Quantitative analysis of group-specific brain tissue probability map for schizophrenic patients

We developed group-specific tissue probability map (TPM) for gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF) on the common spatial coordinates of an averaged brain atlas derived from normal controls (NC) and from schizophrenic patients (SZ). To identify differences in group-specific TPMs, we used quantitative evaluation methods based on differences in probabilistic distribution as a global criterion, and the mean probability and the similarity index (SI) by lobe as regional criteria. The SZ group showed more spatial variation with a lower mean probability than NC subjects. And, for the right temporal and left parietal lobes, the SI between each group was lower than the other lobes. It can be said that there were significant differences in spatial distribution between controls and schizophrenic patients at those areas. In case of female group, although group differences in the volumes of GM and WM were not significant, global difference in the probabilistic distribution of GM was more prominent and the SI was lower and its descent rate was greater in all lobes, compared with the male group. If these morphological differences caused by disease or group-specific features were not considered in TPM, the accuracy and certainty of specific group studies would be greatly reduced. Therefore, suitable TPM is required as a common framework for functional neuroimaging studies and an a priori knowledge of tissue classification

The immediate early gene Egr3 Is required for hippocampal induction of Bdnf by electroconvulsive stimulation

Early growth response 3 (Egr3) is an immediate early gene (IEG) that is regulated downstream of a cascade of genes associated with risk for psychiatric disorders, and dysfunction of Egr3 itself has been implicated in schizophrenia, bipolar disorder, and depression. As an activity-dependent transcription factor, EGR3 is poised to regulate the neuronal expression of target genes in response to environmental events. In the current study, we sought to identify a downstream target of EGR3 with the goal of further elucidating genes in this biological pathway relevant for psychiatric illness risk. We used electroconvulsive stimulation (ECS) to induce high-level expression of IEGs in the brain, and conducted expression microarray to identify genes differentially regulated in the hippocampus of Egr3-deficient (-/-) mice compared to their wildtype (WT) littermates. Our results replicated previous work showing that ECS induces high-level expression of the brain-derived neurotrophic factor (Bdnf) in the hippocampus of WT mice. However, we found that this induction is absent in Egr3-/- mice. Quantitative real-time PCR (qRT-PCR) validated the microarray results (performed in males) and replicated the findings in two separate cohorts of female mice. Follow-up studies of activity-dependent Bdnf exons demonstrated that ECS-induced expression of both exons IV and VI requires Egr3. In situ hybridization demonstrated high-level cellular expression of Bdnf in the hippocampal dentate gyrus following ECS in WT, but not Egr3-/-, mice. Bdnf promoter analysis revealed eight putative EGR3 binding sites in the Bdnf promoter, suggesting a mechanism through which EGR3 may directly regulate Bdnf gene expression. These findings do not appear to result from a defect in the development of hippocampal neurons in Egr3-/- mice, as cell counts in tissue sections stained with anti-NeuN antibodies, a neuron-specific marker, did not differ between Egr3-/- and WT mice. In addition, Sholl analysis and counts of dendritic spines in golgi-stained hippocampal sections revealed no difference in dendritic morphology or synaptic spine density in Egr3-/-, compared to WT, mice. These findings indicate that Egr3 is required for ECS-induced expression of Bdnf in the hippocampus and suggest that Bdnf may be a downstream gene in our previously identified biologically pathway for psychiatric illness susceptibility.US National Institute of Mental Health [R01MH097803, R21MH113154]; Natural Sciences and Engineering Research Council of CanadaOpen access journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Targeted Proteomics and Biochemical Fractionation: New Tools for Deciphering the Synapse in Schizophrenia

Schizophrenia is a chronic and debilitating psychiatric illness affecting approximately 1% of the world\u27s population for which there is no cure and treatment options are limited. Poor understanding of disease pathology and the difficulty in modeling psychiatric symptoms in animal models has hindered the search for a cure. Despite these difficulties great progress has been made on several fronts. Genetic studies have identified risk genes for disease, while fMRI and histology experiments have located brain regions with altered activity and cytoarchitecture. Pharmacology, molecular and immunology studies have identified receptor signaling pathways that are perturbed as well. One of the biggest challenges currently facing the field is elucidating the mechanisms linking genetic and environmental risk to the altered processes observed in the brains of schizophrenic patients. One approach to this question may be to investigate the postmortem brain tissues of patients. The goal of this thesis is to use mass spectrometry based proteomics to investigate the expression and partitioning of postsynaptic density proteins in these tissues. The postsynaptic density is implicated in disease pathology by genetic, cytoarchitecture and molecular studies. Thus, there is a good possibility that its protein composition reflects the crossroads of genetic risk and dysregulated molecular and developmental processes. A qualitative analysis of the human postsynaptic density was performed to catalog the proteins therein. Data from this experiment was harnessed to develop a mass spectrometry method for the targeted quantification of over 200 synaptic proteins. This method was then used to validate subcellular fractionation of human postmortem brain tissue to capture synaptic microdomains. Finally, this targeted mass spectrometry method was utilized to quantify synaptic protein expression and PSD partitioning in postmortem brain tissues of subjects and patients. The enrichment of PSD proteins was elevated in tissue from schizophrenic subjects compared to controls, while total protein expression was unaltered. This data suggests that partitioning, not expression, of postsynaptic proteins is altered in schizophrenia. The results of this study demonstrate the power of a targeted mass spectrometry approach and provide an important context in which to study the dysregulation of synaptic processes in schizophrenia

Alterations in neuromodulators of GABAergic transmission in the cerebellar cortex of patients with schizophrenia.

One of the most consistent findings in schizophrenia is the dysfunction of specific subsets of GABAergic interneurons in distributed brain regions including the prefrontal cortex and cerebellum. Analyses of post-mortem tissue from cerebellar hemispheres from 13 schizophrenic patients and 13 matched controls by quantitative real-time PCR (qRT-PCR) revealed that the mRNA levels of both the 67 kDa and 65 kDa isoforms of glutamic acid decarboxylase (GAD67 and GAD65) are decreased. Additionally, the presynaptic GABA transporter GAT-1 and the Golgi cell specific neuromodulator metabotropic glutamate receptor 2 (mGluR2) were decreased in the schizophrenic group. Postsynaptic upregulation of GABAA-alpha6 and delta along with downregulation of neuronal nitric oxide synthase (nNOS), a negative modulator of GABA release, were also seen, suggesting a compensatory mechanism to counteract deficits in GABAergic transmission. In addition to GABAergic alterations in schizophrenia, N-methyl-D-aspartate (NMDA) receptor dysfunction has been proposed. To investigate this possibility, we measured NMDA receptor subunit mRNAs in the same samples and found that the NR2B subunit showed a near-significant decrease (p=0.0681) in the patients. In contrast, the kainic acid receptor subunits GluR6 and KA2 were upregulated in the granule cell layer. In an effort to understand the mechanisms for these gene expression changes, we examined adult rats chronically exposed to NMDA receptor antagonist phencyclidine (PCP, 2.58 mg/kg/day, i.p.), which elicits schizophrenia-like symptoms in both humans and animal models. Analyses of PCP-treated rat cerebellar hemispheres demonstrated similar decreases in all GABAergic marker mRNAs as seen in patients, as well as a decrease in Golgi cell GAD67 as shown by quantitative in situ hybridization (qISH). Additionally, decreases in both NR2B and NR2D transcripts, which are present in Golgi cells and colocalize extra-synaptically, were seen. Since low doses of PCP preferentially block NMDA receptors in GABAergic interneurons, chronic PCP administration could preferentially affect Golgi cells in the cerebellum. Deficits in these GABAergic interneurons may lead to disinhibited firing of cerebellar granule cells, as suggested by our previous studies of increased activity-dependent gene expression in these neurons. In conclusion, our results support the notion that GABA deficits are key elements in the pathophysiology of schizophrenia

Association study of polymorphisms in synaptic vesicle-associated genes, SYN2 and CPLX2, with schizophrenia

BACKGROUND: The occurrence of aberrant functional connectivity in the neuronal circuit is one of the integrative theories of the etiology of schizophrenia. Previous studies have reported that the protein and mRNA levels of the synapsin 2 (SYN2) and complexin 2 (CPLX2) genes were decreased in patients with schizophrenia. Synapsin 2 and complexin 2 are involved in synaptogenesis and the modulation of neurotransmitter release. This report presents a study of the association of polymorphisms of SYN2 and CPLX2 with schizophrenia in the Korean population. METHODS: Six single nucleotide polymorphisms (SNPs) and one 5-bp insertion/deletion in SYN2 and five SNPs in CPLX2 were genotyped in 154 Korean patients with schizophrenia and 133 control patients using direct sequencing or restriction fragment length polymorphism analysis. An intermarker linkage disequilibrium map was constructed for each gene. RESULTS: Although there was no significant difference in the genotypic distributions and allelic frequencies of either SYN2 or CPLX2 polymorphisms between the schizophrenia and control groups, the two-way haplotype analyses revealed significant associations with the disease (P < 0.05 after Bonferroni correction). The three-way haplotype analyses also revealed a significant association of SYN2 with schizophrenia (P < 0.001 after Bonferroni correction). CONCLUSION: These results suggest that both SYN2 and CPLX2 may confer susceptibility to schizophrenia in the Korean population