Lecture 16: Fertilization

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Lecture 16 Fertilization

• Animal Science 434
• John J. Parrish

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Capacitation

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

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Chang Experiment - 1951
Ovulation
After
Before
Percent Fertilization
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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

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Effect of Capacitation
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Model of Capacitation
D
F
Acrosome
Nucleus
Cytoplasm
Plasma Membrane
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Acrosome
Nucleus
Cytoplasm
Plasma Membrane
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Ca2
Cholesterol
Acrosome
Nucleus
Activity of Enzymes
Cytoplasm
Plasma Membrane
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Capacitation

• No change in sperm morphology
• Motility change
• hyperactivation

cAMP Power output
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The Acrosome Reaction
Plasma Membrane
Acrosin Hyaluronidase
Acrosome
Nucleus
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Modification of the Equitorial Region
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The Zona Pellucida
ZP1 ZP2 ZP3
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Sperm Interaction with the Zona
Attachment
Zona Pellucida
Binding
ZP3
Acrosome Reaction Induction
Acrosome Reaction
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Secondary Binding
Zona Pellucida
Zona Penetration
Motility
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Zona Pellucida
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Sperm tract through zona pellucida
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6-12 hr
18-24 hr
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Maturation Promoting Factor(MPF)
LH Surge
Metaphase Promoting Factor
Primary Oocyte
GVBD
Metaphase I
GV-Intact
PB-1
Ovulation
Secondary Oocyte
Metaphase II
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Zona Pellucida
Oocyte
Perivitelline Space
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Zona Pellucida
Oocyte
Perivitelline Space
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Zona Pellucida
Oocyte
Perivitelline Space
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Zona Pellucida
Oocyte
Perivitelline Space
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Zona Pellucida
Oocyte
Perivitelline Space
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Calcium Transients During Bovine Fertilization
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Initiation of Calcium Pulse by Soluble Sperm
Component
DAG
Oocyte
PIP2
PLCzeta
IP3
Ca2
Ca2
Endoplasmic Reticulum
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Sperm Receptor - Calcium Pulse Initiation
PLC
Ca
IP3
ER
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Zona Pellucida
Oocyte
MPF
Perivitelline Space
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Zona Pellucida
Oocyte
Zygote
Perivitelline Space
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Zona Pellucida
Oocyte
Zona Block to Polyspermy
Perivitelline Space
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Zona Pellucida
Oocyte
Zona Block to Polyspermy
Cortical Granules
Perivitelline Space
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Blocks to Polyspermy
Species 1. Mammals 3. InvertebratesAmphibiansF
ishRabbits 4. AmphibiansAvians
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3
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Sperm acrosomal region binds to sperm receptor on
zona
Initiates completion of Meiosis II and release of
2nd polar body
Perivitelline Space
1st Polar Body
Vitelline Membrane
Zona Pellucida
Initiates - Zona Vitelline Reaction
Cortical Granule
ZP3
Binding
Fusion
Cortical Granule Release
Zona Reaction
Initiation of Acrosome Reaction
Excluded Sperm
Continuation of Reaction
Acrosome-Reacted Sperm
Penetration
Zona and Vitelline Reactions block polyspermy
Sperm penetrates zona
Redrawn from Wasserman, P.M. 1988 Scientific
American. p78