Abstract：M-phase promoting factor (MPF) is an important protease in regulating cell cycle progression, explore the expression of MPF in different stages of spermatogenesis in mice will provide insight into the molecular mechanisms of spermatogenesis. The object of this experiment was to expounded the chang of MPF activity in different ages of the mice(Mus musculus) and the relationship between MPF activity and sperm production, which by measuring MPF activity of testicular cells in different ages(8, 14, 18, 20, 28 and 56 d), using flow cytometry to analysis the DNA ploidy of germ cell and analysing the expressing of two subunits of MPF-CDK1 and Cyclin B1 by immunohistochemistry. The results showed that there was no tetraploid cells in the testis of mice before 18-day old, and then suddenly increased to the peak, and then gradually decreased with the age increased. Haploid germ cells appeared from 18-day old and the ratio of this type of cell enlarged rapidly at 20-day old, followed by a further increasing with the age increasesd. The trend of the MPF activity in different ages was similar to tetraploid cells, that was, the MPF activity reached the highest level at 18 d and then decreased, but it incresed once again at 56 d. From the results of immunohistochemistry, CDK1 and Cyclin B1 which was the subunits of MPF expressed in all testis of different ages, its expression increased with age and reached the maximum at 18 d and 20 d, followed by gradually decreased. These results indicate that, tetraploid cells begin to appeare in the testis of mice of 18-day old which indicating that the starting of spermatogenesis and the germ cells would go into primary spermatocytes stage of the first meiosis,while the MPF activity and the expression of its subunits-CDK1 and Cyclin B1 in the testicular tissue are highest at 18 d, suggesting that MPF may play an important role in regulating the meiosis process of mouse spermatogenic cells.
