EDNRA and mandibulofacial dysostosis with alopecia: Instead of a complete loss of EDNRA such as in Ednra-null mice, an impaired Ednra function due to a change in ligand binding affinity caused by the Tyr-129 substitution (Krystek et al. 1994; Lee et al. 1994) leads to the phenotype in EdnraY129F/+ and EdnraY129F/Y129F mice and patients with MFDA.