Expression of TGF-beta isoforms during first trimester human embryogenesis.

We have studied the expression of the genes encoding transforming growth factors (TGFs) beta 1, beta 2 and beta 3 in human embryos ranging from 32 to 57 days post-coitum, using in situ hybridization. The spatial and temporal pattern of expression of each gene is distinct, though each occasionally overlaps. TGF-beta 1 is expressed in haematopoietic, endothelial and osteogenic tissues. TGF-beta 2 and TGF-beta 3 are expressed in a wide variety of mesenchymal tissues including areas of chondrogenic activity. TGF-beta 2 is also found in several epithelial and in the ventral nervous system. The differential transcript distributions are broadly similar to those seen in mouse embryos suggesting that there is conservation of TGF-beta gene regulatory sequences and developmental function across this species boundary.