Building a schizophrenia genetic network: Transcription Factor 4 regulates genes involved in neuronal development and schizophrenia risk
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ABSTRACT: The transcription factor 4 (TCF4) locus is a robust association finding with schizophrenia (SZ), but little is known about the genes regulated by the encoded transcription factor. Therefore, we conducted chromatin immunoprecipitation sequencing (ChIP-seq) of TCF4 in neural-derived (SH-SY5Y) cells to identify genome-wide TCF4 binding sites, followed by data integration with SZ association findings. We identified 11,322 TCF4 binding sites overlapping in two ChIP-seq experiments. These sites are significantly enriched for the TCF4 Ebox binding motif (>85% having ≥1 Ebox) and implicate a gene set enriched for genes down-regulated in TCF4 siRNA knockdown experiments, indicating the validity of our findings. The TCF4 gene set was also enriched among 1) Gene Ontology categories such as axon/neuronal development, 2) genes preferentially expressed in brain, in particular pyramidal neurons of the somatosensory cortex, and 3) genes down-regulated in post-mortem brain tissue from SZ patients (OR=2.8, permutation p<4x10-5). Considering genomic alignments, TCF4 binding sites significantly overlapped those for neural DNA binding proteins such as FOXP2 and the SZ-associated EP300. TCF4 binding sites were modestly enriched among SZ risk loci from the Psychiatric Genomic Consortium (OR=1.56, p=0.03). In total, 130 TCF4 binding sites occurred in 39 of the 108 regions published in 2014. Thirteen genes within the 108 loci had both a TCF4 binding site ±10kb and were differentially expressed in siRNA knockdown experiments of TCF4, suggesting direct TCF4 regulation. These findings confirm TCF4 as an important regulator of neural genes and point towards functional interactions with potential relevance for SZ.
Project description:Common genetic variants in and around the gene encoding transcription factor 4 (TCF4) are associated with an increased risk of schizophrenia whereas rare variants have been found in patients with intellectual disability (ID), developmental disorders and autism spectrum disorder (ASD). Haploinsufficiency of TCF4 also causes Pitt Hopkins syndrome (PTHS); a condition characterized by developmental delay, ID and autonomic dysfunction. To understand the role of TCF4 in these disorders, we have used chromatin immunoprecipitation and next generation sequencing (ChIP-seq) to identify the genomic binding sites for TCF4. In this study we identify 10,604 binding sites assigned to 5,437 genes. De novo motif enrichment found that approximately 77% of the TCF4 binding sites contained at least one E-box (5’-CAtcTG). Furthermore, the majority of TCF4 binding sites overlapped with H3K27ac histone mark for active enhancers. Enrichment analysis on the set of TCF4 targets identified numerous, highly significant functional clusters for pathways including nervous system development, ion transport and signal transduction and co-expression modules for genes associated with synaptic function and brain development. Importantly, we found that genes harboring de novo mutations in schizophrenia (P < 5.3 x 10-7), ASD (P < 2.5 x 10-4) and ID (P < 7.6 x 10-3) were also enriched among TCF4 targets. These data demonstrate that TCF4 binding sites are found in a large number of neuronal genes that include genetic risk factors for common neurodevelopmental disorders.
Project description:Cell-based models of many neurological and psychiatric diseases, established by reprogramming patient somatic cells into human induced pluripotent stem cells (hiPSCs), have now been reported. While numerous reports have demonstrated that neuronal cells differentiated from hiPSCs are electrophysiologically active mature neurons, the âageâ of these cells relative to cells in the human brain remains unresolved. Comparisons of gene expression profiles of hiPSC-derived neural progenitor cells (NPCs) and neurons to the Allen BrainSpan Atlas indicate that hiPSC neural cells most resemble first trimester neural tissue. Consequently, we posit that hiPSC-derived neural cells may most accurately be used to model the early developmental defects that contribute to disease predisposition rather than the late features of the disease. Though the characteristic symptoms of schizophrenia SZ generally appear late in adolescence, it is now thought to be a neurodevelopmental condition, often predated by a prodromal period that can appear in early childhood. Postmortem studies of SZ brain tissue typically describe defects in mature neurons, such as reduced neuronal size and spine density in the prefrontal cortex and hippocampus, but abnormalities of neuronal organization, particularly in the cortex, have also been reported. We postulated that defects in cortical organization in SZ might result from abnormal migration of neural cells. To test this hypothesis, we directly reprogrammed fibroblasts from SZ patients into hiPSCs and subsequently differentiated these disorder-specific hiPSCs into NPCs. SZ hiPSC differentiated into forebrain NPCs have altered expression of a number of cellular adhesion genes and WNT signaling. Methods: We compared global transcription of forebrain NPCs from six control and four SZ patients by RNAseq. Results: Multi-dimensional scaling (MDS) resolved most SZ and control hiPSC NPC samples; 848 genes were significantly differentially expressed (FDR<0.01) Conclusions: The WNT signaling pathway was enriched 2-fold (fisher exact test p-value = 0.031). 1-2 independent differentiations (biological replicates) for each of four control and four schizophrenia patients were analyzed; samples were generated in parallel to neuron RNAseq data.
Project description:Cell-based models of many neurological and psychiatric diseases, established by reprogramming patient somatic cells into human induced pluripotent stem cells (hiPSCs), have now been reported. While numerous reports have demonstrated that neuronal cells differentiated from hiPSCs are electrophysiologically active mature neurons, the “age” of these cells relative to cells in the human brain remains unresolved. Comparisons of gene expression profiles of hiPSC-derived neural progenitor cells (NPCs) and neurons to the Allen BrainSpan Atlas indicate that hiPSC neural cells most resemble first trimester neural tissue. Consequently, we posit that hiPSC-derived neural cells may most accurately be used to model the early developmental defects that contribute to disease predisposition rather than the late features of the disease. Though the characteristic symptoms of schizophrenia SZ generally appear late in adolescence, it is now thought to be a neurodevelopmental condition, often predated by a prodromal period that can appear in early childhood. Postmortem studies of SZ brain tissue typically describe defects in mature neurons, such as reduced neuronal size and spine density in the prefrontal cortex and hippocampus, but abnormalities of neuronal organization, particularly in the cortex, have also been reported. We postulated that defects in cortical organization in SZ might result from abnormal migration of neural cells. To test this hypothesis, we directly reprogrammed fibroblasts from SZ patients into hiPSCs and subsequently differentiated these disorder-specific hiPSCs into NPCs. SZ hiPSC differentiated into forebrain NPCs have altered expression of a number of cellular adhesion genes and WNT signaling. Methods: We compared global transcription of forebrain NPCs from six control and four SZ patients by RNAseq. Results: Multi-dimensional scaling (MDS) resolved most SZ and control hiPSC NPC samples; 848 genes were significantly differentially expressed (FDR<0.01) Conclusions: The WNT signaling pathway was enriched 2-fold (fisher exact test p-value = 0.031).
Project description:Cell-based models of many neurological and psychiatric diseases, established by reprogramming patient somatic cells into human induced pluripotent stem cells (hiPSCs), have now been reported. While numerous reports have demonstrated that neuronal cells differentiated from hiPSCs are electrophysiologically active mature neurons, the “age” of these cells relative to cells in the human brain remains unresolved. Comparisons of gene expression profiles of hiPSC-derived neural progenitor cells (NPCs) and neurons to the Allen BrainSpan Atlas indicate that hiPSC neural cells most resemble first trimester neural tissue. Consequently, we posit that hiPSC-derived neural cells may most accurately be used to model the early developmental defects that contribute to disease predisposition rather than the late features of the disease. Though the characteristic symptoms of schizophrenia SZ generally appear late in adolescence, it is now thought to be a neurodevelopmental condition, often predated by a prodromal period that can appear in early childhood. Postmortem studies of SZ brain tissue typically describe defects in mature neurons, such as reduced neuronal size and spine density in the prefrontal cortex and hippocampus. We directly reprogrammed fibroblasts from SZ patients into hiPSCs and subsequently differentiated these disorder-specific hiPSCs into forebrain neurons. SZ hiPSC differentiated into forebrain neurons have altered expression of a number of synaptic genes. Methods: We compared global transcription of forebrain neurons from six control and four SZ patients by RNAseq. Results: Multi-dimensional scaling (MDS) resolved most SZ and control hiPSC neuron samples; 107 genes were significantly differentially expressed (FDR<0.01)
Project description:BACKGROUND: Common variants in the TCF4 gene are among the most robustly supported genetic risk factors for schizophrenia. Rare TCF4 deletions and loss-of-function point mutations cause Pitt-Hopkins syndrome, a developmental disorder associated with severe intellectual disability. METHODS: In order to explore molecular and cellular mechanisms by which TCF4 perturbation could interfere with human cortical development, we experimentally reduced the endogenous expression of TCF4 in a neural progenitor cell line derived from the developing human cerebral cortex using RNA interference. Effects on genome-wide gene expression were assessed by microarray, followed by Gene Ontology and pathway analysis of differentially expressed genes. Effects on cell proliferation were assessed using high content imaging. RESULTS: Genes that were differentially expressed following TCF4 knockdown were highly enriched for involvement in the cell cycle. Consistent with the gene expression data, TCF4 knockdown was associated with reduced proliferation of cortical progenitor cells in vitro. CONCLUSIONS: Our data indicate effects of TCF4 perturbation on human cortical progenitor cell proliferation, a process that could contribute to cognitive deficits in Pitt-Hopkins Syndrome and risk for schizophrenia.
Project description:Individuals with 22q11.2 Deletion Syndrome (22q11.2 DS) are a specific high-risk group for developing schizophrenia (SZ), schizoaffective disorder (SAD) and autism spectrum disorders (ASD). Several genes in the deleted region have been implicated in the development of SZ, e.g., PRODH and DGCR8. However, the mechanistic connection between these genes and the neuropsychiatric phenotype remains unclear. To elucidate the molecular consequences of 22q11.2 deletion in early neural development, we carried out RNA-seq analysis to investigate gene expression in differentiating human neurons derived from induced pluripotent stem cells (iPSCs) of 22q11.2 DS SZ and SAD patients. Eight cases (ten iPSC-neuron samples in total including duplicate clones) and seven controls (nine in total including duplicate clones) were subject to RNA sequencing. Using a systems level analysis, differentially expressed genes/gene-modules and pathway of interests were identified. We observed ~2-fold reduction in expression of almost all genes in the 22q11.2 region in SZ (37 genes reached p-value < 0.05, 36 of which reached a false discovery rate < 0.05). Outside of the deleted region, 745 genes showed significant differences in expression between SZ and control neurons (p<0.05). Function enrichment and network analysis of the differentially expressed genes uncovered converging evidence on abnormal expression in key functional pathways, such as apoptosis, cell cycle and survival, and MAPK signaling in the SZ and SAD samples.
Project description:DNA methylation (DNAm) signal from the planum temporale of superior temporal gyrus (STG) of forty-four subjects with schizophrenia (SZ) and forty-four non-psychiatric control (NPC) subjects was measured on the Illumina MethylationEPIC BeadChip Infinium (EPIC) array. Averaged, normalized beta-values at each site were correlated with dendritic spine density (DSD) previously measured per subject to identify site-specific DNAm-DSD correlations that met methylome-wide significance, or a suggestive-level of significance. We tested the hypothesis that DNAm correlates with DSD in human STG at several sites across the methylome and that this relationship is disrupted in SZ. DSD measures were available for 40 of the subjects with SZ and 40 of the NPC subjects. We found DNAm to correlate with DSD at more sites than expected by chance in NPC, but not SZ, subjects. In addition, we show that the slopes of the linear DNAm-DSD correlations differed between SZ and NPC subjects at more sites than expected by chance. Together, these data suggest that alterations in the intercation between DNAm and neurobiology in SZ may be a mechanism for SZ-related DSD reductions.
Project description:We have previously demonstrated functional and molecular changes in hippocampal subfields in individuals with schizophrenia (SZ) psychosis associated with hippocampal excitability. In this study, we use RNA-seq and assess global transcriptome changes in the hippocampal subfields, DG, CA3, and CA1 from individuals with SZ psychosis and controls to elucidate subfield-relevant molecular changes. We also examine changes in gene expression due to antipsychotic medication in the hippocampal subfields from our SZ ON- and OFF-antipsychotic medication cohort. We identify unique subfield-specific molecular profiles in schizophrenia postmortem samples compared to controls, implicating astrocytes in DG, immune mechanisms in CA3, and synaptic scaling in CA1. We show a unique pattern of subfield-specific effects by antipsychotic medication on gene expression levels with scant overlap of genes differentially expressed by SZ disease effect versus medication effect. These hippocampal subfield changes could provide the basis for previously observed hippocampal SZ pathology and explain the lack of full efficacy of conventional antipsychotic medication on SZ symptomatology. With further characterization, the identified distinct molecular profiles of the DG, CA3, and CA1 in SZ psychosis may serve to identify potential hippocampal-based therapeutic targets.
Project description:The edited lines introduced a premature termination at rs757148409/p.Arg89Ter. The mutant iNs showed a ~50% decrease in OTUD7A protein expression without undergoing nonsense-mediated mRNA decay. The mutant iNs also exhibited marked reduction of dendritic complexity, synaptic puncta density of AMPA receptor subunit GluA1 and postsynaptic scaffold PSD-95, as well as neural firing rate and network activity. Congruent with the neural phenotypic alterations in mutant iNs, our transcriptomic analysis showed that the set of OTUD7A LoF downregulated genes was significantly enriched for synapse development and function, and was associated with SZ and other neuropsychiatric disorders. These results suggest that the OTUD7A LoF mutation rs757148409 impairs neurodevelopment and synaptic function in human neurons, providing mechanistic insight into the possible role of OTUD7A in driving neuropsychiatric phenotypes associated with the 15q13.3 microdeletion.