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  • 1
    Publication Date: 2013-03-08
    Description: Monocytes regulate host defenses, inflammation, and tissue homeostasis. The transcription factor interferon regulatory factor-8 (IRF8) stimulates monocyte/macrophage differentiation, yet genome-wide understanding of the differentiation program initiated by IRF8 is lacking. By combining chromatin immunoprecipitation sequencing with gene expression profiling, we show that during IRF8-dependent monocyte differentiation, IRF8 binding occurs at both promoter-proximal and promotor-distal regions together with the transcription factor PU.1 and is associated with gene induction. Many of the promoter-distal IRF8 binding sites show an increase in histone H3 lysine 4 monomethylation, a signature for enhancers. However, about half the IRF8-induced genes were not bound by IRF8, suggesting the involvement of downstream transcription factors. Analysis of DNA motifs in cis -regulatory elements of these indirect IRF8 target genes predicted that Krüppel-like factor-4 (KLF4)—essential for Ly6C + monocyte development—is one such factor. Indeed, monocyte development in Irf8 –/– mice is as defective as that in Klf4 –/– chimeric mice. Moreover, Irf8 –/– monocyte-dendritic cell progenitors do not express Klf4 messenger RNA. Introduction of KLF4 into an Irf8 –/– myeloid progenitor cell line induced a subset of IRF8 target genes and caused partial monocyte differentiation. Taken together, our present results uncover genome-wide behavior of IRF8 and identify an IRF8-KLF4 axis that operates during monocyte differentiation.
    Keywords: Phagocytes, Granulocytes, and Myelopoiesis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 2
    Publication Date: 2015-01-09
    Description: Basophils and mast cells play critical roles in host defense against pathogens and allergic disorders. However, the molecular mechanism by which these cells are generated is not completely understood. Here we demonstrate that interferon regulatory factor-8 (IRF8), a transcription factor essential for the development of several myeloid lineages, also regulates basophil and mast cell development. Irf8 –/– mice displayed a severe reduction in basophil counts, which was accounted for by the absence of pre-basophil and mast cell progenitors (pre-BMPs). Although Irf8 –/– mice retained peripheral tissue mast cells, remaining progenitors from Irf8 –/– mice including granulocyte progenitors (GPs) were unable to efficiently generate either basophils or mast cells, indicating that IRF8 also contributes to the development of mast cells. IRF8 appeared to function at the GP stage, because IRF8 was expressed in GPs, but not in basophils, mast cells, and basophil/mast cell-restricted progenitor cells. Furthermore, we demonstrate that GATA2, a transcription factor known to promote basophil and mast cell differentiation, acts downstream of IRF8. These results shed light on the pathways and mechanism underlying the development of basophils and mast cells.
    Keywords: Phagocytes, Granulocytes, and Myelopoiesis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
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