Profiling the transient gastrulation inducing property of amnion-like cells.
Studies in the mouse have established that communication between the trophectoderm and the epiblast is crucial for initiating gastrulation. In the primate embryo, the amnion rather than the trophectoderm is directly juxtaposed to the epiblast and may play this role. To model the interactions between the amnion and epiblast, we differentiated human pluripotent stem cells (hPSCs) to amnion-like cells (AMLCs) and juxtaposed them in a controlled manner with undifferentiated hPSCs, which represent the epiblast. We found that juxtaposition between these cell types is sufficient to initiate a range of cell behaviors associated with gastrulation including organized differentiation to primitive streak and downstream mesendodermal cell fates and directed cell migration out of the primitive streak region. Performing knockout experiments specifically in either the epiblast or amnion compartment revealed intricate crosstalk that is required to properly initiate gastrulation. In particularly, using knockouts of NODAL we show that Nodal signaling in both the amnion and epiblast is required for gastrulation patterning. Finally, we show that inductive ability is a transient property acquired during amnion differentiation, and that cells that differentiate from this inductive state acquire an extraembryonic mesenchyme identity. This study establishes a system to study epiblast-amnion communication and shows that this communication is sufficient to initiate gastrulation in the epiblast. Overall design: RNAseq profiling of ESI017 human emrbyonic stem cells undergo AMLC treatment (BMP4 50ng/ml, SB431542 10 µM) for 2 days and 4 days. An experiment investigating Wnt activation dynamic is run in parallel with the experiment mentioned above. Wnt3a and Chir treated. ESI017 is collected 18 hours or 6 hours after the treatment. Reanalysis of control GSM7834978 from GSE245027 was performed for this study. *************************************************************** The table below lists GEO accessions reused/reanalyzed for this study. ***************************************************************