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The Role Of Metaphase II Arrest ( M II )

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Metaphase II arrest (M II)
The arresting of MII stage is characterized by a high level of MAP kinase and MPF activity (Nurse, 1990). MPF components are heterodimer of cdc2 and cyclin B, its function is stabilized by CSF: Mos, MAPK, and p90Rsk (Sagata, 1989; Haccard et al., 1993; Bhatt and Ferrell, 1999; Gross et al., 1999). An oocyte-specific protein kinase, c-mos, plays an important role in up-regulating the activity of MPF at various stages of final oocyte maturation. Several studies suggest that the proper function of the c-mos-MPF system is associated with important features of the last stages of oocyte maturation such as the resumption of meiotic maturation, inhibition of DNA replication between meiosis I and II, and the maintenance
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2011).
Myomegalin, cAMP-specific 3’,5’-cyclic phosphodiesterase 4D(PDE4D) is important for cell signaling pathway to regulate the diffusion of cAMP and its ability to go to the PKA isoenzymes anchored to organelles (Bolger et al., 2003; Fleming et al., 2004). In summary of proteins involved in MII arrest, the first group is proteins that function in stabilization of MPF and MAP by activation of CSF, mos to maintain oocyte arrest in metaphase II await fertilization and inhibit the activation of APC/C to initiate anaphase transition. Moreover, PDE4D and myomegalin also regulate the level of cAMP to maintain the activity of MPF during metaphase II-arrest. In the second group, PRDX and GST are involved in protection cell against oxidative stress and detoxification to protect oocyte during maturation.

Fertilization
During fertilization, Sperm penetrate into MII-arrest oocyte and trigger oocyte by increasing in intracellular calcium (Miyazaki et al., 1993). High level of intracellular calcium that is essential for cellular signaling lead to oocyte activation, meiosis resumption, cortical reaction to block polyspermy and then zygote development. Following egg activation and resumption of the cell cycle, sperm-egg fusion leads to sperm head decondensation and anaphase II plate formation, the second polar body extrusion and recruitment and translation of maternal mRNAs (Cascio and Wassarman,
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