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On the difficulty of increasing dental complexity


One of the fascinating aspects of the history of life is the apparent increase in morphological complexity through time1, a well known example being mammalian cheek tooth evolution2,3,4. In contrast, experimental studies of development more readily show a decrease in complexity, again well exemplified by mammalian teeth, in which tooth crown features called cusps are frequently lost in mutant and transgenic mice5,6,7. Here we report that mouse tooth complexity can be increased substantially by adjusting multiple signalling pathways simultaneously. We cultured teeth in vitro and adjusted ectodysplasin (EDA), activin A and sonic hedgehog (SHH) pathways, all of which are individually required for normal tooth development. We quantified tooth complexity using the number of cusps and a topographic measure of surface complexity8. The results show that whereas activation of EDA and activin A signalling, and inhibition of SHH signalling, individually cause subtle to moderate increases in complexity, cusp number is doubled when all three pathways are adjusted in unison. Furthermore, the increase in cusp number does not result from an increase in tooth size, but from an altered primary patterning phase of development. The combination of a lack of complex mutants5,6,7, the paucity of natural variants with complex phenotypes9, and our results of greatly increased dental complexity using multiple pathways, suggests that an increase may be inherently different from a decrease in phenotypic complexity.

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Figure 1: Cusp number can be increased in cultured teeth.
Figure 2: Number and density of cusps increase with the number of adjusted signalling pathways.
Figure 3: Tomography reveals high surface complexity of treated molars.


  1. Carroll, S. B. Chance and necessity: the evolution of morphological complexity and diversity. Nature 409, 1102–1109 (2001)

    Article  ADS  CAS  PubMed  Google Scholar 

  2. Hunter, J. P. & Jernvall, J. The hypocone as a key innovation in mammalian evolution. Proc. Natl Acad. Sci. USA 92, 10718–10722 (1995)

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  3. Kielan-Jaworowska, Z., Cifelli, R. L. & Luo, Z.-X. Mammals from the Age of Dinosaurs - Origins, Evolution, and Structure (Columbia Univ. Press, 2004)

    Book  Google Scholar 

  4. Luo, Z.-X. Transformation and diversification in early mammal evolution. Nature 450, 1011–1019 (2007)

    Article  ADS  CAS  PubMed  Google Scholar 

  5. Bei, M. Molecular genetics of tooth development. Curr. Opin. Genet. Dev. 19, 504–510 (2009)

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  6. Nieminen, P. Genetic basis of tooth agenesis. J. Exp. Zool. B. 312B, 320–342 (2009)

    Article  CAS  Google Scholar 

  7. Charles, C. et al. Modulation of Fgf3 dosage in mouse and men mirrors evolution of mammalian dentition. Proc. Natl Acad. Sci. USA 106, 22364–22368 (2009)

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  8. Evans, A. R., Wilson, G. P., Fortelius, M. & Jernvall, J. High-level similarity of dentitions in carnivorans and rodents. Nature 445, 78–81 (2007)

    Article  ADS  CAS  PubMed  Google Scholar 

  9. Miles, A. E. W. & Grigson, C. Colyer’s Variations and Diseases of the Teeth of Animals (Cambridge Univ. Press, 2003)

    Google Scholar 

  10. Santana, S. E., Strait, S. & Dumont, E. R. The better to eat you with: functional correlates of tooth structure in bats. Funct. Ecol. 25, 839–847 (2011)

    Article  Google Scholar 

  11. Jernvall, J., Keränen, S. V. E. & Thesleff, I. Evolutionary modification of development in mammalian teeth: quantifying gene expression patterns and topography. Proc. Natl Acad. Sci. USA 97, 14444–14448 (2000)

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  12. Kay, R. F. “Giant” tamarin from the Miocene of Colombia. Am. J. Phys. Anthropol. 95, 333–353 (1994)

    Article  CAS  PubMed  Google Scholar 

  13. Uhen, M. D. Evolution of marine mammals: back to the sea after 300 million years. Anat. Rec. 290, 514–522 (2007)

    Article  Google Scholar 

  14. Gábris, K., Fábián, G., Kaán, M., Rózsa, N. & Tarján, I. Prevalence of hypodontia and hyperdontia in paedodontic and orthodontic patients in Budapest. Community Dent. Health 23, 80–82 (2006)

    PubMed  Google Scholar 

  15. Mikkola, M. L. TNF superfamily in skin appendage development. Cytokine Growth Factor Rev. 19, 219–230 (2008)

    Article  CAS  PubMed  Google Scholar 

  16. Grüneberg, H. Genes and genotypes affecting the teeth of the mouse. J. Embryol. Exp. Morphol. 14, 137–159 (1965)

    PubMed  Google Scholar 

  17. Kangas, A. T., Evans, A. R., Thesleff, I. & Jernvall, J. Nonindependence of mammalian dental characters. Nature 432, 211–214 (2004)

    Article  ADS  CAS  PubMed  Google Scholar 

  18. Ferguson, C. A. et al. Activin is an essential early mesenchymal signal in tooth development that is required for patterning of the murine dentition. Genes Dev. 12, 2636–2649 (1998)

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  19. Kavanagh, K. D., Evans, A. R. & Jernvall, J. Predicting evolutionary patterns of mammalian teeth from development. Nature 449, 427–432 (2007)

    Article  ADS  CAS  PubMed  Google Scholar 

  20. Salazar-Ciudad, I. & Jernvall, J. A computational model of teeth and the developmental origins of morphological variation. Nature 464, 583–586 (2010)

    Article  ADS  CAS  PubMed  Google Scholar 

  21. Cho, S.-W. et al. Interactions between Shh, Sostdc1 and Wnt signaling and a new feedback loop for spatial patterning of the teeth. Development 138, 1807–1816 (2011)

    Article  CAS  PubMed  Google Scholar 

  22. Ahn, Y., Sanderson, B. W., Klein, O. D. & Krumlauf, R. Inhibition of Wnt signalling by Wise (Sostdc1) and negative feedback from Shh controls tooth number and patterning. Development 137, 3221–3231 (2010)

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  23. Dassule, H. R., Lewis, P., Bei, M., Maas, R. & McMahon, A. P. Sonic hedgehog regulates growth and morphogenesis of the tooth. Development 127, 4775–4785 (2000)

    CAS  PubMed  Google Scholar 

  24. Harfe, B. D. et al. Evidence for an expansion-based temporal Shh gradient in specifying vertebrate digit identities. Cell 118, 517–528 (2004)

    Article  CAS  PubMed  Google Scholar 

  25. Taipale, J. et al. Effects of oncogenic mutations in Smoothened and Patched can be reversed by cyclopamine. Nature 406, 1005–1009 (2000)

    Article  ADS  CAS  PubMed  Google Scholar 

  26. Chen, J. K., Taipale, J., Cooper, M. K. & Beachy, P. A. Inhibition of Hedgehog signalling by direct binding of cyclopamine to Smoothened. Genes Dev. 16, 2743–2748 (2002)

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  27. Ishida, K. et al. The regulation of tooth morphogenesis is associated with epithelial cell proliferation and the expression of Sonic hedgehog through epithelial–mesenchymal interactions. Biochem. Biophys. Res. Commun. 405, 455–461 (2011)

    Article  CAS  PubMed  Google Scholar 

  28. Cai, J. et al. Patterning the size and number of tooth and its cusps. Dev. Biol. 304, 499–507 (2007)

    Article  CAS  PubMed  Google Scholar 

  29. Metscher, B. D. MicroCT for developmental biology: a versatile tool for high-contrast 3D imaging at histological resolutions. Dev. Dyn. 238, 632–640 (2009)

    Article  PubMed  Google Scholar 

  30. Skinner, M. M. et al. Brief communication: contributions of enamel-dentine junction shape and enamel deposition to primate molar crown complexity. Am. J. Phys. Anthropol. 142, 157–163 (2010)

    PubMed  Google Scholar 

  31. Närhi, K. & Thesleff, I. Explant culture of embryonic craniofacial tissues: analyzing effects of signaling molecules on gene expression. Methods Mol. Biol. 666, 253–267 (2010)

    Article  PubMed  Google Scholar 

  32. Gaide, O. & Schneider, P. Permanent correction of an inherited ectodermal dysplasia with recombinant EDA. Nature Med. 9, 614–618 (2003)

    Article  CAS  PubMed  Google Scholar 

  33. Harrington, A. E. et al. Structural basis for the inhibition of activin signalling by follistatin. EMBO J. 25, 1035–1045 (2006)

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  34. Pispa, J. et al. Tooth patterning and enamel formation can be manipulated by misexpression of TNF receptor Edar. Dev. Dyn. 231, 432–440 (2004)

    Article  CAS  PubMed  Google Scholar 

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We thank I. Thesleff, P. Munne, A. R. Evans, I. Corfe, J. Moustakas, M. Murtoniemi, I. Salazar-Ciudad, S. Sova, J.-P. Suuronen and S. Zohdy for discussions or help; R. Santalahti, R. Savolainen and M. Mäkinen for technical assistance; M. Hyvönen for the activin A protein; P. Schneider for the Fc-EDA-A1-protein; and C. Tabin and A. Gritli-Linde for the ShhGFP mice. This study was funded by the Academy of Finland, the Sigrid Juselius Foundation, the Finnish Cultural Foundation, and the graduate school GSBM.

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Authors and Affiliations



E.H. and J.J. designed the study. E.H. performed developmental experiments and measurements. M.L.M. and M.V. designed and performed Eda;Edar transgenic mouse experiments. K.H. and A.K. designed and performed microtomography imaging. E.H. and J.J. analysed the data and wrote the manuscript with contributions from the other authors. J.J. coordinated the study.

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Correspondence to Jukka Jernvall.

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The authors declare no competing financial interests.

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Harjunmaa, E., Kallonen, A., Voutilainen, M. et al. On the difficulty of increasing dental complexity. Nature 483, 324–327 (2012).

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