# Transforming Growth Factor-<latex>$\beta$</latex>: Multifunctional Regulator of Differentiation and Development

A. B. Roberts, K. C. Flanders, U. I. Heine, S. Jakowlew, P. Kondaiah, S.-J. Kim, M. B. Sporn

## Abstract

Transforming growth factors-<latex>$\beta$</latex> (TGF-<latex>$\beta$</latex>) are 25 kilodalton (kDa) homodimeric peptides with multifunctional actions controlling the growth, differentiation and function of a broad range of target cells of both epithelial and mesenchymal derivation. They are expressed early in embryogenesis and their tissue-specific and developmentally dependent expression is strongly suggestive of an essential role in particular morphogenetic and histogenetic events. Five distinct TGF-<latex>$\beta$</latex>s have been characterized so far, with 65-80% homology to each other. By using both molecular biological and immunohistochemical techniques, we are currently attempting to define specific sites of expression of the different TGF-<latex>$\beta$</latex>s and to determine whether TGF-<latex>$\beta$</latex>s 1-5 might have unique functions in development and in the mature organism. Comparative study of the promoter regions for the different TGF-<latex>$\beta$</latex>s and for any particular TGF-<latex>$\beta$</latex> in different species is also underway. Mechanistically, TGF-<latex>$\beta$</latex>s act to control gene expression of their target cells, many of their actions converging on a complex, multifaceted scheme of control of matrix proteins and their interactions with cells; these effects on matrix are thought to mediate many of the effects of TGF-<latex>$\beta$</latex> on development.