Transforming growth factor-betas (TGF-Bs) mediate many cell-cell interactions that occur during embryonic development. Three TGFBs have been identified in mammals. TGF-Beta 1，TGF-Beta 2 and TGF-Beta 3 are each synthesized as precursor proteins that are very similar in that each is cleaved to yield a 112 amino acid polypeptide that remains associated with the latent portion of the molecule. TGF-beta 1 is involved in hematopoiesis and endothelial differentiation.
