Reorganization of cytoskeletal proteins of mouse oocytes mediated by integrins

To study whether integrins on cell membrane ligate with intracellular cytoskeletal proteins and mediate their reorganization in egg activation, female mice were used for su- perovulation. The zona-free oocytes were incubated separately with specific ligand of integrins, an active RGD peptide, in vitro for certain period of time. RGE peptide and mouse capacitated sperm were used as controls. Freshly ovulated oocytes and those treated with different factors were immunostained with FITC-labeled anti-actin antibody, then detected with confocal micro- scope. The results demonstrated that freshly ovulated mouse oocytes, oocytes incubated for 2 h in vitro and those treated with control RGE peptide for 15 min showed hardly visible fluorescene or only thin fluorescence in plasma membrane region. Oocytes coincubated with sperms for 15 min and those treated with active RGD peptide for 10 min, 30 min and 2 hours respectively had strong and thick fluorescence in the plasma membrane and cortical region of oocytes, and some of them showed asymmetrically fluorescent distribution. It is proved that integrins on membrane are ligated directly with cytoskeletal protein. Integrins binding with their ligands regulate reor- ganization of cytoskelal protein, which may be involved in transmembrane signaling in egg acti- vation.