The transforming growth factor β superfamily

The TGFβ superfamily encompasses a large group of growth and differentiation factors affecting a wide range of biological processes in both vertebrates and inver-tebrates. Although the various members of this family are all structurally related, they are quite divergent from TGFβ and from each other with respect to their amino acid sequences and the specific activities that they possess in vitro and in vivo. Like TGFβ, many of these factors are important in regulating cell differentiation processes during embryonic development and in maintaining tissue homeostasis in adult animals. Because these molecules are potent extracellular regulators of cell growth and differentiation, understanding their biology will be important for deciphering the complex regulatory network of cell-cell interactions that take place during develop-ment and for understanding how such regulatory mechanisms can go awry in the pathogenesis of human diseases and how the biological properties of these factors can be exploited for clinical applications.