Distribution of the genetic regulatory protein, Smad4, in a mouse embryo at 8.5 days gestation. The green stain in the center is Smad4 expressed in the liver and pancreas progenitor cells. The green on the periphery is Smad4 in the extraembryonic yolk sac tissue.
Credit: Ken Zaret, PhD; Ewa Wandzioch, PhD, University of Pennsylvania School of Medicine
Download high-resolution version.