1

Lecture 16: Fertilization

Animal Science 434John J. Parrish

Capacitation1951Austin - ratChang - rabbitFertilization does not occur until several

hours after sperm are placed in theuterus or oviduct

Chang Experiment - 1951

0

20

40

60

80

100

-2 -1 0 2 4 6 8

Time of Insemination (hr relative to ovulation)

OvulationOvulation

Perc

ent F

ertil

izat

ion

AfterAfter BeforeBefore

CapacitationThe changes within sperm that conferupon the sperm the ability to acrosomereact in response to the appropriatestimulus.

Zona Pellucida Cumulus Cells Follicular Fluid

Zona Pellucida Cumulus Cells Follicular Fluid

Effect of CapacitationEpididymal Ejaculated

SeminalPlasmaand/or

EpididymalSecretions

+

Capacitated

FemaleTract+

2

Model of CapacitationD F

Plasma Membrane

Cytoplasm

Nucleus

Acrosome

D F

Plasma Membrane

Cytoplasm

Nucleus

Acrosome

GAG

Plasma Membrane

Cytoplasm

Nucleus

Acrosome

GAG

Cholesterol

Chol-Acceptor

Ca2+

Ca2+

pH

cAMPActivity ofEnzymes

Activity ofEnzymes

D F CapacitationNo change in sperm morphologyMotility change– hyperactivation

cAMPPower outputcAMPPower 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

3

The Zona PellucidaThe Zona PellucidaZona

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

4

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 SurgeZona 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+

5

9080706050403020100

0

50

100

150

200

250

300

350

400

450

500

Time (m in)

Ca

lciu

m (

nM

)

9080706050403020100

0

50

100

150

200

250

300

350

400

450

500

Time (min )C

alc

ium

(n

M)

9080706050403020100

0

50

100

150

200

250

300

350

400

450

500

Time (m in)

Ca

lciu

m (

nM

)

9080706050403020100

0

50

100

150

200

250

300

350

400

450

500

Time (min)

Ca

lciu

m (

nM

)

Calcium Transients During Bovine FertilizationCalcium Transients During Bovine Fertilization Initiation of Calcium Pulse bySoluble Sperm Component

Endoplasmic ReticulumCa2+

PLCzetaPIP2

DAG

IP3

Ca2+

Oocyte

Sperm Receptor - CalciumPulse Initiation

Ca++

ER

IP3PLC

Zona Pellucida

PerivitellineSpace

Oocyte

MII

AIIMPF X

Ca2+

Pronuclei

TII

PBII

Zona Pellucida

PerivitellineSpace

Oocyte

MII

AIIMPF X

Ca2+

Pronuclei

Decondensation

Pronuclei

Zygote

TII

PBII

Zona Pellucida

PerivitellineSpace

Oocyte

Ca2+

CorticalGranules

Zona Block toPolyspermy

6

Zona Pellucida

PerivitellineSpace

Oocyte

Ca2+

CorticalGranules

Zona Block toPolyspermy

3

Blocks to Polyspermy

1

2

4

Species1. Mammals3. Invertebrates

AmphibiansFishRabbits

4. AmphibiansAvians