Insights from Amphioxus into the Evolution of Vertebrate Cartilage
Meulemans, Daniel and Bronner-Fraser, Marianne (2007) Insights from Amphioxus into the Evolution of Vertebrate Cartilage. PLoS ONE, 2 (8). Art. No. e787. ISSN 1932-6203. PMCID PMC1950077. http://resolver.caltech.edu/CaltechAUTHORS:MEUplosone07
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Central to the story of vertebrate evolution is the origin of the vertebrate head, a problem difficult to approach using paleontology and comparative morphology due to a lack of unambiguous intermediate forms. Embryologically, much of the vertebrate head is derived from two ectodermal tissues, the neural crest and cranial placodes. Recent work in protochordates suggests the first chordates possessed migratory neural tube cells with some features of neural crest cells. However, it is unclear how and when these cells acquired the ability to form cellular cartilage, a cell type unique to vertebrates. It has been variously proposed that the neural crest acquired chondrogenic ability by recruiting proto-chondrogenic gene programs deployed in the neural tube, pharynx, and notochord. To test these hypotheses we examined the expression of 11 amphioxus orthologs of genes involved in neural crest chondrogenesis. Consistent with cellular cartilage as a vertebrate novelty, we find that no single amphioxus tissue co-expresses all or most of these genes. However, most are variously co-expressed in mesodermal derivatives. Our results suggest that neural crest-derived cartilage evolved by serial cooption of genes which functioned primitively in mesoderm.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1950077/ PubMed Central Article
Bronner-Fraser, Marianne 0000-0003-4274-1862
© 2007 Meulemans, Bronner-Fraser. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Received: May 9, 2007; Accepted: August 1, 2007; Published: August 29, 2007. Academic Editor: Jean-Nicolas Volff, Ecole Normale Supérieure de Lyon, France. Phage library was a gift from J. Langeland. Thanks to J.K. Yu for pre-publication access to the amphioxus EST database, J.K. Yu and L.Z. Holland for EST library clones, J. Lawrence for facilities in Tampa, Florida, and the Joint Genome Institute for access to Amphioxus Genome Release v1.0. Author Contributions: Conceived and designed the experiments: DM. Performed the experiments: DM. Analyzed the data: DM. Contributed reagents/materials/analysis tools: DM. Wrote the paper: MB DM. Funding: Funding for this work was provided by NIH grant DE017911 to MBF. Competing interests: The authors have declared that no competing interests exist.
NIH DE017911
CaltechAUTHORS:MEUplosone07
http://resolver.caltech.edu/CaltechAUTHORS:MEUplosone07
http://dx.doi.org/10.1371/journal.pone.0000787
Meulemans D, Bronner-Fraser M (2007) Insights from Amphioxus into the Evolution of Vertebrate Cartilage. PLoS ONE 2(8): e787. doi:10.1371/journal.pone.0000787
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