Fucosylated glycoconjugates in mouse preimplantation embryos

Preimplantation mouse embryos were metabolically labelled with 3H or 14C-fucose to investigate the synthesis of fucosylated macromolecules. Scintillation counting revealed that there was a progressive increase in both total fucose taken up by the embryo and incorporation of fucose into TCA-precipitable material as embryos developed from the 4-cell to the blastocyst stage. This was reflected in the increasing intensity of bands on autoradiographs of radioactive fucose labelled proteins separated on 10% SDS-PAGs between the 4-cell embryo (at which stage bands were first detectable) and the blastocyst. Minor qualitative changes in fucoproteins were detected at the time of compaction and additional bands appeared at the blastocyst stage. Preliminary analysis of fucolipids in 6- to 8-cell embryos indicated that an approximately equal amount of fucose was incorporated into lipid and protein. Autoradiographs of semi-thin sections of 3H-fucose-labelled embryos showed substantial amounts of radioactive material in the vicinity of the plasma membrane both adjacent to other cells and facing the zona pellucida. These data would support a predominant role for fucoconjugates in cell surface events in the preimplantation embryo from the 8-cell stage.