Fig1D(wt). Copyright: Reprinted with permission from Elsevier from [doi:10.1006/dbio.1999.9527] Dev Biol 217: 10-24, Clouthier DE; Williams SC; Yanagisawa H; Wieduwilt M; Richardson JA; Yanagisawa M, Signaling pathways crucial for craniofacial development revealed by endothelin-A receptor-deficient mice. Copyright 2000