Textbook; Principles of Development, Lewis Wolpert and Cheryl Tickle. Review papers; Lecture 1 and 2 Alexandre (2001) International Journal of Developmental Biology 45, p Rossant (2001) Stem Cells 19, p Yamanaka et al, (2006). Developmental Dynamics 235, p Katsuyoshi and Hamada, (2012) Development 139, p3-14 Lecture 3 and 4 Arnold and Robertson (2009) Nature reviews Molecular cellular biology, 10, p Robb and Tam (2004) Seminars in Cell and Developmental biology 15, p43-54 Hayashi et al (2007) Science 316, p Hashimoto and Hamada (2010), Curr Opin Genet Dev 20, p433-7 Hanna et al (2010) Cell 143, p Yamanaka and Blau (2010) Nature 465, p 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 days E (embryo stage) = dpc (days post coitum). Most commonly referred to from 0.5 onwards as 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 days

Early Post-implantation Development

Gastrulation and Beyond

Extraembryonic tissues

Germ layers, Ectoderm, Mesoderm, and Endoderm, give rise to all tissues of 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 Replication initiation M-phase hr post fertilization 0 Second polar body Zona 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, p374-6 McGrath and Solter, (1984) Cell 37, p 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, p cell embryo 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,

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