This family includes TGF-β1, TGF-β2, TGF-β3, and TGF-β5. They are involved in positively and negatively regulation of cell division, the formation of the extracellular matrix between cells, apoptosis, and embryogenesis. They bind to TGF-β type II receptor (TGFBRII).
TGF-β1 stimulates the synthesis of collagen and fibronectin and inhibits the degradation of the extracellular matrix. Ultimately, it increases the production of extracellular matrix by epithelial cells.
TGF-β proteins regulate epithelia by controlling where and when they branch to form kidney, lung, and salivary gland ducts.