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Novel hematopoietic progenitor populations revealed by direct assessment of GATA1 protein expression and cMPL signaling events.

ABSTRACT: Hematopoietic stem cells (HSCs) must exhibit tight regulation of both self-renewal and differentiation to maintain homeostasis of the hematopoietic system as well as to avoid aberrations in growth that may result in leukemias or other disorders. In this study, we sought to understand the molecular basis of lineage determination, with particular focus on factors that influence megakaryocyte/erythrocyte-lineage commitment, in hematopoietic stem and progenitor cells. We used intracellular flow cytometry to identify two novel hematopoietic progenitor populations within the mouse bone-marrow cKit(+) Lineage (-) Sca1(+) (KLS) Flk2 (+) compartment that differ in their protein-level expression of GATA1, a critical megakaryocyte/erythrocyte-promoting transcription factor. GATA1-high repopulating cells exhibited the cell surface phenotype KLS Flk2(+ to int), CD150(int), CD105(+), cMPL(+), and were termed "FSE cells." GATA1-low progenitors were identified as KLS Flk2(+), CD150(-), and cMPL(-), and were termed "Flk(+) CD150(-) cells." FSE cells had increased megakaryocyte/platelet potential in culture and transplant settings and exhibited a higher clonal frequency of colony-forming unit-spleen activity compared with Flk(+) CD150(-) cells, suggesting functional consequences of GATA1 upregulation in promoting megakaryocyte and erythroid lineage priming. Activation of ERK and AKT signal-transduction cascades was observed by intracellular flow cytometry in long-term HSCs and FSE cells, but not in Flk(+) CD150(-) cells in response to stimulation with thrombopoietin, an important megakaryocyte-promoting cytokine. We provide a mechanistic rationale for megakaryocyte/erythroid bias within KLS Flk2(+) cells, and demonstrate how assessment of intracellular factors and signaling events can be used to refine our understanding of lineage commitment during early definitive hematopoiesis.

SUBMITTER: Heffner GC

PROVIDER: S-EPMC4100980 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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Novel hematopoietic progenitor populations revealed by direct assessment of GATA1 protein expression and cMPL signaling events.

Heffner Garrett C GC Clutter Matthew R MR Nolan Garry P GP Weissman Irving L IL

Stem cells (Dayton, Ohio) 20111101 11

Hematopoietic stem cells (HSCs) must exhibit tight regulation of both self-renewal and differentiation to maintain homeostasis of the hematopoietic system as well as to avoid aberrations in growth that may result in leukemias or other disorders. In this study, we sought to understand the molecular basis of lineage determination, with particular focus on factors that influence megakaryocyte/erythrocyte-lineage commitment, in hematopoietic stem and progenitor cells. We used intracellular flow cyto ...[more]

PMID: 21898686

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Project description:How inflammatory responses are mechanistically modulated by nicotinic acetylcholine receptors (nAChR), especially by receptors composed of alpha7 (?7) subunits, is poorly defined. This includes a precise definition of cells that express ?7 and how these impact on innate inflammatory responses. To this aim we used mice generated through homologous recombination that express an Ires-Cre-recombinase bi-cistronic extension of the endogenous ?7 gene that when crossed with a reporter mouse expressing Rosa26-LoxP (yellow fluorescent protein (YFP)) marks in the offspring those cells of the ?7 cell lineage (?7(lin+)). In the adult, on average 20-25 percent of the total CD45(+) myeloid and lymphoid cells of the bone marrow (BM), blood, spleen, lymph nodes, and Peyers patches are ?7(lin+), although variability between litter mates in this value is observed. This hematopoietic ?7(lin+) subpopulation is also found in Sca1(+)cKit(+) BM cells suggesting the ?7 lineage is established early during hematopoiesis and the ratio remains stable in the individual thereafter as measured for at least 18 months. Both ?7(lin+) and ?7(lin-) BM cells can reconstitute the immune system of naïve irradiated recipient mice and the ?7(lin+):?7(lin-) beginning ratio is stable in the recipient after reconstitution. Functionally the ?7(lin+):?7(lin-) lineages differ in response to LPS challenge. Most notable is the response to LPS as demonstrated by an enhanced production of IL-12/23(p40) by the ?7(lin+) cells. These studies demonstrate that ?7(lin+) identifies a novel subpopulation of bone marrow cells that include hematopoietic progenitor cells that can re-populate an animal's inflammatory/immune system. These findings suggest that ?7 exhibits a pleiotropic role in the hematopoietic system that includes both the direct modulation of pro-inflammatory cell composition and later in the adult the role of modulating pro-inflammatory responses that would impact upon an individual's lifelong response to inflammation and infection.

Dataset Information

Novel hematopoietic progenitor populations revealed by direct assessment of GATA1 protein expression and cMPL signaling events.

Publications

Novel hematopoietic progenitor populations revealed by direct assessment of GATA1 protein expression and cMPL signaling events.

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