REGULATION OF DIFFERENTIATION BY TGF-BETA

Recent experiments in neural, skeletal, endothelial, and hematopoietic tissues have provided new insights into the way members of the transf orming growth factor-beta (TGF-beta) superfamily regulate cellular dif ferentiation, TGF-beta s regulate the fate of multipotential stem cell s instructively (in the neural crest) by regulating the expression or function of tissue-specific transcription factors, as well as selectiv ely On the mesenchyme) by regulating the expression of required growth factors and their receptors. During skeletal development, TGF-beta s have unique functions and act sequentially to modulate chondrocyte and osteoblast differentiation. Responsiveness to TGF-beta s changes as c ells differentiate and evidence now suggests that changes in TGF-beta receptor profile may account for some of these differences. Drosophila and transgenic mouse models are now providing useful insights into me chanisms of TGF-beta action in vivo.