ABIO303: Mammalian and Vertebrate Fertilization

Where does the acrosomal reaction occur in vertebrates?

- At the level of the cumulus or zona pellucida.

Where is Izumo expressed?

- On the sperm surface; essential for sperm-egg fusion.

What is ZP2 cleavage and why is it important?

- ZP2 is cleaved after fertilization to prevent additional sperm binding (blocks polyspermy).

What happens if ZP2 cleavage is prevented?

- The zona pellucida remains sperm-binding, leading to polyspermy.

What does Juno do after fertilization?

- It is shed from the egg membrane to prevent further sperm fusion.

What happens during sperm capacitation?

- Sperm membrane composition changes, enhancing motility and readiness for acrosome reaction.

What guides sperm toward the egg?

- Thermotaxis, chemotaxis, and rheotaxis (chemical and physical cues).

What determines sperm-egg fusion?

- Izumo1 on sperm and Juno on egg interact to enable membrane fusion.

What factors control sperm motility toward the egg?

- pH, temperature gradients, and chemoattractants.

What role does PLCζ play?

- It triggers Ca²⁺ oscillations in the egg to initiate embryonic development.

What is sperm cooperation?

- In some species, sperm form aggregates that swim more efficiently toward the egg.

What occurs in mice lacking ZP3?

- Sperm cannot bind to the zona pellucida, preventing fertilization.