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Sonic hedgehog function in chondrichthyan fins and the evolution of appendage patterning
Randall D Dahn1, Marcus C Davis, William N Pappano
1Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, Illinois 60637, USA.
Nature
|December 26, 2006
Summary
Sonic hedgehog (Shh) gene regulation is deeply conserved in vertebrate paired appendage evolution. Chondrichthyans share Shh expression and function patterns with ray-finned fish and tetrapods, revealing conserved genetic mechanisms.
Area of Science:
- Evolutionary developmental biology
- Comparative genomics
- Vertebrate paleontology
Background:
- Tetrapod limb development genetics are known, but evolutionary assembly and basal vertebrate function remain unclear.
- Chondrichthyans, primitive vertebrates with paired appendages, were thought to have Sonic hedgehog (Shh)-independent appendage skeleton patterning.
- This contrasts with ray-finned fish and tetrapods, suggesting divergent evolutionary paths.
Purpose of the Study:
- To investigate the evolutionary conservation of Sonic hedgehog (Shh) gene function in basal vertebrates.
- To clarify the role of Shh in chondrichthyan appendage development and its evolutionary implications.
- To compare Shh regulation across major vertebrate lineages.
Main Methods:
- Comparative analysis of Shh gene expression patterns in chondrichthyans.
- Identification and characterization of Shh appendage-specific regulatory DNA elements.
- Functional studies assessing Shh's role in appendage patterning.
Main Results:
- Chondrichthyans exhibit conserved patterns of appendage Shh expression.
- Similar Shh appendage-specific regulatory DNA sequences were identified in chondrichthyans, ray-finned fish, and tetrapods.
- Evidence suggests Shh plays a conserved functional role in chondrichthyan appendage patterning.
Conclusions:
- Sonic hedgehog (Shh) function in appendage development is deeply conserved across vertebrate phylogeny.
- The evolution of Shh regulatory mechanisms likely contributed to major morphological changes during appendage evolution.
- Chondrichthyans share fundamental Shh-dependent patterning mechanisms with other jawed vertebrates.
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