Project description:Cellular identity is determined, in part, by cell type-specific epigenomic profiles that govern gene expression. Isolation and epigenomic characterization of specific cell types is greatly needed in neuroscience. While single cell DNA modification studies offer promise to answer this question, these approaches suffer from limited genomic coverage and cannot differentiate between methylation and hydroxymethylation. Thus, approaches to isolate and analyze DNA from specific CNS cell populations are needed. Here we validate a temporally controlled in vivo nuclear tagging mouse model (NuTRAP) and isolation (INTACT) of neuronal nucleic acids. Analysis of differential DNA modifications (methylation and hydroxymethylation) and gene expression in neurons, astrocytes, and microglia demonstrates a common regulatory function for DNA modifications that transcends cell type. Insight into the normal function of DNA modifications in genomic regulation is crucial in order to better understand the epigenomic mechanisms underlying disease.
Project description:Cellular identity is determined, in part, by cell type-specific epigenomic profiles that govern gene expression. Isolation and epigenomic characterization of specific cell types is greatly needed in neuroscience. While single cell DNA modification studies offer promise to answer this question, these approaches suffer from limited genomic coverage and cannot differentiate between methylation and hydroxymethylation. Thus, approaches to isolate and analyze DNA from specific CNS cell populations are needed. Here we validate a temporally controlled in vivo nuclear tagging mouse model (NuTRAP) and isolation (INTACT) of neuronal nucleic acids. Analysis of differential DNA modifications (methylation and hydroxymethylation) and gene expression in neurons, astrocytes, and microglia demonstrates a common regulatory function for DNA modifications that transcends cell type. Insight into the normal function of DNA modifications in genomic regulation is crucial in order to better understand the epigenomic mechanisms underlying disease.
Project description:BackgroundCellular identity is determined partly by cell type-specific epigenomic profiles that regulate gene expression. In neuroscience, there is a pressing need to isolate and characterize the epigenomes of specific CNS cell types in health and disease. In this study, we developed an in vivo tagging mouse model (Camk2a-NuTRAP) for paired isolation of neuronal DNA and RNA without cell sorting and then used this model to assess epigenomic regulation, DNA modifications in particular, of gene expression between neurons and glia.ResultsAfter validating the cell-specificity of the Camk2a-NuTRAP model, we performed TRAP-RNA-Seq and INTACT-whole genome oxidative bisulfite sequencing (WGoxBS) to assess the neuronal translatome and epigenome in the hippocampus of young mice (4 months old). WGoxBS findings were validated with enzymatic methyl-Seq (EM-Seq) and nanopore sequencing. Comparing neuronal data to microglial and astrocytic data from NuTRAP models, microglia had the highest global mCG levels followed by astrocytes and then neurons, with the opposite pattern observed for hmCG and mCH. Differentially modified regions between cell types were predominantly found within gene bodies and distal intergenic regions, rather than proximal promoters. Across cell types there was a negative correlation between DNA modifications (mCG, mCH, hmCG) and gene expression at proximal promoters. In contrast, a negative correlation of gene body mCG and a positive relationship between distal promoter and gene body hmCG with gene expression was observed. Furthermore, we identified a neuron-specific inverse relationship between mCH and gene expression across promoter and gene body regions.ConclusionsNeurons, astrocytes, and microglia demonstrate different genome-wide levels of mCG, hmCG, and mCH that are reproducible across analytical methods. However, modification-gene expression relationships are conserved across cell types. Enrichment of differential modifications across cell types in gene bodies and distal regulatory elements, but not proximal promoters, highlights epigenomic patterning in these regions as potentially greater determinants of cell identity. These findings also demonstrate the importance of differentiating between mC and hmC in neuroepigenomic analyses, as up to 30% of what is conventionally interpreted as mCG can be hmCG, which often has a different relationship to gene expression than mCG.
Project description:Microglia, brain resident macrophages, require instruction from the central nervous system microenvironment to maintain their identity, morphology, and to regulate inflammatory responses. We investigated the heterogeneity of response of microglia to the presence of neurons and astrocytes by performing single-cell sequencing of microglia in both monoculture, and in coculture with neurons and astrocytes.
Project description:Isolation of glia from Alzheimer's mice reveals inflammation and dysfunction. Reactive astrocytes and microglia are associated with amyloid plaques in Alzheimer's disease (AD). Yet, not much is known about the molecular alterations underlying this reactive phenotype. To get an insight into the molecular changes underlying AD induced astrocyte and microglia reactivity, we performed a transcriptional analysis on acutely isolated astrocytes and microglia from the cortex of aged controls and APPswe/PS1dE9 AD mice. As expected, both cell types acquired a proinflammatory phenotype, which confirms the validity of our approach. Interestingly, we observed that the immune alteration in astrocytes was relatively more pronounced than in microglia. Concurrently, our data reveal that astrocytes display a reduced expression of neuronal support genes and genes involved in neuronal communication. The microglia showed a reduced expression of phagocytosis and/or endocytosis genes. Co-expression analysis of a human AD expression data set and the astrocyte and microglia data sets revealed that the inflammatory changes in astrocytes were remarkably comparable in mouse and human AD, whereas the microglia changes showed less similarity. Based on these findings we argue that chronically proinflammatory astrocyte and microglia phenotypes, showing a reduction of genes involved in neuronal support and neuronal signaling, are likely to contribute to the neuronal dysfunction and cognitive decline in AD. 2 cell types from 2 conditions: cortical microglia and cortical astrocytes from 15-18 month old APPswe/PS1dE9 mice compared to wildtype littermates. Biological replicates: microglia from APPswe/PS1dE9, N=7, microglia from WT, N=7, astrocytes from APPswe/PS1dE9, N=4, microglia from WT, N=4
Project description:Type I interferons (IFN-I) are crucial for effective antimicrobial defence in the central nervous system (CNS) but also can cause severe neurological disease (termed cerebral interferonopathy) as exemplified by Aicardi-Goutières Syndrome and chronic viral infection. In the CNS, microglia and astrocytes have essential roles in host responses to infection and injury, with both cell types responding to IFN-I. However, the extent to which the IFN-I responses of these cells differ, if at all, is still unknown. Here we determined the global transcriptional responses of astrocytes and microglia to the IFN-I, IFN-alpha. MGCs were prepared from 2–4 day-old C57BL/6 mice. Purified primary astrocytes were obtained from the MGCs by magnetic activated cell sorting using anti-CD11b beads. Microglia were obtained from mixed glial cell cultures by mechanical shaking for 4 h. After treating astrocytes and microglia with IFN-alpha for 12 h, microarray using Affymetrix mouse genome array 430 2.0 array was performed on total RNA extracted from these cells. We found that under basal conditions, each cell type has a unique gene expression pattern reflective of its developmental origin and biological function. Following stimulation with IFN-alpha for 12 h, astrocytes and microglia also displayed a common core response that was characterized by the increased expression of genes required for pathogen detection and elimination. Microglia had a more extensive and diverse response to IFN-alpha with twice the number of genes upregulated (282 vs. 141 genes) when compared with astrocytes. Validation of the findings in vivo further suggested that astrocytes and microglia play important but distinct roles in the development of IFN-alpha-driven cerebral interferonopathies.