Ectodermal-derived Endothelin1 is required for patterning the distal and intermediate domains of the mouse mandibular arch

► The source of endothelin-1 (Edn1) during pharyngeal arch morphogenesis is examined. ► Only loss of Edn1 from the ectoderm leads to defects in facial development. ► Conditional gene deletion of Edn1 allowed visualization of the intermediate domain. ► Intermediate arch gene expression was most sensitive to loss of Edn1. ► Loss of intermediate arch gene expression correlated with proximal jaw defects.