Figure 4.

(a) Expression pattern of signaling molecules and transcription factors that regulate the formation and maintenance of the cervical loops. (b) The regulatory network for incisor stem cells. Key cellular processes (red), including stem cell maintenance, proliferation and differentiation, are regulated by an intricate network of signaling molecules and transcription factors, which either promote (as indicated by→) or inhibit (as indicated by —|) the downstream events, and ultimately maintain the homeostasis of the stem cell niche.