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Insight from Frogs: Sonic Hedgehog Gene Expression and a Re-evaluation of the Vertebrate Odontogenic Band
Theresa M Grieco1, Leslea J Hlusko2
1Department of Oral Health Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada.
Anatomical Record (Hoboken, N.J. : 2007)
|June 5, 2016
Summary
Sonic hedgehog (Shh) gene expression is thought to initiate tooth development. However, new research on frog development suggests Shh may be linked to mouth formation, not tooth initiation.
Area of Science:
- Developmental biology
- Evolutionary developmental biology
- Comparative genomics
Background:
- Conserved developmental processes reveal fundamental biological mechanisms.
- Evolutionary modifications of development generate anatomical diversity.
- Odontogenesis (tooth development) offers insights into both conserved and diverse developmental pathways.
Purpose of the Study:
- To investigate the role of Sonic hedgehog (Shh) in early tooth development.
- To examine departures from conserved developmental mechanisms in odontogenesis.
- To test the hypothesis that Shh is immediately required for tooth development.
Main Methods:
- Analysis of existing tooth development studies across diverse taxa.
- Examination of Shh gene expression patterns.
- New gene expression data collection for the frog Silurana (Xenopus) tropicalis.
Main Results:
- Several vertebrate species deviate from the Shh Consensus Model of tooth initiation.
- Shh expression patterns in Silurana (Xenopus) tropicalis suggest a role in mouth formation.
- Craniofacial and odontogenic development are more separated in this amphibian model.
Conclusions:
- The assumed causality of epithelial Shh in tooth initiation requires reconsideration.
- Shh's role in tooth development may be context-dependent or related to broader oral structures.
- Comparative studies highlight evolutionary divergence in developmental pathways.
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