Sanders E J, Torkkeli P H, French A S
Department of Physiology, University of Alberta, Edmonton, Canada.
Anat Embryol (Berl). 1997 Feb;195(2):147-54. doi: 10.1007/s004290050033.
We have examined the distribution of cells at an early stage of the cell death process in gastrulating chick and mouse embryos, using a DNA nick end-labelling technique to label nuclei that are undergoing DNA fragmentation in situ. In the chick embryo, the incidence of nuclei showing DNA fragmentation was mapped by digitizing the occurrence of these nuclei from sections, and reconstructing the three separate layers of the entire embryo at several stages of gastrulation. In the chick, DNA fragmentation was found in nuclei throughout the embryo, in cells of all three germ layers, but most especially in the epiblast in the rostral germinal crescent and in the lateral marginal zones. This region of greatest cell death formed an arc rostrally and laterally in the epiblast, and was consistent through gastrulation and into the early neurulation stage. While the extensive cell death in the chick embryo may be due to cell redundancy, it is also possible that the pattern of death observed could be related to the compression of the embryo against the barrier of yolk at the periphery of the area pellucida during expansion. In a number of cases in the chick, local regions of elevated cell death were also observed in the primitive streak. This may be associated with the changing cell-cell and cell-matrix interactions experienced by cells traversing the primitive streak. In the gastrulating mouse embryo, by contrast, nuclei undergoing DNA fragmentation showed no consistent regions of elevated incidence, in any of the embryonic layers. DNA fragmentation in these embryos was, however, observed in nuclei of cells in the visceral endoderm and in the epiblast. The lack of any clear pattern of DNA fragmentation in the mouse embryo at this stage of development leaves the roles of the dying cells enigmatic. The death may, however, be lineage-related or be a reflection of a cellular redundancy necessary in a developing system that is undergoing extensive cell rearrangement and cellular adhesive change.
我们利用DNA缺口末端标记技术对原肠胚形成期的鸡胚和鼠胚细胞死亡过程早期的细胞分布进行了研究，该技术用于原位标记正在经历DNA片段化的细胞核。在鸡胚中，通过数字化切片中这些细胞核的出现情况，并在原肠胚形成的几个阶段重建整个胚胎的三个独立层，来绘制显示DNA片段化的细胞核的发生率。在鸡胚中，DNA片段化存在于整个胚胎的细胞核中，存在于所有三个胚层的细胞中，但最明显的是在头侧生发新月区的上胚层和侧缘区。这个细胞死亡最严重的区域在上胚层中形成了一个从头部到侧面的弧形，并且在原肠胚形成期一直持续到早期神经胚形成阶段。虽然鸡胚中广泛的细胞死亡可能是由于细胞冗余，但也有可能观察到的死亡模式与胚胎在透明带区域扩张过程中受到卵黄屏障挤压有关。在鸡胚的一些情况下，在原条中也观察到局部细胞死亡增加的区域。这可能与穿越原条的细胞所经历的细胞间和细胞与基质相互作用的变化有关。相比之下，在原肠胚形成期的鼠胚中，经历DNA片段化的细胞核在任何胚胎层中都没有显示出一致的发生率升高区域。然而，在这些胚胎中，在内脏内胚层和上胚层的细胞核中观察到了DNA片段化。在这个发育阶段，鼠胚中缺乏任何明显的DNA片段化模式，使得死亡细胞的作用难以捉摸。然而，这种死亡可能与细胞谱系有关，或者反映了一个正在经历广泛细胞重排和细胞黏附变化的发育系统中必要的细胞冗余。
