Gimlich R L, Gerhart J C
Dev Biol. 1984 Jul;104(1):117-30. doi: 10.1016/0012-1606(84)90042-3.
We have attempted to define the location and mode of action of axial determinants in the egg of Xenopus laevis. To this end, we transplanted small numbers of blastomeres from normal 64-cell stage embryos into synchronous recipient embryos which had been irradiated with ultraviolet light prior to first cleavage. Without transplantation, such embryos fail to develop dorsal structures of the embryonic body axis. We found that one to three blastomeres transplanted from the vegetal-most octet of cells can effect complete or partial rescue of of axis development in a recipient, provided that the donor cells derive from the quadrant just under the prospective dorsal marginal region. These same cells, when transplanted into the ventral vegetal quadrant of a normal 64-cell embryo, cause the formation of a complete second body axis. In contrast, other cells from the vegetal octet of normal donors fail to cause axis formation. When the rescuing donor cells are labeled with a lineage-restricted fluorescent marker, we find that their progeny do not contribute to the axial structures of the recipient. Progeny of the transplanted cells are found below the level of the blastopore in the early gastrula and eventually give rise to portions of the gut, as is their fate in normal development. These results, in agreement with those of Nieuwkoop (P.D. Nieuwkoop, 1977, Curr. Top. Dev. Biol. 11, 115-132), imply that the dorsal-most vegetal cells of the 64-cell embryo receive from the egg cytoplasm a set of determinants enabling them to induce neighboring cells to undertake axis formation. We discuss the relationship between axis induction in rescued irradiated embryos and axis determining processes in normal embryogenesis.
我们试图确定非洲爪蟾卵中轴向决定因素的位置和作用方式。为此，我们将少量来自正常64细胞期胚胎的卵裂球移植到同步的受体胚胎中，这些受体胚胎在第一次卵裂前已用紫外线照射。未经移植的话，此类胚胎无法发育出胚胎体轴的背侧结构。我们发现，从最植物极的八个细胞中移植一到三个卵裂球，能够实现受体胚胎轴发育的完全或部分挽救，前提是供体细胞来自紧邻预期背侧边缘区域下方的象限。同样的这些细胞，当被移植到正常64细胞胚胎的腹侧植物象限中时，会导致形成完整的第二条体轴。相比之下，来自正常供体植物极八个细胞中的其他细胞则无法导致轴的形成。当用谱系限制荧光标记物标记挽救性供体细胞时，我们发现它们的后代对受体的轴向结构没有贡献。在早期原肠胚中，移植细胞的后代位于胚孔水平以下，最终发育成肠道的一部分，这与它们在正常发育中的命运相同。这些结果与尼乌科普（P.D. 尼乌科普，1977年，《发育生物学当前主题》第11卷，第115 - 132页）的结果一致，表明64细胞胚胎最背侧的植物细胞从卵细胞质中接收了一组决定因素，使它们能够诱导相邻细胞进行轴的形成。我们讨论了挽救后的辐照胚胎中的轴诱导与正常胚胎发生中的轴决定过程之间的关系。
