- DAN is a secreted glycoprotein related to Xenopus cerberus. Stanley, E., Biben, C., Kotecha, S., Fabri, L., Tajbakhsh, S., Wang, C.C., Hatzistavrou, T., Roberts, B., Drinkwater, C., Lah, M., Buckingham, M., Hilton, D., Nash, A., Mohun, T., Harvey, R.P. Mech. Dev. (1998)