2. Neurulation in the chick, after the node regresses

3. Typical vertebrate organization of the chick embryo (and >200 selector gene domains) **Or wait until the embryo lifts off the yolk sac Notochord “Somatic mesoderm” “Visceral mesoderm”

4. Extra-embryonic membranes of the chick

5. Amnion and chorion: contain ectoderm and somatic mesoderm Yolk sac and allantois: contain enododerm and visceral mesoderm

6. Chick development: Formation of the allantois

8. Human or mouse embryo: pre-implantation stages 4. hatching 1. compaction gene expression starts 128 cell Day 7-human Day 5.5-mouse 2 2. Blastocyst cavity formation 3. Cell sorting (hypo vs. epi)

9. Mouse pre-implantation stages: compaction, apical-basal polarization, cleavage, blastocyst cavity formation Compaction at the late 8-cell stage, With apical-basal polarization of cells 128-cell blastocystcompaction 128-cell blastocyst

10. Human 128cell blastocyst before/during hatching Mouse embryonic stem cells (ES cells) from the inner cell mass, growing in a culture dish Injection of ES cells into the blastocyst cavity “zona” Holding pipet Injection pipet Oct4 gene expression in epiblast

11. Mouse transgenesis (insertion of a foreign gene into the mouse genome) Dr. Mario Capecchi-1984 Univ. of Utah Gene for red fluorescent protein (RFP) Gene for green fluorescent protein (GFP) from jellyfish (e.g., GFP with promoter) FOSTER MOTHER (2x) (random) non-homologous integration Green ES cells

12. Implantation of the human blastocyst in the uterine wall. Mouse implantation is also invasive, like human Syncytio- trophoblast Maternal tissue Uterine fluid

13. Role of the AVE (anterior visceral endoderm) in establishing the anterior-posterior axis of the mouse embryo Cylindrical SymmetryBilateral Symmetry A P Cerberus (anti-Nodal) Dkk (anti-Wnt) Lefty (anti-Nodal) Otx2 Anterior neural ectoderm Nodal, Vg1, Cripto (co-receptor For Nodal and Vg1) Endo-mesoderm induction Day 5.25 Day 5.5 Day 6.25 or hypoblast Endo-mesoderm induction, Primitive streak Nodal, wnt, brachyury, fgf expressed Epiblast ectoderm