Human Gametogenesis and Fertilisation - Embryology · Dr Steven Fleming Honorary Associate...

Dr Steven FlemingHonorary Associate

University of Sydney

Human Gametogenesisand Fertilisation

UNSW Embryology Course 2013

August 2013August 2013 Gametogenesis & FertilisationGametogenesis & Fertilisation

Learning ObjectivesLearning Objectives

MeiosisGametogenesis and aneuploidyCapacitation and hyperactivationOvulation and oocyte maturationFertilisation and polyspermyIUI, IVF, ICSI, PICSI and IMSIAssisted reproduction and society

MeiosisGametogenesis and aneuploidyCapacitation and hyperactivationOvulation and oocyte maturationFertilisation and polyspermyIUI, IVF, ICSI, PICSI and IMSIAssisted reproduction and societyAugust 2013August 2013 Gametogenesis & FertilisationGametogenesis & Fertilisation

Meiosis 1Meiosis 1

Elder, K. and Fleming, S. (2002) Gametogenesis and Preimplantation Embryo Developmentin Preimplantation Genetic Diagnosis (eds J. C. Harper, J. D.A. Delhanty and A. H. Handyside)

Meiosis 1 (continued)Meiosis 1 (continued)

Meiosis 2Meiosis 2

Why is meiosis a highly risky cell division?

Which aneuploidies result in subfertility or infertility?

Which aneuploidies increase with increased maternal age?

Which aneuploidies result in subfertility or infertility?

Which aneuploidies increase with increased maternal age?

Hunt and Hassold (2001) Nature Reviews Genetics, 2 280-291

Aneuploidy: the scale of the problem

©Yorgos Nikas©Yorgos NikasEikonicaAthensGreece

EikonicaAthensGreece

Spermatozoa within the seminiferous tubule

SpermatogenesisSpermatogenesis

In what ways does meiosis differ during oogenesis?

What are the mechanisms underlying these differences?

Folliculogenesis/OogenesisFolliculogenesis/Oogenesis

In Vitro Maturation In Vitro Maturation

24-48 hours

Prophase I Metaphase I Metaphase II

Actin-rich domain during PB formation in mouse oocyte:

Maro and Verlhac, 2002 Nature Cell Biology 4, 281-3August 2013August 2013 Gametogenesis & FertilisationGametogenesis & Fertilisation

Why is the timing of fertilisation regulated?Why is the timing of

fertilisation regulated?What are the mechanisms in

the male and female that regulate fertilisation?

What are the mechanisms in the male and female that

regulate fertilisation?

Graafian follicle

The follicle maintains the oocyte under meiotic arrest

RFSH LH

Gap junctions

OocyteCumulus

Granulosa

FSH EGF?

FF-MAS

Granulosa cells

Primordial oocyte

Oogonia

FF-MAS

MI MIIPreovulatoryoocyte

FF-MAS?

Meiotic start and stop signalsMeiotic start and stop signals

The pathway to fertilisationThe pathway to fertilisationCapacitationHyperactivationOocyte maturationSperm-egg recognitionThe acrosome reactionSperm-egg fusionOocyte activationPronuclei formationSyngamy

CapacitationHyperactivationOocyte maturationSperm-egg recognitionThe acrosome reactionSperm-egg fusionOocyte activationPronuclei formationSyngamy

Yorgos NikasYorgos NikasEikonikaAthensGreece

EikonikaAthensGreece

Spermatozoa traversing ciliated epithelium

Acrosome reacted spermatozoa in cumulus

Sperm penetration of mature egg - DiagramSperm penetration of mature egg - Diagram

Sperm binding

Acrosome-reacting

Acrosome-reacted

Sperm-egg fusion

Sperm incorporation

Acrosome-intact

AR in Cumulus

CR=corona radiataPVS=perivitelline space ZP=zona pellucida

Sathananthan, H. (2008) Human fertilisation after IVF and ICSI in Textbook of Assisted Reproduction for Scientists in Reproductive Technology (eds S. Fleming and S. Cooke)

Sperm penetration of the zona - TEMSperm penetration of the zona - TEM

Spermatozoa penetrating the zona pellucida

Sperm – egg membrane fusion - TEMSperm – egg membrane fusion - TEM

Fusion

Midpiece

Ooplasm

Fusogenic zone

Spermatozoon binding to the oolemma

Formation of pronuclei and syngamy

How does the oocyte know it has been fertilised?

What is the mechanism by which the oocyte becomes

activated?

What is the mechanism by which the oocyte becomes

activated?

Adapted from Developmental Biology , third edition by Scott F. Gilbert

plasma mem brane of egg

sperm, not drawn t o scale

( f irst messenger)

sperm recep t or

G prote in

phosphoti dy linosit ol bis-phosphate in isolat ion

endoplasmic reticulum

cytoplasm

lumen of the ER

IP3 as second messenger

IP recepto r and calcium channel

Role of second messengers in fertilisation

Mature and pronuclear eggs – Nomarski opticsMature and pronuclear eggs – Nomarski optics

MII 1PN

2PN 3PN

Courtesy Dr.D.Payne, AdelaideAugust 2013August 2013 Gametogenesis & FertilisationGametogenesis & Fertilisation

Pronuclear ova - DiagramPronuclear ova - Diagram

Normal 2PN Dispermy

DigynyPartheno-genesis

How does the oocyteprevent polyspermy?How does the oocyteprevent polyspermy?How might polyspermy occur

unwittingly in vitro?How might polyspermy occur

unwittingly in vitro?

Fertilisation events - DiagramFertilisation events - Diagram

A: sperm-egg fusion B: second maturation division C: cortical reactionD: zona reactionE: association of male & female pronuclei

a: Sperm aster forms after sperm incorporation

activation

Sathananthan, H. (2008) Human fertilisation after IVF and ICSI in Textbook of Assisted Reproduction for Scientists in Reproductive Technology (eds S. Fleming and S. Cooke)

Cortical reaction at fertilisation - TEMCortical reaction at fertilisation - TEM

Ooplasm

Block to polyspermy – nature’s way - TEMBlock to polyspermy – nature’s way - TEM

Ooplasm

Zona morphology following fertilisation

Adapted from Developmental Biology, third edition by Scott F. Gilbert

Sperm binds egg receptor

G protein activated

Membrane potential changed

FAST BLOCK OF POLYSPERMY

phospholipase C activated (PLC)

diacylglycerol produced (DAG)

protein kinase C activated (PK-C)

cortical reaction

SLOW BLOCK OF POLYSPERMY

increase in intracellular pH

Ca released from ER

2+IP produced

IP as a second messenger in fertilization3

Na ion influx

Na /H exchanger activated

activation of egg

Fast and slow blocks to polyspermy

Ovulation inductionand

Intrauterine insemination

Ovulation inductionand

Intrauterine inseminationPatent fallopian tubesOvulatory menstrual cyclesSuccess rate = 10% - 15%Increases up to 4 attemptsTotal motile sperm count≥ 10 million

Patent fallopian tubesOvulatory menstrual cyclesSuccess rate = 10% - 15%Increases up to 4 attemptsTotal motile sperm count≥ 10 million

In vitro fertilisation (IVF)In vitro fertilisation (IVF)

Success rate = 25% - 30%

What if the sperm concentration or sperm

motility is too poor for IUI or IVF?

What if the sperm concentration or sperm

motility is too poor for IUI or IVF?

Intra-Cytoplasmic Sperm Injection (ICSI)

• Only one sperm required per egg

• Success rate = 25% - 30%

• Only one sperm required per egg

• Success rate = 25% - 30%

What if there are no sperm being ejaculated?

Retrograde ejaculation?Genital tract obstruction?Very low sperm production?

Surgical Sperm Recovery

Testicular sperm extraction

PICSIPICSI

Jakab et al (2005) Fertil Steril 84: 1665-1673

Acridine Orange FluorescenceAcridine Orange Fluorescence

Fixation with methanol and glacial acetic acid (9:1)Staining with Acridine Orange

solution for 10 minutesMetachromatic shift in

fluorescenceGreen (native, double-stranded DNA)Red (single stranded DNA breaks)

Fixation with methanol and glacial acetic acid (9:1)Staining with Acridine Orange

solution for 10 minutesMetachromatic shift in

fluorescenceGreen (native, double-stranded DNA)Red (single stranded DNA breaks)

HA selection of spermHA selection of sperm

August 2013August 2013 Gametogenesis & FertilisationGametogenesis & FertilisationYagci et al (2010) J Androl 31: 566-572

DNA integrity of HA selected spermatozoaDNA integrity of HA

selected spermatozoa

Yagci et al (2010) J Androl 31: 566-572

Variable Mean ± SD (%)Green sperm in semen 54.9 ± 2.0Green sperm outside HA spot 56.1 ± 1.9Green sperm inside HA spot 99.1 ± 0.2Red sperm in semen 45.0 ± 1.9Red sperm outside HA spot 43.9 ± 1.9Red sperm inside HA spot 0.9 ± 1.9

PICSI vs Sperm SlowPICSI vs Sperm Slow

August 2013August 2013 Gametogenesis & FertilisationGametogenesis & Fertilisation Parmegiani et al (2012) Fertil Steril

Mean ICSI procedure duration (s)

PICSI = 450.0 ± 30.5SSlow = 284.1 ± 10.1p < 0.001

Intracytoplasmic Morphologically Selected Sperm Injection (IMSI)Intracytoplasmic Morphologically Selected Sperm Injection (IMSI)

Bartoov et al (2002) J Androl 23: 1-8

RCT of ICSI vs IMSIRCT of ICSI vs IMSI

Balaban et al (2011) RBM Online 22: 472-476)

Balaban et al (2011) RBM Online 22: 472-476

ART, Ethics & SocietyART, Ethics & Society

Mitochondrial disease and ooplasmic transferHaploidisation of somatic cells to

derive gametesMicroarray CGH and sperm

selection

Mitochondrial disease and ooplasmic transferHaploidisation of somatic cells to

derive gametesMicroarray CGH and sperm

selection

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