title: BMP signaling balances murine myeloid potential through SMAD-independent p38MAPK and NOTCH pathways.
abstract: Bone morphogenetic protein (BMP) signaling regulates early hematopoietic development, proceeding from mesoderm patterning through the progressive commitment and differentiation of progenitor cells. The BMP pathway signals largely through receptor-mediated activation of Mothers Against Decapentaplegic homolog (SMAD) proteins, although alternate pathways are modulated through various components of mitogen-activated protein kinase (MAPK) signaling. Using a conditional, short hairpin RNA (shRNA)-based knockdown system in the context of differentiating embryonic stem cells (ESCs), we demonstrated previously that Smad1 promotes hemangioblast specification, but then subsequently restricts primitive progenitor potential. Here we show that co-knockdown of Smad5 restores normal progenitor potential of Smad1-depleted cells, suggesting opposing functions for Smad1 and Smad5. This balance was confirmed by cotargeting Smad1/5 with a specific chemical antagonist, LDN193189 (LDN). However, we discovered that LDN treatment after hemangioblast commitment enhanced primitive myeloid potential. Moreover, inhibition with LDN (but not SMAD depletion) increased expression of Delta-like ligands Dll1 and Dll3 and NOTCH activity; abrogation of NOTCH activity restored LDN-enhanced myeloid potential back to normal, corresponding with expression levels of the myeloid master regulator, C/EBPα. LDN but not SMAD activity was also associated with activation of the p38MAPK pathway, and blocking this pathway was sufficient to enhance myelopoiesis. Therefore, NOTCH and p38MAPK pathways balance primitive myeloid progenitor output downstream of the BMP pathway.
authors.affiliation: Department of Surgery, Weill Cornell Medical College, New York, NY.
authors.forename: Brandoch D
authors.initials: BD
authors.lastname: Cook
authors.affiliation: Department of Surgery, Weill Cornell Medical College, New York, NY.
authors.forename: Todd
authors.initials: T
authors.lastname: Evans
mesh_terms: D000818:Animals; D052004:Bone Morphogenetic Protein Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism; D002135:Calcium-Binding Proteins; D002478:Cells, Cultured; D058732:Embryoid Bodies / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D055785:Gene Knockdown Techniques; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008565:Membrane Proteins / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D051379:Mice; D023461:Myeloid Progenitor Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D038042:Myelopoiesis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D051785:Smad Proteins / Q000378:metabolism*; D051898:Smad1 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051902:Smad5 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D019485:Bone Morphogenetic Proteins; D022763:CCAAT-Enhancer-Binding Protein-alpha; D002135:Calcium-Binding Proteins; C512925:Dlk1 protein, mouse; C511877:Dll3 protein, mouse; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; C554430:LDN 193189; D008565:Membrane Proteins; D011720:Pyrazoles; D011743:Pyrimidines; D034741:RNA, Small Interfering; D051880:Receptors, Notch; D051785:Smad Proteins; D051898:Smad1 Protein; C497401:Smad1 protein, mouse; D051902:Smad5 Protein; C497798:Smad5 protein, mouse; D048051:p38 Mitogen-Activated Protein Kinases; D052004:Bone Morphogenetic Protein Receptors