Project description:Platelet homeostasis is essential for vascular integrity and immune defense. While the process of platelet formation by fragmenting megakaryocytes (thrombopoiesis) has been extensively studied, the cellular and molecular mechanisms required to constantly replenish the pool of megakaryocytes (MKs) by their progenitor cells (megakaryopoiesis) remains unclear. Here we use intravital imaging to track the cellular dynamics of megakaryopoiesis over days. We identify plasmacytoid dendritic cells (pDCs) as homeostatic sensors that monitor the bone marrow for apoptotic MKs and deliver IFN- to the MK niche triggering local on-demand proliferation and maturation of MK progenitors. This fine-tuned coordination between thrombopoiesis and megakaryopoiesis is crucial for MK and platelet homeostasis in steady state and stress. However, excessive activation of pDCs, such as by viral infections, can disturb this homeostatic circuit. Accordingly, we show that pDCs activated by SARS-CoV2 drive inappropriate megakaryopoiesis. Together, we uncover a hitherto unknown pDC-dependent homeostatic circuit that involves innate immune sensing and demand-adapted release of inflammatory mediators to maintain tissue homeostasis of the megakaryocytic lineage.
Project description:The hematopoietic system gives rise to a heterogeneous population of terminally differentiated cells that reside in the bone marrow (BM) to fulfill their roles in immunity, blood clotting and tissue oxygenation. Hematopoietic stem and progenitor cells are at the apex of a hierarchically organized maturation cascade constantly replenishing the pool of differentiated cells to maintain blood cell homeostasis. The bone marrow microenvironment is functionally compartmentalized by heterogeneous niche cells that provide physical and soluble signals to spatio-temporally organize hematopoiesis. Megakaryocytes (MKs) are niche cells of hematopoietic origin that support hematopoietic stem cell (HSCs) homeostasis and generate circulating platelets. Platelet production involves the release of MK fragments while their cell body is entirely consumed in a process termed thrombopoiesis. Consequently, replenishment of fragmented MKs from MK progenitors (termed megakaryopoiesis) is required to ensure sufficient platelet production, but also to maintain MK homeostasis within the HSC niche. Here, we used intravital imaging of the megakaryocytic lineage to identify the spatio-temporal patterns of megakaryopoiesis during steady state and thrombocytopenia. We show that MK consumption during thrombopoiesis is compensated by immediate and local proliferation of MK progenitors. MK homeostasis is controlled by plasmacytoid dendritic cells (pDCs) that scan the BM and secrete Interferon alpha (INFa) upon detection of exhausted megakaryocytes to trigger megakaryopoiesis. We identified local pDC-derived INFa release as a physiological inflammatory stimulus of the bone marrow niche that synchronizes megakaryopoiesis and thrombopoiesis to maintain homeostasis of MKs and platelets in steady state and under stress. Viral infection with SARS-CoV-2 can manipulate pDC-driven MK proliferation leading to inappropriate megakaryopoiesis, which has been associated with thrombotic complications during COVID-19.
Project description:Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive malignancy assumed to originate from plasmacytoid dendritic cells (pDCs), which affects the skin and bone marrow and sequentially other organ systems. Here, we used EPIC arrays to characterize methylation profiles in 51 BPDCN cases.
Project description:We used microarrays to detail the global program of gene expression underlying the effect of p17 on human plasmacytoid dendritic cells and was compared to CpG profile. Experiment Overall Design: Human plasmacytoid dendritic cells were purified from two donors and cultured in the presence of p17 or CpG for 18 h.
Project description:Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy that is most similar in expression profiles to plasmacytoid dendritic cells. However, patients often exhibit features of AML and can progress to AML. In this project, we will determine the differentially and commonly expressed genes between BPDCN and AML specimens. Available BPDCN and TET2-mutated AML specimens were taken for transcriptome microarray analysis.
Project description:Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive malignancy assumed to originate from plasmacytoid dendritic cells (pDCs), which mostly affects the skin, bone marrow and lymph nodes and sequentially other organ systems. We applied paired WES/RNA-seq combined with genome-wide copy-number analysis to characterize 47 BPDCN patients regarding mutational drivers, cytogenetic aberrations and gene-expression profiles.
Project description:This SuperSeries is composed of the following subset Series: GSE24726: Gene expression profile of mature plasmacytoid dendritic cells (PDC) after the deletion of transcription factor E2-2 GSE24740: Binding targets of transcription factor E2-2 in human plasmacytoid dendritic cells Refer to individual Series
Project description:To investigate the effect of IVIG and desialylated IVIG on the activation of plasmacytoid dendritic cells (pDCs). Human primary plasmacytoid dendritic cells were treated with TLR stimulation together with or without IVIG or desialylated IVIG, and the change of genes were analyzed. Primary human pDCs were preincubated with or without 10mg/ml IVIG or desialylated IVIG followed by stimulation with CpG overnight. The different genes between IVIG+CpG and desialylated IVIG+CpG were analyzed.