Twist1 Acts Upstream of the Dlx5-Hand2 Pathway to Pattern the Mammalian Jaw

Both the upper and lower jaws develop from cranial neural crest cells (CNCCs) populating the first pharyngeal arch in all gnathostomes. Previous studies showed that the Edn1/Ednra-Dlx5/Dlx6-Hand2 signaling pathway is necessary for lower jaw formation and that ectopic expression of Edn1 or Hand2 throughout the CNCCs partly transformed the upper jaw to lower jaw structures, but the molecular mechanisms regulating upper jaw development remain unclear. Here we show that the basic helix-loop-helix...