Abstract
E-cadherin is a member of the cadherin superfamily of calcium-dependent cell adhesion molecules, and has critical roles in cell adhesion during early embryo development. To determine the expression and distribution of E-cadherin, we applied immunofluorescent staining on late 8 cell, morula and blastocyst stage embryos during the experiments. Firstly, we superovulated the females and sacrificed them to isolate oviducts. We flushed 2 cell embryos by using FHM HEPES-buffered medium from the CD1 female mouse oviducts and cultured them in KSOM medium until the blastocyst stage. Embryos were fixed and immunostained with E-cadherin, then images were assessed using a fluorescence microscope. We demonstrate that E-cadherin is expressed throughout the late 8 cell to fully expanded blastocysts. We observed that E-cadherin is present only in the cell-cell contact sites and not in the apical sites of the membrane of late 8 cell stage embryo. In morula, E-cadherin localized on the surface of blastomeres and cell-cell junctions. In blastocyst stage, embryos showed membrane staining in cell-cell contact regions in trophectoderm cells while localized on the surface of inner cell mass. Our results indicate that E-cadherin mediated cell adhesion has major roles on compaction, trophectoderm epithelial differentation and implantation.
Highlights
Cell adhesion molecules have a fundamental importance in early mouse embryo because of their roles in mediating cell-cell interactions during subsequent development (Fleming TP, 2001)
The expression of E-cadherin was determined during preimplantation embryo development by immunofluorescence staining from late 8 cell stage to the blastocyst stage
We showed that E-cadherin protein is entirely localized around the internal blastomeres membrane and is present in cell-cell contact sites of adjacent external blastomeres in morula (Figure 1B)
Summary
Cell adhesion molecules have a fundamental importance in early mouse embryo because of their roles in mediating cell-cell interactions during subsequent development (Fleming TP, 2001). E-cadherin has a major role on the adhesion of blastomeres during preimplantation mammalian embryo development [14]. As a result of compaction, adherens junctions form at the cell-to-cell contact sites, forming the embryo called morula. The TE is a single outer layer of polarized epithelial cells which mediates the implantation of the embryo and contributes to placentation, while ICM is composed of pluripotent unpolarized cells that give rise to the fetus [13]. By the E4.5 (embryonic day 4.5) blastocyst (fully expanded blastocyst) stage, ICM cells are segregated into two distinct cell layers called primitive endoderm (PrE) and pluripotent epiblast (Epi) that gives rise to visceral and parietal endoderm and most of the cells of the embryo proper respectively [7]
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