Zetter B R, Martin G R
Proc Natl Acad Sci U S A. 1978 May;75(5):2324-8. doi: 10.1073/pnas.75.5.2324.
The expression of a high molecular weight cell surface glycoprotein (LETS, fibronectin) by preimplantation mouse embryos as well as cultured teratocarcinoma stem cells was detected by using indirect immunofluorescent staining. When each stage of preimplantation embryonic development was tested for the presence of LETS protein, none was observed on two-cell, four-cell, or eight-cell embryos, or on the morula or the outer cell layer (trophectoderm) of the early or late blastocyst. However, when the inner cell mass was isolated by immunosurgery, positive staining was observed. The intensity of the staining was significantly greater on the inner cell mass isolated from the expanded (day 4) blastocyst than on that from the early (day 3) blastocyst. Certain established cell lines of teratocarcinoma stem cells (embryonal carcinoma cells) also express cell surface LETS protein. "Nullipotent" (Nulli-SCC-1) as well as pluripotent (PSA 1) embryonal carcinoma cell lines have deposits of LETS protein concentrated in areas of cell-cell contact. In addition, a teratocarcinoma-derived endodermal cell line (PYS) was found to be capable of depositing LETS onto the substratum in a fibrillar network.Taken together, our results indicate that LETS protein is synthesized at a specific stage of preimplantation mouse embryonic development. In particular, they suggest that LETS protein is a product of the embryonic ectoderm, and that some types of embryonic endoderm are also capable of synthesizing this protein.
通过间接免疫荧光染色检测了植入前小鼠胚胎以及培养的畸胎瘤干细胞中高分子量细胞表面糖蛋白（LETS，纤连蛋白）的表达。当检测植入前胚胎发育的各个阶段是否存在LETS蛋白时，在二细胞、四细胞或八细胞胚胎，或桑葚胚、早期或晚期囊胚的外层细胞（滋养外胚层）上均未观察到。然而，当通过免疫手术分离内细胞团时，观察到阳性染色。从扩张期（第4天）囊胚分离的内细胞团的染色强度明显大于从早期（第3天）囊胚分离的内细胞团。某些已建立的畸胎瘤干细胞系（胚胎癌细胞）也表达细胞表面LETS蛋白。“无潜能”（Nulli-SCC-1）以及多能（PSA 1）胚胎癌细胞系的LETS蛋白沉积物集中在细胞间接触区域。此外，发现一种源自畸胎瘤的内胚层细胞系（PYS）能够在纤维状网络中将LETS沉积到基质上。综上所述，我们的结果表明LETS蛋白是在植入前小鼠胚胎发育的特定阶段合成的。特别是，它们表明LETS蛋白是胚胎外胚层的产物，并且某些类型的胚胎内胚层也能够合成这种蛋白。
