4- Signalling Pathways Flashcards
what is the first cell fate decision of the mammalian embryo? at what cell stage does it occur?
first cell fate decision - 16-cell embryo; differentiation of a cell into inner cell mass or trophectoderm
occurs between the 8- to 16-cell stage
what is the second cell fate decision of the mammalian embryo?
inner cell mass of a blastocyst - differentiating into epiblast or hypoblast
the first cell fate decision is governed by the expression of specific TFs - what TFs for ICM cells (4)? what TFs for trophectoderm cells (3)?
ICM - Oct4, Sox2, Sall4, Nanog
TE - Tead4, GATA2, Cdx2
what three factors determine the first cell fate decision of cells in the 16-cell embryo? describe how
- polarity
- position of embryo
- differential expression of specific TFs
describe the influence of the Hippo signalling pathway in determining the first cell fate decision
Tead4 is expressed in both TE and ICM cells at the start - polarity of TE cells means inactive Hippo signalling pathway
allows Yap protein to translocate from cytoplasm to nucleus - partners & activates Tead4 - induces expression of TE-specific TFs (GATA4, Cdx2)
describe the Notch-Delta pathway and how it creates binary fate decisions via lateral inhibtion
Notch-Delta pathway - Notch & Delta expressed on both cells, pathway is short-range; requires direct cell-cell contact
how does lateral inhibition via Notch-Delta influence neurogenesis?
what other signalling pathway is involved in the first cell fate decision besides Notch? how?
what signals or features bias initial Delta expression in neurogenesis?
expression of proneural genes - cells expressing proneural genes = slightly higher Delta expression
through Notch-Delta signalling, small differences in Delta are amplified by lateral inhibition - that cell ends up with high Delta activity, inducing a neural fate (neuron)
explain how a tiny difference in Delta expression between two cells can lead to distinct fates
