Holy week 5 - regulators of dvlp

Question 1

Regulative vs mosaic dvlp?

Answer 1

In regulative development, blastomeres initially have similar developmental potencies, each capable of giving rise to a complete embryo. (Induction)
In mosaic development, cell fate is already assigned during cleavage. (Asymmetric division)

Question 2

By which mechanism of dvlp are identical twins produced?

Answer 2

Regulative

Question 3

Regulation of inner cell mass vs trophoblast?

Answer 3

Hippo signaling.

Question 4

Regulation of epiblast vs hypoblast?

Answer 4

Oct4, Nanog, Sox = epiblast
GATA expression = hypoblast
(Cdx2 also plays a role)

Question 5

Regulation of decision to form 3 germ layers (gastrulation)?

Answer 5

High Oct4/low BMP4 = embryonoic stem cell self-renewal
High Oct4/high BMP4 = mesoderm
Low Oct4/high BMP4 = ectoderm
Low Oct4/low BMP4 = neuroectoderm

Question 6

Unipotent:

Answer 6

Can give rise to just one type of cell

Question 7

Multipotent

Answer 7

Multipotent: can give rise to multiple (but not all) cell types

Question 8

Pluripotent

Answer 8

Pluripotent: can give rise to all embryonic cell types and structures

Question 9

Totipotent

Answer 9

Totipotent: can give rise to all embryonic and extra-embryonic cell types and structures

Question 10

Describe the process of forming dorsal-ventral axis.

Answer 10

It is formed by notochord control. Sonic hedgehog (Shh) is released from ventral surface and TGF (BMP) is released from dorsal surface.

Question 11

Describe the process of forming left-right axis.

Answer 11

Cilia beat unidirectionally from primitive node causing leftward flow of fluid which increases Nodal. Nodal stimulates the production of itself and another signaling molecule called Lefty, which is antagonistic to nodal (nodal and lefty both belong to the TGF-b family). Not enough lefty is produced to inhibit nodal on the left side, but it is enough to inhibit the lesser amounts of nodal expressed on the right side.

Question 12

What is responsible for creating anterior-posterior axis?

Answer 12

Homeobox genes (HOX)
(Retonoic acid seems to make more posterior)

Question 13

What was example of eye development in class showing?

Answer 13

It was showing sequential induction secondary to Fibroblast growth factor 8 signaling.

Question 14

Name the big 5 of developmental signaling pathways and what they do?

Answer 14

• TGF pathway (transforming growth factor; includes TGF-b, BMP, Activin, and Nodal proteins) - Mesoderm & endoderm; osteogenesis; L/R asymmetry
• Weird hand pictures
• Hedgehog pathway - Numerous tissues; neural fate along DV axis; AP digit identity
• Disease with deviation from midline
• FGF pathway (fibroblast growth factor; includes a number of FGFs) - Activate RAS and MAP kinase pathway.
• Dwarfism
• Wnt pathway - intestinal crypt stem cells, hematopoiesis, neural crest
• Cancer with blocking of APC
• Notch pathway - Hematopoiesis, neural development, somitogenesis
• Alagille syndrome - facial and organ abnormalities

Question 15

What regulates EMT and MET (epithelialgmesenchymal and mesenchymalgepithelial transitions)?

Answer 15

EMT: TGF-b, FGF, Wnt, and Notch
MET: BMP
These signaling pathways activate the expression of transcription factors like Snail, which regulate genes involved in motility and adhesion.

Question 16

What is Snail?

Answer 16

Snail (a transcription factor) represses cadherin, claudin and occludin expression, which results in loss of adherens and tight junctions.

Question 17

What is role of cadherins in EMT and MET?

Answer 17

Cadherins sort out cells based on which they express. Loss of cadherins is associated with metastasis of cancer.