Small GTPase RhoA is required for ooplasmic segregation and spindle rotation, but not for spindle organization and chromosome separation during mouse oocyte maturation, fertilization, and early cleavage.
RhoA, a small GTPase, plays versatile roles in many aspects of cell function such as stress fiber formation, cytokinesis, and cell polarization. In this study, we investigated the subcellular localization of RhoA and its possible roles during oocyte maturation and fertilization. RhoA was localized in the cytoplasm of eggs from the germinal vesicle (GV) stage to 2-cell stage, especially concentrating in the midbody of telophase spindle when oocyte extruded PB1 and PB2. The RhoA kinases (ROCKs) specific inhibitor Y-27632 blocked GV breakdown (GVBD) and first polar body extrusion, but did not affect apparatus formation and anaphase/telophase I entry. Anti-RhoA antibody microinjection into the oocytes showed similar results. RhoA inhibitor caused abnormal organization of microfilaments, failure of spindle rotation, PB2 extrusion as well as cleavage furrow formation, while sister chromatid separation was not affected. Microinjection of RhoA antibody also blocked PB2 emission. Our findings indicate that RhoA, by regulating microfilament organization, regulates several important events including GVBD, polar body emission, spindle rotation, and cleavage.
Zhong
Zhi-Sheng
ZS
State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
Huo
Li-Jun
LJ
Liang
Cheng-Guang
CG
Chen
Da-Yuan
DY
Sun
Qing-Yuan
QY
D000577:Amides / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D002970:Cleavage Stage, Ovum / Q000166:cytology / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005306:Fertilization / Q000187:drug effects / Q000502:physiology*; D005307:Fertilization in Vitro; D008297:Male; D051379:Mice; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D009866:Oogenesis / Q000187:drug effects / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D008941:Spindle Apparatus / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000577:Amides; D004791:Enzyme Inhibitors; D011725:Pyridines; C108830:Y 27632; D020742:rhoA GTP-Binding Protein