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Second meiotic arrest and exit in

frogs and mice

Perry, A.C.F. and Verlhac, M.H.

EMBO Rep. 9, 246-251 (2008)


Mature vertebrate oocytes typically undergo programmed arrest at the second meiotic cell cycle until they are signalled to initiate embryonic development at fertilization. Here, we describe the underlying molecular mechanisms of this second meiotic arrest and release in Xenopus, and compare and contrast them with their counterparts in mice.

Low-resolution model of second metaphase homeostasis. The model links spindle modulation by Mos to the establishment and maintenance of, and exit from, Emi2-mediated mII arrest. The establishment of Emi2 as cytostatic factor (Emi2CSF) is coordinated by mII spindle formation (spindle*) and Mos activity. Following fertilization, Emi2CSF is replaced by Emi2cyk activity which modulates Mos function (Mos*) to ensure that the spindle is formatted for productive cytokinesis (spindle+).

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