Small GTPase RhoA regulates cytoskeleton dynamics during porcine oocyte maturation and early embryo development

Abstract

Mammalian oocyte maturation is distinguished by asymmetric division that is regulated primarily by cytoskeleton, including microtubules and microfilaments. Small Rho GTPase RhoA is a key regulator of cytoskeletal organization which regulates cell polarity, migration, and division. In this study, we investigated the roles of RhoA in mammalian oocyte meiosis and early embryo cleavage.(1) Disrupting RhoA activity or knock down the expression of RhoA caused the failure of polar body emission. This may have been due to decreased actin assembly and subsequent spindle migration defects. The involvement of RhoA in this process may have been though its regulation of actin nucleators ROCK, p-Cofilin, and ARP2 expression. (2) In addition, spindle morphology was also disrupted and p-MAPK expression decreased in RhoA inhibited or RhoA KD oocytes, which indicated that RhoA also regulated MAPK phosphorylation for spindle formation. (3) Porcine embryo development was also suppressed by inhibiting RhoA activity. Two nuclei were observed in one blastomere, and actin expression was reduced, which indicated that RhoA regulated actin-based cytokinesis of porcine embryo. Thus, our results demonstrated indispensable roles for RhoA in regulating porcine oocyte meiosis and cleavage during early embryo development.

RhoA-mediated FMNL1 regulates GM130 for actin assembly and phosphorylates MAPK for spindle formation in mouse oocyte meiosis

“…34,[38][39][40] Recent study showed Rho GTPase RhoA RNAi reduced the expression of p-MAPK and resulted in aberrant spindle formation during mouse oocyte meiotic maturation. 41 While our result showed FMNL1 depletion resulted in the disrupted localization and the decreased expression of p-MAPK, as Formin proteins are the effectors of Rho GTPases, our results indicated that similar with Rho GTPase RhoA, FMNL1 might regulate spindle formation during oocyte meiosis through its effects on p-MAPK expression. Moreover, our results also showed that FMNL1 was the downstream molecule of RhoA, we speculated a RhoA-FMNL1-MAPK signal pathway which involved into spindle formation during oocyte meiotic maturation.…”

GTPase-activating protein Elmod2 is essential for meiotic progression in mouse oocytes

“…11,12 During porcine oocyte maturation and early embryo development, small GTPase RhoA regulates cytoskeleton dynamics. 13 Although GTPases can hydrolyze GTP on their own, their efficiency is greatly elevated by GTPase-activating proteins (GAPs); while guanine exchange factors (GEFs) help convert GDP into GTP to regenerate GTPases. All members of the GTPase family have their specific GEFs and GAPs.…”

Centriolin, a centriole-appendage protein, regulates peripheral spindle migration and asymmetric division in mouse meiotic oocytes

“…17 The roles of microfilaments and/or microtubules in spindle migration and anchorage to the oocyte cortex have been reported for various invertebrate and mammalian oocytes, 2 and several factors have recently been shown to regulate oocyte polarity and asymmetric division. [18][19][20][21] However, the role of centrosomes in this process is still not well understood. We showed that depletion of centriolin caused a failure of peripheral meiotic spindle migration and polarity establishment in a high proportion of oocytes, as well as elongated central spindles, leading to symmetric divisions, as indicated by the production of 2 same-sized cells or the formation of a large polar body.…”