Catala M, Teillet M A, Le Douarin N M
Institut d'Embryologie Cellulaire et Moléculaire du CNRS, Nogent-Sur-Marne, France.
Mech Dev. 1995 May;51(1):51-65. doi: 10.1016/0925-4773(95)00350-a.
After closure of the posterior neuropore, the caudal part of the embryo designated as the 'tail bud' forms a mass of undifferentiated cells from which the lumbosacral and caudal parts of the body develop. It has been proposed that the tail bud is a homogeneous structure comparable to a blastema (Holmdahl, 1925; Griffith et al., 1992). Another view is that morphogenesis of the tail bud is merely the continuation of the gastrulation process (Pasteels, 1937, 1943). In order to try to solve this controversy, we have studied the fate of definite and discrete regions of the tail bud at the 25-somite stage by using the quail-chick marker system. We found that the tail bud is composed of different domains endowed with a definite fate. A ventro-rostral region equivalent to the chordo-neural hinge defined by Pasteels gives rise to the notochord and floor plate and thus corresponds to the Hensen's node which in the tail bud pursues its rostrocaudal movement. The presumptive territory of the lateral walls of the lumbo-sacro-caudal neural tube is located caudally to the Hensen's node as it stands at the 25-somite stage. Material destined to form the sacral and caudal somites is still located in the dorsal midline in the caudalmost part of the tail bud. We thus show that the movements of invagination and divergence which characterize gastrulation are still going on in the tail bud after the 25-somite stage. Thus the somitic material located medio-dorsally diverges laterally and contributes by apposition to the growth of the trunco-caudal part of the body. The parallel between tail bud development in Amniotes and Amphibians as described recently by Gont et al. (1993) is striking and points to the unity in the development mechanisms within the Vertebrate phylum.
后神经孔闭合后，胚胎的尾端部分被称为“尾芽”，它形成了一团未分化的细胞，身体的腰骶部和尾部由此发育而来。有人提出尾芽是一种与芽基类似的同质结构（霍尔姆达尔，1925年；格里菲思等人，1992年）。另一种观点认为尾芽的形态发生仅仅是原肠胚形成过程的延续（帕斯特尔斯，1937年、1943年）。为了试图解决这一争议，我们通过使用鹌鹑 - 鸡标记系统研究了25体节期尾芽特定离散区域的命运。我们发现尾芽由具有特定命运的不同区域组成。与帕斯特尔斯定义的脊索 - 神经铰链相当的腹侧 - 头侧区域产生脊索和底板，因此相当于亨森结，它在尾芽中继续其头尾向运动。腰骶尾神经管侧壁的预定区域在25体节期时位于亨森结的尾侧。注定形成骶骨和尾椎骨节的物质仍位于尾芽最尾端部分的背中线处。因此我们表明，原肠胚形成过程中特有的内陷和分离运动在25体节期之后的尾芽中仍在继续。因此，位于中背侧的体节物质向外侧分离，并通过附着促进身体躯干 - 尾部的生长。冈特等人（1993年）最近描述的羊膜动物和两栖动物尾芽发育之间的相似性非常显著，这表明脊椎动物门内发育机制的统一性。
