PROJECT SUMMARY
Dental and craniofacial abnormalities are some of the most common congenital conditions in the United States,
and tooth abnormalities occur in 3-4% of adults. For several dental and craniofacial disorders, mutations in
regulatory genes have been identified. For example, mutations in PITX2 and EDA are both associated with
missing or misshapen primary and adult teeth. Understanding how these genes are regulated and function in
normal and disease contexts is thus important to better understand how teeth form and regenerate. However,
because developing teeth are dynamic, heterogeneous tissues, and the initiation of and response to molecular
signals is often cell-type-specific, we currently lack a clear understanding of how Pitx2 and Eda are spatially
and temporally regulated during tooth initiation, and which gene network(s) they affect to promote tooth
placode proliferation. Therefore, the overall goal of this work is to determine the cell-type and tissue-specific
gene regulation and signaling networks that underlie tooth placode initiation and morphogenesis. This goal will
be achieved through the completion of several objectives in the threespine stickleback, a tractable fish model
for developmental biology that, like humans but unlike mice, has the ability to replace teeth. First, genomic
enhancers that regulate the expression of Pitx2 and Eda in developing teeth will be identified and analyzed to
improve our ability to predict enhancers from genomic sequence (Specific Aim 1). Next, the effects of Pitx2 and
Eda mutant alleles on early tooth germ cell proliferation and morphology will be quantified, both in initial and
replacement teeth (Specific Aim 2). Finally, the downstream transcriptional effects of Pitx2 and Eda mutant
alleles will be quantified using several complementary techniques, specifically in situ hybridization and cell
proliferation assays (Specific Aim 2). This work will directly test the hypothesis that Pitx2 and Eda regulate
dental epithelial cell proliferation of neighboring cells through distinct downstream targets. In addition to
improving our functional understanding of two important master regulator genes that cause human tooth
disorders, this work will provide training in traditional and cutting-edge developmental biology techniques in a
dynamic and supportive scientific environment. The acquisition of these skills, interactions within the local
scientific community, and training through courses at the research institute will facilitate the ability of the
applicant to conduct rigorous, independent research of the genetic and developmental basis of tooth formation.
