Requirements of Src family kinase during meiotic maturation in mouse oocyte

The Src family kinase (SFK) is important in normal cell cycle control. However, its role in meiotic maturation in mammalian has not been examined. We used confocal microscope immunofluorescence to examine the in vitro dynamics of the subcellular distribution of SFK during the mouse oocyte meiotic maturation and further evaluated the functions of SFK via biochemical analysis using a specific SFK pharmacological inhibitor, PP(2). Our results showed that nonphospho-SFK was absent in oocyte upon its release from follicle. Nonphospho-SFK appeared in cytoplasm 0.5 hr after the release of oocyte and translocated to germinal vesicle (GV) before germinal vesicle breakdown (GVBD). After GVBD, nonphospho-SFK colocated with condensed chromosomes. In occyte at metaphase I (MI) and telophase I, nonphospho-SFK accumulated in the cortex and the cleavage furrow respectively besides its existence in cytoplasm in both stages. In oocyte at metaphase II (MII), nonphospho-SFK concentrated at the aligned chromosomes. In contrast, phospho-SFK was absent in oocyte until 1 hr after its release from the follicle. Phospho-SFK accumulated in the GV, the cortex, and cytoplasm immediately prior to GVBD. After GVBD, phospho-SFK evenly distributed in oocyte. In oocyte at MII, phospho-SFK localized throughout the cytoplasm and under the egg member. When the SFK activity was inhibited, the oocyte failed to initiate GVBD, could not go into MII, and could not extrude the first polar body. Our results demonstrated that SFK is required for meiotic maturation in mouse oocyte.