Dynamic reorganization of actin filaments is essential for various stages of mammalian oocyte maturation, including spindle migration, actin cap formation, polar body extrusion, and cytokinesis. Various actin binding proteins (ABPs) have been known to be involved in the regulation of actin filament remodeling. We elucidate roles of three different actin binding proteins in mouse oocyte maturation. The heterodimeric actin-capping protein (CP) binds to the fast-growing(barbed) ends of actin filaments and plays essential roles in various actin-mediated cellular processes. When CP is knockdowned or inhibitory component was overexpressed, asymmetric division of oocyte have been compromised. It turns out that knockdown or inhibition of CP deplete cytoplasmic actin mesh level, which have been known to be essential for maintain cytoplasmic actin mesh. Another actin binding proteins, tropomodulin 3 (Tmod3), binds to the slow-growing end of actin filaments and knockdown or expression deletion mutant of Tmod3 also decrease actin mesh level in maturing oocyte and it severely ablated asymmetric division of oocyte. Finally, tropomyosin 3, actin filament binding proteins protect actin filament from depolymerization, is also important to maintain cortex integrity in maturing oocyte. Taken together, these finding showed the essential roles of actin binding proteins in remodeling of actin filaments in mammalian oocyte development.

• Suk Namgoong(Department of Animal Sciences, Chungbuk National University)