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The Amphioxus SoxB Family: Implications for the Evolution of Vertebrate Placodes

Meulemans, Daniel and Bronner-Fraser, Marianne (2007) The Amphioxus SoxB Family: Implications for the Evolution of Vertebrate Placodes. International Journal of Biosciences, 3 (6). pp. 356-364. ISSN 1449-2288. PMCID PMC1950271.

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Cranial placodes are regions of thickened ectoderm that give rise to sense organs and ganglia in the vertebrate head. Homologous structures are proposed to exist in urochordates, but have not been found in cephalochordates, suggesting the first chordates lacked placodes. SoxB genes are expressed in discrete subsets of vertebrate placodes. To investigate how placodes arose and diversified in the vertebrate lineage we isolated the complete set of SoxB genes from amphioxus and analyzed their expression in embryos and larvae. We find that while amphioxus possesses a single SoxB2 gene, it has three SoxB1 paralogs. Like vertebrate SoxB1 genes, one of these paralogs is expressed in non-neural ectoderm destined to give rise to sensory cells. When considered in the context of other amphioxus placode marker orthologs, amphioxus SoxB1 expression suggests a diversity of sensory cell types utilizing distinct placode-type gene programs was present in the first chordates. Our data supports a model for placode evolution and diversification whereby the full complement of vertebrate placodes evolved by serial recruitment of distinct sensory cell specification programs to anterior pre-placodal ectoderm.

Item Type:Article
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URLURL TypeDescription CentralArticle
Bronner-Fraser, Marianne0000-0003-4274-1862
Additional Information:Copyright ©2008 Ivyspring International Publisher. Received 2007-5-21. Accepted 2007-8-5. Published 2007-8-6. 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. Funding for this work was provided by NIH grant DE017911 to MBF. The authors have declared that no conflict of interest exists.
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Subject Keywords:Evolution, development, chordates, vertebrates, placodes, amphioxus
Issue or Number:6
PubMed Central ID:PMC1950271
Record Number:CaltechAUTHORS:MEUijbs07
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Official Citation:Meulemans D, Bronner-Fraser M. The Amphioxus SoxB Family: Implications for the Evolution of Vertebrate Placodes. Int J Biol Sci 2007; 3:356-364. Available from
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11843
Deposited By: Archive Administrator
Deposited On:06 Oct 2008 21:01
Last Modified:03 Oct 2019 00:23

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