In keeping with the mission of NIDCR to improve oral, dental and craniofacial health, this proposal focuses on the developmental genetic basis of patterning of the facial skeleton. It utilizes zebrafish as a model system. The model has many positive attributes for study of the detailed nature of how embryonic cells build and shape a set of interconnected skeletal elements, and for learning about the genes that guide these cellular activities. Zebrafish broadly share basic patterning mechanisms of jaw and skull formation with other vertebrates, including humans. Furthermore, there are increasing numbers of examples known where mutations in the very same genes of humans, mouse, and zebrafish produce head skeletal malformations that are similar in detail. Hence, zebrafish can teach us much about the nature of the defects in inherited craniofacial disorders such as cleft palate. Three projects are proposed to test specific predictions of hypotheses explaining critical aspects of early skeletal patterning, and to discover new craniofacial regulatory genes. The first investigation is to examine function of a genetic pathway that is activated in the embryonic pharyngeal arches by an upstream signaling molecule, Endothelin1, critical for jaw patterning in zebrafish and mouse alike. With even mild disruption of this pathway the joint between the upper and lower jaw is lost, replaced with cartilage in a way that seems to mimic early stages of severe osteoarthritis. The experiments examine specific roles of Endothelin1 target genes that normally regulate repression of cartilage development where the joint arises. All of the zebrafish craniofacial studies carried out so far have been limited to the first few days of skeletal development, and the second and third projects will expand our knowledge to include many more days, to the juvenile-adult stage. The second project utilizes confocal time-lapse recording of development of fluorescently labeled bone and bone-forming cells in living, intact fish larvae. It will explore the nature of the dynamic cellular reorganizations that appear to underlie formation of new bone morphologies. The third investigation is to use a skeletal mutant screen at the juvenile-adult stage to discover new craniofacial genes. The highest priority is to find genes that function to expand upon the early skeletal scaffold that forms in the embryo. Analyses of the mutants recovered in this screen will reveal how the genes work.
Our project will provide basic understanding of genetic and cellular mechanisms regulating morphogenesis of the craniofacial skeleton. We will investigate cellular behaviors that shape dermal bones, and we will identify and characterize new craniofacial genes, informing us of the potential disturbances underlying inherited human disorders such as in DeGeorge and Frasier syndromes.
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|Kimmel, Charles B (2014) Skull developmental modularity: a view from a single bone - or two. J Appl Ichthyol 30:600-607|
|Eames, B Frank; DeLaurier, April; Ullmann, Bonnie et al. (2013) FishFace: interactive atlas of zebrafish craniofacial development at cellular resolution. BMC Dev Biol 13:23|
|Sasaki, Mark M; Nichols, James T; Kimmel, Charles B (2013) edn1 and hand2 interact in early regulation of pharyngeal arch outgrowth during zebrafish development. PLoS One 8:e67522|
|MacDonald, Ryan B; Pollack, Jacob N; Debiais-Thibaud, Melanie et al. (2013) The ascl1a and dlx genes have a regulatory role in the development of GABAergic interneurons in the zebrafish diencephalon. Dev Biol 381:276-85|
|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|
|Eames, B Frank; Yan, Yi-Lin; Swartz, Mary E et al. (2011) Mutations in fam20b and xylt1 reveal that cartilage matrix controls timing of endochondral ossification by inhibiting chondrocyte maturation. PLoS Genet 7:e1002246|
|Zuniga, Elizabeth; Stellabotte, Frank; Crump, J Gage (2010) Jagged-Notch signaling ensures dorsal skeletal identity in the vertebrate face. Development 137:1843-52|
|Kimmel, Charles B; DeLaurier, April; Ullmann, Bonnie et al. (2010) Modes of developmental outgrowth and shaping of a craniofacial bone in zebrafish. PLoS One 5:e9475|
|Talbot, Jared Coffin; Johnson, Stephen L; Kimmel, Charles B (2010) hand2 and Dlx genes specify dorsal, intermediate and ventral domains within zebrafish pharyngeal arches. Development 137:2507-17|
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