Root-forming mesenchymal progenitors express Osterix. (A) P4 mandibular first molar (M1) of Osx-creER; R26RtdTomato/+ is shown. Tomato+ odontoblasts were observed beneath enamel (yellow arrowheads). (B) High magnification of rectangle area. DP, dental papilla; DF, dental follicle. P11 mandibular first molar (M1) section of Osx-creER; R26RtdTomato/+ (C) and high magnification of rectangle area (D, E). P18 mandibular first molar (M1) section of Osx-creER; R26RtdTomato/+ (F) and high magnification of rectangle area (G, H). Scale bars represent 200 µm (upper panels), 50 µm (lower panels) and 20 µm ((E) panel)