Studies on actin-mediated processes in platelet production and function in conditional knockout mice

• Applicant: Professor Dr. Markus Bender
• Subject Area: Hematology, Oncology ; Cell Biology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 452622720

Platelets are produced by bone marrow megakaryocytes. Platelet activation at sites of vascular injury is critical for the formation of a hemostatic plug which limits excessive blood loss, but also represents a major pathomechanism of ischemic cardio- and cerebrovascular diseases.The cytoskeleton and its rearrangements are of central importance in the final steps of thrombopoiesis as well as for platelet shape change after activation. Mutations in important cytoskeletal proteins lead to increased bleeding tendencies, which shows that the cytoskeletal integrity of platelets is critical for hemostasis. However, the underlying mechanisms are only poorly understood.In this project proposal three aspects of actin-mediated processes in platelet production and function are investigated: (I) ADAP-, WASP-, Pfn1-, and Arp2/3-deficient mice exhibit thrombocytopenia and ectopic release of proplatelet-like particles into the bone marrow. The reason for the ectopic release of proplatelets into the bone marrow of these mouse lines is not yet fully understood. In this part of the project we will investigate whether there is an axis of actin-regulatory proteins that is responsible for directional proplatelet formation into the bloodstream. (II) Furthermore, we will address the role of lamellipodial structures in platelet function. In preliminary work we could show that platelets that were unable to form lamellipodia have a normal hemostatic function and form stable thrombi. However, it is still unclear whether these structures play a role in other platelet-dependent processes. (III) The WASH complex contributes to vesicle transport through Arp2/3-dependent actin nucleation. First preliminary data show that the WASH subunit strumpellin plays an important role in the expression of the platelet integrin alphaIIb beta3. We hypothesize that strumpellin plays an important role in integrin recycling. Therefore, megakaryocytes and platelets from strumpellin-deficient mice will be studied to gain more insight into the function of the cytoskeleton and its regulation in protein internalization and in the endosomal signaling pathway.These studies may contribute to a better understanding of the role of the cytoskeleton in thrombopoiesis and platelet function.

• DFG Programme: Research Grants