phospholipase C, beta 3 is required for Endothelin1 regulation of pharyngeal arch patterning in zebrafish

Genetic and pharmacological studies demonstrate that Endothelin 1 (Edn 1) is a key signaling molecule for patterning the facial skeleton in fish, chicks, and mice. When Edn I function is reduced early in development the ventral lower jaw and supporting structures are reduced in size and often fused to their dorsal upper jaw counterparts. We show that schmerle (she) encodes a zebrafish ortholog of Phospholipase C, beta 3 (Plc beta 3) required in cranial neural crest cells for Edn1 regulation of pharyngeal arch patterning. Sequencing and co-segregation demonstrates that two independent she (plc beta 3) alleles have missense mutations in conserved residues within the catalytic domains of Plc beta 3. Homozygous plc beta 3 mutants are phenotypically similar to edn1 mutants and exhibit a strong arch expression defect in Edn1-dependent Distalless (Dlx) genes as well as expression defects in several Edn1-dependent intermediate and ventral arch domain transcription factors. p1c beta 3 also genetically interacts with edn1, supporting a model in which Edn1 signals through a G protein-coupled receptor to activate Plc beta 3. Mild skeletal defects occur in plc beta 3 heterozygotes, showing the plc beta 3 mutations are partially dominant. Through a morpholino-mediated deletion in the N-terminal PH domain of Plc beta 3, we observe a partial rescue of facial skeletal defects in homozygous plc beta 3 mutants, supporting a hypothesis that an intact PH domain is necessary for the partial dominance we observe. In addition, through mosaic analyses, we show that wild-type neural crest cells can efficiently rescue facial skeletal defects in homozygous plc beta 3 mutants, demonstrating that Plc beta 3 function is required in neural crest cells and not other cell types to pattern the facial skeleton. (c) 2006 Elsevier Inc. All rights reserved.