Schoenwolf G C, Chandler N B, Smith J L
Dev Biol. 1985 Aug;110(2):467-79. doi: 10.1016/0012-1606(85)90104-6.
Holmdahl divided vertebrate embryogenesis into two phases called primary and secondary body development. Three primary germ layers are delineated during primary body development and undergo morphogenesis to form primary organ rudiments. In contrast, during secondary body development, the tail bud (a mesenchymal mass of cells located at the caudal end of the embryo and derived principally from Hensen's node) directly forms secondary organ rudiments. We have been testing Holmdahl's concept of primary and secondary body development by mapping the embryonic structures that originate from the tail bud. In the present study, we examined the origins of neural crest cells in caudal regions of avian embryos and observed two populations: primary neural crest cells derived from ectoderm and secondary neural crest cells derived from tail bud. Both types of neural crest cells originate locally, and little or no displacement of these cells occurs along the longitudinal axis. Some secondary neural crest cells seem to colonize the surface epithelium, forming a mosaic derived from both ectoderm and tail bud. Other secondary neural crest cells form spinal ganglia, differentiating as sensory neurons, satellite cells, and Schwann cells. Despite their strikingly different origins and locations, primary and secondary neural crest cells give rise to similar structures.
霍尔姆达尔将脊椎动物胚胎发育分为两个阶段，即初级和次级身体发育。在初级身体发育过程中，三个主要胚层被划定，并经历形态发生形成初级器官原基。相比之下，在次级身体发育过程中，尾芽（位于胚胎尾端的间充质细胞团，主要源自亨森结）直接形成次级器官原基。我们一直在通过绘制源自尾芽的胚胎结构来验证霍尔姆达尔的初级和次级身体发育概念。在本研究中，我们检查了鸟类胚胎尾部区域神经嵴细胞的起源，观察到两个群体：源自外胚层的初级神经嵴细胞和源自尾芽的次级神经嵴细胞。这两种类型的神经嵴细胞均在局部起源，并且这些细胞沿纵轴几乎没有或没有发生位移。一些次级神经嵴细胞似乎定殖于表面上皮，形成一个源自外胚层和尾芽的嵌合体。其他次级神经嵴细胞形成脊髓神经节，分化为感觉神经元、卫星细胞和施万细胞。尽管初级和次级神经嵴细胞的起源和位置截然不同，但它们产生相似的结构。
