TY - JOUR
T1 - Regulation of the G2/M transition in oocytes of Xenopus tropicalis
AU - Stanford, Jennifer S.
AU - Lieberman, Soyan Leung
AU - Wong, Valerie L.
AU - Ruderman, Joan V.
N1 - Funding Information:
We thank Hazel Sive and Vladimir Apekin (Whitehead Institute, MIT) for several shipments of X. tropicalis, and Brian Frederick for help in maintaining our X. tropicalis and X. laevis colonies; Laurinda Jaffe (University of Connecticut Health Center) for collagenase defolliculation protocols; Jonathan Cooper (University of Washington) for the pCS3+CK2β construct; Angus MacNicol (University of Arkansas for Medical Sciences) for the pXen-Mos construct; Richard Maurer (Oregon Health and Science University) for the GST-PKI construct; and Susan Taylor (University of California, San Diego) for the mouse PKA-catalytic subunit clone. We thank Jean-Francois Bodart (Van Andel Research Institute), and Jonathan Marchant (University of California at Irvine) for discussions about X. tropicalis . We are grateful to Brian Duckworth of this laboratory for making the PKAc construct, and to all of the members of the Ruderman lab for helpful, enthusiastic discussions, and several hot dog happy hours. J.S.S. is an NSF predoctoral fellow. This work was supported by N.I.H. Grant HD 37636 (to J.V.R.).
PY - 2003/8/15
Y1 - 2003/8/15
N2 - The molecular events regulating hormone-induced oocyte activation and meiotic maturation are probably best understood in Xenopus laevis. In X. laevis, progesterone activates the G2-arrested oocyte, induces entry into M phase of meiosis I (MI) and resumption of the meiotic cell cycles, and leads to the formation of a mature, fertilizable egg. Oocytes of Xenopus tropicalis offer several practical advantages over those of X. laevis, including faster and more synchronous meiotic cell cycle progression, less seasonal variability, and the availability of transgenic approaches. Previous work found several similarities in the pathways regulating oocyte maturation in the two species. Here, we report several additional ones that are conserved in X. tropicalis. (1) Injection of Mos mRNA into G2-arrested oocytes activates the MAP kinase cascade and induces the G2/MI transition. (2) Injection of the β subunit of the kinase CK2 (a negative regulator of Mos and oocyte activation) delays the G2/MI transition. (3) Elevating PKA activity blocks progesterone-induced maturation; repressing PKA activity induces entry into MI in the absence of progesterone. (4) LF (anthrax lethal factor), which cleaves certain MAP kinase kinases, strongly reduces both the rate and extent of entry into MI. In contrast to the one previously reported major difference between oocytes of the two species, we find that injection of egg cytoplasm ("MPF activity") into G2-arrested X. tropicalis oocytes induces entry into meiosis I even when protein synthesis is blocked, just as it does in oocytes of X. laevis. These results indicate that much of what we have learned from studies of X. laevis oocytes holds for those of X. tropicalis, and suggest that X. tropicalis oocytes offer a good experimental system for investigating certain questions that require a rapid, synchronous progression through the G2/meiosis I transition.
AB - The molecular events regulating hormone-induced oocyte activation and meiotic maturation are probably best understood in Xenopus laevis. In X. laevis, progesterone activates the G2-arrested oocyte, induces entry into M phase of meiosis I (MI) and resumption of the meiotic cell cycles, and leads to the formation of a mature, fertilizable egg. Oocytes of Xenopus tropicalis offer several practical advantages over those of X. laevis, including faster and more synchronous meiotic cell cycle progression, less seasonal variability, and the availability of transgenic approaches. Previous work found several similarities in the pathways regulating oocyte maturation in the two species. Here, we report several additional ones that are conserved in X. tropicalis. (1) Injection of Mos mRNA into G2-arrested oocytes activates the MAP kinase cascade and induces the G2/MI transition. (2) Injection of the β subunit of the kinase CK2 (a negative regulator of Mos and oocyte activation) delays the G2/MI transition. (3) Elevating PKA activity blocks progesterone-induced maturation; repressing PKA activity induces entry into MI in the absence of progesterone. (4) LF (anthrax lethal factor), which cleaves certain MAP kinase kinases, strongly reduces both the rate and extent of entry into MI. In contrast to the one previously reported major difference between oocytes of the two species, we find that injection of egg cytoplasm ("MPF activity") into G2-arrested X. tropicalis oocytes induces entry into meiosis I even when protein synthesis is blocked, just as it does in oocytes of X. laevis. These results indicate that much of what we have learned from studies of X. laevis oocytes holds for those of X. tropicalis, and suggest that X. tropicalis oocytes offer a good experimental system for investigating certain questions that require a rapid, synchronous progression through the G2/meiosis I transition.
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U2 - 10.1016/S0012-1606(03)00259-8
DO - 10.1016/S0012-1606(03)00259-8
M3 - Article
C2 - 12921744
AN - SCOPUS:0042562239
SN - 0012-1606
VL - 260
SP - 438
EP - 448
JO - Developmental biology
JF - Developmental biology
IS - 2
ER -