Fig. 1. Root development in mouse molar, mouse incisor and vole molar. (A) Differential gene expression of Fgf10 during the development of mouse incisors and molars and sibling vole molars. In mouse molar development, Fgf10 is expressed in the neighboring mesenchyme adjacent to the proliferating epithelium during crown morphogenesis, but disappears at the root formation stage. In the vole molar and the mouse incisor, Fgf10 is expressed continuously only in the mesenchyme of the crown analog, but not in that of the root analog. However, slight expression of Fgf10 is detectable around the tip of the lingual epithelium of mouse incisors. (B) Higher magnification of the boxed area in A during the root development of mouse molars. The broken red line indicates the border between the crown and root. (C) Higher magnification of the boxed area during root analog (lingual side) formation in mouse incisors. The histological features at the lingual side (C) mimic the root development of mouse molars (B). The HERS-like epithelial sheath and its fragmented epithelium, like Malassez epithelial rests, are visible at the apical end. Periodontal ligaments are formed between the fragmented epithelium. d, dentin; e, enamel.