Patterning of the face and skull involves coordinated signaling between the epithelial cells and skeletal-forming mesenchymal cells of the pharyngeal arches. Defects in epithelial-mesenchymal signaling within human arches result in a variety of birth defects, including facial deformities and cleft palate. Whereas major advances have been made in identifying the signaling pathways involved in facial development, how these pathways are integrated to generate precise patterns of skeleton in the head remains poorly understood. The long-term goal of this proposal is to understand the logic by which arch mesenchymal cells interpret diverse signals in their environment to develop into precisely shaped cartilages and bones. In the first round of funding, zebrafish genetics was used to identify a novel role for Jag1 Notch signaling in patterning the skeleton of the upper face. Mutations in Jag1 result in facial defects not only in zebrafish but also in humans with Alagille Syndrome, and hence these investigations have had direct implications for understanding how craniofacial development goes awry in this birth defect. It is currently thought that Notch signaling only goes in one direction, from the Jag1 ligand to the Notch receptor. In this renewal proposal, new data suggest that signaling may go in the other direction in the face, with Notch activating Jag1. As such, the genetic experiments proposed here may lead to a dramatic re-interpretation of the origins of facial and other organ defects in Alagille Syndrome. Moreover, as Notch signaling is widely utilized, the findings made here will have much broader implications for understanding how this pathway functions during animal development. A number of related Fox transcription factors are found in the precursor cells to the facial skeleton, with mutations in Foxc1 resulting in the craniofacial defects of Axenfeld-Rieger Syndrome. Whether other members of the Fox family also play specific roles in patterning the face remains unknown. In addition to Foxc1, our preliminary zebrafish studies suggest that Foxd2 and Foxf1 also have very specific roles in facial patterning. In this proposal, we use some of the most advanced genetic tools available in zebrafish to test a model in which Fox genes translate complex signals (such as Jag1-Notch) into the discrete shapes and positions of individual skeletal elements. Zebrafish is ideally suited for these studies as Fox expression is remarkably well conserved between mammals and fish, and powerful genetic and embryological tools in zebrafish allow us to dissect the precise roles of multiple Fox genes in regulating skeletogenesis. The completion of these Aims will inform how changes in bone and cartilage differentiation underlie the facial defects of Axenfeld-Rieger Syndrome.

Public Health Relevance

Mutations in Jag1 and Foxc1 result in the craniofacial defects of Alagille and Axenfeld-Rieger Syndromes, respectively, yet how these genes control normal facial development remains poorly understood. The proposed studies will test a model in which Foxc1 forms part of a larger family of Fox genes that act downstream of Jag1 and other signals to pattern specific bones and cartilages in the face. The completion of these studies will provide important insights into how craniofacial development goes awry in Alagille and Axenfeld-Rieger Syndromes and how the shapes of individual facial bones vary between people and species.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE018405-07
Application #
8658423
Study Section
Special Emphasis Panel (ZRG1-MOSS-F (02))
Program Officer
Scholnick, Steven
Project Start
2007-09-01
Project End
2018-03-31
Budget Start
2014-04-01
Budget End
2015-03-31
Support Year
7
Fiscal Year
2014
Total Cost
$411,042
Indirect Cost
$161,042
Name
University of Southern California
Department
Other Basic Sciences
Type
Schools of Medicine
DUNS #
072933393
City
Los Angeles
State
CA
Country
United States
Zip Code
90089
Balczerski, Bartosz; Matsutani, Megan; Castillo, Pablo et al. (2012) Analysis of sphingosine-1-phosphate signaling mutants reveals endodermal requirements for the growth but not dorsoventral patterning of jaw skeletal precursors. Dev Biol 362:230-41
Zuniga, Elizabeth; Rippen, Marie; Alexander, Courtney et al. (2011) Gremlin 2 regulates distinct roles of BMP and Endothelin 1 signaling in dorsoventral patterning of the facial skeleton. Development 138:5147-56
Alexander, Courtney; Zuniga, Elizabeth; Blitz, Ira L et al. (2011) Combinatorial roles for BMPs and Endothelin 1 in patterning the dorsal-ventral axis of the craniofacial skeleton. Development 138:5135-46
Zuniga, Elizabeth; Stellabotte, Frank; Crump, J Gage (2010) Jagged-Notch signaling ensures dorsal skeletal identity in the vertebrate face. Development 137:1843-52