Cleavage to Gastrulation... initial commitment and differentiation Flashcards
1
Q
zygote to trophoblast CELLULAR
A
- cellular:
- cells of early embryo morphologically identical
- totipotency until 16 cell stage
- innter and outer cells… (inner mass, trophoblast)
- trophoblast (supporting structures, placenta)
- ICM cells pluripotent
- ICM cells = ES cells
2
Q
Early cleavage cells divide..
A
- symmetrically or asymmetrically
- polar cells (apical and basal surfaces)
- nonpolar cells (inner cells)
3
Q
zygote to trophoblast MOLECULAR
A
- cells even at 2, 4, 8 cell stage have molecule differences
- noisy gene expression (works itself out)
- regulative ability
- Oct4 key TF
- oct4 in all cells in morula stage, then only in ICM
4
Q
Oct4 expression and function
A
- development of pluripotent cells in ICM and ES
- essential TF:
pluripotency maintainance
cell differentiation
transdifferentiation
reprogramming to iPS cells
5
Q
differentiation into trophopblast and ICM
A
- involves oct4 and Cdx2, reciprocal interation
- see figure
6
Q
What determines if the cell expresses oct4 or cdx2
A
- something happens to cause differential expression of cdx or oct4
7
Q
-
A
-
8
Q
pluripotency network
A
- formed by TFs oct4, nanog, sox2… up/downregulate to maintain pluripotency
9
Q
ICM to epiblast/hypoblast
A
- nanog and gata6 orchestrate differentiation to epiblast and hypoblast in the last blastocyst
- turn inner mass into 2 layers
- see figure
10
Q
by the time of implantation
A
- blastocyst developed:
epiblast
primitive endoderm (hypoblast)
and trophoectodderm (TE) - extraembryonic tissues are critical to sustain embryonic growth, and pattern embryo
11
Q
multistep model of EPI/PrE lineage formation
A
- initial expression of TFs is followed by progression towards stabilised salt and pepper pattern of PrE (Gata6) and EPI (Nanog) expression