A differentiation program induced by bone morphogenetic proteins 4 and 7 in endodermal epithelial cells provides the molecular basis for efficient nutrient transport by the chicken yolk sac.

This paracrine signaling cascade may constitute the basis for the EEC-mediated mechanism underlying the efficient uptake, degradation, resynthesis, and transfer of yolk-derived nutrients into the embryonic circulation, which assures proper energy supply and development of the growing fetus.