Maruyama Yoshihiko K, Shinoda Masaru
Department of Zoology, Faculty of Science, Kyoto University, Sakyo-Ku, Kyoto 606, Japan.
Dev Growth Differ. 1990 Feb;32(1):73-84. doi: 10.1111/j.1440-169X.1990.00073.x.
Starfish blastomeres are reported to be totipotent up to the 8-cell stage. We reinvestigated the development of blastomeres of 8-cell stage embryos with a regular cubic shape consisting of two tiers of 4 blastomeres. On dissociation of the embryo by disrupting the fertilization membrane at the 8-cell stage, each of the 4 blastomeres of the vegetal hemisphere gave rise to an embryo that gastrulated, whereas blastomeres from the animal hemisphere did not. By injection of a cell lineage tracer into blastomeres of 8-cell stage embryos, we found that only those of the vegetal hemisphere formed cells constituting the archenteron. Next, we compressed 4-cell stage embryos along the animal-vegetal axis so that all the blastomeres in the 8-cell stage were in a single layer. When these 8 blastomeres were then dissociated, an average of 7 of them developed into gastrulae. By cell lineage analysis, all the blastomeres in single-layered embryos at the 8-cell stage were shown to have the capacity to form cells constituting an archenteron. Taken together, these findings indicate that the fate to form the archenteron is specified by a cytoplasmic factor(s) localized at the vegetal hemisphere, and that isolated blastomeres that have inherited this factor develop into gastrulae.
据报道，海星的卵裂球在8细胞阶段之前都是全能的。我们重新研究了呈规则立方体形状、由两层4个卵裂球组成的8细胞期胚胎卵裂球的发育情况。在8细胞阶段通过破坏受精膜使胚胎解离时，植物半球的4个卵裂球每个都发育成了一个进行原肠胚形成的胚胎，而动物半球的卵裂球则没有。通过将细胞谱系示踪剂注入8细胞期胚胎的卵裂球中，我们发现只有植物半球的卵裂球形成了构成原肠的细胞。接下来，我们沿着动物 - 植物轴压缩4细胞期胚胎，使8细胞期的所有卵裂球都处于单层。当然后将这8个卵裂球解离时，平均有7个发育成了原肠胚。通过细胞谱系分析表明，8细胞期单层胚胎中的所有卵裂球都具有形成构成原肠的细胞的能力。综上所述，这些发现表明形成原肠的命运是由位于植物半球的一种或多种细胞质因子决定的，并且继承了这种因子的分离卵裂球会发育成原肠胚。
