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Resources » Paper

Michael Stitzel et al. (2007) International Worm Meeting "The meiotic cell cycle regulates the EGG-3/MBK-2 cortical complex essential for the oocyte-to-zygote transition."

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  • Comments on Michael Stitzel et al. (2007) International Worm Meeting "The meiotic cell cycle regulates the EGG-3/MBK-2 cortical complex essential for the oocyte-to-zygote transition." (0)

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    Publication type:
    Meeting_abstract
    WormBase ID:
    WBPaper00030380

    Michael Stitzel, & Geraldine Seydoux (2007). The meiotic cell cycle regulates the EGG-3/MBK-2 cortical complex essential for the oocyte-to-zygote transition presented in International Worm Meeting. Unpublished information; cite only with author permission.

    The oocyte-to-zygote transition transforms a differentiated germ cell into a totipotent zygote. The signals that activate this transition remain poorly understood. Here we report that regulation by the meiotic cell cycle of the MBK-2 kinase and its cortical anchor EGG-3 is one of the signals that initiates the oocyte-to-zygote transition in C. elegans. The DYRK kinase MBK-2 marks oocyte proteins for degradation shortly after fertilization during the second meiotic division (Nishi & Lin, 2005; Stitzel et al., 2006). GFP:MBK-2 accumulates on the cortex of oocytes and relocalizes to the cytoplasm during the second meiotic division. Cortical localization of MBK-2 depends on EGG-3, a cortical oocyte protein also essential for the oocyte-to-zygote transition (Maruyama and Singson, pers. comm). MBK-2 and EGG-3 interact directly in vitro, suggesting that EGG-3 may function as a transient cortical anchor for MBK-2 (see abstract by Cheng & Seydoux). Using cell cycle and egg-3 mutants, we found that MBK-2 is regulated both positively by regulators of meiotic M phase and negatively by EGG-3. Activators of meiotic M phase activate MBK-2 kinase activity upon oocyte maturation. EGG-3 then sequesters active MBK-2 at the cortex until the second meiotic division. This system ensures that oocyte proteins become marked for degradation only at the end of the meiotic divisions, when they are no longer needed and the egg is ready to embark on embryonic development. Remarkably, the meiotic cell cycle appears to be driving these changes independently of fertilization. We propose that, in addition to regulating chromosome segregation, the meiotic cell cycle controls egg-wide developmental changes essential for the initiation of embryonic development.


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