title: Contractile forces sustain and polarize hematopoiesis from stem and progenitor cells.
abstract: Self-renewal and differentiation of stem cells depend on asymmetric division and polarized motility processes that in other cell types are modulated by nonmuscle myosin-II (MII) forces and matrix mechanics. Here, mass spectrometry-calibrated intracellular flow cytometry of human hematopoiesis reveals MIIB to be a major isoform that is strongly polarized in hematopoietic stem cells and progenitors (HSC/Ps) and thereby downregulated in differentiated cells via asymmetric division. MIIA is constitutive and activated by dephosphorylation during cytokine-triggered differentiation of cells grown on stiff, endosteum-like matrix, but not soft, marrow-like matrix. In vivo, MIIB is required for generation of blood, while MIIA is required for sustained HSC/P engraftment. Reversible inhibition of both isoforms in culture with blebbistatin enriches for long-term hematopoietic multilineage reconstituting cells by 5-fold or more as assessed in vivo. Megakaryocytes also become more polyploid, producing 4-fold more platelets. MII is thus a multifunctional node in polarized division and niche sensing.
authors.affiliation: Biophysical Engineering Lab, University of Pennsylvania, Philadelphia, PA 19104, USA; Cell and Molecular Biology and Pharmacology Graduate Groups, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Jae-Won
authors.initials: JW
authors.lastname: Shin
authors.affiliation: Biophysical Engineering Lab, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Amnon
authors.initials: A
authors.lastname: Buxboim
authors.affiliation: Biophysical Engineering Lab, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Kyle R
authors.initials: KR
authors.lastname: Spinler
authors.affiliation: Biophysical Engineering Lab, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Joe
authors.initials: J
authors.lastname: Swift
authors.affiliation: Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Christian
authors.affiliation: Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Hunter
authors.affiliation: UMR S949, Inserm, Université de Strasbourg, Établissement Français du Sang, Strasbourg, 67000, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Léon
authors.affiliation: UMR S949, Inserm, Université de Strasbourg, Établissement Français du Sang, Strasbourg, 67000, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Gachet
authors.affiliation: Biophysical Engineering Lab, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: P C Dave P
authors.initials: PC
authors.lastname: Dingal
authors.affiliation: Biophysical Engineering Lab, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Irena L
authors.initials: IL
authors.lastname: Ivanovska
authors.affiliation: Biophysical Engineering Lab, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Florian
authors.initials: F
authors.lastname: Rehfeldt
authors.affiliation: Life Sciences Division, University of California, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Division of Hematology/Oncology, University of California, San Francisco, San Francisco, CA 94143, USA.
authors.forename: Joel Anne
authors.initials: JA
authors.lastname: Chasis
authors.affiliation: Biophysical Engineering Lab, University of Pennsylvania, Philadelphia, PA 19104, USA; Cell and Molecular Biology and Pharmacology Graduate Groups, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address: discher@seas.upenn.edu.
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Discher
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D019070:Cell Lineage; D002465:Cell Movement; D049109:Cell Proliferation; D005434:Flow Cytometry; D006410:Hematopoiesis / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000502:physiology; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D024507:Nonmuscle Myosin Type IIA / Q000378:metabolism*; D024501:Nonmuscle Myosin Type IIB / Q000378:metabolism*; D010766:Phosphorylation; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D055153:Stem Cell Niche / Q000502:physiology
chemical_list: D006576:Heterocyclic Compounds, 4 or More Rings; C472645:blebbistatin; D024507:Nonmuscle Myosin Type IIA; D024501:Nonmuscle Myosin Type IIB