Gimlich R L
Dev Biol. 1986 Jun;115(2):340-52. doi: 10.1016/0012-1606(86)90254-x.
This paper describes a continuing effort to define the location and mode of action of morphogenetic determinants which direct the development of dorsal body axis structures in embryos of the frog Xenopus laevis. Earlier results demonstrated that presumptive endodermal cells in one vegetal quadrant of the 64-cell embryo can, under certain experimental conditions, induce partial or complete body axis formation by progeny of adjacent equatorial cells. (R.L. Gimlich and J.C. Gerhart, 1984, Dev. Biol. 104, 117-130). I have now assessed the importance of other blastomeres for embryonic axis formation in a series of transplantation experiments using cells from the equatorial level of the 32-cell embryo. The transplant recipients were embryos which had been irradiated with ultraviolet light before first cleavage. Without transplantation, embryos failed to develop the dorsal structures of the embryonic body axis. However, cells of these recipients were competent to respond to inductive signals from transplanted tissue and to participate in normal embryogenesis. Dorsal equatorial cells, but not their lateral or ventral counterparts, often caused partial or complete body axis development in irradiated recipients, and themselves formed much of the notochord and some prechordal and somitic mesoderm. These are the same structures that they would have formed in the normal donor. Thus, the dorsal equatorial blastomeres were often at least partially autonomous in developing according to their prospective fates. In addition, they induced progeny of neighboring host cells to contribute to the axial mesoderm and to form most of the central nervous system. The frequency with which such transplants caused complete axis formation in irradiated hosts increased when they were made at later and later cleavage stages. In contrast, the inductive activity of vegetal cells remained the same or declined during the cleavage period. These and other results suggest that the egg cytoplasmic region containing "axial determinants" is distributed to both endodermal and mesodermal precursors in the dorsal-most quadrant of the early blastula.
本文描述了一项持续的研究工作，旨在确定形态发生决定因素的位置和作用方式，这些因素指导非洲爪蟾胚胎中背体轴结构的发育。早期结果表明，在64细胞胚胎的一个植物象限中的预定内胚层细胞，在某些实验条件下，可以诱导相邻赤道细胞的后代形成部分或完整的体轴。（R.L. Gimlich和J.C. Gerhart，1984年，《发育生物学》104卷，117 - 130页）。我现在通过一系列移植实验评估了其他卵裂球对胚胎轴形成的重要性，这些实验使用了来自32细胞胚胎赤道水平的细胞。移植受体是在第一次卵裂前用紫外线照射过的胚胎。未经移植，胚胎无法发育出胚胎体轴的背侧结构。然而，这些受体的细胞能够对来自移植组织的诱导信号作出反应，并参与正常的胚胎发生。背侧赤道细胞，而不是它们的外侧或腹侧对应细胞，常常在受照射的受体中引起部分或完整的体轴发育，并且它们自身形成了大部分脊索以及一些脊索前和体节中胚层。这些与它们在正常供体中会形成的结构相同。因此，背侧赤道卵裂球在根据其预期命运发育时通常至少部分是自主的。此外，它们诱导相邻宿主细胞的后代参与轴向中胚层的形成，并形成大部分中枢神经系统。当在越来越晚的卵裂阶段进行这种移植时，它们在受照射宿主中导致完整轴形成的频率增加。相比之下，植物细胞的诱导活性在卵裂期保持不变或下降。这些以及其他结果表明，含有“轴向决定因素”的卵细胞质区域在早期囊胚最背侧象限中被分配到内胚层和中胚层前体。
