Galphaq and Galpha11 proteins mediate endothelin-1 signaling in neural crest-derived pharyngeal arch mesenchyme.

Endothelin-A (ET(A)) is a G-protein-coupled receptor expressed in the neural crest-derived mesenchyme of the pharyngeal arches during craniofacial development. Targeted deletion of the ET(A) receptor or its ligand endothelin-1 (ET-1) causes cleft palate and hypoplasia of the mandible, otic cup, and tympanic ring. Previously we showed that Galpha(q)/Galpha(11)-null mice die around E11.0, whereas Galpha(q)((-/-))Galpha(11)((+/-)) mice survive to birth with hypomorphic phenotypes similar to, but less severe than, ET(A) or ET-1-null mice. To determine whether ET-1 signaling is transduced by Galpha(q)/Galpha(11) proteins, we examined the expression patterns of several ET-1 dependent and independent transcription factors in Galpha(q)/Galpha(11)-deficient embryos. Expression of genes encoding the ET-1-dependent transcription factors Dlx3, Dlx6, dHAND, and eHAND was specifically downregulated in the pharyngeal arches of Galpha(q)/Galpha(11)-deficient mice. In contrast, pharyngeal arch expression of the homeobox gene Msx1, which is not regulated by ET-1 signaling, was maintained in these embryos. We conclude that the Galpha(q) and Galpha(11) proteins serve as the intracellular mediators of ET-1 signaling in the pharyngeal arch mesenchyme.