Generation of Smad3-null Mice and Smad4-conditional Mice
SMADs are a novel set of mammalian proteins that act downstream of TGF-beta family ligands. These proteins can be categorized into three distinct functional sets, receptor-activated SMADs (SMADs 1,2,3,5, and 8), the common mediator SMAD (SMAD 4), and inhibitory SMADs (SMADs 6 and 7). SMAD proteins are thought to play a role in vertebrate development and tumorigenesis.