Defective and damaged teeth are a common public health problem affecting the majority of human being throughout their lifespan. Tooth bioengineering and regeneration can have a premise future to tackle this health issue. A thorough understanding of molecular and cellular processes that regulate tooth stem cell self-renewal and differentiation is crucial to build new teeth. Currently, significant progresses have been made in tooth mesenchymal stem cells research. Yet, odontogenic epithelial stem cells (OESCs) are understudied and no suitable in vitro culture system is available for expansion and analyses of OESCs. The fibroblast growth factor (FGF) signaling axis has been shown plays important roles in development and survival of the cervical loop, a stem cell niche that supports the lifelong growth of mouse incisors. In this project, we will use the newly developed in vitro culture systems for OESCs and the genetically engineered mouse models to study the mechanisms that underlie regulation of survival, self- renewal, and differentiation of OESCs by the FGF signaling axis. We will first optimize the OESC sphere culture conditions, and study how to induce OESC lineage commitment and differentiation by manipulation of the FGF signaling axis. Next, we will develop methods for enriching OESCs and for lineage tracing of OESC progeny. We will then determine whether the FGF signaling axis is required for the survival, self-renewal, and differentiation of OESCs. These studies will advance our understanding of how self-renewal, expansion, and differentiation are regulated in general; the findings will likely benefit a large number of men and women with defective or damaged teeth, and will guide future efforts aimed at stem cell-based tooth bioengineering. The project is highly innovative since it is the first to understand how survival, self-renewal, and differentiation of OESC are regulated. Novel genetically engineered mouse models and novel OESC culture systems will be developed, which, together with currently available ones, will also benefit the tooth research community.