ABSTRACT: Gene expression of L3 and L5 pyramidal neurons in the DLPFC comparing schizophrenia from bipolar major depressive disorders and unaffected subjects.
Project description:Impairments in certain cognitive processes (e.g., working memory) are typically most pronounced in schizophrenia (SZ), intermediate in bipolar disorder (BP) and least in major depressive disorder (MDD). Given that working memory depends, in part, on neural circuitry that includes pyramidal neurons in layer 3 (L3) and layer 5 (L5) of the dorsolateral prefrontal cortex (DLPFC), we sought to determine if transcriptome alterations in these neurons were shared or distinctive for each diagnosis.
Project description:Schizophrenia is a complex psychiatric disorder encompassing a range of symptoms and etiology dependent upon the interaction of genetic and environmental factors. Several risk genes, such as DISC1, have been associated with schizophrenia as well as bipolar disorder (BPD) and major depressive disorder (MDD), consistent with the hypothesis that a shared genetic architecture could contribute to divergent clinical syndromes. The present study compared gene expression profiles across three brain regions in post-mortem tissue from matched subjects with schizophrenia, BPD or MDD and unaffected controls. Post-mortem brain tissue was collected from control subjects and well-matched subjects with schizophrenia, BPD, and MDD (n=19 from each group). RNA was isolated from hippocampus, Brodmann Area 46, and associative striatum and hybridized to U133_Plus2 Affymetrix chips. Data were normalized by RMA, subjected to pairwise comparison followed by Benjamini and Hochberg False Discovery Rate correction (FDR). Samples derived from patients with schizophrenia exhibited many more changes in gene expression across all brain regions than observed in BPD or MDD. Several genes showed changes in both schizophrenia and BPD, though the magnitude of change was usually larger in schizophrenia. Several genes that have variants associated with schizophrenia were found to have altered expression in multiple regions of brains from subjects with schizophrenia. Continued evaluation of circuit-level alterations in gene expression and gene-network relationships may further our understanding of how genetic variants may be influencing biological processes to contribute to psychiatric disease. Pre-frontal cortex, striatum and hippocampus were obtained from subjects with schizophrenia, bipolar disorder, major depressive disorder and matched controls.
Project description:Schizophrenia is associated with alterations in working memory that reflect dysfunction of dorsolateral prefrontal cortex (DLPFC) circuitry. Working memory depends on the activity of excitatory pyramidal cells in DLPFC layer 3, and to a lesser extent in layer 5. Although many studies have profiled gene expression in DLPFC gray matter in schizophrenia, little is known about cell type-specific transcript expression in these two populations of pyramidal cells. We hypothesized that interrogating gene expression specifically in DLPFC layer 3 or 5 pyramidal cells would reveal new and/or more robust schizophrenia-associated differences that would provide new insights into the nature of pyramidal cell dysfunction in the illness.
Project description:Emerging high-throughput proteomic technologies have recently been considered as a powerful means of identifying substrates involved in mood disorders. We performed proteomic profiling using liquid chromatography-tandem mass spectrometry to identify dysregulated proteins in plasma samples of 44, 49, and 50 patients with major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia , respectively, in comparison to 51 healthy controls (HCs).
Project description:Schizophrenia is associated with dysfunction of the dorsolateral prefrontal cortex (DLPFC). This dysfunction is manifest as cognitive deficits that appear to arise from disturbances in gamma frequency oscillations. These oscillations are generated in DLPFC layer 3 via reciprocal connections between pyramidal cells and parvalbumin (PV)-containing interneurons. The density of cortical PV neurons is not altered in schizophrenia, but expression levels of several transcripts involved in PV cell function, including PV, are lower in the disease.
Project description:Schizophrenia is a complex psychiatric disorder encompassing a range of symptoms and etiology dependent upon the interaction of genetic and environmental factors. Several risk genes, such as DISC1, have been associated with schizophrenia as well as bipolar disorder (BPD) and major depressive disorder (MDD), consistent with the hypothesis that a shared genetic architecture could contribute to divergent clinical syndromes. The present study compared gene expression profiles across three brain regions in post-mortem tissue from matched subjects with schizophrenia, BPD or MDD and unaffected controls. Post-mortem brain tissue was collected from control subjects and well-matched subjects with schizophrenia, BPD, and MDD (n=19 from each group). RNA was isolated from hippocampus, Brodmann Area 46, and associative striatum and hybridized to U133_Plus2 Affymetrix chips. Data were normalized by RMA, subjected to pairwise comparison followed by Benjamini and Hochberg False Discovery Rate correction (FDR). Samples derived from patients with schizophrenia exhibited many more changes in gene expression across all brain regions than observed in BPD or MDD. Several genes showed changes in both schizophrenia and BPD, though the magnitude of change was usually larger in schizophrenia. Several genes that have variants associated with schizophrenia were found to have altered expression in multiple regions of brains from subjects with schizophrenia. Continued evaluation of circuit-level alterations in gene expression and gene-network relationships may further our understanding of how genetic variants may be influencing biological processes to contribute to psychiatric disease.
Project description:RNA expression in immortalized lymphocytes of schizophrenia and bipolar disorders patients were compared to that of their non-affected relatives to identify genes showing significant differences in expression. The study subjects were recruited in the Eastern Quebec kindred study.
Project description:Pyramidal neurons in the cortex are embedded in distinct information processing pathways. Cortical layer 5 (L5) intratelencephalic (IT) and pyramidal tract (PT) neurons receive different input and project to distinct brain regions. The synaptic molecular signatures that define synaptic connectivity and function of L5 IT and PT neurons are largely unknown. Here, we use an optimized proximity biotinylation workflow to characterize the excitatory postsynaptic proteomes of L5 IT and PT neurons in intact somatosensory circuits. We find that differential expression of neurotransmitter receptors, ion channels and cell-surface proteins (CSPs), most prominently of the leucine-rich repeat (LRR) family, specifies L5 IT and PT neuron input connectivity and function. Our analysis further uncovers differential vulnerability to neurodevelopmental disorders for L5 IT and PT neurons, with a marked enrichment of autism risk genes in the postsynaptic excitatory proteome of IT, but not of PT, neurons. Together, cell type- and input type-specific synaptic proteome profiling implies that many of the proteins specifying connectivity and function of two closely related cortical pyramidal cell types also underlie their differential vulnerability to neurodevelopmental disorders.
Project description:Genome wide association studies of schizophrenia encompassing the major histocompatibility locus (MHC) were highly significant following genome wide correction. This broad region implicates many genes including the MHC complex class II. Within this interval we examined the expression of two MHC II genes (HLA-DPA1 and HLA-DRB1) in brain from individual subjects with schizophrenia (SZ), bipolar disorder (BD), major depressive disorder (MDD), and controls by differential gene expression methods. A third MHC II mRNA, CD74, was studied outside of the MHC II locus, as it interacts within the same immune complex. HLA-DPA1 and CD74 were both reduced in hippocampus, amygdala, and dorsolateral prefrontal cortex regions in SZ and BD compared to controls by specific qPCR assay. We found several novel HLA-DPA1 mRNA variants spanning HLA-DPA1 exons 2-3-4 as suggested by an exon microarray study. The intronic rs9277341 SNP was a significant cis expression quantitative trait locus (eQTL) that was associated with the total expression of HLA-DPA1 in five brain regions. A biomarker study of MHC II mRNAs was conducted in SZ, BD, MDD, and control lymphoblastic cell lines (LCL) by qPCR assay of 87 subjects. There was significantly decreased expression of HLA-DPA1 and CD74 in BD, and trends for reductions in SZ in LCLs. The discovery of multiple splicing variants in brain for HLA-DPA1 is important as the HLA-DPA1 gene is highly conserved, there are no reported splicing variants, and the functions in brain are unknown. Future work on the function and localization of MHC Class II proteins in brain will help to understand the role of alterations in neuropsychiatric disorders. The HLA-DPA1 eQTL is located within a large linkage disequilibrium block that has an irrefutable association with schizophrenia. Future tests in a larger cohort are needed to determine the significance of this eQTL association with schizophrenia. Our findings support the long held hypothesis that alterations in immune function are associated with the pathophysiology of psychiatric disorders. There were 20 anterior cingulate postmortem brain samples that were extracted for total RNA, and analyzed using Affymetrix Exon Array (bipolar disorder subjects n = 9, controls n = 11).