The crosstalk between the epiblast and the trophoblast is critical in supporting the early stages of
conceptus development. FGF4 and BMP4 are inductive signals that participate in the communication
between the epiblast and the extraembryonic ectoderm (ExE) of the developing mouse embryo.
Importantly, however, it is unknown whether a similar crosstalk operates in species that lack a
discernible ExE and develop a mammotypical embryonic disc (ED).