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: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:We performed a single-cell transcriptomic analysis of monocyte and monocyte progenitors by single-cell mRNA sequencing (scRNA-seq) using the C1 Fluidigm platform. We sorted BM cMoPs (Lin−CD117+CD115+CD135−Ly6C+), BM Ly6C+ monocytes (Lin−CD117-CD115+CD135−Ly6C+) and blood Ly6Chi monocytes (CD115+CD11b+Ly6Chi) from wild-type (WT) C57BL/6 mice by fluorescence-activated cell sorting (FACS) and generated transcriptional profiles for each individual cell (n = 38 for blood Ly6Chi monocytes, n = 66 for BM cMoPs, n = 57 for BM Ly6C+ monocytes).
Project description:Ly6C+ ‘classical’ monocytes respond rapidly to inflammation, either directly as effector cells or by differentiating into inflammatory macrophages and dendritic cells (DC). In the absence of DC, elevated levels of serum Flt3L and G-CSF induce a monocytosis although the properties of this expanded population have not been addressed. Here, we show that depletion of DC using the CD11c-DTR model results in rapid and CCR2-independent expansion of a variant population of splenic MHC Class II+ CD64+ Ly6C+ monocytes that are distinct from both circulating blood Ly6C+ monocytes and their tissue counterparts, but resemble Ly6C+ cells mobilized by exogenous G-CSF and Flt3L. The CD64+ Ly6C+ monocyte population is characterized by up-regulation of TLR signalling apparatus and an increased capacity to produce TNF-a following stimulation. Therefore, perturbation within the mononuclear phagocytic system in the absence of inflammation induces an alternative differentiation pathway that drives expansion of monocytes poised for innate immune activation. Monocytes populations were purified from CD11c-DTR mice which were injected with PBS or diphtheria toxin 48 hours previously. Common monocyte progenitors (cMoP) were isolated from untreated C57BL/6 mice. 48 hours after injection of PBS or DT, monocytes were purified from the spleen after collagenase digestion and flow sorted directly into Qiagen RLT buffer. cMoP were purified directly from the bone marrow without digestion enzymes.
Project description:In mice, two restricted DC progenitors, macrophage-dendritic progenitor (MDP) and common dendritic cell progenitor (CDP) demonstrate increasing commitment of DC lineage as they sequentially lose granulocyte and monocyte potential respectively. Identifying these progenitors has enabled understanding of the role of DCs and monocytes in immunity and tolerance in mice. In humans, however, restricted monocyte and DC progenitors remain unknown. Progress in studying human DC development has been hampered by lack of an in vitro culture system that recapitulates in vivo DC hematopoiesis. Here we report a culture system that supports development of CD34+ hematopoietic stem cell progenitors into the three major human DC subsets, monocytes, granulocytes, NK and B cells. Using this culture system we defined the pathway for human DC development, and revealed the sequential origin of human DCs from increasingly restricted progenitors: a granulocyte-monocyte-DC progenitor (hGMDP) that develops into a monocyte-DC progenitor (hMDP) that develops into monocytes and a common DC progenitor (hCDP) that is restricted to produce the three major DC subsets. The phenotype of the DC progenitors partially overlaps with granulocyte monocyte progenitors (GMPs). These progenitors reside in human cord blood and bone marrow but not in the blood or lymphoid tissues in the steady state. We performed whole transcriptome expression analysis on monocytes and subsets of dendritic cells i.e. CD1c+ DCs, CD141+ DCs and CD303+ pDCs isolated from blood or differentiated in culture from cord blood CD34+ cells in presence of MS5 stromal cells and Flt3l, GM-CSF and SCF cytokines.
Project description:Granulocyte-monocyte progenitors (GMPs) and monocyte-dendritic cell progenitors (MDPs) produce monocytes during homeostasis and in response to increased demand during infection. Both progenitor populations are thought to derive from common myeloid progenitors (CMPs), and a hierarchical relationship (CMP-GMP-MDP-monocyte) is presumed to underlie monocyte differentiation. Here, however, we demonstrate that mouse MDPs arose from CMPs independently of GMPs, and that GMPs and MDPs produced monocytes via similar, but distinct, monocyte-committed progenitors. GMPs and MDPs yielded classical (Ly6Chi) monocytes with gene expression signatures that were defined by their origins and impacted their function. GMPs produced a subset of “neutrophil-like” monocytes, whereas MDPs gave rise to a subset of monocytes that yielded monocyte-derived dendritic cells. GMPs and MDPs were also independently mobilized to produce specific combinations of myeloid cell types following the injection of microbial components. Thus, the balance of GMP and MDP differentiation shapes the myeloid cell repertoire during homeostasis and following infection.
Project description:Granulocyte-monocyte progenitors (GMPs) and monocyte-dendritic cell progenitors (MDPs) produce monocytes during homeostasis and in response to increased demand during infection. Both progenitor populations are thought to derive from common myeloid progenitors (CMPs), and a hierarchical relationship (CMP-GMP-MDP-monocyte) is presumed to underlie monocyte differentiation. Here, however, we demonstrate that mouse MDPs arose from CMPs independently of GMPs, and that GMPs and MDPs produced monocytes via similar, but distinct, monocyte-committed progenitors. GMPs and MDPs yielded classical (Ly6Chi) monocytes with gene expression signatures that were defined by their origins and impacted their function. GMPs produced a subset of “neutrophil-like” monocytes, whereas MDPs gave rise to a subset of monocytes that yielded monocyte-derived dendritic cells. GMPs and MDPs were also independently mobilized to produce specific combinations of myeloid cell types following the injection of microbial components. Thus, the balance of GMP and MDP differentiation shapes the myeloid cell repertoire during homeostasis and following infection.
Project description:Administration of G-CSF mobilizes a unique population of CD11b+Ly6C+CD34+mature monocytes that can inhibit GVHD in murine models of BMT via an iNOS-dependent mechanism. The transcriptional profiles of flow sorted lineage-CD11b+CD34+ cells from G-CSF treated mice were compared with conventional splenic Ly6C+ and Ly6C- monocytes, progenitor cells and cultured myeloid-derived suppressor cells. Further comparisons were made with lineage-CD11b+CD34+ cells from G-CSF treated mice that had been grown in culture or that were derived from iNOS ko mice. We used microarrays to detail the global programme of gene expression underlying diffrenetiation of each of these cell types Lin-CD11b+CD34+ populations were isolated directly from the spleens of G-CSF-treated C57BL/6 mice or iNOS ko mice. In untreated C57BL/6 mice, Lin-CD11b+CD115+Ly6C+ and Lin-CD11b+CD115+Ly6C- monocytes were isolated from the spleen and Lin-CD117+CD115+CD135-Ly6C+CD11b- common monocyte progenitors were isolated from the bone marrow. Myeloid-derived suppressor cells (Ly6C+CD11b+ cells derived from G-CSF, GM-CSF and IL-13 cultured C57BL/6 bone marrow) were also isolated and compared with the above populations. Lin-CD11b+CD34+ spleen cells derived from G-CSF-treated C57BL/6 mice were cultured for 3 days in Flt3 ligand and SCF and then compared to the original input population.
Project description:Multiple Sclerosis (MS) is characterized by pathological inflammation resulting from recruitment of lymphoid and myeloid immune cells from the blood circulation into the central nervous system (CNS). Due to cellular heterogeneity, defining the functional roles of these subsets in acute and chronic stages of MS has been challenging. Here we used index sorting and transcriptional single-cell sequencing to characterize peripheral mononuclear phagocyte infiltrates in the MS mouse model, experimental autoimmune encephalomyelitis (EAE). Based on their transcriptomes, we identified eight monocyte and three dendritic cell subsets during disease pathology with defined characteristics pointing towards distinct functions. Cell ablation identified two specific monocytic subsets with a pathogenic potential. Congenic monocyte transfer experiments combined with indexed-lineage sorting coupled to scRNA-seq established that these pathogenic cells are not descendants of the canonical Ly6C+ monocytes but derived from early myeloid cell progenitors. These results suggest a potential for targeted therapeutic interventions aimed at blocking specific pathogenic monocytic subsets.