Project description:Here we show that muscarinic type-1 (Chrm1) signaling in the central nervous system (CNS) promotes G-CSF-elicited HSC migration from the BM. Blockade of Chrm1 in the CNS, but not the periphery, reduced HSC mobilization. In Chrm1−⁄− mice, reduced mobilization was rescued by wild-type parabionts, suggesting the contribution of a soluble factor. We found that corticosterone levels were dramatically reduced in the BM, and its exogenous administration normalized the mobilization deficit of Chrm1−⁄− animals. Chrm1−⁄− HSCs have reduced nuclear glucocorticoid receptors (Nr3c1) and alterations in the expression of actin-organizing molecules. Polymerized actin formation and HSC mobilization are also impaired in mice harboring Nr3c1-deficient hematopoietic cells.
Project description:High ploidy large cytoplasmic megakaryocytes (LCM) are critical negative regulators of hematopoietic stem cells (HSC) and are responsible for platelet formation. Using a mouse knockout model with normal megakaryocyte numbers but essentially devoid of LCM (MK-LCM KO), we demonstrated a pronounced increase in bone marrow HSC concurrent with endogenous mobilization and extramedullary hematopoiesis. When HSC isolated from a MK-LCM KO microenvironment were transplanted in lethally irradiated mice, the absence of LCM increased HSC in BM, blood and spleen. Severe thrombocytopenia was observed in animals with diminished LCM, although there was no change in megakaryocyte ploidy distribution. In contrast, WT HSC-generated LCM regulated a normal HSC pool and prevented thrombocytopenia. The present label-free quantitative LC-MSMS data was used to determine proteins that are differentially expressed in bone marrow cells of MK-LCM WT versus MK-LCM KO mice.
Project description:After irradiation and bone-marrow transplantation, most of microglia and boarder-associated macrophages in the central nervous system is replaced by engranft cells. Taking advantages of Ms4a3-Cre: R26-TdTomato: Cx3cr1-gfp mice, we discriminated cells from monocyte precursors and hematopoietic stem cells with colors at 32 weeks following irradiation and bone-marrow transplantation. We sorted HSC-derived, monocyte-derived, and endogenouse microglia and leptomeningeal macrophages, and analyzed gene expression level between different cell populations using a bulk RNAseq method.
Project description:Fate decisions of haematopoietic stem cells (HSCs) to self-renew or differentiate in response to various demands are finely tuned by specialized microenvironments called “niches” in the bone marrow. Recent studies suggest that arterioles and sinusoids accompanied with distinct stromal cells marked by nerve/glial antigen 2 (NG2) and leptin receptor (LepR), compose distinct niches regulating quiescence and proliferation of HSCs, respectively. However, it remains unknown how the distinct niche cells differentially regulate the HSC functions. Here we show that effects of cytokines regulating HSC functions are dependent on the producing cell sources. Deletion of chemokine C-X-C motif ligand 12 (CXCL12) in NG2-cre targeted cells, which exclusively overlap with Nestin-GFP (Nes-GFP)+ stromal cells associated with arterioles and sinusoids, resulted in a robust reductions of HSCs in the bone marrow and massive mobilization. Deletion of CXCL12 from arteriolar NG2+ vascular smooth muscle cells caused a significant decrease of HSCs and altered HSC location in the marrow, while CXCL12 depletion from sinusoidal LepR+ cells did not reduce HSC numbers in the bone marrow. By contrast, deletion of stem cell factor (SCF) in LepR+ cells led to significant reductions in HSC numbers whereas SCF deletion in arteriolar NG2+ cells showed no effect on HSC numbers in the marrow. These results uncover the distinct contributions of cytokines derived from perivascular cells in separate vascular niches for HSC maintenance and mobilization. We sought to obtain comprehensive understanding of differences between peri-arteriolar and peri-sinusoidal niche cells by the present RNA-seq analysis.
Project description:Quiescent and dividing hemopoietic stem cells (HSC) display marked differences in their ability to move between the peripheral circulation and the bone marrow. Specifically, long-term engraftment potential predominantly resides in the quiescent HSC subfraction, and G-CSF mobilization results in the preferential accumulation of quiescent HSC in the periphery. In contrast, stem cells from chronic myeloid leukemia (CML) patients display a constitutive presence in the circulation. To understand the molecular basis for this, we have used microarray technology to analyze the transcriptional differences between dividing and quiescent, normal, and CML-derived CD34+ cells.
Project description:Aging of hematopoietic stem cells (HSCs) is associated with the decline of their regenerative capacity, and multi-lineage differentiation potential, contributing to development of blood disorders. The bone marrow microenvironment was recently suggested to influence HSC aging, however the underlying mechanisms remain largely unknown. Here, we show that HSC aging critically depends on bone marrow innervation by the sympathetic nervous system (SNS), as premature loss of SNS nerves or adrenoreceptor b3 (ADRb3) signaling in the microenvironment accelerated the appearance of HSC aging phenotypes reminiscent of physiological aging. Strikingly, supplementation of ADRb3 sympathomimetics to old mice significantly rejuvenated in vivo function of old HSCs, suggesting that the preservation or restitution of SNS innervation during aging may hold the potential for novel HSC rejuvenation strategies.
Project description:Stem cell function is regulated by specialized microenvironments called stem cell niches. These niches maintain stem cells in a dormant state and promote self-renewal. The most potent hematopoietic stem cells (HSC) with high self-renewal potential are reportedly enriched in the endosteal compared to the central region of the bone marrow. Therefore we analyzed the global transcriptome of the endosteal region and directly compared it to that of the central bone marrow (BM). This comparative, differential analysis revealed that in addition to genes specific to the osteoblastic and osteoclastic lineage and classic regulators of HSC (CXCL12, KIT ligand, angiopoietin-1, Jagged-1, N-cadherin), the endosteum abundantly expresses prostaglandin I2 (PGI2) synthase (Ptgis), which produces PGI2. PGI2 is a highly labile, lipid metabolite with no known roles in regulating HSCs. We show in this study that PGI2 is a potent regulator of HSC function. Therefore comparing endosteal versus central BM transcriptome is a viable approach for uncovering candidate genes that may regulate the function of HSC and the HSC niche.
Project description:<p>We are studying the natural history, pathogenesis and treatment of patients with WHIM syndrome, an immunodeficiency disorder characterized by warts, hypogammaglobulinemia, recurrent infections and neutropenia usually due to autosomal dominant gain-of-function mutations in chemokine receptor <i>CXCR4</i>. We have identified a patient born with WHIM syndrome and the WHIM mutation <i>CXCR4<sup>R334X</sup></i> who has been disease-free for 20 years and who lacks <i>CXCR4<sup>R334X</sup></i> in myeloid cells, the cells that drive disease manifestations. She is a genetic and hematopoietic mosaic, since she still has the mutation in lymphoid cells and non-hematopoietic cells. Cytogenetics and microarray analysis revealed that the mechanism of loss of the mutation was deletion of the mutant allele from one copy of chromosome 2. Whole genome sequencing of patient neutrophil and skin fibroblast genomic DNA revealed that the mechanism of deletion was chromothripsis, a process of chromosome shattering resulting in deletions and rearrangements of the non-deleted chromosomal segments. In the patient, this process evidently occurred in a single hematopoietic stem cell (HSC), resulting in deletion of the disease allele <i>CXCR4<sup>R334X</sup></i> and one copy of 163 other genes on chromosome 2. This HSC evidently acquired a growth advantage and repopulated the HSC population and the myeloid lineage. Consistent with this, studies using gene targeted mice in competitive bone marrow transplantation experiments revealed that selective <i>Cxcr4</i> haploinsufficiency (inactivation of one copy of <i>Cxcr4</i> and not of any other genes) was sufficient to confer a strong engraftment advantage over bone marrow cells from wild type mice as well as bone marrow cells from a mouse model of WHIM syndrome. These results suggest that <i>CXCR4</i> knockdown may be a useful strategy to enhance bone marrow engraftment in the absence of toxic bone marrow conditioning regimens.</p>
Project description:Haematopoietic stem cells (HSC) reside in locations within the bone marrow microenvironment (BMM) featuring a slightly higher extracellular calcium ion concentration [eCa2+]. HSC respond to [eCa2+] via the G-protein coupled calcium-sensing receptor (CaSR), but the role of CaSR for leukaemia and leukaemia stem cells (LSC), the malignant counterpart to HSC, is poorly defined. Here we performed a proteomic analysis on Lin- MLL AF9+ cells, comparing WT cells to cells lacking CaSR using TMT-based proteomics.