Department of Anatomy and Embryology, University of Tsukuba, Tennodai, Tsukuba, Ibaraki, Japan.
Blood. 2013 Aug 29;122(9):1649-57. doi: 10.1182/blood-2012-12-471102. Epub 2013 Jun 21.
C1galt1 is essential for synthesis of the core 1 structure of mucin-type O-glycans. To clarify the physiological role of O-glycans in adult hematopoiesis, we exploited the interferon-inducible Mx1-Cre transgene to conditionally ablate the C1galt(flox) allele (Mx1-C1). Mx1-C1 mice exhibit severe thrombocytopenia, giant platelets, and prolonged bleeding times. Both the number and DNA ploidy of megakaryocytes in Mx1-C1 bone marrow were similar to those in wild-type (WT) mice. However, there were few proplatelets in Mx1-C1 primary megakaryocytes. Conversely, bone marrow transplanted from Mx1-C1 to WT and splenectomized Mx1-C1 mice gave rise to observations similar to those described above. The expression of GPIbα messenger RNA was unchanged in Mx1-C1 bone marrow, whereas flow cytometric and western blot analyses using megakaryocytes and platelets revealed that the expression of GPIbα protein was significantly reduced in Mx1-C1 mice. Moreover, circulating Mx1-C1 platelets exhibited an increase in the number of microtubule coils, despite normal levels of α- and β-tubulin. Our observations suggest that O-glycan is required for terminal megakaryocyte differentiation and platelet production and that the decrease in GPIbα in cells lacking O-glycan might be caused by increased proteolysis.
C1galt1 对于黏蛋白型 O-聚糖核心 1 结构的合成是必需的。为了阐明 O-聚糖在成人造血中的生理作用，我们利用干扰素诱导的 Mx1-Cre 转基因来条件性敲除 C1galt(flox)等位基因（Mx1-C1）。Mx1-C1 小鼠表现出严重的血小板减少症、巨大血小板和延长的出血时间。Mx1-C1 骨髓中的巨核细胞数量和 DNA 倍性与野生型（WT）小鼠相似。然而，在 Mx1-C1 原发性巨核细胞中很少有前血小板形成。相反，来自 Mx1-C1 的骨髓移植到 WT 和脾切除术 Mx1-C1 小鼠中，产生了与上述描述相似的观察结果。在 Mx1-C1 骨髓中 GPIbα 信使 RNA 的表达没有改变，而使用巨核细胞和血小板进行流式细胞术和 Western blot 分析显示，GPIbα 蛋白的表达在 Mx1-C1 小鼠中显著降低。此外，尽管 α-和 β-微管蛋白水平正常，但循环 Mx1-C1 血小板中微管线圈的数量增加。我们的观察结果表明，O-聚糖对于终末巨核细胞分化和血小板生成是必需的，并且缺乏 O-聚糖的细胞中 GPIbα 的减少可能是由于蛋白水解增加所致。
