Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Critical Care giúp cho các bạn có thêm kiến thức về ngành y học đề tài: Mechanism of the chromosome-induced polar body extrusion in mouse eggs. | 0 CELL DIVISION Wang et al. Cell Division 2011 6 17 http content 6 1 17 RESEARCH Open Access Mechanism of the chromosome-induced polar body extrusion in mouse eggs Qiong Wang1 2 Catherine Racowsky1 and Manqi Deng1 Abstract Background An oocyte undergoes two rounds of asymmetric division to generate a haploid gamete and two small polar bodies designed for apoptosis. Chromosomes play important roles in specifying the asymmetric meiotic divisions in the oocytes but the underlying mechanism is poorly understood. Results Chromosomes independently induce spindle formation and cortical actomyosin assembly into special cap and ring structures in the cortex of the oocyte. The spindle and the cortical cap ring interact to generate mechanical forces leading to polar body extrusion. Two distinct force-driven membrane changes were observed during 2nd polar body extrusion a protrusion of the cortical cap and a membrane invagination induced by an anaphase spindle midzone. The cortical cap protrusion and invagination help rotate the spindle perpendicularly so that the spindle midzone can induce bilateral furrows at the shoulder of the protruding cap leading to an abscission of the polar body. It is interesting to note that while the mitotic spindle midzone induces bilateral furrowing leading to efficient symmetric division in the zygote the meiotic spindle midzone induced cytokinetic furrowing only locally. Conclusions Distinct forces driving cortical cap protrusion and membrane invagination are involved in spindle rotation and polar body extrusion during meiosis II in mouse oocytes. Background Female meiosis in most animals is characterized by two sequential asymmetric meiotic divisions following one round of DNA replication which results in formation of a haploid egg and extrusion of two small polar bodies destined for degeneration. Oocyte haploidization by means of discarding half of the chromosomes into the polar bodies represents a special mechanism for .
