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Biology of the oocyte.
The last step of oogenesis also called meiotic maturation is a key event for embryonic development and ensures the formation of a haploid germ cell ready to be fertilized. In the ovary, oocytes are arrested in prophase of the first meiotic division. At time of ovulation, oocytes reenter meiosis upon hormonal stimulation and reach the second meiotic division without an intervening S phase. Oocytes then become arrested a second time in Metaphase II awaiting for fertilization. This process relies on the activation of MPF (Cdk1-CyclinB complexes) and recapitulates all the biochemical mechanisms regulating the G2-M transition of the cell cycle.
Our team is interested on studying three steps of meiotic maturation using Xenopus oocyte:
- What regulate the activation of MPF in response to steroid hormones? Our researches are mainly focused on the respective contribution of kinases (Cdk1 and MAPK) and phosphatases (PP1 and PP2A)
- What is the molecular mechanism inhibiting DNA replication during the meiosis I-meiosis II transition; this inhibition being essential for the formation of a haploid gamete?
- Which mechanisms arrest the oocyte in metaphase II?
Understanding the cell cycle regulation in meiosis is not only critical for reproduction and early development, it also helps us to decipher the process of tumoregenesis as cancer often results from the misregulation of cell division.