(a) β-catenin disassembly induced by membrane adhesion in oocytes and sperm. In the ‘Non-adhered' group (upper panels), ZP-denuded C57BL/6N oocytes were stained with DAPI and subsequently reacted with anti-β-catenin mAb. Also, epididymal sperm were stained with DAPI and anti-β-catenin mAb. In the ‘Adhered' group (lower panels), ZP-denuded C57BL/6N oocytes were stained with DAPI and then subjected to IVF for 30 min prior to incubation with anti-β-catenin mAb. Arrows indicate areas where fluorescent intensities of β-catenin are reduced. In each panel, boxes in middle sets of panels were enlarged and shown on the right. Scale bars: 20 and 10 µm in left and middle panels, respectively. (b) Fluorescence intensities of oocytes before and after sperm-oocyte adhesion. Fluorescence intensities were measured after being traced along dotted lines in the left panels of (a). Arrows indicate both sides of the oocyte cell membranes. (c) Fluorescence intensities of sperm before and after sperm-oocyte adhesion. Fluorescence intensities were measured after being traced along dotted lines in the right panels of a. Red and blue lines indicate fluorescent intensities for β-catenin and DAPI, respectively. (d) β-Catenin disassembly induced by membrane adhesion in oocytes and sperm. In the ‘Non-adhered' group (upper panels), ZP-denuded CD9-/- oocytes were stained with DAPI and subsequently reacted with anti-β-catenin mAb. In the ‘Adhered' group (lower panels), ZP-denuded CD9-/- oocytes were preloaded with DAPI as depicted in Fig. 3c and then subjected to IVF for 30 min prior to incubation with anti-β-catenin mAb. Arrows indicate areas where fluorescent intensities of β-catenin are reduced. In each panel, Scale bars: 20 µm. (e) Fluorescence intensities of CD9-/- oocytes before and after sperm-oocyte adhesion. Fluorescence intensities were measured after being traced along dotted lines in the left panels of d. Arrows indicate both sides of the oocyte cell membranes.