Growth and Transcription Factors in Tooth Development

Odontogenesis is a complex embryonic process originated by the interaction between two main embryonic components, dental epithelium and ectomesenchyme. This ectomesenchymal interaction is mediated by growth and transcription factors controlling the different aspects of tooth development such as tooth initiation, enamel knot formation and/or cell proliferation and differentiation. The aim of this review was to establish which factors are, how they interact and their functions in Odontogenesis. We have described several signaling pathways which are essential for correct tooth development and organized all available information. Our conclusion is that instead of large amount of information about tooth development, further studies are necessary to clear several essential mechanisms which still remain unknown and/or unclear. The earliest marker of tooth position is Pixt2 appears in the stomatodeal and is progressively restricted to dental placode determining the request of Pixt2 for early specification of odontogenic epithelium [6]. Pax9 is another early marker of tooth position and its function might be necessary for establishing the competence of future tooth mesenchyme to respond to epithelial signals [7]. The same study proposes an alternative explanation about Pax9 function during initial stage suggesting that it plays a more direct role in the regulation of signaling molecules’ production by the mesenchyme [7]. Wnt7b and Shh act as early markers of tooth position and are expressed in oral ectoderm and dental epithelium, respectively, interacting to keep cell boundaries between oral ectoderm and dental epithelium from E9.5 until E11.5 [8]. In Table 1 [9-13] we can see which factors are implicated in molar and/or incisor formation such as Lhx6 and Lhx7 which control the acquisition of odontogenic potential by molar mesenchyme [14,15], in response to epithelial FGF-8 [15], or Dlx1 and Dlx2 which specify a subpopulation of neural crest derived mesenchymal cells as odontogenic for the upper molar region [10]. In Figure 1 [9,12,16-18], it has been shown interaction between some factors which determine tooth type and position. Thickening of dental epithelium and mesenchymal condensation: Epithelial BMP-4 and FGF-8 are essential in control of target genes transcription at this stage. They interact, BMP-4 as inhibitor and FGF-8 as inducer, and lead to different responses (Figure 2) [7,16,19] controlling epithelial proliferation. Introduction The embryonic process of odontogenesis is originated by two main embryonic tissues which are ectoderm and the underlying ectomesenchyme. The interaction between both two components leads tooth development throughout different phases known as initial stage, bud stage, cap stage, bell stage, appositional stage and root development [1]. Signal molecules, growth and transcription factors among other factors, are responsible of this interaction between epithelium and ectomesenchyme, and the communication in a one tissue layer [1]. Nowadays there are several researches which show the expression and functions of these factors during tooth development, but it is necessary to collect and organize this information improving the quality of the future studies. Therefore the aim of this review has been the collection and organization of all information about these factors during Odontogenesis. Discussion Initial stage The first morphological signal of tooth development is the formation of a serie of epithelial thickenings into ectomesenchyme at sites corresponding to the position of presumptive teeth [2]. In mice the number of thickenings which appear is fewer than human. Mice has only one incisor, which is continuously growing throughout their live, and three molars separated by a diastema region in each quadrant [3]. During this stage the cranial ectoderm produces the signals which initiate tooth development, until E12.5 the underlying ectomesenchyme has not yet been specified for tooth development [4,5]. Early markers of tooth position and tooth type: Prior to thickening of dental epithelium various factors are expressed in dental epithelium and mesenchyme determining the position and pattern of prospective tooth. Review Article Growth and Transcription Factors in Tooth Development Laura de Sousa-Romero* and Ana María Moreno-Fernández Department of Cytology and Histology, school of Medicine, University of Seville, Spain Dates: Received: 07 April, 2016; Accepted: 18 April, 2016; Published: 29 April, 2016 *Corresponding author: Laura de Sousa Romero, Department of Cytology and Histology, School of Medicine, University of Seville, Avda Sanchez Pizjuán sn, 41009, Spain, Tel. +34954551798; E-mail: