Activin signal transduction pathways.

Many of the signal transduction pathways required for mammalian endocrine cell function are conserved from flies and worms. These model organisms permitted the illumination of the biological properties of ligands and provided systems in which cellular coactivating molecules could be identified rapidly. Our knowledge about the activin signaling components has been advanced tremendously by the work carried out in these systems. Subsequent research is beginning to reveal the complex interactions that serve to regulate this signaling pathway.