Medline ® Abstracts for References 1,2
of 'Anatomy and development of the teeth'
Tissue Interactions Regulating Tooth Development and Renewal.
Balic A, Thesleff I
Curr Top Dev Biol. 2015;115:157. Epub 2015 Oct 6.
Reciprocal interactions between epithelial and mesenchymal tissues play a fundamental role in the morphogenesis of teeth and regulate all aspects of tooth development. Extensive studies on mouse tooth development over the past 25 years have uncovered the molecular details of the signaling networks mediating these interactions (reviewed by Jussila&Thesleff, 2012; Lan, Jia,&Jiang, 2014). Five conserved signaling pathways, namely, the Wnt, BMP, FGF, Shh, and Eda, are involved in the mediation of the successive reciprocal epithelial-mesenchymal cross talk which follows the general principle of morphogenetic interactions (Davidson, 1993). The pathways regulate the expression of transcription factors which confer the identity of dental epithelium and mesenchyme. The signals and transcription factors are integrated in complex signaling networks whose fine-tuning allows the generation of the variation in tooth morphologies. In this review, we describe the principles and molecular mechanisms of the epithelial-mesenchymal interactions regulating successive stages of tooth formation: (i) the initiation of tooth development, with special reference to the shift of tooth-forming potential from epithelium to mesenchyme; (ii) the morphogenesis of the tooth crown, focusing on the roles of epithelial signaling centers; (iii) the differentiation of odontoblasts and ameloblasts, which produce dentin and enamel, respectively; and (iv) the maintenance of dental stem cells, which support the continuous growth of teeth.
Research Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
Towards unraveling the human tooth transcriptome: the dentome.
Hu S, Parker J, Wright JT
PLoS One. 2015;10(4):e0124801. Epub 2015 Apr 7.
The goal of the study was to characterize the transcriptome profiles of human ameloblasts and odontoblasts, evaluate molecular pathways and advance our knowledge of the human "dentome". Laser capture microdissection was used to isolate odontoblasts and ameloblasts from human tooth buds (15-20week gestational age) from 4 fetuses. RNA was examined using Agilent 41k whole genome arrays at 2 different stages of enamel formation, presecretory and secretory. Probe detection was considered against the array negative control to control for background noise. Differential expression was examined using Significance Analysis of Microarrays (SAM) 4.0 between different cell types and developmental stages with a false discovery rate of 20%. Pathway analysis was conducted using Ingenuity Pathway Analysis software. We found that during primary tooth formation, odontoblasts expressed 14,802 genes, presecretory ameloblasts 15,179 genes and secretory ameloblasts 14,526 genes. Genes known to be active during tooth development for each cell type (eg COL1A1, AMELX) were shown to be expressed by our approach. Exploring further into the list of differentially expressed genes between the motile odontoblasts and non-motile presecretory ameloblasts we found several genes of interest that could be involved in cell movement (FN1, LUM, ASTN1). Furthermore, our analysis indicated that the Phospholipase C and ERK5 pathways, that are important for cell movement, were activated in the motile odontoblasts. In addition our pathway analysis identified WNT3A and TGFB1 as important upstream contributors. Recent studies implicate these genes in the development of Schimke immuno-osseous dysplasia. The utility of laser capture microdissection can be a valuable tool in the examination of specific tissues or cell populations present in human tooth buds. Advancing our knowledge of the human dentome and related molecular pathways provides new insights into the complex mechanisms regulating odontogenesis and biomineralization. This knowledge could prove useful in future studies of odontogenic related pathologies.
Pediatric Dentistry, University of North Carolina, Chapel Hill, North Carolina, United States of America; Oral Biology Curriculum, University of North Carolina, Chapel Hill, North Carolina, United States of America.