Cell surface carbohydrates and lectins in early development

Current knowledge on the development regulation of cell surface carbohydrates and lectins in mammalian embryos is summarized. Much of this data comes from observations on mouse embryos but information on the human embryo is included where it is available. Over the last few years, numerous studies have indicated that carbohydrates play a critical role in the cell-cell interactions of the pre-and peri-implantation embryo. Functional tests suggest a role for terminal fucosylated Gal beta 1-3/4GlcNAc structures in the early steps of implantation. We also now have clear evidence for the expression of lectins in the trophectoderm just prior to implantation. Mouse mutants have been generated which lack particular enzymes involved in glycosylation or particular lectins, but so far they have not been informative about the role of glycoconjugates or lectins in the very early embryo.