Project description:Development of type 1 conventional dendritic cells (cDC1) underlies the capacity to generate antiviral and antitumor immune responses. Here, we identify the basis for cDC1 development from its earliest progenitors, determining the hierarchy of several required transcription factors and uncovering a novel paradigm for superenhancer function. We produced in vivo mutations of two C/EBP binding sites that comprise the Irf8 +56 kb enhancer that abrogate IRF8 expression in all myeloid progenitors and impair cDC1 development. These sites do not bind RUNX1 or RUNX3, and C/EBPα expression instead is regulated by their action at the Cebpa +37 kb enhancer, placing RUNX factors upstream of Cepba in regulating Irf8. Finally, we demonstrate that cis interactions between the +56 kb Irf8 enhancer and the previously reported +41 kb and +32 kb Irf8 enhancers are mandatory in the sequential progression of these stage specific constituent elements.
Project description:To understand the mechanism underlying monocyte and dendritic cell development through the regulation of Irf8 expression by the 56 kb downstream (+56 kb) Irf8 enhancer, we performed epigenetic profiling of bone marrow cells and splenocytes from wild-type, the Irf8 +56 kb enhancer-deficient, and IRF8-deficient mice. Taken together with the transcriptome analysis of mononuclear phagocyte lineage cells in these mice, the Irf8 +56 kb enhancer-mediated high Irf8 expression in hematopoietic progenitor cells promote type 1 classical dendritic cell (cDC1) differentiation, while low Irf8 expression in progenitors led to Ly6C+ monocyte development. In addition, IRF8 ChIP-seq of mature cDC1s and monocytes suggested that IRF8 regulates enhancers in cooperation with different transcription factors in each lineage in its expression level.
Project description:Type 1 classical dendritic cells (cDC1s) development requires the transcription factor IRF8, and IRF8 mutations cause severe combined immunodeficiency, including disseminated bacille Calmette-Guérin (BCG) disease. IRF8 regulated enhancers are required for Irf8 expression in early DC progenitors and mature cDC1s. The E-protein-dependent +41 kb enhancer gains accessibility and activates transcription in common DC progenitors (CDPs), and its depletion abrogated pre-cDC1s specification. The Batf3-dependent +32 kb enhancer gains accessibility and activates transcription in pre-cDC1 progenitors, and its depletion impaired cDC1 maturation. The +32 kb Irf8 enhancer locus bears an enhancer transcript, and the production of enhancer RNA (eRNA) Gm39266 is dependent on +41 kb Irf8 enhancer. It was unclear whether the +32 kb and +41 kb enhancers act independently or cooperate to regulate Irf8 expression. We dissected the mechanisms using +32/+41 compound heterozygous mice, and found that while the +41 kb enhancer suffices for pre-cDC1 progenitor specification, the +32 kb and +41 kb enhancers must reside on one allele to support cDC1 maturation. The +41 kb enhancer cis-regulates chromatin accessibility and BATF3 binding at +32 kb enhancer, independent of eRNA Gm39266 transcripts or transcription across +32 kb Irf8 enhancer.
Project description:Type 1 classical dendritic cells (cDC1s) development requires the transcription factor IRF8, and IRF8 mutations cause severe combined immunodeficiency, including disseminated bacille Calmette-Guérin (BCG) disease. IRF8 regulated enhancers are required for Irf8 expression in early DC progenitors and mature cDC1s. The E-protein-dependent +41 kb enhancer gains accessibility and activates transcription in common DC progenitors (CDPs), and its depletion abrogated pre-cDC1s specification. The Batf3-dependent +32 kb enhancer gains accessibility and activates transcription in pre-cDC1 progenitors, and its depletion impaired cDC1 maturation. The +32 kb Irf8 enhancer locus bears an enhancer transcript, and the production of enhancer RNA (eRNA) Gm39266 is dependent on +41 kb Irf8 enhancer. It was unclear whether the +32 kb and +41 kb enhancers act independently or cooperate to regulate Irf8 expression. We dissected the mechanisms using +32/+41 compound heterozygous mice, and found that while the +41 kb enhancer suffices for pre-cDC1 progenitor specification, the +32 kb and +41 kb enhancers must reside on one allele to support cDC1 maturation. The +41 kb enhancer cis-regulates chromatin accessibility and BATF3 binding at +32 kb enhancer, independent of eRNA Gm39266 transcripts or transcription across +32 kb Irf8 enhancer.
Project description:To understand the mechanism underlying monocyte and dendritic cell development through the regulation of Irf8 expression by the 56 kb downstream (+56 kb) Irf8 enhancer, we performed transcriptome analysis of bone marrow cells and splenocytes from wild-type, the Irf8 +56 kb enhancer-deficient, and IRF8-deficient mice. Taken together with the epigenetic profiling of mononuclear phagocyte lineage cells in these mice, the Irf8 +56 kb enhancer-mediated high Irf8 expression in hematopoietic progenitor cells promote type 1 classical dendritic cell (cDC1) differentiation, while low Irf8 expression in progenitors led to Ly6C+ monocyte development.
Project description:Autoactivation of lineage-determining transcription factors (TFs) mediates bistable expression to generate distinct cell phenotypes essential for complex body plans. Classical dendritic cells type 1 (cDC1) and type 2 (cDC2) provide non-redundant functions required for defense against distinct immune challenges. Interferon Regulatory Factor 8 (IRF8), the cDC1 lineage-determining TF, undergoes autoactivation in cDC1 progenitors to establish cDC1 identity, yet its expression is downregulated during cDC2 differentiation by an unknown mechanism. This study reveals that the Irf8 +32 kb enhancer, responsible for IRF8 autoactivation, has been tuned to possess low-affinity IRF8 binding sites. Incorporation of multiple high-affinity IRF8 binding sites into the Irf8 +32 kb enhancer induces erroneous IRF8 autoactivation in specified cDC2 progenitors, causing their redirection towards cDC1 and a novel hybrid DC subset with mixed lineage phenotypes. These developmental alterations critically impair both cDC1- and cDC2-dependent arms of immunity. Collectively, our findings underscore the significance of enhancer suboptimization in the developmental segregation of classical dendritic cells required for normal immune function.
Project description:To understand the mechanism underlying monocyte and dendritic cell development through the regulation of Irf8 expression by the 56 kb downstream (+56 kb) Irf8 enhancer, we analyzed chromatin accessibility of bone marrow cells from wild-type and Irf8-/- mice. Combined with the epigenetic profiling by H3K27 acetylation ChIP-seq, the +56 kb enhancer opens at LMPP stage, and gets activated at its highest level in mononuclear phagocyte lineage progenitor cells.
Project description:Autoactivation of lineage-determining transcription factors (TFs) mediates bistable expression to generate distinct cell phenotypes essential for complex body plans. Classical dendritic cells type 1 (cDC1) and type 2 (cDC2) provide non-redundant functions required for defense against distinct immune challenges. Interferon Regulatory Factor 8 (IRF8), the cDC1 lineage-determining TF, undergoes autoactivation in cDC1 progenitors to establish cDC1 identity, yet its expression is downregulated during cDC2 differentiation by an unknown mechanism. This study reveals that the Irf8 +32 kb enhancer, responsible for IRF8 autoactivation, has been tuned to possess low-affinity IRF8 binding sites. Increasing these affinities in vivo induces erroneous IRF8 autoactivation in specified cDC2 progenitors, causing their redirection towards cDC1 and a novel hybrid DC subset with mixed lineage phenotypes. These developmental alterations critically impair both cDC1- and cDC2-dependent arms of immunity. Collectively, our findings underscore the significance of enhancer suboptimization in the developmental segregation of classical dendritic cells required for normal immune function.
Project description:To understand the roles of Irf8 3’ enhancers on Irf8 expression during cDC1 differentiation, we performed RNA-seq analysis of bone marrow cells and splenocytes from wild-type, and the Irf8 enhancer-deficient mice. Phenotypic analysis and integrated analysis of transcriptome data with genome-wide CUT&Tag data analysis for H3K27ac revealed that the +56 kb enhancer acts on other 3′ enhancers via an IRF8-dependent TF program and the +32 kb enhancer acts in cis to activate other 3′ enhancers.
Project description:To understand the roles of Irf8 3’ enhancers on Irf8 expression during cDC1 differentiation, we performed Cleavage Under Targets and Tagmentation (CUT&Tag) analysis for H3K27ac of bone marrow cells and splenocytes from wild-type, and the Irf8 enhancer-deficient mice. Phenotypic analysis and integrated analysis of CUT&Tag data with transcriptome data of these mouse mononuclear phagocytic lineage cells revealed that the +56 kb enhancer acts on other 3′ enhancers via an IRF8-dependent TF program and the +32 kb enhancer acts in cis to activate other 3′ enhancers.