(D) EMSA of Pitx2 protein with IRDye-labeled oligonucleotides from the promoter

(D) EMSA of Pitx2 protein with IRDye-labeled oligonucleotides from the promoter. and teeth, indicating that it contributes to the development of these organs (Amendt et al., 1998; Semina et al., 1996). Mice with a general knockout are embryonic lethal with defects Losartan in the heart, lung, body wall and teeth, further demonstrating that plays an essential role in controlling organogenesis during development (Lin et al., 1999). In the case of teeth, the general knockout of leads to an arrest in development at the bud stage, involving downregulation of fibroblast growth factor 8 (controls early odontogenesis are unknown. However, using transgenic mice overexpressing a repressor of Pitx2, we have demonstrated that plays a role in dental epithelial cell differentiation into ameloblasts (Cao et al., 2013; Li et al., 2013). Although has long been considered as a master regulator of the transcriptional hierarchy in early tooth development, including stem cells (Pispa and Thesleff, 2003; Tucker and Sharpe, 2004), its specific role in cell differentiation and signaling has not been investigated due to embryonic lethality of Losartan global knockout mice. Therefore, we investigated the specific role of using a conditional knockout approach. During embryonic development, stem-cell specification, and the proliferation and differentiation of transit-amplifying cells (TAs), which are a population in transition between stem cells and differentiated cells, are keys to organogenesis (Hsu et al., 2014). Organs such as teeth, hair follicles and mammary glands are derived from surface ectodermal cells via processes coordinated by interactions between the epithelium and Losartan mesenchyme (Jimnez-Rojo et al., 2012). As soon as the epithelial ectoderm receives signals from adjacent mesenchyme within a determined region, it forms a placode or a localized thickening of epithelial cells (Fig.?1B). Teeth develop from two epithelial cell populations within the dental placode: Sox2+ cells and Lef1+ cells (Sanz-Navarro et al., 2018; Sun et al., 2016) (Fig.?1B). The Sox2+ cells are the progenitors of various epithelial cell types that form bud- and cap-stage teeth, and the Lef1+ cells that are present during the placode, bud and cap stages produce growth factors that control tooth morphology. Ablation of in the developing tooth leads to impaired proliferation of dental epithelial stem cells (DESCs) during the early stages of tooth development and prevents the renewal of DESCs in the adult (Sanz-Navarro et al., 2018; Sun et al., 2016). The ablation of in the dental epithelium also leads to severe developmental defects of the teeth, causing an arrest during the transition from bud to cap stage (Sasaki et al., 2005; van Genderen et al., 1994). We have recently shown that conditional overexpression of in the dental epithelium results in a new stem cell compartment and lack of dental epithelial cell differentiation (Sun et al., 2016). Furthermore, regulates and expression in the epithelium. Open in a separate window Fig. 1. Dental development is delayed at bud stage Itgam and disrupted at the cap stage in embryos. (A) Representative images of weaning-age mice, showing the gum (black arrow) but an absence of teeth in mice. (B) Murine lower incisor development and location of the two signaling centers (IK, initiation knot; EK, enamel knot). (C) Representative Hematoxylin and Eosin images of bud- (E12.5), cap- (E14.5) and bell- (E16.5) stage lower incisor morphogenesis. Development of the lower incisors of embryos is delayed with respect to invagination of the dental epithelium (DE, blue arrows) and vestibular lamina (VL, black arrows, E12.5 and E14.5). No typical lower incisors were found in E14.5 and E16.5 embryos. DE, dental epithelium; LaCL, labial cervical loop; DESC, dental epithelial stem cell; VL, vestibular lamina; Md, mandible; Mx, maxillary; LI, lower incisor; UI, upper incisor; OE, oral epithelium; Tg, tongue. Tooth morphogenesis is stimulated by growth factors Fgf, Wnt, Shh and Bmp, which are produced by a cluster of cells known as the dental epithelial signaling center and by adjacent dental mesenchyme (Balic and Thesleff, 2015). Effective function of the epithelial signaling centers is crucial for tooth morphogenesis. There are two signaling centers, the initiation knot (IK), and enamel knot (EK), and the size of the IK signaling center correlates with that of the entire tooth at each stage (Ahtiainen et al., 2016) (Fig.?1B). Specifically, an epithelial signaling center at the cap stage (E13.5), the EK, is crucial for tooth morphogenesis during this stage. The EK is derived from the cells toward the posterior region of the tooth bud; it is not derived from the IK.