Lecture 16 Fertilization Animal Science 434 John J

Lecture 16: Fertilization Animal Science 434 John J. Parrish

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

Percent Fertilization Chang Experiment - 1951 Ovulation After Before

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

Effect of Capacitation Epididymal Seminal + Plasma Ejaculated Female + Tract Capacitated

Model of Capacitation D F Acrosome Nucleus Cytoplasm Plasma Membrane

D F D F Chol-Acceptor GAG Ca 2+ Cholesterol Acrosome Nucleus Activity of Enzymes p. H c. AMP Cytoplasm Plasma Membrane Ca 2+

Capacitation l No change in sperm morphology l Motility change – hyperactivation c. AMP Power output

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

Modification of the Equitorial Region

The Zona Pellucida

Sperm Interaction with the Zona Attachment Z o n a P e l l u c i d a Binding ZP 3 Acrosome Reaction Induction Acrosome Reaction

Z o n a Secondary Binding ZP 2 P e ZP 2 l l u ZP 2 c i d a Zona Penetration Motility

Zona Pellucida

Sperm tract through zona pellucida

6 -12 hr 18 -24 hr

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

Zona Pellucida Oocyte Ca 2+ Perivitelline Space

Calcium Transients During Bovine Fertilization

Initiation of Calcium Pulse by Soluble Sperm Component

Calcium Pulse Initiated by IP 3 Ca++ IP 3 ER

Zona Pellucida Oocyte Pronuclei TII Perivitelline Space PBII AII Ca 2+ X MPF MII

Zona Pellucida Oocyte Decondensation Pronuclei Zygote Pronuclei TII Perivitelline Space PBII AII Ca 2+ X MPF MII

Zona Pellucida Oocyte Ca 2+ Cortical Granules Perivitelline Space Zona Block to Polyspermy

Blocks to Polyspermy Species 1. Mammals 3. Invertebrates Amphibians Fish Rabbits 4. Amphibians Avians 1 2 3 4

Sperm acrosomal region binds to sperm receptor on zona Perivitelline Space 1 st Polar Body Zona Initiates Pellucida Zona & Vitelline Membrane Cortical ZP 3 Granule Binding Vitelline Fusion Reaction Cortical Granule Release Zona Reaction Initiation of Acrosome Reaction Continuation of Reaction Initiates completion of Meiosis II and release of 2 nd polar body Acrosome-Reacted Sperm penetrates zona Redrawn from Wasserman, P. M. 1988 Scientific American. p 78 Excluded Sperm Penetration Zona and Vitelline Reactions block polyspermy