ABSTRACT: Thymic T-cell progenitor development is supported by membrane bound Kit ligand provided by a combined vascular endothelial and epithelial niche.
Project description:Thymic T-cell progenitor development is supported by membrane bound Kit ligand provided by a combined vascular endothelial and epithelial niche.
Project description:The ligand for the c-Kit receptor, KitL, exists as a membrane-associated (mKitL) and a soluble form (sKitL). KitL functions outside c-Kit activation have not been identified. We show that co-culture of c-Kit– and mKitL–expressing NIH3T3 cells results in signaling through mKitL: c-Kit–bound mKitL recruits calcium-modulating cyclophilin ligand (CAML) to selectively activate Akt, leading to CREB phosphorylation, mTOR pathway activation, and increased cell proliferation. Activation of mKitL in thymic vascular endothelial cells (VECs) induces mKitL- and Akt-dependent proliferation, and genetic ablation of mKitL in thymic VECs blocks their c-Kit responsiveness and proliferation during neonatal thymic expansion. Therefore, mKitL–c-Kit form a bi-directional signaling complex that acts in the developing thymus to coordinate thymic VEC and early thymic progenitor (ETP) expansion by simultaneously promoting ETP survival and VEC proliferation. This mechanism may be relevant to both normal tissues and malignant tumors that depend on KitL–c-Kit signaling for their proliferation.
Project description:How disseminated tumor cells (DTCs) engage specific stromal components in distant organs for survival and outgrowth is a critical but poorly understood step of the metastatic cascade. Previous studies have demonstrated the importance of the epithelial-mesenchymal transition (EMT) in promoting the cancer stem cell properties needed for metastasis initiation, while the reverse process of mesenchymal-epithelial transition (MET) is required for metastatic outgrowth. Here we report that this paradoxical requirement for simultaneous induction of both MET and cancer stem cell traits in DTCs is provided by bone vascular niche E-selectin. Using cell surface alkoxyamine-biotinylation and label-free LC-MS/MS, Glg1 was identified as a top candidate Fut3/Fut6-dependent E-selectin ligand. We functionally validated their involvement in the formation of bone metastasis. These findings provide unique insights into the functional role of E-selectin as a component of the vascular niche criticalfor metastatic colonization in bone.
Project description:Pluripotent stem cells (PSC) represent an alternative source of hematopoietic stem cells (HSCs). Clinical translation is impeded by limited engraftment of human (h)PSC-multipotent progenitor cells (MPP). This barrier suggests that additional cues are required for definitive hematopoiesis. We hypothesized that vascular niche producing Notch ligands Jagged-1 (JAG1) and Delta-like ligand-4 (DLL4) would drive definitive hematopoiesis. To test our hypothesis, hes2 human embryonic stem cells (hESC) 2 and Macaca nemestrina (Mn) iPSC line-7 were differentiated with cytokines ± endothelial cells (EC), which express JAG1 and DLL4. EC co-culture supported emergence of 8-fold more CD34+CD45+ cells compared to co-culture with cytokines ± ECs with JAG1 or DLL4 knockdown. EC-induced cells exhibit Notch activation and express HSC-specific targets of Notch signaling RUNX1 and GATA2. EC-induced PSC-MPP engraft at a higher level in NSG mice compared to cytokine-induced cells (10% >5 months), and selection increased engraftment (30%). Long-term engraftment and the myeloid-to-lymphoid ratio achieved with vascular niche induction is similar to levels achieved for cord blood MPP and up to 20-fold higher than hPSC-MPP engraftment. Our findings identify a previously underappreciated role for endothelial Notch ligands in PSC definitive hematopoiesis and production of long-term engrafting CD34+ cells and suggest they are critical for HSC emergence. Transcriptome sequencing of Macaca nemestrina (Mn) iPSCs
Project description:Specialized niche environments specify and maintain stem and progenitor cells, but little is known about the identities and functional interactions of niche components in vivo. Here, we describe a modular system for the generation of artificial hematopoietic niches in the mouse embryo. A circumscribed tissue that lacks niche function but is physiologically accessible for hematopoietic progenitor cells is functionalized by individual and combinatorial expression of four factors, the chemokines Ccl25 and Cxcl12, the cytokine Scf and the Notch ligand DLL4. The distinct phenotypes and variable numbers of hematopoietic cells in the resulting niches reveal synergistic, context-dependent and hierarchical interactions among niche effector molecules. The surprisingly simple rules determining niche outcomes enable the in vivo engineering of artificial niches conducive to the presence of distinct myeloid or T or B lymphoid lineage precursors. The dataset comprises 24 samples divided into eight sample groups each representing a different lymphoid progenitor cell type isolated from wild-type (+/-) or transgenic (-/-) thymic niches. -/-, Foxn1-deficient genotype; +/-, Foxn1 heterozygous phenotype; DP, CD4/CD8 double-poisztive thymocytes; DN3, CD4/CD8-negative stage 3 thymocytes; SP4, CD4 single-positive thymocytes; SP8, CD8 single-positive thymocytes; B IgM-, IgM surface negative B cells; B IgM+, IgM surface positive B cells; B IgM- -/-, IgM surface negative B cells from Foxn1-deficient genotype.
Project description:Metastasis is the primary cause of cancer-related mortality and the mechanistically least well understood step of the tumor progression cascade. Employing surgical preclinical metastasis models, we show here that small primary tumors reprogram the body’s vascular endothelium to alter systemic homeostasis and to condition the premetastatic niche for metastatic colonization. Endothelial cells thereby serve as an amplifier of tumor-induced instructive signals. The combined endothelial transcriptomic and serum proteomic screen identified the TGFß pathway signaling specifier LRG1 as an early vascular niche instructor of metastatic colonization. Adjuvant LRG1 inhibition to primary tumor-resected mice delayed metastatic growth and increased overall survival. The study has thereby established the premetastatic systems map of primary tumor-induced vascular changes and identified LRG1 as a therapeutic target for metastasis
Project description:Although bone marrow (BM) niche cells are essential for hematopoietic stem cell (HSC) maintenance, their interaction in response to stress is not well defined. Here, we used a mouse model of acute thrombocytopenia to investigate the crosstalk between HSCs and niche cells during restoration of the thrombocyte pool. This process required membrane-localized stem cell factor (m-SCF) in megakaryocytes, which was regulated by vascular endothelial growth factor A (VEGF-A) and platelet-derived growth factor-B (PDGF-B) derived from BM endothelial cells. HSCs and multipotent progenitors 2 (MPP2), but not MPP3/4 were subsequently activated by a dual receptor tyrosine kinase (RTK)-dependent signaling event, namely m-SCF/c-Kit and VEGF-A/VEGFR-2, contributing to their selective and early proliferation. Our findings describe a dynamic network of signals in response to the acute loss of a single blood cell type, and reveal the important role of three RTKs in orchestrating the selective activation of HSCs and progenitor cells in thrombocytopenia.
Project description:Pluripotent stem cells (PSC) represent an alternative source of hematopoietic stem cells (HSCs). Clinical translation is impeded by limited engraftment of human (h)PSC-multipotent progenitor cells (MPP). This barrier suggests that additional cues are required for definitive hematopoiesis. We hypothesized that vascular niche producing Notch ligands Jagged-1 (JAG1) and Delta-like ligand-4 (DLL4) would drive definitive hematopoiesis. To test our hypothesis, hes2 human embryonic stem cells (hESC) 2 and Macaca nemestrina (Mn) iPSC line-7 were differentiated with cytokines ± endothelial cells (EC), which express JAG1 and DLL4. EC co-culture supported emergence of 8-fold more CD34+CD45+ cells compared to co-culture with cytokines ± ECs with JAG1 or DLL4 knockdown. EC-induced cells exhibit Notch activation and express HSC-specific targets of Notch signaling RUNX1 and GATA2. EC-induced PSC-MPP engraft at a higher level in NSG mice compared to cytokine-induced cells (10% >5 months), and selection increased engraftment (30%). Long-term engraftment and the myeloid-to-lymphoid ratio achieved with vascular niche induction is similar to levels achieved for cord blood MPP and up to 20-fold higher than hPSC-MPP engraftment. Our findings identify a previously underappreciated role for endothelial Notch ligands in PSC definitive hematopoiesis and production of long-term engrafting CD34+ cells and suggest they are critical for HSC emergence.