First and second cell fate decisions in mammalian development Flashcards
When do inner cell mass cells and trophectoderm cells become morphologically apparent?
These cells become morphologically apparent at the blastocyst stage, but molecular changes occur before this
What does the first cell fate decision separate?
first cell fate decision separates the ICM and TE in the blastocyst
What does the second cell fate decision give rise to?
second cell fate decision gives rise to the epiblast and hypoblast
What is TE and ICM governed by?
TE and ICM are governed by transcription factors and the expression of transcription
What are TE cells associated with?
TE cells are associated with the expression of Tead4 and Cdx2 transcription factors
What are the ICM cells associated with?
ICM cells are associated with the expression of Nanog, Oct4, Sox3, Sal4
What binary decisions do ICM cells undergo?
ICM cells makes a binary decision to give rise to epiblast and primitive endoderm. Gata6 transcription factor is associated with epiblast cell fate. Nanog transcription factor is associated with primitive endoderm cell fate.
What transcription factors are expressed in ICM?
Nanog, Oct3/4, Sox3, Sal4
What transcription factors are expressed in TE?
Gata4, Cdx2
What are the 2 possible mechanisms used for the generation of multiple cell types and polarity?
Localised maternal determinant
No localised maternal determinant
What is localised maternal determinant?
Something is passed down to the mother. The polarity within the embryo is set aside. Early polarisation may lead to early asymmetric inheritance. The asymmetric inheritance is then reinforced to give rise to 2 different cell types.
What is no localised maternal determinant?
External influences can determine polarity of embryo
What is meant by cells being equivalent upto the 8-16 cell stage?
If you were to remove a single cell, it can give rise to a normal embryo
How are initial differences established between cells?
It is possible for early asymmetry to occur, and early cells aren’t homogenous. The early asymmetry may be provided by the polar bodies. As the cells divide, some cells will end up toward the outside of the cell whereas others will end up towards the inside of the cluster of cells. Some cells are partly reliant on position and divide in different ways. Some divide symmetrically and become equivalent. Some divide asymmetrically and the cell may take up a different fate. During the 16 cell phase, the outside cells will develop polarity and epithelium phenotype. As the blastocyst is formed, there’s differences within the ICM. Some may be lying closer to the blastocoel and may receive signals from it.
How is Cdx2 mRNA distributed within an embryo?
Cdx2 mRNA is not distributed equally within an embryo
