Gardner R L, Cockroft D L
Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK.
Development. 1998 Jul;125(13):2397-402. doi: 10.1242/dev.125.13.2397.
Observations on chimaeric mice argue that there must be considerable dispersal and intermingling of the clonal descendants of epiblast founder cells at an early stage in the development of the tissue. However, it has not been established when or how this occurs. Here we have used a genetic marker that enables donor cells to be visualized in situ to examine the early postimplantation distribution of clones obtained by transplanting epiblast founder cells into host blastocysts. We have also determined the spatial relationship between sister cells in non-chimaeric postimplantation epiblast by ionophoretic injection of a fluorescent macromolecule. Both experimental approaches support the conclusion that breakdown of coherent clonal growth accompanies epithelialization of the epiblast and is essentially complete by the onset of gastrulation. Furthermore, the clonal analysis shows that descendants of different epiblast founder cells continue to intermingle extensively well into organogenesis. We suggest that this sustained intermingling of cells in the epithelial epiblast, which does not occur in the adjacent visceral endoderm, depends on cells losing contact with the basal lamina when they divide. These findings have implications both for patterning of the early amniote embryo and for the growth of tall columnar epithelia in general.
对嵌合小鼠的观察结果表明，在组织发育的早期阶段，上胚层原始细胞的克隆后代之间必定存在相当程度的分散和混合。然而，目前尚未确定这种情况何时发生以及如何发生。在这里，我们使用了一种遗传标记，能够在原位观察供体细胞，以研究将上胚层原始细胞移植到宿主囊胚后获得的克隆在植入后的早期分布情况。我们还通过离子电渗法注射荧光大分子，确定了非嵌合植入后上胚层中姐妹细胞之间的空间关系。这两种实验方法均支持以下结论：连贯的克隆生长的瓦解伴随着上胚层的上皮化，并且在原肠胚形成开始时基本完成。此外，克隆分析表明，不同上胚层原始细胞的后代在器官发生过程中仍会广泛地继续混合。我们认为，上皮性上胚层中细胞的这种持续混合，在相邻的脏内胚层中不会发生，这取决于细胞在分裂时与基膜失去接触。这些发现对早期羊膜动物胚胎的模式形成以及一般的高柱状上皮的生长都有影响。
