β-catenin is a molecular switch that regulates transition of cell-cell adhesion to fusion

Abstract

When a sperm and an oocyte unite upon fertilization, their cell membranes adhere and fuse, but little is known about the factors regulating sperm-oocyte adhesion. Here we explored the role of β-catenin in sperm-oocyte adhesion. Biochemical analysis revealed that E-cadherin and β-catenin formed a complex in oocytes and also in sperm. Sperm-oocyte adhesion was impaired when β-catenin-deficient oocytes were inseminated with sperm. Furthermore, expression of β-catenin decreased from the sperm head and the site of an oocyte to which a sperm adheres after completion of sperm-oocyte adhesion. UBE1-41, an inhibitor of ubiquitin-activating enzyme 1, inhibited the degradation of β-catenin, and reduced the fusing ability of wild-type (but not β-catenin-deficient) oocytes. These results indicate that β-catenin is not only involved in membrane adhesion, but also in the transition to membrane fusion upon fertilization.

Requirement of the transcription factor USF1 in bovine oocyte and early embryonic development

“…High abundance of TWIST2 transcript at MII stage in oocytes and 4–8 cell embryonic stage suggests a potential regulatory role in control of genes associated with maturation and initial cleavage divisions during early embryonic development. Interestingly, many of the mammalian target genes for TWIST2 includes cell adhesion molecules (E-cadherin and fibronectin) and transcription factors (beta-catenin and STAT3) (Fang et al 2011), genes involved in sperm and oocyte fusion (Takezawa et al 2011), cleavage, compaction and in the formation of a implantation competent embryo (Bloor et al 2002). …”

CD81 and CD9 work independently as extracellular components upon fusion of sperm and oocyte

“…The oocytes were isolated from oviducts of superovulated mice, and cumulus cells were removed from the oocytes by treatment with hyaluronidase (300 µg/ml) in TYH medium, as described previously (Takezawa et al, 2011). After zona-intact oocytes were treated with collagenase (Wako Pure Chemical Industries, Ltd.) at the final concentration of 1 mg/ml in a 30 µl drop of medium (Yamatoya et al, 2011) for 20 min at 37°C, denuded oocytes were removed from the drop with a microcapillary attached to a mouth piece and the remaining solution (<30 µl) was collected as extracellular components of oocytes.…”

Effects of DEHP on endometrial receptivity and embryo implantation in pregnant mice

“…Levels of molecules related to endometrial receptivity, such as E-cadherin, HoxA10 and others, are altered depending on their functions at different steps of this process. For example, the expression of E-cadherin, which is positively correlated with ␤-catenin expression [26], peaks during pre-implantation, functioning as an adhesion molecule to mediate homotypic adhesion between epithelial cells of the closed lumen in the mouse uterus [16,18]. It then declines sharply after preimplantation to favor the invasion of trophoblastic cells [18].…”