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DOC1R: a MAP kinase substrate that control microtubule organization of metaphase II mouse oocytes
M Emilie Terret1, Christophe Lefebvre, Alexandre Djiane
1UMR 7622, CNRS, Université Paris VI, 9 quai Saint Bernard, Bat. C, 75252 Paris, cedex 05, France.
Abstract:
For the success of fertilization, spindles of vertebrate oocytes must remain stable and correctly organized during the arrest in metaphase II of meiosis. 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. 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. We characterize DOC1R during mouse oocyte meiosis resumption. DOC1R is regulated by phosphorylation during meiotic maturation by MPF (M-phase promoting factor) and by the MOS/./MAPK pathway. DOC1R and a DOC1R-GFP fusion localize to microtubules during meiotic maturation. 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. These defects are rescued by overexpressing a Xenopus DOC1R, showing that they are specific to DOC1R. 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.
Insights
Researchers identified DOC1R, a protein regulated by MAPK, crucial for maintaining stable microtubule organization in mouse oocytes during meiosis II arrest, ensuring successful fertilization.
Area of Science:
- Cell Biology
- Molecular Biology
- Developmental Biology
Background:
- Vertebrate oocyte spindle stability is essential for successful fertilization.
- Proper organization of the metaphase II spindle is critical during meiotic arrest.
- Previous work identified MISS as a key regulator of oocyte spindle stability.
Purpose of the Study:
- To identify and characterize novel MAPK-interacting proteins involved in oocyte spindle regulation.
- To investigate the role of DOC1R in mouse oocyte meiotic maturation and spindle organization.
- To elucidate the molecular mechanisms by which DOC1R influences microtubule stability.
Main Methods:
- Yeast two-hybrid screening using MAPK as bait.
- Phosphorylation analysis during meiotic maturation.
- Subcellular localization studies using DOC1R-GFP fusion proteins.
- Functional analysis via antisense and double-stranded RNA injection.
- Rescue experiments using Xenopus DOC1R.
Main Results:
- DOC1R, a homolog of a potential tumor suppressor, was identified as a MAPK partner.
- DOC1R phosphorylation is regulated by MPF and the MOS/MAPK pathway during oocyte maturation.
- DOC1R localizes to microtubules and its depletion causes microtubule defects in metaphase II oocytes.
- Depletion-induced defects are specifically rescued by Xenopus DOC1R.
Conclusions:
- DOC1R is a novel MAPK substrate that plays a critical role in regulating microtubule organization and spindle stability in mouse oocytes.
- The MOS/MAPK pathway is important for controlling spindle stability during the metaphase II arrest.
- DOC1R represents a new target for understanding fertilization success and potential developmental abnormalities.