Latimer J J, Hultner M L, Cleaver J E, Pedersen R A
Laboratory of Radiobiology and Environmental Health, University of California, San Francisco 94143, USA.
Exp Cell Res. 1996 Oct 10;228(1):19-28. doi: 10.1006/excr.1996.0294.
In order to determine whether there is differential cell-type-specific DNA repair we measured the nucleotide excision repair capacity of the four distinct cell lineages that comprise the extraembryonic yolk sac using the unscheduled DNA synthesis assay. Yolk sacs from mouse embryos at 11.5-12.5 days gestation were microdissected to yield purified trophoblast, parietal endoderm, mesoderm, and visceral endoderm, as well as fetal skin fibroblasts which were then grown as primary explants. At this midgestational stage of development, the yolk sac provides essential functions for the sustenance of the embryo while the complex process of organogenesis is proceeding in the liver, kidney, and gut. Trophoblast giant cells, parietal endoderm, and visceral endoderm all demonstrated low levels of unscheduled DNA synthesis consistent with levels measured in adult mouse skin fibroblasts. As has previously been documented, embryonic mouse skin fibroblasts were reproducibly 2- to 3-fold higher than adult mouse skin fibroblasts in levels of DNA excision repair. The extraembryonic mesoderm, however, displayed a statistically significant level of unscheduled DNA synthesis 10-fold higher than adult mouse skin fibroblasts or the other lineages of the midgestation yolk sac. Further, the S-indexes of these lineages were also determined to assess the possible relevance of differential repair to the proliferative status of the cells. These data demonstrate that DNA excision repair capacity is lineage-specific during embryogenesis in the mouse. These studies may begin to provide a context for understanding the perplexing developmental aspects such as the characteristic congenital abnormalities associated with the human heritable DNA repair deficiency diseases.
为了确定是否存在细胞类型特异性的DNA修复差异，我们使用非预定DNA合成试验测量了构成胚外卵黄囊的四种不同细胞谱系的核苷酸切除修复能力。对妊娠11.5 - 12.5天的小鼠胚胎的卵黄囊进行显微解剖，以获得纯化的滋养层、壁内胚层、中胚层和脏内胚层，以及胎儿皮肤成纤维细胞，然后将其作为原代外植体培养。在这个发育的中期阶段，卵黄囊为胚胎的维持提供重要功能，而肝脏、肾脏和肠道的器官发生复杂过程正在进行。滋养层巨细胞、壁内胚层和脏内胚层均显示出低水平的非预定DNA合成，这与成年小鼠皮肤成纤维细胞中测量的水平一致。如先前所述，胚胎小鼠皮肤成纤维细胞的DNA切除修复水平比成年小鼠皮肤成纤维细胞高2至3倍。然而，胚外中胚层显示出统计学上显著的非预定DNA合成水平，比成年小鼠皮肤成纤维细胞或中期妊娠卵黄囊的其他谱系高10倍。此外，还确定了这些谱系的S指数，以评估差异修复与细胞增殖状态的可能相关性。这些数据表明，在小鼠胚胎发育过程中，DNA切除修复能力是谱系特异性的。这些研究可能开始为理解令人困惑的发育方面提供背景，例如与人类遗传性DNA修复缺陷疾病相关的特征性先天性异常。
