Spreading of blastomeres from eight-cell mouse embryos on lectin-coated beads

Single blastomeres from 8-cell embryos adhere to lectin-coated agarose beads. The cells spread over the surface of peanut lectin (PNA), wheat germ lectin (WGA) and concanavalin A (Con A)-coated agarose beads, and this was prevented by sugars with high affinity for the appropriate lectin. Spreading was also prevented by cytochalasin D at a concentration (0.5-1.0 microgram/ml) known to inhibit compaction of whole 8-cell embryos. Colcemid (1-2 micrograms/ml) only depressed spreading, as measured by linear contact distance, to 70-80% of that for the controls, while removal of calcium from the medium with EDTA had little effect on spreading. Fucose promoted spreading on WGA beads. Cells from 8-cell embryos will not adhere to negatively charged G-Sephadex and CM-Sephadex beads. They do adhere to positively charged DEAE-Sephadex beads but do not spread on them. In an attempt to inhibit cell spreading at compaction in intact 8-cell embryos, these were disaggregated in the presence of various (34) saccharide-containing molecules. Neither any sugar-containing molecules alone, nor combinations of N-acetyl-glucosamine, galactose and mannose, fucose and galactose, and fucose and lactose were able to inhibit compaction at physiological concentrations. However, blastocyst formation was inhibited to various extents by high nonphysiological concentrations (50 mM) of D-glucose, D-mannose, L-fucose, D-arabinose, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, alpha-lactose, 25 mM-alpha-melibionic acid and by 2 mg/ml fucoidin, ovine mucin and desialylated ovine mucin. Our results indicate that interaction of PNA, WGA and Con A with molecules on the cell surface that bind these lectins can trigger the cells to spread. However, a simple lectin-sugar interaction alone may not account for the spreading of cells on one another at compaction in whole 8-cell embryos.