Rastan S, Thorpe S J, Scudder P, Brown S, Gooi H C, Feizi T
J Embryol Exp Morphol. 1985 Jun;87:115-28.
Roles of cell surface carbohydrates containing the 3-fucosyl-N-acetyllactosamine and poly-N-acetyllactosamine sequences (SSEA-1 and I antigens, respectively) in the compaction of mouse embryos have been investigated using the endo-beta-galactosidase of Bacteroides fragilis to modify the surface of cleavage-stage embryos. Treatment with this enzyme abolished SSEA-1 activity and diminished I antigen activity on the embryonic cell surface. Embryos cultured in the presence of endo-beta-galactosidase from the 2- to 4-cell stage onwards, or treated with the enzyme at the compacting 8-cell stage, continued to compact and proceeded to form blastocysts at the normal rate. However, when compacted 8- to 16-cell embryos were experimentally decompacted in calcium-free medium, treated for 1 h with endo-beta-galactosidase and returned to normal culture medium, the time taken for 50% of the embryos to recompact was prolonged five-fold. There was an even greater delay if these embryos were maintained in culture medium containing the enzyme. Blastocysts were eventually formed under both conditions. Thus, endo-beta-galactosidase did not affect compaction unless the embryos were first decompacted. On the assumption that recompaction and de novo compaction occur by similar mechanisms, we propose that carbohydrate-binding molecules are involved which have high affinities for poly-N-acetyllactosamine structures and protect them from digestion by endo-beta-galactosidase.
利用脆弱拟杆菌的β-半乳糖苷内切酶修饰卵裂期胚胎的表面，研究了含有3-岩藻糖基-N-乙酰乳糖胺和多-N-乙酰乳糖胺序列（分别为阶段特异性胚胎抗原-1和I抗原）的细胞表面碳水化合物在小鼠胚胎致密化中的作用。用这种酶处理可消除胚胎细胞表面的阶段特异性胚胎抗原-1活性并降低I抗原活性。从2-细胞期开始在β-半乳糖苷内切酶存在下培养的胚胎，或在致密化的8-细胞期用该酶处理的胚胎，继续致密化并以正常速率发育成囊胚。然而，当将致密化的8-16细胞胚胎在无钙培养基中实验性地解聚，用β-半乳糖苷内切酶处理1小时后再放回正常培养基中时，50%的胚胎重新致密化所需的时间延长了五倍。如果将这些胚胎置于含有该酶的培养基中培养，延迟会更大。在这两种情况下最终都形成了囊胚。因此，除非胚胎首先解聚，β-半乳糖苷内切酶不会影响致密化。基于重新致密化和从头致密化通过相似机制发生的假设，我们提出碳水化合物结合分子参与其中，这些分子对多-N-乙酰乳糖胺结构具有高亲和力，并保护它们不被β-半乳糖苷内切酶消化。
