Profilin 1 plays feedback role in actin-mediated polar body extrusion in mouse oocytes

Mammalian oocytes undergo several crucial processes during meiosis maturation, including spindle formation and migration and polar body extrusion, which rely on the regulation of actin. As a small actin-binding protein, profilin 1 plays a central role in the regulation of actin assembly. However, the functions of profilin 1 in mammalian oocytes are uncertain. To investigate the function of profilin 1 in oocytes, immunofluorescent staining was first used to examine profilin 1 localisation. The results showed that profilin 1 was localised around the meiotic spindles and was colocalised with cytoplasmic actin. Knockdown (KD) of profilin 1 with specific morpholino microinjection resulted in failure of polar body extrusion. This failure resulted from an increase of actin polymerisation both at membranes and in the cytoplasm. Furthermore, western blot analysis revealed that the expression of Rho-associated kinase (ROCK) and phosphorylation levels of myosin light chain (MLC) were significantly altered after KD of profilin 1. Thus, the results indicate that a feedback mechanism between profilin, actin and ROCK-MLC2 regulates actin assembly during mouse oocyte maturation.