Epithelial stem cell marker p63 expression during postnatal mouse molar EO development. (A) Secretory stage 3-day postnatal mouse molar EO, including stratum intermedium (si) and ameloblast (amel) cell layers and the enamel mineral layer (en). The arrow points to p63-positive stratum intermedium cell nuclei. (B) EO at 9 days postnatal. Arrows point to p63 labels in the stratum intermedium (si) and ameloblast (am) cell layers. (C, D) Twelve-day postnatal EO. The arrows point to p63-labeled nuclei in the ameloblast cell layer (am), stellate reticulum (sr), and stratum basale of the oral epithelium (oe). (E) Root tip and adjacent periodontal tissue of an 18-day postnatal first mouse molar tooth root. Root dentin (de), periodontal ligament (pdl), and Hertwig's epithelial root sheath (hers) are labeled. The arrows point to p63-positive nuclei present in HERS cells. EO, enamel organ.