroscience, there have been continuous advances in technologies and data analytics that are contributing to a much better understanding of the origins of neurobiological and behavioral heterogeneity.

Integrative Analysis Identified Key Schizophrenia Risk Factors from an Abnormal Behavior Mouse Gene Set

Schizophrenia (SCZ) is a severe chronic psychiatric illness with heterogeneous symptoms. However, the pathogenesis of SCZ is unclear, and the number of well-defined SCZ risk factors is limited. We hypothesized that an abnormal behavior (AB) gene set verified by mouse model experiments can be used to better understand SCZ risks. In this work, we carried out an integrative bioinformatics analysis to study two types of risk genes that are either differentially expressed (DEGs) in the case-control study data or carry reported SCZ genetic variants (MUTs). Next, we used RNA-Seq expression data from the hippocampus (HIPPO) and dorsolateral prefrontal cortex (DLPFC) to define the key genes affected by different types (DEGs and MUTs) in different brain regions (DLPFC and HIPPO): DLPFC-kDEG, DLPFC-kMUT, HIPPO-kDEG, and HIPPO-kMUT. The four hub genes (SHANK1, SHANK2, DLG4, and NLGN3) of the biological functionally enriched terms were strongly linked to SCZ via gene co-expression network analysis. Then, we observed that specific spatial expressions of DLPFC-kMUT and HIPPO-kMUT were convergent in the early stages and divergent in the later stages of development. In addition, all four types of key genes showed significantly larger average protein-protein interaction degrees than the background. Comparing the different cell types, the expression of four types of key genes showed specificity in different dimensions. Together, our results offer new insights into potential risk factors and help us understand the complexity and regional heterogeneity of SCZ.

Interaction of maternal immune activation and genetic interneuronal inhibition

Genes and environment interact during intrauterine life, and potentially alter the developmental trajectory of the brain. This can result in life-long consequences on brain function. We have previously developed two transgenic mouse lines that suppress Gad1 expression in parvalbumin (PVALB) and neuropeptide Y (NPY) expressing interneuron populations using a bacterial artificial chromosome (BAC)-driven miRNA-based silencing technology. We were interested to assess if maternal immune activation (MIA), genetic interneuronal inhibition, and the combination of these two factors disrupt and result in long-term changes in neuroinflammatory gene expression, sterol biosynthesis, and acylcarnitine levels in the brain of maternally exposed offspring. Pregnant female WT mice were given a single intraperitoneal injection of saline or polyinosinic-polycytidilic acid [poly(I:C)] at E12.5. Brains of offspring were analyzed at postnatal day 90. We identified complex and persistent neuroinflammatory gene expression changes in the hippocampi of MIA-exposed offspring, as well in the hippocampi of Npy/Gad1 and Pvalb/Gad1 mice. In addition, both MIA and genetic inhibition altered the post-lanosterol sterol biosynthesis in the neocortex and disrupted the typical acylcarnitine profile. In conclusion, our findings suggest that both MIA and inhibition of interneuronal function have long-term consequences on critical homeostatic mechanisms of the brain, including immune function, sterol levels, and energy metabolism.

A combination of three plasma bile acids as a putative biomarker for schizophrenia

The aim of the present study is to determine whether plasma bile acids (BAs) could be used as an auxiliary diagnostic biomarker to distinguish patients with schizophrenia from healthy controls. Seventeen different BAs were quantitatively measured in plasma of 12 healthy participants and 12 patients with schizophrenia. Then, the data were subjected to correlation and linear discriminant analysis (LDA). The concentrations of cholic acid (CA), taurochenodeoxycholic acid (TCDCA) and taurodeoxycholic acid (TDCA) were significantly decreased in plasma of the schizophrenia patients. Correlation analysis showed the concentrations of CA, TCDCA and TDCA were negatively correlated with schizophrenia. In addition, LDA demonstrated that combination of CA, TCDCA and TDCA with a classification formula could predict correctly classified cases and the accuracy of prediction was up to 95.83%. Combination of the three BAs may be useful to diagnose schizophrenia in plasma samples.

Oxidative Stress-Related Mechanisms in Schizophrenia Pathogenesis and New Treatment Perspectives

Schizophrenia is recognized to be a highly heterogeneous disease at various levels, from genetics to clinical manifestations and treatment sensitivity. This heterogeneity is also reflected in the variety of oxidative stress-related mechanisms contributing to the phenotypic realization and manifestation of schizophrenia. At the molecular level, these mechanisms are supposed to include genetic causes that increase the susceptibility of individuals to oxidative stress and lead to gene expression dysregulation caused by abnormal regulation of redox-sensitive transcriptional factors, noncoding RNAs, and epigenetic mechanisms favored by environmental insults. These changes form the basis of the prooxidant state and lead to altered redox signaling related to glutathione deficiency and impaired expression and function of redox-sensitive transcriptional factors (Nrf2, NF-κB, FoxO, etc.). At the cellular level, these changes lead to mitochondrial dysfunction and metabolic abnormalities that contribute to aberrant neuronal development, abnormal myelination, neurotransmitter anomalies, and dysfunction of parvalbumin-positive interneurons. Immune dysfunction also contributes to redox imbalance. At the whole-organism level, all these mechanisms ultimately contribute to the manifestation and development of schizophrenia. In this review, we consider oxidative stress-related mechanisms and new treatment perspectives associated with the correction of redox imbalance in schizophrenia. We suggest that not only antioxidants but also redox-regulated transcription factor-targeting drugs (including Nrf2 and FoxO activators or NF-κB inhibitors) have great promise in schizophrenia. But it is necessary to develop the stratification criteria of schizophrenia patients based on oxidative stress-related markers for the administration of redox-correcting treatment.

The prefrontal cortex as a target for atypical antipsychotics in schizophrenia, lessons of neurodevelopmental animal models

Prefrontal cortex (PFC) inflammatory imbalance, oxidative/nitrosative stress (O/NS) and impaired neuroplasticity in schizophrenia are thought to have neurodevelopmental origins. Animal models are not only useful to test this hypothesis, they are also effective to establish a relationship among brain disturbances and behavior with the atypical antipsychotics (AAPs) effects. Here we review data of PFC post-mortem and in vivo neuroimaging, human induced pluripotent stem cells (hiPSC), and peripheral blood studies of inflammatory, O/NS, and neuroplasticity alterations in the disease as well as about their modulation by AAPs. Moreover, we reviewed the PFC alterations and the AAP mechanisms beyond their canonical antipsychotic action in four neurodevelopmental animal models relevant to the study of schizophrenia with a distinct approach in the generation of schizophrenia-like phenotypes, but all converge in O/NS and altered neuroplasticity in the PFC. These animal models not only reinforce the neurodevelopmental risk factor model of schizophrenia but also arouse some novel potential therapeutic targets for the disease including the reestablishment of the antioxidant response by the perineuronal nets (PNNs) and the nuclear factor erythroid 2-related factor (Nrf2) pathway, as well as the dendritic spine dynamics in the PFC pyramidal cells.

Key role for lipids in cognitive symptoms of schizophrenia

Schizophrenia (SZ) is a psychiatric disorder with a convoluted etiology that includes cognitive symptoms, which arise from among others a dysfunctional dorsolateral prefrontal cortex (dlPFC). In our search for the molecular underpinnings of the cognitive deficits in SZ, we here performed RNA sequencing of gray matter from the dlPFC of SZ patients and controls. We found that the differentially expressed RNAs were enriched for mRNAs involved in the Liver X Receptor/Retinoid X Receptor (LXR/RXR) lipid metabolism pathway. Components of the LXR/RXR pathway were upregulated in gray matter but not in white matter of SZ dlPFC. Intriguingly, an analysis for shared genetic etiology, using two SZ genome-wide association studies (GWASs) and GWAS data for 514 metabolites, revealed genetic overlap between SZ and acylcarnitines, VLDL lipids, and fatty acid metabolites, which are all linked to the LXR/RXR signaling pathway. Furthermore, analysis of structural T₁-weighted magnetic resonance imaging in combination with cognitive behavioral data showed that the lipid content of dlPFC gray matter is lower in SZ patients than in controls and correlates with a tendency towards reduced accuracy in the dlPFC-dependent task-switching test. We conclude that aberrations in LXR/RXR-regulated lipid metabolism lead to a decreased lipid content in SZ dlPFC that correlates with reduced cognitive performance.

Δ-9-Tetrahydrocannabinol treatment during adolescence and alterations in the inhibitory networks of the adult prefrontal cortex in mice subjected to perinatal NMDA receptor antagonist injection and to postweaning social isolation

The prefrontal cortex (PFC) continues its development during adolescence and alterations in its structure and function, particularly of inhibitory networks, have been detected in schizophrenic patients. Since cannabis use during adolescence is a risk factor for this disease, our main objective was to investigate whether THC administration during this period might exacerbate alterations in prefrontocortical inhibitory networks in mice subjected to a perinatal injection of MK801 and postweaning social isolation. This double-hit model (DHM) combines a neurodevelopmental manipulation and the exposure to an aversive experience during early life; previous work has shown that DHM mice have important alterations in the structure and connectivity of PFC interneurons. In the present study we found that DHM had reductions in prepulse inhibition of the startle reflex (PPI), GAD67 expression and cingulate 1 cortex volume. Interestingly, THC by itself induced increases in PPI and decreases in the dendritic complexity of somatostatin expressing interneurons. Both THC and DHM reduced the density of parvalbumin expressing cells surrounded by perineuronal nets and, when combined, they disrupted the ratio between the density of puncta expressing excitatory and inhibitory markers. Our results support previous work showing alterations in parameters involving interneurons in similar animal models and schizophrenic patients. THC treatment does not modify further these parameters, but changes some others related also to interneurons and their plasticity, in some cases in the opposite direction to those induced by the DHM, suggesting a protective effect.

Novel Treatment Strategies Targeting Myelin and Oligodendrocyte Dysfunction in Schizophrenia

Oligodendrocytes are the glial cells responsible for the formation of the myelin sheath around axons. During neurodevelopment, oligodendrocytes undergo maturation and differentiation, and later remyelination in adulthood. Abnormalities in these processes have been associated with behavioral and cognitive dysfunctions and the development of various mental illnesses like schizophrenia. Several studies have implicated oligodendrocyte dysfunction and myelin abnormalities in the disorder, together with altered expression of myelin-related genes such as Olig2, CNP, and NRG1. However, the molecular mechanisms subjacent of these alterations remain elusive. Schizophrenia is a severe, chronic psychiatric disorder affecting more than 23 million individuals worldwide and its symptoms usually appear at the beginning of adulthood. Currently, the major therapeutic strategy for schizophrenia relies on the use of antipsychotics. Despite their widespread use, the effects of antipsychotics on glial cells, especially oligodendrocytes, remain unclear. Thus, in this review we highlight the current knowledge regarding oligodendrocyte dysfunction in schizophrenia, compiling data from (epi)genetic studies and up-to-date models to investigate the role of oligodendrocytes in the disorder. In addition, we examined potential targets currently investigated for the improvement of schizophrenia symptoms. Research in this area has been investigating potential beneficial compounds, including the D-amino acids D-aspartate and D-serine, that act as NMDA receptor agonists, modulating the glutamatergic signaling; the antioxidant N-acetylcysteine, a precursor in the synthesis of glutathione, protecting against the redox imbalance; as well as lithium, an inhibitor of glycogen synthase kinase 3β (GSK3β) signaling, contributing to oligodendrocyte survival and functioning. In conclusion, there is strong evidence linking oligodendrocyte dysfunction to the development of schizophrenia. Hence, a better understanding of oligodendrocyte differentiation, as well as the effects of antipsychotic medication in these cells, could have potential implications for understanding the development of schizophrenia and finding new targets for drug development.

Molecular alterations in the medial temporal lobe in schizophrenia

The medial temporal lobe (MTL) and its individual structures have been extensively implicated in schizophrenia pathophysiology, with considerable efforts aimed at identifying structural and functional differences in this brain region. The major structures of the MTL for which prominent differences have been revealed include the hippocampus, the amygdala and the superior temporal gyrus (STG). The different functions of each of these regions have been comprehensively characterized, and likely contribute differently to schizophrenia. While neuroimaging studies provide an essential framework for understanding the role of these MTL structures in various aspects of the disease, ongoing efforts have sought to employ molecular measurements in order to elucidate the biology underlying these macroscopic differences. This review provides a summary of the molecular findings in three major MTL structures, and discusses convergent findings in cellular architecture and inter-and intra-cellular networks. The findings of this effort have uncovered cell-type, network and gene-level specificity largely unique to each brain region, indicating distinct molecular origins of disease etiology. Future studies should test the functional implications of these molecular changes at the circuit level, and leverage new advances in sequencing technology to further refine our understanding of the differential contribution of MTL structures to schizophrenia.

Psychiatric drugs impact mitochondrial function in brain and other tissues

Mitochondria have been linked to the etiology of schizophrenia (SZ). However, studies of mitochondria in SZ might be confounded by the effects of pharmacological treatment with antipsychotic drugs (APDs) and other common medications. This review summarizes findings on relevant mitochondria mechanisms underlying SZ, and the potential impact of psychoactive drugs including primarily APDs, but also antidepressants and anxiolytics. The summarized data suggest that APDs impair mitochondria function by decreasing Complex I activity and ATP production and dissipation of the mitochondria membrane potential. At the same time, in the brains of patients with SZ, antipsychotic drug treatment normalizes gene expression modules enriched in mitochondrial genes that are decreased in SZ. This indicates that APDs may have both positive and negative effects on mitochondria. The available evidence suggests three conclusions i) alterations in mitochondria functions in SZ exist prior to APD treatment, ii) mitochondria alterations in SZ can be reversed by APD treatment, and iii) APDs directly cause impairment of mitochondria function. Overall, the mechanisms of action of psychiatric drugs on mitochondria are both direct and indirect; we conclude the effects of APDs on mitochondria may contribute to both their therapeutic and metabolic side effects. These studies support the hypothesis that neuronal mitochondria are an etiological factor in SZ. Moreover, APDs and other drugs must be considered in the evaluation of this pathophysiological role of mitochondria in SZ. Considering these effects, pharmacological actions on mitochondria may be a worthwhile target for further APD development.

Schizophrenia-associated MicroRNA-Gene Interactions in the Dorsolateral Prefrontal Cortex

Schizophrenia-associated anomalies in gene expression in postmortem brain can be attributed to a combination of genetic and environmental influences. Given the small effect size of common variants, it is likely that we may only see the combined impact of some of these at the pathway level in small postmortem studies. At the gene level, however, there may be more impact from common environmental exposures mediated by influential epigenomic modifiers, such as microRNA (miRNA). We hypothesise that dysregulation of miRNAs and their alteration of gene expression have significant implications in the pathophysiology of schizophrenia. In this study, we integrate changes in cortical gene and miRNA expression to identify regulatory interactions and networks associated with the disorder. Gene expression analysis in post-mortem prefrontal dorsolateral cortex (BA 46) (n = 74 matched pairs of schizophrenia, schizoaffective, and control samples) was integrated with miRNA expression in the same cohort to identify gene-miRNA regulatory networks. A significant gene-miRNA interaction network was identified, including miR-92a, miR-495, and miR-134, which converged with differentially expressed genes in pathways involved in neurodevelopment and oligodendrocyte function. The capacity for miRNA to directly regulate gene expression through respective binding sites in BCL11A, PLP1, and SYT11 was also confirmed to support the biological relevance of this integrated network model. The observations in this study support the hypothesis that miRNA dysregulation is an important factor in the complex pathophysiology of schizophrenia.

Altered Expression of a Unique Set of Genes Reveals Complex Etiology of Schizophrenia

Background: The etiology of schizophrenia is extensively debated, and multiple factors have been contended to be involved. A panoramic view of the contributing factors in a genome-wide study can be an effective strategy to provide a comprehensive understanding of its causality. Materials and Methods: GSE53987 dataset downloaded from GEO-database, which comprised mRNA expression data of post-mortem brain tissue across three regions from control (C) and age-matched subjects (T) of schizophrenia (N = Hippocampus [HIP]: C-15, T-18, Prefrontal cortex [PFC]: C-15, T-19, Associative striatum [STR]: C-18, T-18). Bio-conductor-affy-package used to compute mRNA expression, and further t-test applied to investigate differential gene expression. The analysis of the derived genes performed using the PANTHER Classification System and NCBI database. Further, a protein interactome analysis of the derived gene set was performed using STRING v10 database (https://string-db.org/) Results: A set of 40 genes showed significantly altered (p < 0.01) expression across all three brain regions. The analyses unraveled genes implicated in biological processes and events, and molecular pathways relating basic neuronal functions. Conclusions: The aberrant expression of genes maintaining basic cell machinery explains compromised neuronal processing in SCZ.

Protective Effect of the MCP-1 Gene Haplotype against Schizophrenia

While cytokines and their genetic variants have been intensively studied in schizophrenia, little attention has been focused on chemokines in the last years. The monocyte chemoattractant protein 1 (MCP-1) is known to attract peripheral monocytes to the brain during an inflammatory reaction and to affect the T helper (Th) cell development by stimulating Th2 polarization. Owing to the neuroinflammation in schizophrenia and the variable level of MCP-1 in these patients' sera, we proposed to analyze the impact of functional genetic variants of the MCP-1 gene (MCP-1-2518A/G (rs1024611), MCP-1-362G/C (rs2857656), and MCP-1 int1del554-567 (rs3917887)) in schizophrenic patients. We conducted a case-control study on a Tunisian population composed of 200 patients and 200 controls using RFLP-PCR. Our results indicated that the minor alleles (-2518G and Del554-567) were significantly more prevalent in controls than in patients (P=0.001/adjusted OR = 0.42, P=0.04/adjusted OR = 0.64), whereas, for -362C minor allele, increased risk of schizophrenia was revealed (P=0.001, adjusted OR = 2.38). In conclusion, we have identified the haplotype combination -2581G/-362G/int1del554-567 that could mediate protection against schizophrenia (P=0.0038, OR = 0.19) and the effect could result more strongly from the MCP-1 -2582G with -362G variants, whereas the effect of int1del554-567 may in part be explained by its LD with -362.

Reduced cortical somatostatin gene expression in a rat model of maternal immune activation

Alterations in GABAergic interneurons and glutamic acid decarboxylase (GAD) are observed in the brains of people with schizophrenia. Studies also show increased density of interstitial white matter neurons (IWMN), including those containing GAD and somatostatin (SST) in the brain in schizophrenia. Maternal immune activation can be modelled in rodents to investigate the relationship between prenatal exposure to infections and increased risk of developing schizophrenia. We reported that maternal immune activation induced an increase in density of somatostatin-positive IWMN in the adult rat offspring. Here we hypothesised that maternal immune activation induced in pregnant rats by polyinosinic:polycytidylic acid would alter SST and GAD gene expression as well as increase the density of GAD-positive IWMNs in the adult offspring. SST gene expression was significantly reduced in the cingulate cortex of adult offspring exposed to late gestation maternal immune activation. There was no change in cortical GAD gene expression nor GAD-positive IWMN density in adults rats exposed to maternal immune activation at either early or late gestation. This suggests that our model of maternal immune activation induced by prenatal exposure of rats to polyinosinic:polycytidylic acid during late gestation is able to recapitulate changes in SST but not other GABAergic neuropathologies observed in schizophrenia.

Loss of dysbindin-1 affects GABAergic transmission in the PFC

It has been shown that dystrobrevin-binding protein 1 gene that encodes the protein dysbindin-1 is associated with risk for cognitive deficits, and studies have shown decreases in glutamate and correlated decreases in dysbindin-1 protein in the prefrontal cortex (PFC) and hippocampus of post-mortem tissue from schizophrenia patients. The PFC and the hippocampus have been shown to play a fundamental role in cognition, and studies in dysbindin-1 null mice have shown alterations in NMDAR located in pyramidal neurons as well as perturbation in LTP and cognitive deficits. The balance between excitatory and inhibitory transmission is crucial for normal cognitive functions; however, there is a dearth of information regarding the effects of loss of dysbindin-1 in GABAergic transmission. Using in vitro whole-cell clamp recordings, Western blots, and immunohistochemistry, we report here that dysbindin-1-deficient mice exhibit a significant decrease in the frequency of sIPSCs and in the amplitude of mIPSCs and significant decreases in PV staining and protein level. These results suggest that loss of dysbindin-1 affects GABAergic transmission at pre- and postsynaptic level and decreases parvalbumin markers.

Consistent gene signature of schizophrenia identified by a novel feature selection strategy from comprehensive sets of transcriptomic data

The etiology of schizophrenia (SCZ) is regarded as one of the most fundamental puzzles in current medical research, and its diagnosis is limited by the lack of objective molecular criteria. Although plenty of studies were conducted, SCZ gene signatures identified by these independent studies are found highly inconsistent. As one of the most important factors contributing to this inconsistency, the feature selection methods used currently do not fully consider the reproducibility among the signatures discovered from different datasets. Therefore, it is crucial to develop new bioinformatics tools of novel strategy for ensuring a stable discovery of gene signature for SCZ. In this study, a novel feature selection strategy (1) integrating repeated random sampling with consensus scoring and (2) evaluating the consistency of gene rank among different datasets was constructed. By systematically assessing the identified SCZ signature comprising 135 differentially expressed genes, this newly constructed strategy demonstrated significantly enhanced stability and better differentiating ability compared with the feature selection methods popular in current SCZ research. Based on a first-ever assessment on methods’ reproducibility cross-validated by independent datasets from three representative studies, the new strategy stood out among the popular methods by showing superior stability and differentiating ability. Finally, 2 novel and 17 previously reported transcription factors were identified and showed great potential in revealing the etiology of SCZ. In sum, the SCZ signature identified in this study would provide valuable clues for discovering diagnostic molecules and potential targets for SCZ.

Novel Complex Interactions between Mitochondrial and Nuclear DNA in Schizophrenia and Bipolar Disorder

Mitochondrial dysfunction has been associated with schizophrenia (SZ) and bipolar disorder (BD). This review examines recent publications and novel associations between mitochondrial genes and SZ and BD. Associations of nuclear-encoded mitochondrial variants with SZ were found using gene- and pathway-based approaches. Two control region mitochondrial DNA (mtDNA) SNPs, T16519C and T195C, both showed an association with SZ and BD. A review of 4 studies of A15218G located in the cytochrome B oxidase gene (CYTB, SZ = 11,311, control = 35,735) shows a moderate association with SZ (p = 2.15E-03). Another mtDNA allele A12308G was nominally associated with psychosis in BD type I subjects and SZ. The first published study testing the epistatic interaction between nuclear-encoded and mitochondria-encoded genes demonstrated evidence for potential interactions between mtDNA and the nuclear genome for BD. A similar analysis for the risk of SZ revealed significant joint effects (34 nuclear-mitochondria SNP pairs with joint effect p ≤ 5E-07) and significant enrichment of projection neurons. The mitochondria-encoded gene CYTB was found in both the epistatic interactions for SZ and BD and the single SNP association of SZ. Future efforts considering population stratification and polygenic risk scores will test the role of mitochondrial variants in psychiatric disorders.

Shared co-expression networks in frontal cortex of the normal aged brain and schizophrenia

Previous studies on the brain of people with schizophrenia have identified structural changes and gene expression changes, suggesting that brain aging maybe accelerated in people with schizophrenia. To better characterize gene expression profiles in schizophrenia and in the aged population we constructed co-expression networks using RNA-Seq data from frontal cortex. The first data set analysed was from 62 subjects with schizophrenia and 51 unaffected controls ranging in age from 19 to 63 years. The second separate data set was from normal control individuals ranging in age from 29 to 106 years. In the first data set, we found two co-expression modules significantly associated with schizophrenia. One was a downregulated co-expression module enriched for neuron function related genes and the other was an upregulated immune/inflammation-related module. In the second data set of normal individuals, we found seven co-expression modules significantly correlated with age. A comparison of the co-expression modules from the two data sets revealed a significant consensus in nodes associated with schizophrenia and those associated with normal aging. The results indicate that a co-expression module related to neuronal function is downregulated and an immune/inflammation related co-expression module is upregulated, and associated with cells of the blood vessels, in both schizophrenia and in normal aging. This finding adds further support to the hypothesis that there may be accelerated brain aging in schizophrenia.

The SNAP25 Interactome in Ventromedial Caudate in Schizophrenia Includes the Mitochondrial Protein ARF1

Abnormalities of SNAP25 (synaptosome-associated protein 25) amount and protein-protein interactions occur in schizophrenia, and may contribute to abnormalities of neurotransmitter release in patients. However, presynaptic terminal function depends on multiple subcellular mechanisms, including energy provided by mitochondria. To explore the SNAP25 interactome in schizophrenia, we immunoprecipitated SNAP25 along with interacting proteins from the ventromedial caudate of 15 cases of schizophrenia and 13 controls. Proteins were identified with mass spectrometry-based proteomics. As well as 15 SNARE- (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) associated proteins, we identified 17 mitochondria-associated and four other proteins. The mitochondrial small GTPase ARF1 (ADP-ribosylation factor 1) was identified in eight schizophrenia SNAP25 immunoprecipitates and none from controls (P = 0.004). Although the ARF1-SNAP25 interaction may be increased, immunoblotting demonstrated 21% lower ARF1-21 (21 kiloDaltons) in schizophrenia samples (P = 0.04). In contrast, the mitochondrial protein UQCRC1 (ubiquinol-cytochrome c reductase core protein 1) did not differ. Lower ARF1-21 levels were associated with the previously reported increased SNAP25-syntaxin interaction in schizophrenia (r = -0.39, P = 0.04). Additional immunoprecipitation studies confirmed the ARF1-21-SNAP25 interaction, independent of UQCRC1. Both ARF1 and SNAP25 were localized to synaptosomes. Confocal microscopy demonstrated co-localization of ARF1 and SNAP25, and further suggested fivefold enrichment of ARF1 in synaptosomes containing an excitatory marker (vesicular glutamate transporter) compared with synaptosomes containing an inhibitory marker (vesicular GABA transporter). The present findings suggest an association between abnormalities of SNARE proteins involved with vesicular neurotransmission and the mitochondrial protein ARF1 that may contribute to the pathophysiology of schizophrenia.

Over-expression of TGF-β1 gene in medication free Schizophrenia

BACKGROUND AND PURPOSE

Immunological pathways play a crucial role in developing and precipitating neuropsychiatric disorders. Although the exact pathogenesis of schizophrenia is unknown, the possible role of genetic and biomarker involvement of the immune system is gaining attention. Here we quantified the mRNA expression of cytokines as a key role player of the immune system from the peripheral blood mononuclear cells of patients with schizophrenia and healthy controls to identify the differentially expressed genes.

METHODS

Sixteen medication-free schizophrenia patients and 16 healthy subjects were enrolled in the current study. To investigate the desired expression level of mRNAs including TGF-β1, IL-1β, IL-23, TNF-α, NF-κB, and BDNF, quantitative real-time PCR was performed using specific oligonucleotide primers and the Applied Bio systems StepOne™ real time PCR system. DNA methylation was also analyzed through methylation-specific polymerase chain reaction (MSP).

RESULTS

TGF-β1 was significantly up-regulated in peripheral blood mononuclear cells of patients vs. healthy individuals (P value = 0.03). In addition, we found a significant correlation between the positive symptom scale and TGF-β1 gene overexpression (r = 0.536, P = 0.039). However, we did not observe any statistically significant differences for the methylation status of CpG Islands 1 and 2 between the patients and normal group. No statistical significance was found either for gene expression of IL-1β (P = 0.32), IL-23 (P = 0.12), TNF-α (P = 0.87), NF-κB (P = 0.07), and BDNF (P = 0.33).

CONCLUSIONS

Although the number of medication-free schizophrenia patients is extremely limited, our data highlighted the potential role of TGF-β1 as a regulatory cytokine in complex inflammatory mechanism involved in medication-free schizophrenia. In addition, we observed that increased level of TGF-β1 mRNA in this disease might not be under methylation as an epigenetic control element at the genomic level.

Reduced expression of synapsin II in a chronic phencyclidine preclinical rat model of schizophrenia

Schizophrenia is a mental disorder characterized by positive symptoms, negative symptoms, and cognitive dysfunction. Phencyclidine (PCP)-a N-methyl-D-aspartate (NMDA) receptor antagonist-induces symptoms indistinguishable from those of schizophrenia. A reduction of the phosphoprotein synapsin II has also been implicated in schizophrenia and has a well-known role in the maintenance of the presynaptic reserve pool and vesicle mobilization. This study assessed the behavioral and biochemical outcomes of chronic NMDA receptor antagonism in rodents and its implications for the pathophysiology of schizophrenia. Sprague Dawley rats received saline or chronic PCP (5 mg/kg/day) for 14 days via surgically implanted Alzet® osmotic mini-pumps. Following the treatment period, rats were tested with a series of behavioral paradigms, including locomotor activity, social interaction, and sensorimotor gating. Following behavioral assessment, the medial prefrontal cortex (mPFC) of all rats was isolated for synapsin II protein analysis. Chronic PCP treatment yielded a hyper-locomotive state (p = 0.0256), reduced social interaction (p = 0.0005), and reduced pre-pulse inhibition (p < 0.0001) in comparison to saline-treated controls. Synapsin IIa (p < 0.0001) and IIb (p < 0.0071) levels in the mPFC of chronically treated PCP rats were reduced in comparison to the saline group. Study results confirm that rats subject to chronic PCP treatment display behavioral phenotypes similar to established preclinical animal models of schizophrenia. Reduction of synapsin II expression in this context implicates the role of this protein in the pathophysiology of schizophrenia and sheds light on the longer-term consequences of NMDA receptor antagonism facilitated by chronic PCP treatment.

Behavioral Analysis of SNAP-25 and Synaptobrevin-2 Haploinsufficiency in Mice

In central synapses, synaptobrevin-2 (also called VAMP-2) is the predominant synaptic vesicle SNARE protein that interacts with the plasma membrane SNAREs, SNAP-25 and syntaxin-1 to execute exocytosis. Mice deficient in synaptobrevin-2 or SNAP-25 show embryonic lethality, which precludes investigation of the complete loss-of-function of these proteins in the adult nervous system. However, mice that carry heterozygous null mutations survive into adulthood and are fertile. In order to elucidate how loss-of-function mutations in these proteins may result in human disease phenotypes it is important to develop bona fide animal models. Therefore, given the importance of these two critical SNAREs in central synaptic transmission and their association with several neurological or neuropsychiatric disorders, we performed a comprehensive behavioral analysis of SNAP-25 heterozygous null (SNAP-25^+/-) mice as well as the synaptobrevin-2 heterozygous null (+/-) mice. This analysis revealed only mild phenotypes, SNAP-25 (+/-) mice exhibited marked hypoactivity, whereas synaptobrevin-2 (+/-) mice showed enhanced performance on the rotarod. The two mouse lines did not manifest significant deficits in anxiety-related behaviors, learning and memory measures, or prepulse inhibition. The rather mild behavioral deficits indicate that these key proteins, SNAP25 and synaptobrevin-2, are expressed in excess to circumvent the impact of potential fluctuations in expression levels on nervous system function.

(Micro)Glia as Effectors of Cortical Volume Loss in Schizophrenia

Contrary to the notion that neurology but not psychiatry is the domain of disorders evincing structural brain alterations, it is now clear that there are subtle but consistent neuropathological changes in schizophrenia. These range from increases in ventricular size to dystrophic changes in dendritic spines. A decrease in dendritic spine density in the prefrontal cortex (PFC) is among the most replicated of postmortem structural findings in schizophrenia. Examination of the mechanisms that account for the loss of dendritic spines has in large part focused on genes and molecules that regulate neuronal structure. But the simple question of what is the effector of spine loss, ie, where do the lost spines go, is unanswered. Recent data on glial cells suggest that microglia (MG), and perhaps astrocytes, play an important physiological role in synaptic remodeling of neurons during development. Synapses are added to the dendrites of pyramidal cells during the maturation of these neurons; excess synapses are subsequently phagocytosed by MG. In the PFC, this occurs during adolescence, when certain symptoms of schizophrenia emerge. This brief review discusses recent advances in our understanding of MG function and how these non-neuronal cells lead to structural changes in neurons in schizophrenia.

Positron emission tomography imaging of the γ-aminobutyric acid system

In this review, we summarize the recent development of positron emission tomography (PET) radioligands for γ-aminobutyric acid A (GABA_A) receptors and their potential to measure changes in endogenous GABA levels and highlight the clinical and translational applications of GABA-sensitive PET radioligands. We review the basic physiology of the GABA system with a focus on the importance of GABA_A receptors in the brain and specifically the benzodiazepine binding site. Challenges for the development of central nervous system radioligands and particularly for radioligands with increased GABA sensitivity are outlined, as well as the status of established benzodiazepine site PET radioligands and agonist GABA_A radioligands. We underline the challenge of using allosteric interactions to measure GABA concentrations and review the current state of PET imaging of changes in GABA levels. We conclude that PET tracers with increased GABA sensitivity are required to efficiently measure GABA release and that such a tool could be broadly applied to assess GABA transmission in vivo across several disorders.

Identification of key gene modules and pathways of human glioma through coexpression network

Glioma causes great harm to people worldwide. Systemic coexpression analysis of this disease could be beneficial for the identification and development of new prognostic and predictive markers in the clinical management of glioma. In this study, we extracted data sets from the Gene Expression Omnibus data set by using "glioma" as the keyword. Then, a coexpression module was constructed with the help of Weighted Gene Coexpression Network Analysis software. Besides, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed on the genes in these modules. As a result, the critical modules and target genes were identified. Eight coexpression modules were constructed using the 4,000 genes with a high expression value of the total 141 glioma samples. The result of the analysis of the interaction among these modules showed that there was a high scale independence degree among them. The GO and KEGG enrichment analyses showed that there was a significant difference in the enriched terms and degree among these eight modules, and module 5 was identified as the most important module. Besides, the pathways it was enriched in, hsa04510: Focal adhesion and hsa04610: Complement and coagulation cascades, were determined as the most important pathways. In summary, module 5 and the pathways it was enriched in, hsa04510: Focal adhesion and has 04610: Complement and coagulation cascades, have the potential to serve as biomarkers for patients with glioma.

Brain, blood, cerebrospinal fluid, and serum biomarkers in schizophrenia

Over the last decade, finding a reliable biomarker for the early detection of schizophrenia (Scz) has been a topic of interest. The main goal of the current review is to provide a comprehensive view of the brain, blood, cerebrospinal fluid (CSF), and serum biomarkers of Scz disease. Imaging studies have demonstrated that the volumes of the corpus callosum, thalamus, hippocampal formation, subiculum, parahippocampal gyrus, superior temporal gyrus, prefrontal and orbitofrontal cortices, and amygdala-hippocampal complex were reduced in patients diagnosed with Scz. It has been revealed that the levels of interleukin 1β (IL-1β), IL-6, IL-8, and TNF-α were increased in patients with Scz. Decreased mRNA levels of brain-derived neurotrophic factor (BDNF), tropomyosin receptor kinase B (TrkB), neurotrophin-3 (NT-3), nerve growth factor (NGF), and vascular endothelial growth factor (VEGF) genes have also been reported in Scz patients. Genes with known strong relationships with this disease include BDNF, catechol-O-methyltransferase (COMT), regulator of G-protein signaling 4 (RGS4), dystrobrevin-binding protein 1 (DTNBP1), neuregulin 1 (NRG1), Reelin (RELN), Selenium-binding protein 1 (SELENBP1), glutamic acid decarboxylase 67 (GAD 67), and disrupted in schizophrenia 1 (DISC1). The levels of dopamine, tyrosine hydroxylase (TH), serotonin or 5-hydroxytryptamine (5-HT) receptor 1A and B (5-HTR1A and 5-HTR1B), and 5-HT1B were significantly increased in Scz patients, while the levels of gamma-aminobutyric acid (GABA), 5-HT transporter (5-HTT), and 5-HT receptor 2A (5-HTR2A) were decreased. The increased levels of SELENBP1 and Glycogen synthase kinase 3 subunit α (GSK3α) genes in contrast with reduced levels of B-cell translocation gene 1 (BTG1), human leukocyte antigen DRB1 (HLA-DRB1), heterogeneous nuclear ribonucleoprotein A3 (HNRPA3), and serine/arginine-rich splicing factor 1 (SFRS1) genes have also been reported. This review covers various dysregulation of neurotransmitters and also highlights the strengths and weaknesses of studies attempting to identify candidate biomarkers.