RAB14 GTPase is essential for actin-based asymmetric division during mouse oocyte maturation

RAB14 is a member of small GTPase RAB family which localizes at the endoplasmic reticulum (ER), Golgi apparatus and endosomal compartments. RAB14 acts as molecular switches that shift between a GDP-bound inactive state and a GTP-bound active state and regulates circulation of vesicles between the Golgi and endosomal compartments. In present study, we investigated the roles of RAB14 during oocyte meiotic maturation.

Microinjection with siRNA and exogenous mRNA for knock down and rescue, and immunofluorescence staining, Western blot and real-time RT-PCR were utilized for the study.

Our results showed that RAB14 localized in the cytoplasm and accumulated at the cortex during mouse oocyte maturation, and it was also enriched at the spindle periphery. Depletion of RAB14 did not affect polar body extrusion but caused large polar bodies, indicating the failure of asymmetric division. We found that absence of RAB14 did not affect spindle organization but caused the spindle migration defects, and this might be due to the regulation on cytoplasmic actin assembly via the ROCK-cofilin signalling pathway. We also found that RAB14 depletion led to aberrant Golgi apparatus distribution. Exogenous Myc-Rab14 mRNA supplement could significantly rescue these defects caused by Rab14 siRNA injection.

Taken together, our results suggest that RAB14 affects ROCK-cofilin pathway for actin-based spindle migration and Golgi apparatus distribution during mouse oocyte meiotic maturation.