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

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.

Regression of Hensen’s Node Stage 6 Stage 7 Stage 4 18hr Stage 5 N N N Stage 8 Stage 7 N Stage 9 Stage 10 36hr Regression of Hensen’s Node

Neurulation in the chick, after the node regresses

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

Extra-embryonic membranes of the chick

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

Chick development: Formation of the allantois

Start mouse development: fertilization to the 128 cell blastocyst

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

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

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

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

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