Function of actin-monomer-binding proteins in megakaryocytes and platelets

肌动蛋白和微管蛋白细胞骨架的调节性重组对于其前体细胞巨核细胞（MK）的血小板生物合成至关重要。此外，基本的血小板功能，如形状变化，颗粒释放，粘附/铺展在固定的细胞外基质（ECM）成分和聚集，严格依赖于微调的细胞骨架重排。小肌动蛋白单体结合蛋白twinfilin 1（Twf 1），twinfilin 2a（Twf 2a），环化酶相关蛋白1（CAP 1），环化酶相关蛋白2（CAP 2），胸腺素β 4（Tmsb 4x），cofilin（Cof）和profilin 1（Pfn 1）在有核细胞中调节细胞骨架动力学的功能在体外部分被确定，但它们在体内的功能在很大程度上仍然未知，特别是在血小板中。在我们的初步工作中，我们确定了ADF/Cof和Pfn 1在血小板产生和功能中的关键作用。进一步的数据也指出了一个重要的作用，Twf 2a在这些过程中，并提供了第一个证据，在体内的相互作用的Twf 1和Cof巨核细胞和血小板。在拟议的项目中，我们的目标是解剖的生理作用的Twf和他们假设的相互作用的合作伙伴在血小板的生物发生和功能。为此，我们将产生在Twf 1，Twf 2a，CAP 1，CAP 2，Tmsb 4x，TMSB 1和Pfn 1中具有组成性或MK-/血小板特异性单，双或三缺陷的小鼠品系，并对其进行详细的体外和体内血小板生物发生和功能研究。我们希望这些研究将有助于更好地了解细胞骨架的功能，并提供新的见解肌动蛋白和微管蛋白细胞骨架的小肌动蛋白单体结合蛋白的调节。此外，预期结果可能与造血系统疾病的诊断和治疗有关。

The regulated reorganization of the actin and tubulin cytoskeleton is of paramount importance for platelet biogenesis by their precursor cells, the megakaryocytes (MKs). In addition, essential platelet functions, such as shape change, granule release, adhesion/ spreading on immobilized extracellular matrix (ECM) components and aggregation, strictly depend on fine-tuned cytoskeletal rearrangements. The functions of the small actin-monomer-binding proteins twinfilin1 (Twf1), twinfilin2a (Twf2a), cyclase-associated protein 1 (CAP1), cyclase-associated protein 2 (CAP2), thymosin beta4 (Tmsb4x), cofilin (Cof) and profilin1 (Pfn1) in the regulation of cytoskeletal dynamics in nucleated cells are partially defined in vitro but their function in vivo remains largely unknown, particularly in platelets. In our preliminary work, we identified critical roles for ADF/Cof and Pfn1 in platelet production and function. Further data also point to an important role of Twf2a in these processes and provide the first evidence in vivo for an interaction of Twf1 and Cof in megakaryocytes and platelets. In the proposed project, we aim to dissect the physiological roles of Twf and their hypothetical interaction partners in platelet biogenesis and function. To this end, we will generate mouse lines with constitutive or MK-/platelet-specific single, double or triple-deficiencies in Twf1, Twf2a, CAP1, CAP2, Tmsb4x, Cof1 and Pfn1 and subject them to detailed in vitro and in vivo studies on platelet biogenesis and function. We expect that these studies will contribute to a better understanding of cytoskeletal functions and provide novel insights into the regulation of the actin- and tubulin cytoskeleton by small actin-monomer-binding proteins. In addtion, the expected results may be of relevance for the diagnosis and treatment of disorders of the hematopoietic system.