Fig. 6. Diverse behaviour of GFP-positive cells contributing to the PrE layer in Pdgfra^H2B-GFP/+ embryos. (A) 3D reconstructions of z-stacks taken during fluorescence time-lapse imaging of a single Pdgfr^H2B-GFP/+ blastocyst during PrE formation. GFP-positive cells are initially randomly distributed throughout the ICM, but then segregate progressively to the surface of the ICM in contact with the blastocyst cavity. Some GFP-positive cells stay on the cavity throughout the movie (dark blue dot). Note the intercalation of GFP-positive cells highlighted by magenta and red dots. During PrE layer formation, GFP-positive cells remaining in the EPI can undergo apoptosis (arrowhead) or downregulate GFP expression, in contrast to cells in the PrE, which upregulate GFP expression (pale blue dot). A weakly GFP-positive cell is shown migrating away from the cavity (yellow dot). Scale bar: 20 µm. (B) Relative contribution of different types of cell behaviour to PrE segregation.