Page 34 - ESHRE2019

Oocyte contribution to activation
 Ca2+ stores in SER
 Ca2+ membrane pumps and channels  PIP2, DAG, IP3R, PKC
 CaMKII: calcium/calmodulin‐dependent protein kinase II: o activated by Ca2+
o plays a key role in oocyte activation
o Initiates cascade that leads to alleviation of meiotic arrest
 MAPK: mitogen‐activated protein kinase  Other phospholipases, e.g. PLCβ, γ, δ.
Defects in above components can lead to fertilisation failure (reviewed by Yeste et al 2016 Hum Reprod Update)
Block to polyspermy
The egg must be fertilised by a single sperm to give rise to a viable embryo.
Around 10% of spontaneous abortions are due to diandric triploidy – also around 10% 3PN after IVF
(Hassold et al 1980, van der Ven et al 1985) Two blocks against polyspermy:
o Modification of the oolemma
o Exocytosis of cortical granules (modification of ZP)
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