![]() ![]() Not much is known about the precise mechanisms that allow the second meiotic spindle to remain correctly organized during the so-called CSF (cytostatic factor) ( Masui and Markert, 1971) arrest in metaphase II of vertebrate oocytes. During the arrest in metaphase II, chromosomes remain aligned on the metaphase plate, waiting for fertilization to trigger chromosome segregation. These meiotic spindles organize from MTOCs (microtubule organizing centers)that lack centrioles. Typically, mouse meiotic spindles are barrel shaped and are devoid of astral microtubules. Thus, the discovery of DOC1R, a substrate of MAPK that regulates microtubule organization of metaphase II mouse oocytes, reinforces the importance of this pathway in the control of spindle stability during the metaphase II arrest.Īfter ovulation, mouse oocytes arrest for several hours in metaphase II(MII) of the second meiotic division with a stable spindle. These defects are rescued by overexpressing a Xenopus DOC1R, showing that they are specific to DOC1R. ![]() Consistent with this microtubular localization, we show, by antisense and double-stranded RNA injection, that depletion of DOC1R induces microtubule defects in metaphase II oocytes. DOC1R and a DOC1R-GFP fusion localize to microtubules during meiotic maturation. DOC1R is regulated by phosphorylation during meiotic maturation by MPF (M-phase promoting factor)and by the MOS/./MAPK pathway. We characterize DOC1R during mouse oocyte meiosis resumption. Using the same screen, we identify another MAPK partner, DOC1R (Deleted in oral cancer one related), a murine homologue of a potential human tumor suppressor gene. Using a two-hybrid screen with MAPK as a bait, we have recently identified MISS (MAPK interacting and spindle stabilizing) which controls mouse oocyte metaphase II spindle stability. For the success of fertilization, spindles of vertebrate oocytes must remain stable and correctly organized during the arrest in metaphase II of meiosis. ![]()
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May 2023
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