Wilson E T, Cretekos C J, Helde K A
Department of Human Genetics, Eccles Institute of Human Genetics, University of Utah, Salt Lake City 84112, USA.
Dev Genet. 1995;17(1):6-15. doi: 10.1002/dvg.1020170103.
Descendants of early blastomeres in the zebrafish come to populate distinctive regions of the fate map. We present a model suggesting that the distribution of cells in the early gastrula (the fate map stage) results from the passive response of cells to reproducible forces that change the overall shape of the blastoderm just prior to gastrulation. We suggest that one of the morphogenetic changes that accompanies epiboly, the upward doming of the yolk cell into the overlying blastoderm, could be responsible for cell mixing. In support of the model, we show that the timing, extent, and directions of cell mixing in the embryo accurately reflect the expectations of the model. Finally, we show that one portion of the gastrula, a marginal region that later gives rise to many of the mesendodermal derivatives, experiences little cell mixing during the doming process. As a result, this region in the gastrula is populated by the descendants of the subset of the early blastomeres that were originally at the margin. The finding that cytoplasm initially at the edge of the 1-celled blastodisc is transmitted specifically to mesendodermal precursors at the fate map stage raises the possibility that maternal determinants may contribute to initiation of embryonic patterning in the zebrafish embryo.
斑马鱼早期卵裂球的后代开始占据命运图的不同区域。我们提出了一个模型，表明早期原肠胚（命运图阶段）中细胞的分布是细胞对可重复力的被动反应的结果，这些力在原肠胚形成之前改变了胚盘的整体形状。我们认为，外包过程中伴随的形态发生变化之一，即卵黄细胞向上隆起进入上覆的胚盘，可能是细胞混合的原因。为支持该模型，我们表明胚胎中细胞混合的时间、程度和方向准确反映了模型的预期。最后，我们表明原肠胚的一部分，即一个边缘区域，后来产生许多中内胚层衍生物，在隆起过程中细胞混合很少。因此，原肠胚中的这个区域由最初位于边缘的早期卵裂球子集的后代占据。在命运图阶段，最初位于单细胞胚盘边缘的细胞质特异性地传递给中内胚层前体，这一发现增加了母体决定因素可能有助于斑马鱼胚胎中胚胎模式形成启动的可能性。
