Project Summary/Abstract In the U.S., more than 10% of infants are born with dental anomalies, including tooth agenesis, malformation, and enamel dysplasia (ED). The study of tooth development is critical for understanding these congenital disorders and developing novel therapies and treatments, and thus has implications for oral health. However, the transcriptional and epigenetic mechanisms that control tooth development is not well understood. The long- term goal is to identify and characterize the transcription factors that function as important regulators of tooth development in health and disease. The objective of this proposal is to understand the transcriptional and epigenetic regulatory mechanisms underlying tooth enamel development and to address why loss-of-function mutations of the p63 gene cause tooth anomalies, including ED. p63 is a master transcription factor of ectodermal development and homeostasis, as evidenced by ectodermal dysplasia in individuals with p63 mutations, often involving ED and other dental anomalies. However, the role of ΔNp63, the major isoform of p63, and the mechanisms by which ΔNp63 regulates the chromatin and transcriptional regulatory environment in tooth development is completely unknown due to lack of targeted genetic systems. In response to this need, a well- defined ΔNp63 knockout mouse model was generated to perform robust, inducible deletion of ΔNp63 in the developing enamel organ. Based on preliminary data and re-analysis of published work by others, it is hypothesized that p63 functions as a major regulator of tooth enamel development by comprehensively activating its target genes, which are essential for driving earlier cell fate specification and later cell differentiation events in the enamel organ cells. Using genomics and epigenomics approaches and a newly developed mouse model of ED in ectodermal dysplasia, in which ΔNp63 knockout is induced during tooth development, three important questions will be addressed. Aim 1 will define the developmental mechanisms that require p63 action during tooth development. Aim 2 willdefine the molecular mechanisms by which p63 directs tooth development. Finally, Aim 3 will identify the cell-state transition dynamics and the underlying epigenetic mechanism governed by ΔNp63 in tooth development. Collectively, these experiments will define the fundamental mechanisms that govern tooth enamel development on a broad and dynamic scale, which will provide foundational information essential for developing better ways to diagnose, treat, and prevent congenital and acquired dental disorders.

Project Narrative Despite the wealth of biological knowledge about how teeth are formed, the underlying molecular mechanisms of tooth development remain poorly understood. This research will identify the gene regulation programs of tooth enamel development and address the question of why certain genetic mutations result in congenital dental enamel anomalies. Understanding the gene regulation programs of tooth enamel development is important for the development of better strategies for the diagnosis, prevention, and treatment of congenital and acquired dental disorders.