Labor für Pädiatrische Molekularbiologie der Klinik für Allgemeine Pädiatrie, Charité-Universitätsmedizin, Berlin, Germany.
Blood. 2009 Dec 24;114(27):5532-40. doi: 10.1182/blood-2009-04-216804. Epub 2009 Oct 2.
Terminally mature megakaryocytes undergo dramatic cellular reorganization to produce hundreds of virtually identical platelets. A hallmark feature of this process is the generation of an elaborate system of branched protrusions called proplatelets. We recently identified RanBP10 as a tubulin-binding protein that is concentrated along polymerized microtubules in mature megakaryocytes. RanBP10 depletion in vitro caused the disturbance of polymerized filaments. Here we study the function of RanBP10 in vivo by generating deficient mice using a gene-trap approach. Mutant mice show normal platelet counts, and fetal liver-derived megakaryocytes reveal only slightly reduced proplatelet formation. However, ultrastructural analysis unveiled a significantly increased geometric axis ratio for resting platelets, and many platelets exhibited disorders in microtubule filament numbers and localization. Mutant mice showed a markedly prolonged bleeding time. Granule release, a process that depends on internal contraction of the microtubule marginal coil, also was reduced. Flow cytometry analysis revealed reduced expression of CD62P and CD63 after PAR4-peptide stimulation. These data suggest that RanBP10 plays an essential role in hemostasis and in maintaining microtubule dynamics with respect to both platelet shape and function.
终末成熟的巨核细胞经历剧烈的细胞重排，产生数百个几乎相同的血小板。这个过程的一个显著特征是产生了一种叫做血小板前体的复杂分支突起系统。我们最近发现 RanBP10 是一种微管结合蛋白，在成熟巨核细胞中沿聚合微管集中。体外 RanBP10 耗竭会导致聚合丝的紊乱。在这里，我们通过基因捕获方法生成缺陷型小鼠来研究 RanBP10 在体内的功能。突变小鼠的血小板计数正常，胎肝来源的巨核细胞显示血小板前体形成仅略有减少。然而，超微结构分析显示静止血小板的几何轴比显著增加，许多血小板显示微管丝数量和定位异常。突变小鼠的出血时间明显延长。依赖于微管边缘线圈内部收缩的颗粒释放也减少了。流式细胞术分析显示，PAR4 肽刺激后 CD62P 和 CD63 的表达减少。这些数据表明，RanBP10 在止血和维持微管动力学方面，对血小板的形状和功能都起着至关重要的作用。
