Project description:Neutrophils are key component of the innate immune system in vertebrates. Diverse transcription factors and cofactors act in a well-coordinated manner to ensure proper neutrophil development. Dysregulation of the transcriptional program triggering neutrophil differentiation is associated with various human hematologic disorders such as neutropenia, neutrophilia, and leukemia. In the current study we show the zinc finger protein Znf687 is a lineage-specific transcription factor, whose deficiency leads to an impaired neutrophil development in zebrafish. Mechanistically, Znf687 functions as a negative regulator of gfi1aa, a pivotal modulator in terminal granulopoiesis, to regulate neutrophil maturation. Moreover, we found BRD4, an important epigenetic regulator, interacts with ZNF687 in neutrophils. Deficiency of brd4 results in similar defective neutrophil development as observed in znf687 mutant zebrafish. Biochemical and genetic analyses further reveal that instead of serving as a canonical transcriptional coactivator, Brd4 directly interacts and bridges Znf687 and Smrt nuclear corepressor on gfi1aa gene’s promoter to exert transcription repression. Overall, our work not only indicates Znf687 and Brd4 are reciprocally required in promoting granulopoiesis, but also provides new insights into the role of the two crucial regulators in transcriptional repression.
Project description:Staphylococcus aureus is the principal causative agent of osteomyelitis, a serious bacterial infection of bone that is associated with progressive inflammatory damage. Bone-forming osteoblasts have increasingly been recognized to play an important role in the initiation and progression of detrimental inflammation at sites of infection, and have been demonstrated to release an array of inflammatory mediators and factors that promote osteoclastogenesis and leukocyte recruitment following bacterial challenge. In the present study, we describe elevated bone tissue levels of the potent neutrophil-attracting chemokines, CXCL1, CXCL2, CXCL3, CXCL5, CCL3, and CCL7, in a murine model of post-traumatic staphylococcal osteomyelitis. RNA-Seq gene ontology analysis of isolated primary murine osteoblasts showed enrichment in differentially expressed genes involved in cell migration and chemokine receptor binding and chemokine activity following S. aureus infection, and a rapid increase in the expression of mRNA encoding CXCL1, CXCL2, CXCL3, CXCL5, CCL3, and CCL7, in these cells. Importantly, we have confirmed that such upregulated gene expression results in protein production with the demonstration that S. aureus challenge elicits the rapid and robust release of these chemokines by osteoblasts and does so in a bacterial dose-dependent manner. Furthermore, we have confirmed the ability of soluble osteoblast-derived chemoattractants to elicit the migration of a neutrophil-like cell line. As such, these studies demonstrate the robust production of CXCL1, CXCL2, CXCL3, CXCL5, CCL3, and CCL7, by osteoblasts in response to S. aureus infection, and the release of such neutrophil-attracting chemokines provides an additional mechanism by which osteoblasts could drive the inflammatory bone loss associated with staphylococcal osteomyelitis.
Project description:Bone morphogenetic proteins (BMPs) regulate many aspects of skeletal development, including osteoblast and chondrocyte differentiation, cartilage and bone formation, and cranial and limb development. Among them, BMP2, one of the most potent osteogenic signaling molecules, stimulates osteoblast differentiation. We used cDNA microarrays to elucidate regulators of BMP-2-induced osteoblast differentiation.
Project description:Defects in neutrophil number and survival are common to both hematologic disorders and chronic inflammatory diseases. At sites of inflammation, neutrophils respond to multiple signals that activate protein kinase A (PKA) signalling, which positively regulates neutrophil survival. We aimed to study the transcriptional responses to several stimuli in human neutrophils. We used microarrays to detail the global programme of gene expression and identified distinct classes of up-regulated genes, which pointing to a key role of NR4A receptors in regulation of neutrophil lifespan and homeostasis.
Project description:Osteolineage cells represent one of the critical bone marrow niche components that support maintenance of hematopoietic stem and progenitor cells (HSPCs). Recent studies demonstrate that extracellular vesicles (EVs) regulate stem cell development via horizontal transfer of bioactive cargo, including microRNAs (miRNAs). Here, we characterize the miRNA profile of EVs secreted by human osteoblasts and study their biological effect of on human umbilical cord blood-derived CD34+ HSPCs by sequencing, gene expression and biochemical analyses. Using next-generation sequencing we show that osteoblast-derived EVs contain highly abundant miRNAs specifically enriched in EVs, including critical regulators of hematopoietic proliferation (e.g., miR-29a). EV treatment of CD34+ HSPCs alters the expression of candidate miRNA targets, such as HBP1, BCL2 and PTEN. Furthermore, EVs enhance proliferation of CD34+ cells and their immature subsets in growth factor-driven ex vivo expansion cultures. Importantly, EV-expanded cells retain their differentiation capacity in vitro and show successful engraftment in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice in vivo. These discoveries reveal a novel osteoblast-derived EV-mediated mechanism for regulation of HSPC proliferation and warrant consideration of EV-miRNAs for the development of expansion strategies to treat hematological disorders.
Project description:Bone morphogenetic proteins (BMPs) regulate many aspects of skeletal development, including osteoblast and chondrocyte differentiation, cartilage and bone formation, and cranial and limb development. Among them, BMP2, one of the most potent osteogenic signaling molecules, stimulates osteoblast differentiation.
Project description:The role of MAP4K4 in the development of neutrophils remains largely unexplored. We utilized single cell sequencing (scRNA-seq) technology to elucidate the impact of Map4k4 deficiency on neutrophil maturation within mouse bone marrow. Through the application of scRNA-seq, we characterized the transcriptional changes across various stages of neutrophil development in both Map4k4-deficient (Map4k4-cKO) and control mice.
Project description:As critical executors of the immune system, neutrophils provide an immediate inflammatory response for the clearance of debris and microbes, which is essential for the protection of health. Developmentally, neutrophils and macrophages share common progenitors, whose fate is tightly controlled by transcriptional programs. Dysregulation of these programs causes severe hematological disorders, including neutropenia, neutrophilia, leukemia, and inflammatory disorders. However, the mechanisms underlying the generation of neutrophils through these programs are poorly understood. Here, we revealed that Ikzf1 and Myb were enriched in neutrophils. Overactivation of Ikzf1 promoted neutrophil generation while suppressing macrophage emergence. Conversely, the simultaneous loss of Ikzf1 and Myb, but not the individual mutations, drastically impaired neutrophil production and enlarged the macrophage pool in both zebrafish and mice. Mechanistically, Ikzf1 and Myb formed a complex that targeted irf8 and induced the expression of a long non-coding RNA (lncRNA), irf8-2, through a novel regulatory element. LncRNA irf8-2 biased neutrophil commitment by modulating irf8 dosage via Zfp36l1. The deletion of irf8-2 resulted in defective neutrophil development and enhanced macrophage production. However, a partial ratio of neutrophils and macrophages was restored when Ikzf1, Myb, and Irf8 were all compromised. Overall, our study reveals that Ikzf1 and Myb cooperatively bias neutrophil development against Irf8 via the lncRNA irf8-2 and Zfp36l. This study provides novel insights into the conserved molecular balance between neutrophil and macrophage development during myelopoiesis, with potential implications for understanding and treating myeloid disorders.