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Blood, 1 February 2007, Vol. 109, No. 3, pp. 971-979.
Prepublished online as a Blood First Edition Paper on October 3, 2006; DOI 10.1182/blood-2006-04-020552.
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HEMATOPOIESIS
Down-regulation of RXR expression is essential for neutrophil development from granulocyte/monocyte progenitors
Sabine Taschner1,
Christina Koesters1,2,
Barbara Platzer1,
Almut Jörgl1,
Wilfried Ellmeier1,
Thomas Benesch3, and
Herbert Strobl1
1 Institute of Immunology, Medical University Vienna, Austria;
2 Competence Center for Biomolecular Therapeutics, Vienna, Austria;
3 Section of Medical Statistics, Medical University Vienna, Austria
Neutrophil granulocytes (Gs) represent highly abundant and short-lived leukocytes that are constantly regenerated from a small pool of myeloid committed progenitors. Nuclear receptor (NR) family members are ligand-activated transcription factors that play key roles in cellular proliferation and differentiation processes including myelopoiesis. Retinoid X receptor alpha (RXR ) represents the predominant NR types I and II homo- and heterodimerization partner in myeloid cells. Here we show that human myeloid progenitors express RXR protein at sustained high levels during macrophage colony-stimulating factor (M-CSF)induced monopoiesis. In sharp contrast, RXR is down-regulated during G-CSFdependent late-stage neutrophil differentiation from myeloid progenitors. Down-regulation of RXR is critically required for neutrophil development since ectopic RXR inhibited granulopoiesis by impairing proliferation and differentiation. Moreover, ectopic RXR was sufficient to redirect G-CSFdependent granulocyte differentiation to the monocyte lineage and to promote M-CSFinduced monopoiesis. Functional genetic interference with RXR signaling in hematopoietic progenitor/stem cells using a dominant-negative RXR promoted the generation of late-stage granulocytes in human cultures in vitro and in reconstituted mice in vivo. Therefore, our data suggest that RXR down-regulation is a critical requirement for the generation of neutrophil granulocytes.

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