The cranial neural crest (NC) contributes to the formation of many craniofacial structures including the bones and cartilage of the face, tooth dentin and peripheral ganglia. Cell signaling regulates different aspects of cranial NC specification, epithelial-to-mesenchymal transition (EMT) and differentiation and disruptions in this developmental program results in many cranial NC-derived craniofacial birth defects including craniosynestosis, Treacher Collins and CHARGE syndromes, and cleft palate. BMP signaling plays a crucial role during the specification and differentiation of cranial NC, and more recently, BMP signaling was shown to control cranial NC EMT. A mechanistic understanding of the role of BMP signaling during cranial NC development is essential to develop novel preventative and therapeutic measures against craniofacial defects. This proposal will determine the molecular mechanism of BMP gradient formation in the chick gastrula, and how this gradient regulates the formation of cranial cell types including neural, cranial NC, placode and epidermal fates. These experiments will use in vivo and in silico approaches to test the hypothesis that extracellular BMP ligands are produced primarily by the cranial NC and are actively shuttled over long distances to signal most strongly in the nonneural ectoderm. Next, quantitative expression analysis and live imaging will be used to establish the timeline of BMP signaling during gastrulation and neurulation, and analysis of the resulting datasets will determine population- and single-cell-level responses to BMP signals. Differences in signal timing and strength will then be correlated with direct input into different target genes. Finally, the role of BMP target genes Id1/2/3/4 and Fibin during cranial NC EMT will be investigated using in vivo functional analyses. Together, the results of these aims will provide a comprehensive understanding of the regulation and roles of BMP signaling events during early cranial NC development. In addition to identifying targets for translational avenues to prevent craniofacial birth defects, the mentored phase of this proposal will provide Dr. Michael Piacentino with necessary training as he prepares to begin his independent career. Dr. Marianne Bronner's lab at California Institute of Technology, and his assembled advisory council, provide the necessary tools, expertise, and training environment to efficiently execute the proposed aims and establish Dr. Piacentino's independence. This training will be instrumental as Dr. Piacentino begins his independent research program and will provide the experience needed to make lasting impacts on the field of BMP signaling during craniofacial development.
PUBLIC HEALTH RELEVANCE Cranial neural crest cells are essential for the formation of diverse craniofacial structures including bones and cartilage as well as portions of cranial ganglia; as such, defects in cranial neural crest specification, epithelial- to-mesenchymal transition, and differentiation are root to many craniofacial birth defects including craniosynestosis, Treacher Collins and CHARGE syndromes. This project will identify the mechanisms that control BMP signaling during its essential roles in cranial neural crest specification and will determine the molecular function of BMP signaling during cranial neural crest epithelial-to-mesenchymal transition. The results will provide significant and novel avenues for translational approaches to prevent and treat neural crest-derived craniofacial birth defects.