Iruela-Arispe M L, Liska D J, Sage E H, Bornstein P
Department of Biological Structure, University of Washington, Seattle 98195.
Dev Dyn. 1993 May;197(1):40-56. doi: 10.1002/aja.1001970105.
Thrombospondin 1 is a secreted, trimeric glycoprotein that mediates interactions between cells and extracellular matrix and exhibits cell-specific effects on migration and proliferation. Recently, two additional thrombospondin genes (thrombospondin 2 and 3) have been identified. To study the functions of these proteins, we have used in situ hybridization and RNAse protection assays to compare the expression of the genes encoding thrombospondin 1, 2, and 3 during murine embryogenesis. Thrombospondin mRNAs were associated with ossification, neuronal organogenesis, and lung development, although transcripts were differentially expressed. Thrombospondin 1 was predominant from days 10 to 13. During this period, high but transient levels of expression were observed in the neural tube, head mesenchyme, and cardiac cushions. In contrast, a more constant level of thrombospondin 1 mRNA was apparent in resident megakaryocytes of the liver, as well as in circulating megakaryocytes; neither thrombospondin 2 nor 3 was detected in these cells. Thrombospondin 1 was also produced by cells of the developing kidney and gut. The expression of thrombospondin 2 was confined principally to organized connective tissue that included pericardium, pleura, perichondrium, periosteum, meninges, ligaments, and reticular dermis. Thrombospondin 2 was also produced by differentiating skeletal myoblasts and by cells of the kidney and gut. Moreover, high levels of expression were detected in blood vessels. Thrombospondin 3 mRNA was restricted to brain, cartilage, and lung. Although thrombospondin 1, 2, and 3 belong to a family of structurally related genes, the differences observed in the spatiotemporal distribution of the corresponding mRNAs indicate unique functions for these secreted proteins.
血小板反应蛋白1是一种分泌型三聚体糖蛋白，介导细胞与细胞外基质之间的相互作用，并对细胞迁移和增殖表现出细胞特异性作用。最近，又鉴定出另外两个血小板反应蛋白基因（血小板反应蛋白2和3）。为了研究这些蛋白质的功能，我们使用原位杂交和RNA酶保护试验来比较在小鼠胚胎发育过程中编码血小板反应蛋白1、2和3的基因的表达情况。血小板反应蛋白的mRNA与骨化、神经器官发生和肺发育有关，尽管转录本的表达存在差异。血小板反应蛋白1在第10至13天占主导地位。在此期间，在神经管、头部间充质和心脏垫中观察到高但短暂的表达水平。相比之下，血小板反应蛋白1 mRNA在肝脏驻留巨核细胞以及循环巨核细胞中表现出更稳定的水平；在这些细胞中未检测到血小板反应蛋白2和3。发育中的肾脏和肠道细胞也产生血小板反应蛋白1。血小板反应蛋白2的表达主要局限于有组织的结缔组织，包括心包、胸膜、软骨膜、骨膜、脑膜、韧带和网状真皮。分化的骨骼肌成肌细胞以及肾脏和肠道细胞也产生血小板反应蛋白2。此外，在血管中检测到高水平的表达。血小板反应蛋白3 mRNA局限于脑、软骨和肺。尽管血小板反应蛋白1、2和3属于结构相关基因家族，但在相应mRNA的时空分布中观察到的差异表明这些分泌蛋白具有独特的功能。
