Cdx2 Paper

Question 1

What was known prior to the publication of the Cdx2 paper?

3

Answer 1

• 8 cell blastomeres already show bias (outer = TE, inner = ICM)
• Oct4 is required for ICM fate
• But no known equivalent of Oct4 for the trophectoderm.

Question 2

Why did researchers see Cdx2 as a good candidate?

Answer 2

It is expressed in the early trophectoderm.

Question 3

What kind of transcription factor is Cdx2?

Answer 3

Homeobox transcription factor

Question 4

What is a homeobox transcription factor?

Answer 4

A homeobox transcription factor is a protein, encoded by a homeobox gene, that regulates the expression of other genes by binding to specific DNA sequences

Question 5

List the methods employed in the Cdx2 paper.

Answer 5

in situ hybirdization
Immunohistochemistry
Loss-of-function genetics
Embryo culturing

Question 6

What was shown by Cdx2 immunohistochemistry?

Answer 6

Cdx2 is expressed in cells of the TE lineage

Question 7

What was revealed about cultured Cdx2-/- embryos?

Answer 7

They failed to form an expanded blastocyst.

Question 8

What was found about epithelia integrity of Cdx2 mutant embryos and what immunos were used to visualize this?

Answer 8

Epithelial integrity of the TE is not maintained in Cdx2 mutant embryos.
Immunos: ZO1a+ and E-cadherin

Question 9

What was found in relation to trophectoderm markers in Cdx2 mutant blastocysts?

Answer 9

There was reduced expression of trophectoderm markers in the mutants

Question 10

What trophectoderm marker was used in the paper?

Answer 10

Integrina 7

Question 11

What was found regarding Oct4 and Nanog expression in Cdx2 mutants?

Answer 11

Oct4 and Nanog are expressed in outer cells of Cdx2 -/- blastocysts.

Question 12

What was discovered about Nanog expression in the outer cells of Cdx2 mutants?

Answer 12

Nanog is not downregulated in the outer cells of the mutants

Question 13

What was discovered about Cdx2 mutant embryos at the expanded blastocyst stage?

Answer 13

Cultured Cdx2 -/- embryos exhibit excessive cell death at the expanded blastocyst stage.

Question 14

What was discovered about Cdx2 in 2008?

Answer 14

The decision to be TE vs. ICM is made before Cdx2 is required and Cdx2 thus acts as a read-out of the decision rather than being the cause.

Question 15

What was discovered about Cdx2 in 2014?

Answer 15

Notch and Hippo pathways converge on a Cdx2 enhancer.

Question 16

What additional factors may contribute to the ICM vs. TE decision?

2

Answer 16

Amount of stress placed on the blastomere
The adhesion properties of the blastomere