Textbook; Principles of Development, Lewis Wolpert and Cheryl Tickle. Review papers;Lecture 1 and 2 Alexandre (2001) International Journal of Developmental Biology 45, p457-467 Rossant (2001) Stem Cells 19, p477-82 Yamanaka et al, (2006). Developmental Dynamics 235, p2301-2314 Katsuyoshi and Hamada, (2012) Development 139, p3-14 Lecture 3 and 4 Arnold and Robertson (2009) Nature reviews Molecular cellular biology, 10, p91-103 Robb and Tam (2004) Seminars in Cell and Developmental biology 15, p43-54 Hayashi et al (2007) Science 316, p394-396. Hashimoto and Hamada (2010) , Curr Opin Genet Dev 20, p433-7

Hanna et al (2010) Cell 143, p508-525. Yamanaka and Blau (2010) Nature 465, p704-712

Reading list

Model systems for studying vertebrate development

Positional informationCell Fate

Anterior (Head)

Posterior (Tail)

Dorsal (Back)Ventral (Front)

Left

Right

Overview of Lectures

Lecture 1

• Overview of early mammalian development• Fertilisation and parthenogenesis • Mosaic vs regulated development

You should understand

• Non-equivalence of maternal and paternal genomes • Mammalian development is highly regulated

In utero development in mouse occurs over 19-21 days

• E (embryo stage) = dpc (days post coitum). Most commonly referred to from 0.5 onwardsas mating takes place at night.

• Preimplantation development occurs up to E3.5. All other development occurs postimplantation.

Preimplantation Development

Trophectoderm

Primitive (primary) endoderm

Inner cell mass/Primitive ectoderm

Cleavage stages

Zona pelucida

Blastocoel cavity

Activation of embryonic genome

Blastomere

0 1 2 3 4 days

Early Post-implantation Development

Gastrulation and Beyond

Extraembryonic tissues

Germ layers, Ectoderm, Mesoderm, and Endoderm, give rise to all tissuesof the developing embryo

Blastocyst

Non-equivalence of maternal and paternal genomes

• Penetration of cumulus cells

• Acrosomal reaction penetrates zona pellucida made up of glycoproteins

• Sperm and egg plasma membranes fuse and sperm nucleus enters egg.

• Fertilization triggers dramatic release of calcium in the egg, setting in train completion of female meiosis etc.

Pronuclear Maturation

12 24

Replicationinitiation

M-phase

hr post fertilization0

Second polar bodyZona pelucida

• Maternal and paternal haploid genome remains separate (pronuclei) until first metaphase.

Male pronucleus. Female pronucleus.

Syngamy

Parthenogenesis

• Limited viability suggests either that sperm/fertilization confers essential properties for development or that maternal genome alone is incapable of supporting development

Parthenogenetic activation

- Genetic background- In vitro manipulation- Pronase/hyalouronidase- Heat shock- Ethanol- Strontium chloride

• Oocytes can be activated in the absence of fertilization, leading to parthenogenetic development

• Parthenogenetic embryos have limited viability, contrasting with other model organisms

Non-equivalent contribution of maternal and paternal genomes

?Recipient zygote

Donor zygote

Barton, Surani , Norris (1984)Nature 311, p374-6McGrath and Solter, (1984)Cell 37, p179-183

• Gynogenetic embryos have retarded growth/development of extraembryonic tissues

• Androgenetic embryos have retarded growth/development of embryonic tissues

Epigenesis vs Preformation

Nicolas Hartsoeker, 1695

• Roux (1888) shows ‘mosaic development’ of frog embryo following ablation of one cell in two-cell embryo – formation of ‘half’ embryo.• Driesch (1895) finds opposite is true for sea urchin, normal albeit smaller embryo develops from one of two cells – ‘regulated development’.

Mosaic and Regulated development

Tarkowski, (1959)Nature 184, p1286-7

2-cellembryo

Donor

Recipient

Regulated development in mouse embryos

Chimeras from aggregaton of 8-cell stage embryos

8-cell embryos

Remove zona pellucida

Aggregate in dish

Culture in vitro

Chimeric blastocyst

Transfer to foster mother

Chimeric progeny

Tarkowski (1961) Nature 190, 857-860

Chimeras from transfer of ICM cells

• Gardner later demonstrated this for ICM cells of the blastocyst stage embryo. • In these experiments ICM cells did not contribute to trophectoderm or primitive endoerm lineages

Gardner (1968), Nature 220, p596-7

End lecture 1