Lipid rafts enriched in monosialylGb5Cer carrying the stage-specific embryonic antigen-4 epitope are involved in development of mouse preimplantation embryos at cleavage stage

Here we show that monosialylGb5Cer (MSGb5Cer)-enriched raft domains are involved in development during the cleavage stage of mouse preimplantation embryos. MSGb5Cer preferentially localizes at the interfaces between blastomeres in mouse preimplantation embryos. Live-imaging analysis revealed that MSGb5Cer localizes in cleavage furrows during cytokinesis, and that by accumulating at the interfaces, it thickens them. Depletion of cholesterol from the cell membrane with methyl-beta-cyclodextrin (MbCD) reduced the expression of MSGb5Cer and stopped cleavage. Extensive accumulation of MSGb5Cer at the interfaces by cross-linking with anti-MSGb5Cer Mab (6E2) caused F-actin to aggregate at the interfaces and suppressed the localization of E-cadherin at the interfaces, which resulted in the cessation of cleavage. In addition, suppression of actin polymerization with cytochalasin D (CCD) decreased the accumulation of MSGb5Cer at the interfaces. In E-cadherin-targeted embryos, the MSGb5Cer-enriched raft membrane domains accumulated heterotopically.These results indicate that MSGb5Cer-enriched raft membrane domains participate in cytokinesis in a close cooperation with the cortical actin network and the distribution of E-cadherin.The molecular dynamics involved in embryogenesis is now being elucidated. In the early cleavage stage of embryogenesis, the localization of cell surface molecules periodically changes and is spatio-temporally controlled. Cytokinesis is a fundamental process of cell cleavage in which the daughter cells split after nuclear division, and it is driven by actin-dependent narrowing of a contractile ring as well as furrow-specific addition of membrane [1,2]. The latter contributes to dynamic rearrangement of cell surface proteins and provides molecules required to construct the complex machinery of cytokinesis. For example, the cell surface adhesion molecule E-cadherin is drastically rearranged in a close correlation with the dynamics of cortical actin [3]. I