Tassan Jean-Pierre, Wühr Martin, Hatte Guillaume, Kubiak Jacek
, CNRS UMR 6290, Rennes, France.
Université de Rennes 1, Institut de Génétique et Développement de Rennes, Rennes, France.
Results Probl Cell Differ. 2017;61:243-260. doi: 10.1007/978-3-319-53150-2_11.
Asymmetric cell divisions produce two daughter cells with distinct fate. During embryogenesis, this mechanism is fundamental to build tissues and organs because it generates cell diversity. In adults, it remains crucial to maintain stem cells. The enthusiasm for asymmetric cell division is not only motivated by the beauty of the mechanism and the fundamental questions it raises, but has also very pragmatic reasons. Indeed, misregulation of asymmetric cell divisions is believed to have dramatic consequences potentially leading to pathogenesis such as cancers. In diverse model organisms, asymmetric cell divisions result in two daughter cells, which differ not only by their fate but also in size. This is the case for the early Xenopus laevis embryo, in which the two first embryonic divisions are perpendicular to each other and generate two pairs of blastomeres, which usually differ in size: one pair of blastomeres is smaller than the other. Small blastomeres will produce embryonic dorsal structures, whereas the larger pair will evolve into ventral structures. Here, we present a speculative model on the origin of the asymmetry of this cell division in the Xenopus embryo. We also discuss the apparently coincident asymmetric distribution of cell fate determinants and cell-size asymmetry of the 4-cell stage embryo. Finally, we discuss the asymmetric furrowing during epithelial cell cytokinesis occurring later during Xenopus laevis embryo development.
不对称细胞分裂产生两个具有不同命运的子细胞。在胚胎发育过程中，这种机制对于构建组织和器官至关重要，因为它能产生细胞多样性。在成体中，它对于维持干细胞也仍然至关重要。对不对称细胞分裂的热情不仅源于该机制的美妙以及它所引发的基本问题，还具有非常实际的原因。事实上，不对称细胞分裂的失调被认为会产生严重后果，可能导致诸如癌症等发病机制。在多种模式生物中，不对称细胞分裂会产生两个子细胞，这两个子细胞不仅命运不同，大小也存在差异。非洲爪蟾早期胚胎就是如此，其最初的两次胚胎分裂相互垂直，产生两对通常大小不同的卵裂球：其中一对卵裂球比另一对小。小卵裂球将产生胚胎的背部结构，而较大的那一对将发育成腹部结构。在此，我们提出一个关于非洲爪蟾胚胎中这种细胞分裂不对称性起源的推测模型。我们还讨论了4细胞期胚胎中细胞命运决定因子明显一致的不对称分布以及细胞大小的不对称性。最后，我们讨论了非洲爪蟾胚胎发育后期上皮细胞胞质分裂过程中的不对称沟裂。
