Yuan S, Darnell D K, Schoenwolf G C
Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City 84132, USA.
Dev Biol. 1995 Dec;172(2):567-84. doi: 10.1006/dbio.1995.8064.
The notochord normally arises from committed cells in the rostral tip of the primitive streak. After removal of these cells from the avian gastrula, embryos with notochords nevertheless develop in the majority of cases. A region required for the formation of this reconstituted notochord lies lateral to the primitive streak. In the present study we have determined that this region acts as an inducer for more lateral cells in the epiblast, which actually give rise to the reconstituted notochord. The strongest inducing region lies between 0-250 micrometer lateral to the streak and 500-750 micrometer caudal to the rostral end of the streak and chiefly contains cells normally fated to form lateral plate and somitic mesoderm. The responding region is located 250-500 micrometer lateral to the streak and 0-750 micrometer caudal to the rostral end of the streak. This area chiefly contains cells normally fated to form neural ectoderm, although cells normally fated to form lateral plate and somitic mesoderm are also within this area. The inducing and responding areas interact to form reconstituted notochord either when the primitive streak, including its rostral end (Hensen's node), is removed from the cultured blastoderm or when the inducer and responder are grafted together into an ectopic site. Grafting Hensen's node into isolates containing both inducer and responder blocks formation of reconstituted notochord, suggesting that Hensen's node suppresses formation of lateral notochords during normal development. These findings increase our understanding of the early interactions between mesoderm and ectoderm and provide a novel model system that is well defined and accessible for studying inductive events in higher vertebrates.
脊索通常起源于原条前端的定向细胞。从鸡胚原肠胚中移除这些细胞后，大多数情况下仍会发育出带有脊索的胚胎。形成这种重建脊索所需的区域位于原条的外侧。在本研究中，我们确定该区域作为上胚层中更外侧细胞的诱导物，这些细胞实际上产生了重建的脊索。最强的诱导区域位于原条外侧0 - 250微米以及原条前端尾侧500 - 750微米之间，主要包含通常注定形成侧板和体节中胚层的细胞。反应区域位于原条外侧250 - 500微米以及原条前端尾侧0 - 750微米。该区域主要包含通常注定形成神经外胚层的细胞，尽管通常注定形成侧板和体节中胚层的细胞也在这个区域内。当从培养的胚盘移除原条，包括其前端（亨氏结）时，或者当诱导物和反应细胞被移植到异位位点时，诱导区域和反应区域相互作用形成重建的脊索。将亨氏结移植到同时包含诱导物和反应细胞的分离物中会阻止重建脊索的形成，这表明亨氏结在正常发育过程中抑制外侧脊索的形成。这些发现增进了我们对中胚层和外胚层早期相互作用的理解，并提供了一个定义明确且易于研究高等脊椎动物诱导事件的新型模型系统。
