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Understanding Sperm Capacitation and Fertilization in Mammals: Key Mechanisms and Processes

This lecture delves into the critical processes of sperm capacitation and fertilization, detailing the laboratory experiments conducted by Chang in 1951 involving rats and rabbits. It emphasizes the importance of capacitation, which prepares sperm to undergo the acrosome reaction necessary for fertilization. The discussion includes the physiological changes sperm undergo, interactions with the zona pellucida, and the biochemical factors such as calcium transients and maturation promoting factors essential for successful fertilization. Key mechanisms are explored to enhance understanding of reproductive biology.

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Understanding Sperm Capacitation and Fertilization in Mammals: Key Mechanisms and Processes

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Presentation Transcript

  1. Lecture 16: Fertilization Animal Science 434 John J. Parrish

  2. Capacitation • 1951 • Austin - rat • Chang - rabbit • Fertilization does not occur until several hours after sperm are placed in the uterus or oviduct

  3. Chang Experiment - 1951 Ovulation After Before Percent Fertilization

  4. Capacitation The changes within sperm that confer upon the sperm the ability to acrosome react in response to the appropriate stimulus. • Zona Pellucida • Cumulus Cells • Follicular Fluid

  5. Epididymal Ejaculated Capacitated Seminal Plasma and/or Epididymal Secretions Female Tract + + Effect of Capacitation

  6. Model of Capacitation D F Acrosome Nucleus Cytoplasm Plasma Membrane

  7. GAG D F Acrosome Nucleus Cytoplasm Plasma Membrane

  8. Chol-Acceptor GAG D F Ca2+ pH cAMP Ca2+ Cholesterol Acrosome Nucleus Activity of Enzymes Cytoplasm Plasma Membrane

  9. Capacitation • No change in sperm morphology • Motility change • hyperactivation cAMP Power output

  10. Fused Plasma Membrane and Outer Acrosomal Membrane The Acrosome Reaction Plasma Membrane Acrosin Hyaluronidase Acrosome Nucleus

  11. Modification of the Equitorial Region

  12. The Zona Pellucida ZP1 ZP2 ZP3

  13. Sperm Interaction with the Zona Attachment Zona Pellucida Binding ZP3 Acrosome Reaction Induction Acrosome Reaction

  14. ZP2 ZP2 ZP2 ZP2 Secondary Binding Zona Pellucida Zona Penetration Motility

  15. Zona Pellucida

  16. Sperm tract through zona pellucida

  17. 6-12 hr 18-24 hr

  18. MPF MPF MPF MPF Maturation Promoting Factor(MPF) LH Surge Metaphase Promoting Factor Primary Oocyte GVBD Metaphase I GV-Intact PB-1 Ovulation Metaphase II Secondary Oocyte

  19. Ca2+ Ca2+ Ca2+ Ca2+ Zona Pellucida Oocyte Perivitelline Space

  20. Ca2+ Ca2+ Ca2+ Ca2+ Zona Pellucida Oocyte Perivitelline Space

  21. Ca2+ Ca2+ Ca2+ Ca2+ Zona Pellucida Oocyte Perivitelline Space

  22. Ca2+ Ca2+ Ca2+ Ca2+ Zona Pellucida Oocyte Perivitelline Space

  23. Ca2+ Ca2+ Ca2+ Ca2+ Zona Pellucida Oocyte Perivitelline Space

  24. Calcium Transients During Bovine Fertilization

  25. Initiation of Calcium Pulse by Soluble Sperm Component DAG Oocyte PIP2 PLCzeta IP3 Ca2+ Ca2+ Endoplasmic Reticulum

  26. Sperm Receptor - Calcium Pulse Initiation PLC Ca++ IP3 ER

  27. Pronuclei Ca2+ AII X TII MII PBII Zona Pellucida Oocyte MPF Perivitelline Space

  28. Decondensation Pronuclei Pronuclei Ca2+ AII X TII MPF MII PBII Zona Pellucida Oocyte Zygote Perivitelline Space

  29. Ca2+ Cortical Granules Zona Pellucida Oocyte Zona Block to Polyspermy Perivitelline Space

  30. Ca2+ Zona Pellucida Oocyte Zona Block to Polyspermy Cortical Granules Perivitelline Space

  31. Blocks to Polyspermy Species 1. Mammals 3. InvertebratesAmphibiansFishRabbits 4. AmphibiansAvians 1 2 3 4

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