Fig. 5. Edar and Ccn2 colocalize during early hair and tooth development. Whole-mount in situ hybridization with a probe specific to Ccn2 (A-G,H,K,M) and Edar (I,J,L). (A-C') Ccn2 is expressed in primary hair placodes of wild-type embryos at E14, and is often concentrated at the circumference of the placode (arrowheads in C). (D) No localized expression of Ccn2 is detected in Eda-null skin at E14. (E-G) Recombinant Eda-A1-induced localized upregulation of Ccn2 in Eda^-/- E13 skin explants cultured for 24 hours. (H,I) Vibratome section of whole mounts confirmed the colocalization of Edar and Ccn2 in primary hair placodes of E14 wild-type embryos. (J,K) Edar and Ccn2 are coexpressed also in wild-type molar (arrow) and incisor (arrowhead) placodes at E12. (L,M) In contrast to primary hair placodes, expression of Ccn2 is unaffected in Eda-deficient tooth placodes. Mc, Meckel's cartilage. Scale bar: 1 mm in A; 0.5 mm in B-D,J-M; 50 µm in H,I.