Inhibition of MEK or cdc2 Kinase Parthenogenetically Activates Mouse Eggs and Yields the Same Phenotypes as Mos−/− Parthenogenotes

Abstract

Mammalian eggs are arrested in metaphase II of meiosis until fertilization. Arrest is maintained by cytostatic factor (CSF) activity, which is dependent on the MOS-MEK-MAPK pathway. Inhibition of MEK1/2 with a specific inhibitor, U0126, parthenogenetically activated mouse eggs, producing phenotypes similar to Mos(-/-) parthenogenotes (premature, unequal cleavages and large polar bodies). U0126 inactivated MAPK in eggs within 1 h, in contrast to the 5 h required after fertilization, while the time course of MPF inactivation was similar in U0126-activated and fertilized eggs. We also found that inactivation of MPF by the cdc2 kinase inhibitor roscovitine induced parthenogenetic activation. Inactivation of MPF by roscovitine resulted in the subsequent inactivation of MAPK with a time course similar to that following fertilization. Notably, roscovitine also produced some Mos(-/-)-like phenotypes, indistinguishable from U0126 parthenogenotes. Simultaneous inhibition of both MPF and MAPK in eggs treated with roscovitine and U0126 produced a very high proportion of eggs with the more severe phenotype. These findings confirm that MEK is a required component of CSF in mammalian eggs and imply that the sequential inactivation of MPF followed by MAPK inactivation is required for normal spindle function and polar body emission.

GM130, a cis-Golgi protein, regulates meiotic spindle assembly and asymmetric division in mouse oocyte

“…7A). Treatment of U0126, the specific MEK inhibitor, 24,25 caused disorganized spindles and GM130 dispersion into the cytoplasm in mouse oocytes.…”

Single Ca2+ transients vs oscillatory Ca2+ signaling for assisted oocyte activation: limitations and benefits

“…In addition, full-term embryonic development was achieved in mice and pigs by using TPEN as the only agent for oocyte activation. Moreover, different protein synthesis inhibitors such as puromycin (De Sutter et al 1992, Lu et al 2006) and cycloheximide (Moses & Kline 1995, Rogers et al 2006 have been shown to alleviate meiotic arrest by interrupting the continuous synthesis of cyclin B. Roscovitine, in turn, was shown to induce the meiotic release by direct inhibition of the cdk1 function (Phillips et al 2002).…”

Temporal regulation of the first mitosis in Xenopus and mouse embryos

“…CSF activity results from the activation of various pathways in which the APC/C inhibitor Emi2 plays a key role (Shoji et al, 2006;Tung et al, 2005). The Mos/MEK1/ERK1 and ERK2 MAP kinases cascade is also involved, but its exact mode of participation in the CSF activity remains not fully understood (Araki et al, 1996;Colledge et al, 1994;Hashimoto et al, 1994;Phillips et al, 2002;Sagata et al, 1989;Verlhac et al, 1996). Recent papers by T. A c c e p t e d M a n u s c r i p t downstream substrate of ERK2, in Xenopus oocytes is a key regulatory event in stimulating Emi2 activity (Inoue et al, 2007;Nishiyama et al 2007).…”