Gurdon J B, Mohun T J, Fairman S, Brennan S
Proc Natl Acad Sci U S A. 1985 Jan;82(1):139-43. doi: 10.1073/pnas.82.1.139.
Fertilized Xenopus eggs have been ligated with a hair loop into separate fragments before the first cleavage. The plane of the ligation was varied in relation to the animal-vegetal and dorso-ventral axes. The fragments that contained a nucleus were cultured for 24 hr until controls reached the neurula stage; they were then analyzed by S1 nuclease protection for their content of muscle-specific actin mRNA, using a gene-specific probe. We find that all egg components required for the eventual activation of these actin genes are localized, already at the 1-cell stage, in a region below the equator, and mostly on the dorsal (grey crescent) side. This material subsequently occupies the equivalent position in 8-cell and 32-cell embryos. We interpret our results, in combination with the previous work of others, to mean that mesoderm (including muscle) formation in Amphibia depends both on cytoplasmic substances already localized in the egg as well as on inductive cell interactions during cleavage.
在第一次卵裂之前，用毛发环将受精的非洲爪蟾卵结扎成单独的片段。结扎平面相对于动物-植物轴和背-腹轴而变化。含有细胞核的片段培养24小时，直到对照胚胎达到神经胚阶段；然后使用基因特异性探针通过S1核酸酶保护分析它们的肌肉特异性肌动蛋白mRNA含量。我们发现，这些肌动蛋白基因最终激活所需的所有卵成分在1细胞阶段就已定位在赤道下方的区域，并且大多位于背侧（灰色新月区）。该物质随后在8细胞和32细胞胚胎中占据相应位置。我们结合其他人之前的工作来解释我们的结果，即两栖动物中胚层（包括肌肉）的形成既依赖于卵中已经定位的细胞质物质，也依赖于卵裂期间的诱导性细胞相互作用。
