Region and diagnosis-specific changes in synaptic proteins in schizophrenia and bipolar I disorder

Biomarkers of Bipolar Disorder in Late Life: An Evidence-Based Systematic Review

PURPOSE OF REVIEW

Review the current evidence on biomarkers for bipolar disorder in the older adults. We conducted a systematic search of PubMed MEDLINE, PsycINFO, and Web of Science databases using the MeSH search terms "Biomarkers", "Bipolar Disorder", "Aged" and and "Aged, 80 and over". Studies were included if they met the following criteria: (1) the mean age of the study population was 50 years old or older, (2) the study included patients with bipolar disorder, and (3) the study examined one type of biomarkers or more including genetic, neuroimaging, and biochemical biomarkers. Reviews, case reports, studies not in English and studies for which no full text was available were excluded. A total of 26 papers were included in the final analysis.

RECENT FINDINGS

Genomic markers of bipolar disorder in older adults highlighted the implication of serotonin metabolism, while the expression of genes involved in angiogenesis was dysregulated. Peripheral blood markers were mainly related with low grade inflammation, axonal damage, endothelial dysfunction, and the dysregulation of the HPA axis. Neuroanatomical markers reflected a dysfunction of the frontal cortex, a loss of neurones in the anterior cingulate cortex and a reduction of the hippocampal volume (in patients older than 50 years old). While not necessarily limited to older adults, some of them may be useful for differential diagnosis (neurofilaments), disease staging (homocysteine, BDNF) and the monitoring of treatment outcomes (matrix metalloproteinases). Our review provides a comprehensive overview of the current evidence on biomarkers for bipolar disorder in the older adults. The identification of biomarkers may aid in the diagnosis, treatment selection, and monitoring of bipolar disorder in older adults, ultimately leading to improved outcomes for this population. Further research is needed to validate and further explore the potential clinical utility of biomarkers in this population.

The role of microglia heterogeneity in synaptic plasticity and brain disorders: Will sequencing shed light on the discovery of new therapeutic targets?

Microglia play a crucial role in interacting with neuronal synapses and modulating synaptic plasticity. This function is particularly significant during postnatal development, as microglia are responsible for removing excessive synapses to prevent neurodevelopmental deficits. Dysregulation of microglial synaptic function has been well-documented in various pathological conditions, notably Alzheimer's disease and multiple sclerosis. The recent application of RNA sequencing has provided a powerful and unbiased means to decipher spatial and temporal microglial heterogeneity. By identifying microglia with varying gene expression profiles, researchers have defined multiple subgroups of microglia associated with specific pathological states, including disease-associated microglia, interferon-responsive microglia, proliferating microglia, and inflamed microglia in multiple sclerosis, among others. However, the functional roles of these distinct subgroups remain inadequately characterized. This review aims to refine our current understanding of the potential roles of heterogeneous microglia in regulating synaptic plasticity and their implications for various brain disorders, drawing from recent sequencing research and functional studies. This knowledge may aid in the identification of pathogenetic biomarkers and potential factors contributing to pathogenesis, shedding new light on the discovery of novel drug targets. The field of sequencing-based data mining is evolving toward a multi-omics approach. With advances in viral tools for precise microglial regulation and the development of brain organoid models, we are poised to elucidate the functional roles of microglial subgroups detected through sequencing analysis, ultimately identifying valuable therapeutic targets.

Decreased serum levels of α-synuclein in patients with schizophrenia and their unaffected siblings

AIM

The final common pathway in the etiopathogenesis of schizophrenia is suggested that there is a defect in the presynaptic terminal in dopaminergic transmission, in which α-synuclein has an important role. Peripheral biomarker studies in schizophrenia have become crucial for better diagnoses, early interventions, and personalized therapies. This study aims to compare α-synuclein levels in patients with schizophrenia and their unaffected siblings with healthy controls, as a potential peripheral biomarker for schizophrenia.

METHODS

The quantifications of α-synuclein serum concentrations were conducted by the ELISA method. PANSS and CGI-S were used to analyse the severity of the symptoms of the subjects. Data were analysed by nonparametric tests and the Receiver Operating Curve (ROC) analysis.

RESULTS

Sixty-two patients with schizophrenia (mean age: 34,8 ± 9,9, %64,5 male), their 56 unaffected siblings (mean age: 39,4 ± 11,5, %55,4 male) and 56 healthy controls (mean age: 36,2 ± 9,8, %64,3 male) were included. α-synuclein levels were significantly lower in the patient (27,65 (12,61-46,09) pg/ml) and the unaffected sibling groups (24,62 (15,60-57,87) pg/ml) compared with healthy controls (45,58 (11,25-108,30) pg/ml) (p < .001). According to the ROC analysis, the optimal cut-off value for α-synuclein levels in distinguishing the schizophrenia group from the control group was 42.20. The sensitivity of the measurement of serum α-synuclein at this point was 93.5%, and the specificity was 60.7%.

CONCLUSION

Our study demonstrates that decreased levels of serum α-synuclein may be utilized as a possible peripheral biomarker of familial risk for schizophrenia in both patients and their siblings.

Dodecyl creatine ester improves cognitive function and identifies key protein drivers including KIF1A and PLCB1 in a mouse model of creatine transporter deficiency

Creatine transporter deficiency (CTD), a leading cause of intellectual disability is a result of the mutation in the gene encoding the creatine transporter SLC6A8, which prevents creatine uptake into the brain, causing mental retardation, expressive speech and language delay, autistic-like behavior and epilepsy. Preclinical in vitro and in vivo data indicate that dodecyl creatine ester (DCE) which increases the creatine brain content, might be a therapeutic option for CTD patients. To gain a better understanding of the pathophysiology and DCE treatment efficacy in CTD, this study focuses on the identification of biomarkers related to cognitive improvement in a Slc6a8 knockout mouse model (Slc6a8−/y) engineered to mimic the clinical features of CTD patients which have low brain creatine content. Shotgun proteomics analysis of 4,035 proteins in four different brain regions; the cerebellum, cortex, hippocampus (associated with cognitive functions) and brain stem, and muscle as a control, was performed in 24 mice. Comparison of the protein abundance in the four brain regions between DCE-treated intranasally Slc6a8−/y mice and wild type and DCE-treated Slc6a8−/y and vehicle group identified 14 biomarkers, shedding light on the mechanism of action of DCE. Integrative bioinformatics and statistical modeling identified key proteins in CTD, including KIF1A and PLCB1. The abundance of these proteins in the four brain regions was significantly correlated with both the object recognition and the Y-maze tests. Our findings suggest a major role for PLCB1, KIF1A, and associated molecules in the pathogenesis of CTD.

Evidence that the frontal pole has a significant role in the pathophysiology of schizophrenia

Different regions of the cortex have been implicated in the pathophysiology of schizophrenia. Recently published data suggested there are many more changes in gene expression in the frontal pole (Brodmann's Area (BA) 10) compared to the dorsolateral prefrontal cortex (BA 9) and the anterior cingulate cortex (BA 33) from patients with schizophrenia. These data argued that the frontal pole is significantly affected by the pathophysiology of schizophrenia. The frontal pole is a region necessary for higher cognitive functions and is highly interconnected with many other brain regions. In this review we summarise the growing body of evidence to support the hypothesis that a dysfunctional frontal pole, due at least in part to its widespread effects on brain function, is making an important contribution to the pathophysiology of schizophrenia. We detail the many structural, cellular and molecular abnormalities in the frontal pole from people with schizophrenia and present findings that argue the symptoms of schizophrenia are closely linked to dysfunction in this critical brain region.

Autoantibodies against NCAM1 from patients with schizophrenia cause schizophrenia-related behavior and changes in synapses in mice

From genetic and etiological studies, autoimmune mechanisms underlying schizophrenia are suspected; however, the details remain unclear. In this study, we describe autoantibodies against neural cell adhesion molecule (NCAM1) in patients with schizophrenia (5.4%, cell-based assay; 6.7%, ELISA) in a Japanese cohort (n = 223). Anti-NCAM1 autoantibody disrupts both NCAM1-NCAM1 and NCAM1-glial cell line-derived neurotrophic factor (GDNF) interactions. Furthermore, the anti-NCAM1 antibody purified from patients with schizophrenia interrupts NCAM1-Fyn interaction and inhibits phosphorylation of FAK, MEK1, and ERK1 when introduced into the cerebrospinal fluid of mice and also reduces the number of spines and synapses in frontal cortex. In addition, it induces schizophrenia-related behavior in mice, including deficient pre-pulse inhibition and cognitive impairment. In conclusion, anti-NCAM1 autoantibodies in patients with schizophrenia cause schizophrenia-related behavior and changes in synapses in mice. These antibodies may be a potential therapeutic target and serve as a biomarker to distinguish a small but treatable subgroup in heterogeneous patients with schizophrenia.

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Some patients with schizophrenia are positive for anti-NCAM1 autoantibodies

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Anti-NCAM1 antibody from schizophrenia patients inhibits NCAM1-NCAM1 interactions

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Anti-NCAM1 antibody from schizophrenia patients reduces spines and synapses in mice

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Anti-NCAM1 antibody from patients induces schizophrenia-related behavior in mice

Alterations in brain synaptic proteins and mRNAs in mood disorders: a systematic review and meta-analysis of postmortem brain studies

The pathophysiological mechanisms underlying bipolar (BD) and major depressive disorders (MDD) are multifactorial but likely involve synaptic dysfunction and dysregulation. There are multiple synaptic proteins but three synaptic proteins, namely SNAP-25, PSD-95, and synaptophysin, have been widely studied for their role in synaptic function in human brain postmortem studies in BD and MDD. These studies have yielded contradictory results, possibly due to the small sample size and sourcing material from different cortical regions of the brain. We performed a systematic review and meta-analysis to understand the role of these three synaptic proteins and other synaptic proteins, messenger RNA (mRNA) and their regional localizations in BD and MDD. A systematic literature search was conducted and the review is reported in accordance with the MOOSE Guidelines. Meta-analysis was performed to compare synaptic marker levels between BD/MDD groups and controls separately. 1811 papers were identified in the literature search and screened against the preset inclusion and exclusion criteria. A total of 72 studies were screened in the full text, of which 47 were identified as eligible to be included in the systematic review. 24 of these 47 papers were included in the meta-analysis. The meta-analysis indicated that SNAP-25 protein levels were significantly lower in BD. On average, PSD-95 mRNA levels were lower in BD, and protein levels of SNAP-25, PSD-95, and syntaxin were lower in MDD. Localization analysis showed decreased levels of PSD-95 protein in the frontal cortex. We found specific alterations in synaptic proteins and RNAs in both BD and MDD. The review was prospectively registered online in PROSPERO international prospective register of systematic reviews, registration no. CRD42020196932.

Bipolar spectrum disorders in neurologic disorders

Psychiatric symptoms frequently predate or complicate neurological disorders, such as neurodegenerative diseases. Symptoms of bipolar spectrum disorders (BSD), like mood, behavioral, and psychotic alterations, are known to occur - individually or as a syndromic cluster - in Parkinson's disease and in the behavioral variant of frontotemporal dementia (FTD). Nonetheless, due to shared pathophysiological mechanisms, or genetic predisposition, several other neurological disorders show significant, yet neglected, clinical and biological overlaps with BSD like neuroinflammation, ion channel dysfunctions, neurotransmission imbalance, or neurodegeneration. BSD pathophysiology is still largely unclear, but large-scale network dysfunctions are known to participate in the onset of mood disorders and psychotic symptoms. Thus, functional alterations can unleash BSD symptoms years before the evidence of an organic disease of the central nervous system. The aim of our narrative review was to illustrate the numerous intersections between BSD and neurological disorders from a clinical-biological point of view and the underlying predisposing factors, to guide future diagnostic and therapeutical research in the field.

Dysfunction of the SNARE complex in neurological and psychiatric disorders

The communication between neurons constitutes the basis of all neural activities, and synaptic vesicle exocytosis is the fundamental biological event that mediates most communication between neurons in the central nervous system. The SNARE complex is the core component of the protein machinery that facilitates the fusion of synaptic vesicles with presynaptic terminals and thereby the release of neurotransmitters. In synapses, each release event is dependent on the assembly of the SNARE complex. In recent years, basic research on the SNARE complex has provided a clearer understanding of the mechanism underlying the formation of the SNARE complex and its role in vesicle formation. Emerging evidence indicates that abnormal expression or dysfunction of the SNARE complex in synapse physiology might contribute to abnormal neurotransmission and ultimately to synaptic dysfunction. Clinical research using postmortem tissues suggests that SNARE complex dysfunction is correlated with various neurological diseases, and some basic research has also confirmed the important role of the SNARE complex in the pathology of these diseases. Genetic and pharmacogenetic studies suggest that the SNARE complex and individual proteins might represent important molecular targets in neurological disease. In this review, we summarize the recent progress toward understanding the SNARE complex in regulating membrane fusion events and provide an update of the recent discoveries from clinical and basic research on the SNARE complex in neurodegenerative, neuropsychiatric, and neurodevelopmental diseases.

Specificity and Continuity of Schizophrenia and Bipolar Disorder: Relation to Biomarkers

Schizophrenia and bipolar disorder overlap considerably in terms of symptoms, familial patterns, risk genes, outcome, and treatment response. This article provides an overview of the specificity and continuity of schizophrenia and mood disorders on the basis of biomarkers, such as genes, molecules, cells, circuits, physiology and clinical phenomenology. Overall, the discussions herein provided support for the view that schizophrenia, schizoaffective disorder and bipolar disorder are in the continuum of severity of impairment, with bipolar disorder closer to normality and schizophrenia at the most severe end. This approach is based on the concept that examining biomarkers in several modalities across these diseases from the dimensional perspective would be meaningful. These considerations are expected to help develop new treatments for unmet needs, such as cognitive dysfunction, in psychiatric conditions.

Transcriptomic Landscape and Functional Characterization of Induced Pluripotent Stem Cell-Derived Cerebral Organoids in Schizophrenia

IMPORTANCE

Three-dimensional cerebral organoids generated from patient-derived induced pluripotent stem cells (iPSCs) may be used to interrogate cellular-molecular underpinnings of schizophrenia.

OBJECTIVE

To determine transcriptomic profiles and functional characteristics of cerebral organoids from patients with schizophrenia using gene expression studies, complemented with investigations of mitochondrial function through measurement of real-time oxygen consumption rate, and functional studies of neuronal firing with microelectrode arrays.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study was conducted at Massachusetts General Hospital between 2017 and 2019. Transcriptomic profiling of iPSC-derived cerebral organoids from 8 patients with schizophrenia and 8 healthy control individuals was undertaken to identify cellular pathways that are aberrant in schizophrenia. Induced pluripotent stem cells and cerebral organoids were generated from patients who had been diagnosed as having schizophrenia and from heathy control individuals.

MAIN OUTCOMES AND MEASURES

Transcriptomic analysis of iPSC-derived cerebral organoids from patients with schizophrenia show differences in expression of genes involved in synaptic biology and neurodevelopment and are enriched for genes implicated in schizophrenia genome-wide association studies (GWAS).

RESULTS

The study included iPSC lines generated from 11 male and 5 female white participants, with a mean age of 38.8 years. RNA sequencing data from iPSC-derived cerebral organoids in schizophrenia showed differential expression of genes involved in synapses, in nervous system development, and in antigen processing. The differentially expressed genes were enriched for genes implicated in schizophrenia, with 23% of GWAS genes showing differential expression in schizophrenia and control organoids: 10 GWAS genes were upregulated in schizophrenia organoids while 15 GWAS genes were downregulated. Analysis of the gene expression profiles suggested dysregulation of genes involved in mitochondrial function and those involved in modulation of excitatory and inhibitory pathways. Studies of mitochondrial respiration showed lower basal consumption rate, adenosine triphosphate production, proton leak, and nonmitochondrial oxygen consumption in schizophrenia cerebral organoids, without any differences in the extracellular acidification rate. Microelectrode array studies of cerebral organoids showed no differences in baseline electrical activity in schizophrenia but revealed a diminished response to stimulation and depolarization.

CONCLUSIONS AND RELEVANCE

Investigations of patient-derived cerebral organoids in schizophrenia revealed gene expression patterns suggesting dysregulation of a number of pathways in schizophrenia, delineated differences in mitochondrial function, and showed deficits in response to stimulation and depolarization in schizophrenia.

SNAP-25 in Major Psychiatric Disorders: A Review

Synaptosomal Associated Protein-25 kilodaltons (SNAP-25) is an integral member of the SNARE complex. This complex is essential for calcium-triggered synaptic vesicular fusion and release of neurotransmitters into the synaptic cleft. In addition to neurotransmission, SNAP-25 is associated with insulin release, the regulation of intracellular calcium, and neuroplasticity. Because of SNAP-25's varied and crucial biological roles, the consequences of changes in this protein can be seen in both the central nervous system and the periphery. In this review, we will look at the published literature from human genetic, postmortem, and animal studies involving SNAP-25. The accumulated data indicate that SNAP-25 may be linked with some symptoms associated with a variety of psychiatric disorders. These disorders include bipolar disorder, schizophrenia, major depressive disorder, attention deficit hyperactivity disorder, autism, alcohol use disorder, and dementia. There are also data suggesting SNAP-25 may be involved with non-psychiatric seizures and metabolic disorders. We believe investigation of SNAP-25 is important for understanding both normal behavior and some aspects of the pathophysiology of behavior seen with psychiatric disorders. The wealth of information from both animal and human studies on SNAP-25 offers an excellent opportunity to use a bi-directional research approach. Hypotheses generated from genetically manipulated mice can be directly tested in human postmortem tissue, and, conversely, human genetic and postmortem findings can improve and validate animal models for psychiatric disorders.

Synaptic loss in schizophrenia: a meta-analysis and systematic review of synaptic protein and mRNA measures

Although synaptic loss is thought to be core to the pathophysiology of schizophrenia, the nature, consistency and magnitude of synaptic protein and mRNA changes has not been systematically appraised. Our objective was thus to systematically review and meta-analyse findings. The entire PubMed database was searched for studies from inception date to the 1st of July 2017. We selected case-control postmortem studies in schizophrenia quantifying synaptic protein or mRNA levels in brain tissue. The difference in protein and mRNA levels between cases and controls was extracted and meta-analysis conducted. Among the results, we found a significant reduction in synaptophysin in schizophrenia in the hippocampus (effect size: -0.65, p < 0.01), frontal (effect size: -0.36, p = 0.04), and cingulate cortices (effect size: -0.54, p = 0.02), but no significant changes for synaptophysin in occipital and temporal cortices, and no changes for SNAP-25, PSD-95, VAMP, and syntaxin in frontal cortex. There were insufficient studies for meta-analysis of complexins, synapsins, rab3A and synaptotagmin and mRNA measures. Findings are summarised for these, which generally show reductions in SNAP-25, PSD-95, synapsin and rab3A protein levels in the hippocampus but inconsistency in other regions. Our findings of moderate-large reductions in synaptophysin in hippocampus and frontal cortical regions, and a tendency for reductions in other pre- and postsynaptic proteins in the hippocampus are consistent with models that implicate synaptic loss in schizophrenia. However, they also identify potential differences between regions and proteins, suggesting synaptic loss is not uniform in nature or extent.

Effects of haloperidol and clozapine on synapse-related gene expression in specific brain regions of male rats

We investigated the effects of clozapine and haloperidol, drugs that are widely used in the treatment of schizophrenia, on gene expression in six cortical and subcortical brain regions of adult rats. Drug treatments started at postnatal day 85 and continued over a 12-week period. Ten animals received haloperidol (1 mg/kg bodyweight) and ten received clozapine (20 mg/kg bodyweight) orally each day. Ten control rats received no drugs. The ten genes selected for this study did not belong to the dopaminergic or serotoninergic systems, which are typically targeted by the two substances, but coded for proteins of the cytoskeleton and proteins belonging to the synaptic transmitter release machinery. Quantitative real-time PCR was performed in the prelimbic cortex, cingulate gyrus (CG1) and caudate putamen and in the hippocampal cornu ammonis 1 (CA1), cornu ammonis 3 (CA3) and dentate gyrus. Results show distinct patterns of gene expression under the influence of the two drugs, but also distinct gene regulations dependent on the brain regions. Haloperidol-medicated animals showed statistically significant downregulation of SNAP-25 in CA3 (p = 0.0134) and upregulation of STX1A in CA1 (p = 0.0133) compared to controls. Clozapine-treated animals showed significant downregulation of SNAP-25 in CG1 (p = 0.0013). Our results clearly reveal that the drugs' effects are different between brain regions. These effects are possibly indirectly mediated through feedback mechanisms by proteins targeted by the drugs, but direct effects of haloperidol or clozapine on mechanisms of gene expression cannot be excluded.

HDAC1 and HDAC3 underlie dynamic H3K9 acetylation during embryonic neurogenesis and in schizophrenia-like animals

Although histone acetylation is one of the most widely studied epigenetic modifications, there is still a lack of information regarding how the acetylome is regulated during brain development and pathophysiological processes. We demonstrate that the embryonic brain (E15) is characterized by an increase in H3K9 acetylation as well as decreases in the levels of HDAC1 and HDAC3. Moreover, experimental induction of H3K9 hyperacetylation led to the overexpression of NCAM in the embryonic cortex and depletion of Sox2 in the subventricular ependyma, which mimicked the differentiation processes. Inducing differentiation in HDAC1-deficient mouse ESCs resulted in early H3K9 deacetylation, Sox2 downregulation, and enhanced astrogliogenesis, whereas neuro-differentiation was almost suppressed. Neuro-differentiation of (wt) ESCs was characterized by H3K9 hyperacetylation that was associated with HDAC1 and HDAC3 depletion. Conversely, the hippocampi of schizophrenia-like animals showed H3K9 deacetylation that was regulated by an increase in both HDAC1 and HDAC3. The hippocampi of schizophrenia-like brains that were treated with the cannabinoid receptor-1 inverse antagonist AM251 expressed H3K9ac at the level observed in normal brains. Together, the results indicate that co-regulation of H3K9ac by HDAC1 and HDAC3 is important to both embryonic brain development and neuro-differentiation as well as the pathophysiology of a schizophrenia-like phenotype.

A Multilevel Functional Study of a SNAP25 At-Risk Variant for Bipolar Disorder and Schizophrenia

The synaptosomal-associated protein SNAP25 is a key player in synaptic vesicle docking and fusion and has been associated with multiple psychiatric conditions, including schizophrenia, bipolar disorder, and attention-deficit/hyperactivity disorder. We recently identified a promoter variant in SNAP25, rs6039769, that is associated with early-onset bipolar disorder and a higher gene expression level in human prefrontal cortex. In the current study, we showed that this variant was associated both in males and females with schizophrenia in two independent cohorts. We then combined in vitro and in vivo approaches in humans to understand the functional impact of the at-risk allele. Thus, we showed in vitro that the rs6039769 C allele was sufficient to increase the SNAP25 transcription level. In a postmortem expression analysis of 33 individuals affected with schizophrenia and 30 unaffected control subjects, we showed that the SNAP25b/SNAP25a ratio was increased in schizophrenic patients carrying the rs6039769 at-risk allele. Last, using genetics imaging in a cohort of 71 subjects, we showed that male risk carriers had an increased amygdala-ventromedial prefrontal cortex functional connectivity and a larger amygdala than non-risk carriers. The latter association has been replicated in an independent cohort of 121 independent subjects. Altogether, results from these multilevel functional studies are bringing strong evidence for the functional consequences of this allelic variation of SNAP25 on modulating the development and plasticity of the prefrontal-limbic network, which therefore may increase the vulnerability to both early-onset bipolar disorder and schizophrenia.SIGNIFICANCE STATEMENT Functional characterization of disease-associated variants is a key challenge in understanding neuropsychiatric disorders and will open an avenue in the development of personalized treatments. Recent studies have accumulated evidence that the SNARE complex, and more specifically the SNAP25 protein, may be involved in psychiatric disorders. Here, our multilevel functional studies are bringing strong evidence for the functional consequences of an allelic variation of SNAP25 on modulating the development and plasticity of the prefrontal-limbic network. These results demonstrate a common genetically driven functional alteration of a synaptic mechanism both in schizophrenia and early-onset bipolar disorder and confirm the shared genetic vulnerability between these two disorders.

Neural Cell Adhesion Molecules of the Immunoglobulin Superfamily Regulate Synapse Formation, Maintenance, and Function

Immunoglobulin superfamily adhesion molecules are among the most abundant proteins in vertebrate and invertebrate nervous systems. Prominent family members are the neural cell adhesion molecules NCAM and L1, which were the first to be shown to be essential not only in development but also in synaptic function and as key regulators of synapse formation, synaptic activity, plasticity, and synaptic vesicle recycling at distinct developmental and activity stages. In addition to interacting with each other, adhesion molecules interact with ion channels and cytokine and neurotransmitter receptors. Mutations in their genes are linked to neurological disorders associated with abnormal development and synaptic functioning. This review presents an overview of recent studies on these molecules and their crucial impact on neurological disorders.

NCAM Regulates Inhibition and Excitability in Layer 2/3 Pyramidal Cells of Anterior Cingulate Cortex

The neural cell adhesion molecule (NCAM), has been shown to be an obligate regulator of synaptic stability and pruning during critical periods of cortical maturation. However, the functional consequences of NCAM deletion on the organization of inhibitory circuits in cortex are not known. In vesicular gamma-amino butyric acid (GABA) transporter (VGAT)-channelrhodopsin2 (ChR2)-enhanced yellow fluorescent protein (EYFP) transgenic mice, NCAM is expressed postnatally at perisomatic synaptic puncta of EYFP-labeled parvalbumin, somatostatin and calretinin-positive interneurons, and in the neuropil in the anterior cingulate cortex (ACC). To investigate how NCAM deletion affects the spatial organization of inhibitory inputs to pyramidal cells, we used laser scanning photostimulation in brain slices of VGAT-ChR2-EYFP transgenic mice crossed to either NCAM-null or wild type (WT) mice. Laser scanning photostimulation revealed that NCAM deletion increased the strength of close-in inhibitory connections to layer 2/3 pyramidal cells of the ACC. In addition, in NCAM-null mice, the intrinsic excitability of pyramidal cells increased, whereas the intrinsic excitability of GABAergic interneurons did not change. The increase in inhibitory tone onto pyramidal cells, and the increased pyramidal cell excitability in NCAM-null mice will alter the delicate coordination of excitation and inhibition (E/I coordination) in the ACC, and may be a factor contributing to circuit dysfunction in diseases such as schizophrenia and bipolar disorder, in which NCAM has been implicated.

Diagnostic and therapeutic potential of microRNAs in neuropsychiatric disorders: Past, present, and future

Neuropsychiatric disorders are common health problems affecting approximately 1% of the population. Twin, adoption, and family studies have displayed a strong genetic component for many of these disorders; however, the underlying pathophysiological mechanisms and neural substrates remain largely unknown. Given the critical need for new diagnostic markers and disease-modifying treatments, expanding the focus of genomic studies of neuropsychiatric disorders to include the role of non-coding RNAs (ncRNAs) is of growing interest. Of known types of ncRNAs, microRNAs (miRNAs) are 20-25-nucleotide, single-stranded, molecules that regulate gene expression through post-transcriptional mechanisms and have the potential to coordinately regulate complex regulatory networks. In this review, we summarize the current knowledge on miRNA alteration/dysregulation in neuropsychiatric disorders, with a special emphasis on schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD). With an eye toward the future, we also discuss the diagnostic and prognostic potential of miRNAs for neuropsychiatric disorders in the context of personalized treatments and network medicine.

The Neural Cell Adhesion Molecule (NCAM) Promotes Clustering and Activation of EphA3 Receptors in GABAergic Interneurons to Induce Ras Homolog Gene Family, Member A (RhoA)/Rho-associated protein kinase (ROCK)-mediated Growth Cone Collapse

Establishment of a proper balance of excitatory and inhibitory connectivity is achieved during development of cortical networks and adjusted through synaptic plasticity. The neural cell adhesion molecule (NCAM) and the receptor tyrosine kinase EphA3 regulate the perisomatic synapse density of inhibitory GABAergic interneurons in the mouse frontal cortex through ephrin-A5-induced growth cone collapse. In this study, it was demonstrated that binding of NCAM and EphA3 occurred between the NCAM Ig2 domain and EphA3 cysteine-rich domain (CRD). The binding interface was further refined through molecular modeling and mutagenesis and shown to be comprised of complementary charged residues in the NCAM Ig2 domain (Arg-156 and Lys-162) and the EphA3 CRD (Glu-248 and Glu-264). Ephrin-A5 induced co-clustering of surface-bound NCAM and EphA3 in GABAergic cortical interneurons in culture. Receptor clustering was impaired by a charge reversal mutation that disrupted NCAM/EphA3 association, emphasizing the importance of the NCAM/EphA3 binding interface for cluster formation. NCAM enhanced ephrin-A5-induced EphA3 autophosphorylation and activation of RhoA GTPase, indicating a role for NCAM in activating EphA3 signaling through clustering. NCAM-mediated clustering of EphA3 was essential for ephrin-A5-induced growth cone collapse in cortical GABAergic interneurons, and RhoA and a principal effector, Rho-associated protein kinase, mediated the collapse response. This study delineates a mechanism in which NCAM promotes ephrin-A5-dependent clustering of EphA3 through interaction of the NCAM Ig2 domain and the EphA3 CRD, stimulating EphA3 autophosphorylation and RhoA signaling necessary for growth cone repulsion in GABAergic interneurons in vitro, which may extend to remodeling of axonal terminals of interneurons in vivo.

Select putative neurodevelopmental toxins modify SNAP-25 expression in primary cultures of rat cerebellar granule cells

A presynaptic protein SNAP-25 belonging to SNARE complex which is instrumental in intracellular vesicular trafficking and exocytosis, has been implicated in hyperactivity and cognitive abilities in some neuropsychiatric disorders. The unclear etiology of the behavior disrupting neurodevelopmental disabilities in addition to genetic causes most likely involves environmental factors. The aim of this in vitro study was to test if various suspected developmental neurotoxins can alter SNAP-25 mRNA and protein expression in neurons. Real-time PCR and Western blotting analyses were used to assess SNAP-25 mRNA and protein levels in primary cultures of rat cerebellar granule cells (CGCs). The test substances: tetrabromobisphenol-A (TBBPA), thimerosal (TH), silver nanoparticles (NAg), valproic acid (VPA) and thalidomide (THAL), were administered to CGC cultures at subtoxic concentrations for 24h. The results demonstrated that SNAP-25 mRNA levels were increased by 49 and 66% by TBBPA and THAL, respectively, whereas VPA and NAg reduced these levels to 48 and 64% of the control, respectively. The SNAP-25 protein content in CGCs was increased by 79% by TBBPA, 25% by THAL and 21% by NAg; VPA and TH reduced these levels to 73 and 69% of the control, respectively. The variety of changes in SNAP-25 expression on mRNA and protein level suggests the diversity of the mechanism of action of the test substances. This initial study provided no data on concentration-effect relations and on functional changes in CGCs. However it is the first to demonstrate the effect of different compounds that are suspected of causing neurodevelopmental disabilities on SNAP-25 expression. These results suggest that this protein may be a common target for not only inherited but also environmental modifications linked to behavioral deficits in neurodevelopmental disabilities.

Dysregulations of Synaptic Vesicle Trafficking in Schizophrenia

Schizophrenia is a serious psychiatric illness which is experienced by about 1 % of individuals worldwide and has a debilitating impact on perception, cognition, and social function. Over the years, several models/hypotheses have been developed which link schizophrenia to dysregulations of the dopamine, glutamate, and serotonin receptor pathways. An important segment of these pathways that have been extensively studied for the pathophysiology of schizophrenia is the presynaptic neurotransmitter release mechanism. This set of molecular events is an evolutionarily well-conserved process that involves vesicle recruitment, docking, membrane fusion, and recycling, leading to efficient neurotransmitter delivery at the synapse. Accumulated evidence indicate dysregulation of this mechanism impacting postsynaptic signal transduction via different neurotransmitters in key brain regions implicated in schizophrenia. In recent years, after ground-breaking work that elucidated the operations of this mechanism, research efforts have focused on the alterations in the messenger RNA (mRNA) and protein expression of presynaptic neurotransmitter release molecules in schizophrenia and other neuropsychiatric conditions. In this review article, we present recent evidence from schizophrenia human postmortem studies that key proteins involved in the presynaptic release mechanism are dysregulated in the disorder. We also discuss the potential impact of dysfunctional presynaptic neurotransmitter release on the various neurotransmitter systems implicated in schizophrenia.

Deficits in axon-associated proteins in prefrontal white matter in bipolar disorder but not schizophrenia

OBJECTIVES

Brain imaging studies have implicated white matter dysfunction in the pathophysiology of both bipolar disorder (BD) and schizophrenia (SCZ). However, the contribution of axons to white matter pathology in these disorders is not yet understood. Maintenance of neuronal function is dependent on the active transport of biological material, including synaptic proteins, along the axon. In this study, the expression of six proteins associated with axonal transport of synaptic cargoes was quantified in postmortem samples of prefrontal white matter in subjects with BD, those with SCZ, and matched controls, as a measure of axonal dysfunction in these disorders.

METHODS

Levels of the microtubule-associated proteins β-tubulin and microtubule-associated protein 6 (MAP6), the motor and accessory proteins kinesin-1 and disrupted-in-schizophrenia 1 (DISC1), and the synaptic cargoes synaptotagmin and synaptosomal-associated protein-25 (SNAP-25) were quantified in white matter adjacent to the dorsolateral prefrontal cortex in subjects with BD (n = 34), subjects with SCZ (n = 35), and non-psychiatric controls (n = 35) using immunoblotting and an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Protein expression of β-tubulin, kinesin-1, DISC1, synaptotagmin, and SNAP-25 was significantly lower in subjects with BD compared to controls. Levels of axon-associated proteins were also lower in subjects with SCZ, but failed to reach statistical significance.

CONCLUSIONS

These data provide evidence for deficits in axon-associated proteins in prefrontal white matter in BD. Findings are suggestive of decreased axonal density or dysregulation of axonal function in this disorder.

Reciprocal Interactions between Cell Adhesion Molecules of the Immunoglobulin Superfamily and the Cytoskeleton in Neurons

Cell adhesion molecules of the immunoglobulin superfamily (IgSF) including the neural cell adhesion molecule (NCAM) and members of the L1 family of neuronal cell adhesion molecules play important functions in the developing nervous system by regulating formation, growth and branching of neurites, and establishment of the synaptic contacts between neurons. In the mature brain, members of IgSF regulate synapse composition, function, and plasticity required for learning and memory. The intracellular domains of IgSF cell adhesion molecules interact with the components of the cytoskeleton including the submembrane actin-spectrin meshwork, actin microfilaments, and microtubules. In this review, we summarize current data indicating that interactions between IgSF cell adhesion molecules and the cytoskeleton are reciprocal, and that while IgSF cell adhesion molecules regulate the assembly of the cytoskeleton, the cytoskeleton plays an important role in regulation of the functions of IgSF cell adhesion molecules. Reciprocal interactions between NCAM and L1 family members and the cytoskeleton and their role in neuronal differentiation and synapse formation are discussed in detail.

SNAP-25a/b Isoform Levels in Human Brain Dorsolateral Prefrontal Cortex and Anterior Cingulate Cortex

SNAP-25 is a neurotransmitter vesicular docking protein which has been associated with brain disorders such as attention deficit hyperactivity disorder, bipolar disorder and schizophrenia. In this project, we were interested if clinical factors are associated with differential SNAP-25 expression. We examined the SNAP-25 isoform mRNA and protein levels in postmortem cortex Brodmann's area 9 (BA9) and BA24 (n = 29). Subjects were divided by psychiatric diagnosis, clinical variables including mood state in the last week of life and lifetime impulsiveness. We found affected subjects with a diagnosis of alcohol use disorder (AUD) had a lower level of SNAP-25b BA24 protein compared to those without AUD. Hispanic subjects had lower levels of SNAP-25a, b and BA9 mRNA than Anglo-American subjects. Subjects who smoked had a total pan (total) SNAP-25 BA9/BA24 ratio. Subjects in the group with a low level of anxious-psychotic symptoms had higher SNAP-25a BA24 mRNA compared to normal controls, and both the high and low symptoms groups had higher pan (total) SNAP-25 BA9/BA24 ratios than normal controls. These data expand our understanding of clinical factors associated with SNAP-25. They suggest that SNAP-25 total and isoform levels may be useful biomarkers beyond limited neurological and psychiatric diagnostic categories.

Molecular evidence for decreased synaptic efficacy in the postmortem olfactory bulb of individuals with schizophrenia

Multiple lines of evidence suggest altered synaptic plasticity/connectivity as a pathophysiologic mechanism for various symptom domains of schizophrenia. Olfactory dysfunction, an endophenotype of schizophrenia, reflects altered activity of the olfactory circuitry, which conveys signals from olfactory receptor neurons to the olfactory cortex via synaptic connections in the glomeruli of the olfactory bulb. The olfactory system begins with intranasal olfactory receptor neuron axons synapsing with mitral and tufted cells in the glomeruli of the olfactory bulb, which then convey signals directly to the olfactory cortex. We hypothesized that olfactory dysfunction in schizophrenia is associated with dysregulation of synaptic efficacy in the glomeruli of the olfactory bulb. To test this, we employed semi-quantitative immunohistochemistry to examine the olfactory bulbs of 13 postmortem samples from schizophrenia and their matched control pairs for glomerular expression of 5 pre- and postsynaptic proteins that are involved in the integrity and function of synapses. In the glomeruli of schizophrenia cases compared to their matched controls, we found significant decreases in three presynaptic proteins which play crucial roles in vesicular glutamate transport - synapsin IIa (-18.05%, p=0.019), synaptophysin (-24.08% p=0.0016) and SNAP-25 (-23.9%, p=0.046). Two postsynaptic proteins important for spine formation and glutamatergic signaling were also decreased-spinophilin (-17.40%, p=0.042) and PSD-95 (-34.06%, p=0.015). These findings provide molecular evidence for decreased efficacy of synapses within the olfactory bulb, which may represent a synaptic mechanism underlying olfactory dysfunction in schizophrenia.

Are ICAM, VCAM and E-selectin levels different in first manic episode and subsequent remission?

OBJECTIVE

In bipolar patients, the rate of mortality from cardiovascular diseases is two-fold higher than that in other psychiatric disorders. The risk of cardiovascular diseases was found to be associated with some cellular adhesion molecules: Intracellular adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM) and E-selectin. The aim of this study was to compare ICAM, VCAM and E-selectin levels at first manic episode and subsequent remission period, and to investigate the presence of a relationship between adhesion molecules levels and clinical and metabolic variables.

METHODS

In line with this purpose, 50 patients diagnosed with mania according to DSM IV-TR criteria, who had their first episode were evaluated consecutively. The control group consisted of 50 healthy individuals without any history of psychiatric admission and treatment, matched with the manic patients in terms of age, gender, BMI and smoking status. For the confirmation of subsequent remission period (n=40), Young Mania Rating Scale and Hamilton Depression Rating Scale were used. In three groups plasma ICAM, VCAM and E-selectin, fasting blood glucose, total cholesterol, LDL cholesterol, HDL cholesterol and triglyceride levels were measured and compared.

RESULTS

ICAM and VCAM levels were found to be higher in first manic episode than those in subsequent remission and healthy individuals. A weak correlation was found between ICAM levels and YMRS scores in manic patients. In first manic episode, a weak correlation was found between ICAM and total cholesterol and LDL cholesterol levels and a weak correlation was found between ICAM, VCAM and E-selectin levels and BMI.

CONCLUSION

In the present study, which is the first investigation of proinflammatory and prothrombotic state, which is defined as a risk for metabolic syndrome and cardiovascular disease, in bipolar disorder, ICAM and VCAM levels were found to be higher in first episode mania than those in subsequent remission and healthy individuals. As the study group included first episode mani cases, there was no effect of chronic psychotropic use. Probable risk of cardiovascular disease, reflected by increased ICAM and VCAM levels is already present in bipolar patients at the onset of the disease. In addition, ICAM and VCAM levels increasing in manic episode, return to normal in the subsequent remission period.

Building a better dynasore: the dyngo compounds potently inhibit dynamin and endocytosis

Dynamin GTPase activity increases when it oligomerizes either into helices in the presence of lipid templates or into rings in the presence of SH3 domain proteins. Dynasore is a dynamin inhibitor of moderate potency (IC₅₀ ~ 15 μM in vitro). We show that dynasore binds stoichiometrically to detergents used for in vitro drug screening, drastically reducing its potency (IC₅₀ = 479 μM) and research tool utility. We synthesized a focused set of dihydroxyl and trihydroxyl dynasore analogs called the Dyngo™ compounds, five of which had improved potency, reduced detergent binding and reduced cytotoxicity, conferred by changes in the position and/or number of hydroxyl substituents. The Dyngo compound 4a was the most potent compound, exhibiting a 37-fold improvement in potency over dynasore for liposome-stimulated helical dynamin activity. In contrast, while dynasore about equally inhibited dynamin assembled in its helical or ring states, 4a and 6a exhibited >36-fold reduced activity against rings, suggesting that they can discriminate between helical or ring oligomerization states. 4a and 6a inhibited dynamin-dependent endocytosis of transferrin in multiple cell types (IC₅₀ of 5.7 and 5.8 μM, respectively), at least sixfold more potently than dynasore, but had no effect on dynamin-independent endocytosis of cholera toxin. 4a also reduced synaptic vesicle endocytosis and activity-dependent bulk endocytosis in cultured neurons and synaptosomes. Overall, 4a and 6a are improved and versatile helical dynamin and endocytosis inhibitors in terms of potency, non-specific binding and cytotoxicity. The data further suggest that the ring oligomerization state of dynamin is not required for clathrin-mediated endocytosis.

Rethinking schizophrenia in the context of normal neurodevelopment

The schizophrenia brain is differentiated from the normal brain by subtle changes, with significant overlap in measures between normal and disease states. For the past 25 years, schizophrenia has increasingly been considered a neurodevelopmental disorder. This frame of reference challenges biological researchers to consider how pathological changes identified in adult brain tissue can be accounted for by aberrant developmental processes occurring during fetal, childhood, or adolescent periods. To place schizophrenia neuropathology in a neurodevelopmental context requires solid, scrutinized evidence of changes occurring during normal development of the human brain, particularly in the cortex; however, too often data on normative developmental change are selectively referenced. This paper focuses on the development of the prefrontal cortex and charts major molecular, cellular, and behavioral events on a similar time line. We first consider the time at which human cognitive abilities such as selective attention, working memory, and inhibitory control mature, emphasizing that attainment of full adult potential is a process requiring decades. We review the timing of neurogenesis, neuronal migration, white matter changes (myelination), and synapse development. We consider how molecular changes in neurotransmitter signaling pathways are altered throughout life and how they may be concomitant with cellular and cognitive changes. We end with a consideration of how the response to drugs of abuse changes with age. We conclude that the concepts around the timing of cortical neuronal migration, interneuron maturation, and synaptic regression in humans may need revision and include greater emphasis on the protracted and dynamic changes occurring in adolescence. Updating our current understanding of post-natal neurodevelopment should aid researchers in interpreting gray matter changes and derailed neurodevelopmental processes that could underlie emergence of psychosis.

miR-153 regulates SNAP-25, synaptic transmission, and neuronal development

SNAP-25 is a core component of the trimeric SNARE complex mediating vesicle exocytosis during membrane addition for neuronal growth, neuropeptide/growth factor secretion, and neurotransmitter release during synaptic transmission. Here, we report a novel microRNA mechanism of SNAP-25 regulation controlling motor neuron development, neurosecretion, synaptic activity, and movement in zebrafish. Loss of miR-153 causes overexpression of SNAP-25 and consequent hyperactive movement in early zebrafish embryos. Conversely, overexpression of miR-153 causes SNAP-25 down regulation resulting in near complete paralysis, mimicking the effects of treatment with Botulinum neurotoxin. miR-153-dependent changes in synaptic activity at the neuromuscular junction are consistent with the observed movement defects. Underlying the movement defects, perturbation of miR-153 function causes dramatic developmental changes in motor neuron patterning and branching. Together, our results indicate that precise control of SNAP-25 expression by miR-153 is critically important for proper neuronal patterning as well as neurotransmission.

Regulation of intracellular membrane trafficking and cell dynamics by syntaxin-6

Intracellular membrane trafficking along endocytic and secretory transport pathways plays a critical role in diverse cellular functions including both developmental and pathological processes. Briefly, proteins and lipids destined for transport to distinct locations are collectively assembled into vesicles and delivered to their target site by vesicular fusion. SNARE (soluble N-ethylmaleimide-sensitive factor-attachment protein receptor) proteins are required for these events, during which v-SNAREs (vesicle SNAREs) interact with t-SNAREs (target SNAREs) to allow transfer of cargo from donor vesicle to target membrane. Recently, the t-SNARE family member, syntaxin-6, has been shown to play an important role in the transport of proteins that are key to diverse cellular dynamic processes. In this paper, we briefly discuss the specific role of SNAREs in various mammalian cell types and comprehensively review the various roles of the Golgi- and endosome-localized t-SNARE, syntaxin-6, in membrane trafficking during physiological as well as pathological conditions.

Are NCAM deficient mice an animal model for schizophrenia?

Genetic and biomarker studies in patients have identified the Neural Cell Adhesion Molecule (NCAM) and its associated polysialic acid (PSA) as a susceptibility factors for schizophrenia. NCAM and polysialtransferase mutant mice have been generated that may serve as animal models for this disorder and allow to investigate underlying neurodevelopmental alterations. Indeed, various schizophrenia-relevant morphological, cognitive and emotional deficits have been observed in these mutants. Here we studied social interaction and attention of NCAM null mutant (NCAM^−/−) mice as further hallmarks of schizophrenia. Nest building, which is generally associated with social behavior in rodents, was severely impaired, as NCAM^−/− mice continuously collected smaller amounts of nest building material than their wild type littermates and built nests of poorer quality. However, social approach tested in a three—compartment—box was not affected and latent inhibition of Pavlovian fear memory was not disturbed in NCAM^−/− mice. Although NCAM deficient mice do not display a typical schizophrenia-like phenotype, they may be useful for studying specific endophenotypes with relevance to the disease.

Partitioning the proteome: phase separation for targeted analysis of membrane proteins in human post-mortem brain

Neuroproteomics is a powerful platform for targeted and hypothesis driven research, providing comprehensive insights into cellular and sub-cellular disease states, Gene × Environmental effects, and cellular response to medication effects in human, animal, and cell culture models. Analysis of sub-proteomes is becoming increasingly important in clinical proteomics, enriching for otherwise undetectable proteins that are possible markers for disease. Membrane proteins are one such sub-proteome class that merit in-depth targeted analysis, particularly in psychiatric disorders. As membrane proteins are notoriously difficult to analyse using traditional proteomics methods, we evaluate a paradigm to enrich for and study membrane proteins from human post-mortem brain tissue. This is the first study to extensively characterise the integral trans-membrane spanning proteins present in human brain. Using Triton X-114 phase separation and LC-MS/MS analysis, we enriched for and identified 494 membrane proteins, with 194 trans-membrane helices present, ranging from 1 to 21 helices per protein. Isolated proteins included glutamate receptors, G proteins, voltage gated and calcium channels, synaptic proteins, and myelin proteins, all of which warrant quantitative proteomic investigation in psychiatric and neurological disorders. Overall, our sub-proteome analysis reduced sample complexity and enriched for integral membrane proteins by 2.3 fold, thus allowing for more manageable, reproducible, and targeted proteomics in case vs. control biomarker studies. This study provides a valuable reference for future neuroproteomic investigations of membrane proteins, and validates the use Triton X-114 detergent phase extraction on human post mortem brain.

Altered neuronal markers following treatment with mood stabilizer and antipsychotic drugs indicate an increased likelihood of neurotransmitter release

Objective

Given the ability of mood stabilizers and antipsychotics to promote cell proliferation, we wanted to determine the effects of these drugs on neuronal markers previously reported to be altered in subjects with psychiatric disorders.

Methods

Male Sprauge-Dawley rats were treated with vehicle (ethanol), lithium (25.5 mg per day), haloperidol (0.1 mg/kg), olanzapine (1.0 mg/kg) or a combination of lithium and either of the antipsychotic drugs for 28 days. Levels of cortical synaptic (synaptosomal associated protein-25, synaptophysin, vesicle associated protein and syntaxin) and structural (neural cell adhesion molecule and alpha-synuclein) proteins were determined in each treatment group using Western blots.

Results

Compared to the vehicle treated group; animals treated with haloperidol had greater levels of synaptosomal associated protein-25 (p<0.01) and neural cell adhesion molecule (p<0.05), those treated with olanzapine had greater levels of synaptophysin (p<0.01) and syntaxin (p<0.01). Treatment with lithium alone did not affect the levels of any of the proteins. Combining lithium and haloperidol resulted in greater levels of synaptophysin (p<0.01), synaptosomal associated protein-25 (p<0.01) and neural cell adhesion molecule (p<0.01). The combination of lithium and olanzapine produced greater levels of synaptophysin (p<0.01) and alpha-synuclein (p<0.05).

Conclusion

Lithium alone had no effect on the neuronal markers. However, haloperidol and olanzapine affected different presynaptic markers. Combining lithium with olanzapine additionally increased alpha-synuclein. These drug effects need to be taken into account by future studies examining presynaptic and neuronal markers in tissue from subjects with psychiatric disorders.

Dynamics of subcellular proteomes during brain development

Many neurological disorders are caused by perturbations during brain development, but these perturbations cannot be readily identified until there is comprehensive description of the development process. In this study, we performed mass spectrometry analysis of the synaptosomal and mitochondrial fractions from three rat brain regions at four postnatal time points. To quantitate our analysis, we employed (15)N labeled rat brains using a technique called SILAM (stable isotope labeling in mammals). We quantified 167429 peptides and identified over 5000 statistically significant changes during development including known disease-associated proteins. Global analysis revealed distinct trends between the synaptic and nonsynaptic mitochondrial proteomes and common protein networks between regions each consisting of a unique array of expression patterns. Finally, we identified novel regulators of neurodevelopment that possess the identical temporal pattern of known regulators of neurodevelopment. Overall, this study is the most comprehensive quantitative analysis of the developing brain proteome to date, providing an important resource for neurobiologists.

Neuritic growth impairment and cell death by unconjugated bilirubin is mediated by NO and glutamate, modulated by microglia, and prevented by glycoursodeoxycholic acid and interleukin-10

Neuronal oxidative damage and cell death by unconjugated bilirubin (UCB) showed to be mediated by overstimulation of glutamate receptors and nitric oxide (NO) production, which was abrogated by the bile acid glycoursodeoxycholic acid (GUDCA). Microglia, a crucial mediator of CNS inflammation, evidenced to react to UCB by releasing glutamate and NO before becoming senescent. Our studies demonstrated that neurite outgrowth deficits are produced in neurons exposed to UCB and that conditioned media from these UCB-treated neurons further stimulate NO production by microglia. Nevertheless, microglia protective and/or harmful effects in neonatal jaundice are poorly understood, or unrecognized. Here, we investigated the role of microglia, glutamate and NO in the impairment of neurite sprouting by UCB. Therapeutic potential of the anti-inflammatory cytokine interleukin (IL)-10 and GUDCA was also evaluated. By using MK-801 (a NMDA glutamate-subtype receptor antagonist) and L-NAME (a non-specific NO synthase inhibitor) we found that glutamate and NO are determinants in the early and enduring deficits in neurite extension and ramification induced by UCB. Both GUDCA and IL-10 prevented these effects and decreased the production of glutamate and NO. Only GUDCA was able to counteract neuronal death and synaptic changes. Data from organotypic-cultured hippocampal slices, depleted or non-depleted in microglia, supported that microglia participate in glutamate homeostasis and contribute to NO production and cell demise, which were again abrogated by GUDCA. Collectively our data suggest that microglia is a key player in UCB-induced neurotoxicity and that GUDCA might be a valuable preventive therapy in neonates at risk of UCB encephalopathy.

Tyrosine kinase B protein expression is reduced in the cerebellum of patients with bipolar disorder

BACKGROUND

The role of the cerebellum in coordinating mental activity is supported by its connections with cerebral regions involved in cognitive/affective functioning, with decreased activities on functional neuroimaging observed in the cerebellum of schizophrenia patients performing mental tasks. Brain-derived neurotrophic factor (BDNF)-induced activation of tyrosine kinase B (TrkB) is essential to synaptic plasticity. We hypothesized that alterations in BDNF and TrkB expression in the cerebellum were associated with schizophrenia and affective disorders.

METHODS

We employed immunohistochemistry and immunoblotting to quantify protein expression of BDNF and TrkB in the cerebellum of patients with schizophrenia, bipolar disorder, and major depression compared to controls (n=15 each).

RESULTS

While TrkB immunoreactivity in each of the molecular and granule-cell layers was reduced in all 3 disease groups (12-34%) compared to the control (P=0.018 and 0.038, respectively, ANOVA), only the reduction in bipolar disorder remained statistically significant upon Tukey-Kramer post hoc analyses (P=0.019 and 0.021, respectively). Apparent decreases in BDNF immunoreactivity in all 3 disease groups (12-30%) compared to the control were not statistically significant. TrkB immunoreactivity was not significantly associated with any of the demographic, clinical, and postmortem variables. Immunoblotting displayed an 85-kDa TrkB-immunoreactive band, consistent with a truncated isoform, in all 60 cases.

LIMITATIONS

On immunoblotting, apparent decreases in 85-kDa-TrkB levels in all 3 disease groups compared to the control were not statistically significant.

CONCLUSIONS

Our finding of reduced TrkB expression in bipolar disorder suggests that dysregulation of TrkB-mediated neurotrophin signaling in the cerebellum may play a role in the pathophysiology of this disease.

Expression of VGluT1 and VGAT mRNAs in human dorsolateral prefrontal cortex during development and in schizophrenia

A balance between excitatory and inhibitory neurotransmission is important in normal brain function, and in schizophrenia a deficit in γ-aminobutyric acid (GABA)ergic inhibitory neurotransmission has been indicated by postmortem studies. We examined the ratio of excitatory to inhibitory vesicular neurotransmitter transporter mRNAs (VGluT1 to VGAT) and their ratio in the dorsolateral prefrontal cortex during normal human development and in people with schizophrenia and controls by quantitative RT-PCR. The ratio of VGluT1/VGAT increased gradually in development to reach a peak at school age (5-12 years), after which levels remained fairly constant into adulthood. The VGluT1 mRNA/VGAT mRNA ratio was unchanged in schizophrenia, as was the ratio of complexin 2 mRNA to complexin 1 mRNA (related to synaptic vesicle fusion in excitatory and inhibitory terminals, respectively). This suggests that the excitatory/inhibitory balance is attained prior to adolescence and is maintained across the rest of the life-span and also indicates that in schizophrenia this balance is not greatly disturbed.

Lack of change in markers of presynaptic terminal abundance alongside subtle reductions in markers of presynaptic terminal plasticity in prefrontal cortex of schizophrenia patients

BACKGROUND

Reduced synaptic connectivity in frontal cortex may contribute to schizophrenia symptoms. While altered messenger RNA (mRNA) and protein expression of various synaptic genes have been found, discrepancies between studies mean a generalizable synaptic pathology has not been identified.

METHODS

We determined if mRNAs encoding presynaptic proteins enriched in inhibitory (vesicular gamma-aminobutyric acid transporter [VGAT] and complexin 1) and/or excitatory (vesicular glutamate transporter 1 [VGluT1] and complexin 2) terminals are altered in the dorsolateral prefrontal cortex of subjects with schizophrenia (n = 37 patients, n = 37 control subjects). We also measured mRNA expression of markers associated with synaptic plasticity/neurite outgrowth (growth associated protein 43 [GAP43] and neuronal navigators [NAVs] 1 and 2) and mRNAs of other synaptic-associated proteins previously implicated in schizophrenia: dysbindin and vesicle-associated membrane protein 1 (VAMP1) mRNAs using quantitative polymerase chain reaction.

RESULTS

No significant changes in complexin 1, VGAT, complexin 2, VGluT1, dysbindin, NAV2, or VAMP1 mRNA expression were found; however, expression of mRNAs associated with plasticity/cytoskeletal modification (GAP43 and NAV1) was reduced in schizophrenia. Although dysbindin mRNA did not differ in schizophrenia compared with control subjects, dysbindin mRNA positively correlated with GAP43 and NAV1 in schizophrenia but not in control subjects, suggesting low levels of dysbindin may be linked to reduced plasticity in the disease state. No relationships between three dysbindin genetic polymorphisms previously associated with dysbindin mRNA levels were found.

CONCLUSIONS

A reduction in the plasticity of synaptic terminals supports the hypothesis that their reduced modifiability may contribute to neuropathology and working memory deficits in schizophrenia.