Figure 6. αE-catenin regulates enamel knot formation and tooth germ invagination by controlling YAP/TAZ activity during tooth development.

(a,b) H&E staining of E13.5 tooth germ shows that double deletion of Yap/Taz in the Ctnna1^cKO dental epithelium is able to rescue the invagination defect seen in Ctnna1^cKO. (c) Quantification of the depth of invaginated tooth germ in control, triple knockouts and Ctnna1^cKO at E13.5 (mean±s.e.m., n=3, P<0.01). (d–g) Deletion of Yap/Taz in Ctnna1^cKO restores the non-proliferating zone at the posterior region of the tooth germ, as assessed by Ki67 staining, indicating the formation of the EK (open yellow arrowheads). (h–k) p21 staining confirms that deletion of Yap/Taz in Ctnna1^cKO reestablishes a non-proliferating zone, indicating the formation of the EK in the tooth germ (yellow arrowheads). (l) Quantification of the number of p21-positive cells per section in control and triple knockout tooth germs (mean±s.e.m., n=3, P>0.05). (m,n) Shh expression at the posterior region of the tooth germ epithelium is rescued on Yap/Taz deletion in the Ctnna1^cKO (dark arrowheads). (o,p) Expression of the mesenchymal gene, Msx1, is rescued in the dental mesenchyme at E13.5 after deletion of Yap/Taz in Ctnna1^cKO in the tooth germ. All quantifications are analysed by using Student's t-test. *P<0.05, **P<0.01. Dotted lines outline the epithelium of the incisor tooth germ. Scale bar, 100 μm (a,b); 50 μm (d,f,h,j,m–p); 8 μm (e,g,i,k).