Cell surface changes in preimplantation mouse embryos during compaction investigated using FITC conjugated lectins after proteolytic enzyme treatment

Summary Fluorescein-conjugated lectins were used to examine the reappearance of glycoproteins on the surface of 8-cell mouse embryos after treatment with proteolytic enzymes. Embryos were decompacted in calcium free medium, treated with various proteases and the process of recompaction monitored. The most effective enzymes in delaying recompaction were subtilopeptidase A and proteinase K at 1 mg/ml; the initiation of recompaction was delayed by about 5 h and 90% recompaction by 14–18 h. Papain and -chymotrypsin were only effective in the absence of calcium. The reappearance of receptors for fluorescein-conjugated Con-A, MPA, RCA-I, FBP, BSL-II and DBA was examined photometrically at 0,8–10 and 17–18 h after proteinase K treatment. There was an increase in binding of MPA, RCA-I, FBP and BSL-II in control embryos during the period of the experiment, between approx. 61 and 80 h post coitum in which embryos passed from the 8-cell stage to the 16–32 cell stage. Con-A binding remained the same and that of DBA decreased. By the time that 50% of enzyme treated embryos had recompacted (8–10 h) binding of Con-A was similar to control embryos. Binding of FBP had almost reached control levels while that of BSL-II, DBA, RCA-I and MPA had reached 60–85% of control levels. When embryos were fully compact (17–18 h) Con-A, FBP and DBA were bound in equal or slightly greater amounts to enzyme treated as to control embryos, and receptors for BSL-II, MPA and RCA-I had recovered almost to control levels. The results clearly show that the recovery of glycoproteins on the surface of 8–16 cell embryos parallels recompaction, providing further evidence for the role of these molecules in compaction.