Involvement of Dynamin 2 in actin-based polar-body extrusion during porcine oocyte maturation.

Mammalian oocyte meiotic maturation involves a unique asymmetric division, but the regulatory mechanisms and signaling pathways involved are poorly understood. Dynamins are ubiquitous eukaryotic GTPases involved in membrane trafficking and actin dynamics, whose roles in mammalian oocyte maturation have not been determined. In this study, we used porcine oocytes to show that Dynamin 2 accumulated at the meiotic spindle and in the cortex of oocytes, with a distribution similar to that of actin. Inhibiting Dynamin 2 activity in porcine oocytes with the specific inhibitor dynasore resulted in failed polar-body extrusion. This phenotype may have been due to aberrant actin distribution and/or spindle positioning as inhibitor treatment disrupted the formation of the actin cap and cortical granule-free domain, which negatively impacted spindle positioning. Moreover, the distribution of ARP2, a key actin-nucleation factor, was severely reduced in the cortex after dynasore treatment. Thus, our results suggest that Dynamin 2 possibly regulates porcine oocyte maturation through its effects on actin-mediated spindle positioning and cytokinesis, and that this may depend on regulating ARP2 localization.