The appearance of jaws was a turning point in vertebrate evolution because it allowed primitive vertebrates to capture and process large, motile prey. The vertebrate jaw consists of separate dorsal and ventral skeletal elements connected by a joint. How this structure evolved from the unjointed gill bar of a jawless ancestor is an unresolved question in vertebrate evolution. To understand the developmental bases of this evolutionary transition, we examined the expression of 12 genes involved in vertebrate pharyngeal patterning in the modern jawless fish lamprey. We find nested expression of Dlx genes, as well as combinatorial expression of Msx, Hand and Gsc genes along the dorso-ventral (DV) axis of the lamprey pharynx, indicating gnathostome-type pharyngeal patterning evolved before the appearance of the jaw. In addition, we find that Bapx and Gdf5/6/7, key regulators of joint formation in gnathostomes, are not expressed in the lamprey first arch, whereas Barx, which is absent from the intermediate first arch in gnathostomes, marks this domain in lamprey. Taken together, these data support a new scenario for jaw evolution in which incorporation of Bapx and Gdf5/6/7 into a preexisting DV patterning program drove the evolution of the jaw by altering the identity of intermediate first-arch chondrocytes. We present this "Pre-pattern/Cooption" model as an alternative to current models linking the evolution of the jaw to the de novo appearance of sophisticated pharyngeal DV patterning.
- MeSH
- biologická evoluce MeSH
- biologické modely MeSH
- čelisti anatomie a histologie MeSH
- homeodoménové proteiny genetika metabolismus MeSH
- mihule anatomie a histologie genetika MeSH
- molekulární sekvence - údaje MeSH
- obratlovci anatomie a histologie genetika MeSH
- rozvržení tělního plánu MeSH
- transkripční faktory bHLH genetika metabolismus MeSH
- transkripční faktory genetika metabolismus MeSH
- vývojová regulace genové exprese MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
- MeSH
- experimenty na zvířatech MeSH
- glykosaminoglykany * metabolismus MeSH
- krysa rodu rattus fyziologie metabolismus MeSH
- kyselina hyaluronová izolace a purifikace metabolismus MeSH
- ledvinové kanálky * cytologie metabolismus účinky léků MeSH
- mihule fyziologie metabolismus MeSH
- obojživelníci fyziologie metabolismus MeSH
- ptáci fyziologie metabolismus MeSH
- ryby fyziologie metabolismus MeSH
- vasopresiny fyziologie metabolismus účinky léků MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus fyziologie metabolismus MeSH
- zvířata MeSH
