Tooth Morphogenesis and Patterning: Molecular Genetics

Abigail Saffron Tucker, King's College London, London, UK

Published online: March 2009

DOI: 10.1002/9780470015902.a0005989.pub2

Teeth develop by a series of epithelial–mesenchymal interactions that govern not only where the tooth will form within the developing jaw, but also what type of tooth will develop. Before any sign of tooth development is observed, the patterning information regarding what type of tooth will form has already been determined. Thus an incisor forms in the distal jaw, whereas the molars form more proximally at the back of the jaw. Then, as the tooth develops, a signalling centre, known as the enamel knot, is set up at the centre of the tooth germ, which controls the shape (morphogenesis) of the tooth and the number of cusps which form. The genes involved in these patterning processes are starting to be elucidated and experiments involving knockout mice and misexpression studies have given insights into the molecular genetics of tooth morphogenesis.

Key concepts:

  • How a tooth develops in the embryo?
  • How tooth identity is determined – i.e. to develop as a molar or incisor?
  • How tooth shape is controlled – i.e. number of cusps?

Keywords: tooth; development; shape; identity; enamel knot

Figure 1. Stages of tooth development. Condensing mesenchyme will form part of the dental papilla.
Figure 2. Expression of homeobox genes in the developing mandibular process at E10. Frontal view of the head of an E10 embryo showing the mandibular process (dashed line). The expression domains of four homeobox genes are represented as grey blocks within a schematic of the developing mandible. The spots indicate the sites where tooth germs will initiate. Tooth germs develop within Lhx-expressing mesenchyme. Tooth germs that develop within Barx1 and Dlx domains develop as molars, whereas tooth germs that develop within Msx domains develop as incisors.
Figure 3. Schematic to show signalling involved in setting up the enamel knot and its action within the tooth germ. (a) Induction of the primary enamel knot (EK) at the bud stage by signals from the mesenchyme. (b) and (c) Stimulation of proliferation outside of the EK and apoptosis within the EK lead to changes in the shape of the tooth germ epithelium and eventual loss of the primary EK by the end of the cap stage. (d) Formation of secondary EKs in molar tooth germs act to control cusp morphogenesis.
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 Further Reading
    Chai Y and Maxson RE (2006) Recent advances in craniofacial morphogenesis. Developmental Dynamics 235: 2353–2375.
    Fleischmannova J, Matalova E, Tucker AS and Sharpe PT (2008) Mouse models of tooth abnormalities. European Journal of Oral Science 116: 1–10.
    ePath http://bite-it.helsinki.fi/, Gene Expression in Tooth. Gene expression patterns of a wide variety of signalling molecules, transcription factors etc. involved in tooth development from the epithelial thickening stage to the bell stage of development.
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    Kapadia H, Mues G and D'Souza R (2007) Genes affecting tooth morphogenesis. Orthodontics & Craniofacial Research 10: 105–113.
    Matalova E, Fleischmannova J, Sharpe PT and Tucker AS (2008) Tooth agenesis: from molecular genetics to molecular dentistry. Journal of Dental Research 87: 617–623.
    Tucker AS and Sharpe P (2004) The cutting-edge of mammalian development; how the embryo makes teeth. Nature Reviews. Genetics 5: 499–508.

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Article Title: Tooth Morphogenesis and Patterning: Molecular Genetics
 
How to Cite close
Saffron Tucker, Abigail(Mar 2009) Tooth Morphogenesis and Patterning: Molecular Genetics. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0005989.pub2]