Segregation of PrE from EPI Flashcards
Introduce PrE segregation.
PrE cell fate is for those cells of the ICM in contact with the blastocoel. They express GATA6. Later make amnion.
Epiblast cells are internal ICM express nanog. Later make embryo proper.
What are the models for segregation of PrE from EPI?
Positional model and Stochastic model.
What is the positional model? (aka time outside-time inside model)
Different ICM microenvironments created by cavitation determine cell fate.
Cells internalised in the first wave of asymmetric division at 8-16 cell stage give rise to pluripotent stem cells more likely to become EPI.
Cells internalised in the second way at the 16-32 cell stage are more likely to express GATA6 and become PrE.
What is the stochastic model?
Expression of PrE and epiblast markers overlap in morula, due to random expression of GATA6 and nanog, to give ‘salt and pepper’-like expression in early blastocyst. This is then resolved by cell sorting and/or cell death before implantation.
E.g. Cells that express GATA6 if in inner ICM will migrate to blastocoel edge or die.
This suggest blastocoel plays a role - may have migration factors or survival factors for ICM cells.
What is negative of these models?
Only use small number of embryos in labs, lots of different results. Results likely to differ between labs, difficult to make generalised model.
