Fig. 2. Expression of TAp63 and Np63 transcripts, and of p63 protein. (A-C) No TAp63 mRNA was seen in surface ectoderm or tooth germ epithelia at the initiation (E11), placode (E12) or cap stages of molar tooth development (E14). (D-G) Intense expression of Np63 was seen in the oral and dental epithelium, as well as in hair follicles, in similar patterns to those observed with the p63 probe that detects all isoforms (see also Fig. 1). (H) Expression of the TAp63 isoform was not detected in the epithelia of the newborn (NB) mouse. (I) In P2 incisors, Np63 expression was intense in the enamel organ epithelium contacting the ameloblasts, but ameloblasts did not express Np63. (J) Immunohistochemical analysis showed p63 protein expression throughout the oral and dental epithelia at E11. (K) Expression was particularly intense in the outer enamel epithelium in the molar at bell stage. (L) In the P1 incisor, p63 protein expression was most intense in the outer enamel epithelium. (M) Western blot analysis of p63 isoforms in E13 and E14 skin samples of p63^-/- and wild-type (combined +/- and +/+) embryos. NIH3T3 cells transfected with Np63, Np63ß or Np63 were used as control samples. The major band detected in wild-type tissues corresponds to Np63; TAp63 typically migrates substantially more slowly in SDS-PAGE. (N) Quantification of the expression of Np63 and TAp63 isoforms in E7 and E8 whole embryos, and in E9 and E13 skin by real-time PCR. Trace amounts of the TAp63 isoform were detected at E13. A, ameloblasts; cl, cervical loop; oee, outer enamel epithelium; n.d., not detectable.