- Mutations of ephrin-B1 (EFNB1), a marker of tissue boundary formation, cause craniofrontonasal syndrome. Twigg, S.R., Kan, R., Babbs, C., Bochukova, E.G., Robertson, S.P., Wall, S.A., Morriss-Kay, G.M., Wilkie, A.O. Proc. Natl. Acad. Sci. U.S.A. (2004)