The cellular basis of epiboly: an SEM study of deep-cell rearrangement during gastrulation in Xenopus laevis.
The cellular basis of epiboly: an SEM study of deep-cell rearrangement during gastrulation in Xenopus laevis.
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发表时间：
1980-12
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通讯作者：
R. Keller
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作者：
R. Keller
为了描述在背侧边缘区伸展和动物区外包过程中，原肠胚深部区域面积增加所涉及的细胞过程，我们从精心分期的破碎胚胎的扫描电子显微照片中，对晚期囊胚和原肠胚中深部细胞的形状、接触、位置和排列的若干指标进行了测量。在原肠胚形成开始时，背侧边缘区的深部细胞变长，沿着胚胎半径在彼此之间伸出突起，并相互交错，在径向交错过程中形成面积更大但层数更少的细胞层。当交错完成时，深部区域由一层柱状细胞组成，这些细胞随后变扁并扩散，从而使深部区域的面积进一步增加。在动物区外包过程中，也会发生交错，细胞层数减少，但没有出现背侧边缘区那样的细胞形状变化。这些差异可能与背侧边缘区的扩张（伸展和汇聚）各向异性有关，而动物区是均匀扩散；或者它们可能反映了背侧边缘区的细胞主动运动，而动物区是被动行为。我们提出了一个细胞和力学模型，其中主动（自主）扩散是由深部细胞主动产生力的交错以及随后的扁平化所导致的。还提出了一个被动扩散（拉伸）模型。这些观察结果提示了一些实验，这些实验将确定细胞行为与原肠胚形成力学之间的关系。
Measurements of several indices of shape, contact, position and arrangement of deep cells in the late blastula and gastrula were made from scanning electron micrographs of carefully staged, fractured embryos in order to describe the cellular processes which account for the increased area of the deep region of the gastrula during extension of the dorsal marginal zone and epiboly of the animal region. At the onset of gastrulation, the deep cells of the dorsal marginal zone become elongated, extend protrusions between one another along radii of the embryo and interdigitate to form fewer layers of cells of greater area in a process of radial interdigitation. When interdigitation, is complete, the deep region consists of one layer of columnar cells which then flatten and spread and thus account for additional increase in area of the deep region. During epiboly of the animal region, interdigitation occurs and the number of cell layers decreases without the changes in cell shape seen in the dorsal marginal zone. These differences may be related to the anisotropy of expansion (extension and convergence) in the dorsal marginal done as opposed to uniform spreading in the animals region, or they may reflect an active cell motility in the dorsal marginal zone as opposed to a passive behavior in the animal region. A cellular and mechanical model is presented in which active (autonomous) spreading is brought about by active, force-producing interdigitation and subsequent flattening of deep cells. A model of passive spreading (stretching) is also presented. These observations suggest experiments that would determine the relationship of cell behavior to the mechanics of gastrulation.