title: Megakaryocytes assemble podosomes that degrade matrix and protrude through basement membrane.
abstract: Megakaryocytes give rise to platelets via extension of proplatelet arms, which are released through the vascular sinusoids into the bloodstream. Megakaryocytes and their precursors undergo varying interactions with the extracellular environment in the bone marrow during their maturation and positioning in the vascular niche. We demonstrate that podosomes are abundant in primary murine megakaryocytes adherent on multiple extracellular matrix substrates, including native basement membrane. Megakaryocyte podosome lifetime and density, but not podosome size, are dependent on the type of matrix, with podosome lifetime dramatically increased on collagen fibers compared with fibrinogen. Podosome stability and dynamics depend on actin cytoskeletal dynamics but not matrix metalloproteases. However, podosomes degrade matrix and appear to be important for megakaryocytes to extend protrusions across a native basement membrane. We thus demonstrate for the first time a fundamental requirement for podosomes in megakaryocyte process extension across a basement membrane, and our results suggest that podosomes may have a role in proplatelet arm extension or penetration of basement membrane.
authors.affiliation: University of Glasgow College of Medical, Veterinary and Life Sciences and Beatson Institute for Cancer Research, Bearsden, Glasgow, UK.
authors.forename: Hannah
authors.initials: H
authors.lastname: Schachtner
authors.forename: Simon D J
authors.initials: SD
authors.lastname: Calaminus
authors.forename: Amy
authors.initials: A
authors.lastname: Sinclair
authors.forename: James
authors.initials: J
authors.lastname: Monypenny
authors.forename: Michael P
authors.initials: MP
authors.lastname: Blundell
authors.forename: Catherine
authors.initials: C
authors.lastname: Leon
authors.forename: Tessa L
authors.initials: TL
authors.lastname: Holyoake
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Thrasher
authors.forename: Alison M
authors.initials: AM
authors.lastname: Michie
authors.forename: Milica
authors.initials: M
authors.lastname: Vukovic
authors.forename: Christian
authors.initials: C
authors.lastname: Gachet
authors.forename: Gareth E
authors.initials: GE
authors.lastname: Jones
authors.forename: Steven G
authors.initials: SG
authors.lastname: Thomas
authors.forename: Steve P
authors.initials: SP
authors.lastname: Watson
authors.forename: Laura M
authors.initials: LM
authors.lastname: Machesky
mesh_terms: D000818:Animals; D001485:Basement Membrane / Q000378:metabolism / Q000502:physiology*; D001792:Blood Platelets / Q000378:metabolism / Q000502:physiology; D022081:Cell Surface Extensions / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000378:metabolism*; D005340:Fibrinogen / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007231:Infant, Newborn; D020782:Matrix Metalloproteinases / Q000378:metabolism; D008533:Megakaryocytes / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D024462:Myosin Type II / Q000378:metabolism
chemical_list: D005340:Fibrinogen; D020782:Matrix Metalloproteinases; D024462:Myosin Type II