Advance Publication by J-STAGE Journal of Reproduction and Development

23 The mammalian oocyte undergoes an asymmetric division during meiotic maturation, 24 producing a small polar body and a haploid gamete. This process involves the dynamics of 25 actin filaments, and the guanosine triphosphatase (GTPase) protein superfamily is a major 26 2 regulator of actin assembly. In the present study, the small GTPase CDC42 was shown to 1 participate in the meiotic maturation of porcine oocytes. Immunofluorescent staining showed 2 that CDC42 was mainly localized at the periphery of the oocytes, and accumulated with 3 microtubules. Deactivation of CDC42 protein activity with the effective inhibitor ML141 4 caused a decrease in actin distribution in the cortex, which resulted in a failure of polar body 5 extrusion. Moreover, western blot analysis revealed that besides the Cdc42-N-WASP pathway 6 previously reported in mouse oocytes, the expression of ROCK and p-cofilin, two molecules 7 involved in actin dynamics, was also decreased after CDC42 inhibition during porcine oocyte 8 maturation. Thus, our study demonstrates that CDC42 is an indispensable protein during 9 porcine oocyte meiosis, and CDC42 may interact with N-WASP, ROCK, and cofilin in the 10 assembly of actin filaments during porcine oocyte maturation. 11 12