Figure 6. Roles of Tpm3 in oocyte maturation. (A) The localization of Tpm3 dynamically changes during oocyte maturation. At the germinal vesicle (GV) and germinal vesicle breakdown (GVBD) stages, Tpm3 colocalizes with cortical actin, whereas at the MI and MII stages, Tpm3 is excluded from the cortex. The localization of Tpm3 at the cortex correlates with recently reported changes in cortical tension.³⁵ (B) Protection of cortical actin from ADF/cofilin-induced depolymerization by Tpm3. Cytoplasmic actin in the oocyte is dynamically remodeled by polymerization induced by actin nucleators and depolymerization induced by ADF/cofilin to provide the force for cytoplasmic streaming required for spindle migration. By contrast, cortical actin is relatively stable during oocyte maturation to maintain cortical integrity. Tpm3-coated cortical actin filaments in oocytes can be protected from depolymerization induced by ADF/cofilin, as has been reported in other cells¹⁴