Project description:Although classified as hematopoietic cells, tissue-resident macrophages are selfrenewing and maintained independently of adult hematopoiesis. While most macrophages originate from embryonic precursors that seed tissues prior to birth, their exact origin is unknown. Using an in utero macrophage depletion strategy and fatemapping of yolk sac (YS) and fetal liver (FL) hematopoiesis, we found that YS macrophages are the main precursors of microglia, while most other macrophages derive from fetal monocytes. Both YS macrophages and fetal monocytes arise from erythro-myeloid progenitors (EMP) generated in the YS. In the YS, EMP gave rise to macrophages without monocytic intermediates, while EMP seeding the FL upon the establishment of blood circulation acquired c-Myb expression and gave rise to fetal monocytes that then seed embryonic tissues to differentiate into macrophages. Thus, adult tissue-resident macrophages established from HSC-independent embryonic precursors arise from two different developmental programs. 12 samples of progenitors, monocytes or macrophages are analyzed from 2 to 4 replicate. Each replicate derived from at least 5 embryos or adult mice
Project description:Although classified as hematopoietic cells, tissue-resident macrophages are selfrenewing and maintained independently of adult hematopoiesis. While most macrophages originate from embryonic precursors that seed tissues prior to birth, their exact origin is unknown. Using an in utero macrophage depletion strategy and fatemapping of yolk sac (YS) and fetal liver (FL) hematopoiesis, we found that YS macrophages are the main precursors of microglia, while most other macrophages derive from fetal monocytes. Both YS macrophages and fetal monocytes arise from erythro-myeloid progenitors (EMP) generated in the YS. In the YS, EMP gave rise to macrophages without monocytic intermediates, while EMP seeding the FL upon the establishment of blood circulation acquired c-Myb expression and gave rise to fetal monocytes that then seed embryonic tissues to differentiate into macrophages. Thus, adult tissue-resident macrophages established from HSC-independent embryonic precursors arise from two different developmental programs.
Project description:Tissue-resident macrophages can derive from yolk sac macrophages, fetal liver monocytes or adult bone marrow monocytes. Whether these precursors can give rise to transcriptionally identical alveolar macrophages is unknown. Here, we transferred traceable yolk sac macrophages, fetal liver monocytes, adult bone marrow monocytes or adult alveolar macrophages as a control, into the empty alveolar macrophage niche of neonatal Csf2rb-/- mice. All precursors efficiently colonized the alveolar niche and generated alveolar macrophages that were transcriptionally almost identical, with only 22 genes that could be linked to their origin. Underlining the physiological relevance of our findings, all transfer-derived alveolar macrophages self-maintained within the lungs for up to 1 year and durably prevented alveolar proteinosis. Thus, precursor origin does not affect the development of functional self-maintaining tissue-resident macrophages.
Project description:Tissue-resident macrophages can derive from yolk sac macrophages, fetal liver monocytes or adult bone marrow monocytes. Whether these precursors can give rise to transcriptionally identical alveolar macrophages is unknown. Here, we transferred traceable yolk sac macrophages, fetal liver monocytes, adult bone marrow monocytes or adult alveolar macrophages as a control, into the empty alveolar macrophage niche of neonatal Csf2rb-/- mice. All precursors efficiently colonized the alveolar niche and generated alveolar macrophages that were transcriptionally almost identical, with only 22 genes that could be linked to their origin. Underlining the physiological relevance of our findings, all transfer-derived alveolar macrophages self-maintained within the lungs for up to 1 year and durably prevented alveolar proteinosis. Thus, precursor origin does not affect the development of functional self-maintaining tissue-resident macrophages. CD45.1+CD45.2+ yolk sac macrophages, fetal liver monocytes, adult bone marrow monocytes or adult alveolar macrophages from the bronchoalveolar lavage were sorted from wild type CD45.1+CD45.2+ mice of indicated ages. From part of these samples RNA was isolated. The other part was transferred intranasally into the lungs of neonate Csf2rb-/- mice. 6 weeks post-transfer, transfer-derived CD45.1+CD45.2+ alveolar macrophages were sorted from the bronchoalveolar lavage. Wild type CD45.1+CD45.2 alveolar macrophages from the bronchoalveolar lavage of 6 week old mice were sorted as control. 36 samples (arrays) in total. RNA was isolated, amplified with Nugene pico kit, converted to cDNA and then hybridised on Affymetrix GeneChip Mouse Gene 1.0 ST Arrays.
Project description:Alveolar macrophages (AMs) are lung resident phagocytes. They derive from fetal liver monocytes, which colonize the lung during embryonic development and give rise to fully mature AMs perinatally. We have identified TGF- signaling as an indispensible regulator during this process. To analyze the impact of TGF- on the entire transcriptome of AMs, we performed RNA-seq on AMs deficient of Tgfbr2 in CD11cCre/+ Tgfbr2fl/fl mice at P3 with Tgfbr2fl/fl littermates as a control.
Project description:Self-renewing tissue-resident macrophages are thought to be exclusively derived from embryonic progenitors. However, whether circulating monocytes can also give rise to such macrophages has not been formally investigated. Here we use a new model of diphtheria toxin-mediated depletion of liver-resident Kupffer cells to generate niche availability and show that circulating monocytes engrafted in the liver, gradually adopt the transcriptional profile of their depleted counterparts and become long-lived self-renewing cells. Underlining the physiological relevance of our findings, circulating monocytes also contribute to the expanding pool of macrophages in the liver shortly after birth, when macrophage niches become available during normal organ growth. Thus, like embryonic precursors, monocytes can and do give rise to self-renewing tissue-resident macrophages if the niche is available to them. Clec4F+ Kupffer cells were isolated and sorted from livers from adult WT mice or KC-DTR or KC-DTR littermate control mice +/- 50ng DT at indicated timepoints. 19 samples (arrays) in total. RNA was isolated, amplified with Nugene pico kit, converted to cDNA and then hybridised on Affymetrix GeneChip Mouse Gene 1.0 ST Arrays.
Project description:Self-renewing tissue-resident macrophages are thought to be exclusively derived from embryonic progenitors. However, whether circulating monocytes can also give rise to such macrophages has not been formally investigated. Here we use a new model of diphtheria toxin-mediated depletion of liver-resident Kupffer cells to generate niche availability and show that circulating monocytes engrafted in the liver, gradually adopt the transcriptional profile of their depleted counterparts and become long-lived self-renewing cells. Underlining the physiological relevance of our findings, circulating monocytes also contribute to the expanding pool of macrophages in the liver shortly after birth, when macrophage niches become available during normal organ growth. Thus, like embryonic precursors, monocytes can and do give rise to self-renewing tissue-resident macrophages if the niche is available to them.
Project description:The earliest macrophages are generated during embryonic development from erythro-myeloid progenitors (EMPs) via primitive haematopoiesis. This process is poorly understood in humans and in the mouse is thought to be spatially restricted to the yolk sac. Human fetal placental macrophages, Hofbauer cells (HBC), arise during the primitive haematopoietic wave at ~18 days post conception. Here we identify a population of placental erythro-myeloid progenitors (PEMPs) in the early human placenta that give rise to HBC. PEMP are fetal CD34+CD43+ progenitors found exclusively at early gestational timepoints. Transcriptomic analyses reveal that PEMP have conserved features of primitive yolk sac EMPs, including the lack of HLF expression. Using in vitro single-cell culture experiments we show that PEMP generate HBC-like cells that completely lack HLA-DR expression and demonstrate that this is a conserved feature of all macrophages generated by primitive haematopoiesis in humans. Finally, we demonstrate that the class II transactivator, CTIIA, the master regulator HLA-DR expression, is epigenetically silenced during primitive haematopoiesis, leading to HLA-DRneg macrophages. These findings demonstrate that HBC are derived locally from PEMP and establish the human placenta as an additional site of primitive haematopoiesis.
Project description:Tissue-resident macrophages such as microglia, Kupffer and Langerhans cells derive from Myb-independent yolk sac (YS) progenitors generated before the emergence of hematopoietic stem cells (HSCs). Myb-independent YS-derived resident macrophages self-renew locally, independently of circulating monocytes and HSCs. In contrast, adult blood monocytes as well as infiltrating, gut and dermal macrophages derive from Myb-dependent HSCs. These findings are derived from the mouse, using gene knock-outs and lineage tracing, but their applicability to human development has not been formally demonstrated. Here we use human induced pluripotent stem cells (iPSCs) as a tool to model human hematopoietic development. By using a CRISPR-Cas9 knock-out strategy we show that human iPSC-derived monocytes/macrophages develop in a MYB-independent, RUNX1 and SPI1 (PU.1)-dependent fashion. This result makes human iPSC-derived macrophages developmentally related to and a good model for MYB-independent tissue-resident macrophages such as alveolar and kidney macrophages, microglia, Kupffer and Langerhans cells.
Project description:Tissue resident macrophages are functionally diverse cells that share an embryonic mesodermal origin. However, the mechanism(s) that control their specification remain unclear. We performed transcriptional, molecular and in situ spatio-temporal analyses of macrophage development in mice. We report that Erythro-Myeloid Progenitors generate pre-macrophages (pMacs) that simultaneously colonize the head and caudal embryo from embryonic day (E)9.5 in a chemokine-receptor dependent manner, to further differentiate into tissue F4/80+ macrophages. The core macrophage transcriptional program initiated in pMacs, is rapidly diversified in early macrophages as expression of transcriptional regulators becomes tissue-specific. For example, the preferential expression of the transcriptional regulator Id3 initiated in early fetal liver macrophages appears critical for Kupffer cell differentiation, as inactivation of Id3 causes a selective Kupffer cell deficiency that persists in adults. We propose that colonization of developing tissues by differentiating macrophages is immediately followed by their specification as they establish residence, hereby generating the macrophage diversity observed in post-natal tissues. RNA-sequencing of ID3+/- and ID3-/- Kupffer cells