Blocking Src-PSD-95 interaction rescues glutamatergic signaling dysregulation in schizophrenia

The complex and heterogeneous genetic architecture of schizophrenia inspires us to look beyond individual risk genes for therapeutic strategies and target their interactive dynamics and convergence. Postsynaptic NMDA receptor (NMDAR) complexes are a site of such convergence. Src kinase is a molecular hub of NMDAR function, and its protein interaction subnetwork is enriched for risk-genes and altered protein associations in schizophrenia. Previously, Src activity was found to be decreased in post-mortem studies of schizophrenia, contributing to NMDAR hypofunction. PSD-95 suppresses Src via interacting with its SH2 domain. Here, we devised a strategy to suppress the inhibition of Src by PSD-95 via employing a cell penetrating and Src activating PSD-95 inhibitory peptide (TAT-SAPIP). TAT-SAPIP selectively increased post-synaptic Src activity in humans and mice, and enhanced synaptic NMDAR currents in mice. Chronic ICV injection of TAT-SAPIP rescued deficits in trace fear conditioning in Src hypomorphic mice. We propose blockade of the Src-PSD-95 interaction as a proof of concept for the use of interfering peptides as a therapeutic strategy to reverse NMDAR hypofunction in schizophrenia and other illnesses.

Chromatin domain alterations linked to 3D genome organization in a large cohort of schizophrenia and bipolar disorder brains

Chromosomal organization, scaling from the 147 base pair nucleosome to megabase-ranging domains encompassing multiple transcriptional units including heritability loci for psychiatric traits, remains largely unexplored in the human brain. Here, we construct promoter and enhancer enriched nucleosomal histone modification landscapes for adult prefrontal cortex (PFC) from H3-lysine 27 acetylation and H3-lysine 4 trimethylation profiles, generated from (n=739) 388 controls and 351 subjects diagnosed with schizophrenia (SCZ) or bipolar disorder (BD). We mapped thousands of cis-regulatory domains (CRDs), revealing fine-grained, 10⁴-10⁶ bp chromosomal organization, firmly integrated into Hi-C topologically associating domain (TAD) stratification by open/repressive chromosomal environments and nuclear topography. Large clusters of hyperacetylated CRDs were enriched for SCZ heritability, with prominent representation of regulatory sequences governing fetal development and glutamatergic neuron signaling. Therefore, SCZ and BD brains show coordinated dysregulation of risk-associated regulatory sequences assembled into kilo- to megabase-scaling chromosomal domains.

Maintenance of Wellness in Patients With Obsessive-Compulsive Disorder Who Discontinue Medication After Exposure/Response Prevention Augmentation: A Randomized Clinical Trial

IMPORTANCE

Serotonin reuptake inhibitors (SRIs) are the only medications approved for obsessive-compulsive disorder (OCD), yet most patients taking SRIs exhibit significant symptoms. Adding exposure/response prevention (EX/RP) therapy improves symptoms, but it is unknown whether patients maintain wellness after discontinuing SRIs.

OBJECTIVE

To assess whether patients with OCD who are taking SRIs and have attained wellness after EX/RP augmentation can discontinue their SRI with noninferior outcomes compared with those who continue their SRI therapy.

DESIGN, SETTING, AND PARTICIPANTS

A 24-week, double-blind, randomized clinical trial was performed from May 3, 2013, to June 25, 2018. The trial took place at US academic medical centers. Participants included 137 adults with a principal diagnosis of OCD (≥1 year) who were taking an SRI (≥12 weeks), had at least moderate symptoms (defined as Yale-Brown Obsessive-Compulsive Scale [Y-BOCS] score ≥18 points), and received as many as 25 sessions of EX/RP therapy. Those who attained wellness (Y-BOCS score ≤14 points; 103 patients [75.2%]) were study eligible. Data were analyzed from June 29, 2019, to October 2, 2021.

INTERVENTION

Participants were randomly assigned either to receive taper to placebo (taper group) or to continue their SRI (continuation group) and monitored for 24 weeks.

MAIN OUTCOME AND MEASURES

The Y-BOCS score (range, 0-40 points) was the primary outcome; the Hamilton Depression Rating Scale (HDRS; range, 0-52 points) and the Quality-of-Life Enjoyment and Satisfaction Questionnaire-Short Form (Q-LES-Q-SF; range, 0%-100%) scores were secondary outcomes. Outcomes were assessed at 8 time points by independent evaluators who were blinded to randomization. The taper regimen was hypothesized to be noninferior to continuation at 24 weeks using a 1-sided α value of .05.

RESULTS

A total of 101 patients (mean [SD] age, 31.0 [11.2] years; 55 women [54.5%]) participated in the trial: 51 patients (50.5%) in the taper group and 50 patients (49.5%) in the continuation group. At 24 weeks, patients in the taper group had noninferior results compared with patients in the continuation group (mean [SD] Y-BOCS score: taper group, 11.47 [6.56] points; continuation group: 11.51 [5.97] points; difference, -0.04 points; 1-sided 95% CI, -∞ to 2.09 points [below the noninferiority margin of 3.0 points]; mean [SD] HDRS score: taper group, 5.69 [3.84] points; continuation group, 4.61 [3.46] points; difference, 1.08 points; 1-sided 95% CI, -∞ to 2.28 points [below the noninferiority margin of 2.5 points]; mean [SD] Q-LES-Q-SF score: taper group, 68.01% [15.28%]; continuation group, 70.01% [15.59%]; difference, 2.00%; 1-sided 95% CI, -∞ to 6.83 [below the noninferiority margin of 7.75]). However, the taper group had higher rates of clinical worsening (23 of 51 [45%] vs 12 of 50 [24%]; P = .04).

CONCLUSIONS AND RELEVANCE

Results of this randomized clinical trial show that patients with OCD who achieve wellness after EX/RP therapy could, on average, discontinue their SRI with noninferior outcomes compared with those who continued their SRI. Those who tapered the SRI had higher clinical worsening rates. Future research should evaluate if SRI half-life alters these rates.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01686087.

Transcriptional profile of pyramidal neurons in chronic schizophrenia reveals lamina-specific dysfunction of neuronal immunity

While the pathophysiology of schizophrenia has been extensively investigated using homogenized postmortem brain samples, few studies have examined changes in brain samples with techniques that may attribute perturbations to specific cell types. To fill this gap, we performed microarray assays on mRNA isolated from anterior cingulate cortex (ACC) superficial and deep pyramidal neurons from 12 schizophrenia and 12 control subjects using laser-capture microdissection. Among all the annotated genes, we identified 134 significantly increased and 130 decreased genes in superficial pyramidal neurons, while 93 significantly increased and 101 decreased genes were found in deep pyramidal neurons, in schizophrenia compared to control subjects. In these differentially expressed genes, we detected lamina-specific changes of 55 and 31 genes in superficial and deep neurons in schizophrenia, respectively. Gene set enrichment analysis (GSEA) was applied to the entire pre-ranked differential expression gene lists to gain a complete pathway analysis throughout all annotated genes. Our analysis revealed overrepresented groups of gene sets in schizophrenia, particularly in immunity and synapse-related pathways, suggesting the disruption of these pathways plays an important role in schizophrenia. We also detected other pathways previously demonstrated in schizophrenia pathophysiology, including cytokine and chemotaxis, postsynaptic signaling, and glutamatergic synapses. In addition, we observed several novel pathways, including ubiquitin-independent protein catabolic process. Considering the effects of antipsychotic treatment on gene expression, we applied a novel bioinformatics approach to compare our differential expression gene profiles with 51 antipsychotic treatment datasets, demonstrating that our results were not influenced by antipsychotic treatment. Taken together, we found pyramidal neuron-specific changes in neuronal immunity, synaptic dysfunction, and olfactory dysregulation in schizophrenia, providing new insights for the cell-subtype specific pathophysiology of chronic schizophrenia.

Neuronal Nsun2 deficiency produces tRNA epitranscriptomic alterations and proteomic shifts impacting synaptic signaling and behavior

Epitranscriptomic mechanisms linking tRNA function and the brain proteome to cognition and complex behaviors are not well described. Here, we report bi-directional changes in depression-related behaviors after genetic disruption of neuronal tRNA cytosine methylation, including conditional ablation and transgene-derived overexpression of Nsun2 in the mouse prefrontal cortex (PFC). Neuronal Nsun2-deficiency was associated with a decrease in tRNA m5C levels, resulting in deficits in expression of 70% of tRNAGly isodecoders. Altogether, 1488/5820 proteins changed upon neuronal Nsun2-deficiency, in conjunction with glycine codon-specific defects in translational efficiencies. Loss of Gly-rich proteins critical for glutamatergic neurotransmission was associated with impaired synaptic signaling at PFC pyramidal neurons and defective contextual fear memory. Changes in the neuronal translatome were also associated with a 146% increase in glycine biosynthesis. These findings highlight the methylation sensitivity of glycinergic tRNAs in the adult PFC. Furthermore, they link synaptic plasticity and complex behaviors to epitranscriptomic modifications of cognate tRNAs and the proteomic homeostasis associated with specific amino acids.

Maximizing remission from cognitive-behavioral therapy in medicated adults with obsessive-compulsive disorder

Practice guidelines for adults with obsessive-compulsive disorder (OCD) recommend augmenting serotonin reuptake inhibitors (SRIs) with exposure and ritual prevention (EX/RP). However, fewer than half of patients remit after a standard 17-session EX/RP course. We studied whether extending the course increased overall remission rates and which patient factors predicted remission. Participants were 137 adults with clinically significant OCD (Yale-Brown Obsessive Compulsive Scale [Y-BOCS] score ≥18) despite an adequate SRI trial (≥12 weeks). Continuing their SRI, patients received 17 sessions of twice-weekly EX/RP (standard course). Patients who did not remit (Y-BOCS ≤12) received up to 8 additional sessions (extended course). Of 137 entrants, 123 completed treatment: 49 (35.8%) remitted with the standard course and another 46 (33.6%) with the extended course. Poorer patient homework adherence, more Obsessive-Compulsive Personality Disorder (OCPD) traits, and the Brain-Derived Neurotrophic Factor (BDNF) Val66MET genotype were associated with lower odds of standard course remission. Only homework adherence differentiated non-remitters from extended course remitters. Extending the EX/RP course from 17 to 25 sessions enabled many (69.3%) OCD patients on SRIs to achieve remission. Although behavioral (patient homework adherence), psychological (OCPD traits), and biological (BDNF genotype) factors influenced odds of EX/RP remission, homework adherence was the most potent patient factor overall.

mGluR5 hypofunction is integral to glutamatergic dysregulation in schizophrenia

Multiple lines of evidence point to glutamatergic signaling in the postsynaptic density (PSD) as a pathophysiologic mechanism in schizophrenia. Integral to PSD glutamatergic signaling is reciprocal interplay between GluN and mGluR5 signaling. We examined agonist-induced mGluR5 signaling in the postmortem dorsolateral prefrontal cortex (DLPFC) derived from 17 patients and age-matched and sex-matched controls. The patient group showed a striking reduction in mGluR5 signaling, manifested by decreases in Gq/11 coupling and association with PI3K and Homer compared to controls (p < 0.01 for all). This was accompanied by increases in serine and tyrosine phosphorylation of mGluR5, which can decrease mGluR5 activity via desensitization (p < 0.01). In addition, we find altered protein-protein interaction (PPI) of mGluR5 with RGS4, norbin, Preso 1 and tamalin, which can also attenuate mGluR5 activity. We previously reported molecular underpinnings of GluN hypofunction (decreased GluN2 phosphorylation) and here we show those of reduced mGluR5 signaling in schizophrenia. We find that reduced GluN2 phosphorylation can be precipitated by attenuated mGluR5 activity and that increased mGluR5 phosphorylation can result from decreased GluN function, suggesting a reciprocal interplay between the two pathways in schizophrenia. Interestingly, the patient group showed decreased mGluR5-GluN association (p < 0.01), a mechanistic basis for the reciprocal facilitation. In sum, we present the first direct evidence for mGluR5 hypoactivity, propose a reciprocal interplay between GluN and mGluR5 pathways as integral to glutamatergic dysregulation and suggest protein-protein interactions in mGluR5-GluN complexes as potential targets for intervention in schizophrenia.

Transcriptional corepressor SIN3A regulates hippocampal synaptic plasticity via Homer1/mGluR5 signaling

Long-term memory depends on the control of activity-dependent neuronal gene expression, which is regulated by epigenetic modifications. The epigenetic modification of histones is orchestrated by the opposing activities of 2 classes of regulatory complexes: permissive coactivators and silencing corepressors. Much work has focused on coactivator complexes, but little is known about the corepressor complexes that suppress the expression of plasticity-related genes. Here, we define a critical role for the corepressor SIN3A in memory and synaptic plasticity, showing that postnatal neuronal deletion of Sin3a enhances hippocampal long-term potentiation and long-term contextual fear memory. SIN3A regulates the expression of genes encoding proteins in the postsynaptic density. Loss of SIN3A increases expression of the synaptic scaffold Homer1, alters the metabotropic glutamate receptor 1α (mGluR1α) and mGluR5 dependence of long-term potentiation, and increases activation of ERK in the hippocampus after learning. Our studies define a critical role for corepressors in modulating neural plasticity and memory consolidation and reveal that Homer1/mGluR signaling pathways may be central molecular mechanisms for memory enhancement.

The proteome and its dynamics: A missing piece for integrative multi-omics in schizophrenia

The complex and heterogeneous pathophysiology of schizophrenia can be deconstructed by integration of large-scale datasets encompassing genes through behavioral phenotypes. Genome-wide datasets are now available for genetic, epigenetic and transcriptomic variations in schizophrenia, which are then analyzed by newly devised systems biology algorithms. A missing piece, however, is the inclusion of information on the proteome and its dynamics in schizophrenia. Proteomics has lagged behind omics of the genome, transcriptome and epigenome since analytic platforms were relatively less robust for proteins. There has been remarkable progress, however, in the instrumentation of liquid chromatography (LC) and mass spectrometry (MS) (LCMS), experimental paradigms and bioinformatics of the proteome. Here, we present a summary of methodological innovations of recent years in MS based proteomics and the power of new generation proteomics, review proteomics studies that have been conducted in schizophrenia to date, and propose how such data can be analyzed and integrated with other omics results. The function of a protein is determined by multiple molecular properties, i.e., subcellular localization, posttranslational modification (PTMs) and protein-protein interactions (PPIs). Incorporation of these properties poses additional challenges in proteomics and their integration with other omics; yet is a critical next step to close the loop of multi-omics integration. In sum, the recent advent of high-throughput proteome characterization technologies and novel mathematical approaches enable us to incorporate functional properties of the proteome to offer a comprehensive multi-omics based understanding of schizophrenia pathophysiology.

Src deficient mice demonstrate behavioral and electrophysiological alterations relevant to psychiatric and developmental disease

Much evidence suggests that hypofunction of the N-methyl-d-aspartate glutamate receptor (NMDAR) may contribute broadly towards a subset of molecular, cognitive and behavioral abnormalities common among psychiatric and developmental diseases. However, little is known about the specific molecular changes that lead to NMDAR dysfunction. As such, personalized approaches to remediating NMDAR dysfunction based on a specific etiology remains a challenge. Sarcoma tyrosine kinase (Src) serves as a hub for multiple signaling mechanisms affecting GluN2 phosphorylation and can be disrupted by convergent alterations of various signaling pathways. We recently showed reduced Src signaling in post mortem tissue from schizophrenia patients, despite increased MK-801 binding and NMDA receptor complex expression in the postsynaptic density (PSD). These data suggest that Src dysregulation may be an important underlying mechanism responsible for reduced glutamate signaling. Despite this evidence for a central role of Src in NMDAR signaling, little is known about how reductions in Src activity might regulate phenotypic changes in cognition and behavior. As such, the current study sought to characterize behavioral and electrophysiological phenotypes in mice heterozygous for the Src Acl gene (Src+/- mice). Src+/- mice demonstrated decreased sociability and working memory relative to Src+/+ (WT) mice while no significant differences were seen on locomotive activity and anxiety-related behavior. In relation to WT mice, Src+/- mice showed decreased mid-latency P20 auditory event related potential (aERP) amplitudes, decreased mismatch negativity (MMN) and decreased evoked gamma power, which was only present in males. These data indicate that Src+/- mice are a promising new model to help understand the pathophysiology of these electrophysiological, behavioral and cognitive changes. As such, we propose that Src+/- mice can be used in the future to evaluate potential therapeutic approaches by targeting increased Src activity as a common final pathway for multiple etiologies of SCZ and other diseases characterized by reduced glutamate function.

Neuron-specific signatures in the chromosomal connectome associated with schizophrenia risk

To explore the developmental reorganization of the three-dimensional genome of the brain in the context of neuropsychiatric disease, we monitored chromosomal conformations in differentiating neural progenitor cells. Neuronal and glial differentiation was associated with widespread developmental remodeling of the chromosomal contact map and included interactions anchored in common variant sequences that confer heritable risk for schizophrenia. We describe cell type-specific chromosomal connectomes composed of schizophrenia risk variants and their distal targets, which altogether show enrichment for genes that regulate neuronal connectivity and chromatin remodeling, and evidence for coordinated transcriptional regulation and proteomic interaction of the participating genes. Developmentally regulated chromosomal conformation changes at schizophrenia-relevant sequences disproportionally occurred in neurons, highlighting the existence of cell type-specific disease risk vulnerabilities in spatial genome organization.

Non-coding RNA dysregulation in the amygdala region of schizophrenia patients contributes to the pathogenesis of the disease

Schizophrenia (SCZ) is a neuropsychiatric disorder with a complex genetic etiology. The redundancy of the gene networks underlying SCZ indicates that many gene combinations have the potential to cause a system dysfunction that can manifest as SCZ or a related neurodevelopmental disorder. Recent studies show that small non-coding microRNA (miRNA) and long non-coding RNA (lncRNA) are important factors in shaping these networks and are dynamically regulated by neuronal activation. We investigated the genome-wide transcription profiles of 46 human amygdala samples obtained from 22 SCZ patients and 24 healthy controls. Using RNA sequencing (RNA-seq), we determined lncRNA expression levels in all samples and generated miRNA profiles for 27 individuals (13 cases and 14 controls). Previous studies have identified differentially expressed miRNAs in SCZ, including miR-132, miR-212, and miR-34a/miR-34c. Here we report differential expression of a novel miRNA, miR1307, in SCZ. Notably, miR1307 maps to a locus previously associated with SCZ through GWAS. Additionally, one lncRNA that was overexpressed in SCZ, AC005009.2, also maps to a region previously associated with SCZ based on GWAS and overlapped SCZ-related genes. The results were replicated in a large independent data set of 254 dorsolateral prefrontal cortex samples from the CommonMind consortium. Taken together, these results suggest that miRNA and lncRNAs are important contributors to the pathogenesis of SCZ.

Large-Scale Identification of Common Trait and Disease Variants Affecting Gene Expression

Genome-wide association studies (GWASs) have identified a multitude of genetic loci involved with traits and diseases. However, it is often unclear which genes are affected in such loci and whether the associated genetic variants lead to increased or decreased gene function. To mitigate this, we integrated associations of common genetic variants in 57 GWASs with 24 studies of expression quantitative trait loci (eQTLs) from a broad range of tissues by using a Mendelian randomization approach. We discovered a total of 3,484 instances of gene-trait-associated changes in expression at a false-discovery rate < 0.05. These genes were often not closest to the genetic variant and were primarily identified in eQTLs derived from pathophysiologically relevant tissues. For instance, genes with expression changes associated with lipid traits were mostly identified in the liver, and those associated with cardiovascular disease were identified in arterial tissue. The affected genes additionally point to biological processes implicated in the interrogated traits, such as the interleukin-27 pathway in rheumatoid arthritis. Further, comparing trait-associated gene expression changes across traits suggests that pleiotropy is a widespread phenomenon and points to specific instances of both agonistic and antagonistic pleiotropy. For instance, expression of SNX19 and ABCB9 is positively correlated with both the risk of schizophrenia and educational attainment. To facilitate interpretation, we provide this lexicon of how common trait-associated genetic variants alter gene expression in various tissues as the online database GWAS2Genes.

Sociability Deficits and Altered Amygdala Circuits in Mice Lacking Pcdh10, an Autism Associated Gene

BACKGROUND

Behavioral symptoms in individuals with autism spectrum disorder (ASD) have been attributed to abnormal neuronal connectivity, but the molecular bases of these behavioral and brain phenotypes are largely unknown. Human genetic studies have implicated PCDH10, a member of the δ2 subfamily of nonclustered protocadherin genes, in ASD. PCDH10 expression is enriched in the basolateral amygdala, a brain region implicated in the social deficits of ASD. Previous reports indicate that Pcdh10 plays a role in axon outgrowth and glutamatergic synapse elimination, but its roles in social behaviors and amygdala neuronal connectivity are unknown. We hypothesized that haploinsufficiency of Pcdh10 would reduce social approach behavior and alter the structure and function of amygdala circuits.

METHODS

Mice lacking one copy of Pcdh10 (Pcdh10^+/-) and wild-type littermates were assessed for social approach and other behaviors. The lateral/basolateral amygdala was assessed for dendritic spine number and morphology, and amygdala circuit function was studied using voltage-sensitive dye imaging. Expression of Pcdh10 and N-methyl-D-aspartate receptor (NMDAR) subunits was assessed in postsynaptic density fractions of the amygdala.

RESULTS

Male Pcdh10^+/- mice have reduced social approach behavior, as well as impaired gamma synchronization, abnormal spine morphology, and reduced levels of NMDAR subunits in the amygdala. Social approach deficits in Pcdh10^+/- male mice were rescued with acute treatment with the NMDAR partial agonist d-cycloserine.

CONCLUSIONS

Our studies reveal that male Pcdh10^+/- mice have synaptic and behavioral deficits, and establish Pcdh10^+/- mice as a novel genetic model for investigating neural circuitry and behavioral changes relevant to ASD.

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.

Effects of sex and DTNBP1 (dysbindin) null gene mutation on the developmental GluN2B-GluN2A switch in the mouse cortex and hippocampus

BACKGROUND

Neurodevelopmental disorders such as autism spectrum disorders and schizophrenia differentially impact males and females and are highly heritable. The ways in which sex and genetic vulnerability influence the pathogenesis of these disorders are not clearly understood. The n-methyl-d-aspartate (NMDA) receptor pathway has been implicated in schizophrenia and autism spectrum disorders and changes dramatically across postnatal development at the level of the GluN2B-GluN2A subunit "switch" (a shift from reliance on GluN2B-containing receptors to reliance on GluN2A-containing receptors). We investigated whether sex and genetic vulnerability (specifically, null mutation of DTNBP1 [dysbindin; a possible susceptibility gene for schizophrenia]) influence the developmental GluN2B-GluN2A switch.

METHODS

Subcellular fractionation to enrich for postsynaptic density (PSD), together with Western blotting and kinase assay, were used to investigate the GluN2B-GluN2A switch in the cortex and hippocampus of male and female DTNBP1 null mutant mice and their wild-type littermates. Main effects of sex and DTNBP1 genotype, and interactions with age, were assessed using factorial ANOVA.

RESULTS

Sex differences in the GluN2B-GluN2A switch emerged across development at the frontal cortical synapse, in parameters related to GluN2B. Males across genotypes displayed higher GluN2B:GluN2A and GluN2B:GluN1 ratios (p < 0.05 and p < 0.01, respectively), higher GluN2B phosphorylation at Y1472 (p < 0.01), and greater abundance of PLCγ (p < 0.01) and Fyn (p = 0.055) relative to females. In contrast, effects of DTNBP1 were evident exclusively in the hippocampus. The developmental trajectory of GluN2B was disrupted in DTNBP1 null mice (genotype × age interaction p < 0.05), which also displayed an increased synaptic GluN2A:GluN1 ratio (p < 0.05) and decreased PLCγ (p < 0.05) and Fyn (only in females; p < 0.0005) compared to wild-types.

CONCLUSIONS

Sex and DTNBP1 mutation influence the GluN2B-GluN2A switch at the synapse in a brain-region-specific fashion involving pY1472-GluN2B, Fyn, and PLCγ. This highlights the possible mechanisms through which risk factors may mediate their effects on vulnerability to disorders of NMDA receptor dysfunction.

Altered G Protein Coupling in Olfactory Neuroepithelial Cells From Patients With Schizophrenia

Increasing evidence suggests that olfactory dysfunction is an endophenotype of schizophrenia, and thus the olfactory system can be studied both in relation to this sensory dysfunction and also as a means of examining pathophysiologic mechanisms of schizophrenia. In this study, we examined human olfactory neuroepithelial (ON) biopsy tissues and their in vitro culture cells for ligand-induced guanine nucleotide-binding protein (G protein) activation and downstream signaling. We assessed the binding of a nonhydrolyzable GTP analogue [(35)S]GTPγS binding to specific G protein subtypes in response to odorants, dopamine, or serotonin in ON cell membranes from matched schizophrenia-control subjects. In response to odorant mixtures, we found decreased [(35)S]GTPγS binding to Gαs/olf in schizophrenia patients. These changes were not mediated by mRNA expression of key molecules of G protein coupling, including adenylate cyclase III (ACIII), protein kinase A (PKA), protein kinase Cγ (PKCγ), or Gαs or Gαolf in ON cells or ON biopsy tissues. In contrast, dopamine (DA)- and serotonin (5HT)-induced S(35)-GTPγS binding to Gαs/olf and Gαq/11 were significantly increased in schizophrenia cases, while these parameters were strikingly reduced by in vitro treatment with antipsychotics. Patients with schizophrenia exhibit increases in electrolfactogram (EOG) recordings, suggesting enhanced odorant-induced activation. Our results of decreased odorant-induced G protein activation may point further downstream for underlying mechanisms for increased EOG measures. Increased G protein activation in response to DA and 5HT may suggest increased postreceptor DA or 5HT signaling as an additional mechanism of dopaminergic or serotonergic dysregulation in schizophrenia.

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.

Delayed emergence of behavioral and electrophysiological effects following juvenile ketamine exposure in mice

Frequent ketamine abuse in adulthood correlates with increased risk of psychosis, as well as cognitive deficits, including disruption of higher-order executive function and memory formation. Although the primary abusers of ketamine are adolescents and young adults, few studies have evaluated its effects on juvenile cognition. Therefore, the current study analyzes the effect of adolescent ketamine exposure on cognitive development. Juvenile mice (4 weeks of age) were exposed to chronic ketamine (20 mg kg(-1), i.p. daily) for 14 days. Mice were tested immediately after exposure in the juvenile period (7 weeks of age) and again as adults (12 weeks of age). Measures included electroencephalography (EEG) in response to auditory stimulation, the social choice test, and a 6-arm radial water maze task. Outcome measures include low-frequency EEG responses, event-related potential (ERP) amplitudes, indices of social behavior and indices of spatial working memory. Juvenile exposure to ketamine was associated with electrophysiological abnormalities in adulthood, particularly in induced theta power and the P80 ERP. The social choice test revealed that ketamine-exposed mice failed to exhibit the same age-related decrease in social interaction time as controls. Ketamine-exposed mice outperformed control mice as juveniles on the radial water maze task, but did not show the same age-related improvement as adult controls. These data support the hypothesis that juvenile exposure to ketamine produces long-lasting changes in brain function that are characterized by a failure to progress along normal developmental trajectories.

Src kinase as a mediator of convergent molecular abnormalities leading to NMDAR hypoactivity in schizophrenia

Numerous investigations support decreased glutamatergic signaling as a pathogenic mechanism of schizophrenia, yet the molecular underpinnings for such dysregulation are largely unknown. In the post-mortem dorsolateral prefrontal cortex (DLPFC), we found striking decreases in tyrosine phosphorylation of N-methyl-D aspartate (NMDA) receptor subunit 2 (GluN2) that is critical for neuroplasticity. The decreased GluN2 activity in schizophrenia may not be because of downregulation of NMDA receptors as MK-801 binding and NMDA receptor complexes in postsynaptic density (PSD) were in fact increased in schizophrenia cases. At the postreceptor level, however, we found striking reductions in the protein kinase C, Pyk 2 and Src kinase activity that in tandem can decrease GluN2 activation. Given that Src serves as a hub of various signaling mechanisms affecting GluN2 phosphorylation, we postulated that Src hypoactivity may result from convergent alterations of various schizophrenia susceptibility pathways and thus mediate their effects on NMDA receptor signaling. Indeed, the DLPFC of schizophrenia cases exhibit increased PSD-95 and erbB4 and decreased receptor-type tyrosine-protein phosphatase-α (RPTPα) and dysbindin-1, each of which reduces Src activity via protein interaction with Src. To test genomic underpinnings for Src hypoactivity, we examined genome-wide association study results, incorporating 13 394 cases and 34 676 controls. We found no significant association of individual variants of Src and its direct regulators with schizophrenia. However, a protein-protein interaction-based network centered on Src showed significant enrichment of gene-level associations with schizophrenia compared with other psychiatric illnesses. Our results together demonstrate striking decreases in NMDA receptor signaling at the postreceptor level and propose Src as a nodal point of convergent dysregulations affecting NMDA receptor pathway via protein-protein associations.

Six-month outcomes from a randomized trial augmenting serotonin reuptake inhibitors with exposure and response prevention or risperidone in adults with obsessive-compulsive disorder

OBJECTIVE

To compare outcomes after 6-month maintenance treatment of adults diagnosed with obsessive-compulsive disorder (OCD) based on DSM-IV criteria who responded to acute treatment with serotonin reuptake inhibitors (SRIs) augmented by exposure and response prevention (EX/RP) or risperidone.

METHOD

A randomized trial was conducted at 2 academic sites from January 2007 through December 2012. In the acute phase, 100 patients on therapeutic SRI dose with at least moderate OCD severity were randomized to 8 weeks of EX/RP, risperidone, or pill placebo. Responders entered the 6-month maintenance phase, continuing the augmentation strategy they received acutely (n = 30 EX/RP, n = 8 risperidone). Independent evaluations were conducted every month. The main outcome was the Yale-Brown Obsessive Compulsive Scale (Y-BOCS).

RESULTS

Intent-to-treat analyses indicated that, after 6-month maintenance treatment, EX/RP yielded OCD outcomes that were superior to risperidone (Y-BOCS = 10.95 vs 18.70; t40 = 2.76, P = .009); more patients randomized to EX/RP met response criteria (Y-BOCS decrease ≥ 25%: 70% vs 20%; P < .001) and achieved minimal symptoms (Y-BOCS ≤ 12: 50% vs 5%; P < .001). During maintenance, OCD severity decreased slightly in both conditions (Y-BOCS decrease = 2.2 points, P = .020). Lower Y-BOCS at entry to maintenance was associated with more improvement in both conditions (r38 = 0.57, P < .001).

CONCLUSIONS

OCD patients taking SRIs who responded to acute EX/RP or risperidone maintained their gains over 6-month maintenance. Because EX/RP patients improved more during acute treatment than risperidone-treated patients, and both maintained their gains during maintenance, EX/RP yielded superior outcomes 6 months later. The findings that 50% of patients randomized to EX/RP had minimal symptoms at 6-month maintenance, a rate double that of prior studies, suggests that EX/RP maintenance helps maximize long-term outcome.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00389493.

Increased stability of microtubules in cultured olfactory neuroepithelial cells from individuals with schizophrenia

Microtubules (MTs) are essential components of the cytoskeleton that play critical roles in neurodevelopment and adaptive central nervous system functioning. MTs are essential to growth cone advance and ultrastructural events integral to synaptic plasticity; these functions figure significantly into current pathophysiologic conceptualizations of schizophrenia. To date, no study has directly investigated MT dynamics in humans with schizophrenia. We therefore compared the stability of MTs in olfactory neuroepithelial (OE) cells between schizophrenia cases and matched nonpsychiatric comparison subjects. For this purpose, we applied nocodazole (Nz) to cultured OE cells obtained from tissue biopsies from seven living schizophrenia patients and seven matched comparison subjects; all schizophrenia cases were on antipsychotic medications. Nz allows MT depolymerization to be followed but prevents repolymerization, so that in living cells treated for varying time intervals, the MTs that are stable for a given treatment interval remain. Our readout of MT stability was the time at which fewer than 10 MTs per cell could be distinguished by anti-β-tubulin immunofluorescence. The percentage of cells with ≥10 intact MTs at specified intervals following Nz treatment was estimated by systematic uniform random sampling with Visiopharm software. These analyses showed that the mean percentages of OE cells with intact MTs were significantly greater for schizophrenia cases than for the matched comparison subjects at 10, 15, and 30min following Nz treatment indicating increased MT stability in OE cells from schizophrenia patients (p=0.0007 at 10min; p=0.0008 at 15min; p=0.036 at 30min). In conclusion, we have demonstrated increased MT stability in nearly all cultures of OE cells from individuals with schizophrenia, who received several antipsychotic treatments, versus comparison subjects matched for age and sex. While we cannot rule out a possible confounding effect of antipsychotic medications, these findings may reflect analogous neurobiological events in at least a subset of immature neurons or other cell types during gestation, or newly generated cells destined for the olfactory bulb or hippocampus, suggesting a mechanism that underlies findings of postmortem and neuroimaging investigations of schizophrenia. Future studies aimed at replicating these findings, including samples of medication-naïve subjects with schizophrenia, and reconciling the results with other studies, will be necessary. Although the observed abnormalities may suggest one of a number of putative pathophysiologic anomalies in schizophrenia, this work may ultimately have implications for an improved understanding of pathogenic processes related to this disorder.

Meta-analysis of olfactory function in schizophrenia, first-degree family members, and youths at-risk for psychosis

BACKGROUND

Previous research has provided compelling support for olfactory dysfunction in schizophrenia patients, their first-degree relatives, and youth at-risk for psychosis. A previous meta-analysis revealed large effect sizes across olfactory tasks but was limited to 2 olfactory tasks and did not examine moderator variables. Thus, the current meta-analysis was undertaken to incorporate additional studies, risk cohorts, olfactory test domains, and moderator variable analyses.

METHOD

A meta-analysis was conducted on 67 publications examining olfactory function in schizophrenia patients and 15 publications examining olfactory functioning in youth at-risk for psychosis, first-degree relatives of schizophrenia patients, and individuals with schizotypy.

RESULTS

Results revealed medium-to-large olfactory deficits in schizophrenia patients though significant heterogeneity was evident. Several variables moderated overall study effects. At-risk youths similarly demonstrated medium-to-large effect sizes, whereas first-degree relatives and individuals with schizotypy showed small effects.

CONCLUSIONS

Findings suggest robust olfactory deficits in schizophrenia and at-risk youths. In schizophrenia, several variables had significant impact on these deficits and warrant consideration in prospective studies. Our findings also indicate that olfactory measures may be a useful marker of schizophrenia risk status.

Cognitive-behavioral therapy vs risperidone for augmenting serotonin reuptake inhibitors in obsessive-compulsive disorder: a randomized clinical trial

IMPORTANCE

Obsessive-compulsive disorder (OCD) is one of the world's most disabling illnesses according to the World Health Organization. Serotonin reuptake inhibitors (SRIs) are the only medications approved by the Food and Drug Administration to treat OCD, but few patients achieve minimal symptoms from an SRI alone. In such cases, practice guidelines recommend adding antipsychotics or cognitive-behavioral therapy consisting of exposure and ritual prevention (EX/RP).

OBJECTIVE

To compare the effects of these 2 SRI augmentation strategies vs pill placebo for the first time, to our knowledge, in adults with OCD.

DESIGN, SETTING, AND PARTICIPANTS

A randomized clinical trial (conducted January 2007-August 2012) at 2 academic outpatient research clinics that specialize in OCD and anxiety disorders. Patients (aged 18-70 years) were eligible if they had OCD of at least moderate severity despite a therapeutic SRI dose for at least 12 weeks prior to entry. Of 163 who were eligible, 100 were randomized (risperidone, n = 40; EX/RP, n = 40; and placebo, n = 20), and 86 completed the trial.

INTERVENTIONS

While continuing their SRI at the same dose, patients were randomized to the addition of 8 weeks of risperidone (up to 4 mg/d), EX/RP (17 sessions delivered twice weekly), or pill placebo. Independent assessments were conducted every 4 weeks.

MAIN OUTCOME AND MEASURE

The Yale-Brown Obsessive Compulsive Scale (Y-BOCS) to measure OCD severity.

RESULTS

Patients randomized to EX/RP had significantly greater reduction in week 8 Y-BOCS scores based on mixed-effects models (vs risperidone: mean [SE], -9.72 [1.38]; P < .001 vs placebo: mean [SE], -10.10 [1.68]; P < .001). Patients receiving risperidone did not significantly differ from those receiving placebo (mean [SE], -0.38 [1.72]; P = .83). More patients receiving EX/RP responded (Y-BOCS score decrease ≥25%: 80% for EX/RP, 23% for risperidone, and 15% for placebo; P < .001). More patients receiving EX/RP achieved minimal symptoms (Y-BOCS score ≤12: 43% for EX/RP, 13% for risperidone, and 5% for placebo; P = .001). Adding EX/RP was also superior to risperidone and placebo in improving insight, functioning, and quality of life.

CONCLUSIONS AND RELEVANCE

Adding EX/RP to SRIs was superior to both risperidone and pill placebo. Patients with OCD receiving SRIs who continue to have clinically significant symptoms should be offered EX/RP before antipsychotics given its superior efficacy and less negative adverse effect profile.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00389493.

Proteoglycan abnormalities in olfactory epithelium tissue from subjects diagnosed with schizophrenia

Emerging evidence points to proteoglycan abnormalities in the pathophysiology of schizophrenia (SZ). In particular, markedly abnormal expression of chondroitin sulfate proteoglycans (CSPGs), key components of the extracellular matrix, was observed in the medial temporal lobe. CSPG functions, including regulation of neuronal differentiation and migration, are highly relevant to the pathophysiology of SZ. CSPGs may exert similar functions in the olfactory epithelium (OE), a continuously regenerating neural tissue that shows cell and molecular abnormalities in SZ. We tested the hypothesis that CSPG expression in OE may be altered in SZ. CSPG-positive cells in postmortem OE from non-psychiatric control (n=9) and SZ (n=10) subjects were counted using computer-assisted light microscopy. 'Cytoplasmic' CSPG (c-CSPG) labeling was detected in sustentacular cells and some olfactory receptor neurons (c-CSPG+ORNs), while 'pericellular' CSPG (p-CSPG) labeling was found in basal cells and some ORNs (p-CSPG+ORNs). Dual labeling for CSPG and markers for mature and immature ORNs suggests that c-CSPG+ORNs correspond to mature ORNs, and p-CSPG+ORNs to immature ORNs. Previous studies in the same cohort demonstrated that densities of mature ORNs were unaltered (Arnold et al., 2001). In the present study, numerical densities of c-CSPG+ORNs were significantly decreased in SZ (p<0.025; 99.32% decrease), suggesting a reduction of CSPG expression in mature ORNs. Previous studies showed a striking increase in the ratios of immature neurons with respect to basal cells. In this study, we find that the ratio of p-CSPG+ORNs/CSPG+basal cells was significantly increased (p=0.03) in SZ, while numerical density changes of p-CSPG+ORNs (110.71% increase) or CSPG+basal cells (53.71% decrease), did not reach statistical significance. Together, these results indicate that CSPG abnormalities are present in the OE of SZ and specifically point to a reduction of CSPG expression in mature ORNs in SZ. Given the role CSPGs play in OE cell differentiation and axon guidance, we suggest that altered CSPG expression may contribute to ORN lineage dysregulation, and olfactory identification abnormalities, observed in SZ.

Six-month follow-up of a randomized controlled trial augmenting serotonin reuptake inhibitor treatment with exposure and ritual prevention for obsessive-compulsive disorder

OBJECTIVE

This article describes the long-term effects of augmenting serotonin reuptake inhibitors (SRIs) with exposure and ritual prevention or stress management training in patients with DSM-IV obsessive-compulsive disorder (OCD).

METHOD

Between November 2000 and November 2006, 111 OCD patients from 2 academic outpatient centers with partial SRI response were randomized to the addition of exposure and ritual prevention or stress management training, delivered twice weekly for 8 weeks (acute phase); 108 began treatment. Responders (38 of 52 in the exposure and ritual prevention condition, 11 of 52 in the stress management training condition) entered a 24-week maintenance phase. The Yale-Brown Obsessive Compulsive Scale (YBOCS) was the primary outcome measure.

RESULTS

After 24 weeks, patients randomized to and receiving exposure and ritual prevention versus stress management training had significantly better outcomes (mean YBOCS scores of 14.69 and 21.37, respectively; t = 2.88, P = .005), higher response rates (decrease in YBOCS scores ≥ 25%: 40.7% vs 9.3%, Fisher exact test P < .001), and higher rates of excellent response (YBOCS score ≤ 12: 24.1% vs 5.6%, Fisher exact test P = .01). During the maintenance phase, the slope of change in YBOCS scores was not significant in either condition (all P values ≥ .55), with no difference between exposure and ritual prevention and stress management training (P > .74). Better outcome was associated with baseline variables: lower YBOCS scores, higher quality of life, fewer comorbid Axis I diagnoses, and male sex.

CONCLUSIONS

Augmenting SRIs with exposure and ritual prevention versus stress management training leads to better outcome after acute treatment and 24 weeks later. Maintenance outcome, however, was primarily a function of OCD severity at entrance. Greater improvement during the acute phase influences how well patients maintain their gains, regardless of treatment condition.

Are we getting closer to valid translational models for major depression?

Advances in characterizing the neuropathology and functional dysconnectivity of depression and promising trials with emerging circuit-targeted and fast-onset therapeutics are providing unprecedented opportunities to gain deeper insight into the neurobiology of this devastating and pervasive disorder. Because of practical and ethical limitations to dissecting these mechanisms in humans, continued progress will critically depend on our ability to emulate aspects of depressive symptomatology and treatment response in nonhuman organisms. Although various experimental models are currently available, they often draw skepticism from both clinicians and basic research scientists. We review recent progress and highlight some of the best leads to diversify and improve discovery end points for preclinical depression research.

Biochemical fractionation and stable isotope dilution liquid chromatography-mass spectrometry for targeted and microdomain-specific protein quantification in human postmortem brain tissue

Synaptic architecture and its adaptive changes require numerous molecular events that are both highly ordered and complex. A majority of neuropsychiatric illnesses are complex trait disorders, in which multiple etiologic factors converge at the synapse via many signaling pathways. Investigating the protein composition of synaptic microdomains from human patient brain tissues will yield valuable insights into the interactions of risk genes in many disorders. These types of studies in postmortem tissues have been limited by the lack of proper study paradigms. Thus, it is necessary not only to develop strategies to quantify protein and post-translational modifications at the synapse, but also to rigorously validate them for use in postmortem human brain tissues. In this study we describe the development of a liquid chromatography-selected reaction monitoring method, using a stable isotope-labeled neuronal proteome standard prepared from the brain tissue of a stable isotope-labeled mouse, for the multiplexed quantification of target synaptic proteins in mammalian samples. Additionally, we report the use of this method to validate a biochemical approach for the preparation of synaptic microdomain enrichments from human postmortem prefrontal cortex. Our data demonstrate that a targeted mass spectrometry approach with a true neuronal proteome standard facilitates accurate and precise quantification of over 100 synaptic proteins in mammalian samples, with the potential to quantify over 1000 proteins. Using this method, we found that protein enrichments in subcellular fractions prepared from human postmortem brain tissue were strikingly similar to those prepared from fresh mouse brain tissue. These findings demonstrate that biochemical fractionation methods paired with targeted proteomic strategies can be used in human brain tissues, with important implications for the study of neuropsychiatric disease.

Neuropathology of the olfactory mucosa in chronic rhinosinusitis

BACKGROUND

Chronic rhinosinusitis (CRS) is a complex heterogeneous inflammatory disease that affects the nasal cavity, but the pathological examination of the olfactory mucosa (OM) in this disease has been limited.

METHODS

Nasal biopsy specimens were obtained from 20 control subjects and 50 CRS patients in conjunction with clinical assessments. Histopathology of these nasal biopsy specimens was performed and immunohistochemistry was used to characterize nonneuronal, neuronal, and inflammatory cells in the OM. These OM characteristics were then evaluated to determine the degree to which pathological features may be related to smell loss in CRS.

RESULTS

Histopathological examination of control and CRS OM revealed changes in the normal pseudostratified olfactory epithelium (OE): intermixing of goblet cells, metaplasia to squamous-like cells, and erosion of the OE. Lower percentages of normal epithelium and olfactory sensory neurons were found in CRS OE compared with controls. Relative to other CRS patients, those with anosmia had the greatest amount of OE erosion, the highest density of eosinophils infiltrating the OE, and exhibited the most extensive abnormalities on CT and endoscopic examination, including being significantly more likely to exhibit nasal polyposis.

CONCLUSION

Our results suggest that OM pathology observed in nasal biopsy specimens can assist in understanding the degree of epithelial change and sensorineural damage in CRS and the potential for olfactory loss.

Scents and nonsense: olfactory dysfunction in schizophrenia

Among the sensory modalities, olfaction is most closely associated with the frontal and temporal brain regions that are implicated in schizophrenia and most intimately related to the affective and mnemonic functions that these regions subserve. Olfactory probes may therefore be ideal tools through which to assess the structural and functional integrity of the neural substrates that underlie disease-related cognitive and emotional disturbances. Perhaps more importantly, to the extent that early sensory afferents are also disrupted in schizophrenia, the olfactory system-owing to its strategic anatomic location-may be especially vulnerable to such disruption. Olfactory dysfunction may therefore be a sensitive indicator of schizophrenia pathology and may even serve as an "early warning" sign of disease vulnerability or onset. In this article, we review the evidence supporting a primary olfactory sensory disturbance in schizophrenia. Convergent data indicate that structural and functional abnormalities extend from the cortex to the most peripheral elements of the olfactory system. These reflect, in part, a genetically mediated neurodevelopmental etiology. Gross structural and functional anomalies are mirrored by cellular and molecular abnormalities that suggest decreased or faulty innervation and/or dysregulation of intracellular signaling. A unifying mechanistic hypothesis may be the epigenetic regulation of gene expression. With the opportunity to obtain olfactory neural tissue from live patients through nasal epithelial biopsy, the peripheral olfactory system offers a uniquely accessible window through which the pathophysiological antecedents and sequelae of schizophrenia may be observed. This could help to clarify underlying brain mechanisms and facilitate identification of clinically relevant biomarkers.

Neuregulin 1 transgenic mice display reduced mismatch negativity, contextual fear conditioning and social interactions

INTRODUCTION

Neuregulin-1 (NRG1) is one of susceptibility genes for schizophrenia and plays critical roles in glutamatergic, dopaminergic and GABAergic signaling. Using mutant mice heterozygous for Nrg1 (Nrg1(+/-)) we studied the effects of Nrg1 signaling on behavioral and electrophysiological measures relevant to schizophrenia.

EXPERIMENTAL PROCEDURE

Behavior of Nrg1(+/-) mice and their wild type littermates was evaluated using pre-pulse inhibition, contextual fear conditioning, novel object recognition, locomotor, and social choice paradigms. Event-related potentials (ERPs) were recorded to assess auditory gating and novel stimulus detection.

RESULTS

Gating of ERPs was unaffected in Nrg1(+/-) mice, but mismatch negativity in response to novel stimuli was attenuated. The Nrg1(+/-) mice exhibited behavioral deficits in contextual fear conditioning and social interactions, while locomotor activity, pre-pulse inhibition and novel object recognition were not impaired.

SUMMARY

Nrg1(+/-) mice had impairments in a subset of behavioral and electrophysiological tasks relevant to the negative/cognitive symptom domains of schizophrenia that are thought to be influenced by glutamatergic and dopaminergic neurotransmission. These mice are a valuable tool for studying endophenotypes of schizophrenia, but highlight that single genes cannot account for the complex pathophysiology of the disorder.

Dysbindin-1 in dorsolateral prefrontal cortex of schizophrenia cases is reduced in an isoform-specific manner unrelated to dysbindin-1 mRNA expression

DTNBP1 (dystrobrevin binding protein 1) remains a top candidate gene in schizophrenia. Reduced expression of this gene and of its encoded protein, dysbindin-1, have been reported in the brains of schizophrenia cases. It has not been established, however, if the protein reductions encompass all dysbindin-1 isoforms or if they are associated with decreased DTNBP1 gene expression. Using a matched pairs design in which each of 28 Caucasian schizophrenia cases was matched in age and sex to a normal Caucasian control, Western blotting of whole-tissue lysates of dorsolateral prefrontal cortex (DLPFC) revealed significant reductions in dysbindin-1C (but not in dysbindin-1A or -1B) in schizophrenia (P = 0.022). These reductions occurred without any significant change in levels of the encoding transcript in the same tissue samples and in the absence of the only DTNBP1 risk haplotype for schizophrenia reported in the USA. Indeed, no significant correlations were found between case-control differences in any dysbindin-1 isoform and the case-control differences in its encoding mRNA. Consequently, the mean 60% decrease in dysbindin-1C observed in 71% of our case-control pairs appears to reflect abnormalities in mRNA translation and/or processes promoting dysbindin-1C degradation (e.g. oxidative stress, phosphorylation and/or ubiquitination). Given the predominantly post-synaptic localization of dysbindin-1C and known post-synaptic effects of dysbindin-1 reductions in the rodent equivalent of the DLPFC, the present findings suggest that decreased dysbindin-1C in the DLPFC may contribute to the cognitive deficits of schizophrenia by promoting NMDA receptor hypofunction in fast-spiking interneurons.

Novel environment and GABA agonists alter event-related potentials in N-methyl-D-aspartate NR1 hypomorphic and wild-type mice

Clinical and experimental data suggest dysregulation of N-methyl-d-aspartate receptor (NMDAR)-mediated glutamatergic pathways in schizophrenia. The interaction between NMDAR-mediated abnormalities and the response to novel environment has not been studied. Mice expressing 5 to 10% of normal N-methyl-d-aspartate receptor subunit 1 (NR1) subunits [NR1(neo)(-/-)] were compared with wild-type littermates for positive deflection at 20 ms (P20) and negative deflection at 40 ms (N40) auditory event-related potentials (ERPs). Groups were tested for habituation within and across five testing sessions, with novel environment tested during a sixth session. Subsequently, we examined the effects of a GABA(A) positive allosteric modulator (chlordiazepoxide) and a GABA(B) receptor agonist (baclofen) as potential interventions to normalize aberrant responses. There was a reduction in P20, but not N40 amplitude within each habituation day. Although there was no amplitude or gating change across habituation days, there was a reduction in P20 and N40 amplitude and gating in the novel environment. There was no difference between genotypes for N40. Only NR1(neo)(-/-) mice had reduced P20 in the novel environment. Chlordiazepoxide increased N40 amplitude in wild-type mice, whereas baclofen increased P20 amplitude in NR1(neo)(-/-) mice. As noted in previous publications, the pattern of ERPs in NR1(neo)(-/-) mice does not recapitulate abnormalities in schizophrenia. In addition, reduced NR1 expression does not influence N40 habituation but does affect P20 in a novel environment. Thus, the pattern of P50 (positive deflection at 50 ms) but not N100 (negative deflection at 100 ms) in human studies may relate to subjects' reactions to unfamiliar environments. In addition, NR1 reduction decreased GABA(A) receptor-mediated effects on ERPs while causing increased GABA(B) receptor-mediated effects. Future studies will examine changes in GABA receptor subunits after reductions in NR1 expression.

Smoking-associated squamous metaplasia in olfactory mucosa of patients with chronic rhinosinusitis

Few studies have examined the induction of squamous metaplasia in human olfactory nasal tissue caused by tobacco use and the implications it may have for olfaction, particularly when there are pre-existing insults, such as chronic rhinosinusitis (CRS). Quantitative histopathological analyses were performed on Alcian blue- and H&E-stained sections of nasal biopsies taken from the upper aspect of the middle turbinate of CRS patients. Chronic rhinosinusitis patients who were current smokers had a predominance of squamous metaplasia in the olfactory sensory epithelium, whereas CRS patients who were nonsmokers and were not exposed to secondhand cigarette smoke had a prevalence of goblet cell hyperplasia. In spite of this difference, the groups did not differ significantly in olfactory threshold sensitivity. The impact of primary cigarette smoke on olfaction and a possible role of squamous metaplasia in preserving olfactory neurogenesis are discussed.

The post-synaptic density of human postmortem brain tissues: an experimental study paradigm for neuropsychiatric illnesses

Recent molecular genetics studies have suggested various trans-synaptic processes for pathophysiologic mechanisms of neuropsychiatric illnesses. Examination of pre- and post-synaptic scaffolds in the brains of patients would greatly aid further investigation, yet such an approach in human postmortem tissue has yet to be tested. We have examined three methods using density gradient based purification of synaptosomes followed by detergent extraction (Method 1) and the pH based differential extraction of synaptic membranes (Methods 2 and 3). All three methods separated fractions from human postmortem brains that were highly enriched in typical PSD proteins, almost to the exclusion of pre-synaptic proteins. We examined these fractions using electron microscopy (EM) and verified the integrity of the synaptic membrane and PSD fractions derived from human postmortem brain tissues. We analyzed protein composition of the PSD fractions using two dimensional liquid chromatography tandem mass spectrometry (2D LC-MS/MS) and observed known PSD proteins by mass spectrometry. Immunoprecipitation and immunoblot studies revealed that expected protein-protein interactions and certain posttranscriptional modulations were maintained in PSD fractions. Our results demonstrate that PSD fractions can be isolated from human postmortem brain tissues with a reasonable degree of integrity. This approach may foster novel postmortem brain research paradigms in which the stoichiometry and protein composition of specific microdomains are examined.

Deficits in docosahexaenoic acid and associated elevations in the metabolism of arachidonic acid and saturated fatty acids in the postmortem orbitofrontal cortex of patients with bipolar disorder

Previous antemortem and postmortem tissue fatty acid composition studies have observed significant deficits in the omega-3 fatty acid docosahexaenoic acid (DHA, 22:6n-3) in red blood cell (RBC) and postmortem cortical membranes of patients with unipolar depression. In the present study, we determined the fatty acid composition of postmortem orbitofrontal cortex (OFC, Brodmann area 10) of patients with bipolar disorder (n=18) and age-matched normal controls (n=19) by gas chromatography. After correction for multiple comparisons, DHA (-24%), arachidonic acid (-14%), and stearic acid (C18:0) (-4.5%) compositions were significantly lower, and cis-vaccenic acid (18:1n-7) (+12.5%) composition significantly higher, in the OFC of bipolar patients relative to normal controls. Based on metabolite:precursor ratios, significant elevations in arachidonic acid, stearic acid, and palmitic acid conversion/metabolism were observed in the OFC of bipolar patients, and were inversely correlated with DHA composition. Deficits in OFC DHA and arachidonic acid composition, and elevations in arachidonic acid metabolism, were numerically (but not significantly) greater in drug-free bipolar patients relative to patients treated with mood-stabilizer or antipsychotic medications. OFC DHA and arachidonic acid deficits were greater in patients plus normal controls with high vs. low alcohol abuse severity. These results add to a growing body of evidence implicating omega-3 fatty acid deficiency as well as the OFC in the pathoaetiology of bipolar disorder.

A randomized, controlled trial of cognitive-behavioral therapy for augmenting pharmacotherapy in obsessive-compulsive disorder

OBJECTIVE

Although serotonin reuptake inhibitors (SRIs) are approved for the treatment of obsessive-compulsive disorder (OCD), most OCD patients who have received an adequate SRI trial continue to have clinically significant OCD symptoms. The purpose of this study was to examine the effects of augmenting SRIs with exposure and ritual prevention, an established cognitive-behavioral therapy (CBT) for OCD.

METHOD

A randomized, controlled trial was conducted at two academic outpatient clinics to compare the effects of augmenting SRIs with exposure and ritual prevention versus stress management training, another form of CBT. Participants were adult outpatients (N=108) with primary OCD and a Yale-Brown Obsessive Compulsive Scale total score > or = 16 despite a therapeutic SRI dose for at least 12 weeks prior to entry. Participants received 17 sessions of CBT (either exposure and ritual prevention or stress management training) twice a week while continuing SRI pharmacotherapy.

RESULTS

Exposure and ritual prevention was superior to stress management training in reducing OCD symptoms. At week 8, significantly more patients receiving exposure and ritual prevention than patients receiving stress management training had a decrease in symptom severity of at least 25% (based on Yale-Brown Obsessive Compulsive Scale scores) and achieved minimal symptoms (defined as a Yale-Brown Obsessive Compulsive Scale score < or = 12).

CONCLUSIONS

Augmentation of SRI pharmacotherapy with exposure and ritual prevention is an effective strategy for reducing OCD symptoms. However, 17 sessions were not sufficient to help most of these patients achieve minimal symptoms.

Selective deficits in the omega-3 fatty acid docosahexaenoic acid in the postmortem orbitofrontal cortex of patients with major depressive disorder

BACKGROUND

Epidemiological surveys and peripheral tissue (red blood cells/plasma) fatty acid composition studies suggest that omega-3 fatty acid deficiency is associated with major depressive disorder (MDD) and suicide. It was hypothesized that patients with MDD would exhibit lower frontal cortical concentrations of docosahexaenoic acid (DHA), the principal omega-3 fatty acid in brain, relative to normal controls.

METHODS

We determined the total fatty acid composition of postmortem orbitofrontal cortex (Brodmann's Area 10) from patients with DSM-IV-defined MDD (n = 15) and age-matched normal controls (n = 27) by gas chromatography.

RESULTS

After correction for multiple comparisons, the omega-3 fatty acid DHA was the only fatty acid that was significantly different (-22%) in the postmortem orbitofrontal cortex of MDD patients relative to normal controls. Deficits in DHA concentrations were greater in female MDD patients (-32%) than in male MDD patients (-16%), and could not be wholly attributed to lifestyle factors or postmortem tissue variables.

CONCLUSIONS

These results demonstrate a selective deficit in the omega-3 fatty acid DHA in the orbitofrontal cortex of patients with MDD. This finding adds to a growing body of evidence implicating omega-3 fatty acid deficiency as well as the orbitofrontal cortex in the pathophysiology and potentially pathogenesis of MDD.

Abnormalities in the fatty acid composition of the postmortem orbitofrontal cortex of schizophrenic patients: gender differences and partial normalization with antipsychotic medications

Previous studies have observed significant abnormalities in the fatty acid composition of peripheral tissues from drug-naïve first-episode schizophrenic (SZ) patients relative to normal controls, including deficits in omega-3 and omega-6 polyunsaturated fatty acids, which are partially normalized following chronic antipsychotic treatment. We hypothesized that postmortem cortical tissue from patients with SZ would also exhibit deficits in cortical docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (AA; 20:4n-6) relative to normal controls, and that these deficits would be greater in drug-free SZ patients. We determined the total fatty acid composition of postmortem orbitofrontal cortex (OFC) (Brodmann area 10) from drug-free and antipsychotic-treated SZ patients (n=21) and age-matched normal controls (n=26) by gas chromatography. After correction for multiple comparisons, significantly lower DHA (-20%) concentrations, and significantly greater vaccenic acid (VA) (+12.5) concentrations, were found in the OFC of SZ patients relative to normal controls. Relative to age-matched same-gender controls, OFC DHA deficits, and elevated AA:DHA, oleic acid:DHA and docosapentaenoic acid (22:5n-6):DHA ratios, were found in male but not female SZ patients. SZ patients that died of cardiovascular-related disease exhibited lower DHA (-31%) and AA (-19%) concentrations, and greater OA (+20%) and VA (+17%) concentrations, relative to normal controls that also died of cardiovascular-related disease. OFC DHA and AA deficits, and elevations in oleic acid and vaccenic acid, were numerically greater in drug-free SZ patients and were partially normalized in SZ patients treated with antipsychotic medications (atypical>typical). Fatty acid abnormalities could not be wholly attributed to lifestyle or postmortem tissue variables. These findings add to a growing body of evidence implicating omega-3 fatty acid deficiency as well as the OFC in the pathoaetiology of SZ, and suggest that abnormalities in OFC fatty acid composition may be gender-specific and partially normalized by antipsychotic medications.

Augmentation of sertraline with prolonged exposure in the treatment of posttraumatic stress disorder

The present study was designed to determine whether augmenting sertraline with prolonged exposure (PE) would result in greater improvement than continuation with sertraline alone. Outpatient men and women with chronic PTSD completed 10 weeks of open label sertraline and then were randomly assigned to five additional weeks of sertraline alone (n = 31) or sertraline plus 10 sessions of twice-weekly PE (n = 34). Results indicated that sertraline led to a significant reduction in PTSD severity after 10 weeks but was associated with no further reductions after five more weeks. Participants who received PE showed further reduction in PTSD severity. This augmentation effect was observed only for participants who showed a partial response to medication.

Dysbindin-1 is a synaptic and microtubular protein that binds brain snapin

Variations in the gene encoding the novel protein dysbindin-1 (DTNBP1) are among the most commonly reported genetic variations associated with schizophrenia. Recent studies show that those variations are also associated with cognitive functioning in carriers with and without psychiatric diagnoses, suggesting a general role for dysbindin-1 in cognition. Such a role could stem from the protein's known ability to affect neuronal glutamate release. How dysbindin-1 might affect glutamate release nevertheless remains unknown without the discovery of the protein's neuronal binding partners and its subcellular locus of action. We demonstrate here that snapin is a binding partner of dysbindin-1 in vitro and in the brain. Tissue fractionation of whole mouse brains and human hippocampal formations revealed that both dysbindin-1 and snapin are concentrated in tissue enriched in synaptic vesicle membranes and less commonly in postsynaptic densities. It is not detected in presynaptic tissue fractions lacking synaptic vesicles. Consistent with that finding, immunoelectron microscopy showed that dysbindin-1 is located in (i) synaptic vesicles of axospinous terminals in the dentate gyrus inner molecular layer and CA1 stratum radiatum and in (ii) postsynaptic densities and microtubules of dentate hilus neurons and CA1 pyramidal cells. The labeled synapses are often asymmetric with thick postsynaptic densities suggestive of glutamatergic synapses, which are likely to be derived from dentate mossy cells and CA3 pyramidal cells. The function of dysbindin-1 in presynaptic, postsynaptic and microtubule locations may all be related to known functions of snapin.

Altered neuregulin 1-erbB4 signaling contributes to NMDA receptor hypofunction in schizophrenia

Recent molecular genetics studies implicate neuregulin 1 (NRG1) and its receptor erbB in the pathophysiology of schizophrenia. Among NRG1 receptors, erbB4 is of particular interest because of its crucial roles in neurodevelopment and in the modulation of N-methyl-D-aspartate (NMDA) receptor signaling. Here, using a new postmortem tissue-stimulation approach, we show a marked increase in NRG1-induced activation of erbB4 in the prefrontal cortex in schizophrenia. Levels of NRG1 and erbB4, however, did not differ between schizophrenia and control groups. To evaluate possible causes for this hyperactivation of erbB4 signaling, we examined the association of erbB4 with PSD-95 (postsynaptic density protein of 95 kDa), as this association has been shown to facilitate activation of erbB4. Schizophrenia subjects showed substantial increases in erbB4-PSD-95 interactions. We found that NRG1 stimulation suppresses NMDA receptor activation in the human prefrontal cortex, as previously reported in the rodent cortex. NRG1-induced suppression of NMDA receptor activation was more pronounced in schizophrenia subjects than in controls, consistent with enhanced NRG1-erbB4 signaling seen in this illness. Therefore, these findings suggest that enhanced NRG1 signaling may contribute to NMDA hypofunction in schizophrenia.

Lithium and valproic acid treatments reduce PKC activation and receptor-G protein coupling in platelets of bipolar manic patients

Dysregulated protein kinase C (PKC) distribution and activation, and abnormal receptor-G protein coupling, have been implicated in the pathophysiology of bipolar affective disorder (BD). The therapeutic effectiveness of lithium has also been correlated with its ability to reduce PKC activation and G protein-mediated signaling. We examine the cellular distribution and activation of PKC and receptor-G protein coupling in blood platelets from normal controls, patients with BD mania or schizophrenia during treatment-free state, and after lithium or valproic acid administration. PKC activity was measured under basal and 50 nM phorbol 12-myristate, 13-acetate (PMA), 1 microM serotonin or 0.5 U/ml thrombin-stimulated conditions. The coupling of G proteins to serotonin or thrombin receptors were assessed by serotonin or thrombin-mediated [35S]GTPgammaS binding to membrane Galpha proteins. The results demonstrate that membrane-associated PKC activity and stimulus-induced PKC translocation are increased in BD manic, whereas stimulus-elicited PKC translocation is attenuated in schizophrenic patients. Lithium and valproic acid treatments attenuated the stimulus-induced PKC translocations to a similar degree and decreased PKC activity in both cytosolic and membranous fractions after two weeks of drug administration. An increase in 5-HT or thrombin stimulated [35S]GTPgammaS binding to Galpha proteins was detected in BD manic but not in schizophrenic patients although basal [35S]GTPgammaS binding was not different across the diagnostic groups. Lithium and valproic acid treatments similarly reduced receptor-G protein coupling with comparable time courses. Thus, increased membrane-associated PKC, cytosol to membrane PKC translocation and receptor-G protein coupling in platelets of BD manic patients were alleviated by lithium or valproic acid treatments.

Aberrant intracellular calcium signaling in olfactory neurons from patients with bipolar disorder

OBJECTIVE

The authors examined the feasibility of using olfactory receptor neurons from living patients to test whether calcium signaling is altered in a neuronal cell population in bipolar disorder.

METHOD

Ratiometric fluorescence photomicroscopy was used to assess basal and stimulus-induced changes in intracellular calcium levels in biopsy-derived olfactory receptor neurons from seven euthymic patients with bipolar disorder who were medication-free, 10 euthymic patients with bipolar disorder who were treated with mood stabilizers, and 17 age- and sex-matched comparison subjects without bipolar disorder.

RESULTS

Olfactory receptor neurons from the seven medication-free patients responded to stimuli predominantly with decreases in intracellular calcium, unlike those from the seven matched healthy subjects. Olfactory receptor neurons from patients treated with mood stabilizers were less likely to respond to stimulation than olfactory receptor neurons from medication-free patients.

CONCLUSIONS

This study demonstrates the feasibility of using olfactory receptor neurons to examine alterations in intracellular signaling in neuronal cells from living patients. Our results, although based on a small number of subjects, suggest that altered intracellular calcium signaling in olfactory receptor neurons may be a trait of bipolar disorder.

In vivo and in vitro neurogenesis in human olfactory epithelium

The birth and differentiation of neurons have been extensively studied in the olfactory epithelium (OE) of rodents but not in humans. The goal of this study was to characterize cellular composition and molecular expression of human OE in vivo and in vitro. In rodent OE, there are horizontal basal cells and globose basal cells that are morphologically and functionally distinct. In human OE, however, there appears to be no morphological distinction among basal cells, with almost all cells having round cell bodies similar to rodent globose basal cells. Unlike the case in rodents, human basal cells, including putative neuronal precursors, express p75NGFR, suggesting a distinctive role for p75NGFR in human OE neurogenesis. Molecular expression of neuronal cells during differentiation in human OE grossly follows that in rodents. However, the topographical organization of immature and mature ORNs in human OE differs from that of rodents, in that immature and mature ORNs in humans are dispersed throughout the OE, whereas rodent counterparts have a highly laminar organization. These observations together suggest that the birth and differentiation of neuronal cells in human OE differ from those in rodents. In OE explant culture, neuronal cells derived from human OE biopsy express markers for immature and mature neurons, grossly recapitulating neuronal differentiation of olfactory neurons in vivo. Furthermore, small numbers of cells are doubly label for bromodeoxyuridine and olfactory marker protein, indicating that neuronal cells born in vitro reach maturity. These data highlight species-related differences in OE development and demonstrate the utility of explant culture for experimental studies of human neuronal development.