The Functional Research Of Maternal Protein RBBP7 In Mouse Oocyte Development And Maturation

Retinoblastoma binding protein 7 (RBBP7) is a nuclear protein with tumor inhibitory effect, previous studies showed that RBBP7 protein can interfere with normal cell cycle and increase the apoptosis of tumor cells to inhibit the conversion. Our laboratory studied the protein expression of mouse MII (metaphase of the second meiosis) oocytes and parthenogenetically activated oocytes by 2D gel electrophoresis, through mass spectrum identification, bioinformatical analysis. RBBP7 decreased in the 2D gel of parthenogenetically activated oocytes. This indicates that RBBP7 may play an important function in the maturation of mouse oocytes. But there is no report on the functional reasearch of RBBP7 in the oocyte maturation and embryo development.We study the location of RBBP7 in mouse ovary with immunohistochemistry and immunofluorescence first. Immunohistochemistry of ovary sections indicate that RBBP7 distribute in the nucleus of oocytes. Immunofluorescence show that, RBBP7 locates in the nucleus of the germinal vesicle (GV) oocytes and when the germinal vesicle breakdown (GVBD), RBBP7 is in the cytoplasm. During MI (the metaphase of the first meiosis) RBBP7 is in the spindle. In AI(antaphase of the first meiosis), RBBP7 is in the midbody of the spindle. Specially RBBP7 has the same localtion with the spindle in the MII oocytes. To study the function of RBBP7 in mouse oocyte development and maturation, we microinject RBBP7 siRNA into the cytoplasm of mouse GVBD oocytes, continuous observation using time-lapse video miscroscopy finds that when RBBP7 is knock down,there is no difference in the number of oocytes which emission the first polar body, but many of the RBBP7 depleted oocytes has the increased cytokinesis of the first meiosis, the homologous chromosome can not segregate and at last, the cleavage furrow displays fusion with the oocyte, and finally the cells will be binucleate cells.With above phenotypes, we then studied the mechanism that how RBBP7 influence the segregation of homologous chromosome. Immunoprecipitation analysis with mouse ovaries finds that RBBP7 can function with VCP. VCP can regulate the disassembly of the spindle in the anaphase of mitosis. RBBP7 specially locate in the midbody of the spindle in the anaphase of meiosis I. So we suggest that RBBP7 may be a spindle assembly factor and RBBP7 can function with VCP to regulate the spindle disassembly in female meiosis I to regulate the homologous chromosme segregation.