RESUMEN
Objective To explore the effect and mechanism of the bone morphologenetic protein 4 (BMP4)/Smad signaling pathway on the apoptosis of mouse primordial follicle oocytes .Methods Three-day-old Kunming mouse ovarine tissues were digested by the two-step enzymatic method to extract and purify oocytes .The cultured oocytes were divided into three groups: the normal culture medium (Con group), the medium with BMP4 (BMP4 group), and the medium with BMP4 and BMP4 inhibitor ( BMP4+inhibitor group ) .TUNEL was used to examine the effects of BMP 4 on the survival of the primordial follicle oocyte;Immunohistochemical staining and Real-time quantitative PCR were performed to investigate the expressions of p-Smad1/5/8, sohlh2, c-kit and foxo3a;siRNA interference, sohlh2 plasmid transfection and LY294002 treatments were performed to explore the mechanism of the BMP 4/Smad signaling pathway on the apoptosis of oocytes . Results TUNEL results demonstrated that the ratio of apoptotic oocytes in BMP 4 group was significantly lower than that in the Con group ( P <0.05 ) and the BMP4 +inhibitor group ( P <0.05 ); BMP4 significantly promoted the nuclear translocation of Smad and inhibited the nuclear translocation of foxo 3a, the mRNA and protein levels of sohlh2 and c-kit remarkably increased in BMP4 group.The effect of BMP4 on the oocyte survival was significantly repressed after sohlh 2 siRNA transfection.Sohlh2 overexpression up-regulated the expression of p-foxo3a, and this activity was abolished by LY 294002.Conclusion BMP4/Smad signaling pathway may inhibit primordial follicle oocyte apoptosis , via up-regulation of the expression of sohlh2 and c-kit, and then down-regulation of the nuclear translocation of foxo 3a.
RESUMEN
Primordial follicles are formed prenatally in mammalian ovaries, and at birth they are fated to be activated to primary follicles, to be dormant, or to die. During the early stage of folliclulogenesis, the oocyte undergoes dynamic alterations in expression of numerous genes, which are regulated by transcription factors. Several germ-cell specific transcriptional regulators are critical for formation and maintenance of follicles. These transcriptional regulators include: Figla, Lhx8, Nobox, Sohlh1, and Sohlh2. A subset of these transcriptional regulators is mutated in women with ovarian insufficiency and infertility. Establishment of this oocyte pool is essential for fertility. This review focuses on these transcriptional regulators of female primordial follicles.