Cytoskeletal Mechanisms of Platelet Formation

血小板是一种特殊的无核细胞，在止血、血管生成、创伤等方面发挥着重要作用。 治愈、免疫和炎症。血小板计数异常导致临床并发症和医疗 越来越需要昂贵输血的病症。随着对血小板输注的需求上升， 迫切需要更好地了解它们的形成机制。我们的调查 将以巨核细胞(MK)为靶细胞，巨核细胞是通过重塑细胞质生成血小板的前体细胞 珠状前血小板工艺，用作血小板生产的装配线。我们知道 细胞骨架力学为血小板的产生提供动力，但关于血小板生物生成的许多问题 仍未得到答复。虽然基于微管的力量对原血小板的伸长至关重要，但有一个 令人惊讶的是，对触发MK经历细胞骨架的机制缺乏了解 启动原血小板生成所需的重排。目标1将测试一个新的假设，即中心体 聚集和随后的单纺锤体形成导致成熟的巨噬细胞启动原血小板的形成。我们会 询问分子马达KIFC1在中心体聚集和诱导血小板原中的作用。虽然 皮质微管滑动推动血小板原延长的机制尚不清楚，我们最近 观察到肌动蛋白组装过程的抑制瘫痪了原血小板的延长，这表明了 肌动蛋白。这一令人兴奋的新数据表明，肌动蛋白可能作为分子离合器发挥作用，促进微管的形成。 微管滑动和/或锚定到膜上，这将在目标2中测试。最后，我们知道 血小板突起从骨髓延伸，突破血管内皮细胞屏障，将血小板沉积到 血，但我们不知道是怎么回事。Aim 3将采用工程化、内皮化、微流控的骨髓 芯片上测试肌动蛋白驱动的巨核细胞足体提供了一种穿透 内皮细胞。受生物启发的工程学将被用于研究足体如何转变为血小板原 并测试单纺锤体的形成在原血小板极化进入血流中的作用。我们 期待这项研究的发现将1)提高对分子机制的理解， 调节健康和疾病中的血小板形成，2)为新的治疗方法奠定基础 加速血小板减少患者的血小板生成，以及3)使未来能够在体外创造 血小板。

Blood platelets are specialized anucleate cells that play an essential role in hemostasis, angiogenesis, wound healing, immunity, and inflammation. Abnormal platelet counts result in clinical complications and medical conditions that increasingly require expensive transfusions. As the demand for platelet transfusions rises, the need for an improved understanding of their mechanistic formation has urgently increased. Our investigations will target megakaryocytes (MKs), the precursor cells that generate platelets by remodeling their cytoplasm into beaded proplatelet processes which function as the assembly lines for platelet production. We know that cytoskeletal mechanics power platelet production, but many questions about platelet biogenesis remain unanswered. While microtubule-based forces are critical for proplatelet elongation, there is a surprising lack of understanding of the mechanisms that trigger MKs to undergo the cytoskeletal rearrangements needed to initiate proplatelet production. Aim 1 will test a new hypothesis that centrosome clustering and subsequent monospindle formation cause mature MKs to initiate proplatelet formation. We will interrogate the role of the molecular motor KIFC1 in centrosome clustering and proplatelet induction. Although the mechanism by which sliding of cortical microtubules powers proplatelet extension is unknown, our recent observation that inhibition of the actin assembly process paralyzes proplatelet elongation suggests a role for actin. This exciting new data indicates that actin may function as a molecular clutch and promote microtubule sliding and/or anchoring of microtubules to the membrane, which will be tested in Aim 2. Finally, we know that proplatelet protrusions extend from bone marrow, breach the endothelial barrier, and deposit platelets into the blood, but we do not know how. Aim 3 will employ an engineered, endothelialized, microfluidic bone marrow on-a-chip to test the idea that actin-driven megakaryocyte podosomes provide a mechanism to penetrate the endothelium. Biologically inspired engineering will be used to study how podosomes transition to proplatelet production and to test the role of monospindle formation in proplatelet polarization into the bloodstream. We expect that findings from this investigation will 1) improve the understanding of the molecular mechanisms that regulate platelet formation in health and disease, 2) lay the foundation for novel therapeutic approaches to accelerate platelet production in patients with thrombocytopenia, and 3) enable the future creation of in vitro platelets.