Project description:In the immune system HDAC7 is expressed in T cells where it regulates the expression of key genes for T cell development and function. Here we report that HDAC7 is also highly expressed in B cell precursors, where it is recruited by MEF2C to repress the activity of key genes for myeloid cell function. While HDAC7 is down-regulated during the conversion of pre-B cells into macrophages, re-expression of HDAC7 interferes with both the acquisition of the myeloid gene transcriptional program and macrophage specific cell functions. Thus, HDAC7 is a novel transcriptional repressor of lineage inappropriate genes in B cells.
Project description:Tet2 is an enzyme that hydroxylates methylated cytosines and has been implicated in hematopoietic differentiation and the formation of myeloid malignancies when mutated. An ideal system to study the role of Tet2 in myelopoeisis is C/EBPa induced transdifferentiation of pre-B cells into macrophages, where many myeloid genes become rapidly upregulated. Here we found that C/EBPa binds to upstream regions of Tet2 and that the gene becomes activated. Tet2 knockdowns impaired the upregulation of macrophage markers as well as phagocytic capacity, suggesting that the enzyme is required for both early and late stages of myeloid differentiation. A slightly weaker effect was seen in primary cells with a Tet2 ablation. Expression arrays of transdifferentiating cells with Tet2 knockdowns permitted the identification of a small subset of myeloid genes whose upregulation was blunted. Activation of these target genes was accompanied by a rapid increase of promoter hydroxy-methylation. Our observations indicate that Tet2 helps C/EBPa to rapidly de-repress myeloid genes during the conversion of pre-B cells into macrophages. Gene expression was measured in a control and Tet2kd mouse preB cell line (called Haftl) harboring an inducible form of C/EBPa. Expression was measured in starting cells and cells induced to transdifferentiate into macrophage-like cells for 24 hours. Technical duplicates for each treatment and time were assayed.
Project description:Collombet2016 - Lymphoid and myeloid cell
specification and transdifferentiation
This model is described in the article:
Logical modeling of lymphoid
and myeloid cell specification and transdifferentiation
Samuel Collombet, Chris van Oevelen,
Jose Luis Sardina Ortega, Wassim Abou-Jaoudé, Bruno Di
Stefano, Morgane Thomas-Chollier, Thomas Graf, and Denis
Thieffry
Proceedings of the National Academy of
Sciences of the United States of America
Abstract:
Blood cells are derived from a common set of hematopoietic
stem cells, which differentiate into more specific progenitors
of the myeloid and lymphoid lineages, ultimately leading to
differentiated cells. This developmental process is controlled
by a complex regulatory network involving cytokines and their
receptors, transcription factors, and chromatin remodelers.
Using public data and data from our own molecular genetic
experiments (quantitative PCR, Western blot, EMSA) or
genome-wide assays (RNA-sequencing, ChIP-sequencing), we have
assembled a comprehensive regulatory network encompassing the
main transcription factors and signaling components involved in
myeloid and lymphoid development. Focusing on B-cell and
macrophage development, we defined a qualitative dynamical
model recapitulating cytokine-induced differentiation of common
progenitors, the effect of various reported gene knockdowns,
and the reprogramming of pre-B cells into macrophages induced
by the ectopic expression of specific transcription factors.
The resulting network model can be used as a template for the
integration of new hematopoietic differentiation and
transdifferentiation data to foster our understanding of
lymphoid/myeloid cell-fate decisions.
This model is hosted on
BioModels Database
and identified by:
MODEL1610240000.
To cite BioModels Database, please use:
BioModels Database:
An enhanced, curated and annotated resource for published
quantitative kinetic models.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
Project description:Tet2 is an enzyme that hydroxylates methylated cytosines and has been implicated in hematopoietic differentiation and the formation of myeloid malignancies when mutated. An ideal system to study the role of Tet2 in myelopoeisis is C/EBPa induced transdifferentiation of pre-B cells into macrophages, where many myeloid genes become rapidly upregulated. Here we found that C/EBPa binds to upstream regions of Tet2 and that the gene becomes activated. Tet2 knockdowns impaired the upregulation of macrophage markers as well as phagocytic capacity, suggesting that the enzyme is required for both early and late stages of myeloid differentiation. A slightly weaker effect was seen in primary cells with a Tet2 ablation. Expression arrays of transdifferentiating cells with Tet2 knockdowns permitted the identification of a small subset of myeloid genes whose upregulation was blunted. Activation of these target genes was accompanied by a rapid increase of promoter hydroxy-methylation. Our observations indicate that Tet2 helps C/EBPa to rapidly de-repress myeloid genes during the conversion of pre-B cells into macrophages.
Project description:B lymphocyte development is a complex process tightly controlled at the transcriptional level by the action of networks of transcription factors. The repression of genes from alternative lineages is necessary to ensure the acquisition of the correct B cell identity. However, the mechanisms of transcriptional repression during B cell generation are largely unknown. Here, using a conditional knockout mouse model, we show that the histone deacetylase HDAC7 is essential for B cell development. Early deletion of HDAC7 dramatically blocked B cell development at the pro-B cell stage and gave rise to a severe lymphopenia in peripheral organs. HDAC7-deficient pro-B cells exhibit cell lineage promiscuity, expressing myeloid and T lymphocyte genes. In wild-type B cells HDAC7 is recruited to myocyte enhancer factor 2C (MEFC2) binding sites located at the promoters of macrophage and T lymphocyte genes. Our results demonstrate that HDAC7 is a bona fide transcriptional repressor essential for B cell development.
Project description:Earlier work has shown that pre-B cells can be converted into macrophages by the transcription factor C/EBP? at very high frequencies. Using this system we have now performed a systematic analysis of the question whether during transdifferentiation the cells transiently reactivate progenitor restricted genes or even retrodifferentiate. A transcriptome analysis of transdifferentiating cells showed that most genes are continuously up or downregulated, acquiring a macrophage phenotype within 5 days. In addition, we observed the transient reactivation of a subset of immature myeloid markers, as well as low levels of the progenitor markers Kit and Flt3 and a few lineage inappropriate genes. However, we were unable to observe the re-expression of cell surface marker combinations that characterize hematopoietic stem and progenitor cells (HSPCs), including c-Kit and Flt3. This was the case even when C/EBPalpha was activated in pre-B cells under culture conditions that favor HSPC growth or when the transcription factor was activated in a time limited fashion. Together, our findings are consistent with the notion that the conversion from pre-B cells to macrophages is mostly direct and does not involve overt retrodifferentiation. Our microarray data indicate that most expression changes are direct, and that transdifferentiation does not involve retrodifferentiation. Our data also show that there is a low level transient activation of selected progenitor genes, as well as myeloid precursor genes. Primary mouse pre-B cells were infected with an inducible form of C/EBPa and cells induced to transdifferentiate with beta Estradiol (b-Est) harvested at different time points to analyze expression profiles, using Affymetrix 430.2 arrays.
Project description:Earlier work has shown that pre-B cells can be converted into macrophages by the transcription factor C/EBP? at very high frequencies. Using this system we have now performed a systematic analysis of the question whether during transdifferentiation the cells transiently reactivate progenitor restricted genes or even retrodifferentiate. A transcriptome analysis of transdifferentiating cells showed that most genes are continuously up or downregulated, acquiring a macrophage phenotype within 5 days. In addition, we observed the transient reactivation of a subset of immature myeloid markers, as well as low levels of the progenitor markers Kit and Flt3 and a few lineage inappropriate genes. However, we were unable to observe the re-expression of cell surface marker combinations that characterize hematopoietic stem and progenitor cells (HSPCs), including c-Kit and Flt3. This was the case even when C/EBPalpha was activated in pre-B cells under culture conditions that favor HSPC growth or when the transcription factor was activated in a time limited fashion. Together, our findings are consistent with the notion that the conversion from pre-B cells to macrophages is mostly direct and does not involve overt retrodifferentiation. Our microarray data indicate that most expression changes are direct, and that transdifferentiation does not involve retrodifferentiation. Our data also show that there is a low level transient activation of selected progenitor genes, as well as myeloid precursor genes.
Project description:Histone deacetylase 7 (HDAC7) is highly expressed in CD4+/CD8+ thymocytes and functions as a signal-dependent repressor of gene transcription during T cell development. In this study, we express HDAC7 mutant proteins in a T cell line and use DNA microarrays to identify transcriptional targets of HDAC7 in T cells. Gene expression changes are compared to differential gene expression profiles associated with positive and negative thymic selection. This analysis reveals that HDAC7 regulates an extensive set of genes that are differentially expressed during both positive and negative thymic selection. Many of these genes play important functional roles in positive and negative selection, primarily via coupling between antigen receptor and downstream signaling events. Keywords: microarray gene expression profiling, comparison of perturbation of HDAC7 gene function with differential expression during thymic selection
Project description:Title of Publication: Histone Deacetylase 7 Regulates Cell Survival and TCR Signaling in CD4/CD8 Double-Positive Thymocytes Abstract of publicaton: CD4/CD8 double-positive (DP) thymocytes express the transcriptional repressor Histone Deacetylase 7 (HDAC7), a class IIa HDAC that is exported from the cell nucleus after T cell receptor (TCR) engagement. Through signal-dependent nuclear export, class IIa HDACs such as HDAC7 mediate signal-dependent changes in gene expression that are important to developmental fate decisions in multiple tissues. We report that HDAC7 is exported from the cell nucleus during positive selection in thymocytes, and regulates genes mediating the coupling between TCR engagement and downstream events that determine cell survival. Thymocytes lacking HDAC7 are inefficiently positively selected due to a severely shortened lifespan and exhibit a truncated repertoire of TCR J segments. The expression of multiple important mediators and modulators of the response to TCR engagement is altered in HDAC7-deficient thymocytes, resulting in increased tonic MAP kinase activity that contributes to the observed loss of viability. Remarkably, the activity of Protein Kinase D, the kinase that mediates nuclear export of HDAC7 in response to TCR signaling, is also increased in HDAC7-deficient thymocytes, suggesting that HDAC7 nuclear export governs a self-sustaining auto-excitatory loop. These experiments add to the understanding of the life/death decision in thymic T cell development, define a novel function for class IIa HDACs, and point to a novel feed-forward mechanism whereby these molecules regulate their own state and mediate stable developmental transitions. Goal of Microarray experiment: We did these experiments to determine how alteration of the function of HDAC7, a site-specific and signal-dependent repressor of transcription, changes gene expression in CD4/CD8 DP thymocytes. Three biological replicate samples were prepared for each non-wild type mouse strain (Samples 7-18). Six biological replicates were prepared for the wild type strain (Samples 1-6). Total RNA was prepared from isolated CD4/CD8 Double-positive thymocytes and labeled with the Affymetrix Whole-Transcript labeling protocol. Labeled probes were hybridized to one Affymetrix Mouse Gene 1.0ST array each. Data from .cel files were normalized using RMA, in normalization groups representing each of the binary comparisons made. These binary comparisons between sample groups represent gene expression changes due to loss of HDAC7 (samples 1-3 vs. 7-9), transgenic expression of an HDAC7-VP16 fusion protein (samples 4-6 vs. 10-12), positive thymic selection (samples 1-6 vs. samples 11-15), and negative thymic selection (Samples 11-15 vs. samples 16-18).
Project description:The present study reports an unbiased analysis of the cytotoxic T cell serine-threonine phosphoproteome using high resolution mass spectrometry. Approximately 2,000 phosphorylations were identified in CTLs of which approximately 450 were controlled by TCR signaling. A significantly overrepresented group of molecules identified in the phosphoproteomic screen were transcription activators, co-repressors and chromatin regulators. A focus on the chromatin regulators revealed that CTLs have high expression of the histone deacetylase HDAC7 but continually phosphorylate and export this transcriptional repressor from the nucleus. HDAC7 dephosphorylation results in its nuclear accumulation and suppressed expression of genes encoding key cytokines, cytokine receptors and adhesion molecules that determine CTL function. The screening of the CTL phosphoproteome thus reveals intrinsic pathways of serine-threonine phosphorylation that target chromatin regulators in CTLs and determine the CTL functional program. We used Affymetrix microarray analysis to explore the molecular basis for the role of HDAC7 in CTLs and the impact of GFP-HDAC7 phosphorylation deficient mutant expression on the CTL transcriptional profile. In vitro generated P14 TCR cytotoxic T cells were retrovirally infected with a construct encoding GFP-HDAC7 phosphorylation deficient mutant, sorted in base of GFP expression (GFP positive and GFP negative) and processed for microarray analysis in three biological replicas.