Simultaneous transcriptional and epigenomic profiling from specific cell types within heterogeneous tissues in vivo
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ABSTRACT: This study introduces “NuTRAP”, a transgenic mouse that allows simultaneous isolation of cell type-specific translating mRNA and chromatin from complex tissues Using NuTRAP, we successfully characterize gene expression and epigenomic states of various adipocyte populations in vivo, To demonstrate general usefulness, we chateraterize histone states of in vivo hepatocytes.
Project description:Epigenomic mechanisms direct distinct gene expression programs for different cell types. Various in vivo tissues have been subjected to epigenomic analysis; however, these studies have been limited by cellular heterogeneity, resulting in composite gene expression and epigenomic profiles. Here, we introduce "NuTRAP," a transgenic mouse that allows simultaneous isolation of cell-type-specific translating mRNA and chromatin from complex tissues. Using NuTRAP, we successfully characterize gene expression and epigenomic states of various adipocyte populations in vivo, revealing significant differences compared to either whole adipose tissue or in vitro adipocyte cell lines. We find that chromatin immunoprecipitation sequencing (ChIP-seq) using NuTRAP is highly efficient, scalable, and robust with even limited cell input. We further demonstrate the general utility of NuTRAP by analyzing hepatocyte-specific epigenomic states. The NuTRAP mouse is a resource that provides a powerful system for cell-type-specific gene expression and epigenomic profiling.
Project description:Studies of neuroepigenetic mechanisms in health and disease are hindered by a lack of approaches to analyze both the transcriptome and epigenome of specific cell types isolated from the complex milieu of the CNS. Cell isolation by cell surface markers is complicated by preparation artifacts, changes in markers with experimental conditions, and lack of specific markers. This study validates a Nuclear Tagging and Translating Ribosome Affinity Purification (NuTRAP) approach with tamoxifen (Tam) inducible cell-type specific cre recombination to allow the parallel interrogation of the epigenome and the transcriptome in astrocytes (Aldh1l1-creERT2) or microglia (Cx3cr1-creERT2). The recombined NuTRAP construct labels, in a cell-type specific manner, nuclei (RanGAP1) with biotin and mCherry, and the ribosomes (L10a) with EGFP, enabling INTACT isolation of DNA and TRAP isolation of RNA. Validation experiments by flow cytometry and imaging demonstrate cell-type specific induction of the NuTRAP construct. Transcriptomic studies demonstrate isolation of highly enriched RNA by TRAP and oxidative bisulfite studies of INTACT-isolated DNA demonstrate differential DNA modification patterns in microglia and astrocytes. LPS administration in Cx3cr1 NuTRAP mice demonstrates that microglia-specific transcriptome and epigenome changes are revealed that cannot be detected with tissue-level samples. These experiments demonstrate that the NuTRAP approach can be applied to CNS cell populations and that INTACT approaches can be used to study DNA modifications. These results also provide an approach for generation and validation of NuTRAP neuroscience models crossed to any relevant cell-type specific cre line.
Project description:Studies of neuroepigenetic mechanisms in health and disease are hindered by a lack of approaches to analyze both the transcriptome and epigenome of specific cell types isolated from the complex milieu of the CNS. Cell isolation by cell surface markers is complicated by preparation artifacts, changes in markers with experimental conditions, and lack of specific markers. This study validates a Nuclear Tagging and Translating Ribosome Affinity Purification (NuTRAP) approach with tamoxifen (Tam) inducible cell-type specific cre recombination to allow the parallel interrogation of the epigenome and the transcriptome in astrocytes (Aldh1l1-creERT2) or microglia (Cx3cr1-creERT2). The recombined NuTRAP construct labels, in a cell-type specific manner, nuclei (RanGAP1) with biotin and mCherry, and the ribosomes (L10a) with EGFP, enabling INTACT isolation of DNA and TRAP isolation of RNA. Validation experiments by flow cytometry and imaging demonstrate cell-type specific induction of the NuTRAP construct. Transcriptomic studies demonstrate isolation of highly enriched RNA by TRAP and oxidative bisulfite studies of INTACT-isolated DNA demonstrate differential DNA modification patterns in microglia and astrocytes. LPS administration in Cx3cr1 NuTRAP mice demonstrates that microglia-specific transcriptome and epigenome changes are revealed that cannot be detected with tissue-level samples. These experiments demonstrate that the NuTRAP approach can be applied to CNS cell populations and that INTACT approaches can be used to study DNA modifications. These results also provide an approach for generation and validation of NuTRAP neuroscience models crossed to any relevant cell-type specific cre line.
Project description:Studies of neuroepigenetic mechanisms in health and disease are hindered by a lack of approaches to analyze both the transcriptome and epigenome of specific cell types isolated from the complex milieu of the CNS. Cell isolation by cell surface markers is complicated by preparation artifacts, changes in markers with experimental conditions, and lack of specific markers. This study validates a Nuclear Tagging and Translating Ribosome Affinity Purification (NuTRAP) approach with tamoxifen (Tam) inducible cell-type specific cre recombination to allow the parallel interrogation of the epigenome and the transcriptome in astrocytes (Aldh1l1-creERT2) or microglia (Cx3cr1-creERT2). The recombined NuTRAP construct labels, in a cell-type specific manner, nuclei (RanGAP1) with biotin and mCherry, and the ribosomes (L10a) with EGFP, enabling INTACT isolation of DNA and TRAP isolation of RNA. Validation experiments by flow cytometry and imaging demonstrate cell-type specific induction of the NuTRAP construct. Transcriptomic studies demonstrate isolation of highly enriched RNA by TRAP and oxidative bisulfite studies of INTACT-isolated DNA demonstrate differential DNA modification patterns in microglia and astrocytes. LPS administration in Cx3cr1 NuTRAP mice demonstrates that microglia-specific transcriptome and epigenome changes are revealed that cannot be detected with tissue-level samples. These experiments demonstrate that the NuTRAP approach can be applied to CNS cell populations and that INTACT approaches can be used to study DNA modifications. These results also provide an approach for generation and validation of NuTRAP neuroscience models crossed to any relevant cell-type specific cre line.
Project description:Studies of neuroepigenetic mechanisms in health and disease are hindered by a lack of approaches to analyze both the transcriptome and epigenome of specific cell types isolated from the complex milieu of the CNS. Cell isolation by cell surface markers is complicated by preparation artifacts, changes in markers with experimental conditions, and lack of specific markers. This study validates a Nuclear Tagging and Translating Ribosome Affinity Purification (NuTRAP) approach with tamoxifen (Tam) inducible cell-type specific cre recombination to allow the parallel interrogation of the epigenome and the transcriptome in astrocytes (Aldh1l1-creERT2) or microglia (Cx3cr1-creERT2). The recombined NuTRAP construct labels, in a cell-type specific manner, nuclei (RanGAP1) with biotin and mCherry, and the ribosomes (L10a) with EGFP, enabling INTACT isolation of DNA and TRAP isolation of RNA. Validation experiments by flow cytometry and imaging demonstrate cell-type specific induction of the NuTRAP construct. Transcriptomic studies demonstrate isolation of highly enriched RNA by TRAP and oxidative bisulfite studies of INTACT-isolated DNA demonstrate differential DNA modification patterns in microglia and astrocytes. LPS administration in Cx3cr1 NuTRAP mice demonstrates that microglia-specific transcriptome and epigenome changes are revealed that cannot be detected with tissue-level samples. These experiments demonstrate that the NuTRAP approach can be applied to CNS cell populations and that INTACT approaches can be used to study DNA modifications. These results also provide an approach for generation and validation of NuTRAP neuroscience models crossed to any relevant cell-type specific cre line.
Project description:Aerobic exercise is well known to promote neuroplasticity and hippocampal memory. In the developing brain, early-life exercise (ELE) can lead to lasting improvements in hippocampal function, yet molecular mechanisms underlying this phenomenon have not been fully explored. In this study, adolescent transgenic mice harboring the “NuTRAP” (Nuclear tagging and Translating Ribosome Affinity Purification) cassette in Emx1 expressing neurons (“Emx1-NuTRAP” mice) undergo ELE followed by a hippocampal learning task, in order to determine the molecular underpinnings of exercise contributing to improved hippocampal memory performance. We simultaneously isolate and sequence translating mRNA and nuclear chromatin from a single hippocampus in a cell-type specific manner (excitatory neurons), demonstrate validity of our new technical approach, and couple multi-omics sequencing data to evaluate histone modifications H4K8ac and H3K27me3 and their influence on gene expression after ELE. We then evaluate new gene expression – histone modification relationships specifically during hippocampal memory consolidation that may play a critical role in facilitated memory after ELE. Our data reveal novel candidate gene-histone modification interactions and implicate gene regulatory pathways involved in ELE’s impact on hippocampal learning and memory.
Project description:Aerobic exercise is well known to promote neuroplasticity and hippocampal memory. In the developing brain, early-life exercise (ELE) can lead to lasting improvements in hippocampal function, yet molecular mechanisms underlying this phenomenon have not been fully explored. In this study, adolescent transgenic mice harboring the “NuTRAP” (Nuclear tagging and Translating Ribosome Affinity Purification) cassette in Emx1 expressing neurons (“Emx1-NuTRAP” mice) undergo ELE followed by a hippocampal learning task, in order to determine the molecular underpinnings of exercise contributing to improved hippocampal memory performance. We simultaneously isolate and sequence translating mRNA and nuclear chromatin from a single hippocampus in a cell-type specific manner (excitatory neurons), demonstrate validity of our new technical approach, and couple multi-omics sequencing data to evaluate histone modifications H4K8ac and H3K27me3 and their influence on gene expression after ELE. We then evaluate new gene expression – histone modification relationships specifically during hippocampal memory consolidation that may play a critical role in facilitated memory after ELE. Our data reveal novel candidate gene-histone modification interactions and implicate gene regulatory pathways involved in ELE’s impact on hippocampal learning and memory.
Project description:The interspersed anatomic distribution of endothelial cells (ECs) and their dependence on microenvironmental cues have been major challenges in studying EC function and response to (patho)physiological stimuli in vivo. Combining EC-specific translating ribosome affinity purification (EC-TRAP) with RNA sequencing provides an accurate in vivo snapshot of tissue-specific EC expression profiles, and maintains a high degree of sensitivity to detect low abundant transcripts while limiting changes in gene expression profiles due to enzymatic tissue dissociation required to generate single cell suspensions for FACS sorting or single cell analysis. In vitro HUVEC data was obtained to ensure short-term cycloheximide treatment, as used for in vivo experiments, did not alter global gene expression.
Project description:The interspersed anatomic distribution of endothelial cells (ECs) and their dependence on microenvironmental cues have been major challenges in studying EC function and response to (patho)physiological stimuli in vivo. Combining EC-specific translating ribosome affinity purification (EC-TRAP) with RNA sequencing provides an accurate in vivo snapshot of tissue-specific EC expression profiles, and maintains a high degree of sensitivity to detect low abundant transcripts while limiting changes in gene expression profiles due to enzymatic tissue dissociation required to generate single cell suspensions for FACS sorting or single cell analysis. In addition to demonstrating EC heterogeneity under physiologic conditions, the in vivo host response to lipopolysaccharide (LPS) revealed the induction of expression programs associated with a native defense response, with marked differences across vascular beds.
Project description:Epigenetic regulation of the genome through DNA modifications, mainly methylcytosine (mC) and hydroxymethylcytosine (hmC), alters DNA accessibility, genomic organization and gene expression and is thought to be altered during neurodegenerative diseases, such as age-related macular degeneration (AMD). Analysis of retina epigenetic and transcriptomic signatures at the cell-type specific level is crucial to understanding the pathophysiology of retinal degeneration. We have discovered that Aldh1l1 is specifically expressed in the major macroglia of the retina, the Müller glia, and, unlike the brain, is not expressed in retinal astrocytes. This allows a novel model to study paired epigenetic and transcriptomic signatures in Müller glia using Nuclear Tagging and Translating Ribosome Affinity Purification (NuTRAP) for temporally controlled labeling and isolation of Müller glial DNA and RNA. As validated through a variety of approaches, the Aldh1l1cre/ERT2-NuTRAP model provides Müller glia specific translatome and epigenome profiles. Application of this approach to models of acute injury (optic nerve crush) and chronic stress (aging) uncovered common Müller glia-specific transcriptome changes in inflammatory pathways, as well as differential signatures for each stimulus. The expression of components of the IL1b signalling axis, complement system, and markers of gliosis was enhanced in Müller glia in response to optic nerve crush but not in response to aging. The expression of components of the purinergic receptor and focal adhesion signalling pathways changed uniquely in response to aging but not with optic nerve crush. The Aldh1l1cre/ERT2-NuTRAP model allows focusing molecular analyses to a single, minority cell type within the retina, providing more substantial effect sizes than whole tissue analyses. The NuTRAP model, nucleic acid isolation, and validation approaches presented here can be applied to any retina cell type for which a cell type-specific cre is available.