Studies on the role of microtubule and actin filament regulatory proteins in megakaryo- and thrombopoiesis

• Applicant: Professor Dr. Markus Bender
• Subject Area: Hematology, Oncology
• Term: from 2015 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 268521205

• Final Report Year: 2021

Final Report Abstract

Cytoskeletal dynamics play a central role in platelet production and function. The objective of this Emmy Noether project was to investigate the role of microtubule- and actin filament-regulatory proteins in megakaryo- and thrombopoiesis in order to better understand the complex process of platelet production. In addition, we focused on the role of the cytoskeleton in platelet function. In the first project, we could demonstrate that the ADAP (adhesion- and degranulation-promoting adapter protein) protein plays a central role in megakaryocyte polarization. ADAP-deficient mice exhibited ectopic release of proplatelets and platelets into the bone marrow, associated with a reduced platelet count in the blood. Further evidence suggests that there is an axis of actin-regulatory proteins responsible for directional formation of proplatelets into the bloodstream. In another project, we addressed the question of the role of lamellipodia (plate-like protrusions) with their branched peripheral actin filaments in thrombus formation and stability, as this has been controversially discussed in the literature. Using a knockout mouse model lacking the Cyfip1 subunit of the WAVE complex, we demonstrated that the lack of lamellipodia formation in Cyfip1-deficient platelets has no effect on the hemostatic function and in vivo thrombus formation. Furthermore, we found that morphological changes of platelets differ between a static spreading assay and thrombus formation under flow. We also investigated the role of the large actin and microtubule filament crosslinker protein MACF1 (microtubule-actin crosslinking factor 1), which belongs to the spectraplakin family, in platelet function. We generated megakaryocyte/platelet-specific MACF1-deficient mice. MACF1 deficiency had no effect on basal platelet function. Compensatory upregulation of other proteins that can also bind to microtubule and actin filaments was not detected. The findings obtained in this project contribute to a better understanding of the complex interplay between the individual cytoskeletal components, their regulatory proteins, and their interaction partners in the process of platelet production and function.

Publications

• Twinfilin 2a is a regulator of platelet reactivity and turnover in mice. Blood. 2017 Oct 12;130(15):1746-1756
  Stritt, Simon; Beck, Sarah; Becker, Isabelle C.; Vögtle, Timo; Hakala, Markku; Heinze, Katrin G.; Du, Xiaoping; Bender, Markus; Braun, Attila; Lappalainen, Pekka & Nieswandt, Bernhard
  
• ADAP deficiency impairs megakaryocyte polarization with ectopic platelet release and causes microthrombocytopenia. Blood. 2018 Aug 9;132(6):635-646
  Spindler, Markus; van Eeuwijk, Judith M. M.; Schurr, Yvonne; Nurden, Paquita; Nieswandt, Bernhard; Stegner, David; Reinhold, Annegret & Bender, Markus
  
• Blood collection, platelet isolation and measurement of platelet count and size in mice-a practical guide. Platelets. 2018 Oct 22:1-10
  Aurbach, Katja; Spindler, Markus; Haining, Elizabeth J.; Bender, Markus & Pleines, Irina
  
• Coactosin-like 1 integrates signaling critical for shear-dependent thrombus formation in mouse platelets. Haematologica. 2020 Jun;105(6):1667-1676
  Scheller, Inga; Stritt, Simon; Beck, Sarah; Peng, Bing; Pleines, Irina; Heinze, Katrin G.; Braun, Attila; Otto, Oliver; Ahrends, Robert; Sickmann, Albert; Bender, Markus & Nieswandt, Bernhard
  
• Platelet lamellipodia formation is not required for thrombus formation and stability Blood. 2019 Dec 19;134(25):2318-2329
  Schurr, Yvonne; Sperr, Andreas; Volz, Julia; Beck, Sarah; Reil, Lucy; Kusch, Charly; Eiring, Patrick; Bryson, Sheila; Sauer, Markus; Nieswandt, Bernhard; Machesky, Laura & Bender, Markus
  
• The cytoskeletal crosslinking Protein MACF1 is dispensable for thrombus formation and hemostasis. Sci Rep. 2019 May 22;9(1):7726
  Schurr, Yvonne; Spindler, Markus; Kurz, Hendrikje & Bender, Markus
  
• Actin/microtubule crosstalk during platelet biogenesis in mice is critically regulated by Twinfilin1 and Cofilin1. Blood Adv. 2020 May 26;4(10):2124-2134
  Becker, Isabelle C.; Scheller, Inga; Wackerbarth, Lou M.; Beck, Sarah; Heib, Tobias; Aurbach, Katja; Manukjan, Georgi; Gross, Carina; Spindler, Markus; Nagy, Zoltan; Witke, Walter; Lappalainen, Pekka; Bender, Markus; Schulze, Harald; Pleines, Irina & Nieswandt, Bernhard
  
• Flow-accelerated platelet biogenesis is due to an elasto-hydrodynamic instability. Proc Natl Acad Sci USA. 2020 Jul 27:202002985
  Bächer, Christian; Bender, Markus & Gekle, Stephan
  
• SMIFH2 inhibition of platelets demonstrates a critical role for formin proteins in platelet cytoskeletal dynamics. J Thromb Haemost. 2020 Jan 13
  Green, Hannah L.H.; Zuidscherwoude, Malou; Alenazy, Fawaz; Smith, Christopher W.; Bender, Markus & Thomas, Steven G.
  
• Vps34 derived phosphatidylinositol 3-monophosphate modulates megakaryocyte maturation and proplatelet production through late endosomes/lysosomes J Thromb Haemost. 2020 Jul;18(7):1756-1772
  Bertović, Ivana; Kurelić, Roberta; Milošević, Ira; Bender, Markus; Krauss, Michael; Haucke, Volker & Jurak Begonja, Antonija