- The high mobility group transcription factor Sox8 is a negative regulator of osteoblast differentiation. Schmidt, K., Schinke, T., Haberland, M., Priemel, M., Schilling, A.F., Mueldner, C., Rueger, J.M., Sock, E., Wegner, M., Amling, M. J. Cell Biol. (2005)