Fertilisation II Flashcards
(33 cards)
What does the acrosome reaction release from the acrosome?
Hydrolytic enzymes
Examples of hydrolytic enzymes that are released from the sperm during the AR?
hyaluronidase and proteases, eg acrosin
What assists passage through the ZP (as well as the enzymes)?
Sperm flagellar propulsion
What is known ab the sperm-ZP binding molecules?
Not yet proven/known as to which ones are responsible
What is the area between the egg cytoplasm and the ZP?
perivitelline (pv) space
What can the sperm do once in the pv space?
Bind the oolemma
What is the oolemma?
The egg plasma membrane
What is specific ab the sperm oolemma relationship?
Their binding and fusion are separable
What does the sperm-oolemma binding and fusion being separable allow?
Can prevent fusion after binding
What is the sperm oolemma binding mediated by?
Sperm IgG-like acrosomal protein, Izumo
What does izumo do during the acrosomal reaction?
Moves to the equatorial segment
What does izumo do upon oocyte binding?
Dimerizes
Which protein that isn’t izumo mediates oolemma binding?
SPACA6
Where is SPACA6 found?
Sperm plasma membrane
What is the principle Izumo receptor on eggs?
Juno
What does the sperm-oocyte interaction involve?
Tetraspanin, CD9
Role of CD9 for sperm-oocyte interaction?
organise protein complexes & plasma membrane
topology required for fusion
What happens to eggs from Juno homozygous knockouts?
They dont bind sperm
What is polyspermy?
More than one sperm fertilising
What are the two levels of polyspermy blockage?
Plasma membrane and zona block
When does the zona block occur?
After fertilisation
How does the zona block work?
Cortical granule exocytosis
What happens when the cortical granules are exocytosed?
CG exocytosis releases protease, ovastacin into perivitelline (pv) space
What does ovastacin do?
Cleaves ZP2
