Ece1 and Tbx1 define distinct pathways to aortic arch morphogenesis

Pharyngeal arch artery (PAA) remodeling defects account for several cases of congenital heart disease. Mutations in the Endothelin-1 genetic pathway or Tbx1, a candidate gene for DiGeorge syndrome, cause similar aortic arch defects. Previous research suggests that Tbx1 may trigger diffusible signals from the pharyngeal arches to support the growth of the PAAs that contribute to the mature aortic arch. The demonstration of genetic interaction between Tbx1 and Fgf8 pointed to FGF signaling as a possible candidate. Because Fgf8 interacts with Endothelin-1 signaling and because Endothelin-1 signaling interacts with neural crest-derived cells in the pharyngeal apparatus, we hypothesized that Tbx1 and Endothelin-1 signaling may contribute to the same pathway required for aortic arch morphogenesis. Therefore, we have analyzed mice mutated for the endothelin converting enzyme (Ece1) or Tbx1 genes and compound mutants. Results show that the two genes have different roles in the remodeling of the PAAs and do not interact. We propose that Tbx1 is required for the formation and early growth and remodeling of the PAAs, whereas Ece1 is necessary for regression of the cranial arch arteries and growth of the most caudal arch arteries. The latter function is likely related to the known role of the Endothelin-1 pathway in neural crest function. Developmental Dynamics 228.95-104, 2003. (C) 2003 Wiley-Liss, Inc.