- Functional characterization of transforming growth factor beta signaling in Smad2- and Smad3-deficient fibroblasts. Piek, E., Ju, W.J., Heyer, J., Escalante-Alcalde, D., Stewart, C.L., Weinstein, M., Deng, C., Kucherlapati, R., Bottinger, E.P., Roberts, A.B. J. Biol. Chem. (2001)