title: Critical role for ERK1/2 in bone marrow and fetal liver-derived primary megakaryocyte differentiation, motility, and proplatelet formation.
abstract: OBJECTIVE
  Megakaryopoiesis and platelet formation is a multistep process through which hematopoietic progenitor cells develop into mature megakaryocytes (MKs) and form proplatelets. The present study investigates the regulation of different steps of megakaryopoiesis (i.e., differentiation, migration, and proplatelet formation) by extracellar signal-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) in two models of primary murine MKs derived from bone marrow (BM) cells and fetal liver (FL) cells.
  
  
  METHODS
  A preparation of MKs was generated from BM obtained from femora and tibiae of C57BL6 mice. FL-derived MKs were obtained from the liver of mouse fetuses aged 13 to 15 days.
  
  
  RESULTS
  For both cell populations, activation of MEK-ERK1/2 pathway by thrombopoietin was found to have a critical role in MK differentiation, regulating polyploidy and surface expression of CD34, GPIIb, and GPIb. The MEK-ERK1/2 pathway plays a major role in migration of BM-derived MKs toward a stromal-cell-derived factor 1alpha (SDF1alpha) gradient, whereas unexpectedly, FL-derived cells fail to migrate in response to the chemokine due to negligible expression of its receptor, CXCR4. The MEK-ERK1/2 pathway also plays a critical role in the generation of proplatelets. In contrast, p38MAPK pathway was not involved in any of these processes.
  
  
  CONCLUSIONS
  This report demonstrates a critical role of MEK-ERK1/2 pathway in MK differentiation, motility, and proplatelet formation. This study highlights several differences between BM- and FL-derived MKs, which are discussed.
authors.affiliation: Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Mazharian
authors.forename: Steve P
authors.initials: SP
authors.lastname: Watson
authors.forename: Sonia
authors.initials: S
authors.lastname: Séverin
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D001792:Blood Platelets / Q000166:cytology*; D001854:Bone Marrow Cells / Q000166:cytology / Q000201:enzymology*; D002478:Cells, Cultured / Q000166:cytology / Q000201:enzymology; D054377:Chemokine CXCL12 / Q000494:pharmacology; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology*; D008099:Liver / Q000166:cytology* / Q000196:embryology / Q000201:enzymology; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008533:Megakaryocytes / Q000166:cytology / Q000201:enzymology*; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology*; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000096:biosynthesis / Q000235:genetics; D040201:Platelet Membrane Glycoprotein IIb / Q000096:biosynthesis / Q000235:genetics; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000032:analysis; D034061:Thrombopoiesis / Q000502:physiology*; D013926:Thrombopoietin / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000032:analysis
chemical_list: C488185:2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluoro-5-bromobenzamide; D000814:Aniline Compounds; D001549:Benzamides; D054377:Chemokine CXCL12; D008562:Membrane Glycoproteins; D019038:Platelet Glycoprotein GPIb-IX Complex; D040201:Platelet Membrane Glycoprotein IIb; C094990:adhesion receptor; D013926:Thrombopoietin; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C512964:Rps6ka1 protein, mouse; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases