2010
DOI: 10.1242/dev.052480
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Mouse Emi2 as a distinctive regulatory hub in second meiotic metaphase

Abstract: SUMMARYThe oocytes of vertebrates are typically arrested at metaphase II (mII) by the cytostatic factor Emi2 until fertilization. Regulatory mechanisms in Xenopus Emi2 (xEmi2) are understood in detail but contrastingly little is known about the corresponding mechanisms in mammals. Here, we analyze Emi2 and its regulatory neighbours at the molecular level in intact mouse oocytes. Emi2, but not xEmi2, exhibited nuclear targeting. Unlike xEmi2, separable N-and C-terminal domains of mouse Emi2 modulated metaphase … Show more

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Cited by 72 publications
(97 citation statements)
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“…In Xenopus eggs, calcineurin activity is essential in the process of exit from metII arrest, but this function is not conserved in mouse eggs (11)(12)(13). Mammalian eggs may deviate or differ from Xenopus, so it is not always possible to extrapolate across species with accuracy, and indeed this lack of conservation is observed in more than one aspect of cell cycle control (13)(14)(15). Instead, the exit of the mouse egg from metII arrest may more closely match mitotic exit in somatic cells and so rely on phosphatase activity from a member of the protein phosphatase 2A (PP2A) family (16 -20).…”
Section: B1mentioning
confidence: 99%
“…In Xenopus eggs, calcineurin activity is essential in the process of exit from metII arrest, but this function is not conserved in mouse eggs (11)(12)(13). Mammalian eggs may deviate or differ from Xenopus, so it is not always possible to extrapolate across species with accuracy, and indeed this lack of conservation is observed in more than one aspect of cell cycle control (13)(14)(15). Instead, the exit of the mouse egg from metII arrest may more closely match mitotic exit in somatic cells and so rely on phosphatase activity from a member of the protein phosphatase 2A (PP2A) family (16 -20).…”
Section: B1mentioning
confidence: 99%
“…EMI2 inhibits the anaphasepromoting complex (APC) to block cyclin B1 ubiquitination and degradation during MII and is thus an essential component of the cytostatic factor activity in the mature oocyte (Masui & Markert 1971, Shoji et al 2006. EMI2 contains a zinc-binding region that is essential for blocking APC activity during MII arrest (Shoji et al 2006, Suzuki et al 2010a, 2010b. Exit from MII during oocyte activation requires a lowering of cellular zinc through the rapid export of zinc from the oocyte.…”
Section: Introductionmentioning
confidence: 99%
“…It is tempting to speculate that, during the course of vertebrate evolution, the Erp1/CaMKII system evolved and became more dominant. In accordance with this hypothesis, Xenopus provides an example of an intermediate between more basal chordates (such as the ascidian) and the mammals: its eggs rely on both calcineurin and CaMKII (Mochida and Hunt, 2007;Nishiyama et al, 2007) for cell cycle resumption, whereas mammalian eggs have completely dispensed with calcineurin (Suzuki et al, 2010) and rely solely on CaMKII to trigger not only Erp1 destruction and consequent APC/C-mediated cyclin B destruction (Madgwick et al, 2005;Shoji et al, 2006), but also activation of the kinase Wee1B which also inactivates CDK1 by inhibitory phosphorylation (Oh et al, 2011). It will be interesting to test the role of CN during fertilisation in eggs of other more basal invertebrates that are known to be activated by Ca 2+ to explore these findings.…”
Section: Calcineurin As the Ancestral Mediator Of Egg Activationmentioning
confidence: 87%
“…At the same time as Erp1 is being degraded, the Ca 2+ -sensitive phosphatase CN promotes metaphase exit by activating Cdc20-mediated APC/C activity (Mochida and Hunt, 2007;Nishiyama et al, 2007). Interestingly though, CN appears to play no part in mouse egg activation (Suzuki et al, 2010), in which instead CaMKII [specifically the γ isoform (Chang et al, 2009;Backs et al, 2010)] is the sole signal transducer of the fertilisation-induced Ca 2+ rise (Shoji et al, 2006;Madgwick et al, 2006); this occurs not only via APC/C-mediated cyclin B destruction (Irniger et al, 1995;King et al, 1995;Sudakin et al, 1995), but also via activation of Wee1B (Oh et al, 2011), which together result in the inactivation of Cdk1 (MPF) and meiotic exit. However, in no invertebrate species arrested at metaphase I is it known how sperm-triggered Ca 2+ increase mediates the release of cell cycle arrest.…”
Section: Introductionmentioning
confidence: 99%
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