RESUMO
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.
Assuntos
Região Branquial/metabolismo , Endotelina-1/metabolismo , Proteínas Heterotriméricas de Ligação ao GTP/metabolismo , Crista Neural/metabolismo , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Região Branquial/embriologia , Proteínas de Ligação a DNA/genética , Subunidades alfa Gq-G11 de Proteínas de Ligação ao GTP , Regulação da Expressão Gênica no Desenvolvimento , Proteínas Heterotriméricas de Ligação ao GTP/deficiência , Proteínas Heterotriméricas de Ligação ao GTP/genética , Proteínas de Homeodomínio/genética , Hibridização In Situ , Fator de Transcrição MSX1 , Mesoderma/metabolismo , Camundongos , Camundongos Knockout , Modelos Biológicos , Crista Neural/embriologia , Fenótipo , Transdução de Sinais , Fatores de Transcrição/genética , Proteínas de Peixe-ZebraRESUMO
The regulators of G-protein signaling (RGS) proteins are important regulatory and structural components of G-protein coupled receptor complexes. RGS proteins are GTPase activating proteins (GAPs) of Gi-and Gq-class Galpha proteins, and thereby accelerate signaling kinetics and termination. Here, we mapped the chromosomal positions of all 21 Rgs genes in mouse, and determined human RGS gene structures using genomic sequence from partially assembled bacterial artificial chromosomes (BACs) and Celera fragments. In mice and humans, 18 of 21 RGS genes are either tandemly duplicated or tightly linked to genes encoding other components of G-protein signaling pathways, including Galpha, Ggamma, receptors (GPCR), and receptor kinases (GPRK). A phylogenetic tree revealed seven RGS gene subfamilies in the yeast and metazoan genomes that have been sequenced. We propose that similar systematic analyses of all multigene families from human and other mammalian genomes will help complete the assembly and annotation of the human genome sequence.
