1. Finish chick early development: Node regression, notochord formation, and neurulation in the ectoderm Organization of the body axis, cross-section Development of 4 extra-embryonic tissues

2. Regression of Hensen’s Node: 1) progressively laying down notochord toward the posterior tip and 2) progressively shutting down endomesoderm induction and waterfall ingression thru the streak.

3. Regression of Hensen’s Node
Stage 6
Stage 7
Stage hr
Stage 5 N N N
Stage 8
Stage 7 N
Stage 9
Stage 10 36hr
Regression of Hensen’s Node

4. Neurulation in the chick, after the node regresses

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

6. Extra-embryonic membranes of the chick

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

8. Chick development: Formation of the allantois

9. Start mouse development: fertilization to the 128 cell blastocyst

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

11. 128-cell blastocyst
compaction
128-cell blastocyst
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

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

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

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