Lecture 16: Fertilization

Animal Science 434John J. Parrish

Capacitation

1951Austin - ratChang - rabbit Fertilization does not occur until several

hours after sperm are placed in the uterus or oviduct

Chang Experiment - 1951

OvulationOvulation

Per

cen

t F

erti

liza

tio

n

AfterAfter BeforeBefore

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

Zona Pellucida

Cumulus Cells

Follicular Fluid

Effect of CapacitationEpididymal Ejaculated

SeminalPlasmaand/or

EpididymalSecretions

+

Capacitated

FemaleTract

+

DF (BSP in Bovine)

Plasma Membrane

Decapacitation Factor – Stabilizes plasma membrane and inhibits a premature acrosome reaction

CholesterolAcceptor

BSPHeparin

Plasma Membrane

CholesterolAcceptor

BSPHeparin

Plasma Membrane Raft MigrationZp bindingclustering

sAC

HCO3-

HCO3-

(+)

(-)

cAMP

PK-A

PTK Ptyr-Ptase

Protein Tyrosine Phosphorylation

(-)

(+)

(+)

(+)

pHi

(+)

H+

H+

CholesterolAcceptor

BSPHeparin

Raft MigrationZp bindingclustering

CO2 + H2O H2CO3 H+ + HCO3

-

Carbonic Anhydrase

Diffusion

Extracellular Space

sAC

HCO3-

HCO3-

(+)

(-)

cAMP

PK-A

PTK Ptyr-Ptase

Protein Tyrosine Phosphorylation

(-)

(+)

(+)

(+)

pHi

(+)

H+

H+

CholesterolAcceptor

BSPHeparin

Raft MigrationZp bindingclustering

ATP ADPCa2+

ATP ADP

Ca2+

Acrosome

Ca2+

CholesterolAcceptor

BSPHeparin

Raft Migration

ATP ADPCa2+

ATP ADP

Ca2+

Acrosome

Ca2+

Ca2+

sAC

Ca2+HCO3-

HCO3-

(+)

(-)

(+)

cAMP

PK-A

PTK Ptyr-Ptase

Protein Tyrosine Phosphorylation

(-)

(+)

(+)

(+)

pHi

(+)

H+

H+

CholesterolAcceptor

BSPHeparin

Ca2+

Acrosome

Ca2+

Capacitation

No change in sperm morphologyMotility change– hyperactivation

cAMP

Power output

cAMP

Power output

The Acrosome ReactionPlasma Membrane

Acrosome

Fused PlasmaMembrane and

Outer AcrosomalMembrane

Fused PlasmaMembrane and

Outer AcrosomalMembrane

Nucleus

AcrosinHyaluronidase

AcrosinHyaluronidase

Modificationof the

EquitorialRegion

Modificationof the

EquitorialRegion

The Zona PellucidaThe Zona Pellucida

Zona Pellucida

ZP3

Attachment

Binding

Acrosome ReactionInduction

Acrosome Reaction

Sperm Interaction with the Zona

Zona Pellucida

ZP2

ZP2

ZP2

ZP2

Secondary Binding

Zona Penetration

MotilityMotility

Zona Pellucida

Sperm tract through zona pellucidaSperm tract through zona pellucida

6-12 hr6-12 hr

18-24 hr18-24 hr

Maturation Promoting Factor(MPF)

Metaphase Promoting FactorMetaphase Promoting Factor

MPF MPF

MPFMPF

Primary Oocyte

GV-Intact

GVBD Metaphase I

PB-1

Secondary OocyteMetaphase II

Ovulation

LH Surge

Zona Pellucida

PerivitellineSpace

Oocyte

Ca2+

Ca2+

Ca2+

Ca2+

Zona Pellucida

PerivitellineSpace

Oocyte

Ca2+

Ca2+

Ca2+

Ca2+

Zona Pellucida

PerivitellineSpace

Oocyte

Ca2+

Ca2+

Ca2+

Ca2+

Zona Pellucida

PerivitellineSpace

Oocyte

Ca2+

Ca2+

Ca2+

Ca2+

Zona Pellucida

PerivitellineSpace

Oocyte

Ca2+

Ca2+

Ca2+

Ca2+

Calcium Transients During Bovine FertilizationCalcium Transients During Bovine Fertilization

Initiation of Calcium Pulse by Soluble Sperm Component

Endoplasmic Reticulum

Ca2+

PLCzetaPIP2

DAG

IP3

Ca2+

Oocyte

Zona Pellucida

PerivitellineSpace

Oocyte

MII

AIIMPF X

Ca2+

Pronuclei

TII

PBII

Zona Pellucida

PerivitellineSpace

Oocyte

MII

AIIMPF X

Ca2+Ca2+

Pronuclei

Decondensation

Pronuclei

Zygote

TII

PBII

Zona Pellucida

PerivitellineSpace

Oocyte

Ca2+

CorticalGranules

Zona Block to Polyspermy

Zona Pellucida

PerivitellineSpace

Oocyte

Ca2+

CorticalGranules

Zona Block to Polyspermy

3

Blocks to Polyspermy

1

2

4

Species

1.Mammals

3.InvertebratesAmphibiansFishRabbits

4.AmphibiansAvians

Gamete Aging

Oocyte life span approx. 6 – 12 hours after ovulation

Sperm life span approx. 24 – 48 hours after ejaculation